vvEPA
United States
Environmental Protection
Agency
Atmospheric Research and
Exposure Assessment Laboratory
Research Triangle Park, NC 27711
EPA/600/8-90/005
February 1990
Research and Development
Assistance
Document for
Sampling and
Analysis of Toxic
Organic Compounds in
Ambient Air
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EPA/600/8-90/005
February 1990
TECHNICAL ASSISTANCE DOCUMENT FOR
SAMPLING AND ANALYSIS OF TOXIC ORGANIC
COMPOUNDS IN AMBIENT AIR
by
ATC, Inc.
1635 Pumphrey Ave.
Auburn, Alabama 36830
Contract No. 68-02-4556
EPA Project Officer:
Howard Crist
Atmospheric Research and Exposure Assessment Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
ATMOSPHERIC RESEARCH AND EXPOSURE ASSESSMENT LABORATORY
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
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world
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorsement
or recommendation for use.
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ABSTRACT
This Technical Assistance Document (TAD) was initially published in June
1983 and has been updated to reflect the advances that have been made in
sampling and analysis of toxic organic compounds in ambient air. The
primary users of this document are expected to be regional, state, and local
environmental protection personnel who are faced with the need to determine
ambient air quality for regulatory or information-gathering purposes.
The TAD consists of the following seven chapters:
1. Introduction
2. Regulatory Issues Concerning Toxic Organic Monitoring
3. Guidelines for Development of a Monitoring Plan
4. Overview of Sampling Methods
5. Overview of Analytical Methods
6. Methods for Specific Compounds and Compound Classes
7. Quality Assurance
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PREFACE
The determination of toxic organic chemicals in ambient air is an area
of concern for many environmental protection personnel. There exist intense
regulatory pressures to gather data concerning human exposure to such
chemicals. During the last five years, sampling and analysis methods for
toxic organic air pollutants have become increasingly standardized, and
standard reference materials for the compounds have become available. This
technical assistance document (TAD) has been revised for the purpose of
providing such personnel with a basis for developing specific monitoring
plans for toxic organic chemicals, in light of the advances that have been
made in these areas; however, this document does not circumvent the need to
have highly skilled technical personnel organizing such monitoring efforts,
and the TAD should not be used as a rigid, step-by-step guide for developing
monitoring plans.
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TABLE OF CONTENTS
Page
NOTICE ii
ABSTRACT iii
PREFACE iv
LIST OF TABLES viii
LIST OF APPENDICES viii
SECTION 1 INTRODUCTION 1
SECTION 2 REGULATORY AND RELATED ISSUES CONCERNING TOXIC ORGANIC
MATERIALS 3
2 .1 GENERAL 3
2 .2 RISK ASSESSMENT 3
2 .3 REGULATORY NEEDS 4
2.3.1 Resource Conservation and Recovery Act 4
2.3.2 Community Right-to-Know Act 4
2.3.3 Toxic Substances Control Act 4
2.3.4 Clean Air Act 5
2.3.4.1 Technology-Based Standards 5
2.3.4.2 Health-Based Standards 5
2.4 EMERGENCY SITUATIONS AND NUISANCE COMPLIANTS 6
2 .5 AIR POLLUTION RESEARCH ACTIVITIES 6
SECTION 3 GUIDELINES FOR DEVELOPMENT OF A MONITORING PLAN 7
3.1 GENERAL 7
3.2 DATA QUALITY OBJECTIVES 7
3.2.1 Stage I Activities 8
3.2.2 Stage II Activities 8
3.2.3 Stage III Activities 8
3 .3 TECHNICAL CONSIDERATIONS 8
3.3.1 Site Selection 8
3.3.2 Analyte Selection 10
3.3.3 Physical State of the Analyte 10
3.3.4 Sampling and Analytical Protocol Selection . 11
3 . 4 LOGISTICAL CONSIDERATIONS 13
3.5 DATA QUALITY FACTORS 14
3.6 COST FACTORS 14
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TABL1 OF CONTKHTS
(Continued)
Page
3.7 COMPILATION AND EVALUATION OF AVAILABLE INFORMATION 14
3.7.1 Assessment of Available Air Quality Data
Base 14
3.7.1.1 National Air Toxics Information
Clearinghouse (NATICH) Data Base... 16
3.7.1.2 Air Toxics Monitoring Data Base.... 16
3.7.2 Assessment of Toxic Organic Air Pollutant
Sources 17
3.7.3 Assessment of Meteorological Data 18
3.7.4 Assessment of Relevant Sampling and
Analytical Methodologies 19
3.8 SELECTION OF SAMPLING AND ANALYSIS METHODS 20
3.8.1 Analytical Methodology Considerations 21
3.8.2 Sampling Methodology Considerations 23
3.8.3 Selection of Sampling Strategy 24
3 . 9 QUALITY ASSURANCE PLANNING 26
3.10 DEFINITION OF DATA REPORTING FORMAT 27
3.11 SAFETY CONSIDERATIONS 27
3.12 MANPOWER REQUIREMENTS 29
SECTION 4 OVERVIEW OF SAMPLING METHODS 30
4.1 PHYSICAL AND CHEMICAL PROPERTIES 30
4.1.1 Volatile Organic Compounds 30
4.1.2 Semi-volatile Organic Compounds 31
4.1.3 Nonvolatile Organic Compounds 32
4.2 METHODS FOR GAS PHASE COMPONENTS 32
4.2.1 Solid Adsorbents 32
.2.1.1 Organic Polymeric Adsorbents 32
.2.1.2 Inorganic Adsorbents 34
.2.1.3 Carbon Adsorbents 34
4.2.2 Whole Air Collection 36
.2.2.1 Glass Sampling Bulbs 37
.2.2.2 Gas Sampling Bags 37
.2.2.3 SummaR Polished Canisters 37
.2.3 Cryogenic Trapping 38
.2.4 Impinger Collection 40
.2.5 Derivatization Techniques 40
.2.6 Passive Samplers 41
.2.7 Direct Analysis 41
4.3 METHODS FOR PARTICULATE AND PARTICLE BOUND
COMPONENTS 41
4.3.1 Filtration 42
4.3.2 Centrifugal Collection and Impaction 43
4.3.3 Electrostatic Precipitation 44
4.4 GAS AND SOLID PHASE DISTRIBUTION ANALYSIS 44
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TABLE Or CONTENTS
(Continued)
Page
SECTION 5 OVERVIEW OF ANALYTICAL METHODS 46
5.1 CHEMICAL AND PHYSICAL PROPERTIES 46
5.2 FIELD SCREENING TECHNIQUES 47
5.2.1 Colorimetric Detection 48
5.2.2 Spectroscopic Devices 50
5.2.3 lonization Devices 50
5.2.4 Photometric Devices 53
5.2.5 Summary 53
5.3 LABORATORY SCREENING TECHNIQUES 54
5.3.1 Colorimetric Techniques 54
5.3.2 Infrared Spectroscopy (IR) 55
5.3.3 Fluorescence Spectroscopy 55
5.3.4 Low Resolution Mass Spectrometry (LRMS) .... 55
5.4 COMPOUND SPECIFIC TECHNIQUES 56
5.4.1 Gas Chromatrography (GC) 56
5.4.1.1 Column Types 57
5.4.1.2 Detector Types 58
5.4.1.3 Injection Systems 61
5.4.2 Gas Chromatography-Mass Spectrometry (GC-MS) 63
5.4.2.1 Instrumentation 64
5.4.2.2 Applications 65
5.4.3 High Performance Liquid Chromatography
(HPLC) 66
5.4.4 Thin Layer and Column Chromatrography 67
5.4.5 Spectroscopic Techniques 67
SECTION 6 SPECIFIC SAMPLING AND ANALYTICAL METHODS 69
SECTION 7 QUALITY ASSURANCE PROCEDURES 75
7.1 QUALITY ASSURANCE EXPECTATIONS 75
7.2 QUALITY ASSURANCE AND QUALITY CONTROL 75
7.3 QUALITY ASSURANCE MANAGEMENT 75
7.3.1 Quality Assurance System Design 76
7.3.2 Document Control 76
7.3.3 Data Evaluation and Storage 77
7.3.4 Standard Reference Materials 77
7.3.5 Quality Audits 78
7.3.5.1 Performance Audits 78
7.3.5.2 System Audits 78
7.3.6 Quality Assurance Reports 78
7.3.7 Corrective Action 78
7.3.8 Training 79
7.4 Sampling Quality Assurance 79
7.4.1 Site Selection 79
7.4.2 Instrument Calibration and Maintenanc 79
7.4.3 Routine Quality Control Sample Collection .... 80
7.4.4 Sample Labeling, Preservation, Storage, and
Transport 80
7.4.5 Chain of Custody Procedures 80
VII
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TABLE Or CONTENTS
(Continued)
Page
7.5 ANALYTICAL QUALITY ASSURANCE 80
7.5.1 Method Validation 81
7.5.2 Instrument Calibration and Maintenance 81
7.5.3 Quality Control Sample Analysis 82
7 . 6 DATA MANAGEMENT 82
7.7 REPORTING QUALITY ASSURANCE 83
LIST Or TABLES
3.1 COMPONENTS OF THE DATA QUALITY OBJECTIVE PROCESS 9
3.2 QUALITY ASSURANCE (QA) ACTIVITIES TO BE SPECIFIED IN PROGRAM
PLAN 28
5 .1 COMMONLY USED GC DETECTORS 59
5 .2 USEFUL DUAL GC DETECTOR COMBINATIONS 62
5 . 3 HPLC DETECTORS 70
6.1 METHODS FOR THE ANALYSIS OF TOXIC ORGANIC AIR POLLUTANTS IN
AMBIENT AIR 70
6.2 SAMPLING AND ANALYTICAL METHODOLOGIES FOR SELECTED TOXIC
ORGANIC AIR POLLUTANTS 72
LIST Or APPENDICES
APPENDIX A COMPOUNDS SUBJECT TO REGULATION UNDER THE PROPOSED CLEAN
AIR ATTAINMENT ACT OF 1987
APPENDIX B REFERENCE METHODS FOR TOXIC ORGANIC AIR POLLUTANTS
APPENDIX C GLOSSARY
APPENDIX D EQUIPMENT/INSTRUMENT VENDORS
APPENDIX E CALIBRATION GAS STANDARDS
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SECTION 1
INTRODUCTION
The Technical Assistance Document for Sampling and Analysis of Toxic
Organic Compounds in Ambient Air was initially published in June of 1983
and was intended as a guide to those persons responsible for designing and
implementing ambient air monitoring programs for toxic organic compounds.
Since that date, there have been significant advances in methodology for
analyzing toxic organic air pollutants (TOAP's), significant improvements
in the quality and availability of calibration standards for TOAP's, and
significant changes in TOAP regulations. The combined impact of these
factors limited the vitality of the TAD and necessitated revision of the
original document to reflect advances in the field.
This Technical Assistance Document (TAD) is intended for use by
regional, state, and local environmental regulatory personnel. It may
also be useful to the regulated community in terms of the development of
TOAP monitoring programs. The TAD is not intended to serve as a single
source of information from which all necessary technical input concerning
TOAP monitoring can be obtained. Instead, it is a guidance document which
can be used as a basis for the development of TOAP monitoring programs.
The revised TAD ia presented in seven major sections, including this
introductory section. Section 2 provides fundamental information
concerning risk assessment and addresses the regulatory issues which
result in a need for TOAP monitoring programs.
Section 3 focuses on the factors which impact the development of a
TOAP monitoring program. The emphasis of this section is adequate TOAP
monitoring program planning to achieve established objectives. Topics
addressed include program design based on data quality objectives,
evaluation of available information, selection of sampling and analytical
protocols, specification of quality assurance protocols, data reporting,
safety considerations, and manpower requirements. The information is
presented in a manner which implies step-wise progression through the
planning process; however, actual TOAP monitoring program planning is an
iterative process wherein conflicts between program objectives and
limitations of the various planning elements are reconciled.
Section 4 provides an overview of sampling methods for TOAP's.
Sampling methodologies are reviewed on the basis of chemical and physical
properties. Most of this section is dedicated to procedures for volatile
and nonvolatile TOAP's. Advances in sampling protocols for phase
distribution analysis of semi-volatile TOAP's are also reviewed in this
section.
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Section 5 provides an overview of the various analytical protocols for
TOAP's. Field screening and laboratory screening techniques are discussed
in general terms. This section concludes with a discussion of compound
specific analytical techniques.
Section 6 serves to integrate the basic information contained in
Sections 4 and 5 and addresses sampling and analytical approaches for
specific organic compounds. The highlight of Section 6 is a table
summarizing sampling and analytical protocols suitable for several of the
organic compounds subject to regulation under Section 112 of the Clean Air
Act.
Section 7 provides information concerning the various components of an
effective quality assurance program for a TOAP monitoring program. The
emphasis of this section is on system design, document control, data
storage, quality audits, reports, training, equipment calibration,
equipment maintenance, calibration, reference materials, and method
validation.
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SECTION 2
REGULATORY AND RELATED ISSUES CONCERNING TOXIC ORGANIC MATERIALS
2.1. GENERAL
The primary motivations for conducting ambient air monitoring of
TOAP's are: (a) regulatory compliance requirements, (b) emergency
situations (chemical spills, inadvertent releases, and fires) and nuisance
complaints, and (c) air pollution research activities. Each of these
topical areas has distinct requirements for ambient air monitoring which
are important to recognize. While each area may have distinct
requirements, the impetus for TOAP monitoring programs is the risk to
human health associated with exposure to TOAP's.
2.2. RISK ASSESSMENT
Toxic Organic Air Pollutants are the focus of regulatory concern
because of the adverse health effects associated with their uncontrolled
presence in the environment. The establishment of ambient air quality
standards for TOAP's is difficult because of the variety of compounds of
concern, the economics of TOAP control, and the inherent problems
associated with documenting the rationale for ambient TOAP standards.
While the variety of compounds and the economic costs of TOAP control can
eventually be reduced to comprehensible terms, the rationale for
establishing a given TOAP standard is substantially more abstract.
The establishment of ambient standards for TOAP's involves the
assessment of risks associated with exposure to TOAP's. The risk
assessment process can be viewed as a mechanism to examine risks
associated with exposure to air toxics so that they may be avoided,
reduced, or otherwise managed. By definition, the concept of "risk"
implies uncertainty. Therefore, risk assessment is largely concerned with
probability: a difficult concept to grasp. Judgement is another essential
part of the risk assessment process. If all judgement could be removed
from the process, the risk estimates for ambient standards would be far
more consistent.
Thus, the risk assessment process begins with a. debatable foundation
in both probability and judgement. The risk assessment process is further
complicated by the fact that all of the data required to assess health
risks associated with exposure to air toxics are simply not available.
For example, (i) toxicity testing has not kept pace with the need for
information on numerous chemicals and (ii) the environmental fate and the
atmospheric chemistry of air toxics are not well defined.
Although risk assessment is, in theory, to be separate from any risk
management decision, the application of professional judgement throughout
the risk assessment process necessitates a sensitivity on the part of the
risk assessor to risk management issues, such as the establishment of
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an acceptable level of risk for TOAP's. The level of risk is only one
among several variables that determine risk acceptability. Deciding what
level of risk ought to be acceptable is not a technical question but a
value judgement. Therefore, the risk assessor must use skill, recognizing
the broader ramifications when assumptions are made in the risk assessment
process. The validity and usefulness of any risk assessment is tied
directly to the professional abilities of the risk assessor and to the
documentation of all assumptions and value judgements inherent within the
risk assessment.
TOAP risk assessment focuses on cancer incidences in terms of
individual risk and estimated annual incidence. Lifetime risk is an
estimate of the probability of an individual contracting cancer as a
result of exposure to an ambient concentration of a TOAP over a 70-year
period. The annual incidence is determined by applying individual risk
data, based on various exposure levels, to the entire population and then
dividing by 70.
2.3. REOTIATORY NEEDS
The regulatory needs for ambient air monitoring are diverse and
constantly being modified. At the federal level, the statutory basis for
ambient air monitoring is found in the Resource Conservation and Recovery
Act and subsequent amendments, the Community Right-To-Know Act, the Toxic
Substances Control Act, and the Clean Air Act. The focus and requirements
of each act are different and are discussed separately in the subsections
that follow:
2.3.1. R«source Conservation mnd Recovery Act
The Resource Conservation and Recovery Act (RCRA) was signed on
October 21, 1976 and amended in 1980 and 1984. RCRA deals primarily with
current and future waste handling activities. Two types of TOAP
monitoring programs can be required for treatment, storage, and disposal
(TSD) facilities under RCRA: First, TSD facilities may be required to
establish TOAP monitoring programs as part of routine operations to
safeguard community residents. Secondly, a TOAP monitoring program plan
may typically be required as part of the emergency response plan for the
facility.
2.3.2. Community Right-To-Know Act
The Community Right-To-Know Act of 1986 is an integral part of the
Superfund Amendments and Reauthorization Act (SARA). The Community
Right-To-Know Act requires emergency planning, emergency notification,
community right-to-know reporting, and an emissions inventory for each
affected facility. An integral component of the emergency planning
requirement will be a monitoring program for TOAP's
2.3.3. Toxic Substances Control Act
The Toxic Substances Control Act (TSCA) regulates existing and new
chemical substances and applies primarily to chemical manufacturers,
distributors, processors, and importers. It is conceivable that TOAP
monitoring programs may be required by either Section 6 or Section 8 of
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TSCA. Under Section 6, EPA regulatory action can range from labelling
requirements to a complete prohibition of the product if there is reason
to believe that an unreasonable risk to human health or the environment is
associated with the manufacture, processing, distribution, use, or
disposal of a chemical substance or mixture. Section 8 addresses general
reporting requirements, and under Section 8D EPA is authorized to require
that manufacturers, processors, or distributors of certain listed
chemicals submit health and safety data. Health and safety data may
include ambient air monitoring data.
2.3.4. Clean Air Act
The Clean Air Act (CAA) requires EPA to establish national ambient air
standards and national air emission standards. States are required to
achieve these standards through State Implementation Plans (SIP's).
EPA designates harmful pollutants and publishes criteria documents
which discuss potentially harmful effects of those pollutants. EPA then
sets primary and secondary ambient air standards. Primary standards are
intended to protect human health, and secondary standards are intended to
protect the aesthetic values of the environment.
Senate Bill 1894 was introduced in November 1987 as the Clean Air
Standards Attainment Act of 1987, as a proposed amendment to the Clean Air
Act. This legislation addresses several major air pollution issues,
including non-attainment areas for primary ambient air standards,
interstate transport of pollutants, acid disposition, and hazardous air
pollutants. With regard to hazardous air pollutants, EPA will be required
to promulgate both technology-based and health-based emission standards.
2.3.4.1. Tachnology-Basad Standards
Under Senate Bill 1894, EPA will be required to promulgate emission
standards for approximately 225 compounds, of which approximately 200 are
organic compounds. The entire list of compounds subject to this proposed
legislation (1) is provided in Appendix A. Under the proposed amendment,
EPA will also be required to establish test measures and analytical
procedures for monitoring and measuring emissions and ambient
concentrations of the air pollutants identified in Appendix A.
Technologically based standards will require the maximum degree of
reduction in emission, based on an evaluation of costs, non-air-quality
health and environmental impacts, and energy requirements. Typically,
such standards will be achieved through process changes, material
substitutions, process enclosures, or control equipment designed to
collect, capture, or treat pollutants.
2.3.4.2. Haalth-Basad Standards
Under the proposed amendments to the Clean Air Act, EPA is authorized
to establish standards for hazardous air pollutants, on the basis of
possible health impairments or adverse environmental effects. Health
impairments are broadly defined as an increased mortality or irreversible
or incapacitating illnesses. Chemical substances which can produce health
impairments include carcinogens, mutagens, teratogens, neurotoxins, and
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acute and chronic toxins. With regard to adverse environmental effects,
standards can be developed for compounds which exhibit adverse effects at
ambient concentrations or through bioaccumulation or deposition
mechanisms.
2.4. EMERGENCY SITUATIONS AND NUISANCE COMPLAINTS
Emergency response activities are primarily related to chemical spills
and fires at chemical handling facilities. In such situations there
exists an immediate need to conduct ambient air monitoring in the vicinity
of the activity, as well as in remote areas where transport of hazardous
compounds is possible. Emergency monitoring situations differ from most
regulatory-related activities in several important ways: Since acute
rather than chronic effects are of concern, the required detection
sensitivity is less stringent. However, in many cases the exact compounds
of interest may not be immediately known, and hence a broad range of
monitoring techniques must be used to ensure detection of the toxic
compounds. In addition, the regulatory-related monitoring activities are
generally not time critical, and development of a monitoring strategy can
be accomplished over a several-day or a several-week period, whereas
emergency situations obviously require immediate response without
development of a detailed monitoring strategy.
Nuisance complaints arising from the general public are primarily
related to noxious odors, eye irritation, or in some cases, more serious
illness. Monitoring activities in this regard are similar to emergency
response activities in that the chemicals of interest are often not known.
However, the compounds of interest may be present at significantly lower
concentrations in this situation, due to the highly sensitive nature of
the human senses.
2.5. AIR POLLUTION RESEARCH ACTIVITIES
Air pollution research activities require a wide variety of monitoring
strategies. In general, such research activities are concerned with one
of the following topics:
• Identification of toxic organics.
• Validation and refinement of sampling and analysis techniques
for toxic organics.
• Development and validation of air pollution models.
• Fate and transport studies of specific organic compounds.
• Correlation of human health effects data with ambient air
monitoring data.
In general, such research activities are characterized by (a) a great deal
of time and effort in development of a monitoring plan and (b) the need to
detect trace levels of organic compounds, if present. While many research
activities are directed towards the development and support of proposed
regulations, they are distinguished from regulatory monitoring activities
by having a more general scope and greater flexibility.
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SECTION 3.
GUIDELINES FOR DEVELOPMENT OF A MONITORING PLAN
3.1. GENERAL
The development of an appropriate monitoring plan is critical to the
success of any air monitoring project. This is particularly true in the
case of TOAP monitoring projects because of the low concentrations of
sampled compounds and the complexity of sampling and analytical protocols.
3.2. DATA QUALITY OBJECTIVES
The first step in any planning process is the identification of
objectives. EPA has embraced the process of establishing Data Quality
Objectives (DQO's) as a mechanism for ensuring that the quality of
environmental data collected under a given program is consistent with the
intended use of that data. The DQO process is a three-stage process that
places emphasis on defining the regulatory objectives of the environmental
monitoring program/ the decision that will be made regarding the data
collected, and the possible consequences of the decision being incorrect.
Experimental design based on DQO's rather than on collection of the "best
possible data" is intended to ensure that the information needed to make a
decision is obtained, rather then ensuring that each individual
measurement obtained is the best possible.
Data quality objectives are statements of the level of uncertainty
that a decision maker is willing to accept from results derived from
environmental data, when the results are going to be used in a regulatory
or programmatic decision such as establishing the need for a new
regulation, setting or revising a standard, or determining compliance with
an existing standard. Complete data quality objectives must be
accompanied by clear statements of:
• The decision to be made.
• Why environmental data are needed.
• How the environmental data will be used.
• Time and resource constraints on data collection.
• Descriptions of the environmental data to be collected.
• Specifications regarding the domain of the decision.
• The calculations, statistical and otherwise, that will be
performed on the data in order to arrive at the result.
The DQO process is interactive, consisting of three multi-step
stages. The first two stages result in proposed DQO's with accompanying
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specifications and constraints for designing the data collection system.
In the third stage, potential designs for the data collection program are
evaluated. The various stages and steps associated with the DQO process
are summarized in Table 3.1
3.2.1 Stage I Activities
This stage is the responsibility of the decision maker: He/she states
an initial perception of what decision must be made, what information is
needed, why and when it is needed, how it will be used, and what the
consequences will be if information of adequate quality is not available.
Initial estimates of the time and resources that can reasonably be made
available for the data collection activity are presented.
3.2.2 Stag* IX Activities
This stage is primarily the responsibility of the senior program
staff, using guidance and oversight from the decision maker and input from
technical staff. The information from Stage I is carefully examined and
discussed with the decision maker to ensure that senior program staff
understand as many of the nuances of the program as possible. After this
interactive process, senior program staff discuss each aspect of the
initial problem, exercising their prerogative to reconsider key elements
from a. technical or policy standpoint. The outcome of their work, once
explained to and concurred upon by the decision maker, leads to the
generation of specific guidance for designing the data collection
program. The products of Stage II include proposed statements of the type
and quality of environmental data required to support the decision, along
with other technical constraints on the data collection activity, that
will place bounds on the search for an acceptable design in Stage III.
These outputs are the proposed DQO's.
3.2.3 Stage III Activities
This stage is primarily the responsibility of the technical staff but
involves both the senior program staff and the decision maker to assure
the outputs from Stages I and II are understood. The objective of Stage
III is to develop data collection plans that will meet the criteria and
constraints established in Stages I and II. All viable options should be
presented to the decision maker. It is the prerogative of the decision
maker to select the final design that provides the best balance between
time and resources available for data collection and the level of
uncertainty expected in the final results.
3.3. TECHNICAL CONSIDERATIONS
There are four primary factors which shape ambient TOAP monitoring
program objectives from a technical standpoint: sampling site and time
frame selection, analyte selection, physical state of the analyte, and
sampling and analytical protocol selection.
3.3.1. Site Selection
Selection of the appropriate sampling site(s) is an important factor
in terms of developing program objectives. In some instances, such as
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TABLE 3.1
COMPONENTS OF THE DATA QUALITY OBJECTIVE PROCESS
Stage I Decision Definition
Responsibility: Decision Maker
Step 1. Decision Description
Step 2. Description of Information Needed for Decision
Step 3. Definition of Environmental Data Use
Step 4. Definition of Consequences of an Incorrect Decision
Attributable to Inadequate Environmental Data
Step 5. Description of Available Resources
Stage II Clarification of the Information Needed for the Decision
Responsibility: Senior Program Staff
Step 1. Fragmentation of Decision into Decision Elements
Step 2. Specification of Required Environmental Data
Step 3. Definition of Decision Domain
Step 4. Definition of Result to be Derived From Environmental
Data
Step 5. Definition of Desired Performance
Step 6. Evaluation of the Need for New Environmental Data
Step 7. Establish the DQO's
Stage III Design of the Data Collection System
Responsibility: Technical Staff
Step 1. Development of Viable Data Collection Plans That Meet
the Criteria and Constraints Established in Stages I
and II.
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fence-line or spill monitoring, selection of sampling sites will be a
straightforward process. In other instances, such as studying transport
characteristics of certain TOAP's, site selection may be a detailed
process requiring the review of extensive meteorological data and may
result in the selection of many sampling sites. It is important to note
that appropriate selection of a sampling site can vary with the season or
over the course of the day; hence, the time frame over which samples are
collected from a given site can be as important a parameter as the site
from which samples are collected.
3.3.2. Analyta S«l«ction
Selection of the appropriate analyte(s) is a key element of the
monitoring plan. However, selection of too broad a range of compounds can
lead to excessive cost, whereas selection of too few may result in
non-attainment of the general program objectives. In most cases the
selection of a specific set of target compounds represents a compromise
between technical feasibility and environmental significance. For
example, if a particular compound is emitted from a source in a given
region and the program objective is to evaluate the environmental impact
of that source, then monitoring of this compound is a requirement,
regardless of technical limitations.
On the other hand, if a program has the objective of describing
transport of TOAP's over a wide region, selection of the compounds of
interest must be made with emphasis on technical feasibility. In this
case, methods capable of detecting a wide range of compounds
simultaneously should be employed, and compounds requiring specialized
procedures should be included only if the environmental significance of
the regional compounds is substantial.
A further consideration is the stability of a compound in the
atmosphere: If a compound is rapidly degraded in the atmosphere through
hydrolysis, oxidation, photolysis, or other processes, then one must
consider the option of monitoring degradation products rather than the
compound itself. Likewise, one must consider the possibility of formation
of a particular compound of interest in the atmosphere. For example,
formaldehyde is a common oxidation product of olefinic compounds in the
atmosphere. Therefore, if one wishes to describe the impact of a source
emitting formaldehyde, the formation rate of formaldehyde from olefinic
materials must also be considered.
3.3.3. Physical State of th« Analyt*
The physical state of the analyte(s) will be a major concern in terms
of selecting appropriate sampling and analytical protocol(s). While an
analyte may be emitted as a gas, condensation of the TOAP may result in
the formation of particulate or particle bound analytes. A sampling
procedure designed for the collection of gaseous compounds, such as the
use of a canister, will be inappropriate for particulate or particle-bound
TOAP's. Conversely, a solid TOAP may have sufficient vapor pressure to
require a sampling train designed for the collection of vapor phase
constituents to monitor atmospheric concentrations accurately.
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In most cases, the total concentration (gas as well as particle-bound)
of a component is sufficient information. However, if the particle-bound
concentration is of interest (e.g. for inhalation toxicology considera-
tions) one must recognize that the data will be influenced heavily by the
choice of a sampling technique.
3.3.4. Sampling and Analytical Protocol Selection
In many cases, the objectives of a program can be attained using class
specific screening procedures rather than more expensive compound specific
methods. Frequently, class specific or nonspecific screening techniques
can be conducted in the field, often in "real time." Consequently, the
use of a two-tiered (or "pilot" study) approach is often advisable,
wherein these procedures can be used to rapidly define emission "hot
spots," approximate concentrations, and types of compounds emitted.
Appropriate compound specific techniques can then be employed to gain more
detailed information.
The two-tiered monitoring approach is a simple example of using two
sets of technical objectives to meet a single set of general, overall
objectives. There are many other cases where overall objectives will be
best attained through the sequential accomplishment of specific technical
objectives. This approach allows the knowledge gained in one monitoring
effort to facilitate planning of subsequent efforts. In many cases, this
sequential approach may be the only viable alternative, due to information
gaps or technical limitations.
Method performance characteristics should be carefully considered in
the planning stage, since these characteristics have a very profound
effect on the cost and probable success of a project. The specified
ranges of the performance characteristics should be compatible with the
intended use of the data. In certain cases, regulatory requirements may
dictate the use of a specific sampling and analysis method. In such
cases, project personnel should continue to evaluate the method
characteristics and state any limitations impacting the success of the
project.
The major method characteristics of concern are:
• Detection limit.
• Accuracy (absolute and relative).
• Precision.
• Interferences (selectivity).
• Analysis time.
Obviously, the more stringently one defines these requirements, the more
costly a program becomes, often without a direct increase in useful
information. Conversely, if one does not specify sufficiently rigid
performance criteria, the data obtained may be of little value.
Unfortunately, these performance goals are difficult to define because of
the large number of determining variables (e.g. sampling location,
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sampling time, source composition, etc.) In addition, some of these
parameters (e.g. accuracy) are difficult to determine experimentally,
because the wide variation in matrix characteristics can influence them.
The increased availability of Standard Reference Materials (SRM's) and
improved instrumentation has resulted in increased accuracy for sampling
and analytical methods. Consequently, method performance characteristics
should be initially defined in terms of guideline "ranges" and should be
rigidly defined only in cases where the exact requirements are known.
Required detection limits will vary considerably, depending on the
compound of interest, the sampling location relative to the source,
meteorological conditions, available sampling time, and available
analytical instrumentation. Detection limits should always be defined in
terms of component concentration in air (ug/M or ppbv) rather than by
a method detection limit (e.g. in micrograms), since the latter value is
subject to a great deal of interpretation (e.g. sampling time, etc.) In
general, the range of detection limits required for toxic organics will
vary between 0.1 ppbv and 10 ppmv. Detection in the 0.1-10 ppbv range
will be required for ambient air studies where sites are remote from
emission sources, whereas 1-10 ppmv detection limits may be sufficient for
monitoring in the vicinity of chemical spills, dump sites, and other
concentrated sources. Obviously, highly toxic compounds will require more
stringent detection limits in most cases.
Certain classes of compounds (e.g. halogenated compounds) can be
detected at very low levels because of their unique characteristics and
the availability of special detectors. Consequently, one typically
obtains data on these compounds at low levels, irrespective of the project
requirements. However, alternative approaches in such cases include the
use of shorter sampling periods or more general procedures capable of
detecting other compounds of interest. These alternatives may reduce
costs without losing the desired information. Therefore, detection limit
criteria should not be based solely on the available detection limit,
since flexibility is lost in this process.
Some compound classes (e.g. highly polar materials such as alcohols
and acids) cannot be detected readily at ppb levels. For these compounds
one must decide whether or not the program objectives can be achieved
using available analytical methods, toxicological properties being the
primary consideration. If not, then one is left with the difficult choice
of either (a) undertaking a potentially costly development program to
improve the methodology or (b) reducing the program's requirements to
allow partial fulfillment of its objectives or (c) not undertaking the
program at all.
Accuracy and precision requirements are normally more flexible than
detection limit requirements and usually do not result in a major revision
of program objectives. However, several aspects of the accuracy and
precision requirement need to be addressed. The required accuracy is
defined primarily by the method of data comparison. If data collected on
one program are to be compared to data collected on another program, then
absolute accuracy is important. It is therefore important to know the
accuracy of the methods used in each program.
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However, if one simply desires to know the ratio of component
concentration at two sites or at the same site at different times of the
day, then relative accuracy may be more important then absolute accuracy.
In this case, the only requirement is that the method's accuracy be the
same for each data point. The relative accuracy concept is especially
useful when using class specific screening techniques, since the absolute
accuracy will be known only if the specific compounds giving rise to the
response are known, whereas the relative accuracy is known so long as the
relative proportion of the various compounds being detected is constant.
In a strict sense absolute accuracy for a method can be determined only
when a suitable NBS (or NBS traceable) standard is available and can be
analyzed under conditions duplicating the actual sampling and analysis
progress.
Precision requirements are somewhat related to accuracy requirements,
since for a given atmospheric concentration the measured quantity is a
function of both accuracy and precision. If one desires a certain degree
of confidence that a measured signal is representative, then an
appropriate number of replicate determinations must be made. The more
precise the method, the fewer measurements need be made to attain a given
degree of confidence in the data. Precision and accuracy will both
diminish as analyte concentrations approach the detection limit.
A method's specificity and the degree of interference by other
materials in a method must be considered in the definition of project
objectives since this influences data accuracy as well as the range of
compounds to be evaluated. If large quantities of innocuous compounds are
present at the sampling location, the selection of compounds of interest,
as well as sampling and analysis methods, should be based on circumventing
potential interference problems whenever possible. This problem often
limits usefulness of nonspecific screening procedures, since the response
from background components may overwhelm any response due to trace levels
of toxic materials. If such interferences cannot be avoided by judicious
selection of the analyte(s) of interest, then alternative sampling and
analysis procedures which minimize the interference problem must be
selected. In any case, compounds which represent potential interferences
in a given program should be listed, in addition to the compounds of
interest, to aid in the selection of appropriate sampling and analysis
techniques.
3.4. LOGISTICAL CONSIDERATIONS
A variety of logistical considerations must be evaluated in connection
with the development of the TOAP monitoring program plan. These factors
include the availability of manpower, instrumentation, and calibration
standards. TOAP monitoring programs will typically require highly skilled
personnel, non-standard methodology and/or instrumentation, calibration
materials of limited availability, or a combination of these factors.
If the monitoring program objectives are to determine the ambient
levels of TOAP's resulting from a temporary operation or to establish
seasonal variations in ambient TOAP concentrations, it is necessary to
juxtapose fixed monitoring periods with schedules for manpower,
instrumentation, and calibration standards. Such a comparison will most
certainly result in a modification of program objectives or of sampling
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and analytical protocols, if the required personnel, instrumentation, or
calibration standards are unavailable during the targeted sampling period.
3.5. DATA QUALITY FACTORS
A fundamental decision that must be made during the planning process
concerns data quality. The level of data quality required will be
determined by, and must be consistent with, the intended use of the data.
For example, if the possibility exists that the data will be used to
establish or refute legal liability, then the data must be of sufficient
quality to withstand legal scrutiny. If on the other hand, the data are
being collected for more esoteric purposes, then a lower level of data
quality may be acceptable. Program funding will impact attainable data
quality and therefore must also be consistent with the intended use of the
data.
3.6. COST FACTORS
A final and often overriding factor is the allowable cost.
Frequently, the cost is specified within limits, prior to any other
specific program objectives. While this state of affairs must be
accepted, such limitations should not be used as an excuse to collect low
quality data. If the specific program objectives cannot define a
technically feasible and scientifically valid program, then the only valid
alternative is a redefinition of scope, an expansion of available funding,
or termination of the program. The impact of limitations recognized by
technical project personnel must be clearly and openly stated to
appropriate management personnel, in order to avoid implementation of an
ilx-conceived monitoring program.
3.7. COMPILATION AND EVALUATION OF AVAILABLE INFORMATION
The efficiency with which an air monitoring program can be developed
and implemented is greatly dependent on the extent and quality of
technical information available during the development phase of the
program. In most cases this information will be used in an iterative
fashion to develop specific technical objectives for the monitoring
program, since such objectives must be realistic and achievable.
Information most useful in this process will generally include (a)
previous air monitoring data, (b) composition of emission sources in the
region, (c) meteorological conditions, and (d) sampling and analytical
methods and performance data for target analytes.
3.7.1. Assessment of Available Air Quality Data Base
Probably the most useful information is data from previous air
monitoring programs in the region. Although such information is seldom
directly relevant (e.g. due to differences in the compounds monitored,
sites used, or other program objectives), some aspects of the data
normally will be useful. For example, total hydrocarbon data from the
region may be useful in predicting sites and/or times with maximal
pollutant concentration. Data for a compound of interest may be available
from a site similar to the one of interest, thereby giving an "order-of-
magnitude11 estimate of pollutant concentration to be anticipated.
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Additional useful information which could be gained from such studies
includes compound stability in air under various conditions, degradation
products formed, other compounds present in conjunction with the compound
of interest, phase distribution of the compound in ambient air, and
performance data for sampling and analysis methods of interest. As with
all sources of information, critical evaluation is necessary in order to
determine the quality and relevance of the data reported.
The acquisition of air monitoring data is not particularly
straightforward because of the large number of sources of such data and
the wide variety of program objectives. Some primary sources of such data
include:
• National Air Toxics Information Clearinghouse (NATICH).
• Air toxics monitoring data base.
• U.S. Environmental Protection Agency, Research Triangle Park, NC.
• Regional offices of the USEPA.
• State and local environmental protection (or equivalent) offices.
• Contractors and universities performing work through contracts or
grants with EPA or related agencies.
• Peer review journal articles and government reports.
A wide variety of other government and related research organizations
may have available data in specialized areas (e.g. Electric Power Research
Institute, Palo Alto, California; Department of Energy; National Oceanic
and Atmospheric Administration).
Although a few data compilations are available, no single
comprehensive source of monitoring data exists. Consequently, the best
approach towards obtaining relevant data is to contact several sources
(local as well as regional or national) and to describe the type of
monitoring information desired. Since data specifically relevant to the
program are probably not available, one should seek to obtain any
potentially useful monitoring information. In many cases references
within these documents may lead to additional useful data.
Critical evaluation of available data should address the following
points:
• Documentation of sampling and analysis techniques, in terms of
detection limit, precision and accuracy, specificity, and
analysis speed.
• Sampling strategy in terms of reference points and spatial and
temporal resolution.
• Documentation of atmospheric conditions.
• Influence of emission sources in the region.
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The purpose of this evaluation should be to assess the relevance of the
data to the program being developed; therefore, aspects of the data having
no relevance to that program need not be evaluated.
Certain data bases contain much of the information required to assess
the usefulness of the data for TOAP monitoring purposes. Two such data
bases are described in the subsections that follow:
3.7.1.1. National Air Toxics Information Clearinghouse (NATICH) Data
Base
The National Air Toxics Information Clearinghouse (NATICH) has been
established by the U.S. Environmental Protection Agency, Office of Air
Quality Planning and Standards, to support state and local programs in the
control of non-criteria air pollutants. It is intended to facilitate
information exchange among state and local agencies and between EPA and
those agencies and to minimize duplication of effort. For the purposes of
the Clearinghouse, a toxic air pollutant is defined as any non-criteria
air pollutant. Inclusion of a pollutant in the Clearinghouse does not
necessarily mean that it is toxic at ambient concentrations. The
Clearinghouse consists of an on-line computerized data base (NATICH) which
contains information on potentially toxic air pollutants, hard copy
reports of information from the data base, special reports, and a
quarterly newsletter.
The NATICH data base (EPA 450/5-88-007) is updated regularly and
includes a list of state and local agencies that have provided information
to the Clearinghouse, air toxics contacts, regulatory program information,
acceptable ambient concentration guidelines or standards and the bases of
those guidelines/standards, pollutant research information, methods
development activities, permitting information, source testing
information, ambient monitoring information, emissions inventory
information, and risk assessment information. Review of relevant NATICH
data base information should be a preliminary step in the development of a
TOAP monitoring program.
3.7.1.2. Air Toxics Monitoring Data Base
The Air Toxics Monitoring data base (EPA/600/3-88/010A) is a
compilation of information addressing only volatile organic compounds.
Semi-volatile organics, nonvolatile organics, and pesticides are
intentionally excluded from the data base. The program initially focused
on ambient outdoor VOC concentrations in areas remote from emission
sources. It has been expanded to include residential and commercial
indoor air quality data but not industrial indoor air quality data. The
data base includes information relating to the Toxic Exposure Assessment
Monitoring (TEAM) Program, the Toxic Air Monitoring Sites (TAMS) Program,
and the Urban Air Toxics Monitoring Program.
The data base is composed of five files:
e The VOC concentration file - contains information concerning
measured concentration, sampling period rankings, and ratings.
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• The site file - contains information concerning the location of
the sampling program.
• The methods file - provides information concerning the sampling
and analytical protocol employed to generate the data.
• The reference file - contains information concerning the
investigator, program objective, year of the study, and
literature citations.
• The chemical filq - summarizes compounds, CAS numbers, and
measured concentrations contained in the data base.
Data base information can be accessed by reference, site, or chemical
compound.
3.7.2. Assessment of Toxic Organic Air Pollutant Sources
Since most ambient air monitoring programs will be impacted by
emission sources in the region, data concerning the composition of such
emission sources are extremely useful. Programs having the objective of
assessing the impact of a particular source on the environment obviously
require knowledge of the source composition, whereas other programs need
source emission information to avoid biasing the data, as a result of
contamination by the source. Typical sources of concern include:
e Chemical production, processing, or handling facilities.
• Fuel sources (gasoline stations, storage tanks, etc.)
e Mobile sources (automobiles, etc.)
e Chemical waste landfills, lagoons, etc.
e Miscellaneous sources (dry cleaners, sewers, residential heaters,
etc.)
Information concerning emission components from chemical production or
related manufacturing facilities may be available from the plant
operator. Discharge permits represent another source of information.
Since such facilities differ widely, depending on the chemical processes
contributing to the emissions, one can seldom rely to any great extent on
information available from similar facilities. Furthermore, if the
program objective is to assess the impact of the source on regional air
quality, simultaneous measurement of the source emissions and the ambient
air is highly desirable, since the composition of a single source can vary
considerably with time. Knowledge of production schedules and similar
factors is extremely useful in predicting the degree of variability.
In the case of fuel sources, mobile sources, dry cleaners, etc. the
qualitative nature of the emissions can be predicted fairly well, since
these sources have been extensively characterized, and in the case of
dry-cleaners only one or two compounds (perchloroethylene or Stoddard
solvent) are in use. Consequently, one can predict in advance whether or
not these sources will interfere with the ambient air monitoring effort.
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In general, a useful monitoring approach, assuming these source
contributions are not being evaluated, is to locate sampling stations at
sites remote and/or upwind from such sources (but downwind from other
sources of concern), using screening techniques such as flame ionization
or photoionization detection to locate the points of high source
contribution. This approach requires that only the location of the source
be determined, not its detailed composition. However, if the contribution
of such sources to regional air pollution is being evaluated, knowledge of
the detailed source composition will be required and should be made part
of the overall monitoring program.
3.7.3. Assessment of Meteorological Data
Knowledge of meteorological conditions is important to ambient air
monitoring programs in several regards. The impact of a particular source
on regional air quality will be highly influenced by meteorological
conditions, since dilution rates, transport rates, and compound stability
are dependent on these conditions. Overall regional air quality,
representing the summation of source contributions, will be influenced by
these conditions, in the same manner.
A detailed discussion of meteorological considerations in air quality
monitoring is given in the Air Pollution series by Stern (3) and is beyond
the scope of this document. Meteorological parameters of primary concern
include the following:
• Hind speed and direction.
• Temperature.
• Barometric pressure.
• Solar radiation intensity.
• Precipitation.
• Mixing height.
While these data should be collected during the course of the monitoring
program, prior knowledge of typical conditions can be extremely useful in
selecting sampling points.
Regional meteorological data can be obtained from the National Weather
Service in the relevant locality. However, one must recognize that
localized meteorological conditions, not apparent from the National
Weather Service data, can exist. For example, wind speed and turbulence
can be affected by obstructions such as tall buildings in the area. Fog
may occur selectively in marshes or in hilly areas. Surveillance of the
sampling site and discussions with persons familiar with the area can be
useful in selecting sampling sites under favorable meteorological
conditions.
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3.7.4. Assessment of Relevant Sampling and Analytical Methodologies
Availability of suitable sampling and analysis techniques is often the
limiting factor in the development of a comprehensive air monitoring
program, in spite of the large number of techniques which exist. Since
virtually every air monitoring program has a different list of compounds
of interest, a variety of techniques are required to cover this range of
components, resulting in a significant cost impact on the program.
Furthermore, unique requirements in terms of specificity, detection limit,
analysis time, and other performance characteristics may require
modifications to existing methods. Consequently, a highly desirable
approach is to develop program objectives which are in consonance with the
capabilities of available sampling and analysis techniques, wherever
possible. In order to use this approach without severely limiting the
program objectives, one must have available as much relevant information
as possible on sampling and analysis techniques.
Primary sources of sampling and analysis methods include the
following:
• National Institute for Occupational Safety and Health (NIOSH)
Methods (4).
• American Society for Testing and Materials (ASTM) Methods (5).
• Methods-of Air Sampling and Analysis (6).
• Compendium of Methods for the Determination of Toxic Organic
Compounds in Ambient Air (7).
• Peer review, journals, and government reports.
Methods for a number of toxic organic compounds of particular concern are
presented in Sections 4 and 5. Contact with various persons active in air
quality monitoring is also an effective means of gathering recent
information on sampling and analysis methods. The NIOSH and many ASTM
methods are designed for workplace or source concentrations and may
require substantial modification to detect ambient concentrations.
Available sampling and analysis methods should be evaluated with
regard to the following performance characteristics:
• Selectivity (range of compounds detected and potential
interferences).
• Detection limit.
• Precision and accuracy (often unknown).
• Analysis time.
• Cost of analysis.
• Quality of performance evaluation data.
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The methods should be evaluated from two standpoints: (a) the degree to
which method performance has been documented under conditions similar to
those expected and (b) the adequacy of the performance characteristics for
achieving the program objectives.
If method performance is not well documented, one must decide whether
or not to include further documentation, with the resultant increase in
data quality as well as cost, as part of the monitoring program. A
similar decision must be made when existing methods are slightly modified
(e.g. extended to similar compounds, etc.) One must recognize that some
assumptions concerning method performance will inherently be part of any
monitoring program, due to cost and time limitations (i.e. documentation
of all performance characteristics under each set of monitoring conditions
is prohibitively time consuming and expensive). Consequently, those
assumptions which are made should be technically sound and carefully
documented.
3.8. SELECTION OF SAMPLING AND ANALYSIS METHODS
Once a set of program objectives, including specification of the
analytes of interest, have been developed and information concerning
sampling and analysis techniques has been evaluated, the next logical step
is selection of the sampling and analysis procedures to be used in the
monitoring program. Factors to be considered in selecting sampling and
analysis methods include (a) physical and chemical properties of the
compounds, (b) relative and absolute concentrations of the compounds, (c)
relative importance of various compounds to program objectives, (d) method
performance characteristics, (e) potential interferences present at site,
(f) time resolution requirements, and (g) cost restraints. The selection
process will be accomplished by:
• Subdividing compounds into logical groups based on similar
analytical characteristics. This process will result in a
preliminary selection of generic analysis techniques, since
analytical techniques must be considered in the grouping process.
• Specifying detailed analytical procedures based on the guidance
provided by the grouping process, considering accuracy,
precision, time, and cost requirements, as well as incorporating
additional cleanup schemes based on selectivity requirements, if
necessary.
• Evaluating sampling procedures bacc.1 on analytical requirements
and physical properties of the compounds to ensure that the
sampling and analysis methods are compatible.
• Specifying sampling and analysis parameters (sample volumes,
final extract volumes, etc.) based on detection limit
requirements.
• Reconciling conflicts between program objectives and sampling and
analysis capabilities. Redefining objectives and/or undertaking
procedure development efforts, as required.
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• Documenting "standard operating procedures" for the sampling and
analysis methods.
The important chemical and physical properties to be considered
include thermal stability, volatility, polarity, ionic character, phase
distribution, and chemical composition. The manner in which these
properties determine the suitability of analytical as well as sampling
procedures is discussed in Sections 4 and 5.
Volatility, thermal stability, polarity, and ionic character determine
the extent to which commonly-used gas chromatographic procedures are
suitable for the compounds. These properties also must be considered in
the selection of sample preparation procedures, since solvent extraction
and concentration procedures may result in loss or degradation of volatile
or thermally labile compounds.
Phase distribution (gas/particle) of a compound is obviously dependent
on the other physical and chemical properties but must be considered
separately, since sample preparation procedures for particle bound
compounds will usually be different from those for gas phase compounds.
Compounds likely to be present in both phases require special
consideration. Sampling methods can sometimes be employed to drive the
equilibrium into one phase or the other if only the total concentration is
to be determined (e.g. by using a heated filter). Methods capable of
determining the phase distribution of the analyte are described in the
literature (52) .
Chemical composition, specifically the presence of heteroatoms, is
often the most important factor in assigning compounds to a particular
analytical group. Specialized chromatographic detection systems tend to
be specific for a particular class of organic compounds, and selective
colorimetric procedures are available for certain classes of compounds as
well. However, one must avoid oversimplification of the grouping process
by automatically placing compounds having a particular functional group in
a single class. Individual compounds may have unique properties, making
placement in another class more suitable. For example, gas chromatography
with electron capture detection (GC/EC) is sensitive and selective for
detection of many halogenated compounds but does not respond well to vinyl
chloride, chlorobenzene, or 1,2-dichloroethane. Thus, these compounds
should not be grouped with other halogenated compounds targeted for GC/EC
analysis.
3.8.1. Analytical Methodology Consideration*
Familiarity with the analytical procedures available is an obvious
requirement in the compound grouping process. One must recognize that
analytical procedures include both sample preparation and compound
determination steps, each of which must be considered when assigning a
compound to a particular analytical group. Simply specifying gas
chromatography/mass spectrometry (GC/MS), for example, as the analytical
technique does not define an analytical procedure.
The anticipated relative concentrations of the various compounds of
interest should also be considered in the grouping process. Compounds
present at high levels may be candidates for direct analysis in the field
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(e.g. by portable GC), since sample concentration techniques might not be
necessary. At the other extreme, trace components may require sample
concentration, as well as cleanup steps, to obtain sufficient sensitivity
and selectivity.
A final consideration in the grouping process is the relative
importance of the various compounds to the program objectives. While a
formal priority ranking of the compounds normally is not required, one
should consider relative importance in the following qualitative manner.
Compounds of special concern, either because of high toxicity or known
emission sources, should be grouped so as to optimize analytical
performance for these compounds. In certain cases this process may
include placing compounds of high priority in unique groups targeted for
specialized, specific analysis techniques. Compounds of lesser interest
should be placed in the appropriate groups selected for optimal detection
of the compounds of primary concern, usually with some compendium of
analytical performance.
The selection of analytical procedures is largely guided by the
compound grouping process in which the available analytical techniques are
heavily considered. However, the definition of analytical procedures in
terms of specific operating parameters should normally await completion of
the grouping process.
Relatively few standardized analytical procedures for toxic organics
are available. Consequently, program technical personnel will normally
have the responsibility of defining specific sample preparation procedures
and chromatographic operating conditions, as well as writing the detailed
standard operating procedures for the monitoring program. Factors to be
considered in this selection process include required detection limit,
specificity, accuracy, precision, analysis time, and cost, all of which
are also considered in the development of project objectives. The task of
specifying standard operating procedures for analytical methods must be
accomplished in conjunction with the specification of sampling protocols,
since detection limits and other method performance characteristics are a
function of both steps.
Accuracy, precision, analysis time, and cost are determined by the
choice of sampling and analytical techniques and, in many cases, cannot be
substantially improved by refinement of the methods. Consequently one
must weigh these factors carefully during the method selection process, to
ensure that the program requirements are achievable using the technique
selected, Method specificity can be altered to some extent by the
addition of cleanup steps to the analytical methods but is still highly
dependent on the type of detection system used.
Detection limits, on the other hand, can be substantially adjusted by
the selection of specific operating parameters within the sampling and
analytical methods. Parameters contributing to the detection limit
include:
• Detector sensitivity (minimum quantity of material which gives a
detectable response when introduced into the instrument ).
• Proportion of sample introduced into the instrument.
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• Volume of sample collected.
• Recovery of component through the entire sampling and analysis
procedure .
These parameters are, in turn, dependent on other factors. Detection
sensitivity is dependent on the concentration of background components in
the sample (i.e. practical detection sensitivity is limited by
interference from background components, not by absolute instrument
sensitivity) . The proportion of sample which can be introduced into the
instrument is also dependent on the quantity of background components
present and can be substantially increased by the use of additional or
more effective cleanup techniques. Component recovery, on the other hand,
can be adversely affected by the incorporation of additional cleanup
techniques into the method.
3.8.2. Sampling Methodology Considerations
Because of the limited number of sampling methods available, the
selection of specific sampling methods is best accomplished after the
definition of analytical requirements based on compound groups of
interest, etc. However, the specification of detailed analytical
procedures obviously requires knowledge of the sampling scheme (e.g.
physical state of the sample presented for analysis, sampling volumes,
etc.) .
Primary factors to be considered in the selection of sampling
procedures include phase distribution, stability, time resolution
requirements, and analytical requirements. Compounds entirely contained
in the particle phase can be readily sampled using filtration, whereas gas
phase components require more elaborate techniques such as resin sorption,
impinger collection, cryogenic trapping, or evacuated canisters.
Stability of the components of interest during the sampling process must
be considered. If necessary, samples can be removed from the sampling
apparatus and stabilized (e.g. frozen) to prevent degradation. Stability
can also be affected by the collection of reactive components
NO , d-2' ®tc-)- Therefore, sampling techniques which minimize the
collection of such components should be selected whenever possible.
Time resolution requirements may prevent the use of certain techniques
which cannot acquire sufficient sample in the required time period. If
extremely fine time resolution is required, continuous monitors (e.g.
flame ionization or photoionization detectors) may be the only acceptable
alternative. Techniques of this type are usually not specific for
particular organic components, and this limitation must be weighed against
the importance of time resolution.
After sampling and analysis procedures have been selected, the
specific details of these methods (e.g. sampling volumes, cleanup steps,
etc.) can be selected, considering the detection limit requirements in
particular. Subsequently one must examine the program objectives to
determine the capability of the sampling and analysis scheme to accomplish
these goals. Once any differences between sampling and analysis
capabilities and program objectives have been resolved, the sampling and
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analysis procedures should be written into detailed "standard operating
procedures" as a final step in the method specification process.
3.8.3. Selection of Sampling Strategy
Selection of a sampling strategy capable of meeting the program
objectives is vital to the success of any monitoring program. Parameters
which must be specific include:
• Sampling locations.
• Numbers, sampling volumes, and time points of samples to be taken
at each location.
• Meteorological parameters to be monitored and dependency of
sampling strategy on these parameters.
The development of a sampling strategy can be extremely simple or
extremely complex, depending on the program objectives. Programs
involving characterization of the pollutant contribution from a point
source tend to be more straightforward, whereas programs investigating
fate and transport characteristics of components from diverse sources
require more elaborate sampling strategies. An excellent discussion of
the factors to be considered in developing a sampling strategy is provided
in the Air Pollution series by Stern (8).
The selection of an optimal sampling siting plan must take into
account the following factors:
• Locations of stationary as well as mobile sources.
• Transport characteristics of pollutants from these sources and
influences of meteorology and topography on these
characteristics.
• Spatial resolution required to meet program objectives.
• Availability of space and utilities for operating sampling
equipment at potential sites.
Relevant information on optimum site selection criteria are available
in various EPA documents (9). One should consult such documents when
developing a siting plan.
The necessity for locating stationary and mobile sources prior to site
selection has been previously discussed and should be readily apparent.
One must not only have knowledge of the existence of these sources but
also the trajectory of emitted pollutants under the existing
meteorological and topographical conditions. Avoiding sample
contamination by these sources or, conversely, accurately measuring the
pollutant contribution of these sources may require continuous monitoring
of meteorological parameters and adjustment of sampling location or
timing, accordingly. In some cases the siting process can be aided
through the use of air quality models, in particular disperson models
which predict concentration profiles for pollutants emitted from point
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sources under various meteorological conditions. The placement of
reference (control) sites upwind of known emission sources is included in
most monitoring schemes to determine the contribution of those sources.
Additionally, wind direction must be continuously monitored in these
situations to ensure the validity of the reference samples.
Spatial resolution requirements obviously are highly dependent on the
program objectives. If one is attempting to estimate pollutant
concentrations in the vicinity of a point source (e.g. hazardous waste
landfills), spatial resolution of a few tens or hundreds of meters may be
required, whereas programs monitoring pollutant transport through an urban
area may require resolution of a few miles or tens of miles. In
determining spatial resolution requirements, one must realize that a
sampling site provides only the concentration at a given point, and that
data point is used to represent the pollutant concentration over the
entire area between the sampling site and adjacent sampling sites.
Consequently factors which lead to spatially inhomogeneous pollutant
concentrations must be carefully considered in the siting process (i.e.
spatial resolution requirements will be more restrictive in areas of
inhomogeneous concentrations). Such factors include low wind velocities,
presence of tall buildings and other obstacles, and source emission
variability.
In certain specialized cases vertical as well as horizontal resolution
is required. In most cases vertical sampling requires use of an aircraft
acquiring samples at various altitudes, depending on air flow
characteristics. Since this requirement is infrequently encountered in
TOAP monitoring, further discussion here is not warranted.
The use of mobile sampling facilities to provide greater flexibility
(e.g. in response to changes in wind direction, etc.) is an attractive
option in many cases and can be a cost-effective means of providing
greater spatial resolution. In many cases a continual screening monitor,
such as a photoionization detector, may be used to define the need for and
optimal placement of fixed monitoring stations.
A final consideration in the siting process is the availability of
space and utilities for operating sampling equipment. This requirement is
well recognized and does not require a great deal of emphasis in this
document. Obviously, the selection of sites should be done with the
knowledge of available locations and utilities. However, in cases where
utilities are not readily available, portable utilities (e.g. generators,
heaters, or air conditioners) must be provided. In many cases these
portable units represent a potential pollution source, and hence,
contamination of samples may result if their placement is not carefully
considered.
After selection of appropriate monitoring locations one must consider
the sampling requirements in terms of timing and numbers of samples. In
many respects time resolution and spatial resolution requirements place
similar demands on the sampling scheme. Continuous screening monitors can
be used to determine time of dependency of pollutant concentrations and
can thus define time resolution requirements more accurately. As with
spatial resolution, time resolution requirements may not be uniform for a
given program. Certain time periods may require finer time resolution
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than other time periods (e.g. related to traffic patterns, production
schedules, etc.).
In order to achieve adequate time resolution, one must be able to
collect sufficient sample in the allowed time. In some cases the sample
quantity requirements may result in the need to use multiple sampling
devices at each sampling location, although modern analytical instruments
tend to provide sufficient sensitivity to obviate this situation.
The numbers of samples to be collected at each site/time point are
obviously dependent on the variability of the sampling and analysis
methods, the precision requirements of the program, and cost limitations.
In many cases replicate analysis of a single sample, rather than replicate
sampling, will be employed, in which case only analytical precision is
determined. In other cases samples, collected at different times and/or
sites may be treated as replicate samples, due to homogeneous spatial and
temporal distribution of pollutants, hence overcoming the need to take
multiple samples at each site/time point.
Sampling volume, discussed in the previous section of this document,
may become a variable in the monitoring strategy as well. If pollutant
concentrations varying over a wide range (not predictable in advance) or
pollutants of greatly differing concentrations are to be monitored, one
should consider the possibility of collecting multiple samples of varying
volumes at each site/time point. In this manner one has some assurance
that at least some of the samples will contain levels of analyte within
the operating range of the analytical instrument. This approach is vital
in certain cases when the entire sample is introduced into the analytical
instrument (e.g. Tenax resin/thermal desorption techniques) and is of
lesser importance when a selectable proportion of the sample is analyzed.
Meteorological parameters to be monitored usually include temperature,
barometric pressure, wind speed, wind direction, relative humidity, and
precipitation. Wind speed and direction are probably the most important
variables impacting the sampling strategy. In many cases one may wish to
sample only when the wind is in a certain direction, to take advantage of
favorable source transport characteristics. In some cases meteorological
parameters may impact upon spatial and temporal resolution requirements in
such a manner that variations in these parameters will change the sampling
strategy over time.
3.9. QUALITY ASSURANCE PLANKING
The term quality assurance (QA) refers to an overall system design to
monitor, document, and control the technical performance of a program.
While the need for good QA protocols is widely recognized, the design and
implementation of them are frequently treated as secondary parts of the
overall monitoring program. If the QA protocols for a monitoring program
are to serve a useful purpose, they must (a) be readily implemented within
the coat and time constraints of the program and (b) be well understood by
the project personnel. Preparation of the QA plan for a monitoring
program should be undertaken after the sampling strategy and the sampling
and analysis methods have been defined.
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An effective QA plan for a TOAF monitoring program must address five
basic areas: (a) quality assurance management, (b) sampling quality
assurance, (c) analytical quality assurance, (d) data reduction quality
assurance, and (e) reporting quality assurance. Specific considerations
for quality assurance activities in each of these five key areas are
summarized in Table 3.2. Each of these topics is addressed thoroughly in
Section 7.
A series of volumes entitled Quality Assurance Handbook for Air
Pollution Measurement Systems (10) serves as a useful, detailed guidance
document in the QA area. In particular, Volume I - Principles and Volume
II - Ambient Air Specific Methods may be useful in the field of toxic
organic monitoring. Specific guidance for preparation of QA plans is
provided in another EPA document (11). QA practices are also discussed in
Methods of Air Sampling and Analysis (6).
3.10. DEFINITION OF DATA REPORTING FORMAT
Many air monitoring programs are undertaken without prior definition
of the data reporting format. In some cases this approach is justified
because of the unexpected nature of the data obtained (e.g. unexpected
compounds detected or previously unknown sources identified). However, to
the extent possible the format for data presentation should be defined
prior to initiation of the monitoring effort. This practice helps to
identify limitations of the available data and further clarifies the
extent to which technical and management or policy personnel understand
the program objectives.
The optimal format for data presentation is obviously highly dependent
on the program objectives and the quantity of data obtained. In cases
where only a few data points are obtained around a point source (e.g. a
hazardous waste landfill) tabular presentation of data (compound
concentrations at each site) may be appropriate. However, in most
monitoring situations the quality and complexity of the data set will
require graphical presentation. This type of data format requires
definition of the important variables to be considered (e.g. source
locations, sampling times, sampling sites, meteorological effects, etc.)
Statistical methods for evaluating correlation between the important
variables are usually required to obtain meaningful conclusions from the
data set.
3.11. SAFETY CONSIDERATIONS
Safety considerations in air monitoring are similar to those for other
chemically related occupations but should be considered for each air
monitoring program, since unusual hazards may be present in these
situations. Potential safety hazards can be subdivided into the following
broad categories:
• Chemical hazards.
• Electrical equipment.
• Mechanical equipment.
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TABLE 3.2
QUALITY ASSURANCE (QA) ACTIVITIES TO BE
SPECIFIED IN PROGRAM PLAN
Quality Assurance (QA) Management
QA System Design.
Document Control.
Data Evaluation and Storage.
Audit Procedures.
Corrective Action.
QA Reports to Program Management.
Training.
Sampling Quality Assurance
Site Selection.
Instrument Calibration and Maintenance.
- Collection of Routine Quality Control Samples.
- Data Recording.
Sample Labeling, Preservation, Storage, and Transport.
Chain of Custody Procedures.
Analytical Quality Assurance
- Method Validation Requirements.
Instrument Calibration and Maintenance.
Quality Control Sample Analysis.
Data Recording.
Data Reduction Quality Assurance
- Merging Sampling and Analysis Data Files.
Storage of Raw and Intermediate Data.
Data Validation.
Reporting Quality Assurance
- Technical Review of Report.
Editorial Review of Report.
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Chemical hazards include toxic chemicals such as carcinogenic
compounds, corrosive chemicals such as concentrated acids or bases, and
explosive hazards such as compressed gases. Protective equipment should
be employed to minimize direct exposure to such hazards. Since most air
monitoring programs require working with concentrated standards of toxic
organic compounds, special emphasis should be placed on minimizing
exposure to these materials. Programs involving investigation of
concentrated or potentially concentrated sources of hazardous organic
compounds require additional safety protocols to protect workers in the
field as well as laboratory workers who could be unexpectedly exposed to
concentrated samples collected at such sites.
Hazards from corrosive chemicals, compressed gases, glassware,
mechanical equipment, and electrical equipment are presented in a variety
of safety texts and do not require special emphasis here. However, these
hazards should be addressed in the monitoring plan.
3.12. MANPOMER REQUIREMENTS
A significant amount of discussion has been directed at the many
elements that comprise an effective monitoring plan. It is important to
remember that properly trained personnel with appropriate levels of
experience must be available when needed, to ensure the success of the
monitoring program. Personnel may be involved with several simultaneous
projects, so it is important that careful attention be given to personnel
scheduling, to ensure that no project suffers due to unavailability of
human resources.
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SECTION 4
OVERVIEW OF SAMPLING METHODS
4.1. PHYSICAL AND CHEMICAL PROPERTIES
The selection of an appropriate sampling technique is a crucial
decision that significantly impacts the success of a monitoring program.
The sample collection process is often one of the major sources of error
in determining concentrations of atmospheric toxic organics. An obvious
initial consideration is that of the physical and chemical characteristics
of the compound(s) of interest. Selection of the most effective
collection apparatus based on the analyte's specific physical and chemical
profile should be the sampling method selection objective.
Physical properties to be considered include boiling point, vapor
pressure, polarity, and solubility in water and organic solvents. There
are several good handbooks (12, 13, 14, and 15) which can be consulted to
obtain information concerning the physical and chemical properties of
organic compounds.
Ambient air contains a complex range of trace level organic compounds
which have diverse physical and chemical characteristics. For simplified
further discussion, they have been grouped into the following categories
based on their degree of volatility.
4.1.1. Volatil* Organic Compounds
Volatile organic compounds (VOC) is a general term used to describe
the gaseous non-methane organic emissions from a variety of sources.
These compounds have vapor pressures greater than 10 kPa and thus are
predominantly found in the gaseous state in the atmosphere. Much of the
present work dealing with organic compounds in air has been done on VOC's
because they allow for high volume sampling and can be efficiently
thermally desorbed from the sample collection medium.
Sampling with solid sorbents is one of the most widely used methods
for VOC collection. Typically, large volumes of air are passed through a
sample train containing several cartridges of an inert adsorbing material
o R
such as Tenax , XAD-2, or Porasil . The organic constituents are
adsorbed and concentrated on the sorbent surface. Unfortunately, solid
sorbents are not compound specific; analyte breakthrough can occur; and
all organic compounds may be collected. Separation is usually
accomplished by thermal desorption or solvent extraction, followed by gas
chromatographic analysis. A wide variety of solid adsorbents are
available and have been used and determined to be appropriate for specific
needs. These will be discussed in more detail in Section 4.2.1.
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Canister-based sampling systems have been evaluated and improved for
collecting VOC's. Comparisons between Tenax and canister collection
has been conducted (16,17), and comparative guidelines have been developed
which yield statistical inferences as to the equivalency of the two
sampling techniques. As a result of these developmental efforts,
commercial canister-based ambient air samplers are now available.
Other methods which continue to be modified to collect VOC's more
effectively include cryogenic condensation, impinger collection,
derivatization techniques, and passive samplers. While these methods are
promising, sampling systems which employ either solid sorbents or
evaluated canisters represent the standard for VOC sampling work.
4.1.2. Semi-Volatile Organic Compounds
Semi-volatile organic compounds (SVOC's) are not as easily collected
for analysis as the VOC's. However, attention has been focused at
resolving the problems associated with SVOC's found in ambient air.
Members of this class include polynuclear aromatic hydrocarbons (PAH) with
four or fewer fused rings, their halogenated derivatives such as PCB's,
organopesticides with chlorine and phosphorus, and various
chloro-p-dibenzodioxins. Vapor pressures of these compounds range from
10~ kPa to 10~ kPa. These less volatile compounds are present in the
atmosphere, both in the gaseous phase and in a particle-bound phase. This
presents the problem of quantitative collection requiring phase
distribution analysis. Attempts at vapor-particle distribution
determination have been made with uncertain success.
An effective sampling system for SVOC's employs a quartz (or other low
background) filter substrate followed by a vapor trap. The components of
interest are desorbed from both the filter and the vapor trap and analyzed
for SVOC content. It is incorrect to assume, however, that the SVOC found
in the filter represents the entire particle-bound phase while the
concentration of SVOC desorbed from the vapor trap comprises the gas phase
SVOC. Some SVOC will be transferred from the particle-bound phase to the
vapor trap during the sampling process. The distribution between phases
is also dependent on temperature and the degree of volatility of the
compound(s) of interest. For these reasons phase distribution analysis is
a complex determination. This will be discussed further in Section 4.4.
P
A side-by-side sampling comparison of Amberlite XAD-2 resin and
polyurethane foam (PUF) revealed XAD-2 has better collection and retention
efficiency for small ring SVOC (18) . Both foam and resin performed well
on larger, less-reactive compounds.
Several works have adapted current high volume air sampling
methodology to collect SVOC's; see for example Reference 19 and Method
TO-9, Reference 7: Sampling and Analysis of Chlorinated Dibenzo-dioxins
and Furans.
A data base for the chemical, physical, and thermodynamic properties
of 720 polycyclic aromatic compounds (PAC) has been compiled on personal
computer discs, using SCIMATE data management software (20). This
information can be useful in the selection of a sampling method.
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4.1.3. Nonvolatile Organic Confounds
Ambient air contains relatively low amounts of nonvolatile organic
compounds (NVOC). These are compounds with vapor pressures less than
10 kPa, and are almost always found in the condensed particle-bound
state. Polynuclear hydrocarbons with more than four rings, and their
nitrogenous and oxygenated derivatives are the major constituents of this
category (21) . The predominant method for measuring NVOC is collection
using a high volume filtration device followed by solvent extraction. A
system of this nature has been described in detail (22).
4.2. METHODS FOR GAS PHASE COMPONENTS
Compounds which are predominantly in the gas phase at ambient
temperatures and pressures are generally sampled by passing the air sample
through a filtration device to remove the particulate matter before
subsequent capture of the gaseous compounds. In selected cases, direct
analysis of the filtered gas stream is possible, circumventing the need
for the capture and/or pre-concentration process (e.g. direct GC with /FID
or ECD) (23). This situation is rare in ambient air monitoring for toxic
organics because the low concentrations generally make pre-concentration
of the sample a necessity. A general discussion of various sampling
approaches for gas phase components is provided in Katz's book (24).
4.2.1. Solid Adsorbents
Solid adsorbents are the most frequently used sampling media for gas
phase organics in ambient air because they allow a large volume of air to
be sampled relative to other techniques. Solid adsorbing materials can be
grouped into three categories:
• Organic Polymeric Adsorbents.
• Inorganic Adsorbents.
• Carbon Adsorbents.
4.2.1.1. Organic Polymeric Adsorbents
i>
Tenax GC is a porous organic polymeric adsorbent that has probably
been used and researched more than any other material for the purpose of
organic gas sampling. Initially introduced as a GC column packing
material, its inertness, low affinity for water, and high thermal
stability make it an excellent adsorbent for most volatile organic
compounds with molecular weights ranging up to several hundred AMU.
«
Performance audits conducted on sampling systems using Tenax
cartridges have revealed inconsistencies which necessitate precautions and
adherence to quality assurance procedures to minimize error (25,26).
Tenax GC requires thorough conditioning prior to use in order to
minimize contamination. This is accomplished by simultaneously purging
the cartridge with an inert gas and heating the gas to a high
temperature. Tenax TA, a specially processed Tenax, is specifically
designed as a trapping agent with very low levels of potentially
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interfering impurities; however, conditioning is still recommended for
Tenax TA. (Interference due to toluene and/or benzene is a common problem
associated with improperly conditioned or aged Tenax.) It should be noted
that conditioning of the adsorbent does not completely eliminate the
problem of interference. Other complications are also encountered with
solid adsorbents. For example, artifact formation resulting from reactive
air components such as ozone, NO , and SO interacting with organic
compounds or the sampling media may occur during sampling, storage, or the
recovery process. Thermal degradation of the polymer matrix resulting in
the production of detectable levels of interferents is another problem
associated with Tenax.
Another limitation of this technique is the fairly low breakthrough
volumes (the volume at which the analyte species begins to elute from the
sorbent during sampling). Sample volumes are therefore required to be
less than the smallest breakthrough volume for the compounds of interest,
and backup cartridges are required. While breakthrough volumes have been
studied for individual compounds, complex interactions occur when many
species are present. These interactions generally lower breakthrough
volumes determined from pure materials and introduce considerable
uncertainty in the selection of sample volumes.
For these reasons, solid sorbent sampling trains designed for
simultaneous collection of samples at different flow rates are often
employed. This approach, termed "distributed air volume sampling,"
identifies samples which may have been adversely affected during the
sampling, storage, and desorption process. The recommended procedure uses
a set of four samplers simultaneously collecting different volumes of air
(e.g. sample volumes of 10-15L, 20-30L, 40-60L, and 80-100L are
recommended for Tenax). Comparison of the four data sets can result in
the identification of problems associated with sample collection, storage,
and/or sample desorption. It is also important that the sampling and
analysis scheduling be thoroughly coordinated to permit prompt analysis.
R
XAD resins are another popular solid sorbent. When coupled with a
quartz prefilter, XAD resins are superior to polyurethane foam (PUF) for
polyaromatic hydrocarbon sampling (18) . There are fewer problems
associated with PAH breakthrough, loss, and degradation when XAD resins
are used. The retention characteristics and sorbent capacities on XAD-2
resin for many chemicals are provided in EPA publication 600/7-78-054.
Polyurethane foam (PUF) is another organic polymeric adsorber that has
been used for collection of SVOC pesticides, polychlorinated biphenyls
(PCB's), and dioxin vapors. Low volume sampling with PUF is utilized in
Method TO-10 for the analysis of pesticides. The PUF cartridge is easy to
use and has good air flow characteristics. EPA has evaluated the use of
PUF samplers and three cleanup methods associated with them (28). The
cleanup methods are compression rinsing, Soxhlet extraction, and a
combination of both. Results indicate compression rinsing alone is
sufficient for contaminant removal prior to sampling.
Styrene copolymers have been studied as air samplers. Benzene and
acetone breakthrough volume determinations have been performed on Poropak
Q and Chromosorb 101, 102, and 103 (29).
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These are a few of the many porous polymers used frequently for air
sampling because of their many desirable advantages. One major
disadvantage of polymeric sorbents is the inability to capture highly
volatile organic compounds such as vinyl chloride and certain low
molecular weight polar compounds (21) . A modified polymer material
(Eu-sorb ) has been developed which specifically captures very volatile
polar organic compounds such as aldehydes, ketones, and nitriles by
forming a metal complex. A comparison between the metal chelating
R R
Eu-sorb with Tenax TA and Chromosorb 102 revealed Eu-sorb to have
large breakthrough volumes and to be more efficient at pre-concentrating
highly volatile polar organics (30). Its use has been limited, but
potential applications are promising.
4.2.1.2. Inorganic Adsorbents
P
Inorganic adsorbents include silica gel, alumina, Florisil ,
Porasil , and inorganic molecular sieves. These materials are
considerably more polar than organic polymeric sorbents and thus capture
polar compounds. Water can be efficiently captured on certain media and
result in deactivation of the material. Consequently, these adsorbents
are rarely used to collect trace organic compounds, except in cases where
relatively high concentrations of certain polar organics are prevalent.
Silica gel will adsorb compounds with hydroxyl groups such as alcohols and
phenols and other oxygen-containing compounds such as esters, aldehydes,
ketones, and organic esters. Tlorisil has been used to collect
chlorinated pesticide residues with consistent recoveries. Inorganic
adsorbents offer one advantage over organic adsorbents in that the organic
substrate is less likely to be a source of organic interference.
4.2.1.3. Carbon Adsorbents
Carbon adsorbents are relatively nonpolar compared to the inorganic
adsorbents; thus, water adsorption is a less significant problem.
However, water adsorbtion may still prevent analysis in certain
applications. The carbon based materials tend to exhibit much stronger
adsorption properties than organic polymeric adsorbents, hence allowing
efficient collection of highly volatile materials such as vinyl chloride,
benzene, and toluene. However, the strong adsorption on carbon adsorbents
can be a disadvantage in cases where recovery by thermal desorption of
less volatile materials such as benzene or toluene is desired because of
the excessive temperatures required (e.g. 400* C).
There are a variety of carbon based adsorbents available with widely
varying adsorption properties. The commonly available classes of carbon
adsorbents include:
• Various types of conventional activated carbons.
• Carbon molecular sieves.
• Carbonaceous polymeric adsorbents.
Conventional activated carbons have a microporous structure which leads to
difficulty in recovering adsorbed materials; therefore this material is
rarely used in trace organic sampling.
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Carbon molecular sieves have a spherical, macroporous structure which
theoretically leads to better recovery of adsorbed materials, relative to
conventional activated carbons. These materials are sold under various
trade names (e.g. Spherocarb, Carbosphere, Carbosieve, and Ambersorb
XE-347) and have been used to a limited extent for the determination of
volatile organics such as vinyl chloride and methylene chloride (31).
TOAP monitoring data using carbon molecular sieves have been inconsistent,
and leading investigators are diverging from this sampling approach.
Carbonaceous polymeric adsorbents are described as hard, non-dusting
spheres with properties intermediate between activated carbon and organic
polymeric adsorbents. These materials are available from Rohm and Haas
Chemical Company under the trade name "Ambersorb" (XE-340, XE-347,
XE-348). Of the three materials, Ambersorb 347 is classified as a carbon
molecular sieve; XE-348 is most similar to activated carbon, and XE-340 is
most similar to organic polymeric adsorbents. XE-340 appears to have some
attractive features in terms of trace organic sampling and has been shown
to be useful for volatile compounds in the C. to Cg boiling point
range (32,33), a volatility range not covered by organic polymeric
adsorbents such as Tenax.
Carbon hollow tubes (CHT's) have been introduced as pre-concentrators
of atmospheric organic compounds (34) . They have been shown to be stable
for compounds with boiling points between 90*C and 235'C. The design
eliminates many problems associated with other materials. The adsorbent
surface is shallow and allows for rapid thermal desorption, perhaps
minimizing decomposition of trapped analytes. Also, rapid desorption
makes direct interfacing with GC feasible. Finally, the open tubular
design provides a high degree of separation of gases and particles.
In selecting particular adsorbent materials for sampling trace
organics, one must consider both the capture process and the compound
recovery process. Generally, either thermal desorption or solvent
extraction is employed to recover the analytes. Thermal desorption is
most useful for compounds having boiling points of less than 300' C,
whereas solvent extraction is most useful for compounds boiling above 150*
C. The decision on which methodology to use for those compounds which
boil between 150* and 300*C should be based on characteristics of the
compounds within this range. The actual upper bonding point limit for
thermal desorption is also dependent on the temperature limitations of the
sorbent used for sampling.
Thermal desorption is an attractive approach in many cases because the
entire sample can be introduced onto the analytical instrument. This can
be a disadvantage, however, because multiple analyses using the same
sample are difficult to perform. Should the analysis equipment fail or
the working range of the procedure be exceeded, no data can normally be
recovered. For this reason multiple samples are typically collected at
each sampling site to minimize the impact associated with the loss of a
sample during analysis. Since levels of organic contamination are often
very low, these disadvantages are less significant than the enhancement of
detection limit. Furthermore, the thermal desorption process is more
readily automated and does not require disassembly of the sampling
cartridge prior to analysis.
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When solvent extraction is used, only a small fraction of the extract
(e.g. 1-10 percent) can be introduced. This advantage allows adjustment
of the concentration of analyte introduced into the analytical system
(i.e. the analyte remains within the working range of the instrument) and
also allows for replicate analysis of a sample, which can be an important
consideration. Use of solvent extraction also avoids the problem of
thermal decomposition of labile compounds during the analysis step.
The use of supercritical fluid extraction with CO2 of Tenax-GC
sorbent traps to yield rapid and quantitative recovery of PAH's has been
demonstrated for compounds with molecular weights as high as 300 AMU at
low temperatures (45* C). This technique may provide a viable alternative
to liquid solvent extraction and thermal desorption.
Although a wide variety of approaches employing solid adsorbents may
be feasible for any given monitoring situation, the following summary
offers useful guidance for generalized cases:
• Thermal desorption of organic polymeric adsorbents (especially
Tenax GC) is useful for compounds boiling between 60'-300* C,
exclusive of highly polar compounds such as methanol and acetone.
• Solvent extraction of organic polymeric adsorbents (especially
XAD-2) is most useful for compounds boiling above 150* C and can
in some cases be extended to more volatile compounds, depending
on solvent and mode of concentration.
• Thermal desorption of carbon adsorbents (especially carbon
molecular sieves or Ambersorb XE-340 and CHT's) may be useful for
volatile compounds boiling in the range 0*-70* C, including vinyl
chloride. However, the high temperatures (350'-400') required
for desorption from these media may lead to degradation of many
labile compounds. If medium or high concentrations of compounds
are of concern, solvent desorption of carbon adsorbents may be a
useful alternative.
• Supercritical fluid extraction of solid adsorbent (Tenax GC) by
CC>2 is a useful alternative for recovery of PAH's at low
temperatures. The potential for class selective extractions and
direct coupling with on-column cryogenic trapping in a gas
chromatographic column exists.
• Inorganic adsorbents such as silica gel or alumina are not
generally useful for ambient air monitoring, because of the water
deactivation problem. However, when high concentrations of polar
organics are a concern, they may be the method of choice, since
they have high affinities for these materials, which can usually
be recovered by solvent extraction.
4.2.2. Nhol* Air Collection
Collection of whole air samples by means of evacuated glass bulbs,
stainless steel canisters, Tedlar bags, or other devices is probably
the simplest sampling approach and can be useful in many situations. Grab
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sampling advantages have been discussed by Krasnec (36). One major
concern with this type of sampling is the loss of analyte due to
adsorption and permeation through the container walls. At very high
concentrations (e.g. several ppm) condensation may also be a problem.
Consequently, this approach has been utilized primarily for highly stable
compounds such as hydrocarbons and chlorinated hydrocarbons with boiling
points less than 150* C. Long-term storage of certain compounds usually
results in loss of analytes.
4.2.2.1. Glass Sampling Bulbs
Containers for whole air sampling can be categorized as rigid or
non-rigid devices. Evacuated glass bulbs are rigid devices that have been
used extensively in the field. They are convenient, easy to handle, and
relatively inert sample containers. Their main disadvantage is their
susceptibility to breakage, especially during transportation.
4.2.2.2. Gas Sampling Bags
Bag collection of airborne analytes is commonly employed. Trade names
include Tedlar, Teflon, Mylar, and Saran. Generally bag sampling is used
for short-term storage and analysis occurring within a few hours. Leakage
and/or permeation of materials into and out of the bag is a common
problem, and trace level concentrations will not allow for such losses.
On the other hand, bags are advantageous for being lightweight and easily
transportable. Reuse of gas sampling bags is not recommended when
sampling for very low levels of organics. When bags are reused they must
be rigorously cleaned by multiple evacuations and fillings. The
cleanliness of each bag should then be established before use. Even new
bags can be a source of contamination and their cleanliness should be
established by blank analysis prior to use. The standard of cleanliness
will be determined by the concentration of the analyte to be measured and
the analytical method.
4.2.2.3. SunmaR Polish«d Canisters
Stainless steel canisters which have been passivated by deposition of
Tj
a pure chrome-nicked oxide on the interior surface (Summa polishing
process) offer many advantages for VOC and SVOC sampling.
The canisters are not subject to sample permeation or photo-induced
chemical effects, and they can be reused after a simple cleanup
procedure. The sample integrity of trace level organic compounds stored
in Summa polished canisters has been summarized (35) for storage periods
up to 30 days. A study also revealed that canisters which had been
subject to many sampling/cleaning cycles performed better than new
canisters, which showed trace level contamination on an initial blank
test.
Side-by-side comparison of sampling with Tenax GC and passivated
canisters has also been conducted (16), yielding satisfactory results.
Canister sampling offers a distinct advantage over sorbent sampling in
that artifact formation, high blank, and background values, and sorbent
capacity problems are eliminated. Additionally, because a whole air
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sample is collected into the canister, this sampling procedure is
applicable to compounds with a much broader range of boiling points and
vapor pressure.
A prototype sampler system to collect and transfer VOC's from ambient
air has been designed (38), which uses Tenax to adsorb and desorb organic
compounds and then transfer them to storage canisters. Sample enrichment
(15- to 35-fold) is achieved by utilizing less volume flow in the
desorption step than in the adsorption process. This demonstrates the
feasibility of a non-cryogenic pre-concentration technique that can be
used with stainless steel canisters and that still provides adequate
sample enrichment. Obviously, limitations of this procedure are still
those associated with the use of solid sorbents.
Pre-evacuated canisters are used for sampling in one of two ways. For
subatmospheric sampling, an evacuated canister is used to collect a sample
until the pressure of the canister approaches atmospheric pressure. For
pressurized sampling, gas is pumped into an evacuated canister until the
pressure in the canister reaches 15-30 psig. The method which employs
canisters (TO-14) has been most extensively documented using pressurized
sampling techniques.
4.2.3. Cryogenic Trapping
The collection of atmospheric organics by condensation in a cryogenic
trap is an attractive alternative to adsorption or whole air collection.
The primary advantages of this technique include:
• A wide range of organic materials can be collected.
• Contamination, problems with adsorbents and other collection media
are avoided.
* The sample is immediately available for analysis (direct
interfacing with GC possible).
• Consistent recoveries are generally obtained.
However, an important limitation of the technique is condensation of
large quantities of moisture and lesser amounts of certain reactive gases
(S02, NOX, etc.)
Cryogenic sampling can be accomplished in a variety of ways, depending
on the desired detection limit and compounds of interest. The important
parameters to be specified include:
• Choice of cryogen.
• Trap design.
* Method of sample recovery.
• Method of analysis.
Useful cryogens include liquid oxygen, liquid argon, dry ice-solvent
systems, and ice water. Liquid nitrogen is not an acceptable cryogen
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because large quantities of air will condense. Ice water is not cold
enough for collecting organica in ambient air, except for relatively
nonvolatile compounds. Dry ice-solvent systems should be employed with
caution because of the high probability of contaminating the sample with
relatively large quantities of solvent. Liquid oxygen or argon appear to
be the most generally applicable cryogens, although the safety hazards
associated with liquid oxygen make its use less attractive.
The design of a suitable sample trap is extremely important in
cryogenic sampling. One must ensure that the air residence time in the
trap during sampling is great enough to allow for cooling of the gas
stream and condensation of the analyte of interest. The trap material
must be able to withstand the wide temperature range involved in the
sample process. The trap design must also be appropriate for the sample
recovery step, allowing efficient recovery without loss or contamination
of the sample. For highly volatile materials, the inclusion of an
adsorption medium such as silica gel may be necessary to obtain
satisfactory collection efficiency.
Cryogenically collected samples can be recovered either by flash
evaporation into an analytical instrument or by solvent flushing of the
trap. The former approach is preferable in most cases because it allows
more sensitive detection and avoids contamination (e.g. from solvents).
However, the solvent flushing approach can be accomplished with less
elaborate equipment in the field and may be preferable for the analysis of
higher concentrations of material.
A new technique has been developed that resolves some of the problems
associated with both cryogenic and porous polymer sampling techniques and
utilizes the desirable characteristics of each. This method involves
cryogenic concentration followed by volatilization and transfer in an
inert gas stream to Tenax tubes to avoid analyte breakthrough and
artifact formation problems. The technique should be applicable for
determination of VOC's with a wide range of volatiles.
A simplified cryogenic pre-concentration, direct flame ionization
detection (PDFID) method for non-methane organic compounds in ambient air
(Method TO-12) has been developed and recommended for use by state and
local air pollution control agencies in the development of their ozone
control plans (40).
A cryogenic sampling approach for monitoring trace organics in ambient
air has been described (39), which involves the use of a small (3 mm ID)
trap packed with silanized glass beads and held at liquid argon or liquid
oxygen temperature. A 50-500 ml volume of ambient air is drawn through
the trap by means of an evacuated tank/manometer assembly as the pumping
and volume measurement system. The trap is directly connected to a
six-port stainless steel valve, and following sampling collection the
condensed material is flash evaporated onto a capillary GC'FID system for
analysis. Detection limits on the order of 0.5 to 1 ppbv can be achieved
using this approach. Even lower detection limits can be achieved for
certain compounds by the use of selective detectors such as an electron
capture detector (BCD). This technique requires transport of the
analytical system to the monitoring site or collection of a whole air
sample in an evacuated cylinder, with subsequent laboratory analysis. For
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higher boiling compounds adsorption onto container walls may represent a
significant problem if the latter approach is employed.
4.2.4. Impinger Collection
Impinger or "bubbler" collection involves passing the gaseous sample
through a liquid adsorbing solution and "scrubbing" out the species of
interest. Aldehydes and ketones may be sampled with a liquid impinger
system using DNPH reagent for subsequent HPLC analysis (Method TO-5). All
glassware should be thoroughly rinsed with methanol and oven dried before
use. Sodium hydroxide liquid impinger collection for creosol and phenol
is used in EPA Method TO-8. With the exception of Methods TO-5 and TO-8,
impinger based sampling systems have limited applications to TOAP
monitoring programs because large volumes of air must be sampled,
resulting in solvent evaporation, to achieve required detection limits.
4.2.5. Derivmtirmtion Techniques
With the exception of canister based sampling systems a fundamental
limitation of the various sampling techniques discussed so far is the
decomposition of reactive compounds during sample collection or
transport. Two approaches can be used to circumvent this problem. One
obvious approach is to use a direct analysis technique in which the
analyte concentration is determined without physically isolating the air
sample (e.g. total hydrocarbon analysis).
An alternate approach, discussed in this section, is to stabilize
reactive compounds by combining them with a derivatizing reagent during
the sampling process. In many cases derivatizing reagents can be chosen
which not only stabilize the compound but enhance its detectability. Such
schemes are available for determining formaldehyde (TO-11), aldehydes
(TO-5), phosgene (TO-6), and certain other reactive compounds.
In certain cases, such as the 4-aminoantipyrene method for phenols and
the ninhydrin method for amines, the derivatization step is used solely to
enhance detectability and may be done in the laboratory rather than the
field. In this section, only derivatization techniques for field use are
considered. Derivatization schemes for specific compounds or compound
classes are discussed later.
Derivatization reagents for field use can be held either in an
impinger or on a solid adsorbent. The impinger approach is most
convenient because reagents can be prepared and stored as liquid
solutions, whereas solid adsorbent systems require more elaborate
preparation and storage procedures. However, the solid adsorbent approach
is more sensitive in many cases because larger volumes of air can be
sampled. A study of both these approaches for aldehyde derivatization has
been reported (42) . In this particular example, the impinger approach
appears most useful because it provides adequate sensitivity and is less
susceptible to humidity effects on analyte recovery.
All derivatization techniques require the use of high purity
reagents. Normally, fresh stocks of reagent should be prepared for each
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sampling episode or more frequently if degradation or contamination
(through passive diffusion of materials into the reagent) is a problem.
One must be aware of potential interference in the method, especially from
reactive gases present at high levels in the sample (e.g. water, SC>2,
NO2' ^3' etc-) and must incorporate quality control procedures to
ensure such interferences are not a problem.
4.2.6. Paaaiva Samplers
In recent years, the development of passive sampling devices (PSD) has
drawn much attention. These devices sample by means of diffusion or
permeation rather than by means of a pump. They have been shown to be
simple, convenient, inexpensive, and valid alternatives for assessing
time-weighted average concentrations for personal exposure monitoring
(43) .
Analysis of adsorbed compound is accomplished by thermal desorption
and chromatographic separation. Specificity can be introduced into a
passive sampling technique by a suitable choice of adsorbent substrate
(44). A passive sampler using a DNPH-coated glass fiber filter has been
developed for formaldehyde (45). A comparison of recoveries of
trichloroethylene from active charcoal tubes and a thermally-desorbable
personal monitor revealed the passive sampler to exhibit better recovery
efficiency (46). A personal dosimeter based on molecular diffusion and
direct detection by toom temperature phosphorescence has been developed to
monitor vapors of polynuclear aromatics (47).
4.2.7. Direct Analyst*
Probably one of the most attractive sampling and analysis approaches
is that of direct measurement, requiring no sample collection, storage,
and transfer. Methods for organic compounds fitting this definition
include colorimetric, spectroscopic, ionization and other related
techniques. Specific techniques are discussed in detail in the section on
field screening techniques in Section 5. One major limitation of these
techniques is their lack of sensitivity, because the sample is not
preconcentrated.
Problems such as analyte degradation and adsorptive losses are not a
factor in direct analysis because the sample is immediately analyzed in
the field. Delivery of the sample to the analytical device is usually
through an inert and heated sample line (Teflon or passivated stainless
steel). A heated filter is typically placed upstream to collect
interfering particulate matter. Carbon monoxide and water present in the
atmosphere may sometimes cause interference but can be eliminated by use
of an adsorber/collection trap upstream from the analytical device.
4.3. METHODS FOR PARTICUIATS AND PARTICLE BOUND COMPONENTS
Many SVOC's and polar organic compounds in ambient air are associated
with solid particulate matter dispersed in the atmosphere. These organic
compounds may adsorb or condense to different degrees and exist in a
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complex, dynamic, solid-vapor equilibrium with particulate matter.
Sampling for trace organics in air almost always alters the solid-vapor
interphase, making determination and adequate representation of the
ambient condition difficult. Particulate collection is usually
accomplished by filtration, centrifugation, impaction, or electrostatic
precipitation, all effective for collecting solid matter down to sizes in
the micrometer range. During the capture process certain components may
be driven by air flow through the sampling system from the particle-bound
phase to the gas phase and some of the gaseous components may adsorb or
react on the filter media. Additional interference may result from
artifact formation or photochemically induced changes when organic and
inorganic components are concentrated on sampling media. Consequently the
particle-bound concentration of an analyte is an operationally defined
term and must be chosen to satisfy the program objectives. These
considerations will be conditional upon the organic species of interest
and their physical characteristics.
One aspect of particle sampling for trace organic analysis is the need
for a gas phase collection device (e.g. adsorbent, impinger, etc.)
downstream from the particulate capturing device. Analysis of both
collection media will be necessary for total analyte concentration but may
not reflect the actual phase distribution at ambient conditions. Gas and
solid phase distribution will be discussed in more detail in the following
section, and a good coverage of sampling considerations for particulate
matter is given in Stern's book (48).
4.3.1. nitration
The most common method for collecting particulate matter is
filtration, due to its low cost and simplicity. A wide range of filter
media with diverse permeation characteristics is available. If only the
total quantity of organic analyte is of interest, the filter may be
operated at an elevated temperature (above 150* C) to vaporize the
material so that the analytes can be collected in the gas phase, hence
simplifying the analysis requirements. This can however, result in
analyte loss via degradation or interferent production via artifact
formation. If the particle-bound concentration is to be determined, the
sampling system should be maintained at ambient temperature conditions,
and the sample volume should be minimized to reduce volatilization.
Unfortunately, the low levels of ambient particulate matter usually
require the collection of several hundred cubic meters of air (e.g. with a
high volume sampler). Under these conditions even relatively nonvolatile
compounds (e.g. three- and four-ring PAH's) may be lost to some extent.
Chemical transformation of some adsorbed material through reactions with
atmospheric inorganic gases (e.g. NOX, 302, and Og) can also be a
problem in certain situations.
The most commonly used filter media for sampling organics are:
• Cellulose fiber.
e Glass or quartz fiber.
e Mixed fiber filters (glass, cellulose, asbestos, etc.)
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• Membrane filters (cellulose esters, Teflon, Nylon, etc.)
• Nucleopore filters.
Cellulose fiber filters do not have uniform pore sizes and tend to
have unpredictable collection efficiencies for fine particles; however,
they have high mechanical strength and are inexpensive. For air sampling,
Whatman No. 41 is a commonly used cellulose filter. Glass or quartz fiber
filters have the advantages of withstanding higher temperature, having
reduced hygroscopicity, and yielding better collection efficiencies. They
are used extensively in high volume samplers. Disadvantages of glass and
quartz filters, compared to cellulose filters, include reduced mechanical
strength due to fragility, adsorptive loss of organics, and cost. Mixed
fiber filters are used primarily for air cleaning, due to their high
collection efficiency. They are typically not used for analysis because
of the difficulty associated with complete recovery of samples for
analysis. They can be appropriate for gravimetric methods not requiring
separation of sample from the filter, as well as for collection of
radioactive particles for analysis. Membrane and nucleopore filters have
a well defined pore size distribution and have very predictable sampling
properties. However, these filters are expensive, have a relatively high
resistance to flow, and have a rather low sampling capacity. Many
membrane filters are soluble in organic solvents, which could be an
advantage or disadvantage in recovery, depending on the analytes of
interest.
4.3.2. Centrifugal Collection and Impaction
Most particle sampling approaches other than filtration are employed
for the purpose of size classification of particulate matter. The primary
reason for collecting size fractionated particle samples is to distinguish
respirable particles (<10 urn diameter) from larger particles. Although
the most common objective is to compare particle mass in each size range,
the chemical composition is of interest in certain cases. Methods for
collecting size fractionated particulate samples generally rely on the
difference in momentum (mass times velocity) of the various size
particles. Devices operating on this principle include cyclones
(centrifugal collectors) and impactors. Both of these devices collect
particles of a specific size range, based on the design of the apparatus.
Cyclones tend to have a rather broad size cut, whereas impactors have a
much sharper size cut. These devices are useful for particles greater
than approximately 1 urn in diameter and are often used as the basis for
"respirable" particle determinations.
A device has been developed by EPA for sampling large volumes of size
fractionated ambient particulate matter (51). This device called the
"Megavolume Respirable Particulate Sampler" consists of a cascade impactor
followed by an electrostatic precipitator. The absence of a filter
reduces the pressure drop and allows higher sample flow rates (up to 15
m /minute). Particles of greater than 20 urn and <1.7 um are collected.
This device has the disadvantage of being very bulky (4 ft x 2 ft x 2 ft),
and the effect of electrostatic precipitation on chemical composition has
not been thoroughly investigated.
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4.3.3. Electrostatic Precipitation
Electrostatic precipitation (ESP) method is capable of capturing
particles greater than 0.1 nun and serves as an alternative to filtration
for the collection of fine particles. A high electrical field (12-45 kv)
is maintained between a series of parallel plates. Particles entering the
field become charged by ions present in the gas phase and are attracted to
the plates.
This sampling, compared to filtration, approach allows large sample
volumes to be collected, due to the lower pressure drop. However, the
effect of the corona discharge and associated reactive species (e.g.
ozone) generated in the ESP on organic chemical composition is of concern
and has not been thoroughly investigated. Removal of collected particles
from the electrodes is accomplished by rapping or vibration, which seldom
results in quantitative recovery. For these reasons, collection of
particulate matter for trace analysis of toxic organic constituents by ESP
should be thoroughly compared with other available methods of collection.
4.4. GAS AMD SOLID PHASE DISTRIBUTION ANALYSIS
Recently much attention and work has been focused on investigating the
distribution of semi-volatile organic compounds (PAH, PCS, pesticides,
etc.) between the vapor phase and the particle-bound, condensed phase as
they exist at ambient conditions. The knowledge of gas and solid phase
distribution of air pollutant is important for understanding atmospheric
transport, residence time, and fate of these air toxics, as well as in
development of sampling methods and designing pollution control systems.
Conventional filter and adsorbent backup traps have been subjected to
volatilization transfers and are believed to yield erroneous data
concerning phase distribution. Denuder-based gas/particle sampling
systems have been designed and evaluated for more effective collection of
vapor/solid distributed compounds in air. The denuder sampling system is
similar to the standard EPA PS-1 sampler with the incorporation of a
multiple tube denuder ahead of the filter.
Field evaluations of a denuder sampler in conjunction with a PS-1
sampler yield total concentration, fractional phase distribution, and
artifact formation data for target compounds (52). The first results of
field investigation representing direct phase distribution measurements on
SVOC's conducted by EMSL/RTP and Battelle Columbus Division demonstrated
the possibility of separate collection of both gas and solid phases with a
denuder sampler, while maintaining data integrity. However, the system
used was a low-volume sampler sensitive only to major PAH compounds in
air. Subsequently, a compact, high volume multiple annular denuder
sampler has been designed and laboratory tested to yield 95% vapor removal
efficiency and operating flow rates up to 200 L/min with no measurable
loss of particle transmission. It also has direct thermal recovery
potential. Two such systems are under development and evaluation (53).
An experimental system for investigating vapor-particle partitioning
of trace organic pollutants has been designed utilizing a stainless steel
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mixing chamber to generate vapor-phase SVOC under high-volume sampling
conditions (54). Vapor-particle (V/P) distribution for selected compounds
are estimated in the laboratory using the apparent partition coefficient
A[TSP]/F, where A and F are the adsorbent and filter-retained
concentration (ng/m ) and [T3P] is the total suspended particle
concentration (mg/m ).
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SECTION 5
OVXKVIKM OF ANALYTICAL METHODS
This section presents a general description of some analytical methods
used in determining ambient atmospheric concentrations of organic
compounds. The first subsection discusses physical and chemical
properties of concern that govern the applicability of various analytical
techniques. The next subsection presents field screening techniques,
which are relatively inexpensive and are rapidly performed in the field.
The third subsection covers laboratory screening techniques that are more
precise at identifying classes of compounds based on functional groups
present. In the final subsection compound specific methods such as gas
chromatography (GC), high performance liquid chromatography (HPLC), and
mass spectrometry (MS) techniques are presented. No one analytical
technique will be ideal for all organic compounds, and thorough
consideration of the species of interest and program objectives should be
conducted before applying any approach. Section 6 provides more detailed,
specific applications for particular organic compounds of interest.
5.1. CHEMICAL AND PHYSICAL PROPERTIES
In many respects the chemical and physical properties of concern in
sampling method selection are of similar importance in the selection of
analytical methods. However, important differences in emphasis exist and
must be recognized. Properties of primary concern include:
• Physical state (gaseous or adsorbed)
• Volatility
• Polarity
• Solubility
• Ionic character
• Reactivity
• Thermal stability
• Chemical composition
One of the most important properties governing the selection of
analytical methods is volatility. Sample preparation procedures, whereby
the analytes of interest are delivered from the sample matrix into a form
suitable for analysis, generally involve either solvent extraction/
concentration or thermal desorption/cold trapping approaches. Highly
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volatile compounds (e.g. boiling points below 100* C) cannot be readily
analyzed by solvent extraction/concentration approaches because of losses
during the concentration process and interference from the solvent to the
analytical system. On the other hand, compounds with boiling points above
250* C usually are not candidates for the thermal desorption approach.
Volatility, polarity, and thermal stability must also be considered in
the selection of determinative techniques, because gas chromatographic
(GC) procedures are not suitable for non-volatile, highly polar, or
thermally labile compounds unless special precautions are taken.
Generally, polarity and thermal stability are limiting factors for GC
determination of organic compounds in ambient air, since these compounds
tend to be sufficiently volatile.
Ionic character, water solubility, and reactivity are primarily of
concern during sample preparation procedures involving liquid extraction
or adsorption chromatography and for determinative procedures such as high
performance liquid chromatography (HPLC). lonizable compounds (acids or
bases) require careful control of pH when aqueous systems are employed.
Generally, ionizable compounds are converted to their nonionized forms
by adjusting the pH two to three units below the pKa for acidic compounds
and two to three units above the pKb for basic compounds. Highly reactive
compounds may present problems in the sample preparation procedure through
reaction with solvents or adsorption chromatography supports. Phosgene,
for example, reacts readily with water; thus water must be carefully
excluded from the sample preparation scheme.
Chemical composition is important in the selection of determinative
techniques. Whenever possible, a selective detection system for the
compound class should be used. Suitable selective detection systems for
GC analysis are available for halogens, as well as nitrogen-, sulfur-, and
phosphorous-containing compounds. HPLC analysis is appropriate if UV
absorbing (usually aromatic), fluorescent, or electrochemically active
(e.g. phenol, aromatic amines) functional groups are present in the
molecule.
The chemical and physical properties of major compounds (other than
those of interest) present in the sample should be considered, since these
compounds represent potential interferences. Whenever possible,
analytical and sampling techniques should take advantage of differences in
properties between compounds of interest and other compounds, to minimize
interference in the methods.
5.2. riELD SCREENING TECHNIQUES
The term "screening technique" can imply different approaches to
different people, and therefore an introductory definition is necessary.
In this document "field screening techniques" will refer to techniques
which can be accomplished rapidly and with relatively inexpensive
instrumentation in the field. This definition excludes sampling and
analysis approaches which involve conventional sampling techniques and
subsequent application of group specific methods in the laboratory. This
definition also excludes devices such as mobile mass spectrometers (MS)
and triple quadrupole MS/MS systems because these systems are relatively
expensive.
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This limited definition for "screening technique" should not be viewed
as an implication that -the excluded sampling and analysis approaches are
not useful. Indeed, many circumstances arise where such techniques are
extremely useful and should be employed in preference to (or in addition
to) the other techniques described in this document. The purpose in
limiting the definition of "screening technique" in this way is to present
a discussion of alternative approaches which can be used to evaluate
whether or not TOAPs are present at a particular site. This evaluation
should be accomplished rapidly (e.g. be field operable) and with a minimum
of expense (since a multitude of sites may need to be investigated). Such
techniques need not be selective for a particular compound but should be
capable of distinguishing organic components (e.g. methane) typically
found in uncontaminated air from hazardous substances (e.g. chlorinated
and aromatic hydrocarbons). If possible, the technique should indicate
the class of organic compound present so that subsequent detailed
investigations of a. site can be directed toward a limited set of target
compounds, thereby minimizing the cost and time associated with detailed
investigations.
For the purpose of this document the available screening approaches
can be broadly subdivided into the following subsections:
• Colorimetric methods.
• Spectroscopic devices.
• lonization devices (with or without gas chromatographic
separation).
• Photometric devices (with or without gas chromatographic
separation).
• Passive monitors or dosimeters.
One must be aware that most screening devices have been designed to
meet monitoring needs of the industrial hygiene community, among whom
part per million levels are usually of concern. Consequently, if one must
detect part per billion levels in ambient air, many of these devices will
not be sufficiently sensitive.
In the following subsections the operating principles, advantages, and
limitations of the various screening approaches are discussed.
5.2.1. ColoriiMtrlc Detection
Colorimetric devices involve drawing the air sample through an
adsorbent or solution containing a reagent which reacts with the
compound(s) of interest to yield a colored material. The degree of color
change is proportional to the concentration of the adsorbed analyte. The
specificity of such methods is highly dependent on the compound being
monitored, and one must be cognizant of the fact that some airborne
components may create a positive or negative interference in the method.
Humidity, temperature, and sample flow rate can affect the results
obtained, and consequently these variables must be known and controlled
whenever possible.
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The most common type of colorimetric device use for air monitoring is
the gas detection tube. Tubes of this type are available for long-term,
time weighted average exposure and short-term grab sampling. These tubes
are also used extensively for personal exposure monitoring. Some sample
passively and can be worn on the outer clothing of workers. Others draw a
precise sample with the use of a hand-held volumetric pump attached to the
tube.
The concentration of the substance being monitored is determined by
one of two methods: In one system the entire tube changes color; the
extent of color change is then compared to a standard color chart. The
second method draws the sample into the tube, and the reagent stains over
a segment of the length of the tube. The length of the stain is
concentration dependent. Tubes of this type have calibrated scale
markings for direct measurement recording.
The procedures for use are fairly simple, and manufacturers provide
detailed information on the specifics of the reactions involved. Tubes
are refrigerated until use, then allowed to reach ambient temperature.
Reagent expiration dates should be observed, and a system leak check
performed before sampling.
Detection limits for organic compounds being tested in the detector
tube are generally 0.1 ppmv or higher and often will not be adequate for
monitoring ambient levels directly. However, this level of sensitivity
may be sufficient for monitoring air in the vicinity of hazardous waste
dumps, chemical spill sites, and similar sources where a rapid,
inexpensive, qualitative assessment is desirable.
Colorimetric devices other than gas detection tubes are available.
One such device uses an integrated liquid pumping system to trap the
component of interest, react it with a color developing reagent, and
measure the absorbance continuously. This device, while suffering from
the same sensitivity and selectivity limitations as the detector tube,
offers a continuous monitoring capability which can be useful for rapidly
surveying an area for sources of contamination. Currently, this device
can detect formaldehyde, aerylonitrile, and a variety of inorganic species
with detection limits of 0.05 to 0.5 ppmv. However, this basic system
could conceivably be applicable to many more compounds, by using alternate
color developing reagents.
Another colorimetric approach involves impregnating a continuous paper
tape reel with a color reagent and passing air through the tape. The tape
is slowly driven from the air sampling region to an optical detector which
measures the absorbency at a specified wavelength. Currently, devices for
the detection of isocyanates, dinitrotoluene, phosgene, and a variety of
inorganic species are available. Detection limits of a few ppbv are
achievable for selected compounds (e.g. toluene, diisocyanate), although
the detection limits and selectivity of this approach are generally
similar to the other colorimetric approaches. Nevertheless, this approach
can be used for continual area monitoring to observe temporal changes in
concentration of selected components.
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5.2.2. Spectroscopic Devices
Although a wide variety of spectroscopic techniques (e.g. infrared
spectroscopy [IR], ultraviolet adsorption [UV], fluorescence, etc.) could
potentially be applied to air monitoring, only IR has been employed to a
significant extent. UV spectroscopy is too nonspecific to be of any real
value, and fluorescence detection is applicable only to a few selected
compounds, although either of these techniques could be useful in selected
cases.
Infrared spectroscopy is a powerful analytical tool because of its
specificity, sensitivity, versatility, speed, and simplicity. Because
every compound has its own individual characteristic spectra, quantitative
and qualitative identification of compounds and compound classes based on
adsorption bands exhibited by their functional groups can be
accomplished. Analysis of integrated samples as well as continuous
monitoring can be performed. Several variable wavelength and path length
IR spectrophotometers are available for both field and laboratory use.
Analytical parameters (reference and analysis filter wavelength) for
monitoring approximately 100 organic compounds are available. IR spectra
libraries are available for several thousand organic compounds.
Major limitations of the IR method are: (1) many inorganic gases
(e.g. H~0, CO, NO, etc.) are also absorbed at wavelength that may
interfere with analysis; (2) IR absorbance is not as strong as UV
absorbance, hence the poor detection limits (1-10 ppmv). The latter are
minimized by employing long, folded-path optical cells (20 meters).
Microcomputer control of commercial IR screening devices has partially
overcome the first limitation by allowing automated correction for
interference. Drying tubes, ascarite traps, and the use of zero gas also
reduce interference from moisture, carbon dioxide, and other inorganic
gases present in ambient air.
5.2.3. lonization De-vie*•
lonization techniques operate on the principle of subjecting the
analyte to a high energy source, with subsequent detection of the ionized
species by collection at an appropriate polarized electrode. The most
widely used applications of this type are (a) flame ionization detection
(FID), (b) photoionization detection (FID), and (c) electron capture
detection (BCD). Each of these can be used in a "stand alone" mode for
total organic measurements or can be coupled with a gas chromatograph to
provide greater specificity.
Flame ionization detection (FID) - As its name implies, FID involves
the ionization of organic components of the atmosphere in a flame. A
hydrogen/air flame is used because the concentrations of ions within it
are low. The FID responds to virtually all organic compounds, that is,
compounds which contain carbon-hydrogen or carbon-carbon bonds. The
introduction of organic compounds into the flame results in formation of
ions, which reduces the electrical resistance of the flame. This change
in resistance is detected by electrodes and is proportional to the
hydrocarbon concentration. Flame ionization detectors are used in most of
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the commercially available "total hydrocarbon" and "non-methane
hydrocarbon" analyzers. Typical detection limits for such devices are
about 0.5 ppmv (as carbon). Another appealing feature of FID is its wide
range of linearity. A. description of sensitivity variations of two
commercial FID's has been presented (52).
In addition to the commercially available total hydrocarbon monitors,
several portable GC/FID systems are available. These GC/FID systems
provide qualitative as well as quantitative field analysis. When coupled
with a GC, FID effectively identifies specific compounds of interest which
are separated on the GC column from methane and other ubiquitous organic
compounds.
In addition some of these GC systems can utilize alternate detectors
to provide even greater qualitative information, as well as better
sensitivity for selected groups of compounds.
Photoionization detection (PIP) - can be used to measure a wide range
of toxic compounds. PID involves subjecting the gas phase compounds to a
high-intensity beam of UV radiation of a particular energy. Excitation of
the gas molecule by UV energy results in the formation of a positive ion
and a free electron. The degree of ionization is dependent upon the
ionization potential characteristic for each compound. The ions are
collected on positive and negative electrodes, resulting in a flow of
current proportional to the concentration of the ionized species. The
convenience of this method is the fact that natural components of ambient
air (oxygen, nitrogen, carbon dioxide, and water) have much higher
ionization potentials and are thus not detected.
Because the ionization potential of a particular compound must be less
than the radiation energy, compounds having high ionization potentials
will be less easily detected than those compounds of lower ones
Consequently, the choice of lamp energy will have a profound effect on
detector specificity. This aspect of PID detection is attractive from the
standpoint that use of a higher energy lamp will provide a relatively
nonselective, less sensitive detector, whereas a lower energy lamp will
yield a selective detector which can sensitively detect certain readily
ionized compounds (e.g. aromatic hydrocarbons) but will not detect
aliphatic hydrocarbons. While more species can be detected with high
energy lamps, the reduced life expectancy and lowered sensitivity limit
their usefulness.
Several PID devices and a variety of lamp energies ranging from 9.5 to
11.7 eV are available. In general, the ionization potential for important
groups of organic compounds increases in this order: aromatics
-------
The sensitivity of PID is considerably greater (100 ppbv or better)
than that of FID, and several manufacturers produce field-portable GC/PID
systems. These devices have advantages similar to the GC/FID system, in
that qualitative as well as quantitative data are obtained. However,
while the PID system is generally more sensitive than FID, the PID system
does not give uniform response from compound to compound. Hence, the
system must be calibrated for each specific analyte in order to yield
quantitative data.
Electron capture detection (BCD) - In this technique the gas sample is
introduced into an electron cloud produced by a radioactive source
(usually from H or Ni). When an electron-capturing species (such
as halogenated or nitrogenated organic compounds) is subject to an
electron source, a decrease in the standing current gives a response which
is a measurement of the analyte's concentration and electron capturing
efficiency. Unfortunately, response varies widely from compound to
compound and requires specific calibration for every compound analyzed.
The detector can be calibrated at standard atmospheres of the material to
be monitored and has a detection sensitivity of about 10 pg.
ECD's can be used for leak seeking of trace organics and provide
adequate quantitative data. Instruments are used for continuous
monitoring and are also coupled with gas chromatography. "Stand alone"
BCD detectors are not as applicable in selecting organics as FID and PID.
They are also sensitive to inorganic gases and particles and can only be
used in a controlled gas stream using N2 or argon/methane gas carriers.
Response time for BCD is about one second for continuous monitoring and
fifteen seconds for column types. At least one portable GC/ECD is
available and is selective for halogenated organics such as carbon
tetrachloride and trichlorethylene and for nitrogen derivatives. When
using the BCD technique, care should be taken not to overexpose a
particular compound to the detector, as it will become saturated and take
some time to recover.
BCD detectors are moisture sensitive, and some type of
preconcentration is recommended for removal of moisture from the sample.
BCD's are also a source of radiation and must be registered accordingly, a
consideration that may impact purchasing such a device.
Solid state detectors and semiconductors - Another technique
applicable to measuring pollutants has been the use of two types of solid
state detectors: One type measures the heat of reaction produced by
oxidation of a gas on the surface of a catalytic solid. The second
measures change in electrical conductivity of a semiconductor, when
interacted with ionic species.
Pellistor detectors, of the first class, were originally developed for
measuring explosive levels of volatile gases and have limited applications
for detecting trace level toxic organic compounds. Semiconductor devices
measure conductivity changes associated with oxidation and reduction
reactions on the surface of the semiconductor made of oxides of heavy and
transition metals. Many instruments use semiconductors and solid state
devices which measure a wide range of toxics with sensitivity ranges from
1 ppm upward.
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5.2.4. Photometric Devices
Photometric techniques involve monitoring radiant energy emitted by a
species subjected to physical or chemical excitation processes. The two
most common techniques in this category are flame photometric detection
(FPD) and chemiluminescence.
Flame photometric detection (FPD) is based on a spectroscopic
principle which certain elements exhibit when introduced into a
hydrogen/air flame. The light emitted by such elements (e.g. sulfur and
phosphorus) is intensified in emission bands of a particular wavelength
which can be monitored and quantified. The element to be monitored is
selected by placing an appropriate optical filter in front of a
photomultiplier tube to allow only light of the wavelength of interest to
be detected. For example, sulfur compounds are detected using an optical
filter selective for the wavelength of 394 nm. While several elements
could be monitored by this approach, generally only sulfur and phosphorus
compounds are analyzed.
The FPD is used as a total sulfur or phosphorus detector in a "stand
alone" mode (similar to FID for total hydrocarbons). However, inorganic
as well as organic species will be detected, and common inorganic gases
such as SO2 will interfere with organic analysis. Consequently, use of
GC/FPD is advantageous for monitoring sulfur or phosphorus-containing
organics. Detection limits of 10 to 100 ppbv (as S or P) are achievable
in many cases. Detector response is nonlinear.
Chemiluminescence involves the measurement of light emitted frqm a
compound which has been activated by a chemical process. The only
chemiluminescent process to be discussed here is the detection of nitrogen
compounds by conversion of the compound to NO and subsequent reaction with
ozone. The chemical reactions involved are as follows:
(pyrolysis)
R-N + 02 > CO2 + H20 + NO
NO + Og > NO2* + 02
NO2* > NO2 + light
While this approach is highly selective for nitrogen, it does not
distinguish between inorganic and organic nitrogen and thus cannot be used
to detect trace quantities of organic nitrogen compounds in air.
Commercially available systems involving GC preparation have been
developed. This technique for determining trace organic nitrogen
compounds in air provides a method for removing the NO and other
inorganic nitrogen compounds.
5.2.5. Summary
While a large number of screening devices and techniques are
available, one must carefully evaluate the sensitivity, selectivity, and
types of interferences of these techniques before deciding whether or not
they are suitable for use in a particular monitoring situation. Many of
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the available techniques are designed for workplace monitoring where the
levels of interest are greater and the environment is better known and
controlled than is general-ly the case for ambient air monitoring.
In many cases none of the available screening techniques will be
suitable to accomplish a given monitoring objective; therefore, a more
sophisticated analytical approach will be required. In selected cases the
existing screening devices may be suitable if some means of sample
pre-concentration or cleanup is employed. However, extensive sample
workup in the field is generally cumbersome and probably offers little
advantage over conventional laboratory analysis of the sample.
The ionization devices (particularly FID and PID) probably are the
most generally useful in terms of sensitivity for ambient air monitoring,
although colorimetric methods can be quite effective in favorable cases.
A further advantage of the ionization and photometric approaches is the
availability of these techniques in combination with gas chromatography,
which extends the qualitative as well as quantitative capabilities of the
techniques. The IR spectroscopic approach can give useful qualitative
information unavailable by the other techniques but will not be useful for
monitoring ambient levels of many trace components because of spectral
overlap from major organic and inorganic components. The lack of suitable
GC/IR for field use is a further limitation of this approach.
5.3. LABORATORY SCRKNIMG TECHMZQOXS
Laboratory screening techniques generally require the use of more
sophisticated techniques than are applied under field conditions.
The techniques discussed in this section primarily give compound class
information, rather than data for specific compounds. Many techniques
discussed in the preceding section fit this description, although the
current discussion centers on techniques primarily designed for laboratory
rather than field use.
Techniques applicable in this category include:
• Colorimetric techniques.
• Infrared spectroscopy.
• Fluorescence spectroscopy.
• Low resolution mass spectrometry.
Some of these techniques can be used to obtain compound class
information, as well as to determine concentrations of specific
compounds. Compound specific methods based on these techniques are
discussed in Section 6. The techniques themselves are described below:
5.3.1. Colorimtric
A variety of available colorimetric techniques have application to the
analysis of TOAP's. Colorimetric techniques exist for aldehydes,
mercaptans, phenols, amines, and polynuclear aromatic hydrocarbons and in
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some cases have been incorporated into Toxic Organic Methodology (TO-5,
TO-6, TO-8, and TO-11). Relatively few compound class methods for ambient
air have been developed, in the last few years because of the advances in
chromatographic procedures and the intense interest in determining
specific organic compounds.
Most colorimetric techniques involve collection of the compound(s) of
interest in an impinger in either the field or the laboratory, with
subsequent formation of a colored derivative. The content of the impinger
solution should be chosen to (a) stabilize the analytes during collection
and transport and (b) selectively capture the analytes of interest,
allowing potential interferents to pass through.
5.3.2. Infrared Spectroscopy (IR)
IR is widely used as a screening tool for determining organic compound
classes from source emissions in the EPA Level 1 protocol (55). However,
this approach is generally less sensitive than available colorimetric
approaches and will be of value in ambient air monitoring only when high
(ppm) levels of semi-volatile or nonvolatile compounds are present.
The Level 1 IR approach cannot be used for volatile compounds (boiling
point less than 100'C) because of the need for solvent extraction. Gas
phase IR approaches such as those described for field screening could be
employed in the laboratory, but the problems associated with sample
transport make this approach less attractive. Long path IR approaches for
determining specific organic compounds are discussed later.
5.3.3. Fluorescence Spectroscopy
Fluorescence is a relatively inexpensive and highly sensitive
technique useful for determining selected classes of organic compounds.
The principle of fluorescence spectroscopy, as applied to air monitoring,
is discussed in Katz's book (56). Polynuclear aromatic hydrocarbons
(PAH), aromatic amines, and phenols are the primary classes of organic
comounds in ambient air which can be determined using fluorescence
spectroscopy.
A practical limitation of fluorescence spectroscopy is the quenching
phenomenon, whereby large quantities of UV absorbing material reduce the
fluorescence response. Consequently, large quantities of UV absorbing
material must be removed from the sample extract (e.g. by adsorption
chromatography) before a fluorescence determination can be made. A second
limitation is the wide variability in fluorescence response from compound
to compound, even within a given class. This limitation makes development
of a quantitative fluorescence method for compound classes difficult. As
a result of these two limitations most available fluorescence methods
involve chromatographic isolation of a particular compound, prior to its
determination.
5.3.4. Low Resolution Mas* Spectrometry (LAMS)
LRMS is another technique used in the EPA level 1 protocol (55). This
approach suffers from the same limitations as IR when applied to ambient
air monitoring. While the LRMS approach is somewhat more sensitive than
- 55 -
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IR, the data obtained are more difficult to interpret, and the
instrumentation required is more sophisticated and expensive.
Consequently, this approach is of little value for ambient air monitoring.
5.4. COMPOUND SPECIFIC TECHNIQUES
A listing of available techniques for determining specific organic
compounds is given below:
• Gas chromatography (GC).
• Gas chromatography-mass spectrometry (GC-MS).
• High performance liquid chromatography (HPLC).
• Thin layer chromatography (TLC).
• Column chromatography.
• Infrared spectroscopy (IR).
• Ultraviolet or visible absorption (UV-VIS).
• Fluorescence spectroscopy.
Operating principles as well as advantages and limitations of the various
techniques are discussed in the following subsections.
5.4.1. Gas Chromatography (GC)
GC is by far the most widely employed technique in ambient air
monitoring of toxic organic compounds. The sensitivity, specificity, and
versatility of GC, coupled with the relatively volatile nature of most
compounds in ambient air, make this a very attractive technique.
The following discussion of GC principles ie designed to present those
aspects of GC operations important to ambient air analysis. Although the
operation of GC is rather simple, many practical problems can arise which
can be avoided or corrected only by experienced operators. Consequently,
the availability of such personnel is essential to the success of a
monitoring program. It must be remembered that a large number of
compounds may be detected by gas chromatography, even when using specific
detectors and special columns. Coelution can be a problem if adequate
consideration of sample composition is not given when columns are
selected. Great care must be exercised to ensure that reported results
are accurate, since much of the need for toxic organics monitoring exists
in environments where a wide range of potential contaminants may occur.
Basically, GC is a separation technique wherein components of a sample
are separated by differential distribution between a gaseous mobile phase
(usually helium, nitrogen, or hydrogen carrier gas) and a solid or liquid
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stationary phase held in a glass or metal column. The sample is injected
into the carrier gas as a sharp plug, and individual components are
detected as they elute from the column at characteristic "retention times"
after injection. Both column temperature and carrier gas flow must be
carefully controlled to obtain uniform response and retention time
characteristics. The basic components of a gas chromatograph are:
• Gas flow system.
• Injector system.
• Stationary phase (column).
• Oven and associated temperature controller.
• Detector.
• Data recording device.
Only columns, detectors, and injectors will be discussed in detail.
5.4.1.1. Column Types
In order to understand the requirements for the various GC components,
one must recognize that two different types of GC columns are widely
used. The conventional type is called a "packed column" and consists of a
solid support coated with a liquid stationary phase (gas/liquid
chromatograph) or simply a solid adsorbent (gas/solid chromatography).
The second type of column is a wall-coated open tubular (WCOT) or
capillary column and has been widely adopted for environmental analysis
because of its superior resolution and broader applicability, compared to
packed column GC. The capillary column consists of a liquid stationary
phase coated or bonded to specially treated glass or fused silica tubing.
Fused silica tubing is most commonly used because of its physical
durability and superior inertness. Bonded (or cross-linked) columns are
used in preference to coated columns because of the greater operating
temperatures which can be obtained. A significant advancement in column
technology is the development of wide-bore capillary columns. These
columns can be loaded at rates equivalent to packed columns, yet offer the
resolution available with capillary columns. The principles and
applications of capillary column GC are discussed in the appropriate
literature (58,59).
The typical linear flow velocity through both capillary and packed
columns is about 30 cm/sec. However, the much narrower cross sectional
area of the capillary column (0.20 to 0.32 mm ID) translates to a
volumetric flow rate of 1-2 cm /minute versus 30-50 cm /minute for the
packed column. The lower flow rates of capillary columns require that
dead volume in the injector and detector be minimized and that the
effective sample injection volume be reduced. These requirements have
been fulfilled satisfactorily in most modern GC instruments through the
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use of low volume detector cells and split/splitless-type injection
systems. These columns provide superior resolution of complex samples
when the method of sample introduction is a concentrated liquid extract.
However, the low volumetric flow rate and limited capacity for absorption
of analytes present some problems in the use of these columns.
Recent advances in capillary column technology have produced wide bore
and ultrawide bore capillary columns with ID's of up to 0.75 mm. These
columns are particularly well-suited to air sample analysis using various
injection techniques. The columns can operate at higher flow rates, up to
about 20 mL/minute. Larger sample volumes can be injected by gas sampling
loops or syringes, without producing severe peak broadening of the early
eluting compounds. It should be noted that resolution of Cj^ through
Cg substituted aromatics using capillary column technology is very
difficult.
While the use of packed columns has decreased in recent years, these
columns are still very effective for many analyses. The very low boiling
compounds, such as methane, chloromethane, ethylene, and others are
difficult to resolve using capillary column techniques, unless cooling the
compounds to subambient temperatures is possible. Packed columns using
carbon molecular sieves are very effective for performing this type of
analysis. Also, the stationary phase selection available on packed
columns far exceeds that for capillaries.
5.4.1.2. Detector Types
The GC detection system chosen determines, to a large extent, the
specificity and sensitivity of an analytical method. Consequently, one
should carefully review the program requirements when selecting a
detection system for use in a given study.
The primary detector types in use today are:
• Flame Zonization Detector (FID).
• Electron Capture Detector (BCD).
• Photoionization Detector (PID).
• Flame Photometric Detector (FPD).
• Alkali Bead Thermionic Detector.
• Hall Electrolytic Conductivity Detector (HECD).
• Mass Selective Detector (MSD).
• Chemiluminescence Detector (CLD).
• Fourier Transform Infrared Detector (FTIRD).
Table 5.1 provides an overview of the characteristics of available
detection systems. The principles of operation for many detectors are
briefly described in the section on field monitoring techniques.
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By far the moat widely used GC detector is the flame ionization
detector (FID), which provides good sensitivity and uniform response based
on the effective number of carbon atoms for a wide variety of compounds.
The uniformity of the FID's response allows fairly accurate quantification
of compounds for which specific response factors have not been
determined. This is probably the most advantageous feature of the FID and
is useful for ambient air monitoring studies in which the complete range
of compounds present cannot be anticipated. None of the other detectors
gives nearly as uniform a response as FID, for compounds in a given
class. Another major advantage of FID is the very wide linear dynamic
range of the response. The detector itself is linear over a range from
subnanogram to milligram quantities of a detected compound.
The electron capture detector is becoming more widely used in ambient
air monitoring because of its greater sensitivity, compared to FID. ECD
is selective for electron deficient materials, especially polyhalogenated
and nitrosubstituted compounds. In favorable cases, picogram (10~ g)
levels can be detected, but response varies widely from one compound to
the next. Several literature references which describe the detection
sensitivities of various compounds on ECD are available (60-62). A
drawback sometimes encountered when using ECD on direct injected gas
samples is the quenching effect of oxygen from the air on the detector
response. This limitation sometimes precludes use of ECD for certain
analyses.
Like ECD the photoionization (PID) detector is enjoying wider use in
ambient air monitoring because of its greater sensitivity and selectivity
in comparison to FID. PID is widely viewed as a substitute for FID,
although its response varies considerably from compound to compound. PID
is particularly useful for monitoring aromatic compounds. References
describe the detection sensitivities for various compounds of PID (60-62).
The flame photometric (FPD) detector is specific for either phosphorus
or sulfur compounds, depending on the optical filter employed, and gives
sensitivity comparable to or greater than FID. The response obtained is
logarithmically related to the amount of sulfur or phosphorus injected.
This detector is of particular advantage when trace levels of phosphorus
or sulfur compounds must be detected in the presence of much greater
quantities of aliphatic hydrocarbons.
The alkali flame (AFD), thermionic specific (TSD), or nitrogen-
phosphorus (NPD) detector is selective for nitrogen and phosphorus
compounds and is considerably more sensitive than either FPD or FID.
However, response varies considerably from compound to compound. This
detector is preferred over FPD for determining phosphorus compounds, in
many cases, because of its greater sensitivity.
The Hall electrolytic conductivity detector (HECD) can be operated in
either halogen-, sulfur-, or nitrogen-* specific modes, although the
halogen-specific mode is the most widely employed. This system gives
poorer sensitivity than ECD for polyhalogenated compounds but better
response for monohalogenated compounds such as vinyl chloride, since the
HECD response is proportional to the amount of halogen injected.
Correspondingly, the HECD gives a more uniform response for
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polyhalogenated compounds than BCD. An additional advantage of HECD is
its temperature stability, which allows temperature programming (BCD
drifts considerably under temperature programmed conditions). HECD is not
widely used in air monitoring programs because the greater sensitivity of
ECD is highly desirable and tends to outweigh other considerations.
A continuing challenge in GC analysis of organic compounds in ambient
air is the qualitative identification of components identified by the
various detection systems. Use of mass spectrometry as a GC detector
(GC-MS), a highly effective tool in this regard, is discussed later in
this section. However, GC-MS is a very expensive instrument and is not
always available. A less costly, though still expensive, option is the
mass selective detector. This detector is basically a mass spectrometer
without full scanning capabilities. The detector can be set up to monitor
from three to ten ions selected by the operator. These may be changed
during the run. The ions selected are characteristic of one or more
compounds of interest. By observing properly selected multiple ions for a
single compound, qualitative information can be gained.
Other attractive alternatives to GC-MS include analyzing samples
twice, using dissimilar columns or dual (parallel or series) detectors.
The latter approach is more attractive because only a single injection of
sample is required, and retention times can be accurately matched from the
two outputs. If series detectors are employed, the first detector must be
sealed, non-destructive towards the sample, and have a low dead volume to
reduce peak broadening. On the other hand, parallel detector operation
requires a precise stream splitter. Such a system has been described for
simultaneous FID/FID detection using capillary columns GC (60).
Some detector combinations found to be most useful in terms of
qualitative information are listed in Table 5.2. Note that each detector
combination contains one selective (ECD, HCD, or NPD) and one relatively
nonselective (PID or FID) detector. This approach allows the selective
and sensitive detection of compounds of special interest, as well as the
detection of any large, unanticipated components. The ratio of response
for a given peak on the two detectors helps confirm the identity of the
compound.
The chentiluminescence detector uses oxidation and reduction of
nitrogen in compounds to form nitric oxide. The nitric oxide then reacts
with ozone in a light-producing reaction. The detector is highly
selective and sensitive for nitrogen containing compounds. Application of
this detector to environmental analytes is in its early stages, due to the
newness of the detector. Ambient air monitoring by CLD should be seen
more in the future.
5.4.1.3. injection System*
Injection systems are of particular importance in GC analysis of
ambient air, because of the wide range of forms in which the sample may be
collected. The primary injection modes, based on the manner of sample
collection, include:
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TABLE 5.2
USEFUL DUAL GC DETECTOR COMBINATIONS
DETECTOR COMBINATION
APPLICATION
ECD-PID (Series)
PID-FID (Series)
ECD-riD (Series)
PID-HECD (Series)
NPD-FID (Parallel)
FPD-FID (Parallel)
PID-NPD (Series)
HECD-FID (Parallel)
FTIR-MS (Series)
Volatile Aromatics and
Chlorinated Solvents
Aromatic Hydrocarbons
Chlorinated Hydrocarbons
Aromatic and Halogenated
Volatile Compounds
Nitrogen or Phosphorous
Compounds
Sulfur Compounds
Amines
Hydrocarbons and
Halogenated Hydrocarbons
Hydrocarbons, Aldehydes,
and Ketones
- 62 -
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• Liquid injection (particulate or reain extract).
• Whole air injection (syringe or valve).
• Thermal desorption.
• Cryogenic trapping of whole air sample.
Liquid and whole air injections are relatively straightforward and
employ conventional techniques. In the case of capillary column GC a
well-designed splitless injector is required to obtain optimal resolution
and prevent solvent tailing. Generally, the capillary column temperature
is maintained well below the analyte's elution temperature, in order to
reduce peak broadening.
Thermal desorption of resin samples involves (a) heating the resin
cartridge to a suitable temperature in an inert gas stream, (b) passing
the inert gas stream through a cryogenically cooled trap to condense the
desorbed analytes, and (c) flash evaporating the analytes onto a GC column
held at low temperature to "focus" the materials at the head of the
column. Instrumentation allowing semiautomatic operation of the system is
available.
The whole air, cryogenic sampling procedure is similar to the process
described above except that thermal desorption of the resin is omitted.
As described in the literature (39) a 30-500 ml volume of air is passed
through a cryogenically cooled trap (liquid argon), and the condensed
material is flash evaporated onto a GC column held at low temperature
(e.g. -50*C). In both cases, the desorbed components are separated by
temperature programming of the GC column.
Both resin and cryogenic thermal desorption approaches require the use
of nonadsorptive stainless steel or Teflon valves and fittings capable of
withstanding extreme operating temperatures without leaking or
contaminating the system. Capillary columns should be directly coupled to
the injection valve by means of Teflon and stainless steel fittings, as
opposed to using conventional splitless injectors.
5.4.2. Gas Chxonatography-Ma** Spectrometry (GC-MS)
In principle, GC-MS can be viewed as another detection mode for gas
chromatography. However, in practice GC-MS is a highly sophisticated and
powerful technique requiring more specialized skills and detailed
knowledge than required for other forms of GC. A detailed discussion of
GC-MS theory and practice is beyond the scope of this document. A
comprehensive discussion of GC-MS is available in textbook form (63).
Essentially, mass spectra are obtained by bombarding the sample with
an electron beam which knocks electrons or negative groups from the
molecule, producing excited and reactive species. These species further
decompose, producing ionized fragments characteristic of the parent
molecule. The ions are accelerated, passed through a magnetic field, and
detected by an ionization gauge. Generally, only the singly positively
charged ions are detected. The resulting spectral pattern is characteris-
tic of the molecule and can thus be used to identify different chemical
species.
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5.4.2.1. Instrumentation
In addition to the GC system the major components of a GC-MS system
include:
• Interface (between GC column and MS ion source).
• Ion source.
• Mass analyzer.
• Vacuum system(s)
• Data acquisition and instrument control system.
Mass spectrometric analysis involves the following sequential
processes:
• lonization of the sample introduced into the ion source.
• Acceleration of the ions from the ion source into the mass
analyzer region.
• Separation of the ions in the mass analyzer region on the basis
of the mass to charge (m/e) ratio.
• Detection of the ions at each mass.
In order to minimize ion-molecule reactions and interference from air the
ion source, mass analyzer, and ion detector must be maintained at low
pressure (10 mm of Hg or less). Consequently, the high vacuum system
is a critical component of the GC-MS system, and air leakage through
valves, fittings, and/or flanges is a common problem in GC-MS.
Because a GC operates at ambient pressure and above, whereas the MS
must be maintained at low pressure, the GC-MS interface ideally will
discard excess carrier gas flow and quantitatively deliver the sample
components into the ion source for subsequent determination. Typical
GC-MS systems can accept approximately 2-3 ml/minute of gas flow without
significant spectral distortion (due to elevated pressure in the MS
system). The use of capillary column GC, therefore, allows the entire
column effluent to be delivered to the ion source. If fused silica
columns are used, the column can actually be placed directly into the
entrance of the ion source. However, packed column GC-MS operation, in
which column flow rates of 30-50 ml/minute are common, requires the use of
membrane or jet separators to remove a large portion of the light carrier
gas (usually helium) delivering the majority of the sample to the ion
source.
The avoidance of membrane and/or jet separators and associated
fittings, in addition to the other inherent advantages of capillary column
GC (i.e. better resolution, less irreversible adsorption), make capillary
column GC-MS preferable to packed column GC-MS for most environmental
applications. In fact many of the newer commercial GC-MS systems are
designed primarily for capillary column operations.
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Although a wide variety of powerful, specialized forms of MS
ionization modes, mass analysis schemes, etc. are available, the majority
of ambient air monitoring applications uses electron impact (70 eV)
ionization and quadrupole mass analyzers. One must bear in mind that low
resolution mass spectral identifications are considered tentative and for
litigation purposes high resolution spectral data may be required. A
discussion of the various optional approaches is provided in the
previously referenced text (63).
GC-MS analysis of complex environmental samples results in the
acquisition of much data. A typical capillary column GC-MS run might
result in the acquisition of 2000 mass spectra (e.g. one scan per second)
over a range of 40-400 atomic mass units and representing 100-200
individual components. Obviously the acquisition and reduction of this
volume of data requires experienced personnel and the use of a laboratory
computer system operating with a set of sophisticated software. Typical
GC-MS systems use laboratory mini-computers with high density magnetic
disks for mass storage. Archival storage of data is usually accomplished
using 9-track magnetic tape, a more convenient medium than disks for
long-term storage.
A new form of mass spectrometry, termed MS-MS or triple quadrupole MS,
has rscently become available and is receiving much attention (64). This
technique involves direct analysis of an atmospheric sample by (a)
ionizing the sample components in an atmospheric pressure ion source, (b)
separating the ions in the first quadrupole mass analyzer, (c) passing an
ion of one specific mass into a second quadrupole containing a collision
gas such as argon, and (d) separating the product ions resulting from the
ion molecule reaction in (c) by means of a third quadrupole. The use of
two mass analyzers in series introduces great selectivity into the
analysis, hence eliminating the requirement for GC separation in many
cases. In practice the MS-MS approach is highly sophisticated and
expensive, thus limiting its availability for most ambient air monitoring
programs. MS-MS techniques have been employed for air quality modeling
work and for more monitoring ambient dioxin concentrations at remediation
sites. However, in selected cases MS-MS may be the only technique capable
of detecting trace levels of contamination.
5.4.2.2. Application*
The power of GC-MS analysis has resulted in a wide variety of
applications, especially in the environmental area. Reviews (65) and
research articles describing these applications are available throughout
the scientific literature, and no attempt will be made to summarize that
information here.
GC-MS analysis can be used effectively for ambient air monitoring in
two generalized operating modes: The first involves surveying collected
samples to determine what compounds are present and their approximate
concentrations. A typical example of this operating mode is the widely
used Tenax resin collection/GC-MS analysis method for ambient air surveys
(66). This operating mode takes advantage of the powerful identification
capability of GC-MS and is often used in conjunction with other GC
detection schemes, wherein the sample components quantified by FID, ECD,
etc. are identified by GC-MS.
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The second mode of GC-MS operation involves searching a sample for
trace levels of specific compound(s) and accurately quantifying this
material. This operating mode typically employs a form of GC-MS termed
"selected ion monitoring" (SIM) or "multiple ion detection" (MID) whereby
only a few selected ions are monitored, rather than scanning a broad mass
region, as in the first operating mode. The SIM approach is much more
sensitive and accurate than full spectrum scanning approaches.
5.4.3. High Performance Liquid Chromatography (HffLC)
HPLC is a technique designed primarily for the determination of polar
and nonvolatile compounds not readily determined by gas chromatography.
Consequently, HPLC is not widely used for ambient air monitoring, in which
most compounds of interest are relatively volatile. Two specialized cases
in which HPLC is useful for ambient air monitoring are:
• Determination of nonvolatile material (e.g. PAH'a) in ambient
particulate material.
• Determination of reactive components (e.g. aldehydes) by reacting
the compounds with a derivatizing reagent.
The theory and application of HPLC have been described in detail in
textbook form (67).
The important components of an HPLC system include:
• Pump.
• Injection valve.
• Column.
• Detector.
• Data recording device.
HPLC separation, like GC separation, involves separation of sample
components on the basis of the differential distribution between mobile
and stationary phases. However, GC separations are performed primarily on
the baais of volatility, whereas HPLC separation mechanisms are much more
varied and complex. The liquid mobile phase composition has a profound
effect on component retention, and a change in mobile phase composition
can lead to reversal of the elution order for two components.
The most commonly employed forms of HPLC are (a) normal phase
chromatography and (b) reversed phase chromatography. Normal phase HPLC
uses a polar stationary phase (e.g. silica gel, alumina) and a relatively
nonpolar mobile phase (e.g. hexane, methylene chloride). Separation is
based primarily on an adsorption mechanism, with polar components eluting
later than on nonpolar components. Reversed phase HPLC was developed
later than normal phase HPLC and uses a nonpolar (usually chemically
bonded) stationary phase and polar (e.g. water, methanol, acetonitrile)
mobile phase. Reversed phase HPLC separates primarily on a partition
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mechanism, with hydrophilic components eluting earlier than hydrophobia
components. At present, reversed phase HPLC is more widely used than
normal phase HPLC because of the greater versatility of this technique.
In order to achieve rapid, efficient separation of sample components,
HPLC techniques employ microparticulate packing materials, typically
spherical materials of 5 urn diameter. HPLC requires a pumping system
capable of delivering a precise, pulse-free flow (e.g. 1-2 ml/minute) of
mobile phase at pressures of up to 400 atmospheres. Obviously, high
pressure injection valves, columns, and fittings are also required.
Because of the relatively low flow rates involved (compared to GC) "dead
volume" in fittings, injection valves, and detector cells must be
minimized to maintain good separation efficiency.
Recent advances in HPLC column technology have resulted in the
development of capillary HPLC columns. These columns have the potential
to have a similar impact on the HPLC technique that capillary columns had
on GC.
A variety of detection systems are available for HPLC. The readily
available detectors of value in ambient air monitoring are listed in Table
5.3. By far the most widely used HPLC detector is the UV detector (either
fixed or variable wavelength). Unfortunately no sensitive, universal
detector (equivalent to GC/FID) is available for HPLC. This limitation
tends to reduce HPLC to the role of a specialized analytical tool for
determining selected classes of compounds, at least in the ambient air
monitoring area. LC-MS technology has advanced to the point where it is
technically and practically feasible for confirmatory analysis in much the
same fashion that GC-MS is.
5.4.4. Thin Layer and Column Chromatography
Column chromatography and thin layer chromatography (TLC) are widely
used as "cleanup" techniques, prior to GC-MS, GC, or HPLC determination,
and are no longer widely used as determinative techniques in ambient air
monitoring. The few methods whereby these techniques have been used for
compound determination, such as PAH analysis (68), have been largely
replaced by HPLC methods. However, in some cases (e.g. benzo(a)pyrene
analysis in ambient air) TLC has remained a viable technique because of
its lower cost compared to HPLC. Both TLC and column chromatography are
forms of adsorption chromatography.
5.4.5. Spectroscopic Techniques
Spectroscopic techniques of potential value for compound specific
analysis include infrared spectroscopy (IR), fluorescence spectroscopy,
and ultraviolet-visible absorption (UV-VIS) spectroscopy. However, UV-VIS
and fluorescence spectroscopy are not sufficiently selective to be of
value except in combination with chromatographic procedures.
Consequently, these two techniques are used as online HPLC detectors as
well as offline determinative procedures in combination with GC, TLC, or
HPLC. PAH methods using these approaches have been described (70).
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TABLE 5.3
HPLC DETECTORS
DETECTOR
APPROXIMATE
SENSITIVITY,
AMOUNT INJECTED
APPLICATION
Ultraviolet, Fixed, or
Variable Wavelength
Fluorescence
Electrochemical
Refractive Index
10-9g
10-12g
10-"g
10~6g
PAH, phenols,
heterocycles
PAH, aromatic
phenols
Aromatic amines
phenols
nitrogen
amines,
,
Too insensitive for
Mass Spectrometer
10~8g
environmental applica-
tions
Confirmatory analysis
for selected organic
compounds
IR is also useful as an online or offline determinative tool. The
advent of rapid scanning Fourier transform IR (FTIR) techniques has
improved instrumental sensitivity and analysis speed, making online
GC/FTIR techniques feasible (71). GC/FTIR is still in the early stages,
and many commercial instruments are available. Long path (kilometer) FTIR
techniques have been used to detect individual compounds (for example,
formaldehyde) in ambient air (72). This technique has the advantage that
sample collection is not required. However, this is not a readily
available technique and hence is of limited value in ambient air
monitoring programs.
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SECTION 6
SPECIFIC SAMPLING AND ANALYTICAL METHODS
Since the original publication of the TAD, EPA has concentrated on
compiling reference methods for the sampling and analysis of toxic organic
air pollutants (TOAP's). These efforts have culminated in the publication
of a document entitled "Compendium of Methods for the Determination of
Toxic Organic Compounds in Ambient Air." Supplements to this document
have been published, and additional supplements are expected as new
methods become available. Table 6.1 summarizes the various methods
currently published in the compendium. These methods represent compatible
combinations of the sampling and analytical procedures described in
Sections 4 and 5 of this document. Brief descriptions of the sampling and
analytical procedures for each of these methodologies are provided in
Appendix B. Table 6.2 summarizes the compounds for which method
performance has been documented.
In order to minimize the number of methods required for a given
monitoring program methods which apply to multiple compounds or even to
multiple classes of compounds should be used. Table 6.1 indicates that
four methods, TO-1, TO-2, TO-3, and TO-14, have the broadest application.
With the exception of TO-4 and TO-10, which are designed for
polychlorinated biphenyls and organochlorine pesticides, the remaining
methods have limited application. Methods TO-1, TO-2, and TO-3 all employ
solid sorbents, while Method TO-14 employs canisters. Methods TO-1 and
TO-14 essentially represent the standard methods for TOAP monitoring
programs and should be used whenever their application is appropriate.
Selection of an appropriate method will be affected by the monitoring
plan considerations discussed in Section 3 of this document. In some
cases, method performance will not be documented for compounds which are
the focus of concern. This will require that the most appropriate method
be selected and that method performance be validated for the compounds of
interest. Alternatively, methods published by the National Institute of
Occupational Safety and Health (NIOSH) or by the American Society of
Testing and Materials (ASTM) can be used after appropriate validation for
ambient studies.
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TABLE 6.1
METHODS FOR THE ANALYSIS OF TOXIC ORGANIC
AIR POLLUTANTS IN AMBIENT AIR
METHOD
NUMBER METHOD TITLE POLLUTANT TYPES
TO-1 Determination of volatile organic Volatile, nonpolar organics
compounds in ambient air, using having boiling points in the
Tenax adsorption and gas 80* to 200*C range.
chromatography/mass spectroscopy
TO-2 Determination of volatile organic Highly volatile, nonpolar
compounds in ambient air by organics having boiling
carbon molecular sieve adsorption points in the range of
and gas chromatography/mass -15* to 120*C
spectroscopy
TO-3 Determination of volatile organic Volatile, nonpolar organics
compounds in ambient air, using having boiling points in the
cryogenic preconcentration tech- range of -10* to 200*C
niques and gas chromatography
with flame ionization and electron
capture detection
TO-4 Determination of organochlorine Organochlorine pesticides
pesticides and polychlorinated and polychlorinated
biphenyls in ambient air biphenyls
TO-5 Determination of aldehydes in Aldehydes and ketones
ambient air, using high perform-
ance liquid chromatography
TO-6 Determination of phosgene in Phosgene
ambient air, using high perform-
ance liquid chromatography
TO-7 Determination on N-nitroso- N-nitrosodimethylamine
dimethylamine in ambient air,
using gas chromatography
TO-8 Determination of phenol and Cresol, Phenol
methylphenols in ambient air,
using high performance liquid
chromatography
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TABLE 6.1
(Continued)
METHODS FOR THE ANALYSIS OF TOXIC ORGANIC
AIR »OLLUTAMTS IN AMBIENT AIR
METHOD
NUMBER METHOD TITLE POLLUTANT TYPES
TO-9 Determination of polyehlorinated Dioxina
dibenso-p-dioxina (PCDD'a) in
ambient air, uaing high-reaolution
gaa chromatography/high-reaolution
mass spectroaoopy
TO-10 Determination of peaticidea in Pesticides
ambient air, uaing low volume
polyurethane foam aampling with
gaa chromatography/electron
capture detection
TO-11 Determination of formaldehyde Formaldehyde
in ambient air, uaing DNPH-coated
Sep-pak cartridge aampling with
gaa chromatography/electron
capture detection
TO-12 Determination of non-methane Non-methane organic
organic oompounda in ambient compounds
air, uaing cryogenic preeoncen-
tration and direct flame
ioniiation detection
TO-13 Methoda of detection of benso(a) Polynuclear aromatic
pyrene and other polynuolear hydrocarbons
aromatic hydrooarbona in ambient
air, uaing OC and HPLC
TO-14 Determination of volatile organic Volatile organic compounds
oompounda in ambient air, uaing
Summa*-poliahed eaniatera and gaa
chromatographic analyaia
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TABLE 6.2
SAMPLING AND ANALYTICAL METHODOLOGIES.
FOR SELECTED TOXIC ORGANIC AIR POLLUTANTS
COMPOUND
APPLICABLE METHODS
Acetaldehyde
Acrolein
Aerylonitrile
Allyl Chloride
Aldrin
Benzaldehyde
Benzene
Benzo(a)Pyrene
Benzylchloride
Bromoform (Tribromomethane)
Bromobenzene
Bromomethane
Captan
Carbon Tetrachloride
Chlordane
Chlorobenzene
Chloroethane
Chloromethane
Chloroform (Trichloromethane)
Chlorothalonil
Chlorpyrifos
Cresols (o, m, p - Methyl Phenols)
Cumene
2,4,-D esters
4,4'-DDE
4,4'-DDT
1,2-Dichlorobenzene
1,3-Dichlorobenzene
1,4-Dichlorobenzene
Dichlorodifluoromethane
1,2-Dichloroethane
1,1-Dichloroethene
cis-1,2-Dichloroethylene
1,2-Dichloropropane
1,3-Dichloropropane
cis-1.3-Dichloropropene
trana-1.3-DichloroDropene
1,2-Dichloro-l,1,2,2-tetrafluoroethane
Dichlorvos (DDVP)
Dicofol
Dieldrin
Endrin
TO- 5
TO-5
TO- 2, TO- 3
TO- 2, TO- 3
TO-4, TO-10
TO-5
TO-1, TO-2,
TO- 13
TO-1, TO-3,
TO-1, TO-3
TO-1
TO- 14
TO-10
TO-1, TO-2,
TO-10
TO-1, TO-3,
TO- 14
TO- 14
TO-1, TO-2,
TO-10
TO-10
TO-8
TO-1
TO-10
TO-4, TO-10
TO-4, TO-10
TO- 14
TO- 14
TO-1, TO-3,
TO- 14
TO-1, TO-2,
TO-2, TO-3,
TO- 14
TO-1, TO-1 4
TO-1
TO- 14
TO- 14
TO- 14
TO-10
TO-10
TO-10
TO-10
TO-3, TO-1 4
TO- 14
TO-3, TO-14
TO- 14
TO-3, TO-14
TO-14
TO-3, TO-14
TO-14
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TABLE 6.2
(CONTINUED)
SAMPLING AND ANALYTICAL METHODOLOGIES
FOR SELECTED TOXIC ORGANIC AIR POLLUTANTS
COMPOUND
APPLICABLE METHODS
Endrin Aldehyde
Ethylbenzene
Ehylene Dibromide
4-Ethyltoluene
Folpet
Formaldehyde
Heptachlor
Heptachlor epoxide
1,2,3/4,7,8-Hexachlorodibenzo-p-Dioxin
Hexachlorobenzene
Hexachlorobutadlene
and fi-Hexachlorocyclohexanea
Llndane
Methoxychlor
Methylene Chloride
Mexacarbate
Mi rex
Nitrobenzene
N-Nitrosodimethylamine
trana-Nonachlor
Octachlorodibenzo-p-Dioxin
Oxychlordane
Pentachlorobenzene
Pentachlorophenol
Phenol
Phosgene
Polychlorinated Biphenyls
Propanal
Ronnel
Styrene
1,2,3,4-Tetrachlorodibenzo-p-Dioxin
2,3,7,8-Tetrachlorodibenzo-p-Dioxin
1,1,2,2-Tetrachloroethane
Tetrachloroethylene
Toluene
1,2,4-Trichlorobenzene
1,1,1-Trichloroethane
1,1,2-Trichloroethane
Trichlorofluoromethane
TO-10
TO-1,TO-14
TO-1, TO-14
TO-14
TO-10
TO-5, TO-11
TO-10
TO-10
TO-9
TO-10
TO-14
TO-10
TO-10
TO-10
TO-2, TO-3, TO-14
TO-10
TO-10
TO-1, TO-3
TO-7
TO-10
TO-9
TO-10
TO-10
TO-10
TO-8
TO-6
TO-4
TO-5
TO-10
TO-14
TO-9
TO-9
TO-14
TO-1, TO-3, TO-14
TO-1, TO-2, TO-3, TO-14
TO-14
TO-1, TO-2, TO-3, TO-14
TO-14
TO-14
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TABLE 6.2
(CONTINUED)
SAMPLING AMD ANALYTICAL METHODOLOGIES
FOR SELECTED TOXIC ORGANIC AIR POLLUTANTS
COMPOUND
APPLICABLE METHODS
1,1,2-Trichloro-l,2,2-trifluoroethane
2,4,5-Trichlorophenol
1,2,4-Trimethylbenzene
1,3,5-Trimethylbenzene
Vinyl Chloride
o, m, p-Xylene
TO-14
TO-10
TO-14
TO-14
TO-2, TO-3, TO-14
TO-lf T0-3r TO-14
1TO-14 nwthodology hac b««n validated with pr«««uris«d canisters
only.
Breakthrough volume using TO-1 it low.
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SECTION 7
QUALITY ASSURANCE
7.1. QUALITY ASSURANCE EXPECTATIONS
As the discussion of Data Quality Objectives in Section 3 indicates,
the environmental data used in a decision process must be (1) technically
sound and defensible and (2) of sufficient quality to support the decision
process. Achievement of DQO's is ultimately accomplished through a
Quality Assurance (QA) program. An effective QA program for inclusion in
a TOAP monitoring program will consist of planned and systematic
activities necessary to establish consistency of the program output with
the needs for which the program was established. Program needs can
ultimately be understood in terms of acceptable uncertainty associated
with the data; a QA program ensures that the limit of uncertainty is
within the acceptable boundaries of the data collection program.
The limit of uncertainty will vary with the sampling and analytical
procedures. Consequently, there is no universal QA performance standard
applicable to all TOAP monitoring programs. It is therefore important to
establish QA performance standards consistent with both the intended use
of the data and the performance characteristics of the sampling and
analysis procedures. Failure to reconcile discrepancies that exist
between intended data use and QA performance characteristics of the
sampling and analytical protocol will undermine the TOAP monitoring
program.
7.2 QUALITY ASSURANCE AND QUALITY CONTROL
QA is essentially a management program that addresses delegation of
program responsibilities to individuals, documentation, data review, and
audits. The objective of QA procedures is to permit an assessment of the
reliability of the data. QA activities are typically performed by
personnel involved in normal routine operations.
Quality Control (QC) activities complement QA activities. QC
activities address sampling procedures, sample integrity, analysis
methods, calibration procedures, equipment maintenance procedures, and
data production. QC procedures are also performed by individuals involved
in the normal routine operations.
7.3 QUALITY ASSURANCE MANAGEMENT
A QA program is essentially a management tool used to ensure that data
collected is continually consistent with predetermined quality limits.
The major elements of an effective QA program included in a TOAP
monitoring program are discussed in the following subsections.
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7.3.1 Quality A*>uranc« System D««ign
Three fundamental elements comprise an effective .QA program: First,
QA policy and quantitative quality goals or objectives must be defined in
a written QA plan. Secondly, organizational structure must accommodate a
QA function through job assignments and communication mechanisms. Third,
individuals associated with the QA function must have written job
descriptions, duties, responsibilities, and authority commensurate with
their intended function. Each of these vital QA program components is
discussed below:
Before a QA program can be developed, it is necessary to establish a
QA policy and establish the objectives of the QA program. Once these
fundamental tasks have been accomplished, a QA program can be written to
address the strategy for achieving definitive quality objectives relevant
to the activities of the organization.
Strategic QA program planning will obviously require an organizational
structure conducive to effective QA management. Appropriate
considerations for organizational structure include personnel assignments
and communication.
Effective QA is accomplished by a separate individual or group within
the organization. The individual(s) responsible for QA will have written
job descriptions and the corresponding duties, responsibilities, and
authority to perform their job functions in a manner that satisfies the QA
program requirements.
Although individuals associated with the QA functions are removed from
the routine operations they are responsible for assessing, they are by no
means totally isolated from those routine operations. Open lines of
communication and established communication practices are necessary to
ensure interaction between QA personnel, personnel generating data, and
personnel assimilating the data. Effective communication is therefore
essential to the QA program and will ensure that QA functions are
adequately reflected in data output.
7.3.2 Document Control
Because of the volume of written information associated with a TOAP
monitoring program, it is necessary to establish procedures for document
control, consisting of written procedures for inspection, review,
revision, and archival of monitoring program documents. Document control
procedures are generally applicable to the following:
• Sampling procedure.
• Calibration procedure.
• Analytical procedure.
• Data analyses, validation, and reporting procedure.
• Performance and system audit procedure.
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• Preventive maintenance procedure.
• The QA program plan.
• QA plans for specific projects
• Laboratory record notebooks.
• Data sheets.
7.3.3 Data Evaluation
The intent of a QA program is to maintain data continuously within
pre-determined quality limits. This objective will not be achieved if
information applicable to a QA management activity is not received,
reviewed, and/or acted on in a timely manner. An effective QA program
will therefore establish what information is required by QA management
personnel, how it will be used, when it will be required, when it will be
reviewed, and when control actions necessitated by unacceptable data will
be implemented.
7.3.4 Standard Rafaranc* Materials
The fundamental requirements for producing reliable data are
appropriate methodology and properly calibrated instrumentation used
according to established procedure. The quality of generated data can be
assessed by incorporating reference materials into the sampling and
analytical processes.
A reference material is a substance for which critical properties are
sufficiently well established for the reference material to be used to
calibrate an analyzer or validate a measurement process. Generally
speaking, there are three types of reference materials in common use: An
internal reference material (ICM) is developed by a laboratory for its own
internal use. A certified reference material (CRM) is a reference
material issued by an organization recognized by practicing professionals
as technically competent to do so. A Standard Reference Material (SRM) is
a certified reference material issued by the National Institute of
Standards and Technology (NIST). All three types of reference materials
are integral components of effective QA programs for TOAP monitoring
projects. SRM's are particularly important because they are traceable to
national standards and, if used as primary standards, allow meaningful
comparisons of data generated by different laboratories or by different
sampling and analytical procedures.
SRM's for toxic organic air pollutants at sub PPM and PPB levels were
unavailable until recently. Within the past two years SRM's for several
TOAP's at the 5 ppb level have been developed as multi-component mixtures.
Information concerning these materials is provided in Appendix E.
Whenever possible, these SRM's should be incorporated into the QA program
for a TOAP monitoring project.
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7.3.5 Quality Audits
Quality auditing tasks are similar to quality control tasks and in
some instances may be identical. The significant difference between
quality auditing and quality control tasks is that the former are
administered by individuals who are not directly involved with the
measurement process.
7.3.5.1 Performance Audits
Performance audits are incorporated into a TOAP monitoring program to
quantitatively assess the quality of the data being generated by a
measurement system. Performance audits include the evaluation of recovery
of reference materials through the sampling and analytical equipment and
the review of results when test data are entered into a data processing
system.
7.3.5.2 System Audits
System audits are incorporated into a TOAP monitoring program to
qualitatively assess the quality of data being generated by the
measurement system. System audits focus on operational aspects of the
measurement process. There aspects include adherence to (a) established
sampling and analytical procedures, (b) sample shipment and receipt
procedures, (c) equipment maintenance schedules, and (d) quality control
and quality audit schedules.
7.3.6 Quality Assurance Reports
A variety of QA reports should be prepared periodically by the QA
personnel and submitted to the TOAP monitoring program manager. The
frequency and type of report required will be specified by the QA project
plan.
Data Quality Assessment Reports address the precision and accuracy of
program data. Performance and System Audit Reports summarize the results
of audits performed during the course of the TOAP monitoring project.
Data Validation Reports summarize questionable data collected during the
monitoring program, the results of follow-up investigations concerning
such data, data corrected or rejected as a result of the investigation,
corrective action recommended, and effectiveness of the data validation
procedures. Quality Cost Reports summarize the costs associated with each
element (prevention, appraisal, and failure) of a Quality Cost System for
a TOAP monitoring program. Instrument and/or Equipment Downtime Reports
summarize information concerning instrument and/or equipment failures,
failure courses, repair time, and total downtime. Control Charts are
graphical representations of QA Data. Finally, Interlaboratorv Comparison
Summary Reports are published by EPA and are applicable only to specific
analytes and methodologies.
7.3.7 Corrective Action
In many cases data review or audit procedures will result in the need
for corrective action. This may involve reporting certain aspects of the
work or simply providing more detailed documentation for work already
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performed. In either case QA management will be responsible for docu-
menting the need for, type of, and implementation of corrective action.
7.3.8 Training
An important component of a QA program will involve personnel
training. Trained personnel are necessary to ensure that the data they
produce are complete and of high quality. Training can be accomplished on
the job or by trainees attending courses relevant to the employees' job
functions.
The effectiveness of training must be documented to establish and
maintain the integrity of the training program. Training effectiveness
can be evaluated by written tests, proficiency evaluations, and/or
interviews.
7.4 SAMPLING QUALITY ASSURANCE
The purpose of sampling is to collect unbiased samples that are
representative of the system being monitored. The sampling program should
be planned and documented in all details. QA for sampling includes site
selection, number of samples to be collected, frequency of sample
collection, sampling times, instrument calibration and maintenance,
Quality Control sample collection, data recording, sample labeling, sample
preservation, sample storage, sample transport, and chain-of-custody
procedures.
7.4.1 Sit* Selection
Site selection planning is discussed thoroughly in Section 3.3. The
QA plan for a TOAP monitoring program should specify factors which could
result in modification of the siting plan during the monitoring effort,
procedures for approving such modifications, and provisions for
documenting sampling site modifications.
7.4.2 Instrument Calibration and Maintenance
Calibration of sampling equipment is as vital as calibration of
analytical equipment if meaningful data concerning ambient concentrations
of TOAP's are to be obtained. A QA plan for a TOAP monitoring program
will therefore address calibration of sampling equipment. Typically the
QA plan will include:
• Written calibration procedures.
e Calibration frequencies.
• Acceptable calibration quality.
e A statement of the appropriate environment in or conditions for
which the sampling equipment can be used.
• Provisions for proper record keeping of calibration data.
The QA plan will also address appropriate maintenance activities and
frequencies for sampling equipment, to ensure that it operates as
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planned. Additionally, the QA plan will address procedures to document
performance of maintenance activities on schedule.
7.4.3 Routine Quality Control Sample Collection
A QA plan for a TOAP monitoring project will include a provision for
the collection of a variety of quality control samples. Quality control
samples to check overall system performance may include replicate or split
samples, spiked samples, standard reference materials, blanks, and backup
snipes (e.g. series impingers or resin cartridges). Split or replicate
samples are useful checks on sampling and analysis precision and should be
included with each group of samples. Field blanks, in which the sampling
activity is duplicated exactly except that no air is sampled, should also
be routinely collected. Backup samples should be collected whenever the
recovery performance of a particular sampling medium has not been
documented or is subject to wide variations depending on ambient
conditions. Spiked samples should be included whenever an accurate
spiking procedure is available, provided that the spiked material
reasonably simulates the physical and chemical state of the native
material.
7.4.4 Sample Labeling, Preservation, Storage, and Transport
The data obtained from a TOAP monitoring program will be meaningless
if samples are improperly labeled or if preservation, storage, or
transport procedures are inappropriate for the required analyses. Sample
labeling, preservation, storage, and transport procedures will therefore
be specified in the QA plan, and these procedures should be carefully
explained to field personnel, prior to sampling, to ensure proper
implementation. Sample labels, prepared in advance, should include
sufficient information to associate a given sample with a particular data
sheet, as well as with the overall program record notebook. In general,
each sample should be given a unique identification number with a prefix
describing the type of sample.
7.4.5 Chain-of-Custody Procedure
Chain-of-custody procedures are used to document the movement of a sample
from collection until analysis, to ensure sample integrity. Formal chain-
of-custody requirements place a substantial burden on both field and
laboratory personnel. Chain-of-custody procedures must be documented in
the QA plan for a TOAP monitoring project and reviewed with the personnel
who will use them, to ensure that the data is fundamentally legally
defensible.
7.5 ANALYTICAL QUALITY ASSURANCE
The QA plan for the analytical component of a TOAP monitoring program
will address method validation requirements, instrument maintenance and
calibration, quality control sample analysis, and data recording. Each of
these aspects is discussed in the subsections that follow.
- 80 -
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7.5.1 Method Validation
Many TOAP monitoring programs will require the development of new or
modification of existing sampling and analytical protocols. It will be
necessary to establish the performance characteristics of these
procedures, prior to their use in TOAP monitoring programs. Performance
characteristics will include determination of precision, accuracy,
detection limit, and specificity through the analysis of laboratory
standards and, whenever possible, representative samples. The validation
requirements should be appropriate. The incorporation of SRM's in the
method validation process will prove cost effective and minimize the time
required to bring a new method on line. It is important to validate the
method in a manner that approximates as closely as possible the conditions
that will exist when actual samples are collected.
Performance criteria for existing, well documented methodologies must
also be validated when a procedure is used for the first time by the test
team. Validation of this type will require the development of a data base
sufficient to establish critical statistical parameters such as the
coefficient of variation. Again, SRM's are a key component of the method
validation process.
Finally, method validation procedures, such as the recovery of spiked
samples, should be integrated into the daily sampling and analysis
program. SRM's, IRM's, or CRS's are appropriate for this form of method
validation.
7.5.2 Instrument Calibration and Maintenance
Proper calibration of analytical instrumentation is fundamental to the
success of a TOAP monitoring program. The QA plan for a TOAP monitoring
program will therefore include a calibration plan for the various
analytical systems used on the project. The calibration plan will
include:
1. A statement of the maximum allowable time between multipoint
calibrations and calibration checks.
2. A statement of the minimum quality of calibration standards (e.g.
standards should have four to ten times the accuracy of the
instruments that they are being used to calibrate). A list of
calibration standards should be provided.
3. Provisions for standard traceability (e.g., standards should be
traced to NBS-SRM's or commercial Certified Reference Materials
[CRM's] if available).
4. Provisions for written procedures to help ensure that
calibrations are always performed in the same manner. The
procedures should include the intended range of validity.
5.
Statement of proper environmental conditions, to ensure that the
equipment is not significantly affected by its surroundings.
- 81 -
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6. Provisions for proper record keeping and record forma to ensure
that adequate documentation of calibrations is available for use
in internal data validation and in case the data are used in
enforcement, actions.
7. Documentation of qualifications and training of personnel
performing calibrations.
The QA plan will also address appropriate maintenance activities and
frequencies for analytical equipment. Additionally, the QA plan will
include procedures to document performance of maintenance activities on
schedule.
7.5.3 Quality Control Sample Analysis
A QA plan for a TOAP monitoring project will include provisions for
the analysis of a variety of quality control samples. Quality control
samples for evaluating analytical performance should include blanks,
spiked process blanks, spiked samples, standard reference materials, and
replicate (or split) samples. Standard reference materials and replicate
or split samples should generally be included as part of field QA and need
not be additionally included at the analysis stage. However, additional
blanks, spiked process blanks, and spiked samples should be included,
since this practice allows matrix effects to be distinguished from
analytical losses.
7.6 DATA MANAGEMENT
The QA plan for a TOAP monitoring program will include procedures
designed to ensure that required sampling and analytical data are captured
and maintained securely and efficiently. Data recording procedures that
should be specified in the sampling QA plan include (a) periodic reading
of the temperature, flow, volumes, and other parameters; (b) documentation
of meteorological conditions at appropriate time points; (c) documentation
of instrument operating variables; (d) documentation of any upset
conditions such as sudden leakage or pressure surges; and (e)
documentation of calibration or maintenance activities. A logbook for the
overall sampling program, in which sampling descriptions, meteorological
data, and upset conditions are documented, should be maintained. A data
sheet should also be prepared for each set of samples or analytical
procedure for which relevant raw data should be recorded. Certain
measurements, such as filter numbers and weights or impinger volumes,
which are required for analytical purposes can be recorded on a separate
sheet with provisions for recording subsequent analytical data on the same
sheet. Separate maintenance and calibration logbooks should be maintained
for each instrument. In most cases, specific sampling data forms for a
given program must be prepared because of differences in the sampling
design between programs.
The QA program for a TOAP monitoring project will address various
steps in the data reduction process including:
• Merging sampling and analytical data.
- 82 -
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• Storage of raw and intermediate data.
• Data validation.
Since sampling and analytical data processing occurs independently in
moat cases, the QA plan will address the manner in which data from the two
activities are to be treated and validated during the reduction process.
Because TOAP monitoring data can be collected over an extended period of
time and may involve several parties, it is important that the QA plan
address procedures for transferring and storing raw and intermediate
data. Finally, the data reduction component of the QA program will set up
data validation procedures so that appropriate data validation reports can
be prepared.
7.7 REPORTING QUALITY ASSURANCE
The report represents the final output of a TOAP monitoring program.
The QA plan will therefore incorporate appropriate review procedures to
ensure that the report properly summarizes the results of the study.
The report must be reviewed by individuals capable of recognizing
technical deficiencies and QA inconsistencies. The report should also be
reviewed by project personnel who were involved in data generation.
Finally, the report should be reviewed for editorial content, to, minimize
ambiguities.
- 83 -
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RZrUUENCKS
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American Public Health Association, Washington, D.C., 1977.
7. Riggin, R. M. Compendium of Methods for the Determination of Toxic
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10. Quality Assurance for Air Pollution Measurement Sy^tfllMr U.S.
Environmental Protection Agency, Research Triangle Park, North
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V. II Ambient Air Specific Methods, EPA-600/4-77-027a.
11 . Inter^n Guidelines and Specifications for Preparing Quality Assurance
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13. Lancre'g Handbook of Chemistry. McGraw-Hill Book Company.
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14. The Merck Index. Merck and Co., Rahway, New Jersey. (Published
Annually)
15. Handbook °f Environmental Data on Organic Chemicals. K. Verschueren,
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Shadwick. Intercomparison of Sampling Techniques for Toxic Organic
Compounds in Indoor Air. EPA/RTP, NC. EPA-600/4-87-008. U.S.
Environmental Protection Agency, Research Triangle Park, North
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17. Comparison of Tenax and Canister Sampling Techniques for Volatile
Organic Compounds in Ambient Air. Battelle Columbus Division. 1987.
18. Chuang, J. C., S. W. Hannan, and N. K. Wilson. Field Comparison
Study of Polyurethane Foam and XAD-2 Resin for Air Sampling of Poly
Aromatic Hydrocarbons. EPA, APCA Symposium on Measurement of Toxic
and Related Air Pollution. 1987.
19. DeRobs, F. L., J. E. Tabor, S. E. Miller, S. C. Watson, and J. A.
Hatchel. Evaluation of an EPA High-Volume Sampler for
Polychlorinated Dibenzo-p-dioxins and Polychlorinated Dibenzofurans.
EPA-600/4-86/037. U.S. Environmental Protection Agency/ Research
Triangle Park, North Carolina, 1987.
20. Lane, D. A. and D. M. A. McCurvin. A Personal Computer Database for
the Chemical, Physical and Thermodynamic Properties of the Polycyclic
Aromatic Compounds. EPA/APCA Symposium on Measurement of Toxic and
Related Air Pollutants, 1987. pp 341-43.
21. Clements, J. B. and R. 6. Lewis. Sampling for Organic Compounds.
EPA/600/p-87/052. U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina, 1987. p. 11.
22. Standard Practice for Application of the Hi-Vol Sampler method for
Collection and Mass Determination of Airborne Particulate Matter.
Annual Book of ASTM Standards. Amer. Soc. Test. Mater., Designation
D 4096-82, Phil., PA.
23. Phillips, J. B., J. R. Valentin and G. C. Carle. Large Volume
Sampling Without Preconcentration for Continuous Gas Chromatography.
Toxic Materials in the Atmosphere, ASTM STP, 786, 1982. pp. 135-141.
24. Reference 6, pp. 38-48.
25. Handy, R. W., H. L. Crist, and T. W. Stanley. Quality Assurance for
Personal Exposure Monitoring. ASTM Special Technical Publication No.
867, 1985.
26. Walling, J. F., J. E. Bumgarner, D. J. Driscoll, C. M. Morris, A. E.
Riley, and L. H. Wright. Apparent Reaction Products Desorbed from
Tenax Use to Sample Ambient Air. Atmos. Enviro., 20 (1). 1986. pp.
51-57.
- 85 -
-------
27. DRAFT EMSL/RTP Protocol. Sampling Air for Volatile Organic Compounds
Using Tenax.
28. Chuang, J. C., W. E. Bresler, and S. W. Hannan. Evaluation of
Polyurethane Foam Cartridges for Measurement of Polynuclear Aromatic
Hydrocarbons in Air. EPA-600/54-85/055. U.S. Environmental
Protection Agency, Research Triangle Park, 1985.
29. Coppi, S., A. Betti and M. Ascanelli. Styrene Copolymers as
Pollutant Adsorbents Safe Sampling Volume. J. Chromatog., 390. 1987.
pp. 349-355.
30. Williams, E. J., and R. E. Sievers. Synthesis and Characterization
of a New Sorbent for Use in the Determination of Volatile, Complex -
Farming Organic Compounds in Air. Anal. Chem. 56-1984. pp. 2523-
2528.
31. Kebbekus, B. B., and J. N. Bozzelli. Collection and Analysis of
Selected Volatile Organic Compounds in Ambient Air. Proc. Air
Pollution Control Assoc., Paper No. 82-65.2. Air Poll. Control
Association, Pittsburgh, Pennsylvania, 1982.
32. Holzer, 6., H. Shanfield, A. Zlatkis, W. Bertsch, p. Juarez, H.
Mayfield, and H. M. Liebich. Collection and Analysis of Trace
Organic Emissions from Natural Sources. J. Chromatog. 142, 1977.
pp. 755-764.
33. Reference 3 pp 156-158.
34. Cobb, 6. P., R. S. Braman, and K. M. Hua. Carbon Hollow Tubes as
Collectors in Thermal Resorption/Gas Chromatographic Analysis of
Atmospheric Organic Compounds. Anal. Chem., 58, 1986. pp. 2213-221.
35. Hawthorne, S. B., and D. J. Miller. Extraction and Recovery of
Organic Pollutants from Environmental Solids and Tenax-GC Using
Supercritical CO2- J. Chromato. Sci., 24. 1986. pp. 258-263.
36. Krasnec, J. P. Grab Sampling as an Effective Tool in Air Pollution
Monitoring. EPA, APCA Symposium on Measurement of Toxic and Related
Air Pollutants, RTP, NC., 1987.
37. Oliver, K. D., J. D. Pleil, and H. A. McClenny. Sample Integrity of
Trace Level Volatile Organic Compounds in Ambient Air Stored in
S ultima Polished Canisters. Atmos. Environ., 2Q (7), 1986. pp.
1403-1441.
38. Holden, M. W., D. L. Smith, and W. A. McClenny. A Prototype Sampler
for Preconcentration and Transferring Volatile Organic Compounds from
Ambient Air to Passivated Canisters. EPA, APCA Symposium on
Measurement of Toxic and Related Air Pollutants, RTP, NC., 1987.
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39. Holdren, M., S. Humrickhouse, S. Truitt, H. Westberg, and H. Hill.
Analytical Technique to Establish the Identity and Concentration of
Vapor Phase Organic Compounds. Proc. Air Poll. Control Assoc., Paper
No. 79-52.2, Air Pollution Control Association, Pittsburgh,
Pennsylvania, 1979.
40. McElroy, F. F., V. C. Thompson, and H. G. Richter. A Cryogenic
Preconcentration - Direct FID (PDFID) Method for Measurement of NMOC
in Ambient Air. EPA-600/4-85/063. U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina, 1985.
41. Reference 3, pp 152-154.
42. Fung, K., and D. Grosjean Determination of Nanogram Amounts of
Carbonyls as 2,4-Dinitrophenylhydrazones by HPLC. Anal. Chem. 53.
1981. pp. 168-171.
43. Kring, E. V. et. al. Pro-Tek Organic Vapor Air Monitoring Badges.
Toxic Materials in the Atmosphere, ASTM STP 786, 1982. pp. 85-103.
44. Brown, R. H., P. C. Cox, C. J. Purnell, N. G. West, and M. D.
Wright. The Application of Passive Sampling Techniques to the
Analysis of Specific Vapors in Air. In: Identification and Analysis
of Organic Pollutants in Air. L. H. Keith, ed., Ann Arbor Science,
1984. pp. 37-49
45. Levin, J. O, R. Lindahl, and K. Anderson. A Passive Sampler for
Formaldehyde in Air Using 2.4 - Dinitrophenylhydrazin-Coated Glass
Fiber Filters. Environ. Sci. Technol., 20, 1986. pp. 1273-1276.
46. Thompson, J. M. and W. I. Stephen. Comparison of Recoveries of
Trichloroethylene from Charcoal Tubes and Thermally-Desorbably
Personal Monitors. Anal. Chem. Acta., 182, 1986. pp. 299-302.
47. Tuan, Vo-Dinh. Development of a Dosimeter for Personnel Exposure to
Vapors of Polyaromatic Pollutants. Enviro. Sci. Tech., 19. 1985.
pp. 997-1003.
48. Reference 3, pp 3-47.
49. Reference 6, pp 191-205.
50. Kolak, N. P., and J. R. Visalli. Comparison of Three Methods for
Measuring Suspended Particulate Concentrations. Env. Sci. Tech, 15.
1981. pp. 219-224.
51. Mitchell, R. I., W. M. Henry, and N. C. Henderson. "Mega-volume
Respirable Particulate Sampler (Mark II)". Proc. Air Poll. Control
Assoc., Paper No. 77-35.1, Air Pollution Control Association,
Pittsburgh, Pennsylvania, 1977.
52. Colson, E. R. "Flame lonization Detectors and High-End Linearity."
Anal. Chem., 5_Ł, 1986. pp. 337-344.
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53. Lewis, R. G. Development of New Sampling and Analysis Techniques For
Hazardous Air Pollutants in Ambient and Indoor Air. Internal Report
FY-87 EMSL/RTP, NC.,^Dec. 1987.
54. Foreman, W. T. and T. F. Bidleman. An Experimental System for
Investigating Vapor-Particle Partitioning of Trace Organic
Pollutants. Environ. Sci. Technol., 21. 1987. pp. 869-875.
55. IERL-RTP Procedures Manual: Level 1 Environmental Assessment, 2nd
Edition, EPA 600/4-78-201. U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina, October 1978.
56. Reference 6, pp 184-186.
57. Ibid, pp 88-98.
58. Gas Chromatoaraphv with Glass Capillary Columns. Jennings, W., ed.,
Academic Press, New York, 1978.
59. Recent Advances in Capillary Gas Chromatoaraphv. Bertsch, W., G.
Jennings, and R. E. Kaiser, ed., Verlag, Heidelberg, 1981.
60. Cox, R. D., and R. F. Earp. Determination of Trace Level Organics in
Ambient Air by High Resolution Gas Chromatography with Simultaneous
Protoionization and Flame lonization Detection. Anal. Chem., 54.
1982. pp. 2265-2270.
61. Pellizari, E. D. Electron Capture Detection in Gas Chromatography.
J. Chrom., ŁŁ, 1974. pp. 323-361.
62. Freedman, A. N. Photoionization Detector Response. J. Chrom., 236.
1982. pp. 11-15.
63. McFaden, W. H. Techniques of Combined Gas Chromatoaraphv Masa
Spectrometrv. John Wiley and Sons, New York, 1973.
64. Lane, D. A. Mobile Mass Spectrometry. Env. Sci. Tech. 16. 1982.
pp. 38A-46A.
65. Burlingame, A. L., A. Dell, and D. H. Russel. Gas Chromatography
Mass Spectrometry. Anal. Chem. 54. 1982. pp. 363R-409R.
66. Krost, K., E. D. Pellizzari, S. G. Walbun, and S. A. Hubbard.
Collection and Analysis of Hazardous Organic Emissions. Anal. Chem.
M., 1982. pp. 810-818.
67. Introduction to Modern Liquid Chromatoaraphy. Snyder, L. R., and
J. J. Kirkland, 2nd Edition, John Wiley and Sons, New York, 1979.
68. Reference 6, pp. 248-256.
69. Ibid, pp 128-136.
- 88 -
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70. Ibid. pp 216-219.
71. Shafer, K. H., M.-Cooke, F. DeRoos, R. J. Jakobsen, O. Rosario, and
J. D. Mulik. WCOT Capillary Column GC/FT-IR and GC/MS for Identifying
Toxic Organic Pollutants. Applied Spectroscopy, 35. 1981. pp.
469-472.
72. Tuazon, E. C., A. M. Winer, R. A. Graham, and J. N. Pitts.
Atmospheric Measurements of Trace Pollutants by Kilometer-Pathlengths
FT-IR Spectroscopy. In Advances in Environmental Science and
Technology. 10. 1980. pp. 259-300.
- 89 -
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APPENDIX A
COMPOUNDS SUBJECT TO REGULATION UNDER THE
PROPOSED CLEAN AIR ATTAINMENT ACT OF 1987
TABLE l.A
CAS Number
Substance
75-07-0
60-35-5
67-64-1
75-05-8
53-96-3
107-02-8
79-06-1
79-10-7
107-13-1
309-00-2
107-05-1
7429-90-5
96-67-1
7664-41-7
62-53-3
90-04-0
104-94-9
7440-36-0
7440-38-2
1332-21-4
492-80-8
7440-39-3
71-43-2
92-87-5
50-32-8
98-07-7
94-36-0
100-44-7
7440-41-7
92-52-4
111-44-4
75-25-2
74-83-9
106-99-0
141-32-2
71-36-3
78-92-2
85-68-7
123-72-8
Acetaldehyde
Acetamide
Acetone
Acetonitrile
2-Acetylaminofluorene
(N-9H-fluoren-2-YL-acetamide)
Acrolein
Acrylamide
Acrylic acid
Acrylonitrile
Aldrin
Allyl chloride
Aluminum (fume or dust)
4-Aminobiphenyl
Ammonia
Aniline
o-Anisidine
P-Anisidine
Antimony (and compounds)
Arsenic (and compounds)
Asbestos (friable)
Auramine
Barium (and compounds)
Benzene
Benzidine
Benzo[a]pyrene
Benzoic trichloride
(Bensotrichloride)
Benzoyl peroxide
Benzyl chloride
Beryllium (and compounds)
Biph«nyl (Diphenyl)
rfxs (2-chloroethyl) ether
(2,2'-Dichloroethyl ether)
Bromoform (Tribromomethane)
Bromomethane (Methyl bromide)
1,3-Butadiene
Butyl acrylate
n-Butyl alcohol (1-Butanol)
sec-Butyl alcohol
Butyl benzyl phthalate
Butyraldehyde
- 90 -
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TABLE A.I
(CONTINUED)
CAS Number
Substance
7440-43-9
156-62-7
133-06-2
63-25-2
75-15-0
56-23-5
120-80-9
133-90-4
57-74-9
76-13-1
7782-50-5
10049-04-4
79-11-8
532-27-4
108-90-7
510-15-6
75-00-3
67-66-3
74-87-3
542-88-1
107-30-2
126-99-8
7440-47-3
7440-48-4
7440-50-8
1319-77-3
108-39-4
95-48-7
106-44-5
98-82-8
57-12-5
110-82-7
94-75-7
72-55-9
25376-45-8
95-80-7
119-90-4
334-88-3
132-64-9
Cadmium (and compounds)
Calcium cyanamide
Captan
Carbaryl
Carbon disulfide
Carbon tetrachloride
Catechol (Pyrocatechol)
Chloramben
Chlordane
Chlorinated fluorocarbon
(Freon 113)
Chlorine
Chlorine dioxide
Chloroacetic acid (Assistacetic
acid)
2-Chloroaceto phenone
(a-Chloroacetophenone)
Chlorobenzene
Chlorobenzilate (Ethyl
4-4'-dichlorobenzilate)
Chloroethane (Ethyl Chloride)
Chloroform
Chloroir.ethane (Methyl chloride)
Chloromethyl ether
Chloromethyl methyl ether
Chloroprene
Chromium (and compounds)
Cobalt (and compounds)
Copper (and compounds)
Cresol (mixed iaomers)
m-Cresol
o-Cresol (o-Cresyl acid)
p-Cresol
Cumene (1-Methylbenzene)
Cynanide compounds
Cyclohexane (Hexahydrobenzene)
2,4-D ( (2,4-Dichlorophenoxy)
Acetic acid)
DDE
Diaminotoluene (mixed isomers)
2,4-Diaminotoluene
0-Dianisidine
(3.3'-Dimethoxybenzidene)
Diazomethane
Dibenzofuran
- 91 -
-------
TABLE A.I
(CONTINUED)
CAS Number
96-12-8 1,2-Dibromo-3-chloropropane
(DBCP)
106-93-4 1,2-Dibromoethane (Ethylene
dibromide)
84-74-2 Dibutyl phthalate
25321-22-6 Dichlorobenzene (mixed isomers)
95-50-1 1,2-Dichlorobenzene
(o-Dichlorobenzene)
106-46-7 1,4-Dichlorobenzene
(p-Dichlorobenzene)
91-94-1 3,3'-Dichlorobenzidine
75-71-8 Dichlorofluoromethane
75-34-3 1,1-Dichloroethane
107-06-2 1,2-Dichloroethane (Ethylene
Dichloride)
540-59-0 1,2-Dichloroethylene (Acetylene
dichloride)
75-09-2 Dichloromethane (Methylene
Chloride)
78-87-5 1,2-Dichloropropane
542-75-6 1,3-Dichloropropylene
(1,3-Dichloropropene)
62-73-7 Dichlorvos
115-32-2 Dicofol (Kelthane)
60-57-1 Dieldrin
111-42-2 Diethanolamine
117-81-7 Di(2-Ethylhexyl) phthalate
(DEHP)
84-66-2 Diethyl phthlate (1,2-Diethyl
ester 1,2-benzene dicarboxy)
64-67-5 Diethyl sulfate
60-11-7 4-Dimethylaminoazobenzene
(p-Dimethylaminoazobenzene)
121-69-7 N, N-Dimethylaniline
119-93-7 3.3'-dimethylbenzidine
(o-Tolidine)
79-44-7 Dimethylcarbamyl chloride
57-14-7 1,1-Dimethyl hydrazine
(Dimethyldydrazine)
131-11-3 Dimethyl phthalate
77-78-1 Dimethyl sulfate
534-52-1 4,6-Dinitro-o-cresol
(Dinitrocresol)
51-28-5 2,4-Dinitrophenol
- 92 -
-------
TABLE A.I
(CONTINUED)
CAS Number
Substance
121-14-2
123-91-1
122-66-7
106-89-8
110-80-5
140-88-5
100-41-4
74-85-1
107-21-1
151-56-4
75-21-8
96-45-7
50-00-0
76-44-8
118-74-1
87-68-3
77-47-4
67-72-1
1335-87-1
680-31-9
302-01-2
7647-01-1
74-90-8
7664-39-3
123-31-9
78-59-1
67-63-0
7439-92-1
58-89-9
108-31-6
7439-96-5
51-75-2
108-78-1
7439-97-6
67-56-1
72-43-5
2,4-Dinitrotoluene (l-Methyl-2,
4-Dinitrobenzene)
1,4-Dioxane (1,4-Diethylene
dioxide)
1,2-Diphenyl hydrazine
(Hydrazobenzene)
Epichlorohydrin
2-Ethoxyethanol
Ethyl acrylate
Ethyl benzene
Ethylene
Ethylene glycol
Ethyleneimine (Azindine)
Ethylene oxide
Ethylene thiourea
Formaldehyde
Heptachlor
Hexachlorobenzene
Hexachloro-1,3-butadiene
Hexachlorocyclopentadiene
Hexachloroethane
Hexachloronaphthalene
Hexamethylphosphoramide
Hydrazine
Hydrochloric acid (Hydrogen
chloride [gas only])
Hydrogen cyanide (Hydrocyanic
acid)
Hydrogen fluoride
Hydroquinone
Isophorone
Isopropyl alcohol (Mfg.-strong
acid processes)
Lead (and compounds)
Lindane (Hexachlorocyclohexane)
Maleic acid anhydride
(2,5-Furandione)
Manganese (and compounds)
Mechlorethamine (Nitorgen
mustard)
Melamine
Mercury (and compounds)
Methanol
Methoxychlor
(1,1,l-Trichloro-2,2-Bis
[P-Methoxyphenyl] ethyl)
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TABLE A.I
(CONTINUED)
CAS Number
Substance
109-86-4
96-33-3
101-14-4
101-68-8
101-77-9
78-93-3
60-34-4
74-88-4
108-10-1
624-83-9
80-62-6
91-20-3
134-32-7
91-59-8
7440-02-0
7697-37-2
98-95-3
92-93-3
1836-75-5
55-63-0
100-02-7
79-46-9
62-75-9
684-93-5
59-89-2
2234-13-1
20816-12-0
56-38-2
87-86-5
108-95-2
106-50-3
75-44-5
7664-38-2
7723-14-0
85-44-9
88-89-1
2-Methoxyethanol (Methyl
cellosolve)
Methyl acrylate
4,4'-Methylene bis
(2-Chloroaniline) (MOCA)
Methylene bis(Phenylisocyanate)
(MB I)
4,4'-Methylene dianiline
(p,p'-diaminodiphenylmethane)
Methyl ethyl ketone (MEK)
2-Butanone)
Methyl hydrazine
Methyl iodide (lodomethane)
Methyl isobutyl ketone (MIBK)
(Isopropylacetone) (Hexone)
Methyl isocyanate
Methyl methacrylate
Naphthalene
alpha-Naphthylamine
beta-Naphthylamine
(2-Naphthylamine)
Nickel (and compounds)
Nitric acid
Nitrobenzene
4-Nitrobiphenyl
Nitrofen
Nitroglycerin
4-Nitrophenol
2-Nitropropane
N-Nitrosodimethylamine
N-Nitroso-N-methylurea
(N-methyl-N-nitrosocarbamide)
N-Nitrosomorpholine
Octachloronaphthalene
Osmium tetroxide
Parathion
Pentachlorophenol (PCP)
Phenol
p-Phenylenediamine
Phosgene
Phosphoric acid
Phosphorus (yellow or white)
Phthalic anhydride (1,2 Benzene
dicarboxylac acid anhydride)
Picric acid
- 94 -
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TABLE A.I
(CONTINUED)
CAS Number
Substance
1336-36-3
1120-71-4
57-57-8
114-26-1
75-55-8
75-56-9
110-86-1
91-22-5
106-51-4
82-68-8
7782-49-2
7440-22-4
1310-73-2
100-42-5
96-09-3
7664-93-9
100-21-0
1746-01-6
79-34-5
127-18-4
7440-28-0
13463-67-7
108-88-3
584-84-9
95-53-4
8001-35-2
120-82-1
71-55-6
79-00-5
79-01-6
95-95-4
88-06-2
1582-09-8
51-79-6
7440-62-2
108-05-4
Polychlorinated biphenyls
(VCB's)
Propane sultone (2,2-dioxide
1,2-oxathiolane)
beta-Propiolactone
Propoxur
Propyleneimine
Propylene oxide
Pyridine
Quinoline
Quinone (p-Benzoquinone)
Quinotozene
(Pentachloronitrobenzene)
Selenium
Silver (and compounds)
Sodium hydroxide (solution)
Styrene (monomer)
Styrene oxide
Sulfuric acid
Terephthalic acid
2,3,7,8-Tetrachlorodibenzo-p-Di-
oxin (TCDD)
1,1,2,2-Tetrachlorethane
Tetrachloroethylene
(Perchloroethylene)
Thallium (and compounds)
Titanium dioxide
Toluene (Methyl benzene)
Toluene-2,4-Diisocyanate
o-Toluidine
Toxaphene (Camphechlor)
1,2,4-Trichlorobenzene
1,1,1-Trichlorethane (Methyl
chloroform)
1,1,2-Trichloroethane
Trichloroethylene
(Trichloroethene)
2,4,5-Trichlorophenol
2,4,6-Trichlorophenol
Trifluralin
Urethane (monomer) (Ethyl
ester carbamic acid)
Vanadium (fume or dust)
Vinyl acetate
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TABLE A.I
(CONTINUED)
CAS Number Substance
593-60-2 Vinyl bromide
75-01-4 Vinyl chloride (monomer)
(Chloroethane)
75-35-4 Vinylidine chloride
(1,1-Dichloroethylene)
1330-20-7 Xylene (mixed isomers)
(Dimethyl benzene)
108-38-3 m-Xylene (m-Dimethyl benzene)
95-47-6 o-Xylene (o-Dimethyl benzene)
106-42-3 p-Xylene (p-Dimethyl benzene)
7440-66-6 Zinc (fume or dust) (and
compounds)
- 96 -
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APPENDIX B
B.I Method TO-1
Method TO-1 is suitable for the determination of certain nonpolar
volatile organic compounds (VOC's) having boiling points in the range of
80' - 200* C. An ambient air sample is drawn through a cartridge
containing Tenax . The analytical detection limit varies with the
analyte. Detection limits of 1-200 pptv are achievable using a 20L
sample.
Certain VOC's are trapped on the tenax while highly volatile organic
compounds and most inorganic atmospheric constituents pass through the
adsorbent. The cartridge is sealed and returned to the laboratory for
thermal desorption and subsequent GC/MS analysis. Mass spectrometry is
not necessarily required if it can be documented that satisfactory results
can be obtained with an FID or BCD.
Contamination of the Tenax cartridge is a common problem with the
method. Caution must be exercised during all operations to minimize
contamination of the Tenax.
Breakthrough of analytes is another common problem. Backup cartridges
must be used, and distributed air volume sampling techniques are
recommended.
B.2 Method TO-2
Method TO-2 is suitable for the determination of certain nonpolar
volatile organic compounds having boiling points in the range of -15* to
120' C. The analytical detection limit varies with the analyte.
Detection limits of 0.01-1 ppbv are achievable using a 20L sample.
An ambient air sample is drawn through a cartridge containing a carbon
molecular sieve adsorbent. Volatile organic compounds are retained by the
adsorbent while major inorganic atmospheric constituents pass through. The
cartridge is sealed and returned to the laboratory for analysis. Prior to
analysis, the cartridge is purged with pure, dry air to remove adsorbed
moisture. Following the dry air purge, the cartridge is heated and then
purged with helium. Organic compounds are desorbed during this process
and subsequently collected in a cryogenic trap. The collected organics
are then flash evaporated into a capillary column GC/MS system for
identification and quantification.
Contamination of the carbon molecular sieve is a common problem with
the method. Caution must be exercised during all operations to minimize
contamination of the adsorbent.
Breakthrough of analytes is another common problem. Backup cartridges
must be used, and distributed air volume sampling techniques are
recommended.
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B.3 Itothod TO-3
Method TO-3 is suitable for the determination of certain highly
volatile compounds having boiling points in the range of -10* to 200* C.
The analytical detection limit varies widely with the analyte and the
detector system. Detection limits in the low ppbv can be achieved with
certain hydrocarbons, using an FID and a 20L sample. Lower detection
limits are achievable with an ECD.
An ambient air sample is drawn through a collection trap submerged in
either liquid oxygen or, preferably, liquid argon. The collection trap is
plumbed to a gas chromatograph through a rotary, multi-port sampling
valve. Following sample collection, the multi-port valve is switched so
that carrier gas sweeps the contents of the trap onto the head of a cooled
(-50*) GC column. Simultaneously, the liquid cryogen is removed, and the
trap is heated to aid in the transfer of sample contents from the trap to
the head of the GC column. The GC column is temperature programmed to
yield the desired chromatographic separation. Compounds eluting from the
column are then quantified using an FID or an ECD.
This method has two significant limitations. First, compounds having
similar retention times will co-elute, making determination of a compound
of interest difficult. This problem can be minimized by using selective
detection systems and appropriate columns. Secondly, condensation of
moisture can result in ice plugging of the trap or GC column. Permeation
dryers have been used to reduce moisture problems; however, compounds of
interest can be lost with permeation dryers, and permeation dryers can be
a source of organic contaminants.
B.4 Mtethod TO-4
Method TO-4 is suitable for the determination of a variety of
organopesticides and polychlorinated biphenyls in ambient air. Because
the high volume sampler operates at a very high flow rate (200-280
L/minute) and because the ECD is a highly sensitive detector, it is
possible to detect very low ambient concentrations of PCB's and
organopesticides, using this procedure. Detection limits of less than 1
ng/m are achievable during a 24-hour sampling period.
An ambient air sample is collected with a modified high volume sampler
consisting of a glass fiber filter with a polyurethane foam (PUF) backup
adsorbent cartridge. The glass fiber filter and PUF cartridge are
returned to the laboratory for analysis. The PCS's and pesticides are
recovered by Soxhlet extraction, using 5% ether in hexane. The extracts
are concentrated by Kuderna-Danish techniques and cleaned up using column
chromatography. The resulting extracts are then analyzed for pesticides
and PCB's, using gas chromatography with electron capture detection in
accordance with U.S. EPA Method 608.
Organochlorine pesticides and PCB's are complex mixtures of individual
compounds, and it can be very difficult to quantify a specific constituent
of a multicomponent mixture. Contamination of glassware and sampling
equipment is a common problem, and care should be taken to minimize
contamination during equipment cleaning and handling .
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B.5 Method TO-5
Method TO-5 is suitable for the determination of certain individual
aldehydes and Jcetones in ambient air. With proper attention to reagent
purity, the method can detect most monofunctional aldehydes and ketones at
the 1-2 ppbv level.
Ambient air is drawn through a midget impinger containing 10 ml of
0.05% 2,4 - dinitrophenylhydrazine (DNPH) in 2N Hcl and 10 mL of
isooctane. Aldehydes and ketones react with the DNPH to form stable 2,4 -
dinitrophenylhydrazones (DNPH derivatives). The impinger contents are
transferred to a screw cap vial and returned to the laboratory. The
isooctane layer is removed, and the aqueous layer is extracted with
hexane/methylene chloride. The extract is then recombined with the
previously removed isooctane and evaporated to dryness under a stream of
nitrogen. The residue is dissolved in methanol and analyzed using
reversed phase HPLC with an ultraviolet absorbance detector operating at
370 nm.
Isomeric aldehydes and ketones may be unresolved by the HPLC system
and may cause quantification and identification problems. Careful
attention should therefore be given to selection of the separation column
and mobile phase. Formaldehyde and acetone contamination of the DPNH
reagent are common problems. Acetone contamination is unavoidable, and
the method is not suitable to the determination of acetone. Formaldehyde
contamination problems can be minimized by using fresh reagents (<48 hours
old) and storing the DNPH reagent in an uncontaminated environment.
B.6 Method TO-6
Method TO-6 is suitable for the determination of phosgene in ambient
air. The analytical detection limit is approximately 0.1 ppbv.
Ambient air is drawn through a midget impinger containing 10 ml of
2/98 aniline/toluene (v/v). the phosgene reacts with aniline to form 1,3
- diphenylurea. The impinger contents are transferred to a screw-cap vial
and returned to the laboratory for analysis. The Vial is placed on a
heater block, and the liquid is evaporated under a stream of nitrogen.
The residue is dissolved in acetonitrite, and the 1,3 - diphenylurea is
analyzed using reverse-phase HPLC with a UV absorbance detector operating
at 254 nm.
There are few interferences with this method. Chloroformates can
react with aniline to form urea which coelutes with the 1,3 - diphenylurea
and is detectable by UV. Reagent purity is an important consideration
because traces of 1,3 - diphenylurea have been found in reagent grade
aniline.
B.7 Method TO-7
Method TO-7 ia suitable for the analysis of N-nitrosodimethylamine in
ambient air. Analytical detection limits of lug/m are achievable using
GC/MS.
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Ambient air is drawn through a cartridge containing Thermo3orb/N
adsorbent. The cartridges are returned to the laboratory and pre-eluted
with 5 mL of dichloromethane (in same direction as sample flow). Residual
dichloromethane is removed by purging the cartridge with air in the
direction of sample flow. The cartridges are then eluted in reverse
direction with 2 mL of acetone. The N-nitrosodimethylamine is then
determined by GC/MS.
Breakthrough of N-nitrosodimethylamine is apparently not a problem
with flow rates of approximately 2L/minute and sample volumes of 300L.
Compounds having similar retention times and yielding detectable m/e 74
ion fragments may interfere with the method. These problems are minimized
by the pre-elution step.
B.8 Method TO-8
Method TO-8 is suitable for the analysis of phenol and cresols
(methylphenols) in ambient air. Analytical detection limits of 1-5 ppbv
are readily achievable.
Ambient air is drawn through a series of two midget impingers, each
containing 15 mL of 0.1 N NaOH. The phenols and methylphenols are trapped
as phenolates. The impinger contents are transferred to a screw cap vial
and returned to the laboratory for analysis. The solution is cooled in an
ice bath and adjusted to a pH of less than 4 by the addition of 1 ml 5%
H2SO4 (v/v)• The sample volume is adjusted to 25 mL with distilled
water, and an aliquot is removed for analysis by reverse-phase HPLC.
Electrochemical detection, fluorescence detection, or ultraviolet
detection (254 ran) can be used, depending on sample cleanliness.
Compounds that co-elute with compounds of interest will interfere with
the method. Column and mobile phase selection are, therefore, important
considerations. Phenolic compounds of interest may be oxidized during
sampling; consequently, appropriate validation experiments are in order.
B.9 Mathod TO-9
Method To-9 is suitable for the delamination of a variety of
polychlorinated dibenzo-p-dioxins (PCDD's) in ambient air. Detection
limits below 15 pg/m are readily achievable.
Ambient air is drawn through a glass fiber filter and a polyurethane
foam (PUF) adsorbent cartridge by means of a high volume sampler.
Following sample collection, the filter and the PUF cartridge are removed
and returned to the laboratory for analysis. The filter and PUF cartridge
are extracted using benzene. The extract is concentrated using
Kuderna-Danish technique, diluted with hexane, and cleaned up using column
chromatography. The cleaned extract is then analyzed by high resolution
gas chromatography/high resolution mass spectrometry.
This method is very complicated and subject to a variety of
interferences. Chemicals that co-elute with compounds of interest and
produce similar m/e ratios will interfere with quantification and
identification. Reagent purity and glassware cleanliness are of utmost
- 100 -
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importance because of the very low levels of PCDD's that are being
analyzed.
B.10 Method TO-10
Method TO-10 is suitable for the determination of a variety of
organopesticides in ambient air. The analytical detection limit varies
with the analyte, sample volume, and detector used.
An ambient air sample is drawn through a polyurethane foam (PUF)
sorbent cartridge at one to five L/minute. The PUF cartridge is returned
to the laboratory for recovery of the pesticides by Soxhlet extraction
with five percent diethyl ether in hexane. The extract is concentrated
using Kuderna-Danish techniques and cleaned up using column chromatography
techniques. The resulting extract is then analyzed for pesticides, using
gas chromatography with electron capture detection. HPLC with UV
detection may be preferable for certain pesticides.
Organochlorine pesticides are complex mixtures of individual
compounds, and it can be difficult to quantify a specific constituent of a
multicomponent mixture. As with any chromatographic technique, co-elution
of interferents can be a problem.
B.ll Method TO-11
Method TO-11 is suitable for the determination of formaldehyde in
ambient air. This method can be used for either long- or short-term
sampling periods. The analytical detection limit varies with sample
volume; detection limits in the one to 20 ppb range are achievable with
sample volumes of approximately 750 liters.
An ambient air sample is drawn through a user-prepared cartridge
containing 2,4-dintrophenylhydrazine (DNPH)-coated silica gel at a flow
rate of 500-1200 mL/minute. The cartridges are returned to the laboratory
in screw-cap glass vials. The cartridges are then removed from the vials
and washed with acetonitrile by gravity feed elution. The eluate is
diluted volumetrically and an aliquot is removed for determination of the
DNPH-formaldehyde derivative by isocratic reverse phase HPLC with UV
detection at 350 nm.
Formaldehyde contamination of the DNPH reagent is common and will
obscure results if appropriate blank determinations are not made. As with
any chromatographic procedure, co-elution of interferents can be a
problem.
B.12 Method TO-12
Method TO-12 is suitable for the determination of a variety of
non-methane organic compounds (NMOC) in ambient air. Detection limits in
the low PPB's are achievable for many compounds.
This method permits the use of two sampling procedures: A whole air
sample is either extracted directly from the ambient air and analyzed on
site by the GC system or collected into an evacuated sample canister and
analyzed off site.
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A fixed-volume portion of the sample air is drawn through a glass-bead
filled trap cooled with liquid argon to approximately -186'C. The
cryogenic trap simultaneously collects and concentrates the NMOC (either
via condensation or adsorption) while allowing the methane, nitrogen,
oxygen, etc. to pass through the trap without retention. The system is
dynamically calibrated so that the volume of sample passing through the
trap does not have to be quantitatively measured but must be precisely
repeatable between the calibration and the analytical phases. After the
fixed-volume air sample has been drawn through the trap, a helium carrier
gas flow is diverted to pass through the trap, in the opposite direction
to the sample flow, and into an FID. When the residual air and methane
have been flushed from the trap and the FID base line restabilizes, the
cryogen is removed and the temperature of the trap is raised to
approximately 90*C to revolatize the NMOC's. The revolatized NMOC's are
flushed from the trap via carrier gas flow and discharged onto the
chromatographic column where separation occurs.
B.13 Method TO-13
Method TO-13 is suitable for the analysis of polynuclear aromatic
hydrocarbons in ambient air, using either GC or HPLC. At the time of the
TAD publication, Method TO-13 had not been formally published.
B.14 Method TO-14
Method TO-14 is suitable for the analysis in ambient air of VOC's and
SVOC's which have been tested and determined to be stable when stored in
pressurized and subatmospheric canisters. The detection limit varies with
the analyte, but PPB levels are readily achievable.
Both subatmospheric and pressurized sampling modes use an initially
evacuated canister and a sample line purge vacuum pump for sample
collection. Pressurized sampling requires an additional pump (metal
bellows type) to provide positive pressure in the sample canister. A
sample of ambient air is drawn into a sampling train comprised of an
initially evacuated canister and various components that regulate the rate
and duration of sampling and provide sample integrity.
After the air sample is collected, the canister valve is closed: an
identification tag is attached to the canister, and the canister is then
shipped to a predetermined laboratory for analysis. Upon receipt at the
laboratory, the canister tag data are recorded in a dedicated logbook, and
the canister is attached in-line to the analytical system.
In preparation for analysis, the VOC's are concentrated by
condensation in a cryogenic trap. The cryogen is removed, and the
temperature of the trap is raised. The VOC's originally collected in the
trap are revolatilized and carried to the GC column for VOC speciation
followed by multi-detector quantitation.
Each sample is analyzed by the following instrumentation and
procedures:
I. gas chromatoaraohy-flame ionization detector and electron capture
detector (GC-FID-ECD)
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2. qfta chromatoaraphv—mjfss selective detector~scan (GC-MSD-SCAN1
3. aaa ehromatoaraphv-inasa selective detector-selected ion monitoring
(GC-MSD-SIM)
Preliminary identification of VOC species in the sample (including any
polar compounds present) is provided by the FID and BCD analyses.
Positive identification of VOC species is provided by the gas
chromatograph in the SCAN mode. Polar compounds are not identified by the
MSD-SCAN analyses, because a Nafion tube dryer is used to remove water
from the sample, prior to MSD analysis. Preliminary quantitation of the
targeted VOC's is performed by the MSD-SIM analyses.
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APPENDIX C
GLOSSARY
Abaorbance: The logarithm to the base of 10 of the reciprocal of
transmittance.
Accuracy: The degree to which a measured value agrees with the true or
accepted reference value (e.g. pollutant concentration), usually expressed
as the percentage of the true or reference value represented by the
difference between the two (true and measured) values.
Acidic compound: A compound which dissociates in water to form a
hydrogenion (proton) and the corresponding anion (for example, acetic acid
dissociates into a hydrogen ion and the acetate anion).
Adsorbate: Material that has been retained by the process of adsorption.
Adsorbent: Solid material on the surface of which adsorption takes place.
Adsorption: A physical process in which molecules of gas, of dissolved
substances, or of liquids adhere in an extremely thin layer to the surfaces
of solid bodies with which they are in contact.
Aarosol: A dispersion of solid or liquid particles in gaseous media.
Air at normal condition* (standard air): Air at 50 percent relative
humidity, 70*F and 29.92 in. Hg (21'C and 760 mm Hg). These conditions are
chosen in recognition of the data which have been accumulated on
air-handling equipment. They are sufficiently near the 25*C and 760mm Hg
commonly used for indoor air contamination work that no conversion or
correction ordinarily need be applied.
Air pollution: The presence of unwanted material in the air. The term
"unwanted material" here refers to material in sufficient concentrations,
present for a sufficient time, and under circumstances to interfere
significantly with comfort, health, or welfare of persons or with the full
use and enjoyment of property.
Aliquot: A representative portion of the whole.
Alkali flame detector (ATD): See nitrogen phosphorus detector.
Atmosphere, an: A unit of pressure equal to the pressure exerted by a
vertical column of mercury 760 mm high, at a temperature of O'C, and under
standard gravity.
Atmosphere, synthetic: A specific gaseous mass containing any number of
constituents and in any proportion produced by man for a special purpose.
Atmosphere, the: The whole mass of air surrounding the earth and composed
largely of oxygen and nitrogen.
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Basic compounds: Compounds which protonate (add a hydrogen ion) in water
to form a cation (e.g. amines).
Breathing zone: That location in the atmosphere at which persons breathe.
Bubbler: A sampling device consisting of a gas disperser immersed in an
absorbing liquid.
Bubbler, fritted: A bubbler having a frit as the gas disperser.
Calibration: Establishment of a relationship between the responses of a
measurement system obtained by introducing various calibration standards
into the system. The calibration levels should bracket the range of levels
for which actual measurements are to be made.
Chemiluminescence detection: The measurement of emitted visible or
ultraviolet radiation resulting from the reaction of a pollutant with a
reactive gas (for example, detection of nitric oxide by reaction with
ozone).
Column chromatography: A separation technique wherein the stationary
phase is a solid (e.g. silica gel) and the mobile phase is a liquid, usually
an organic solvent or mixture of solvents. The technique is usually
performed using a tubular column operating an ambient pressure and is most
commonly used for the removal of potential interferences, prior to
determination of the compound of interest.
Collection efficiency: The percentage of a specified substance retained
by a gas cleaning or sampling device.
Colorimeter: An instrument used for color measurement based on optical
comparison with standard colors.
Condensate: Liquid or solid matter formed by condensation from the vapor
phase. In sampling, the term is applied to the components of an atmosphere
which have been isolated by simple cooling.
Condensation: The process of converting a material in the gaseous phase
to a liquid or solid state by decreasing temperature, by increasing
pressure, or both. Usually in air sampling, only cooling is used.
Contaminant: A material added by human or natural activities which may,
in sufficient concentrations, render the atmosphere unacceptable.
Cryogenic collection (trapping): A sampling process wherein an air sample
is passed through a cooled trap (usually using liquid argon or material
similar to the cryogen) to collect organic compounds.
Density: The mass per unit volume of substance.
Derivatization: A sampling and analysis process wherein a compound to be
monitored is converted to another more stable and/or readily detectable
compound via chemical reaction during the sampling or analysis step.
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Desorption: The process of freeing from a sorbed state.
Detection limit: The minimum quantity of a compound which yields a
"measureable response." Many statistical definitions of "measureable
response" are in use. One must be careful to differentiate "instrumental
detection limit," which refers to the minimum quantity of detectable
material introducible into a measurement system from "method detection
limit" which refers to the minimum concentration of compound in the sample
which, when carried through the entire sampling and analysis process, can be
detected.
Diffusion, molecular: A process of spontaneous intermixing of different
substances, attributable to molecular motion and tending to produce
uniformity of concentration.
Dispersion: The most general term for a system consisting of particulate
matter suspended in air or other gases.
Diurnal: Recurring daily. Applied to air contaminants, diurnal indicates
variations (in concentration) that follow a distinctive pattern and which
recur from day to day.
Droplet: A small liquid particle of such size and density as to fall
under still conditions but which may remain suspended under turbulent
conditions.
Dust: A term loosely applied to solid particles predominantly larger than
colloidal and capable of temporary suspension in air or other gases. Dusts
do not tend to flocculate except under electrostatic forces; they do not
diffuse but settle under the influence of gravity. Derivation from larger
masses through the application of physical force is usually implied.
Efficiency: A measure of the performance of a collector. Usually it is
the ratio of the amount collected to the inlet loading, expressed in
percentage.
Efficiency, fractional: The mean collection efficiency for specific size
fractions of a contaminant. Commonly this term has been applied to the
performance of air cleaning equipment toward particulate matter in various
size ranges.
Electron capture detector (ECD): A detection device for gas
chromatography which responds sensitively and selectively to electron
deficient (e.g. halogenated, nitrosubstituted) compounds.
Elute: To remove sorbed materials from a sorbent by means of fluid.
Emissions: The total of substances discharged into the air from a stack,
vent, or other discrete source.
Filter: A porous medium for collecting particulate matter.
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Filter, controlled pore: A filter of various plastics or metals having a
structure of controlled uniform pore size. Sometimes referred to as a
membrane or molecular filter.
Flame ionixation detector (FID): A detection device for gas
chromatography which responds to most organic compounds.
Flame photometric detector (FPD): A detection device for gas
chromatography which responds selectively to sulfur- and phosphorous-
containing compounds.
Flowmeter: An instrument for measuring the rate of flow of a fluid moving
through a pipe or duct system. The instrument is calibrated to give either
volume or mass rate of flow.
Fluorescence •pectrcmetery: The measure of ultraviolet or visible
radiation emitted by a compound after excitation with radiation of a lower
wavelength. The technique is widely used for the determination of
polynuclear aromatic hydrocarbons.
Fly ash: The finely divided particles of ash entrained in flue gases
arising from the combustion of fuel. The particles of ash may contain
incompletely burned fuel. The term has been applied predominantly to the
gas-born ash from a boiler with a spreader stoker, an underfeed stoker, and
pulverized fuel (coal) firing.
Fog: A term loosely applied to visible aerosols in which the dispersed
phase is liquid. Formation by condensation is usually implied. In
meteorology, a dispersion of water or ice.
Fractionation: The process of separating a mixture into components having
different properties (as by distillation, precipitation, or screening).
Freezing out: See sampling, condensation, or cryogenic collection.
Frit: A porous material permeable to gas flow usually made by sintering
microbeads of an appropriate material.
Fume: Properly, the solid particles generated by condensation from the
gaseous state, generally after volatilization from melted substances, and
often accompanied by a chemical reaction such as oxidation. Fumes
flocculate and sometime coalesce. Popularly, the term is used in reference
to any or all types of contaminant and, in many laws or regulations, with
the added qualification that the contaminant have some unwanted action.
Gas: One of the three states of aggregation of matter, having neither
independent shape nor volume and tending to expand indefinitely.
Gas chromatography (GC): A separation technique for organic compounds
wherein the stationary phase is a solid, liquid coated on a solid, or liquid
coated or bonded to the interior column wall (capillary column) and the
mobile phase is an inert gas.
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Gas meter: An instrument for measuring the quantity of a gas passing
through the meter.
Grab sample: See sampling, instantaneous.
Gustiness: Now referred to as intensity of turbulence, which is defined
as the ratio of the root mean square of wind velocity fluctuations to the
mean wind velocity.
Hall electrolytic conductivity detector (HBCD): A detection device for
gas chromatography which responds selectively to halogenated, sulfur
containing compounds or to nitrogen containing compounds (depending on
operating mode selected).
Halogenated compound: A compound containing chlorine, bromine, or iodine.
High performance liquid chromatography (HPLC): A separation technique
wherein the mobile phase is a liquid and the stationary phase is a solid,
usually having a particle diameter of 10 urn or less. HPLC is similar to
column chromatography, except that small particle diameter stationary phases
and high pressures are used to achieve faster analysis and greater
resolution.
Impaction: A forcible contact of particles of matter; a term often used
synonymously with impingement.
Impactor: A sampling device that employs the principle of impaction
(impingement). The "cascade impactor" refers to a specific instrument which
employs several impactions serially to collect successively smaller sizes of
particles.
Impingement: The act of bringing matter forcibly into contact. As used
in air sampling, impingement refers to a process for the collection of
particulate matter in which the gas being sampled is directed forcibly
against a surface.
Impinger: See bubbler.
Internal standard: A known quantity of a reference compound added to a
collected sample for use in the quantification of other compounds.
Inversion: A reversal of the normal atmospheric temperature gradient,
thus an increase of air temperature with increasing altitude.
Ionic or ioniiable compound: A compound which dissociates in water to
give ionic species (i.e. acidic or basic compounds).
Isokinetic: A term describing a condition of sampling, in which the flow
of gas into the sampling device (at the opening or face of the inlet) has
the same flow rate and direction as the ambient atmosphere being sampled.
Laps* rate: The rate of change of the absolute value of any
meteorological element with increase of height. (When used without a
modifier, it refers to the rate of decrease of temperature with increase of
height).
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Mass concentration: Concentration expressed in terms of mass of substance
per unit volume of gas or liquid.
Mass spectroscopy: A widely used analytical technique capable of
identifying and quantifying organic materials on the basis of the mass
fragmentation pattern. Most commonly used for organic analysis in
combination with gas chromatography (i.e. GC-MS).
Mass median size: A measurement of particle size for samples of
particulate matter, consisting of that diameter at which the mass of all
larger particles is equal to the mass of all smaller particles.
Meteorology: The science dealing with the atmosphere and weather
conditions.
Micro-climatology: The science that deals with the climate of restricted
areas and investigates their phenomena and causes.
Micro-meteorology: The study of the meteorological characteristics of a
local site that is usually small and often confined to a shallow layer of
air next to the ground.
Mist: Liquid, usually water in the form of particles suspended in the
atmosphere at or near the surface of the earth; small water droplets
floating or falling, approaching the form of rain, and sometimes
distinguished from fog as being more transparent or as having particles
perceptibly moving downward.
Mobile phase: In chromatography, the separation medium which is in
motion.
Month: A base of 30 days to which reported results of outdoor analyses
are calculated.
Neutral compound: A compound which does not ionize in water (e.g. not
acidic or basic).
Nitrogen-phosphorous detector (NPD): A detection device for gas
chromatography which is sensitive and selective for nitrogen- and
phosphorous-containing organic compounds.
Opacity rating: A measurement of the opacity of emissions, defined as the
apparent obscuration of an observer's vision to a degree equal to the
apparent obscuration of smoke of a given rating on the Ringelmann Chart.
Orifice meter: A flowmeter employing as the measure of flow rate the
difference between the pressures measured on the upstream and downstream
sides of the orifice (that is, the pressure differential across the orifice)
in the conveying pipe or duct.
Particle: A small discrete mass of solid or liquid matter.
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Partial* concentrations: Concentration expressed in terms of number of
particles per unit volume of air or other gas. NOTE: On expressing
particle concentration the method of determining the concentration should be
stated.
Particle fall: A measurement of air contamination consisting of the mass
rate at which solid particles deposit from the atmosphere. A term used in
the same sense as the older terms "dust fall" and "soot fall" but without
any amplication as to nature and source of the particles.
Particle sice: An expression for the size of liquid or solid particles
expressed as the average or equivalent diameter.
Particle sice distribution: The relative percentage by weight or number
of each of the different size fractions of particulate matter.
Particulate: Solids or liquids existing in the form of separate
particles.
Phase distribution: The relative amounts of a compound associated with
the particle and gas phases in the atmosphere.
Photochemical reaction: Any chemical reaction initiated as a result of
absorption of light.
Photochemical smog: A type of air pollution resulting from photochemical
reactions.
Photoionication detector (PXD): A detection device for gas chromatography
which detects aromatic, halogenated, and olefinic compounds but is
relatively insensitive to aliphatic compounds. The selectivity can be
adjusted by the choice of lamp energy.
ppb: A unit of measure of the concentration of gases in air expressed as
parts of the gas per billion (10 ) parts of the air-gas mixture, normally
both by volume (ppbv).
ppm: A unit of measure of the concentration of gases in air expressed as
parts of the gas per million parts of the air-gas mixture, normally both by
volume (ppmv).
Precipitation, electrostatic: A process consisting of the separation of
particulate matter from air or other gases under the influence of an
electrostatic field.
Precipitation, meteorological: The deposit on the earth of water from the
atmosphere in the form of hail, mist, rain, sleet, and snow. Deposits of
dew, fog, and frost are excluded.
Precipitation, thermal: A process consisting of the separation of
particulate matter from air and other gases under the influence of a
relatively large temperature gradient extending over a short distance. In
the "Thermal Precipitator" (a sampling instrument), the air or gas is drawn
slowly through a narrow chamber across which extends a heated wire,
particulate matter being deposited upon the adjacent collecting surface.
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Precipitation, ultrasonic: A process consisting of the separation of
particulate matter from air and other gases following agglomeration induced
by an ultrasonic field.
Precipitator, electrostatic: Apparatus employing electrostatic
precipitation for the separation of particles from a gas stream. The
apparatus may be designed either for sampling or for cleaning large volumes
of gas.
Precision: The degree of agreement of repeated measurements of the same
property, expressed in terms of dispersion of test results about the mean
result obtained by repetitive testing of a homogeneous sample under
specified conditions. The precision of a method is expressed quantitatively
as the standard deviation computed from the results of a series of
controlled determinations.
Pressure, gage: The difference between pressure existing within a system
and that of the atmosphere. Zero gage pressure is equal to atmospheric
pressure.
Pressure, static: The pressure of a fluid at rest or in motion, exerted
perpendicularly to the direction of flow.
Pressure, total: The pressure representing the sum of static pressure and
velocity pressure at the point of measurement.
Pressure, velocity: That pressure caused by and related to the velocity
of the flow of fluid; a measure of the kinetic energy of the fluid.
Probe: A tube used for sampling or for measuring pressures at a distance
from the actual collection or measuring apparatus. It is commonly used for
reaching inside stacks and ducts.
Quality assurance: A system of activities designed to provide assurance
that the quality control system is performing adequately.
Quality control: A system of specific efforts designed to test and
control the quality of the data obtained.
Radiosonde: A miniature radio transmitter with instruments that is
carried aloft (as by an unmanned balloon) for broadcasting every few seconds
by means of precise tone signals or other suitable method the humidity,
temperature, pressure, or other parameter.
Resin: A porous polymer adsorbent such as Tenax for collection of gas
phase organic compounds.
Rotometer: A device, based on the principle of Stoke's law, for measuring
rate of fluid flow. It consists of a tapered vertical tube having a
circular cross section and containing a float that is free to move in a
vertical path to a height dependent upon the rate of fluid flow upward
through the tube.
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Sample, cumulative: A sample obtained over a period of time (1) with the
collected atmosphere being retained in a single vessel or (2) with a
separated component accumulating into a single whole. Examples are dust
sampling, in which all the dust separated from the air is accumulated in one
mass of fluid; the absorption of acid gas in an alkaline solution; and
collection of air in a plastic bag or gasometer. Such a sample does not
reflect variations of concentration during the sampling period.
Sample, running: Withdrawal of a portion of the atmosphere over a period
of time along with continuous analysis or with separation of the desired
material continuously and in a "linear" form. Examples are continuous
withdrawal of the atmosphere accompanied by absorption of a component in a
flowing stream of absorbent or by filtration in a moving strip of paper.
Such a sample may be obtained with a considerable concentration of the
contaminant, but it still indicates fluctuations in concentration which
occur during the sampling period.
Sampling: A process consisting of the withdrawal or isolation of a
fractional part of a whole. In air or gas analysis, the separation of a
portion of an ambient atmosphere with or without the simultaneous isolation
of selected components.
Sampling, condensation: A process consisting of the collection of one or
several components of a gaseous mixture by simple cooling of the gas stream
in a device which retains the condensate.
Sampling, continuous: Sampling without interruptions throughout an
operation or for a predetermined time.
Sampling, instantaneous: Obtaining a sample of an atmosphere in a very
short period of time, so that this sampling time is insignificant in
comparison with the duration of the operation or the period being studied.
Sampling, intermittent: Sampling successively for limited periods of time
throughout an operation or for a predetermined period of time. The duration
of sampling periods and of the intervals between are not necessarily regular
and are not specified.
Sampling, source: Withdrawal, with or without simultaneous isolation of
specific components, of a portion of the offgases from a source of
pollutants. Sometimes referred to as stack sampling when withdrawal is from
a chimney, duct, or stack.
Sampling train: The assemblage of equipment necessary to sample
atmospheres.
Scrubber: A type of apparatus used in sampling and in gas cleaning,
whereby the gas is passed through a space containing wetted "packing" or
spray.
Sensor: A device designed to respond to a physical stimulus (as
temperature, illumination, and motion) and to transmit a resulting signal
for interpretation or measurement or for operating a control.
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Series collection: An operation involving the use of two or more
collectors joined in series.
Settling velocity: The terminal rate of fall of a particle through a
fluid, as induced by gravity or other external force; the rate at which
frictional drag balances the accelerating force (or the external force).
Smog: A term derived from the terms "smoke" and "fog", applied to
extensive atmospheric contamination by aerosols, these aerosols arising
partly through natural processes and partly from the activities of human
subjects. Now sometimes used loosely for any contamination of the air.
Smoke: Small gas-borne particles resulting from incomplete combustion,
consisting predominantly of carbon and other combustible material, and
present in sufficient quantity to be observable independently of the
presence of other solids.
Soot: Agglomerations of particles of carbon impregnated with "tar",
formed in the incomplete combustion of carbonaceous material.
Sorbent: A liquid or solid medium in or upon which materials are retained
by absorption or adsorption.
Soxhlet apparatus: An apparatus for use in extracting fatty or other
material with a volatile solvent (as ether, alcohol, or benzene) in which
the solvent is recirculated by evaporation and subsequent condensation.
Specific gravity: The ratio of the density of the substance in question
to the density of a reference substance at specified conditions of
temperature and pressure.
Spectronetry: A method of identification of a compound by identification
of the spectrum produced.
Spectrophotometry; A method for identification of substances and
determination of their concentrations by measuring light transmittance in
different parts of the spectrum.
Standard operating procedure (SOP): A detailed description of the
operation of a sampling or analysis system for a specific .application.
Stationary phase: In chromatography, the separation medium which has held
fixed.
Temperature, absolute: (a) Temperature measured on the thermodynamic
scale, designated as Kelvin (K). (b) Temperature measured from absolute
zero (-273.18*0 or -459.58T). The numerical values are the same for both
the Kelvin scale and the ideal gas scale.
Tenax : A polyphenyloxide polymer prepared as a porous adsorbent for
determination of gas phase organic compounds. The relatively good thermal
stability of Tenax allows recovery of adsorbed organics by thermal
desorption.
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Thermionic detector: See nitrogen-phosphorus detector.
Thin layer chromatography (TLC): A chromatographic technique wherein the
stationary phase is a solid coated in a thin layer on a glass plate and the
mobile phase is a liquid. The technique is commonly used for the
determination of polynuclear aromatic hydrocarbons, using fluorescence
detection.
Validation, data: A systematic effort to review data to identify outliers
or errors and thereby cause deletion or flagging of suspect values to assure
the validity of the data for the user.
Validation, mathod: The process of documenting the performance
characteristics of a method through the analysis of blanks and replicate
samples of known analyte concentration. The analyte concentrations tested
should cover the range likely to be encountered in the actual monitoring
situation.
Vapor: The gaseous phase of matter that normally exists in a liquid or
solid state.
Volume concentration: Concentration expressed in terms of gaseous volume
of substance per unit of air or other gas usually expressed in parts per
million (ppmv) or parts per billion (ppbv).
Year: A period of 12 30-day months, at the end of which results of
analyses of outdoor air are reported.
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APPENDIX D
EQUIPMENT/INSTRUMENT VENDORS
VENDOR
Ace Glass, Inc.
1430 N. West Blvd.
Vineland, NJ 08360
PRODUCT
Sampling Train Glassware
Air Products & Chemicals, Inc.
P.O. Box 538
Allentown, PA 18105
Specialty Gases
Alltech Associates
2051 Waukegan Rd.
Deerfield, IL 60015
Chromatography supplies and
standards
Alnor Instrument Co.
7555 N. Linder Ave.
Skokie, IL 60077
Wind Velocity/Direction
Instrumentation
Alphagaz Specialty Gases
Div. of Liquid Air Corp.
2121 N. California Blvd.
Walnut Creek, CA 94596
Specialty Gases
American Gas & Chemical Co., Ltd.
220 Pegasus Ave.
Northvale, NJ 07647
Specialty Gases
Analabs Div. Foxboro Co.
80 Republic Drive
North Haven, CT 06473
Chromatography supplies and
standards
Analytical Instrument Development,
Rt. 41 and Newark Rd.
Avondale, PA 19311
Inc.
Portable GC System
Andersen Samplers/ Inc.
4215-C Wendell Dr.
Atlanta, GA 30336
Canister Based Sampling System
The Anspec Co., Inc.
P.O. Box 7730
Ann Arbor, MI 48107
Sampling Bags
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VENDOR
Brailsford and Co., Inc,
670 Milton Rd.
Rye, NY 10580
PRODUCT
Air sampling pumps
Brooks Instrument Div.
407 W. Vine Street
Hatfield, PA 19440
Flow measuring and control devices
Bruker Instruments, Inc.
Manning Park
Billerica, MA 01821
Mobile mass Spectrometer System
Calibrated Instruments, Inc.
731 Saw Mill River Rd.
Ardsley, NY 10502
Sampling Bags
California Measurements, Inc.
150 E. Montecito Ave.
Sierra Madre, CA 91024
Particle Sizing Equipment
CEA Instruments, Inc.
16 Chestnut St.
Emerson, NJ 07630
Colorimetric Analyzers
Chemical Data Systems
7000 Limestone Rd.
Oxford, PA 19363
Data Management Systems
Chrompack, Inc.
1130 Rd. 202
Raritan, NJ 08869
GC Packing Material
Chrompack International B.V.
Kuipersweg 6
P.O. Box 8033
Middleburg, The Netherlands 4330EA
GC Packing Material
Climatronics
104 Wilbur PI.
Bohemia, NY 11716
Meteorological Equipment
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VENDOR
Columbia Scientific Industries Corp.
P.O. Box 203190
11950 Jollyville Rd.
Austin, TX 78720
PRODUCT
Thermal Desorption Equipment
Dasibi Environmental
515 W. Colorado St.
Glendale, CA 91204
Gas dilution systems
Dionex Corp.
1228 Titan Way
Sunnyvale, CA 94086
Ion Chromatographs
Dosimeter Corp.
11286 Grooms Rd.
Cincinnati, OH 45242
Passive Monitors
E. I. DuPont de Nemours & Co.,
1007 Market St.
Wilmington, DE 19898
Inc.
Passive Monitors
The Foxboro Company
Foxboro, MA
02035
Infrared Spectrometer
General Metal Works
Div. of Andersen Samplers
145 South Miami Ave.
Village of Cleves, OH 45002
PUF and Hi Vol samplers
Gilian Instrument Corp.
8 Dawes Highway
Wayne, NJ 07470
Sampling pumps
Hewlett-Packard Co.
Mail Stop 2083
3000 Hanover St.
Palo Alto, CA 94304
Analytical Instrumentation
HNU Systems, Inc.
160 Charlemont St.
Newton, MA 02161
GC Systems and Photoionization
Detectors
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VENDOR
The Lee Company
P.O. Box 424
Westbrook, CT 06498
PRODUCT
Teflon solenoid valves and
components
Mace Corporation
2413 Lee Avenue
S. El Monte, CA
Fabricated Teflon components
Matheson Gas Products
30 Seaview Dr.
Secaucus, NJ 07094
Specialty Gases
Micro-Sensor
41762 Christy St.
Freemont, CA 94538
GC Detection Systems
Millipore Corp.
Ashby Rd.
Bedford, MA 01730
Filter Media
Mine Safety Appliances Co,
P.O. Box 426
Pittsburgh, PA 15230
Gas Sampling Tubes
MKS Instruments, Inc.
34 Third Avenue
Burlington, MA 01803
Mass flow controllers
Monitor Labs, Inc.
10180 Scripps Ranch Blvd.
San Diego, CA 92131
Detector Systems
National Draeger, Inc.
P.O. Box 120
101 Technology Dr.
Pittsburgh, PA 15230
Gas Sampling Tubes
Nutech
2806 Cheek Rd.
Durham, NC 27704
Thermal desorbers and cryotrap
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VENDOR
Olympic Products Co.
Div. Cone Mills
4100 Pleasant Garden Rd.
Greensboro, NC 27406
PRODUCT
Polyether foam for PUF sampling
Perkin-Elmer Corp.
761 Main Ave.
Norwalk, CT 06859-0001
Analytical Instrumentation
Perma Pure Products, Inc.
8 Executive Drive
Toms River, NJ 08754
Permeation dryer used with cryotrap
Porter Instrument Co.
P.O. Box 326
Township Line Rd.
Hatfield, PA 19440
Flow measuring devices
Scientific Glass & Instruments, Inc.
P.O. Box 6
Houston, TX 77001
Scientific Glassware
Scientific Instrument Specialists
815 Courtney St.
Moscow, ID 83843
Canister smapling systems
SCIEX
Div. of MDS Health Group, Ltd.
55 Glen Cameron Rd.
Thornhill, Ontario, Canada L3T 1P2
Mobile MS Services
Scott Specialty Gases
6141 Easton Rd.
Plumsteadville, PA 18949
Specialty Gases
Sensidyne, Inc.
12345 Starkey Rd.
Suite E
Largo, FL 33543
Gas Sampling Tubes
Sentex Sensing Technology, Inc.
553 Broad Avenue
Ridgefield, NJ 07657
Gas chromatograph (May be suitable
for ambient sampling with ECD
detector.)
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VENDOR
SKC, Inc.
334 Valley View Rd.
Eighty Four, PA 15330
PRODUCT
Industrial hygiene sampling supplies
Spectrex Corporation
3594 Haven Avenue
Redwood City, CA 94063
Air sampling pumps
Supelco, Inc.
Supelco Park
Bellefonte, PA 16823
Chromotography Supplies
Technical Heaters, Inc.
710 Jessie St.
San Fernando, CA 91340
Heated Sample Lines
Tekmar Co.
P.O. Box 371856
Cincinnati, OH 45222-1856
Thermal Desorption Equipment
Teledyne Hastings-Raydist
P.O. Box 1275
Hampton, VA 23661
Mass flow meters
Thermedics, Inc.
470 Wildwood St.
Woburn, MA 01888-1799
Permeation tubes and diffusion vials
Thermo Environmental Instruments
108 South Street
Hopkinton, MA 01748
Acquired product line of Analytical
Instrument Development, Inc.
Portable GC's and survey type PID' s
TSI, Inc.
500 Cardigan Rd.
P.O. Box 64394
St. Paul, MN 55164
Rc-.i rime Particle Analysis
Equipment
Tylan Corporation
359 Van Ness Way
Torrance, CA 90501
Mass flow controllers
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VENDOR
Valco Instruments Co., Inc.
P.O. Box 55603
Houston, TX 77255
PRODUCT
GC Sampling Valves
Varian Instrument Group
220 Humboldt Ct.
Sunnyvale, CA 94089
GC Systems
Vici Metronics
2991 Corvin Dr.
Santa Clara, CA 95051
Permeation Devices and Dynamic
Calibration Equipment
Weathermeasure Division
Qualimetrics Inc.
P.O. Box 41039
Sacramento, CA 95841
Meteorological Equipment
Wedding & Associates, Inc.
P.O. Box 1756
Fort Collins, CO 80522
High volume PUr samplers, PM-10 etc.
Wheaton Scientific
1000 N. Tenth St.
Millville, NJ 08332
Scientific Glassware
XonTech, Inc.
6862 Hayvenhurst Avenue
Van Nuys, CA 91406
Air sampling equipment for adsorbent
tube sampling
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APPENDIX E
CALIBRATION GAS STANDARDS
Cylinder gas standards of selected hazardous organic compounds at the
ppb level are available through the USEPA for use in auditing the
performance ambient air and stationary source measurement systems.
Calibration standard ranges are 5 ppb and up. Information can be obtained
by contacting:
Robert L. Lampe
USEPA
Environmental Monitoring Systems Laboratory
Quality Assurance Division (MD-77B)
Research Triangle Park, NC 27711
Phone:
Commercial - 919/541-4531
TTS - 629-4531
Group I Compounds
Carbon tetrachloride
Chloroform
Perchloroethylene
Vinyl chloride
Benzene
Group ii Compounds
Trichloroethylene
1,2 - dichloroethane
1,2 - dibromoethane
Acetonitrile
Trichlorofluoromethane (Freon-11)
Dichlorodifluoromethane (Freon-12)
Bromomethane
Methyl ethyl ketone
1,1,1-trichloroethane
Group III Compounds
Vinylidene chloride
1,1,2 trichloro-l,2,2-trifluoro-ethene (Freon-113)
1,2-dichloro-l,1,2,2-tetrafluoroethane (Freon-114)
Acetone
1-4 Dioxane
Toluene
Chlorobenzene
- 122 -
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Group IV Compounds
Acrylonitrile
1,3-Butadiene
Ethylene oxide
Methylene Chloride
Propylene oxide
ortho-xylene
Group V Compounds
Carbon tetrachloride
Chloroform
Perchloroethylene
Vinyl chloride
Benzene
Trichloroethylene
1,2-dichloroethane
1,2-dibromoethane
Methylene chloride
Trichlorofluoromethane (Freon-11)
Bromomethane
Toluene
Chlorobenzene
1,3-Butadiene
ortho-xylene
Ethyl benzene
1,2-dichloropropane
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