United States
Environmental Protection
Agency
Environmental Monitoring and Sup
Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S4-85/056 Dec. 1985
Project Summary
Choosing Cost-Effective QA/QC
Programs for Chemical Analysis
Lloyd P. Provost and Robert S. Elder
The primary objective of the full report
is to provide guidance for choosing
cost-effective quality assurance/qual-
ity control (QA/QC) programsf or chem-
ical laboratories. It describes general
principles of QA/QC, the specific tools
available, and the information needed
to choose appropriate tools for specific
needs. The report does not give detailed
discussions of how to apply each quality
control tool; references are given for
more detailed information.
The major tasks of this project were:
a literature search to identify current
QA/QC practices for inorganic and
organic chemical methods;
an evaluation of ongoing quality as-
surance programs;
development of a model to determine
the type and level of QA/QC effort
required for various uses of particular
analytical methods.
The full report was submitted in fulfill-
ment of Contract Number 68-03-2995,
by Radian Corporation. The research
reported here was conducted under the
sponsorship of the U.S. Environmental
Protection Agency (USEPA).
This Project Summary was developed
by EPA's Environmental Monitoring and
Support Laboratory, Cincinnati, OH, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Background
The Environmental Monitoring and
Support Laboratory, U.S. Environmental
Protection Agency {EPA), Cincinnati of-
fice, has the responsibility for developing
quality control (QC) procedures and lab-
oratory quality assurance (QA) programs
to support ongoing analytical method
development research and monitoring
programs. Radian Corporation was con-
tracted to review current QA/QC pro-
grams* and develop guidelines for
QA/QC practices for the USEPA 600
series methods for chemical analysis of
toxic organic pollutants.
The primary objective of the full report
is to provide guidance for choosing cost-
effective analytical QA/QC programs. To
this end, the full report is organized into
five sections, with two appendices. Ref-
erences are provided throughout the
report for amplification and follow-up by
the reader.
Introduction
This section presents a general over-
view of the report organization. Twelve
general references are provided.
General QA/QC Principles
This section discusses general con-
cepts and approaches found useful by the
quality control profession in over 50 years
of accumulated experience. The princi-
ples described are qualitative, but serve
as guides to quantitative evaluations of
QA/QC programs. They also are helpful
guides in starting quality programs for
new test methods (where information
needed for quantitative decisions may be
lacking) or for choosing minimal programs
for methods whose results are put to
many uses.
*QA = Quality assurance, the system of activities
whose purpose is to provide assurance that
the quality-control job is being done effec-
tively
QC = Qualitycontrol.thesystemof activities whose
purpose is to provide a quality of product or
service that meets the needs of users
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The following concepts are discussed
in this section:
Definition of Quality as FitnessforUse
Total Quality Control
Resource Allocation
Process Control
Measures of Analytical Quality
Simplicity
Seventeen references are provided to
the reader for further studies.
QA/QC Tools
Commonly used QA/QC tools are dis-
cussed in this section in terms of-
Purposes and potential benefits
Information requiredtojudgeeffective-
ness
Qualitative guidance for effective use
Sources of further information
Among the possible reasons for using a
quality control tool are documentation,
appraisal, control or improvement of
quality, and prevention of quality prob-
lems. Some tools serve more than one of
these purposes. The methods available
are not all suitable for every job.
A brief subsection is devoted to each
topic. EPA's QA audit category identifiers
for measured values are given where
appropriate. References are listed at the
end of each subsection for convenience.
The following well-referenced discus-
sion topics are presented in this section:
Blanks (5 references)
Calibration (17 references)
Control Charts (24 references)
Interlaboratory Studies (15 referenc-
es)
Material Controls (6 references)
Method Development (10 references)
Performance and System Audits (5
references)
Reference Materials (7 references)
Replication (11 references)
Sampling Procedures (11 references)
Spike-Recovery Studies (3 references)
Study Planning (5 references)
Surrogate Compounds (2 references)
Validation (5 references)
Measuring QA/QC Cost
Effectiveness
Measures of analytical quality, such as
bias and precision, are useful to the
laboratory for evaluating and maintaining
its performance. However, since factors
in addition to analytical quality often
affect the usefulness of results, more
comprehensive criteria are needed for
measuring end-use effectiveness. The
purpose of this section is to present
methods for evaluating the cost-effective-
ness of particular QA/QC activities.
The statistical tools needed to develop a
quality control program, based upon data
quality objectives (DQO) are presented in
the form of 20 equations, eight charts,
and two useful nomographs. Each topic is
presented with example calculations to
illustrate the solutions to quest ions, such
as:
How many replicate analyses are
needed for a single test to reliably
detect a bias of specified size?
How many replicate analyses are
needed for a single test to reliably
detect a specified bias?
What is the probability of detecting a
serious contamination problem in the
laboratory in a single method blank
analysis?
How many sets of duplicate analyses
are needed in a specified period to
reliably detect a specified increase in
standard deviation?
Choosing Cost-Effective
QA/QC Programs
This section begins with the premise
that in many laboratories an analytical
method may be routinely applied to the
analysis of sample lots with different end-
uses and data quality objectives.
In such a setting, a single QA/QC
program cannot be cost-effective for
every application. One reasonable way to
avoid requiring superfluous efforts is to
establish a two-tier program on the
following basis:
MinimalQC steps needed regardless
of use
AdditionalQC steps tailored to end-
use needs
The cost-effectiveness of QA/QC pro-
grams can be improved further by basing
levels of QC effort in both the minimal and
additional phases on reasonable QC
targets (as discussed in Section 4). The
development of a minimal program is
discussed in the first part of Section 5; the
selection of additional QA/QC procedures
is discussed in the final part of Section 5.
The EPA 600 series methods are used to
illustrate the principles discussed in these
sections
Appendices
The first appendix to the full report
describes the application of skip-lot qual-
ity control procedures. The basic idea of
skip-lot procedures is that the amount of
appraisal effort required in a quality
control program depends on the quality
being produced A process that produces
consistently high quality requires less
monitoring than one that frequently ex-
periences quality problems. Skip-lot pro-
cedures provide objective rules for decid-
ing the frequency of appraisal needed.
The second appendix addresses the
design and analysis of spike-recovery
studies In this appendix, statistical prop-
erties of percent recovery data, when
analytical bias and precision are propor-
tional to sample concentration, are des-
cribed. The impact of the presence of the
analyte of interest in the unspiked sample
(i.e., non-zero background concentration)
is examined and some of the potential
pitfalls in the interpretation of percent
recovery data in method development
and quality control applications are dis-
cussed.
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L. P. Provost andR. S. Elder are with Radian Corporation, Austin, TX 78766.
James E. Longbottom and Stephen Billets are the EPA Project Officers (see
below).
The complete report, entitled "Choosing Cost-Effective QA/QC Programs for
Chemical Analysis," (Order No. PB 85-241 461; Cost: $16.00. subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, V'A 22161
Telephone: 703-487-4650
The EPA Project Officers can be contacted at:
Environmental Monitoring and Support Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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