0 EDA United States ^u1Sm u 0fficeof
Environmental Protection Agency Research and Development
The Arizona Border Study
An Extension of the
Arizona National Human Exposure Assessment Survey (NHEXAS)Study
Sponsored by the Environmental Health Workgroup of the Border XXI Program
Quality Systems and Implementation Plan
for Human Exposure Assessment
The University of Arizona
Tucson, Arizona 85721
Cooperative Agreement CR 824719
Standard Operating Procedure SOP-BCO-L-17.1
Title: Analysis of Volatile Organic Compounds Collected with a Passive
Sampler
Source: The University of Arizona
U.S. Environmental Protection Agency
Office of Research and Development
Human Exposure & Atmospheric Sciences Division
Exposure & Dose Research Branch
Notice: The U.S. Environmental Protection Agency (EPA), through its Office of Research and Development (ORD), partially funded
and collaborated in the research described here. This protocol is part of the Quality Systems Implementation Plan (QSIP)
that was reviewed by the EPA and approved for use in this demonstration/scoping study. Mention of trade names or
commercial products does not constitute endorsement or recommendation by EPA for use.
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Title: Analysis of Volatile Organic Compounds Collected with a Passive Sampler
Document No. BCO-L-17.1
APPROVALS
1 Full SOP 1 Working SOP #pages 24
On Site Principal Investigator:
Issue Date: July 20, 1995
Project QA Director:
Revision No. 0
Independent Reviewer:
Revision No: 1
Revision Date: July 9, 1997
Revision Made: Added VOCs to original list
On Site PI:
Project QA Director:
Independent Reviewer:
Revision No:
Revision Date:
Revision Made:
On Site PI:
Project QA Director:
Independent Reviewer:
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Analysis of Volatile Organic Compounds Collected with a Passive Sampler
1.0 Purpose and Applicability
This standard operating procedure (SOP) describes methodology used for the analysis of
the 3M OVM 3500 Organic Vapor Monitors for volatile organic compounds (VOCs),
using solvent extraction and standard gas chromatograph/mass spectrometer (GC/MS)
analysis procedures.
2.0 Definitions
2.1 Diffusional (passive) sampler: collects contaminant based on the principle of
diffusion; no pump is used to collect the sample.
2.2 Sampling (uptake) rate: the mass of a diffusing chemical divided by the product
of its concentration and the sampling period (in units of volume per unit time).
3.0 References
3.1 3M Organic Vapor Monitors #3500/3510 Instructions for Use, Occupational
Health and Safety Products Division/3M, 1993.
3.2 3M Organic Vapor Monitor Sampling and Analysis Guide for Organic Vapor
Monitors 3500/3510 and Organic Vapor Monitors 3520/3530, 1993.
3.3 H.C. Shields and C.J. Weschler, "Analysis of Ambient Concentrations of Organic
Vapors with a Passive Sampler," JAPCA, 37, 1039-1045 (1987).
3.4 R. Otson, P. Fellin, and S.E. Barnett, "Field Testing of a Passive Monitor for
Airborne VOCs," paper 92-80.07, 85th A&WMA Annual Meeting, June 1992.
3.5 R. Otson, P. Fellin, and Q. Tran, "VOCs in Representative Canadian
Residences," Atmos. Environ. 28, 3563-3569 (1994).
3.6 P. Fellin and R. Otson, "Assessment of the Influence of Climatic Factors on
Concentration Levels of Volatile Organic Compounds (VOCs) in Canadian
Homes," Atmos. Environ. 28, 3581-3586 (1994).
3.7
"Standard Practice for Analysis of Organic Compound Vapors Collected by the
Activated Charcoal Tube Adsorption Method," Standard D 3687, American
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Society for Testing and Materials, Philadelphia, Annual Book of ASTM
Standards, 1989.
3.8 "Sampling Workplace Atmospheres to Collect Organic Gases or Vapors with
Activated Charcoal Diffusional Samplers," Standard D 4597, American Society
for Testing and Materials, Philadelphia, Annual Book of ASTM Standards, 1992.
3.9 Hewlett-Packard 5890 GC Operator's Manual, June 1993.
3.10 Hewlett-Packard 7673A Automatic Sampler Operating and Service Manual, 1995.
3.11 Finnigan MAT Ion Trap Mass Spectrometer System ITMS™ Operator's Guide, P/N
94099-97002, Rev. A, January 1989.
3.12 Finnigan MAT Ion Trap Detector™ Operation Manual, P/N 94011-98025, Rev. G,
January 1989.
Discussion
4.1 The OVM 3500 Organic Vapor Monitor badges used to sample the target VOCs
(according to the procedure described in SOP UA-F-12.1) are extracted with
carbon disulfide. Organic compounds present in the extract are separated and
identified using standard gas chromatography/mass spectrometry (GC/MS)
analysis procedures. Specifically, a small aliquot of the extract (~1 p.L) is injected
into the hot injector of the GC. Analytes and solvent vapors are swept onto the
GC column by the helium carrier gas. The GC column temperature is then
increased uniformly (temperature programmed) and the components eluting from
the column are identified and quantified by MS in the full scan mode. Component
identification is normally accomplished on the basis of the GC retention time and
mass spectral fragmentation pattern. The method is not suitable for the VOC 1,3-
butadiene. The collection efficiency of the low boiling 1,3-butadiene by the OVM
3500 badge is generally poor, and instead, this compound is sampled and
analyzed using actively-pumped carbon-based multisorbent tubes, as described in
SOPs UA-F-11.1 and BCO-L-22.1.
4.2 Interferences resulting from the analytes having similar retention times during GC
analysis are resolved by MS selection. Both the range and limit of detection
depend strongly on the properties of the individual compounds of interest.
According to Otson et al. (Refs. 3.5 and 3.6), the OVM 3500 badges provide
reliable measurements of selected airborne VOCs at concentrations ranging from
about 2 to 6,000 |J.g/m3 for a 24-h to 7 day sampling period. For the compounds
of interest, detection limits are in the range 1.6-5.9 ng/m3 based upon GC/MS/
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SIM analysis and extraction recoveries are: 95.0% for benzene, 97.6% for
toluene, and 96.4% for trichloroethene.
Responsibilities
5.1 Fixed-location sampling of indoor and outdoor air for the target VOCs will be
conducted by University of Arizona (UA) personnel as described in SOP
UA-F-12.1.
5.2 The Sample Custodian at Battelle will be responsible for receiving the samples
from UA and shall sign and date all forms accompanying the samples at the time
of sample receipt. The Sample Custodian shall also be responsible for
transferring custody of the samples to the appropriate Laboratory Analyst for
analysis and shall archive the remaining samples on completion of the laboratory
work.
5.3 Extraction, analysis, and calculations for the samples, as defined in this work
instruction, will be performed by the Laboratory Analyst in the Atmospheric
Sciences and Applied Technology Department at Battelle, under the direction of
the Laboratory Director or his designee.
5.4 The Data Coordinator will be responsible for checking that the Laboratory
Analyst has completed the Sample Laboratory Data Sheet and for preparing Data
Packages for shipment to UA.
5.5 The Laboratory Director at Battelle will be responsible for ensuring completion of
the analyses in accordance with the work instruction and quality control
requirements. He will also be responsible for approving the original and
revisions to the method.
5.6 Any person who amends or alters this procedure is responsible for ensuring that
the changes have been properly documented, the SOP changed, reviewed, and
reissued.
Materials and Reagents
6.1 Materials
6.1.1 OVM 3500 Organic Vapor Monitors (Occupational Health and Safety
Products Division, 3M).
6.1.2 2 mL conical vials (cone begins at 0.5 mL, 48 mm from base of cone to lip
of vial, 8 mm ID).
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6.1.3 1 (J.L, 10 fiL Hamilton syringes; gas-tight microsyringes (10-2,500 ^L)
6.1.4 Class A volumetric flasks, 10 mL.
6.1.5 Capillary pipettes, 50 (iL.
6.1.6 Pasteur pipettes.
6.1.7 Combined Hewlett-Packard 5890 gas chromatograph/Finnigan MAT Ion
Trap Mass Spectrometer (GC/ITMS or GC/MS). The GC is equipped
with a split/splitless injector and a Hewlett-Packard 7673A autosampler.
The GC oven contains a 60 m x 0.32 mm id. DB-5 poly(diphenyl/dimethyl
siloxane) fused silica capillary column. Optimum analytical results are
achieved by temperature programming the GC oven from -50 °C to 200 °C
at 8 7min. The MS is operated in the full-scan mode. In this mode, the
ITMS scans all masses repeatedly during the GC run between a lower and
an upper mass limit. This mode thus provides a complete mass spectrum
for each GC peak. The mass spectrum may then be used to identify the
compound using a computer-based compilation of standard spectra along
with a suitable library search algorithm. For quantitation purposes, a
characteristic ion mass is selected for each target compound and the peak
area of the selected ion is used to determine the amount of material present
in thje sample extract.
6.1.8 Helium carrier gas (purity >99.995%).
6.1.9 Low velocity laboratory fume hood.
6.1.10 Refrigerator.
6.1.11 Nafion PermaPure tube (25 cm x 0.4 cm ID).
6.1.12 Liquid microliter syringes, 10 (J.L, Hamilton (or equivalent), for injection
of standards and sample extracts into GC/MS system.
Reagents
6.2.1 Carbon disulfide, 99.9+% ("benzene-free"), HPLC or Gold Label grade
(Aldrich Chemical Co.), as specified in Ref. 3.3.
6.2.2 Benzene, A.R.G. (Aldrich Chemical Co.)
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6.2.3 Toluene, A.R.G. (Aldrich Chemical Co.)
6.2.4 Trichloroethene, A.R.G. (Aldrich Chemical Co.)
6.2.5 m-Dichlorobenzene, A.R.G. (Aldrich Chemical Co.)
6.2.6 Styrene, A.R.G. (Aldrich Chemical Co.)
6.2.7 Tetrachloroethene, A.R.G. (Aldrich Chemical Co.)
6.2.8 1,1,2-Trichloroethane, A.R.G. (Aldrich Chemical Co.)
6.2.9 p-Xylene, A.R.G. (Aldrich Chemical Co.)
6.2.10 1,1,1-Trichloroethane, A.R.G. (Aldrich Chemical Co.)
6.2.11 Distilled water
6.2.12 Perfluorotributyl amine (FC-43) for MS mass-scale standardization.
7.0 Procedure
All relevant information relating to the analysis of samples, such as lot numbers,
manufacturers of reagents and gases, etc., must be recorded contemporaneously on the
"Sample Laboratory Data Sheet - Badge/VOCs" (Figure 1) and compared against any
control parameters. Any deviations noted require that the analysis be discontinued or
justified via the analysts' best judgement.
7.1 Initial Preparations
7.1.1 Preparation of Primary Standard Solution
7.1.1.1 Prepare a stock solution at an equivalent air concentration of -20
ppbv for each of the nine analytes listed below.
7.1.1.2 Using a 10 |iL Hamilton syringe, add 2.50 \iL of each compound
to 50 mL carbon disulfide solvent in a 100 mL volumetric flask.
Shake gently to mix and make up to mark with CS2.
7.1.1.3
Stopper the 100-mL volumetric flask. Label with the laboratory
notebook number, analytes and concentrations, solvent used,
preparer's initials, and date.
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7.1.1.4 Place flask in refrigerator.
7.1.1.5 The primary standard solution remains fresh for up to 6 months.
7.1.1.6 The actual equivalent concentrations of the analytes are
summarized in the table:
Compound
jiL Added
per 100 mL
Density
(g/mL)
Amount
(mg)
in 100 mL
Equivalent
Concn
(ng/fiL)
Assumed
Amount (fig)
on Badge
Equiv
Concn
(ppbv)*
Benzene
2.50
0.874
2.185
21.85
32.78
30.2
Toluene
2.50
0.867
2.168
21.68
32.51
27.3
Trichloroethene
2.50
1.464
3.660
36.60
54.90
32.9
m-Dichlorobenzene
2.50
1.288
3.220
32.20
48.30
33.0
Styrene
2.50
.909
2.273
22.73
34.09
36.1
T etrachloroethene
2.50
1.623
4.058
40.58
60.86
30.1
1,1,2-Trichloro-
ethane
2.50
1.435
3.588
35.88
53.81
34.7
p-Xylene
2.50
0.866
2.165
21.65
32.48
28.0
1,1,1-Trichloro-
ethane
2.50
1.338
3.345
33.45
50.18
28.7
* Calculated from equation in Section 7.6.4.
7.1.2 Preparation of Calibration Standards
7.1.2.1 Prepare five solutions to be used for the GC calibration curve in
five 10-mL volumetric flasks, according to the following matrix.
Compound
Primary Standard (mL)
10
5
2.5
1.25
0.5
Calibration Concentration (ng/|u.L)
Benzene
21.9
10.9
5.46
2.73
1.09
Toluene
21.7
10.8
5.42
2.71
1.08
Trichloroethene
36.6
18.3
9.15
4.58
1.83
m-Dichlorobenzene
32.2
16.1
8.05
4.03
1.61
Styrene
22.7
11.4
5.68
2.84
1.14
T etrachloroethene
40.6
20.3
10.1
5.07
2.03
1,1,2-Trichloroethane
35.9
17.9
8.97
4.48
1.79
p-Xylene
21.7
10.8
5.41
2.71
1.08
1,1,1 -T richloroethane
33.5
16.7
8.36
4.18
1.67
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7.1.2.2 Using gloves and a fume hood, add ~1 mL of carbon disulfide to
four of the five volumetric flasks. (The fifth flask is not diluted).
7.1.2.3 Transfer aliquots of each of the primary standard volumes into
their respective volumetric flasks using volumetric pipettes.
7.1.2.4 Stopper the flasks and invert several times to mix thoroughly.
Dilute to volume with carbon disulfide.
7.1.2.5 Label the flasks as Instrument Calibration Standards with the
corresponding concentration level. Include the date of
preparation, preparer's initials, and the page of the notebook
where all the information was recorded.
7.1.2.6 Transfer aliquots from each of the volumetric flasks to individual
2-mL screw-cap vials with silicone septa. Label the vials as per
Section 7.1.2.5.
7.1.2.7 Store all standard solutions in a refrigerator at 4 °C.
7.1.2.8 Switch to new vials of the calibration solution every six weeks
and discard the previous solutions.
7.1.2.9 Use the concentrated stock solution to prepare fresh solutions or
other dilutions for up to six months.
7.1.3 Preparation of Spiked Laboratory and Field Controls
7.1.3.1 Spiked controls are used to verify recoveries of the target
compounds, since techniques and the presence of multiple
contaminants can affect recovery efficiencies.
7.1.3.2 To prepare a spiked control, remove a monitor from its
aluminum container.
7.1.3.3 Remove the white film and plastic ring from the monitor.
7.1.3.4 Place a 2.5 cm diameter filter paper on the spacer plate.
7.1.3.5
Snap the closure cap on the monitor.
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7.1.3.6 The spiking standard is prepared as follows:
7.1.3.6.1 Using a volumetric pipette, add 30 (iL each of benzene
and toluene and 20 |iL of trichloroethene to 25 mL
carbon disulfide solvent in a 50 mL volumetric flask.
Shake gently to mix and make up to mark with CS2.
7.1.3.6.2 Stopper the 50-mL volumetric flask. Label as
"Spiking Standard" and include the laboratory note-
book number, analytes and concentrations, solvent
used, preparer's initials, and date. The spiking
standard solution remains fresh for up to 6 months.
Store flask in refrigerator.
7.1.3.6.3 Assuming a 10-nL aliquot ofthe spiking standard is
injected onto the badge, the actual equivalent concen-
trations of the analytes are:
m
Ko
t
c *
C *
^a
Compound
(ng)
(cmVmin)
DE
(min)
(P-g/m3)
(ppbv)
Benzene
5.24
35.5
0.95
10,080
15.41
4.83
Toluene
5.20
31.4
1.00
10,080
16.44
4.37
Trichloroethene
5.86
31.1
0.99
10,080
18.87
3.55
Calculated from equation in Section 7.6.4.2: Ca — m / (Ko.DE.t).
7.1.3.7 Using a Hamilton syringe, withdraw a suitable volume of liquid
from the volumetric flask (e.g., 5 - 20 \iL) and inject the solution
onto the filter paper through the center port.
7.1.3.8 Allow the monitor to sit for 16-24 hours to allow total transfer of
the compounds from the filter paper to the sorbent.
7.1.3.9 Remove the filter paper from the monitor.
7.2.1 GC/MS Instrument Set-Up
7.2.1.1. The helium sweep flow (across the GC injector septum) and
carrier gas flow are set at approximately 3-5 mL/min and 1-2
mL/min, respectively.
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7.2.1.2 Once the column and other system components are assembled
and the various flows established, the column temperature is
initially increased to about 250 °C for at least 4 hours to
condition the column.
7.2.1.3 The MS and data system are set according to the manufacturer's
instructions. Electron ionization (70 eV) and an electron
multiplier gain of about 105 should be used. Once the entire
GC/MS system has been set up, the system is calibrated as
described in Section 7.2.3. (Steps taken to validate the operation
of the data system are described in the Appendix).
7.2.1.4 The injector module of the HP 7673A autosampler is positioned
onto the injection port of the GC. It houses the syringe holder
and a "turret"-type sample tray with space for 5 vials (one to
three samples, one wash and one waste bottle), and associated
electronics to perform the injection sequence. A tray module,
which can position any one of 100 vials (sample extracts) into
the injector, is located adjacent to the injector module. The turret
tray rotates the 5 vials into position directly below the syringe.
Settings for the sample volume (1-5 jiL), number of injections
per sample (1 - 4), number of sample pre-washes (0 - 10), and
number of solvent post-washes (0 - 10) are selected through the
front panel of the controller unit. Samples are loaded into the
tray module in the order in which they are to be analyzed.
7.2.2 Daily GC/MS Tuning and Standardization
7.2.2.1 Once daily, the GC/MS system must be tuned according to
manufacturer's instructions, to verify that acceptable
performance criteria are achieved.
7.2.2.2 To tune the GC/MS, FC-43 is introduced directly into the ion
trap via the molecular leak and the automatic calibration
procedure is used to calibrate the ITMS, using seven peaks of the
calibration compound: m/z 69, 131, 219, 264, 414, 502, and 614.
If any of the calibration peaks are not found, especially at the
higher masses, a slope value is calculated between the closest
two peaks that are found. If necessary, instrumental parameters
are adjusted to give documented, standard relative abundances as
well as acceptable resolution and peak shape (see Section 7.7). If
the instrument fails to tune under auto-tune conditions, the
instrument must be retuned. If the criteria cannot be met, even
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after retiming the mass spectrometer, the ion trap may require
cleaning as per the manufacturer's instructions. The performance
criteria must be achieved before any blanks, standards, or
samples are analyzed.
7.2.2.3 After tuning is complete, output one spectrum of FC-43 from the
calibration analyses and store this spectrum in the instrument
calibration file folder in the MS laboratory.
7.2.3 Initial Calibration of the GC/MS System
7.2.3.1 Before analyzing a sample set on a new column, or after the
instrument has been vented for cleaning or maintenance,
calibration runs are performed with the Calibration Standards,
under the same conditions used to analyze the field samples.
7.2.3.2 Calibration standards encompass four levels, plus a zero level,
that bracket the expected concentration range of interest.
7.2.3.3 For the present purposes, a linear response corresponds to a
correlation coefficient >0.98 for a linear least squares fit of the
concentration versus relative response (peak area of the target ion
of the analyte divided by the peak area of the target ion of the IS;
AS/AIS) data.
7.2.3.4 Once response linearity has been demonstrated, an intermediate
concentration standard near the expected levels for the
components of interest is used for daily calibration purposes.
7.2.3.5 Responses of the target compounds should not vary by more than
10% from day-to-day. If greater variability is observed, more
frequent calibration may be required to ensure the reliability of
the measurements.
7.2.3.6 For each analyte, the average retention time is established
manually from the individual retention times generated in the
calibration runs. A calibration response factor is determined for
the analyte by the computer.
7.2.3.7 Generate the calibration curve, as described in Section 7.6.1.
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7.2.3.8 Once the initial calibration curve has been established, the
GC/MS system is checked on a daily basis with a one-point
calibration.
7.2.3.9 After the single-point calibration, the analytical system is
challenged with neat carbon disulfide to ensure the cleanliness of
the system (i.e., levels of target VOCs must be <0.2 ppbv).
Preparation of Field Samplers and Blanks for Analysis
Set up a new manila folder labeled with the date of analysis and place all
relevant information (written correspondence, identification of samples and
associated computer data files, GC-MS plots, etc.) in the folder. This file will
ultimately contain all information relating to the analysis and reports of the
samples analyzed in the laboratory this day.
7.3.1 Preparation of OVM 3500 Organic Vapor Monitor Samplers
7.3.1.1 Arrange the OVM 3500 samplers in sets of 5 in the order that the
samplers are recorded in the Sample Custodian's sample
logbook.
7.3.1.2 Inspect each sampler. Check, especially, that:
(a) The closure cap is firmly snapped to the monitor body
(b) The closure cap plugs are firmly seated in the cap ports.
7.3.1.3 If any defects are observed, note them in the "Comments"
column of the Sample Laboratory Data Sheet (Figure 1).
7.3.1.4 If the sampler or seal is broken so that air may have entered the
sampler, the sample is voided and marked "NOT ANALYZED"
in the Sample Laboratory Data Sheet.
7.3.2 Extraction of OVM 3500 Badges
7.3.2.1 Open the center port of the badge and inject 1.5 mL of carbon
disulfide. The rim port can be open to allow venting.
7.3.2.2 Reseal both ports.
7.3.2.3 Let badge stand with the charcoal pad of the badge in contact
with the solvent for at least 45 minutes, with occasional mild
agitation by hand.
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7.3.2.4 Open both ports. Carefully transfer the solvent through the rim
port to a 2-mL conical sampler vial.
7.3.2.5 Label, seal, and store the vial in the freezer until ready for
GC/MS analysis.
7.4 Preparation of Samples for Analysis
7.4.1 Arrange the sample vials in sets of 20 samples with five standards (one
standard vial from each concentration level) in the following order:
standard, 8 samples, standard, 8 samples, etc, until all are used.
7.4.2 Inspect each vial. If any defects, such as low volume with respect to the
marked volume line are observed, note them in the "Comments column
of the Data Sheet.
7.5 Analysis of OVM 3500 Sampler Extracts
7.5.1 Separate and quantify the target compounds present in the extract using
standard GC/MS full-scan mode procedures.
7.5.2 Sample analysis is accomplished using a 60 m x 0.32 mm id DB-5 fused
silica capillary column. Optimum analytical results are achieved with this
column by temperature programming the GC oven from -50 °C to 200 °C at
8°/min. The injection port is held at 240 °C.
7.5.3 Helium carrier gas flow through the column ranges from 3 to 5 cm3/min.
7.5.4 Cool the GC oven to its set point.
7.5.5 Using a clean microliter syringe, withdraw a 1 or 2 aliquot of the sample
extract from the vial and inject it into the GC.
7.5.6 Start the GC oven control program and the ITMS data acquisition ('ACQ )
program.
7.5.7 After the final target compound elutes from the column, terminate the
acquisition.
7.5.8 Once a stable baseline has been achieved, the system may be readied for the
next analysis.
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7.5.9 For sample extracts where target compound levels exceed the calibration
range of standards, prepare dilutions with CS2 at 1:10 and 1:100 for
reanalysis.
7.5.10 Initial data processing generally involves (1) qualitatively determining the
presence or absence of each target compound on the basis of a set of
characteristic ions and retention times, and (2) quantification of each
identified component by integrating the intensity of a selected
characteristic ion and comparing the value to that of the calibration
standard.
7.5.11. The characteristic ions selected post-acquisition from the full-scan run for
each analyte include the "target ion", which is used for quantification, and
the "qualifier ion", which is used to verify detection on the basis of correct
intensity relative to the target ion intensity. These diagnostic ions are
listed below with their respective relative intensities.
Compound
Target Ion
Qualifier Ion
Benzene
78
79
Toluene
91
92
Trichloroethene
130
95
m-Dichlorobenzene
146
148
p-Dichlorobenzene
146
148
o-Dichlorobenzene
146
148
Ethylbenzene
91
106
Styrene
104
103
T etrachloroethane
166
164
1,1,2-Trichloroethane
97
99
m+p-Xylene
91
106
o-Xylene
91
106
1,1,1 -T richloroethane
97
99
7.5.12 Place all laboratory-related worksheets in the current analysis folder in
preparation for report generation.
Calculations
7.6.1 Calibration Curve
7.6.1.1 Using the calibration standards data (from Section 7.2.3),
perform a least-squares linear regression analysis, using a
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standard personal computer program and an equation of the form
A = a + bC, where
A = MS peak area (in area units, AU)
C = level of the target compound standard (j_ig)
a = intercept, and
b = slope (AU/|j.g).
7.6.1.2 The correlation coefficient R2 must be greater than 0.98. If this
requirement is not met, re-evaluate the analysis and, if necessary,
run another calibration curve.
7.6.2 Calculation of Target Compound Content of Blank Samplers
7.6.2.1 The target compound content of unexposed (blank) samplers or
control samples mbl must be calculated using the calibration
coefficients from Section 7.6.1.1 and the measured peak areas of
the sample Abl for each compound of interest:
mbl = — (ng)
7.6.2.2 Calculate the average amount for the unexposed samplers from
the same batch.
7.6.3 Calculation of Target Compound Content of Exposed Samplers
7.6.3.1 Use the calibration coefficients from Section 7.6.1.1 and the
measured peak areas of the exposed sampler Aap, for each
compound of interest and correct for the content of unexposed
samplers:
UxP-«)
™exp = L
-mbl (lag)
where m is the target compound content of the exposed
sampler.
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7.6.4 Calculation of Passive Sampler Target Compound Concentration
7.6.4.1 The behavior of the OVM 3500 sampler can be described by
Fick's first law of diffusion (see Ref. 3.6), in terms of which the
flux is proportional to the concentration gradient, i.e.,
where m = mass of compound adsorbed by the sampler (|ig);
t = sampling interval (s); A = cross-sectional area through which
diffusion occurs (7.07 cm2 for the OVM 3500 sampler);
D = diffusion coefficient (cm2/s); Ca = gas-phase concentration
of compound (ng/cm3); Cf= concentration of compound just
above sorbent pad (=0); and / = path over which diffusion
occurs (1.0 cm for the OVM 3500 sampler).
7.6.4.2 The quantity m/tCa in Equation (7-1) defines the sampling
(uptake) rate for diffusive samplers, which is a constant provided
the amount of material collected is much less than the capacity of
the sorbent material used in the device. If the sampling rate for a
compound is known, it can be used to calculate the concentration
Ca of that compound from the equation:
where K0 = uptake rate, as defined in Equation (7-1); and
DE = recovery (desorption) coefficient, a factor used to adjust for
incomplete extraction of a substance from the OVM 3500
sorbent pad.
(7-1)
7.6.4.3
The sampling rates, recovery efficiencies, and capacity limits for
the target compounds are as follows(see Ref. 3.2):
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Compound
Sampling Rate
(cm3/min)
Recovery
Coefficient
Capacity
(mg)
Benzene
35.5±0.6
0.95
22
Toluene
31.4±0.6
1.00
>25
Trichloroethylene
31.1±0.2
0.99
>25
m-Dichlorobenzene
27.8±0.6
0.87
>25
p-D ichlorobenzene
27.8±0.6
0.87
>25
o-D ichlor obenzene
27.8±0.6
0.87
>25
Ethylbenzene
27.3
0.96
24
Styrene
26.8±0.8
0.82
>25
T etrachloroethy lene
31.1±0.2
0.95
>25
1,1,2-T richloroethane
29.7±0.6
0.95
>25
m+p-Xylene
27.3±0.5
0.97
>25
o-Xylene
27.3±0.5
0.97
>25
1,1,1-Trichloroethane
30.9±0.3
1.03
22
7.6.4.4 To calculate the concentration in parts per million (ppm) at 25 °C
and 760 mm Hg, use the value in mg/m3 determined in Step
7.6.4.2 in the following equation:
24 45
C (ppmv) = C(mg / m3) x
where MW = molecular weight of target compound (in g/mole).
7.6.4.5 If the sampling temperature is significantly different from 25 °C,
then the temperature-corrected concentration C0 is obtained from:
t j298°K
C0 = C(mg / m ) x
V s
or
x / 298° AT
C0 = C(ppmv) x ~
where Ts - temperature recorded at the sample site (in °K). This
correction eliminates an error of about 1% for every 10°F (5.6
°C) increment above or below 77°F (25°C) (see Ref. 3.2).
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Quality Control
7.7.1 Solvent Purity, Spiked Controls, Blanks, and Duplicates
7.7.1.1 Each lot of HPLC or Gold Label Grade carbon disulfide must be
analyzed before use to ensure that it contains no more than trace
levels of benzene (see Ref. 3.3).
7.7.1.2 The overall performance of the monitoring method is evaluated
using spiked controls, blanks, and duplicates.
7.7.1.3 Given the small amounts of material that are collected with the
OVM 3500 badges, it is important that samplers used as spikes,
blanks, duplicates, and field samplers come from the same lot
number, since the background compounds present on unexposed
samplers may vary significantly from lot to lot
7.7.1.4 At least one sampler should be prepared for analysis as a field
spike, one sampler each presented for analysis as a field blank
and an unexposed blank, and one field duplicate sampler taken
with every 20 field samples.
7.7.1.5 Method Accuracy: Prior to conducting a study with OVM 3500
badges, blank badges are spiked with the compounds of interest and
analyzed to determine the level of recovery of each compound.
Percent relative accuracy is given by:
7
% Bias = —100
JC
where X = expected level of target compound; and Y= measured
level of target compound recovered in analysis.
7.7.1.6 Rlank Radges: Blank badges are analyzed to determine inadvertent
contamination. Of the analytes of interest in this SOP, benzene is one
of the principal compounds detected in OVM 3500 blanks, and occurs
typically at -0.3 |agftadge. Most other VOCs should be present at
<0.02 |ig/badge.
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7.7.2 Precision, Bias, and Detection Limit
7.7.2.1 Precision and bias are largely dependent upon the precision and
bias of the analytical procedure for each target compound, and
the precision and bias of the sampling process.
7.7.2.2 When the errors involving determination of desorption
efficiency, sampling, and analysis are combined, a relative
precision of ±15% is indicated.
7.7.2.3 Recovery efficiencies for the target compounds are between 95
and 100%.
7.7.2.4 The method detection limit MDL for a target compound is
obtained from the above data. It is defined as:
MDL = A + 3.3a
where A = intercept (coefficient) from the least squares fit to the
calibration curve; and s = standard deviation of the lowest
concentration measurements. The method detection limit for the
3M OVM 3500 passive monitor is about 2 jag/m3, with a practical
quantitation limit of about 8 |ig/m3. Field tests have also shown
that these monitors provide reliable measurements of selected
airborne VOCs at concentrations ranging from about 2 to 6,000
M-g/m3.
7.7.3 Instrument Tuning and Standardization
7.7.3.1 Refer to Section 7.2.2. These procedures provide a means of
monitoring MS performance characteristics over time, and
permanent records of the information are kept in the laboratory.
7.7.4 Calibration for Quantitative Analysis
7.7.4.1 Refer to the quantitative analysis calibration procedures. If
quantitative responses (in area counts) of the lowest level
standard mixture fall below the detection limits, the instrument
and/or GC column and injector must be checked for
performance degradation. The injector and/or ion trap should be
cleaned or the first 0.5 m of the column should be removed.
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7.7.4.2 Those samples which were analyzed during the period when low
level standards were not detected will be reanalyzed.
7.7.5 Storage Stability
7.7.5.1 The shelf life of the OVM 3500 monitor prior to exposure is 18
months when stored in cool, dry conditions which do not exceed
90 °F for extended periods of time.
7.7.5.2 The shelf life of the OVM 3500 monitor after exposure is 1
month when stored in a refrigerator at 4 °C.
7.7.6 Corrective Actions
7.7.6.1 Before beginning any analytical sequence, insert a fresh septum
into the injection port of the GC. Replace the septum daily or
when necessary. Septum failure is probably the most frequent
cause of inconsistent detector response for a given standard or
sample.
7.7.6.2 Changes in the retention times of the target compounds may
indicate a leak in the GC system or deterioration of the GC
column. If this is accompanied by loss of column resolution, the
column should be replaced.
Records
8.1 All operations, maintenance and performance calibration data are stored in each
instrument log book.
8.2 List each sample analyzed on the GC/MS in the instrument log book, including
the date of data acquisition, project number, instrument conditions, file name,
and floppy disk identification.
8.3 All analytical results are logged in specific project books and entered on the
OVM 3500 Sampler Analysis Data Sheet (Figure 2). Directions for filling out
the Analysis Data Sheet are as follows:
8.3.1 Obtain a separate Analysis Data Sheet for each sample.
8.3.2 In the spaces provided, enter the sample code, the analysis date, the
analyst's name, the exposure time (in minutes), and the dilution factor
(default is 1).
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8.3.3 Enter the amounts obtained (in jag) for the field sample and the blank.
8.4 All data files are stored on floppy disks for permanent record.
8.5 Hardcopy output of chromatograms and data reports are produced by the data
system after each run.
8.6 Hard copies of the data will be stored in the analytical laboratory with the
laboratory notebook.
8.7 Analysis results will be sent to UA after one-over-one review of the data.
8.8 All forms and logbooks shall also include the technician's signature, date, time of
analysis, and method number.
8.9 All completed data forms and results will be submitted to the Laboratory Director
where they will be checked and stored in a designated area.
8.10 All forms will be filled out in black ink. Any deletions or corrections shall be
made by drawing a line through the error and shall be initialed by the technician
making the correction.
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Figure 1: "Sample Laboratory Data Sheet - Badge/VOCs"
ITEM: PARAMETER:
Date
Analyst
Standard Curve Number
Primary Std.: Benzene Lot No.
Date Approved
Primary Std.: Toluene Lot No.
Date Approved
Primary Std.: Trichloroethene Lot No.
Date Approved
Primary Std.: m-Dichlorobenzene Lot No.
Date Approved
Primary Std.: Styrene Lot No.
Date Approved
Primary Std.: Tetrachloroethene Lot No.
Date Approved
Primary Std.: 1,1,2-Trichloroethane Lot No
Date Approved
Primary Std.: p-Xylene Lot No
Date Approved
Primary Std.: 1,1,1-Trichloroethane Lot No
Date Approved
Solvent: Carbon Disulfide Lot No.
Date Approved
Carbon Disulfide Blank Check Benzene at trace level
Helium Gas Cylinder ID No.
Date Approved
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ITEM
GC Column ID No.
Date Installed
GC Carrier Gas Flow Rate
GC Temperature Program
Autosampler Settings
MS (SIM): Filament Currrent
EM Voltage
Standard Curve
No. of Badges Analyzed
No. of Badges Recorded
COMMENTS:
Figure 1: Continued
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PARAMETER
Data attached
DB-5, 60 m x 0.32 mm
1.0 - 1.2 cnvVmin
-50 °C - 200 °C at 8 °/min
# of injections/sample;
injection volume (fiL); # of
syringe pre-rinses; # of
syringe post-rinses
80 (J.A
1.8-2.0 kV
SAME AS ANALYZED
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Figure 2: OVM 3500 Sampler Analysis Data Sheet
VOCs in Air
Sample ID: Analysis Date:
HHID: Analyst:
Exposure Time, t = min Dilution Factor:
Compound
Ko
(cm3/min)
DE
mbr
(ng)
#*
(^g)
Benzene
35.5
0.95
Toluene
31.4
1.00
Trichloroethene
31.1
0.99
m-Dichlorobenzene
27.8
0.87
p-Dichlorobenzene
27.8
0.87
o-Dichlorobenzene
27.8
0.87
Ethylbenzene
27.3
0.96
Styrene
26.8
0.82
T etrachloroethene
31.1
0.95
1,1,2-T richloroethane
29.7
0.95
m+p-Xylene
27.3
0.97
o-Xylene
27.3
0.97
1,1,1 -T richloroethane
30.9
1.03
Calculated from equation in Sections 7.6.2.
Calculated from equation in Sections 7.6.3.
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Appendix
Data System Validation
We have adopted a "holistic" approach to validate the computer system used in
this SOP, based on the procedure described by Furman et al. (W.R. Furman, T.P.
Layloff, and R.E, Tetzlaff, "Validation of Computerized Liquid Chromatographic
Systems," J. AOAC Intl., 77, 1314-1318, 1994). This consists of tests to measure
and evaluate the performance of the entire computerized GC/MS system under the
conditions of its intended use, namely, the analysis of extracts of VOCs.
The approach involves an initial characterization and calibration, and a running
calibration. The initial characterization consists of generating 70-eV mass spectra
for each of the target compounds and comparing the spectra with the corres-
ponding standards in a computer-based spectral library (Wiley Registry of Mass
Spectral Data, 5th Edition, containing 140,000 reference spectra and structures for
over 118,000 compounds). The initial calibration is designed to evaluate system
linearity and precision. Linearity is determined by using at least 4 standard
solutions to generate the response curve over the range of interest, as specified in
the SOP. Precision is determined initially by making replicate injections (> 5) of
a single standard solution and calculating the standard deviation of the area
responses.
After satisfactory linearity and precision data are obtained, a standard solution is
run at regular intervals so as to document that the system is not drifting or has
undergone an unexpected change.
All data generated in evaluating the characterization of spectra and calibration of
the system are maintained in a documentation file that is kept with the instrument.
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