5838
Method 524. Measurement of Purgeable Organic
Compounds In Drinking Water
by Gas Chromatography/Mass Spectrometry
February 1983
Ann Alford-Stevens
Games W» Eichelberger
William L. Budde
Physical and Chemical Methods Branch
Environmental Monitoring and Support Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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OATE
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
FEB 2 2 1983
SUBJECT Nationwide Approval of Alternate Test Procedure
01 Trihalomethanes
FROM vrctor Ox Kimm, Director
Office of Drinking Water (WH-550)
T0'Regional Administrators
Listed below is an alternate test procedure for determining
trihalomethanes by a gas chromatography-mass spectrcrr.etry
(GC-MS) method which I have approved for nationwide use for
"National Interim Primary Drinking Water Regulation" (NIPDWR)
compliance monitoring.
This method was developed by the Environmental Monitoring and
Support Laboratory (EMSL) in Cincinnati for the measurement
of purgeable organic compounds in drinking water. Unlike the
previously approved Method 501.3 which involves selected-ion
monitoring with a mass spectrometer, this method permits the
acquisition of complete mass spectra. In addition, this
method can be used for the measurement of many other volatile
organic compounds along with the trihalomethanes. EMSL's
data show that the precision and accuracy of this method is
comparable to that of EPA's approved methods. (Previously
approved methods for trihalomethanes are 501.1, 501.2 and
501.3.) Although detection limits for trihalomethanes are
not as low as those obtained with other approved methodology,
they are entirely adequate for the current maximum contaminant
level.
Measurement
Total Trihalomethanes
Method
^Method 524 - "Measurement of
Purgeable Organic Compounds
in urinking water by Gas
Chromatography/Mass
Spectrometry".
j-V --TT-- r - - -- - _
z/-.ddi uionul information on this method is available from the
Envi .vor.rnontal Monitoring and Support Laboratory, 26 West St
£ti;eot, Cincinnati, Ohio 45268.
cc: Robo.'.-t L. Booth, Acting Director, EMSL
Ann Alford-SLevonn, Chomist, EMSL
Roqi OD.J 1 Writf?r Supply Representatives
H'.'fji onn 1 Quality AG.'jur.irice Officers
Clair
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INDEX
Section
Number Subject
1 Scope and Application
2 Summary of Method
3 Definitions
4 Interferences
5 Safety
6 Apparatus and Equipment
7 Reagents and Consumable Materials
8 Sample Collection, Preservation and Handling
9 Calibration
10 Quality Control
11 Procedure
12 Calculations
13 Precision and Accuracy
References
TABLES
1. Ion Abundance Criteria for p-Bromofluorobenzene.
2. Single Laboratory Method Efficiency Data for Purgeable Organic Compounds
Measured with GC/MS.
3. Acceptable Storage Times for River and Drinking Water Samples Containing
Halogenated Aliphatic Analytes.
4. Storage Time Data for River and Drinking Water Samples Containing
Aromatic Analytes.
5. Single Laboratory Accuracy and Precision Data for Purgeable Organic
Compounds Measured with GC/MS.
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Method 524. Measurement of Purgeable Organic Compounds
in Drinking Water By Gas Chromatography/Mass Spectrometry
1. SCOPE AND APPLICATION
1.1 This is a general purpose method that provides procedures for
identification and measurement of purgeable organic compounds in
finished drinking water, raw source water, or drinking water in any
treatment stage. The method is applicable to a wide range of
organic compounds that have sufficiently high volatility and low
water solubility to be removed from water samples with purge and
trap procedures. Single-laboratory method efficiency, accuracy and
precision data have been determined for the following compounds:
Chemical Abstracts Service^
Analyte
benzene
bis(2-chloroisopropyl) ether
bromoch1orometh ane
bromodichloromethane
4-bromof1uoroben zene
bromoform
carbon tetrachloride
chlorobenzene
chlorod ibromomethane
chloroform
chloromethane
1,2-dibromo-3-chloropropane
1,2-dichlorobenzene
1,3-dichlorobenzene
1,2-dichloroethane
1,1-dichloroethene
trans-1,2-dichloroethene
cis-1,3-dichloropropene
methylene chloride
styrene (ethenylbenzene)
1,1,2,2-tetrachloroethane
tetrachloroethene
toluene
1,1,1-trichloroethane
1,1,2-tr1chloroethane
trichloroethene
vinyl chloride
p-xylene
Registry Number (CASRN)
71-43-2
39638-32-9
74-97-5
75-27-4
460-00-4
75-25-2
56-23-5
108-90-7
124-48-1
67-66-3
74-87-3
96-12-8
95-50-1
541-73-1
107-06-2
75-35-4
156-60-5
10061-01-5
75-09-2
TOO-42-5
79-34-5
127-18-4
108-88-3
71-55-6
79-00-5
79-01-6
75-01-4
106-42-3
STORET
Number
34030
34283
77297
32101
32104
32102
34301
32105
32106
34418
34536
34566
34531
34501
34546
34699
34423
77128
34516
34475
34010
34506
34511
39180
30175
A laboratory may use this method to detect and measure additional
analytes after the laboratory obtains acceptable (defined in
Section 10) accuracy and precision data for each added analyte.
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1.2 Detection Limits (MDLs) (1) are compound dependent, varying with
purging efficiency and concentration, where MDL is defined as the
statistically calculated minimum amount that can be measured with
99% confidence that the reported value is greater than zero. For
the listed analytes in reagent water, MDLs vary from 0.07 to 11.2
ug/L. The applicable concentration range of this method is
compound and instrument dependent but is approximately 0.2 ug to
200 ug of analyte per liter of undiluted sample. Analytes that are
inefficiently purged from water will not be detected when present
at low concentrations, but they can be measured with acceptable
accuracy and precision when present in sufficient amounts.
1.3 Determination of some individual components of complex mixtures may
be hampered by insufficient chromatographic resolution and/or by
large differences in concentrations of individual components.
2. SUMMARY OF METHOD
Highly volatile organic compounds with low water solubility are removed
(purged} from the sample matrix by bubbling helium through a 25-mL
aqueous sample. Purged sample components are trapped in a stainless
steel tube containing suitable sorbent materials. When purging is
complete, the sorbent tube is heated and backflushed with helium to
desorb purged sample components into a gas chromatograph (GC) interfaced
to a mass spectrometer (MS). Compounds eluting from the GC column are
tentatively identified by comparing their mass spectra to reference
spectra in a data base. Tentative identifications are confirmed by
analyzing standards under the same conditions used for samples and
comparing resultant mass spectra and GC retention times. Each identi-
fied component is measured by relating the MS response for an appro-
priate selected ion produced by that compound to the MS response for the
same ion from that same compound in an external standard or for another
ion produced by a compound that is used as an internal standard.
3. DEFINITIONS
External standard a known amount of a pure compound that is analyzed
with the same procedures and conditions that are used to analyze samples
containing that compound. From measured detector responses to known
amounts of the external standard, a concentration of that same compound
can be calculated from measured detector response to that compound in a
sample analyzed with the same procedures.
Internal standard a pure compound added to a sample in known amounts
and used to calibrate concentration measurements of other compounds that
are sample components. The internal standard must be a compound that is
not a sample component.
Field duplicates two samples taken at the same time and place under
identical circumstances and treated exactly the same throughout field
and laboratory procedures. Analysis of field duplicates indicates the
precision associated with sample collection, preservation and storage,
as well as with laboratory procedures.
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Field reagent blank reagent water placed in a sample container in the
laboratory and treated as a sample in all respects, including exposure
to sampling, site conditions, storage, preservation and all analytical
procedures.
Laboratory control standard a solution of analytes prepared in the
laboratory by dissolving known amounts of pure compounds in a known
amount of reagent water. In this method, the laboratory control
standard is prepared by adding appropriate volumes of the secondary
dilution standard solution and the internal standard/surrogate compound
spiking solution to reagent water.
Laboratory duplicates two aliquots of the same sample that are
treated exactly the same throughout laboratory analytical procedures.
Analysis of laboratory duplicates indicates precision associated with
laboratory procedures but not with sample collection, preservation or
storage procedures.
Laboratory reagent blank a 25-mL portion of reagent water placed in
the purging apparatus and analyzed as if it were a sample.
Performance evaluation sample a methanol solution of method analytes
distributed by the Quality Assurance Branch (QA8), Environmental
Monitoring and Support Laboratory, USEPA, Cincinnati, Ohio, to multiple
laboratories for analysis. A small volume of the methanol solution is
added to a known volume of reagent water and analyzed with procedures
used for samples. Results of analyses are used by the QAB to determine
statistically the accuracy and precision that can be expected when a
method is performed by competent analysts. Analyte true values are
unknown to the analyst.
Quality control check sample a methanol solution containing known
concentrations of analytes prepared by a laboratory other than the
laboratory performing the analysis. The analyzing laboratory uses this
solution to demonstrate that it can obtain acceptable identifications
and measurements with a method. A small volume of the methanol solution
is added to a known volume of reagent water and analyzed with procedures
used for samples. True values of analytes are known by the analyst.
Secondary dilution standard a methanol solution of analytes prepared
in the laboratory from stock standard solutions and diluted as needed to
prepare aqueous calibration solutions and laboratory control standards.
Stock standard solution a concentrated solution containing a
certified standard that is a method analyte, or a concentrated methanol
solution of an analyte prepared in the laboratory with an assayed
reference compound. Stock standard solutions are used to prepare
secondary standard solutions.
Surrogate compound ~ a compound that is not expected to be found in the
sample, is added to the original environmental sample to monitor perform-
ance, and is measured with the same procedures used to measure sample
components.
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4. INTERFERENCES
4.1 Samples may be contaminated during shipment or storage by diffusion
of volatile organics through the sample bottle septum seal. Field
reagent blanks must be analyzed to determine when sampling and
storage procedures have not prevented contamination.
4.2 During analysis, major contaminant sources are volatile materials
in the laboratory and impurities in the inert purging gas and in
the sorbent trap. Analyses of field reagent blanks and laboratory
reagent blanks provide information about the presence of contami-
nants.
4.3 Interfering contamination may occur when a sample containing low
concentrations of volatile organic compounds is analyzed
immediately after a sample containing relatively high concentra-
tions of volatile organic compounds. A preventive technique is
between-sample rinsing of the purging apparatus and sample syringes
with two portions of reagent water. After analysis of a sample
containing high concentrations of volatile organic compounds, the
system should be baked for 10 min by passing helium through the
sample purging chamber into the heated (180°) sorbent trap. One
or more laboratory reagent blanks should be analyzed to ensure that
accurate values are obtained for the next sample.
5. SAFETY
5.1 The toxicity or carcinogenicity of chemicals used in this method
has not been precisely defined; each chemical should be treated as
a potential health hazard, arid exposure to these chemicals should
be minimized. Each laboratory is responsible for maintaining
awareness of OSHA regulations regarding safe handling of chemicals
used in this method. Additional references to laboratory safety
are cited (2-4).
5.2 The following method analytes have been tentatively classified as
known or suspected human or mammalian carcinogens: benzene* carbon
tetrachloride, chloroform, and vinyl chloride. Pure standard
materials and stock standard solutions of these compounds should be
handled in a hood.
6. APPARATUS AND EQUIPMENT
6.1 Sample containers 120-mL or larger glass bottles each equipped
with a screw cap and a polytetrafluoroethylene-faced silicone
septum.
6.2 ftjrge and trap device consisting of sample purging chamber, sorbent
trap and desorber. (Acceptable devices are commercially available.)
6.2.1 The all glass sample purging chamber holds 25-mL samples
with < 15 ml of gaseous headspace between the water column
and the trap. The helium purge gas passes through the water
column as finely divided bubbles (optimum diameter of <3 mm
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at the origin). The purge gas must be introduced at a
point <5 mm from the base of the water column.
6.2.2 The stainless steel sorbent trap is 25 cm long by 2.5 mm ID
and is packed with 8 cm of Tenax-GCR, 8 cm of silica gel,
and 8 cm of charcoal, in that order with respect to the
inlet end of the trap. The charcoal is not necessary for
listed analytes but is necessary if fluorine-substituted
methanes and ethanes (fluorocarbons) are among additional
analytes. When analytes do not include fluorocarbons, the
charcoal may be eliminated, and the amount of Tenax-GCR
may be increased. A trap with different dimensions can be
used if it has been evaluated and found to perform satisfac-
torily (i.e., provides method efficiencies equal to or
better than those in Table 2). Before initial use, the trap
should be conditioned overnight at 18QOC by backflushing
with helium flow of at least 20 mL/min. Each day the trap
should be conditioned for 10 min at 180°C with back-
flushing.
6.2.3 The desorber should be capable of rapidly heating the trap
to 180°C. The trap section containing Tenax-6CR should
not be heated to higher than 180°C, and the temperature of
the other sections should not exceed 200°C.
6.3 SYRINGES AND SYRINGE VALVES
6.3.1 Two 25-mL glass hypodermic syringes with Luer-LokR tip (if
applicable to the purging device being used).
6.3.2 One 5-mL gas-tight syringe with shutoff valve.
6.3.3 Two two-way syringe valves with Luer ends (if applicable to
the purging device being used).
6.3.4 Micro syringes, various sizes.
6.4 MISCELLANEOUS
6.4.1 Standard solution storage containers 10-mL bottles with
polytetrafluoroethylene-lined screw caps.
6.4.2 Analytical balance capable of weighing 0.0001 g accurately.
6.4.3 Helium purge gas, as contaminant free as possible.
6.5 GAS CHROMATOGRAPH/MASS SPECTROMETER/DATA SYSTEM (GC/MS/DS)
6.5.1 The 6C must be capable of temperature programming. Any
column (either packed or capillary) that provides data with
adequate accuracy and precision (Sect. 10) can be used. If
a packed column is used, the GC usually is interfaced to the
MS with an all-glass enrichment device and an all-glass
-------
transfer line, but any enrichment device or transfer line
can be used if performance specifications described in this
method can be demonstrated with it. If a capillary column
is used, an enrichment device is not needed. A recommended
packed GC column for the listed analytes is 1.8 m long by 2
mm ID glass packed with 1% SP-1000 on 60/80 mesh Carbopack
B. Recommended operating parameters for that column are:
helium carrier gas flow rate of 30 mL/min and temperature of
45°C for 4 min, increased to 230°C at a rate of
8°C/min, and isothermal at 230°C for at least 25 min or
until all expected analytes elute. An alternative recom-
mended packed column is 1.8 m long by 2 mm ID glass or
stainless steel packed with 0.2% Carbowax 1500 on 80/100
mesh Carbopack C.
6.5.2 Mass spectral data are obtained with electron-impact
ionization at a nominal electron energy of 70 eV. The mass
spectrometer must be capable of scanning from 35 to 450 amu
every 7 s or less and must produce a mass spectrum that
meets all criteria in Table 1 when 50 ng or less of
£-bromofluorobenzene (BFB) is introduced into the GC. To
ensure sufficient precision of mass spectral data, the
desirable MS scan rate allows acquisition of at least five
spectra while a sample component elutes from the GC. With
capillary columns which produce narrower peaks than packed
columns that criterion may not be feasible and adequate
precision with fewer spectra per GC peak must be
demonstrated (Sect. 10).
6.5.3 An interfaced data system (DS) is required to acquire,
store, reduce and output mass spectral data. The computer
software must allow searching any GC/MS data file for ions
of a specific mass and plotting ion abundances versus time
or scan number. This type of plot is defined as an
extracted ion current profile (EICP). Software must also
allow integrating the abundance in any EICP between speci-
fied time or scan number limits.
7. REAGENTS AND CONSUMABLE MATERIALS
7.1 SORBENT TRAP PACKING MATERIALS
7.1.1 Polymer based on 2,6-diphenyl-£-phenylene oxide 60/80
mesh Tenax-6CR, chromatographic grade, or equivalent.
7.1.2 Coconut charcoal 26 mesh.
7.1.3 Silica gel 35/60 mesh, Davison Chemical grade 15, or
equivalent.
7.2 REAGENTS
7.2.1 Methanol pesticide quality or equivalent.
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7.2.2 Reagent water water in which an interferent is not
observed at the method detection limit of the compound of
interest. Prepare reagent water by. passing tap water through
a filter bed containing about 0.5 kg of activated carbon, by
using a water purification system, or by boiling distilled
water for 15 min followed by a 1 h purge with inert gas
while the water temperature is held at 90°C. Store in
clean, narrow-mouth bottles with polytetrafluoroethylene-
lined septa and screw caps.
7.2.3 Sodium thiosulfate or sodium sulfite granular, ACS
reagent grade.
7.3 STOCK STANDARD SOLUTIONS These solutions may be purchased as
certified solutions or prepared from pure standard materials using
the following procedures:
7.3.1 Place about 9.8 ml of methanol in a 10-ml ground-glass
stoppered volumetric flask. Allow the flask to stand
unstoppered for about 10 min or until all alcohol-wetted
surfaces have dried. Weigh the flask to the nearest 0.1
mg.
7.3.2 If the analyte is a liquid at room temperature, with a
100-uL syringe immediately add two or more drops of assayed
reference compound to the flask. (The liquid must fall
directly into the alcohol without contacting the flask). If
the analyte 1s a gas at room temperature, fill a 5-mL valved
gas-tight syringe with the standard to the 5.0-mL mark,
. lower the needle to 5 mm above the methanol meniscus, and
slowly inject the standard into the neck of the flask. (The
gas will rapidly dissolve in the methanol.)
7.3.3 Reweigh the flask, dilute to volume, stopper, and mix by
inverting several times.
7.3.4 From the net weight gain, calculate the concentration in
micrograms per micro liter. When assayed compound purity is
>9656, the unconnected weight may be used to calculate
concentration.
7.3.5 Store stock standard solutions with minimal headspace in
polytetraf1uoroethylene-1ined screw-capped bottles.
Methanol solutions of listed liquid analytes are stable for
at least four weeks when stored at 4°C. Methanol
solutions prepared from listed gaseous analytes are not
stable for more than one week when stored at <0°C; at room
temperature, they must be discarded after one day.
7.4 SECONDARY DILUTION STANDARD Use stock standard solutions to
prepare a secondary dilution standard solution that contains the
analytes in methanol. The secondary, dilution standard should be
prepared at a concentration that can be easily diluted to prepare
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aqueous calibration solutions (Section 9.2.1.2) at concentrations
that will bracket the working concentration range. Store the
secondary dilution standard solution with minimal headspace and
check frequently for signs of deterioration or evaporation,
especially just before preparing calibration solutions from it.
7.5 INTERNAL STANDARD SPIKING SOLUTION AND SURROGATE COMPOUND SPIKING
SOLUTION Prepare a solution of fluorobenzene in methanol at a
concentration that allows use of 2 to 10 uL to add an appropriate
amount of fluorobenzene to each sample; this amount should be
approximately the same as the amount of the analyte to be measured.
If the internal standard technique is used, fluorobenzene serves as
the internal standard. If the external standard technique is used,
fluorobenzene is a surrogate compound added to each sample to
monitor method performance. Fluorobenzene was selected because it
is stable in aqueous solutions, is. efficiently purged, does not
occur naturally, and is not commercially produced in bulk
quantities but is available as a laboratory reagent chemical.
8. SAMPLE COLLECTION. PRESERVATION AND HANDLING
8.1 Collect all samples in duplicate. Fill sample bottles to over-
flowing. No air bubbles should pass through the sample as the
bottle is filled, or be trapped in the sample when the bottle is
sealed. Keep samples sealed from collection time until analysis.
Maximum storage times vary with analytes of concern. Recent
studies (5-6) provided data indicating appropriate storage times
for samples (river and drinking water) containing compounds that
are potential method analytes (Tables 3 and 4).
8.1.1 When sampling from a water tap, open the tap and allow the
system to flush until the water temperature has stabilized
(usually about 10 min). Adjust the flow to about 500 mL/min
and collect duplicate samples from the flowing stream.
8.1.2 When sampling from an open body of water, fill a 1-qt
wide-mouth bottle with sample from a representative area,
and carefully fill duplicate sample bottles from the 1-qt
bottle.
8.2 SAMPLE PRESERVATION
8.2.1 If styrene (which reacts with chlorine) and/or trihalo-
methanes are to be measured in a sample expected to contain
residual chlorine, add a reducing agent, sodium thiosulfate
or sodium sulfite (30 mg per 120-mL sample for up to 5 ppm
chlorine) to the empty sample bottle before it is shipped to
the sampling site.
NOTE: Some possible analytes may be unstable in the
presence of reducing agent. Data (5) indicate that sodium
sulfite should not be used if analytes include
chloromethane, 1,1-dichloroethene, 1,1-dichloropropene,
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2-chloroethyl ethyl ether, or 1,1,2,2-tetrachloroethane;
sodium thiosulfate is not recommended if analytes include
chloromethane or 1,2-dibromoethane.
8.2.2 Much remains to be learned about biological degradation of
aromatic hydrocarbon analytes. Currently, two preservation
techniques are recommended but both have negative aspects.
8.2.2.1 Hydrochloric acid may be used at the sampling site
to adjust the sample pH to < 2; the major disadvan-
tages of this procedure are that shipping acid is
restricted by federal regulations and that effects
of low pH on other analytes (such as organohalides)
are largely unknown.
8.2.2.2 Mercuric chloride may be added to the sample bottle
in amounts to produce a concentration of 10 mg/L.
This may be added to the sample at the sampling site
or to the sample bottle in the laboratory before
shipping to the sampling site. A major disadvantage
of mercuric chloride is that it is a highly toxic
chemical; it must be handled with caution, and
samples containing it must be disposed with appro-
priate procedures.
8.2.2.3 If analytes include both aromatic hydrocarbons and
styrene or trihalomethanes, current recommendations
are either to add both preservative types (reducing
agent along with acid or mercuric chloride) or to
collect two samples with the appropriate preserva-
tive type in each.
8.2.3 After addition of preservative(s), seal the sample bottle
and shake vigorously for 1 min.
8.3 FIELD BLANKS
8.3.1 Duplicate field reagent blanks must be handled along with
each sample set, which is composed of the samples collected
from the same general sample site at approximately the same
time. At the laboratory, fill field blank sample bottles
with reagent water, seal, and ship to the sampling site
along with empty sample bottles and back to the laboratory
with filled sample bottles. Wherever a set of samples is
shipped and stored, it is accompanied by appropriate blanks.
8.3.2 When reducing agent or preservative(s) is added to samples,
use the same procedures used for samples to add the same
amount to blanks. The reducing agent can be added in the
laboratory.
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9. CALIBRATION
9.1 INITIAL CALIBRATION
9.1.1 CALIBRATION SOLUTIONS
9.1.1.1 At least three calibration solutions, each contain-
ing a standard of each analyte, are needed. (More
than three calibration solutions may be required if
analytes are numerous.) One calibration solution
should contain each analyte at a concentration
approaching but greater than the method detection
limit (Table 5) for that compound; the other two
solutions should contain analytes at concentrations
that bracket the range expected in samples. For
example, if the detection limit for a particular
analyte is 0.2 ug/L, and a 25-mL sample expected to
contain approximately 5 ug/L is analyzed, aqueous
solutions of standards should be prepared at
concentrations of 0.3 yg/L, 5 ug/L, and 10 yg/L.
9.1.1.2 To prepare calibration solutions, add appropriate
volumes (uL) of the secondary dilution standard
solution to aliquots of reagent water. Remove the
plunger from a 25-mL syringe and attach a closed
syringe valve. Fill the syringe with reagent water,
replace the plunger, and compress the water. Open
the syringe valve and vent air. Adjust the reagent
water volume to 25 mL and add a carefully measured
aliquot of 2.0 to 18.0 uL of the secondary dilution
standard through the valve bore. Add the appro-
priate amount (> 2.0 uL) of the internal standard
surrogate spiking solution through the valve bore,
but do not add more than 20 yL total volume of
methanol solution.
NOTE: If appropriate concentrations cannot be
prepared without adding more than 20 yL of the
secondary dilution standard to 25 mL of reagent
water, prepare a new secondary dilution standard.
If less than 2.0 yL must be added to obtain appro-
priate concentrations, prepare a larger volume of
the calibration solution in a volumetric flask. Mix
by inverting the flask several times, and transfer a
25-mL portion into the sample syringe. The remain-
ing solution may be stored in screwcap vials with no
headspace. If aromatic compounds are among calibra-
tion solution components, do not store for more than
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1 h. Other aqueous solutions can be stored for up
to 24 h.
9.1.2 Analyze .triplicate aliquots of each calibration solution
with the procedures to be used to analyze samples.
9.1.2.1 If the external standard technique is being used,
prepare a concentration calibration curve for each
analyte by plotting integrated abundances of the ion
characteristic of that compound as a function of the
concentration. If the ratio of ion abundance to
amount of analyte is constant (< 10% relative
standard deviation) throughout the concentration
range, the average ratio may be used instead of a
calibration curve.
9.1.2.2 If the internal standard technique is being used,
calculate the mass spectrometer response to each
compound relative to fluorobenzene, the internal
standard. Calculate the response factor (RF) with
the equation,
RF
-
where Ax * integrated abundance of the selected ion for
the analyte standard;
As * integrated abundance of the selected ion for
the internal standard;
Qs quantity of internal standard; and
Qx * quantity of analyte standard.
RF is a unitless number; units used to express quantities of
analyte and internal standard must be equivalent. Ideally,
the response factor for each analyte should be independent
of analyte quantity for the working range of the
calibration, but required linearity will vary with required
accuracy of analyte concentration measurements. Generally,
acceptable variations of mean RF values are ± 15% over a
concentration range of two orders of magnitude and ± 10% RSD
of values obtained from analyses of triplicate aliquots of
each concentration calibration solution. For an analyte
with non-linear RF, a calibration curve of Areax/Areas
plotted versus Qx way be used to determine an analyte
concentration.
9.2 DAILY CALIBRATION Check calibration data each day by measurement
of one or more laboratory control standards or calibration solu-
tions. If the expected ion abundance was observed (Sect. 10.5) for
50 ng of the MS performance standard but the absolute ion abundance
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measured for any analyte varies from expected abundance by more
than 15%, prepare and analyze a fresh calibration solution to
determine if the problem is being caused by deterioration of the
calibration solution or by a malfunction in the purge and trap
apparatus. When the internal standard technique is being used,
verify each day that response factors have not changed. When
changes occur (> 10% relative standard deviation), prepare and
analyze new standard solutions to determine new response factors.
NOTE: Some analysts have observed marked deterioration of MS
response after the initial purge and trap analysis each day; if
this phenomenon is observed, perform one purge/desorb cycle before
checking MS performance and calibration data.
10. QUALITY CONTROL
10.1 Minimum quality control requirements consist of:
10.1.1 initial demonstration of laboratory analytical capability
(efficiency, accuracy and precision procedures, Sect. 10),
10.1.2 analysis of an MS performance standard and a laboratory
control standard near the beginning of each 8-h work period,
10.1.3 analysis of a field reagent blank along with each sample set,
10.1.4 analysis of a laboratory reagent blank when the field
reagent blank contains analytes at concentrations above the
method detection limits,
10.1.5 quarterly analysis of a quality control check sample, (if
available for analytes of concern), and
10.1.6 continued maintenance of performance records to define the
quality of generated data.
10.2 METHOD EFFICIENCY For each analyte, calculate method efficiency
by comparing the detector response when the compound is introduced
by syringe injection with the detector response when the same
amount is introduced by purging, trapping, and desorption. Because
of the calibration technique used in this method, high efficiency
is not required for acceptable precision and accuracy, but low
method efficiency may cause unacceptably high detection limits.
Measure method efficiency for each analyte whenever the analytical
system undergoes major modification, such as replacement of trap
packing.
10.2.1 Analyze at least five laboratory control standards with the
purge, trap, desorption and 6C/MS detection procedures.
Interspersed among these five or more analyses, inject two
or more aliquots of the secondary dilution standard solution
-------
(Section 7.4) directly into the GC to introduce each analyte
in an amount equal to that introduced by purge and trap
procedures. Use the same MS data acquisition parameters for
injected analytes as those used for purge and trap proce-
dures.
10.2.2 Calculate the method efficiency (E) for each analyte in each
aliquot of the laboratory control standard with the equation:
E . A- 100 ,
Ai
where Ap = ion abundance of compound introduced with purge
and trap techniques, and
A.J * ion abundance produced by an equal amount of
the same compound when injected.
For this calculation, use data obtained from an injection
either closely preceding or following the purge and trap
analysis from which data are used.
10.2.3 Calculate the mean method efficiency for each analyte.
Acceptable detection limits usually can be achieved even if
the mean method efficiency is only 20 to 30%.
10.3 ACCURACY To determine accuracy, analyze duplicate aliquots of a
quality control (QC) check sample containing known amounts of
analytes of concern. QC check samples for some, but not all listed
analytes, currently are available from the U.S. Environmental
Protection Agency, Environmental Monitoring and Support Laboratory,
Quality Assurance Branch, Cincinnati, Ohio 45268; alternatively
certified standard solutions may be purchased from commercial
vendors.
10.3.1 When using the external standard procedure, calculate
accuracy as the ion abundance found in the QC sample
solution expressed as a percentage (P) of the ion abundance
found in the external standard solution:
Ax
P = -T£ . 100 ,
where Ax - abundance of ion used to measure an analyte in
an aliquot of the QC check sample, and
As = abundance of ion used to measure an equal
amount of the same analyte treated as an
external standard.
10.3.2 When using the internal standard procedure, fluorobenzene in
the solution of analyte standards is the internal standard.
-------
Calculate response factors (Sect. 9.3.4) for each analyte
relative to fluorobenzene. With these response factors,
calculate accuracy with data acquired for the QC check
sample:
P = Ax . 100
A DP
e> l»r
where Ax » abundance of ion used to measure an analyte in
an aliquot of the QC check sample,
As - abundance of ion used to measure
fluorobenzene in the same aliquot, and
RF « response factor of the particular
analyte relative to fluorobenzene.
NOTE: The internal standard concentration is constant in
calibration solutions and all samples for which the
calibration solutions are used (Section 9.3).
10.3.3 For each analyte, the mean accuracy should be in the range
of 85 to 115X. For some listed analytes, this may not be
feasible for low concentration measurements.
10.4 PRECISION
10.4.1 For each analyte, calculate method precision as the standard
deviation (s, in yg/L) of the replicate measured values
obtained in the accuracy calculations:
n n
9 /%
. _ n j . X^ - 4_iX-i £
n (n-1)
where n = number of measurements for each analyte, and
X = individual measured value.
10.4.2 For the set of measured values for each analyte, calculate
the dispersion as the percent relative standard deviation
(RSO):
RSD = s . 100
C
where s « standard deviation, and
C s mean observed concentration.
10.4.3 Adequate precision is obtained when the relative standard
deviation is £20%. For some listed analytes, this may not
be feasible foir low concentration measurements.
-------
10.5 MS PERFORMANCE STANDARD
10.5.1 Near the beginning of each 8-h work period in which analytes
are to be measured, measure the mass spectrum produced by 50
ng of p_-bromofluorobenzene (BFB) to ensure that it meets
performance criteria (Table 1). BFB may be introduced into
the MS either by syringe injection or through the purge and
trap system. It may be a component of the laboratory
control standard analyzed daily to check calibration (Sect.
7). Measure the entire mass spectrum at an MS scan rate
that produces at least five spectra for the BFB GC peak but
does not exceed 7 s per spectrum. Although acquisition of
five spectra per BFB GC peak may not be feasible when capil-
lary columns are.used, BFB performance criteria still must
be met. If the BFB spectrum is unacceptable, adjust GC/MS
operating parameters until an acceptable spectrum is pro-
duced before samples are analyzed.
10.5.2 Record the absolute ion abundance detected for 50 ng of
BFB. If ion abundance varies more than ± 10% from the
expected number, check the GC/MS system to locate and
correct the problem. Preparation of a new calibration curve
may be necessary if the system is operating acceptably but
with decreased sensitivity.
10.6 LABORATORY CONTROL STANDARD To demonstrate that the calibration
curve is still valid, analyze a laboratory control standard at the
beginning of each 8-h work period.
10.6.1 For each analyte to be measured, select a concentration
representative of its occurrence in drinking water samples.
10.6.2 Prepare the laboratory control standard with either of the
following procedures:
10.6.2.1 From stock standard solutions, prepare a
laboratory control standard concentrate in
methanol. This solution should contain analytes
at concentrations 2500 times those selected as
representative concentrations. Add 10 yL of the
laboratory control standard concentrate to a 25-mL
aliquot of reagent water.
10.6.2.2 Add 2 to 18 uL of the secondary dilution standard
to 25 mL of reagent water contained in the sample
syringe.
10.6.3 Add an appropriate volume of the internal standard/surrogate
spiking solution and analyze with the same procedures (Sect.
11) to be used for samples.
-------
10.6.4 Determine calibration acceptability and appropriate remedial
actions, if needed. (For the external standard technique,
see Sect. .9.1.2.1; for the internal standard technique, see
Sect. 9.1.2.2.)
10.7 MONITORING THE SURROGATE COMPOUND/INTERNAL STANDARD - Because all
samples and laboratory control standards contain equal amounts of
the internal standard/surrogate compound, use the absolute ion
abundance for the characteristic ion of that compound, fluoro--
benzene, to monitor system performance. If for any sample, the
absolute ion abundance varies more than 15% from that observed in
the previous sample or laboratory control standard, do not report
analyte values obtained for that sample, and take remedial actions
to solve the system performance problem.
10.8 FIELD REAGENT BLANKS ~ Analyze a field reagent blank along with
each sample set. If a field reagent blank contains analytes at
concentrations above the method detection limits, analyze a
laboratory reagent blank. If one or more analytes that are not
detected at concentrations above method detection limits in the
laboratory reagent blank are detected in significant amounts in the
field blank, sampling or storage procedures have not prevented
sample contamination, and the appropriate analyte measurement(s)
must be discarded.
10.9 At least quarterly, analyze a quality control check sample obtained
from the U.S. Environmental Protection Agency, Environmental
Monitoring and Support Laboratory, Quality Assurance Branch,
Cincinnati, Ohio. Quality control check samples currently are
available for some but not all listed analytes. If measured
analyte concentrations are not within ±20% of true values, check
the entire analytical procedure to locate and correct the problem
source.
10.10 Additional QC procedures may be necessary, depending on the purpose
of the analysis performed with this method.
10.10.1 Laboratory Duplicates To determine precision
associated with laboratory techniques, analyze two
aliquots (Sect. 11.1.2) of a sample in which some
analytes were detected in measurable quantities.
Calculate the range (R) of concentrations measured for
each duplicate pair:
R Ci - Cg,
where CT represents the larger and,
C2 represents the smaller of the two
meas urements.
Calculate percent relative range (RR) of duplicate
analyses using the formula:
-------
RR
R
^^^^
C
100
10.10.2
10.10.3
where R = range of concentrations measured, and
C = mean concentration measured.
Generally, if RR is greater than 30*, precision is
inadequate, and laboratory techniques must be improved.
Field Duplicates Analyze 10% of samples in which some
analytes were detected in measurable quantities to
indicate precision limitations imposed by sampling,
transport and storage techniques as well as laboratory
techniques. If acceptable results are obtained from
analysis of field duplicates, analysis of laboratory
duplicates is usually not necessary.
Matrix Effects Determination To indicate matrix
effects on method efficiency, accuracy and precision when
raw source waters or drinking water during treatment is
to be analyzed, analyze aliquots to which known amounts
of analytes have been added. Because analytes may be
present in the unspiked aliquots, analysis of one or more
unspiked aliquots is necessary to determine initial
concentrations, which are then subtracted from concentra-
tions measured in spiked aliquots. For each analyte the
amount added to determine matrix effects should exceed
twice the amount measured in unspiked aliquots.
11. PROCEDURE
11.1 ANALYSIS PROCEDURES
11.1.1 Initial conditions Adjust the helium purge gas flow rate
to 40 ± 3 mL/min. Attach the sorbent trap to the purging
device, and set the device to the purge mode. Open the
syringe valve located on the sample introduction needle of
the purging chamber.
11.1.2 Sample introduction and purging Remove the plunger from a
25-mL syringe and attach a closed syringe valve. Open the
sample or standard bottle, which has been allowed to come to
ambient temperature, and pour the sample into the syringe
barrel to just short of overflowing. Replace the syringe
plunger and compress the sample. Open the syringe valve and
vent any residual air while adjusting the sample volume to
25.0 ml. (Because this process of taking an aliquot impairs
the integrity of the remaining sample, a second syringe
should be filled at the same time, in case a second analysis
is required.) Add 2 to 20 uL of the spiking solution (Sect.
7.5) of fluorobenzene in methanol through the syringe valve
and close the valve. Attach the syringe and its valve
-------
assembly to the syringe valve on the purging device. Open
the syringe valves and slowly inject the sample into the
purging chamber. Close both valves and purge the sample for
11.0 ± 0.1 min at ambient temperature. Because temperature
affects purging efficiencies of some analytes, purging
chamber temperature must be controlled to maintain constant
(approximately ± 2°C) temperature throughout calibration
and sample analyses. If laboratory temperature is not
controlled adequately, the purging chamber can be placed in
a thermostatically controlled water bath.
11.1.3 Desorption and data acquisition At the conclusion of
purging, adjust the purge and trap apparatus to the desorb
mode, and initiate GC temperature programming, trap heating,
and MS data acquisition. Desorb for 4 min. Transfer
trapped sample components into the GC column by heating the
trap to 18QOC rapidly while it is backflushed with helium
flowing at 20 to 60 mL/min. (If the trap cannot be heated
rapidly, use the GC column as a secondary trap by cooling
the column to < 30°C during desorption.)
11.1.4 Sample chamber rinsing During or after desorption empty
the purging chamber with the sample introduction syringe,
and rinse the chamber with two 25-mL portions of reagent
water.
11.1.5 Trap reconditioning After desorbing the sample for 4 min,
reset the purging device to the purge mode. After 15 s,
close the syringe valve on the purging device to begin gas
flow through the trap. After approximately 7 min, turn off
the trap heater and open the syringe valve to stop gas flow
through the trap. When cool (<25°C), the trap is ready,
for the next sample.
11.1.6 Termination of data acquisition When sample components
have eluted from the GC, terminate MS data acquisition and
store data files on the data system storage device. Use
appropriate data output software to display full range mass
spectra and appropriate extracted ion current profiles
(EICPs). If any ion abundance exceeds the system working
range, dilute the sample aliquot in the second syringe with
reagent water and analyze the diluted aliquot.
11.2 IDENTIFICATION PROCEDURES CRITERIA Tentatively identify a sample
component by comparison of its mass spectrum (after background
subtraction) to a reference spectrum in a collection. Use the
following criteria to confirm a tentative identification:
11.2.1 The GC retention time of the sample component must be within
£ s of the time observed for that same compound when a
calibration solution was analyzed. Calculate the value of £
with the equation:
-------
t - (RT)V3
where RT = observed retention time (in seconds) of the
compound when a calibration solution was analyzed.
11.2.2 All ions that are present above 10% relative abundance in
the mass spectrum of the standard must be present in the
mass spectrum of the sample component and should agree
within absolute 10%. For example, if an ion has a relative
abundance of 30% in the standard spectrum, its abundance in
the sample spectrum should be in the range of 20 to 40%.
11.2.3 Identification is hampered when sample components are not
resolved chromatographically and produce mass spectra
containing ions contributed by more than one analyte.
Because purgeable organic compounds are relatively small
molecules and produce comparatively simple mass spectra,
this is not a significant problem for most method analytes.
When GC peaks obviously represent more than one sample
component (i.e., broadened peak with shoulder(s) or valley
between two or more maxima), appropriate analyte spectra and
background spectra can be selected by.examining EICPs of
characteristic ions for tentatively identified components.
When analytes coelute (i.e., only one GC peak is apparent),
the identification criteria described in Section 11.2.2 can
be met but each analyte spectrum will contain extraneous
ions contributed by the coeluting compound.
11.2.4 Structural isomers that produce very similar mass spectra
can be explicitly identified only if they have sufficiently
different GC retention times. Acceptable resolution is
achieved if the height of the valley between two isomer
peaks is less than 25% of the sum of the two peak heights.
Otherwise, structural isomers are identified as isomeric
pairs.
12. CALCULATIONS
12.1 Complete chromatographic resolution is not necessary for accurate
and precise measurements of analyte concentrations, if unique ions
with adequate intensities are selected for EICPs. For example,
although two listed analytes, 1,1,2,2-tetrachloroethane and
tetracnloroethene, were not resolved with the GC conditions used
and produced mass spectra containing common ions, concentrations
(Table 5) were calculated by measuring appropriate characteristic
ions.
12.1.1 With either the internal or external standard technique,
calculate analyte concentrations with the equation:
Cx . Ax °s .
x AS . RF :v
-------
where Cx = analyte concentration in micrograms per liter;
Ax = integrated ion abundance of a significant
characteristic ion of the sample analyte;
AS » integrated "ion abundance of a significant
characteristic ion of the standard (either
internal or external), in units consistent with
those used for the analyte ion abundance;
RF « response factor (With an external standard,
RF » 1, because the standard is the same
compound as the measured analyte.);
Qs = quantity of internal standard added or quantity
of external standard that produced As> in
micrograms; and
V » purged sample volume in liters.
12.1.2 With the external standard technique, As is .a point on the
concentration calibration curve and is the same number as
AX; QS is the quantity that produces As and also is
obtained from the concentration calibration curve.
12.1.3 For each analyte, select a significant characteristic ion.
When feasible, use the most intense ion in the mass
spectrum; when a less intense ion is more characteristic and
sufficiently intense to provide necessary sensitivity, use
that ion to avoid possible interferences.
13. PRECISION AND ACCURACY
13.1 To obtain method efficiency data (Table 2) and to indicate
anticipated single laboratory accuracy and precision data (Table 5)
for each listed analyte, seven 25-ml aliquots of each of two
solutions of reagent water containing known amounts of analytes
were analyzed with purge and trap procedures and a packed column.
One solution contained 16 ug of analyte per liter of solution; the
other contained 1.6 ug/L. Two direct Injections of appropriate
volumes of secondary dilution standard were interspersed among
purged aliquots. To obtain the data in Table 5, one aliquot of
each of the two laboratory control standards was randomly selected
to be a solution with known true values of analytes. This aliquot
was treated as an external standard, and the other six aliquots of
each of the two solutions were treated as samples.
13.1.1 Except for two listed analytes, mean method efficiency
varied among analytes from 25.0% to 118.7%. Those two
analytes, l,2-dibromo-3-chloropropane and bis(2-chloro-
isopropyl) ether, are very inefficiently purged and were not
detected in aliquots containing 1.6 ug/L; mean method
efficiencies for these two analytes when purged from 16 wg/L
aliquots were 9.4% and 4.3%, respectively (Table 2).
Although for some applications these low efficiencies may
result in unacceptably high detection limits for those
-------
analytes, they can be measured with acceptable accuracy and
precision when present at a concentration of 16 ug/L (Table
5).
13.1.2 With these data, MDLs were calculated using the formula:
HDL Vl.l- -0.99) S-
where:
t(n-l, 1- = 0.99) * Student's t value for the 99% confidence
level with n-1 degrees of freedom, where
n - number of replicates, and
s = standard deviation of replicate analyses.
-------
REFERENCES
1. Glaser, 0. A., D. L. Foerst, G. D. McKee, S. A. Quave, and W. L. Budde,
"Trace Analyses for Wastewaters," Environ. Sci. Techno!. 15, 1426, 1981.
2. "Carcinogens - Working With Carcinogens," Department of Health,
Education, and Welfare, Public Health Service, Center for Disease
Control, National Institute for Occupational Safety and Health ,
Publication No. 77-206, Aug. 1977.
3. "OSHA Safety and Health Standards, General Industry," (29CFR1910),
Occupational Safety and Health Administration, OSHA 2206, (Revised,
January 1976).
4. "Safety in Academic Chemistry Laboratories," American Chemical Society
Publication, Committee on Chemical Safety, 3rd Edition, 1979.
5. "The Determination of Halogenated Chemicals in Water by the Purge and
Trap Method," Method 502.1, EPA 600/4-81-059, U.S. Environmental
Protection Agency, Office of Research and Development, Environmental
Monitoring and Support Laboratory, Cincinnati, OH, April 1981.
6. "The Analysis of Aromatic Chemicals in Water by the Purge and Trap
Method," Method 503.1, EPA 600/4-81-057, U.S. Environmental
Protection Agency,. Office of Research and Development, Environmental
Monitoring and Support Laboratory, Cincinnati, OH, May 1980.
-------
Table 2. Single Laboratory Method Efficiency Data3 for Purgeable
Organic Compounds Measured with GC/MS
Compound
chl oromethane
vinyl chloride
methyl ene chloride
1,1-dichloroethene
bromochl oromethane
trans-1 ,2-dichloroethene
chloroform
1,2-dichloroethane
1,1,1 -tri ch 1 oroethane
carbon tetrachloride
bromodi chl oromethane
1 , 1 ,2-tri ch loroethane
trichloroethene
benzene
chlorodibromomethane
cis-l,3-dich1oropropene
fluorobenzene
Measured
Ion
50
62
84
96
128
96
83
62
97
117
83
97
130
78
129
75
96
Rel.
Ret.
Timeb
0.10
0.14
0.22
0.28
0.30
0.31
0.44
0.50
0.59
0.62
0.66
0.79
0.84
0.88
0.88
0.90
1.00
True
Cone.
ug/L
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16 '
1.6
16
1.6
16
Mean Method
Efficiency
108.5
53.8
118.7
81.9
93.8
88.1
68.8
65.0
50. OC
98. 8C
93.8
92.5
62.5
55.6
93.8
90.6
106.2
110.0
81.3
80.6
.18.8C
50. QC
100.0
106.9
106.2
96.3
58.8
53.8
25. QC
70. Oc
100.0
95.6
Rel.
Std.
Dev., %
15.2
13.6
4.9
7.6
5.1
7.9
5.8
6.2
30. 5C
12. 6C
3.8
2.1
12.6
7.1
3.8
2.9
2.2
1.9
5.9
5.4
33. 5C
15.9C
3.0
1.2
2.9
2.2
6.0
11.3
31. 6C
11.8C
7.4
11.1
-------
Table 2. (continued)
Compound
bromoform
1,1,2,2-tetrachloroethane
tetrachl oroethene
tol uene
chlorobenzene
1 ,2-dibromo-3-ch loropropane0"
4-bromof 1 uorobenzene
styrene
p-xylene
bis(2-ch1oroisopropyl) etherd
1,3-dichlorobenzene
1 ,2-di chl orobenzene
Measured
Ion
173
83
164
92
112
157
174
104
106
45
146
146
Rel.
Ret.
Timeb
1.10
1.29
1.31
1.42
1.52
1.70
1.82
1.93
1.97
2.08
2.19
2.20
True
Cone.
ug/L
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
16
1.6
16
1.6
16
Mean Method
Efficiency
%
39.4
35.0
28.1
25.0
106.2
107.5
100.0
102.5
93.8
96.3
1-d
9.4C
93.8
93.8
68. 8C
86. 9C
100.0
103.1
4.3
75. OC
82. 5<=
81.3
79.4
Rel.
Std.
Dev %
7.0
6.3
5.9
6.3
0.0
4.6
3.2
1.5
3.5
2.2
lid
10.3C
5.4
4.0
29. 2C
13.3C
3.0
1.5
14.3
28. 3C
10.3C
5.9
4.2
a Except as noted, data were produced by purging seven aliquots of reagent
water spiked with known amounts of listed compounds; calculations involved two
direct injections.
b SC column: 1.8 m x 2 mm ID glass packed with 1% SP-1000 on 60/80 mesh
carbopack B. Program: 45°C for 4 min; 8°C/min to 230°C.
Retention time relative to fluorobenzene, which has retention time of 11.1 min
under described GC conditions.
c Produced by analysis of six aliquots rather than seven.
d Compound is very inefficiently purged from water and was not detected in
aliquots of 1.6 ug/L solution.
-------
Table 1. Ion Abundance Criteria for p_-Bromofluorobenzene
Mass Ion Abundance Criteria
50
75
95
96
173
174
175
176
177
15 to 40% of mass 95
30 to 60% of mass 95
Base Peak, 100% Relative Abundance
5 to 9% of mass 95
< 2% of mass 174
> 50% of mass 95
5 to 9% of mass 174
> 95% but < 101% of mass 174
5 to 9% of mass 176
-------
Table 3 (continued)
Demonstrated Acceptable
Analyte Storage Time,
Days
2-chloroethylethyl ether 27
2-chloroethylvinyl ether 27
bis-2-chloroethyl ether 9b
bis-2-chloroisopropyl ether 27
a These data were obtained by multiple analyses of raw river water and
carbon-filtered chlorinated tap water to which known amounts (0.20 to 0.50
ug/L) of listed analytes had been added. Some samples were stored and
analyzed periodically over a 21-day period; others, over a 27-day period.
Data from "The Determination, of Halogenated Chemicals in Water by the
Purge and Trap Method," Method 502.1, EPA 600/4-81-059, U.S. Environmental
Protection Agency, Office of Research and Development, Environmental
Monitoring and Support Laboratory, Cincinnati, OH, April 1981.
b Because of observed changes during storage, this number is the maximum
recommended storage time.
-------
Table 3. Acceptable Storage Times3 for River and Drinking
Water Samples Containing Halogenated Aliphatic Analytes
Demonstrated Acceptable
Analyte Storage Time,
Days
chloromethane 21
dichloromethane 27
carbon tetrachloride 27
bromomethane 2b
dibromomethane 21
bromoform 27
bromochloromethane 21
bromodichloromethane 27
chlorodibromomethane 27
dichlorodifluoromethane 27
fluorotrichloromethane 27
chloroethane 21
1,1-dichloroethane 27
1,2-dichloroethane 27
1,1,1-trichloroethane 21
1,1,2-trichloroethane 27
1,1,1,2-tetrachloroethane 21
pentach1oroethane 27
1,2-dibromoethane 21
chloroethylene (vinyl chloride) 6b
1,1-dichloroethylene 27
cis + trans-1,2-dichloroethylene 27
cis-l,2-dichloroethylene 21
1,1,2-trichloroethylene 27
1,1,2,2-tetrachloroethylene 27
1,2-dichloropropane 21
1,3-dichloropropane 21
1,2,3-trichloropropane 21
3-chloroprop-l-ene (ally! chloride) 2b
1,1-dichloroprop-l-ene 27
2,3-dichloroprop-l-ene °.
trans-l,3-dichloroprop-l-ene ]"
cis-l,3-dichloroprop-l-ene lu
1-chlorohexane ]
chlorocyclohexane u
1-chlorocyclohex-l-ene Z7
-------
Table 4. Storage Time Data3 for River and Drinking
Water Samples Containing Aromatic Analytes
Analyte
Percent Recovery From
River Water on Day 1
Preserved*1 Unpreserved
Acceptable0 Storage Time
In Days
Drinking Preserved
Water River Water
Observed
Average Decay
Rate (%/Day) In
Preserved River Water
benzene
toluene
ethyl benzene
o-xylene
m-xylene
p-xylene
ethenyl benzene (styrene)
n-propylbenzene
isopropyl benzene
n -butyl benzene
sec-butylbenzene
ter -butyl benzene
1-methyl -4- 1 sopropylbenzene
1 , 2, 4 -tr1 methyl benzene
1 ,3,5-tr1methylbenzene
chlorobenzene
bromobenzene
o -d i ch 1 oro ben zene
m-di chl orobenzene
p-di chlorobenzene
1 ,2, 3-tri chlorobenzene
1,2,4-trlchlorobenzene
o-chlorotoluene
p-chlorotoluene
<*-trifluorotoluene
100
98
95
95
93
88
83
88
93
88
88
90
88
85
88
90
90
96
96
94
86
88
--
90
84
12
8
10
12
17
12
0
15
0
3
10
43
34
16
5
23
17
85
96
90
97
88
»
45
74
15
15
15
15
15
15,
0<«
15
15
156
15
15
6
15^
28
28
28
28
28
28
28
28
21
13
28
14
14
*
__
_-
*
~
M*»
26
26
26
26
26
26
26
26
26
1.4
1.6
1.6
2.3
4.2
2.2
1.5
3.2
2.2
10
2.3
3.0
2.1
a Data from "The Determination of Aromatic Chemicals 1n Water by the Purge and Trap Method," Method 503.1,
EPA 600/4-81-057, U.S. Environmental Protection Agency, Office of Research and Development, Environmental
Monitoring and Support Laboratory, Cincinnati, OH, May 1980, and from "The Determination of Halogenated
Chemicals in Water by the Purge and Trap Method," Method 502.1, EPA 600/4-81-059, U.S. Environmental
Protection Agency, Office of Research and Development, Environmental Monitoring and Support Laboratory,
Cincinnati, OH, April 1981.
b Preservation was accomplished by adjustment of sample pH to 2.
c Data were obtained by multiple analyses of carbon-filtered tap water and preserved river water to which
known amounts (0.40 or 0.50 pg/L) of listed analytes had been added. Mean recovery of analyte was ^ 80%
except as noted.
d Styrene, which reacts with free chlorine was not detected in chlorinated drinking water.
f Mean recovery of 78$.
f Mean recovery of 75%.
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Table 5. Anticipated Accuracy and Precision Data with Method
(Single Laboratory and Single Operator)
Compound
chloromethane
vinyl chloride
methyl ene chloride
1 , 1-di chl oroethene
bromochl oromethane
trans-l,2-dichloroethene
chloroform
1,2-dichloroethane
1,1, 1-tri chl oroethane
carbon tetrachloride
bromodi chl oromethane
1 , 1 ,2-tri chloroethane
tri chl oroethene
benzene
chl orodibromome thane
cis-l,3-dichloropropene
fluoro benzene
Measured
Ion
50
62
84
96
128
96
83
62
97
117
83
97
130
78
129
75
96
Rel.
Ret.
T1meb
0.10
0.14
0.22
0.28
0.30
0.31
0.44
0.50
0.59
0.62
0.66
0.79
0.84
0.88
0.88
0.90
1.00
True
Cone.
yg/L
Oe
16
Oe
16
1.6
16
1.6
16
1.6
16
1.6,
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
Mean
Observed
Cone., yg/L
16.5
18.2
1.6
15.8
1.6
16.3
1.6
15.6
1.3
15.4
1.6
16.0
1.6
16.0
1.6
16.2
1.6
16.0
1.6
15.8
1.3
15.9
1.6
16.0
1.6
16.1
1.6
15.0
1.3
15.0
Std.
Dev.
yg/L
2.7
2.5
0.08
0.3
0.08
1.8
0.08
1.4
0.5
2.2
0.06
0.32
0.1
1.7
0.04
0.8
0.04
0.4
0.09
0.5
0.3
2.5
0.05
0.2
0.06
0.5
0.1
2.0
0.5
1.8
Rel.
Std.
Dev.,%
16.6
13.9
4.8
2.1
4.9
10.8
5.2
9.2
37.9
14.5
3.8
2.0
6.7
10.5
2.4
4.9
2.3
2.4
5.5
3.2
23.1
15.9
3.3
1.1
4.0
3.1
6.5
13.6
36.9
11.7
Mean Method
Accuracy
103.1
113.8
100
98.8
100
101.9
100
97.5
81.3
96.3
100
100
100
100
100
101.3
100
100
100
98.8
81.3
99.4
100
100
100
100.6
100
93.8
81.3
93.8
Method
Detection
Limit0, yg/L
9.2
8.5
0.25
0.27
0.28
1.7
0.20
-_
0.35
0.13
__
0.13
_«.
0.29
__
1.0
....
0.18
«._
0.21
«.
0.34
mmmm
1.8
.*
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Table 5. (continued)
Compound
bromoform
1 ,1 ,2,2-tetrachloroethane
tetrachloroethene
toluene
chlorobenzene
1 ,2-d1bromo-3-chloropropane('
4-bromofluorobenzene
styrene
p-xylene
b1s(2-chloro1sopropyl) ether**
1 ,3-dichlorobenzene
1,2-di chlorobenzene
Measured
Ion
173
83
164
92
112
157
174
104
106
45
146
146
Rel.
Ret.
T1meb
1.10
1.29
1.31
1.42
1.52
1.70
1.82
1.93
1.97
2.08
2.19
2.20
True
Cone.
V9/L
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
1.6
16
Mean
Observed
Cone., ug/J.
1.5
15.5
1.6
15.5
1.6
15.8
1.6
15.9
1.6
15.7
__d
15.7
1.5
15.6
1.2
15.8
1.6
16.1
_-d
15.1
1.2
15.2
1.5
15.7
Std.
Dev.
uq/L
0.1
2.0
0.08
1.8
0.02
0.4
0.02
0.3
0.03
0.6
_.d
3.0
0.09
1.1
0.3
1.6
0.05
0.2
_.d
2.3
0.3
1.5
0.09
1.3
Rel.
Std.
Dev.,%
6.5
12.7
5.3
11.5
1.3
2.4
1.4
1.6
1.6
3.6
__d
19.1
5.6
7.3
29.0
10.4
3.4
1.0
__d
15.1
28.0
9,8
6.2
8.3
Mean Method
Accuracy
%
93.8
96.9
100
96.9
100
98.8
100
99.4
100
98.1
__d
98.1
93.8
97.5
75.0
98.8
100
100.6
-_d
94.4
75.0
95.0
93.8
98.1
Method
Detection
L1m1tc,ug/L
0.34
M»
0.28
__
0.07
__
0.08
__
0.09
-d
«
10. ld
0.29
--
1.3
0.18
_
_.d
j
8.6d
1.3
-
0.30
-
a Produced by analysis of seven allquots of reagent water spiked with known amounts of listed compounds;
calculations based on external standard technique. Two allquots were treated as standards; five
allquots were treated as samples.
b GC column: 1.8 m x 2 mm ID glass packed with 1% SP-1000 on 60/80 mesh Carbopack B, Retention times
relative to fluorobenzene.
c Minimum concentration that can be measured with 995t confidence that reported value Is greater than
zero.1
d Compound is inefficiently purged and was not detected 1n 1.6 ug/L solution; MDL was calculated from
analysis of 16 yg/L solution.
e Compound not analyzed at concentration of 1.6 ug/L.
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