EPA 524.2

EPA 524.2
METHOD 524.2
MEASUREMENT OF PURGEABLE ORGANIC COMPOUNDS IN WATER BY
CAPILLARY COLUMN GAS CHROMATOGRAPHY/MASS SPECTROMETRY
Revision 4.0
August 1992
A. Alford-Stevens, J. W. Eichelberger, and W.L. Budde
Method 524, Revision 1.0 (1983)
R.W. Slater, Jr.
Revision 2.0 (1986)
J.W. Eichelberger, and W.L. Budde
Revision 3.0 (1989)
J.W. Eichelberger, J.W. Munch, and T.A.Bellar
Revision 4.0 (1992)
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
METHOD 524.2
524.2-1
MEASUREMENT OF PURGEABLE ORGANIC COMPOUNDS IN WATER BY
CAPILLARY COLUMN GAS CHROMATOGRAPHY/MASS SPECTROMETRY
1.0
SCOPE AND APPLICATION
1.1
This is a general purpose method for the identification and simultaneous
measurement of purgeable volatile organic compounds in surface water, ground
water, and drinking water in any stage of treatment1,2. The method is applicable
to a wide range of organic compounds, including the four trihalomethane
disinfection by-products, that have sufficiently high volatility and low water
solubility to be removed from water samples with purge and trap procedures.
The following compounds can be determined by this method.
Compound
Acetone*
Acrylonitrile*
Allyl chloride*
Benzene
Bromobenzene
Bromochloromethane
Bromodichloromethane
Bromoform
Bromomethane
2-Butanone*
n-Butylbenzene
sec-Butylbenzene
tert-Butylbenzene
Carbon disulfide*
Carbon tetrachloride
Chloroacetonitrile*
Chlorobenzene
1-Chlorobutane*
Chloroethane
Chloroform
Chloromethane
2-Chlorotoluene
4-Chlorotoluene
Dibromochloromethane
1,2-Dibromo-3-chloropropane
1,2-Dibromoethane
Dibromomethane
1,2-Dichlorobenzene
1,3-Dichlorobenzene
1,,4-Dichlorobenzene
524.2-2
Chemical Abstract Service
Registry Number
67-64-1
107-13-1
107-05-1
71-43-2
108-86-1
74-97-5
75-27-4
75-25-2
74-83-9
78-93-3
104-51-8
135-98-8
98-06-6
75-15-0
56-23-5
107-14-2
108-90-7
109-69-3
75-00-3
67-66-3
74-87-3
95-49-8
106-43-4
124-48-1
96-12-8
106-93-4
74-95-3
95-50-1
541-73-1
106-46-7
Compound
trans-1,4-Dichloro-2-butene*
Dichlorodifluoromethane
1,1-Dichloroethane
1,2-Dichloroethane
1,1-Dichloroethene
cis-1,2-Dichloroethene
trans-1,2-Dichloroethene
1,2-Dichloropropane
1,3-Dichloropropane
2,2-Dichloropropane
1,1-Dichloropropene
1,1-Dichloropropanone*
cis-1,3-Dichloropropene
trans-1,3-Dichloropropene
Diethyl ether*
Ethylbenzene
Ethyl methacrylate*
Hexachlorobutadiene
Hexachloroethane*
2-Hexanone*
Isopropylbenzene
4-Isopropyltoluene
Methacrylonitrile*
Methylacrylate*
Methylene chloride
Methyl iodide*
Methylmethacrylate*
4-Methyl-2-pentanone*
Methyl-t-butyl ether*
Naphthalene
Nitrobenzene*
2-Nitropropane*
Pentachloroethane*
Propionitrile*
n-Propylbenzene
Styrene
1,1,1,2-Tetrachloroethane
1,1,2,2-Tetrachloroethane
Tetrachloroethene
Tetrahydrofuran*
Toluene
1,2,3-Trichlorobenzene
1,2,4-Trichlorobenzene
1,1,1-Trichloroethane
1,1,2-Trichloroethane
Trichloroethene
Trichlorofluoromethane
524.2-3
Chemical Abstract Service
Registry Number
110-57-6
75-71-8
75-34-3
107-06-2
75-35-4
156-59-4
156-60-5
78-87-5
142-28-9
590-20-7
563-58-6
513-88-2
10061-01-5
10061-02-6
60-29-7
100-41-4
97-63-2
87-68-3
67-72-1
591-78-6
98-82-8
99-87-6
126-98-7
96-33-3
75-09-2
74-88-4
80-62-6
108-10-1
1634-04-4
91-20-3
98-95-3
79-46-9
76-01-7
107-12-0
103-65-1
100-42-5
630-20-6
79-34-5
127-18-4
109-99-9
108-88-3
87-61-6
120-82-1
71-55-6
79-00-5
79-01-6
75-69-4
Compound
1,2,3-Trichloropropane
1,2,4-Trimethylbenzene
1,3,5-Trimethylbenzene
Vinyl chloride
o-Xylene
m-Xylene
p-Xylene
Chemical Abstract Service
Registry Number
96-18-4
95-63-6
108-67-8
75-01-4
95-47-6
108-38-3
106-42-3
*New Compound in Revision 4.0.
2.0
1.2
Method detection limits (MDLs)3 are compound, instrument and especially matrix
dependent and vary from approximately 0.02-1.6 µg/L. The applicable
concentration range of this method is primarily column and matrix dependent,
and is approximately 0.02-200 µg/L when a wide-bore thick-film capillary column
is used. Narrow-bore thin-film columns may have a capacity which limits the
range to about 0.02-20 µg/L. Volatile water soluble, polar compounds which
have relatively low purging efficiencies can be determined using this method.
Such compounds may be more susceptible to matrix effects, and the quality of the
data may be adversely influenced.
1.3
Analytes that are not separated chromatographically, but which have different
mass spectra and noninterfering quantitation ions (Table 1), can be identified and
measured in the same calibration mixture or water sample as long as their
concentrations are somewhat similar (Section 11.6.2). Analytes that have very
similar mass spectra cannot be individually identified and measured in the same
calibration mixture or water sample unless they have different retention times
(Section 11.6.3). Coeluting compounds with very similar mass spectra, typically
many structural isomers, must be reported as an isomeric group or pair. Two of
the three isomeric xylenes and two of the three dichlorobenzenes are examples of
structural isomers that may not be resolved on the capillary column, and if not,
must be reported as isomeric pairs. The more water soluble compounds (>2%
solubility) and compounds with boiling points above 200°C are purged from the
water matrix with lower efficiencies. These analytes may be more susceptible to
matrix effects.
SUMMARY OF METHOD
2.1
Volatile organic compounds and surrogates with low water solubility are
extracted (purged) from the sample matrix by bubbling an inert gas through the
aqueous sample. Purged sample components are trapped in a tube containing
suitable sorbent materials. When purging is complete, the sorbent tube is heated
and backflushed with helium to desorb the trapped sample components into a
capillary gas chromatography (GC) column interfaced to a mass spectrometer
(MS). The column is temperature programmed to facilitate the separation of the
method analytes which are then detected with the MS. Compounds eluting from
the GC column are identified by comparing their measured mass spectra and
retention times to reference spectra and retention times in a data base. Reference
524.2-4
spectra and retention times for analytes are obtained by the measurement of
calibration standards under the same conditions used for samples. The
concentration of each identified component is measured by relating the MS
response of the quantitation ion produced by that compound to the MS response
of the quantitation ion produced by a compound that is used as an internal
standard. Surrogate analytes, whose concentrations are known in every sample,
are measured with the same internal standard calibration procedure.
3.0
DEFINITIONS
3.1
Internal Standard (IS) -- A pure analyte(s) added to a sample, extract, or standard
solution in known amount(s) and used to measure the relative responses of other
method analytes and surrogates that are components of the same sample or
solution. The internal standard must be an analyte that is not a sample
component.
3.2
Surrogate Analyte (SA) -- A pure analyte(s), which is extremely unlikely to be
found in any sample, and which is added to a sample aliquot in known
amount(s) before extraction or other processing and is measured with the same
procedures used to measure other sample components. The purpose of the SA
is to monitor method performance with each sample.
3.3
Laboratory Duplicates (LD1 and LD2) -- Two aliquots of the same sample taken
in the laboratory and analyzed separately with identical procedures. Analyses of
LD1 and LD2 indicates precision associated with laboratory procedures, but not
with sample collection, preservation, or storage procedures.
3.4
Field Duplicates (FD1 and FD2) -- Two separate samples collected at the same
time and place under identical circumstances and treated exactly the same
throughout field and laboratory procedures. Analyses of FD1 and FD2 give a
measure of the precision associated with sample collection, preservation and
storage, as well as with laboratory procedures.
3.5
Laboratory Reagent Blank (LRB) -- An aliquot of reagent water or other blank
matrix that is treated exactly as a sample including exposure to all glassware,
equipment, solvents, reagents, internal standards, and surrogates that are used
with other samples. The LRB is used to determine if method analytes or other
interferences are present in the laboratory environment, the reagents, or the
apparatus.
3.6
Field Reagent Blank (FRB) -- An aliquot of reagent water or other blank matrix
that is placed in a sample container in the laboratory and treated as a sample in
all respects, including shipment to the sampling site, exposure to sampling site
conditions, storage, preservation, and all analytical procedures. The purpose of
the FRB is to determine if method analytes or other interferences are present in
the field environment.
3.7
Laboratory Performance Check Solution (LPC) -- A solution of one or more
compounds (analytes, surrogates, internal standard, or other test compounds)
524.2-5
used to evaluate the performance of the instrument system with respect to a
defined set of method criteria.
4.0
3.8
Laboratory Fortified Blank (LFB) -- An aliquot of reagent water or other blank
matrix to which known quantities of the method analytes are added in the
laboratory. The LFB is analyzed exactly like a sample, and its purpose is to
determine whether the methodology is in control, and whether the laboratory is
capable of making accurate and precise measurements.
3.9
Laboratory Fortified Sample Matrix (LFM) -- An aliquot of an environmental
sample to which known quantities of the method analytes are added in the
laboratory. The LFM is analyzed exactly like a sample, and its purpose is to
determine whether the sample matrix contributes bias to the analytical results.
The background concentrations of the analytes in the sample matrix must be
determined in a separate aliquot and the measured values in the LFM corrected
for background concentrations.
3.10
Stock Standard Solution (SSS) -- A concentrated solution containing one or more
method analytes prepared in the laboratory using assayed reference materials or
purchased from a reputable commercial source.
3.11
Primary Dilution Standard Solution (PDS) -- A solution of several analytes
prepared in the laboratory from stock standard solutions and diluted as needed
to prepare calibration solutions and other needed analyte solutions.
3.12
Calibration Standard (CAL) -- A solution prepared from the primary dilution
standard solution or stock standard solutions and the internal standards and
surrogate analytes. The CAL solutions are used to calibrate the instrument
response with respect to analyte concentration.
3.13
Quality Control Sample (QCS) -- A solution of method analytes of known
concentrations which is used to fortify an aliquot of LRB or sample matrix. The
QCS is obtained from a source external to the laboratory and different from the
source of calibration standards. It is used to check laboratory performance with
externally prepared test materials.
INTERFERENCES
4.1
During analysis, major contaminant sources are volatile materials in the
laboratory and impurities in the inert purging gas and in the sorbent trap. The
use of Teflon tubing, Teflon thread sealants, or flow controllers with rubber
components in the purging device should be avoided since such materials out-gas
organic compounds which will be concentrated in the trap during the purge
operation. Analyses of laboratory reagent blanks provide information about the
presence of contaminants. When potential interfering peaks are noted in
laboratory reagent blanks, the analyst should change the purge gas source and
regenerate the molecular sieve purge gas filter. Subtracting blank values from
sample results is not permitted.
524.2-6
5.0
6.0
4.2
Interfering contamination may occur when a sample containing low
concentrations of volatile organic compounds is analyzed immediately after a
sample containing relatively high concentrations 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, one or more
laboratory reagent blanks should be analyzed to check for cross-contamination.
4.3
Special precautions must be taken to determine methylene chloride. The
analytical and sample storage area should be isolated from all atmospheric
sources of methylene chloride, otherwise random background levels will result.
Since methylene chloride will permeate Teflon tubing, all GC carrier gas lines and
purge gas plumbing should be constructed of stainless steel or copper tubing.
Laboratory worker's clothing should be cleaned frequently since clothing
previously exposed to methylene chloride fumes during common liquid/liquid
extraction procedures can contribute to sample contamination.
4.4
Traces of ketones, methylene chloride, and some other organic solvents can be
present even in the highest purity methanol. This is another potential source of
contamination, and should be assessed before standards are prepared in the
methanol.
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,
and 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 available4-6 for the information of the analyst.
5.2
The following method analytes have been tentatively classified as known or
suspected human or mammalian carcinogens: benzene, carbon tetrachloride,
1,4-dichlorobenzene,
1,2-dichlorethane,
hexachlorobutadiene,
1,1,2,2-tetrachloroethane,
1,1,2-trichloroethane,
chloroform,
1,2-dibromoethane,tetrachloroethene, trichloroethene, and vinyl chloride. Pure
standard materials and stock standard solutions of these compounds should be
handled in a hood. A NIOSH/MESA approved toxic gas respirator should be
worn when the analyst handles high concentrations of these toxic compounds.
EQUIPMENT AND SUPPLIES
6.1
Sample Containers -- 40-120 mL screw cap vials each equipped with a Teflon
faced silicone septum. Prior to use, wash vials and septa with detergent and rinse
with tap and distilled water. Allow the vials and septa to air dry at room
temperature, place in a 105°C oven for one hour, then remove and allow to cool
in an area known to be free of organics.
524.2-7
6.2
Purge and Trap System -- The purge and trap system consists of three separate
pieces of equipment: purging device, trap, and desorber. Systems are
commercially available from several sources that meet all of the following
specifications.
6.2.1
The all glass purging device (Figure 1) should be designed to accept
25 mL samples with a water column at least 5 cm deep. A smaller (5 mL)
purging device is recommended if the GC/MS system has adequate
sensitivity to obtain the method detection limits required. Gaseous
volumes above the sample must be kept to a minimum (<15 mL) to
eliminate dead volume effects. A glass frit should be installed at the base
of the sample chamber so the purge gas passes through the water column
as finely divided bubbles with a diameter of <3 mm at the origin. Needle
spargers may be used, however, the purge gas must be introduced at a
point about 5 mm from the base of the water column. The use of a
moisture control device is recommended to prohibit much of the trapped
water vapor from entering the GC/MS and eventually causing
instrumental problems.
6.2.2
The trap (Figure 2) must be at least 25 cm long and have an inside
diameter of at least 0.105 in. Starting from the inlet, the trap should
contain 1.0 cm of methyl silicone coated packing and the following
amounts of adsorbents:
of 2,6-diphenylene oxide polymer,
of silica
gel, and
of coconut charcoal. If it is not necessary to determine
dichlorodifluoromethane, the charcoal can be eliminated and the polymer
increased to fill
of the trap. Before initial use, the trap should be
conditioned overnight at 180°C by backflushing with an inert gas flow of
at least 20 mL/min. Vent the trap effluent to the room, not to the
analytical column. Prior to daily use, the trap should be conditioned for
10 minutes at 180°C with backflushing. The trap may be vented to the
analytical column during daily conditioning; however, the column must
be run through the temperature program prior to analysis of samples.
The use of alternative sorbents is acceptable, depending on the particular
set of target analytes or other problems encountered, but the new trap
packing must meet all quality control criteria described in Section 9.0.
a
a
a
b
6.2.3
The use of the methyl silicone coated packing is recommended, but not
mandatory. The packing serves a dual purpose of protecting the Tenax
adsorbant from aerosols, and also of insuring that the Tenax is fully
enclosed within the heated zone of the trap thus eliminating potential cold
spots. Alternatively, silanized glass wool may be used as a spacer at the
trap inlet.
6.2.4
The desorber (Figure 2) must be capable of rapidly heating the trap to
180°C either prior to or at the beginning of the flow of desorption gas.
The polymer section of the trap should not be heated higher than 200°C
or the life expectancy of the trap will decrease. Trap failure is
characterized by a pressure drop in excess of 3 lb/in2 across the trap
524.2-8
during purging or by poor bromoform sensitivities. The desorber design
illustrated in Figure 2 meets these criteria.
6.3
Gas Chromatography/Mass Spectrometer/Data System (GC/MS/DS)
6.3.1
The GC must be capable of temperature programming and should be
equipped with variable-constant differential flow controllers so that the
column flow rate will remain constant throughout desorption and
temperature program operation. If the column oven is to be cooled to
10°C or lower, a subambient oven controller will likely be required. If
syringe injections of 4-bromofluorobenzene (BFB) will be used, a
split/splitless injection port is required.
6.3.2
Capillary GC Columns -- Any gas chromatography column that meets the
performance specifications of this method may be used (Section 10.2.4.1).
Separations of the calibration mixture must be equivalent or better than
those described in this method. Four useful columns have been evaluated,
and observed compound retention times for these columns are listed in
Table 2.
6.3.2.1 Column 1 -- 60 m x 0.75 mm ID VOCOL (Supelco, Inc.) glass
wide-bore capillary with a 1.5 µm film thickness.
Column 2 -- 30 m x 0.53 mm ID DB-624 (J&W Scien-tific, Inc.)
fused silica capillary with a 3 µm film thickness.
Column 3 -- 30 m x 0.32 mm ID DB-5 (J&W Scientific, Inc.) fused
silica capillary with a 1 µm film thickness.
Column 4 -- 75 m x 0.53 mm id DB-624 (J&W Scien-tific, Inc.) fused
silica capillary with a 3 µm film thickness.
6.3.3
Interfaces between the GC and MS -- The interface used depends on the
column selected and the gas flow rate.
6.3.3.1 The wide-bore Columns 1, 2, and 4 have the capacity to accept the
standard gas flows from the trap during thermal desorption, and
chromatography can begin with the onset of thermal desorption.
Depending on the pumping capacity of the MS, an additional
interface between the end of the column and the MS may be
required. An open split interface7 or an all-glass jet separator is an
acceptable interface. Any interface can be used if the performance
specifications described in this method (Section 9.0 and 10.0) can
be achieved. The end of the transfer line after the interface, or the
end of the analytical column if no interface is used, should be
placed within a few mm of the MS ion source.
6.3.3.2 When narrow-bore Column 3 is used, a cryogenic interface placed
just in front of the column inlet is suggested. This interface
condenses the desorbed sample components in a narrow band on
an uncoated fused silica precolumn using liquid nitrogen cooling.
524.2-9
When all analytes have been desorbed from the trap, the interface
is rapidly heated to transfer them to the analytical column. The
end of the analytical column should be placed within a few mm of
the MS ion source. A potential problem with this interface is
blockage of the interface by frozen water from the trap. This
condition will result in a major loss in sensitivity and
chromatographic resolution.
6.4
6.5
6.3.4
The mass spectrometer must be capable of electron ionization at a nominal
electron energy of 70 eV. The spectrometer must be capable of scanning
from 35-260 amu with a complete scan cycle time (including scan
overhead) of two seconds or less. (Scan cycle time = Total MS data
acquisition time in seconds divided by number of scans in the
chromatogram.) The spectrometer must produce a mass spectrum that
meets all criteria in Table 3 when 25 ng or less of 4-bromofluorobenzene
(BFB) is introduced into the GC. An average spectrum across the BFB GC
peak may be used to test instrument performance.
6.3.5
An interfaced data system is required to acquire, store, reduce, and output
mass spectral data. The computer software should have the capability of
processing stored GC/MS data by recognizing a GC peak within any
given retention time window, comparing the mass spectra from the GC
peak with spectral data in a user-created data base, and generating a list
of tentatively identified compounds with their retention times and scan
numbers. The software must allow integration of the ion abundance of
any specific ion between specified time or scan number limits. The
software should also allow calculation of response factors as defined in
Section 10.2.6 (or construction of a linear or second order regression
calibration curve), calculation of response factor statistics (mean and
standard deviation), and calculation of concentrations of analytes using
either the calibration curve or the equation in Section 12.0.
Syringe and Syringe Valves
6.4.1
Two 5 mL or 25 mL glass hypodermic syringes with Luer-Lok tip
(depending on sample volume used).
6.4.2
Three two-way syringe valves with Luer ends.
6.4.3
Micro syringes -- 10, 100 µL.
6.4.4
Syringes -- 0.5, 1.0, and 5 mL, gas tight with shut-off valve.
Miscellaneous
6.5.1
7.0
Standard solution storage containers -- 15 mL bottles with Teflon lined
screw caps.
REAGENTS AND STANDARDS
7.1
Trap Packing Materials
524.2-10
7.2
7.3
7.1.1
2,6-Diphenylene oxide polymer, 60/80 mesh, chromatographic grade
(Tenax GC or equivalent).
7.1.2
Methyl silicone packing (optional) -- OV-1 (3%) on Chromosorb W, 60/80
mesh, or equivalent.
7.1.3
Silica gel -- 35/60 mesh, Davison, grade 15 or equivalent.
7.1.4
Coconut charcoal -- Prepare from Barnebey Cheney, CA-580-26 lot
#M-2649 by crushing through 26 mesh screen.
Reagents
7.2.1
Methanol -- Demonstrated to be free of analytes.
7.2.2
Reagent water -- 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 minutes followed
by a one hour purge with inert gas while the water temperature is held
at 90°C. Store in clean, narrow-mouth bottles with Teflon lined septa and
screw caps.
7.2.3
Hydrochloric acid (1+1) -- Carefully add measured volume of conc. HCl
to equal volume of reagent water.
7.2.4
Vinyl chloride -- Certified mixtures of vinyl chloride in nitrogen and pure
vinyl chloride are available from several sources (for example, Matheson,
Ideal Gas Products, and Scott Gases).
7.2.5
Ascorbic acid -- ACS reagent grade, granular.
7.2.6
Sodium thiosulfate -- ACS reagent grade, granular.
Stock Standard Solutions -- These solutions may be purchased as certified
solutions or prepared from pure standard materials using the following
procedures. One of these solutions is required for every analyte of concern, every
surrogate, and the internal standard. A useful working concentration is about
1-5 mg/mL.
7.3.1
Place about 9.8 mL of methanol into a 10 mL ground-glass stoppered
volumetric flask. Allow the flask to stand, unstoppered, for about 10
minutes or until all alcohol-wetted surfaces have dried and weigh to the
nearest 0.1 mg.
7.3.2
If the analyte is a liquid at room temperature, use a 100 µL syringe and
immediately add two or more drops of reference standard to the flask. Be
sure that the reference standard falls directly into the alcohol without
contacting the neck of the flask. If the analyte is a gas at room
temperature, fill a 5 mL valved gas-tight syringe with the standard to the
524.2-11
5.0 mL mark, lower the needle to 5 mm above the methanol meniscus, and
slowly inject the standard into the neck area of the flask. The gas will
rapidly dissolve in the methanol.
7.3.3
Reweigh, dilute to volume, stopper, then mix by inverting the flask several
times. Calculate the concentration in µg/µL from the net gain in weight.
When compound purity is certified at 96% or greater, the weight can be
used without correction to calculate the concentration of the stock
standard.
7.3.4
Store stock standard solutions in 15 mL bottles equipped with Teflon lined
screw caps. Methanol solutions of acrylonitrile, methyl iodide, and methyl
acrylate are stable for only one week at 4°C. Methanol solutions prepared
from other liquid analytes are stable for at least four weeks when stored
at 4°C. Methanol solutions prepared from 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
Primary Dilution Standards -- Use stock standard solutions to prepare primary
dilution standard solutions that contain all the analytes of concern in methanol
or other suitable solvent. The primary dilution standards should be prepared at
concentrations that can be easily diluted to prepare aqueous calibration solutions
that will bracket the working concentration range. Store the primary dilution
standard solutions with minimal headspace and check frequently for signs of
deterioration or evaporation, especially just before preparing calibration solutions.
Storage times described for stock standard solutions in Section 7.3.4 also apply to
primary dilution standard solutions.
7.5
Fortification Solutions for Internal Standard and Surrogates
7.5.1
7.6
A solution containing the internal standard and the surrogate compounds
is required to prepare laboratory reagent blanks (also used as a laboratory
performance check solution), and to fortify each sample. Prepare a
fortification solution containing fluorobenzene (internal standard),
1,2-dichlorobenzene-d4 (surrogate), and BFB (surrogate) in methanol at
concentrations of 5 µg/mL of each (any appropriate concentration is
acceptable). A 5 µL aliquot of this solution added to a 25 mL water
sample volume gives concentrations of 1 µg/L of each. A 5 µL aliquot of
this solution added to a 5 mL water sample volume gives a concentration
of 5 µg/L of each. Additional internal standards and surrogate analytes
are optional. Additional surrogate compounds should be similar in
physical and chemical characteristics to the analytes of concern.
Preparation of Laboratory Reagent Blank (LRB) -- Fill a 25 mL (or 5 mL) syringe
with reagent water and adjust to the mark (no air bubbles). Inject an appropriate
volume of the fortification solution containing the internal standard and
surrogates through the Luer Lok valve into the reagent water. Transfer the LRB
to the purging device. See Section 11.1.2.
524.2-12
8.0
7.7
Preparation of Laboratory Fortified Blank -- Prepare this exactly like a calibration
standard (Section 7.8). This is a calibration standard that is treated as a sample.
7.8
Preparation of Calibration Standards
7.8.1
The number of calibration solutions (CALs) needed depends on the
calibration range desired. A minimum of three CAL solutions is required
to calibrate a range of a factor of 20 in concentration. For a factor of 50,
use at least four standards, and for a factor of 100 at least five standards.
One calibration standard should contain each analyte of concern at a
concentration of 2-10 times the method detection limit (Tables 4, 5, and 7)
for that compound. The other CAL standards should contain each analyte
of concern at concentrations that define the range of the method. Every
CAL solution contains the internal standard and the surrogate compounds
at the same concentration (5 µg/L suggested for a 5 mL sample; 1 µg/L
for a 25 mL sample).
7.8.2
To prepare a calibration standard, add an appropriate volume of a
primary dilution standard containing all analytes of concern to an aliquot
of acidified (pH 2) reagent water in a volumetric flask. Also add an
appropriate volume of internal standard and surrogate compound solution
from Section 7.5.1. Use a microsyringe and rapidly inject the methanol
solutions into the expanded area of the filled volumetric flask. Remove
the needle as quickly as possible after injection. Mix by inverting the flask
three times only. Discard the contents contained in the neck of the flask.
Aqueous standards are not stable in a volumetric flask and should be
discarded after one hour unless transferred to a sample bottle and sealed
immediately.
SAMPLE COLLECTION, PRESERVATION, AND STORAGE
8.1
Sample Collection, Dechlorination, and Preservation
8.1.1
Collect all samples in duplicate. If samples, such as finished drinking
water or waste water, are suspected to contain residual chlorine, add
about 25 mg of ascorbic acid per 40 mL of sample to the sample bottle
before filling. If the residual chlorine is likely to be present >5 mg/L, a
determination of the amount of the chlorine may be necessary. Diethyl-pphenylenediamine (DPD) test kits are commercially available to determine
residual chlorine in the field. Add an additional 25 mg of ascorbic acid
per each 5 mg/L of residual chlorine. If compounds boiling below 25°C
are not to be determined, sodium thiosulfate may be used to reduce the
residual chlorine. Fill sample bottles to overflowing, but take care not to
flush out the rapidly dissolving ascorbic acid. No air bubbles should pass
through the sample as the bottle is filled, or be trapped in the sample
when the bottle is sealed. Adjust the pH of the duplicate samples to <2
by carefully adding two drops of 1:1 HCl for each 40 mL of sample. Seal
the sample bottles, Teflon face down, and shake vigorously for one
524.2-13
minute. Do not mix the ascorbic acid or sodium thiosulfate with the HCl
prior to sampling.
8.2
8.3
8.1.2
When sampling from a water tap, open the tap and allow the system to
flush until the water temperature has stabilized (usually about
10 minutes). Adjust the flow to about 500 mL/min and collect duplicate
samples from the flowing stream.
8.1.3
When sampling from an open body of water, such as surface water, waste
water, and possible leachate samples, partially fill a 1 qt wide-mouth
bottle or 1 L beaker with sample from a representative area. Fill a 60 mL
or a 120 mL sample vial with sample from the larger container, and adjust
the pH of the sample to about 2 by adding 1+1 HCl dropwise while
stirring. Check the pH with narrow range (1.4-2.8) pH paper. Record the
number of drops of acid necessary to adjust the pH to 2. To collect actual
samples, refill the large container with fresh sample and pour sample into
sample vials. Follow filling instructions in Section 8.1.1. Add the
appropriate number of drops of 1+1 HCl to each sample to adjust the pH
to about 2. If samples are suspected to contain residual chlorine, add
ascorbic acid or sodium thiosulfate according to Section 8.1.1.
8.1.4
The samples must be chilled to about 4°C when collected and maintained
at that temperature until analysis. Field samples that will not be received
at the laboratory on the day of collection must be packaged for shipment
with sufficient ice to ensure that they will arrive at the laboratory with a
substantial amount of ice remaining in the cooler.
8.1.5
If a sample foams vigorously when HCl is added, discard that sample.
Collect a set of duplicate samples but do not acidify them. These samples
must be flagged as "not acidified" and must be stored at 4°C or below.
These samples must be analyzed within 24 hours of collection time.
Sample Storage
8.2.1
Store samples at ≤4°C until analysis. The sample storage area must be
free of organic solvent vapors and direct or intense light.
8.2.2
Analyze all samples within 14 days of collection. Samples not analyzed
within this period must be discarded and replaced.
Field Reagent Blanks (FRB)
8.3.1
Duplicate FRBs 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 and sample preservatives, 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
524.2-14
stored, it is accompanied by appropriate blanks.
hermetically sealed until analysis.
8.3.2
9.0
FRBs must remain
Use the same procedures used for samples to add ascorbic acid and HCl
to blanks (Section 8.1.1). The same batch of ascorbic acid and HCl should
be used for the field reagent blanks in the field.
QUALITY CONTROL
9.1
Quality control (QC) requirements are the initial demonstration of laboratory
capability followed by regular analyses of laboratory reagent blanks, field reagent
blanks, and laboratory fortified blanks. Each laboratory must maintain records
to document the quality of the data generated. Additional quality control
practices are recommended.
9.2
Initial demonstration of low system background. Before any samples are
analyzed, it must be demonstrated that a laboratory reagent blank (LRB) is
reasonably free of contamination that would prevent the determination of any
analyte of concern. Sources of background contamination are glassware, purge
gas, sorbents, and equipment. Background contamination must be reduced to an
acceptable level before proceeding with the next section. In general, background
from method analytes should be below the method detection limit.
9.3
Initial demonstration of laboratory accuracy and precision. Analyze five to seven
replicates of a laboratory fortified blank containing each analyte of concern at a
concentration in the range of 0.2-5 µg/L (see appropriate regulations and
maximum contaminant levels for guidance on appropriate concentrations).
9.3.1
Prepare each replicate by adding an appropriate aliquot of a quality
control sample to reagent water. If a quality control sample containing the
method analytes is not available, a primary dilution standard made from
a source of reagents different than those used to prepare the calibration
standards may be used. Also add the appropriate amounts of internal
standard and surrogate compounds. Analyze each replicate according to
the procedures described in Section 11.0, and on a schedule that results in
the analyses of all replicates over a period of several days.
9.3.2
Calculate the measured concentration of each analyte in each replicate, the
mean concentration of each analyte in all replicates, and mean accuracy
(as mean percentage of true value) for each analyte, and the precision (as
relative standard deviation, RSD) of the measurements for each analyte.
Calculate the MDL of each analyte using the equa-tion described in
Section 13.23.
9.3.3
For each analyte, the mean accuracy, expressed as a percentage of the true
value, should be 80-120% and the RSD should be <20%. Some analytes,
particularly the early eluting gases and late eluting higher molecular
weight compounds, are measured with less accuracy and precision than
other analytes. The MDLs must be sufficient to detect analytes at the
524.2-15
required levels according to the SDWA Regulations. If these criteria are
not met for an analyte, take remedial action and repeat the measurements
for that analyte to demonstrate acceptable performance before samples are
analyzed.
9.3.4
Develop and maintain a system of control charts to plot the precision and
accuracy of analyte and surrogate measurements as a function of time.
Charting surrogate recoveries is an especially valuable activity because
surrogates are present in every sample and the analytical results will form
a significant record of data quality.
9.4
Monitor the integrated areas of the quantitation ions of the internal standards and
surrogates (Table 1) in all samples, continuing calibration checks, and blanks.
These should remain reasonably constant over time. An abrupt change may
indicate a matrix effect or an instrument problem. If a cryogenic interface is
utilized, it may indicate an inefficient transfer from the trap to the column. These
samples must be reanalyzed or a laboratory fortified duplicate sample analyzed
to test for matrix effect. A more gradual drift of more than 50% in any area is
indicative of a loss in sensitivity, and the problem must be found and corrected.
9.5
Laboratory Reagent Blanks (LRB) -- With each batch of samples processed as a
group within a work shift, analyze a LRB to determine the background system
contamination. A FRB (Section 9.7) may be used in place of a LRB.
9.6
With each batch of samples processed as a group within a work shift, analyze a
single laboratory fortified blank (LFB) containing each analyte of concern at a
concentration as determined in Section 9.3. If more than 20 samples are included
in a batch, analyze one LFB for every 20 samples. Use the procedures described
in Section 9.3.3 to evaluate the accuracy of the measurements, and to estimate
whether the MDLs can be obtained. If acceptable accuracy and MDLs cannot be
achieved, the problem must be located and corrected before further samples are
analyzed. Add these results to the ongoing control charts to document data
quality.
9.7
With each set of field samples a field reagent blank (FRB) should be analyzed.
The results of these analyses will help define contamination resulting from field
sampling and transportation activities. If the FRB shows unacceptable contamination, a LRB must be measured to define the source of the impurities.
9.8
At least quarterly, replicate LFBs should be analyzed to determine the precision
of the laboratory measurements. Add these results to the ongoing control charts
to document data quality.
9.9
At least quarterly, analyze a quality control sample (QCS) from an external
source. If measured analyte concentrations are not of acceptable accuracy, check
the entire analytical procedure to locate and correct the problem source.
9.10
Sample matrix effects have not been observed when this method is used with
distilled water, reagent water, drinking water, or ground water. Therefore,
524.2-16
analysis of a laboratory fortified sample matrix (LFM) is not required unless the
criteria in Section 9.4 are not met. If matrix effects are observed or suspected to
be causing low recoveries, analyze a laboratory fortified matrix sample for that
matrix. The sample results should be flagged and the LFM results should be
reported with them.
9.11
10.0
Numerous other quality control measures are incorporated into other parts of this
procedure, and serve to alert the analyst to potential problems.
CALIBRATION AND STANDARDIZATION
10.1
Demonstration and documentation of acceptable initial calibration is required
before any samples are analyzed and is required intermittently throughout sample
analysis as dictated by results of continuing calibration checks. After initial
calibration is successful, a continuing calibration check is required at the
beginning of each eight hour period during which analyses are performed.
Additional periodic calibration checks are good laboratory practice.
10.2
Initial Calibration
10.2.1 Calibrate the mass and abundance scales of the MS with calibration
compounds and procedures prescribed by the manufacturer with any
modifications necessary to meet the requirements in Section 10.2.2.
10.2.2 Introduce into the GC (either by purging a laboratory reagent blank or
making a syringe injection) 25 ng or less of BFB and acquire mass spectra
for m/z 35-260 at 70 eV (nominal). Use the purging procedure and/or GC
conditions given in Section 11.0. If the spectrum does not meet all criteria
in Table 3, the MS must be retuned and adjusted to meet all criteria before
proceeding with calibration. An average spectrum across the GC peak
may be used to evaluate the performance of the system.
10.2.3 Purge a medium CAL solution, (e.g., 10-20 µg/L) using the procedure
given in Section 11.0.
10.2.4 Performance criteria for the medium calibration. Examine the stored
GC/MS data with the data system software. Figures 3 and 4 shown
acceptable total ion chromatograms.
10.2.4.1
GC performance -- Good column performance will produce
symmetrical peaks with minimum tailing for most compounds. If peaks are unusually broad, or if peaks are
running together with little vallies between them, the
wrong column has been selected or remedial action is
probably necessary (Section 10.3.6).
10.2.4.2
MS sensitivity -- The GC/MS/DS peak identification
software should be able to recognize a GC peak in the
appropriate retention time window for each of the compounds in calibration solution, and make correct tentative
524.2-17
identifications. If fewer than 99% of the compounds are
recognized, system maintenance is required. See Section
10.3.6.
10.2.5 If all performance criteria are met, purge an aliquot of each of the other
CAL solutions using the same GC/MS conditions.
10.2.6 Calculate a response factor (RF) for each analyte and isomer pair for each
CAL solution using the internal standard fluorobenzene. Table 1 contains
suggested quantitation ions for all compounds. This calculation is
supported in acceptable GC/MS data system software (Section 6.3.5), and
many other software programs. RF is a unitless number, but units used
to express quantities of analyte and internal standard must be equivalent.
where: Ax = integrated abundance of the quantitation ion of the analyte.
Ais = integrated abundance of the quantitation ion of the internal
standard.
Qx = quantity of analyte purged in nanograms or concentration
units.
Qis = quantity of internal standard purged in ng or concentration
units.
10.2.6.1
For each analyte and surrogate, calculate the mean RF from
analyses of CAL solutions.
Calculate the standard
deviation (SD) and the relative standard deviation (RSD)
from each mean: RSD = 100 (SD/M). If the RSD of any
analyte or surrogate mean RF exceeds 20%, either analyze
additional aliquots of appropriate CAL solutions to obtain
an acceptable RSD of RFs over the entire concentration
range, or take action to improve GC/MS performance
Section 10.3.6). Surrogate compounds are present at the
same concentration on every sample, calibration standard,
and all types of blanks.
10.2.7 As an alternative to calculating mean response factors and applying the
RSD test, use the GC/MS data system software or other available software
to generate a linear or second order regression calibration curve.
10.3
Continuing Calibration Check -- Verify the MS tune and initial calibration at the
beginning of each eight-hour work shift during which analyses are performed
using the following procedure.
10.3.1 Introduce into the GC (either by purging a laboratory reagent blank or
making a syringe injection) 25 ng or less of BFB and acquire a mass
spectrum that includes data for m/z 35-260. If the spectrum does not
524.2-18
meet all criteria (Table 3), the MS must be retuned and adjusted to meet
all criteria before proceeding with the continuing calibration check.
10.3.2 Purge a medium concentration CAL solution and analyze with the same
conditions used during the initial calibration.
10.3.3 Demonstrate acceptable
Section 10.2.4.
performance
for
the
criteria
shown
in
10.3.4 Determine that the absolute areas of the quantitation ions of the internal
standard and surrogates have not decreased by more than 30% from the
areas measured in the most recent continuing calibration check, or by
more than 50% from the areas measured during initial calibration. If these
areas have decreased by more than these amounts, adjustments must be
made to restore system sensitivity. These adjustments may require
cleaning of the MS ion source, or other maintenance as indicated in
Section 10.3.6, and recalibration. Control charts are useful aids in
documenting system sensitivity changes.
10.3.5 Calculate the RF for each analyte of concern and surrogate compound
from the data measured in the continuing calibration check. The RF for
each analyte and surrogate must be within 30% of the mean value
measured in the initial calibration. Alternatively, if a linear or second
order regression is used, the concentration measured using the calibration
curve must be within 30% of the true value of the concentration in the
medium calibration solution. If these conditions do not exist, remedial
action must be taken which may require recalibration.
10.3.6 Some possible remedial actions. Major maintenance such as cleaning an
ion source, cleaning quadrupole rods, etc. require returning to the initial
calibration step.
10.3.6.1
Check and adjust GC and/or MS operating conditions;
check the MS resolution, and calibrate the mass scale.
10.3.6.2
Clean or replace the splitless injection liner; silanize a new
injection liner. This applies only if the injection liner is an
integral part of the system.
10.3.6.3
Flush the GC column with solvent according to
manufacturer's instructions.
10.3.6.4
Break off a short portion (about one meter) of the column
from the end near the injector; or replace GC column. This
action will cause a slight change in retention times.
Analyst may need to redefine retention windows.
10.3.6.5
Prepare fresh CAL solutions, and repeat the initial
calibration step.
524.2-19
10.4
10.3.6.6
Clean the MS ion source and rods (if a quadrupole).
10.3.6.7
Replace any components that allow analytes to come into
contact with hot metal surfaces.
10.3.6.8
Replace the MS electron multiplier, or any other faulty
components.
10.3.6.9
Replace the trap, especially when only a few compounds
fail the criteria in Section 10.3.5 while the majority are
determined successfully. Also check for gas leaks in the
purge and trap unit as well as the rest of the analytical
system.
Optional calibration for vinyl chloride using a certified gaseous mixture of vinyl
chloride in nitrogen can be accomplished by the following steps.
10.4.1 Fill the purging device with 25.0 mL (or 5 mL) of reagent water or
aqueous calibration standard.
10.4.2 Start to purge the aqueous mixture. Inject a known volume (between 100
and 2000 µL) of the calibration gas (at room temperature) directly into the
purging device with a gas tight syringe. Slowly inject the gaseous sample
through a septum seal at the top of the purging device at 2000 µL/min.
If the injection of the standard is made through the aqueous sample inlet
port, flush the dead volume with several mL of room air or carrier gas.
Inject the gaseous standard before 5 min of the 11-minute purge time have
elapsed.
10.4.3 Determine the aqueous equivalent concentration of vinyl chloride
standard, in µg/L, injected with the equation:
S = 0.102 (C) (V)
where: S = Aqueous equivalent concentration of vinyl chloride standard
in µg/L.
C = Concentration of gaseous standard in mg/L (v/v).
V = Volume of standard injected in mL.
11.0
PROCEDURE
11.1
Sample Introduction and Purging
11.1.1 This method is designed for a 25 mL sample volume, but a smaller (5 mL)
sample volume is recommended if the GC/MS system has adequate
sensitivity to achieve the required method detection limits. Adjust the
helium purge gas flow rate to 40 mL/min. Attach the trap inlet to the
purging device and open the syringe valve on the purging device.
524.2-20
11.1.2 Remove the plungers from two 25 mL (or 5 mL depending on sample
size) syringes and attach a closed syringe valve to each. Warm the sample
to room temperature, open the sample bottle, and carefully pour the
sample into one of the syringe barrels to just short of overflowing.
Replace the syringe plunger, invert the syringe, and compress the sample.
Open the syringe valve and vent any residual air while adjusting the
sample volume to 25.0 mL (or 5 mL). To all samples, blanks, and
calibration standards, add 5 µL (or an appropriate volume) of the
fortification solution containing the internal standard and the surrogates
to the sample through the syringe valve. Close the valve. Fill the second
syringe in an identical manner from the same sample bottle. Reserve this
second syringe for a reanalysis if necessary.
11.1.3 Attach the sample syringe valve to the syringe valve on the purging
device. Be sure that the trap is cooler than 25°C, then open the sample
syringe valve and inject the sample into the purging chamber. Close both
valves and initiate purging. Purge the sample for 11.0 minutes at ambient
temperature.
11.1.4 Standards and samples must be analyzed in exactly the same manner.
Room temperature changes in excess of 10°F may adversely affect the
accuracy and precision of the method.
11.2
Sample Desorption
11.2.1 Non-cryogenic interface -- After the 11-minute purge, place the purge and
trap system in the desorb mode and preheat the trap to 180°C without a
flow of desorption gas. Then simultaneously start the flow of desorption
gas at a flow rate suitable for the column being used (optimum desorb
flow rate is 15 mL/min) for about four minutes, begin the GC temperature
program, and start data acquisition.
11.2.2 Cryogenic interface -- After the 11-minute purge, place the purge and trap
system in the desorb mode, make sure the cryogenic interface is a -150°C
or lower, and rapidly heat the trap to 180°C while backflushing with an
inert gas at 4 mL/min for about five minutes. At the end of the five
minute desorption cycle, rapidly heat the cryogenic trap to 250°C, and
simultaneously begin the temperature program of the gas chromatograph,
and start data acquisition.
11.2.3 While the trapped components are being introduced into the gas
chromatograph (or cryogenic interface), empty the purging device using
the sample syringe and wash the chamber with two 25 mL flushes of
reagent water. After the purging device has been emptied, leave syringe
valve open to allow the purge gas to vent through the sample introduction
needle.
11.3
Gas Chromatography/Mass Spectrometry -- Acquire and store data over the
nominal mass range 35-260 with a total cycle time (including scan overhead time)
524.2-21
of two seconds or less. If water, methanol, or carbon dioxide cause a background
problem, start at 47 or 48 m/z. If ketones are to be determined, data must be
acquired starting at m/z 43. Cycle time must be adjusted to measure five or
more spectra during the elution of each GC peak. Suggested temperature
programs are provided below. Alternative temperature programs can be used.
11.3.1 Single ramp linear temperature program for wide-bore Columns 1 and 2
with a jet separator. Adjust the helium carrier gas flow rate to within the
capacity of the separator, or about 15 mL/min. The column temperature
is reduced 10°C and held for five minutes from the beginning of
desorption, then programmed to 160°C at 6°C/min, and held until all
components have eluted.
11.3.2 Multi-ramp temperature program for wide-bore Column 2 with the open
split interface. Adjust the helium carrier gas flow rate to about 4.6
mL/min. The column temperature is reduced to 10°C and held for six
minutes from the beginning of desorption, then heated to 70°C at 10°/min,
heated to 120°C at 5°/min, heated to 180°C at 8°/min, and held at 180°C
until all compounds have eluted.
11.3.3 Single ramp linear temperature program for narrow-bore Column 3 with
a cryogenic interface. Adjust the helium carrier gas flow rate to about
4 mL/min. The column temperature is reduced to 10°C and held for five
minutes from the beginning of vaporization from the cryogenic trap,
programmed at 6°/min for 10 minutes, then 15°/min for five minutes to
145°C, and held until all components have eluted.
11.3.4 Multi-ramp temperature program for wide-bore Column 4 with the open
split interface. Adjust the helium carrier gas flow rate to about
7.0 mL/min. The column temperature is -10°C and held for six minutes
from beginning of desorption, then heated to 100°C at 10°C/min, heated
to 200°C at 5°C/min and held at 200°C for eight minutes or until all
compounds of interest had eluted.
11.4
Trap Reconditioning -- After desorbing the sample for four minutes, recondition
the trap by returning the purge and trap system to the purge mode. Wait 15
seconds, then close the syringe valve on the purging device to begin gas flow
through the trap. Maintain the trap temperature at 180°C. Maintain the moisture
control module, if utilized, at 90°C to remove residual water. After approximately
seven minutes, turn off the trap heater and open the syringe valve to stop the gas
flow through the trap. When the trap is cool, the next sample can be analyzed.
11.5
Termination of Data Acquisition -- When all the sample components have eluted
from the GC, terminate MS data acquisition. Use appropriate data output
software to display full range mass spectra and appropriate plots of ion
abundance as a function of time. 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.
524.2-22
11.6
Identification of Analytes -- Identify a sample component by comparison of its
mass spectrum (after background subtraction) to a reference spectrum in the
user-created data base. The GC retention time of the sample component should
be within three standard deviations of the mean retention time of the compound
in the calibration mixture.
11.6.1 In general, all ions that are present above 10% relative abundance in the
mass spectrum of the standard should be present in the mass spectrum of
the sample component and should agree within absolute 20%. 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 10-50%. Some ions, particularly the molecular ion, are of special
importance, and should be evaluated even if they are below 10% relative
abundance.
11.6.2 Identification requires expert judgment when sample components are not
resolved chromatographically and produce mass spectra containing ions
contributed by more than one analyte. 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 plots of
characteristic ions for tentatively identified components. When analytes
coelute (i.e., only one GC peak is apparent), the identification criteria can
be met but each analyte spectrum will contain extraneous ions contributed
by the coeluting compound. Because purgeable organic compounds are
relatively small molecules and produce comparatively simple mass
spectra, this is not a significant problem for most method analytes.
11.6.3 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
peaks is less than 25% of the average height of the two peaks. Otherwise,
structural isomers are identified as isomeric pairs. Two of the three
isomeric xylenes and two of the three dichlorobenzenes are examples of
structural isomers that may not be resolved on the capillary columns. If
unresolved, these groups of isomers must be reported as isomeric pairs.
11.6.4 Methylene chloride, acetone, carbon disulfide, and other background
components appear in variable quantities in laboratory and field reagent
blanks, and generally cannot be accurately measured. Subtraction of the
concentration in the blank from the concentration in the sample is not
acceptable because the concentration of the background in the blank is
highly variable.
12.0
DATA ANALYSIS AND CALCULATIONS
12.1
Complete chromatographic resolution is not necessary for accurate and precise
measurements of analyte concentrations if unique ions with adequate intensities
are available for quantitation.
524.2-23
12.1.1 Calculate analyte and surrogate concentrations.
where: Cx = concentration of analyte or surrogate in µg/L in the water
sample.
Ax = integrated abundance of the quantitation ion of the analyte
in the sample.
Ais = integrated abundance of the quantitation ion of the internal
standard in the sample.
Qis = total quantity (in micrograms) of internal standard added to
the water sample.
V = original water sample volume in mL.
RF = mean response factor of analyte from the initial calibration.
12.1.2 Alternatively, use the GC/MS system software or other available proven
software to compute the concentrations of the analytes and surrogates
from the linear or second order regression curves.
12.1.3 Calculations should utilize all available digits of precision, but final
reported concentrations should be rounded to an appropriate number of
significant figures (one digit of uncertainty). Experience indicates that
three significant figures may be used for concentrations above 99 µg/L,
two significant figures for concentrations between 1-99 µg/L, and one
significant figure for lower concentrations.
12.1.4 Calculate the total trihalomethane concentration by summing the four
individual trihalomethane concentrations.
13.0
METHOD PERFORMANCE
13.1
Single laboratory accuracy and precision data were obtained for the method
analytes using laboratory fortified blanks with analytes at concentrations between
1 and 5 µg/L. Results were obtained using the four columns specified (Section
6.3.2.1) and the open split or jet separator (Section 6.3.3.1), or the cryogenic
interface (Section 6.3.3.2). These data are shown in Tables 4-8.
13.2
With these data, method detection limits were calculated using the formula3:
MDL = S t(n-1,1-alpha = 0.99)
where: t(n-1,1-alpha = 0.99) = Student's t value for the 99% confidence level with n-1
degrees of freedom.
n = Number of replicates.
S = The standard deviation of the replicate analyses.
14.0
POLLUTION PREVENTION
524.2-24
14.1
15.0
WASTE MANAGEMENT
15.1
16.0
No solvents are utilized in this method except the extremely small volumes of
methanol needed to make calibration standards. The only other chemicals used
in this method are the neat materials in preparing standards and sample
preservatives. All are used in extremely small amounts and pose no threat to the
environment.
There are no waste management issues involved with this method. Due to the
nature of this method, the discarded samples are chemically less contaminated
than when they were collected.
REFERENCES
1.
Alford-Stevens, A., Eichelberger, J.W., and Budde, W.L. "Purgeable Organic
Compounds in Water by Gas Chromatography/Mass Spectrometry, Method 524."
Environmental Monitoring and Support Laboratory, U.S. Environmental
Protection Agency, Cincinnati, Ohio, February 1983.
2.
Madding, C. "Volatile Organic Compounds in Water by Purge and Trap
Capillary Column GC/MS," Proceedings of the Water Quality Technology
Conference, American Water Works Association, Denver, CO, December 1984.
3.
Glaser, J.A., Foerst, D.L., McKee, G.D., Quave, S.A., and Budde, W.L. "Trace
Analyses for Wastewaters," Environ. Sci. Technol., 15, 1426, 1981.
4.
"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, August 1977.
5.
"OSHA Safety and Health Standards, General Industry," (29 CFR 1910),
Occupational Safety and Health Administration, OSHA 2206, (Revised, January
1976).
6.
"Safety in Academic Chemistry Laboratories," American Chemical Society
Publication, Committee on Chemical Safety, 3rd Edition, 1979.
7.
Arrendale, R.F., Severson, R.F., and Chortyk, O.T. "Open Split Interface for
Capillary Gas Chromatography/Mass Spectrometry," Anal. Chem. 1984, 56, 1533.
8.
Flesch, J.J. and Fair, P.S. "The Analysis of Cyanogen Chloride in Drinking Water,"
Proceedings of Water Quality Technology Conference, American Water Works
Association, St. Louis, MO., November 14-16, 1988.
524.2-25
17.0
TABLES, DIAGRAMS, FLOWCHARTS, AND VALIDATION DATA
TABLE 1. MOLECULAR WEIGHTS AND QUANTITATION IONS FOR
METHOD ANALYTES
Compound
MWa
Primary
Quantitation
Ion
Secondary
Quantitation
Ions
Internal standard
Fluorobenzene
96
96
77
174
150
95
152
174, 176
115, 150
58
53
76
78
156
128
162
250
94
72
134
134
134
76
152
75
112
92
64
118
50
126
126
206
234
186
172
146
146
43
52
76
78
156
128
83
173
94
43
91
105
119
76
117
48
112
56
64
83
50
91
91
129
75
107
93
146
146
58
53
49
77
77, 158
49, 130
85, 127
175, 252
96
57, 72
134
134
91
–
119
75
77, 114
49
66
85
52
126
126
127
155, 157
109, 188
95, 174
111, 148
111, 148
Surrogates
4-Bromofluorobenzene
1,2-Dichlorobenzene-d4
Target Analytes
Acetone
Acrylonitrile
Allyl chloride
Benzene
Bromobenzene
Bromochloromethane
Bromodichloromethane
Bromoform
Bromomethane
2-Butanone
n-Butylbenzene
sec-Butylbenzene
tert-Butylbenzene
Carbon disulfide
Carbon tetrachloride
Chloroacetonitrile
Chlorobenzene
1-Chlorobutane
Chloroethane
Chloroform
Chloromethane
2-Chlorotoluene
4-Chlorotoluene
Dibromochloromethane
1,2-Dibromo-3-Chloropropane
1,2-Dibromoethane
Dibromomethane
1,2-Dichlorobenzene
1,3-Dichlorobenzene
524.2-26
TABLE 1. MOLECULAR WEIGHTS AND QUANTITATION IONS FOR
METHOD ANALYTES
Compound
1,4-Dichlorobenzene
trans-1,4-Dichloro-2-butene
Dichlorodifluoromethane
1,1-Dichloroethane
1,2-Dichloroethane
1,1-Dichloroethene
cis-1,2-Dichloroethene
trans-1,2-Dichloroethene
1,2-Dichloropropane
1,3-Dichloropropane
2,2-Dichloropropane
1,1-Dichloropropene
1,1-Dichloropropanone
cis-1,3-dichloropropene
trans-1,3-dichloropropene
Diethyl ether
Ethylbenzene
Ethyl methacrylate
Hexachlorobutadiene
Hexachloroethane
2-Hexanone
Isopropylbenzene
4-Isopropyltoluene
Methacrylonitrile
Methyl acrylate
Methylene chloride
Methyl iodide
Methylmethacrylate
4-Methyl-2-pentanone
Methyl-t-butyl ether
Naphthalene
Nitrobenzene
2-Nitropropane
Pentachloroethane
Propionitrile
n-Propylbenzene
Styrene
1,1,1,2-Tetrachloroethane
1,1,2,2-Tetrachloroethane
Tetrachloroethene
Tetrahydrofuran
Toluene
MWa
Primary
Quantitation
Ion
Secondary
Quantitation
Ions
146
124
120
98
98
96
96
96
112
112
112
110
126
110
110
74
106
114
258
234
100
120
134
67
86
84
142
100
100
88
128
123
89
200
55
120
104
166
166
164
72
92
146
53
85
63
62
96
96
96
63
76
77
75
43
75
75
59
91
69
225
117
43
105
119
67
55
84
142
69
43
73
128
51
46
117
54
91
104
131
83
166
71
92
111, 148
88, 75
87
65, 83
98
61, 63
61, 98
61, 98
112
78
97
110, 77
83
110
110
45, 73
106
99
260
119, 201
58
120
134, 91
52
85
86, 49
127
99
58, 85
57
–
77
–
119, 167
–
120
78
133, 119
131, 85
168, 129
72, 42
91
524.2-27
TABLE 1. MOLECULAR WEIGHTS AND QUANTITATION IONS FOR
METHOD ANALYTES
Compound
1,2,3-Trichlorobenzene
1,2,4-Trichlorobenzene
1,1,1-Trichloroethane
1,1,2-Trichloroethane
Trichloroethene
Trichlorofluoromethane
1,2,3-Trichloropropane
1,2,4-Trimethylbenzene
1,3,5-Trimethylbenzene
Vinyl Chloride
o-Xylene
m-Xylene
p-Xylene
MWa
Primary
Quantitation
Ion
Secondary
Quantitation
Ions
180
180
132
132
130
136
146
120
120
62
106
106
106
180
180
97
83
95
101
75
105
105
62
106
106
106
182
182
99, 61
97, 85
130, l32
103
77
120
120
64
91
91
91
a
Monoisotopic molecular weight calculated from the atomic masses of the isotopes with the
smallest masses.
524.2-28
TABLE 2. CHROMATOGRAPHIC RETENTION TIMES FOR METHOD ANALYTES
ON THREE COLUMNS WITH FOUR SETS OF CONDITIONSa
Retention Time (min:sec)
Compound
Column 1b
Column 2b Column 2c Column 3d Column 4e
Internal standard
Fluorobenzene
8:49
6:27
14:06
18:38
22:16
15:43
19:08
23:38
27:25
8:03
22:00
Surrogates
4-Bromofluorobenzene
1,2-Dichlorobenzene-d4
31:21
35:51
Target Analytes
Acetone
Acrylonitrile
Allyl chloride
Benzene
Bromobenzene
Bromochloromethane
Bromodichloromethane
Bromoform
Bromomethane
2-Butanone
n-Butylbenzene
sec-Butylbenzene
tert-Butylbenzene
Carbon Disulfide
Carbon Tetrachloride
Chloroacetonitrile
Chlorobenzene
1-Chlorobutane
Chloroethane
Chloroform
Chloromethane
2-Chlorotoluene
4-Chlorotoluene
Cyanogen chloride8
Dibromochloromethane
1,2-Dibromo-3-Chloropropan
e
1,2-Dibromoethane
Dibromomethane
1,2-Dichlorobenzene
1,3-Dichlorobenzene
1,4-Dichlorobenzene
8:14
18:57
6:44
10:35
17:56
2:01
5:40
15:52
4:23
8:29
14:53
0:58
13:30
24:00
12:22
15:48
22:46
4:48
7:25
16:25
5:38
9:20
15:42
1:17
22:13
20:47
20:17
19:29
18:05
17:34
27:32
26:08
25:36
17:57
17:28
17:19
7:37
5:16
13:10
7:25
15:46
13:01
20:40
14:20
2:05
6:24
1:38
19:20
19:30
1:01
4:48
0:44
16:25
16:43
12:36
3:24
24:32
24:46
5:33
0:58
16:44
16:49
14:23
24:32
11:51
21:05
19:12
12:48
18:02
16:14
17:49
16:58
21:32
31:52
20:20
23:36
30:32
12:26
19:41
35:41
34:04
33:26
16:30
21:11
23:51
28:26
21:00
1:27
20:27
9:11
32:21
32:38
1:03
26:57
38:20
14:44
10:39
22:31
21:13
21:33
11:50
7:56
19:10
18:08
18:23
19:24
15:26
27:26
26:22
26:36
13:36
9:05
17:47
17:28
17:38
27:19
23:22
35:55
34:31
34:45
524.2-29
TABLE 2. CHROMATOGRAPHIC RETENTION TIMES FOR METHOD ANALYTES
ON THREE COLUMNS WITH FOUR SETS OF CONDITIONSa
Retention Time (min:sec)
Compound
t-1,4-Dichloro-2-butene
Dichlorodifluoromethane
1,1-Dichloroethane
1,2-Dichloroethane
1,1-Dichloroethene
cis-1,2-Dichloroethene
trans-1,2-Dichloroethene
1,2-Dichloropropane
1,3-Dichloropropane
2,2-Dichloropropane
1,1-Dichloropropanone
1,1-Dichloropropene
cis-1,3-dichloropropene
trans-1,3-dichloropropene
Diethyl ether
Ethylbenzene
Ethyl Methacrylate
Hexachlorobutadiene
Hexachloroethane
Hexanone
Isopropylbenzene
4-Isopropyltoluene
Methacrylonitrile
Methylacrylate
Methylene Chloride
Methyl Iodide
Methylmethacrylate
4-Methyl-2-pentanone
Methyl-t-butyl ether
Naphthalene
Nitrobenzene
2-Nitropropane
Pentachloroethane
Propionitrile
n-Propylbenzene
Styrene
1,1,1,2-Tetrachloroethane
1,1,2,2-Tetrachloroethane
Tetrachloroethene
Tetrahydrofuran
Toluene
1,2,3-Trichlorobenzene
1,2,4-Trichlorobenzene
Column 1b
Column 2b Column 2c Column 3d Column 4e
1:33
4:51
8:24
2:53
6:11
3:59
10:05
14:02
6:01
0:42
2:56
5:50
1:34
3:54
2:22
7:40
11:19
3:48
3:08
10:48
13:38
7:50
11:56
9:54
15:12
18:42
11:52
0:53
4:02
7:00
2:20
5:04
3:32
8:56
12:29
5:19
7:49
11.58
13.46
5:17
13:06
16:42
17:54
7:10
15:59
13:23
21:00
14:44
26:59
23:41
32:04
19:14
18:04
21:12
15:28
18:31
23:18
26:30
16:25
17:38
3:36
2:04
9:16
2:40
27:10
23:31
32:12
19:04
19:04
17:19
15:56
18:43
13:44
16:25
14:36
13:20
16:21
11:09
24:20
22:24
20:52
24:04
18:36
16:49
15:47
14:44
15:47
13:12
12:26
27:47
26:33
10:00
24:11
23:05
17:24
32:58
31:30
11:31
19:14
18:50
524.2-30
31:44
7:16
18:46
21:31
16:01
19:53
17:54
23:08
26:23
19:54
24:52
21:08
24:24
25:33
15:31
28:37
25:35
42:03
36:45
26:23
30:52
34:27
20:15
20:02
17:18
16:21
23:08
24:38
17:56
42:29
39:02
23:58
33:33
19:58
32:00
29:57
28:35
31:35
26:27
20:26
25:13
43:31
41:26
TABLE 2. CHROMATOGRAPHIC RETENTION TIMES FOR METHOD ANALYTES
ON THREE COLUMNS WITH FOUR SETS OF CONDITIONSa
Retention Time (min:sec)
Compound
1,1,1-Trichloroethane
1,1,2-Trichloroethane
Trichloroethene
Trichlorofluoromethane
1,2,3-Trichloropropane
1,2,4-Trimethylbenzene
1,3,5-Trimethylbenzene
Vinyl chloride
o-Xylene
m-Xylene
p-Xylene
Column 1b
7:16
13:25
9:35
2:16
19:01
20:20
19:28
1:43
17:07
16:10
16:07
Column 2b Column 2c Column 3d Column 4e
4:50
12:50
6:46
20:51
11:03
18:18
11:59
25:59
7:16
14:48
9:01
22:42
1:11
6:12
1:46
14:18
16:14
24:08
16:16
31:47
17:42
31:30
17:19
33:33
16:54
24:50
16:59
32:26
0:47
3:56
1:02
10:22
14:31
22:16
15:47
29:56
13:41
21:22
15:18
28:53
13:41
21:18
15:18
28:53
a
Columns 1-4 are those given in Section 6.3.2.1; retention times were measured from the
beginning of thermal desorption from the trap (Columns 1-2, and 4) or from the beginning of
thermal release from the cryogenic interface (Column 3).
b
GC conditions given in Section 11.3.1.
c
GC conditions given in Section 11.3.2.
d
GC conditions given in Section 11.3.3.
e
GC conditions given in Section 11.3.4.
TABLE 3. ION ABUNDANCE CRITERIA FOR 4-BROMOFLUOROBENZENE (BFB)
Mass
(M/z)
50
75
95
96
173
174
175
176
177
Relative Abundance Criteria
15-40% of mass 95
30-80% of mass 95
Base Peak, 100% Relative Abundance
5-9% of mass 95
<2% of mass 174
>50% of mass 95
5-9% of mass 174
>95% but <101% of mass 174
5-9% of mass 176
524.2-31
TABLE 4. ACCURACY AND PRECISION DATA FROM 16-31 DETERMINATIONS OF
THE METHOD ANALYTES IN REAGENT WATER USING WIDE-BORE
CAPILLARY COLUMN 1a
Compound
Benzene
Bromobenzene
Bromochloromethane
Bromodichloromethane
Bromoform
Bromomethane
n-Butylbenzene
sec-Butylbenzene
tert-Butylbenzene
Carbon tetrachloride
Chlorobenzene
Chloroethane
Chloroform
Chloromethane
2-Chlorotoluene
4-Chlorotoluene
Dibromochloromethane
1,2-Dibromo-3-chloropropane
1,2-Dibromoethane
Dibromomethane
1,2-Dichlorobenzene
1,3-Dichlorobenzene
1,4-Dichlorobenzene
Dichlorodifluoromethane
1,1-Dichloroethane
1,2-Dichloroethane
1,1-Dichloroethene
cis-1,2 Dichloroethene
trans-1,2-Dichloroethene
1,2-Dichloropropane
1,3-Dichloropropane
2,2-Dichloropropane
1,1-Dichloropropene
cis-1,2-Dichloropropene
trans-1,2-Dichloropropene
Ethylbenzene
Hexachlorobutadiene
Isopropylbenzene
4-Isopropyltoluene
Methylene chloride
True
Conc.
Range
(µg/L)
Mean
Accuracy
(% of True
Value)
Rel.
Std.
Dev.
(%)
Method
Det.
Limitb
(µg/L)
0.1-10
0.1-10
0.5-10
0.1-10
0.5-10
0.5-10
0.5-10
0.5-10
0.5-10
0.5-10
0.1-10
0.5-10
0.5-10
0.5-10
0.1-10
0.1-10
0.1-10
0.5-10
0.5-10
0.5-10
0.1-10
0.5-10
0.2-20
0.5-10
0.5-10
0.1-10
0.1-10
0.5-10
0.1-10
0.1-10
0.1-10
0.5-10
0.5-10
97
100
90
95
101
95
100
100
102
84
98
89
90
93
90
99
92
83
102
100
93
99
103
90
96
95
94
101
93
97
96
86
98
5.7
5.5
6.4
6.1
6.3
8.2
7.6
7.6
7.3
8.8
5.9
9.0
6.1
8.9
6.2
8.3
7.0
19.9
3.9
5.6
6.2
6.9
6.4
7.7
5.3
5.4
6.7
6.7
5.6
6.1
6.0
16.9
8.9
0.04
0.03
0.04
0.08
0.12
0.11
0.11
0.13
0.14
0.21
0.04
0.10
0.03
0.13
0.04
0.06
0.05
0.26
0.06
0.24
0.03
0.12
0.03
0.10
0.04
0.06
0.12
0.12
0.06
0.04
0.04
0.35
0.10
0.1-10
0.5-10
0.5-10
0.1-10
0.1-10
99
100
101
99
95
8.6
6.8
7.6
6.7
5.3
0.06
0.11
0.15
0.12
0.03
524.2-32
TABLE 4. ACCURACY AND PRECISION DATA FROM 16-31 DETERMINATIONS OF
THE METHOD ANALYTES IN REAGENT WATER USING WIDE-BORE
CAPILLARY COLUMN 1a
Compound
Naphthalene
n-Propylbenzene
Styrene
1,1,1,2-Tetrachloroethane
1,1,2,2-Tetrachloroethane
Tetrachloroethene
Toluene
1,2,3-Trichlorobenzene
1,2,4-Trichlorobenzene
1,1,1-Trichloroethane
1,1,2-Trichloroethane
Trichloroethene
Trichlorofluoromethane
1,2,3-Trichloropropane
1,2,4-Trimethylbenzene
1,3,5-Trimethylbenzene
Vinyl chloride
o-Xylene
m-Xylene
p-Xylene
True
Conc.
Range
(µg/L)
0.1-100
0.1-10
0.1-100
0.5-10
0.1-10
0.5-10
0.5-10
0.5-10
0.5-10
0.5-10
0.5-10
0.5-10
0.5-10
0.5-10
0.5-10
0.5-10
0.5-10
0.1-31
0.1-10
0.5-10
a
Mean
Accuracy
(% of True
Value)
104
100
102
90
91
89
102
109
108
98
104
90
89
108
99
92
98
103
97
104
Rel.
Std.
Dev.
(%)
8.2
5.8
7.2
6.8
6.3
6.8
8.0
8.6
8.3
8.1
7.3
7.3
8.1
14.4
8.1
7.4
6.7
7.2
6.5
7.7
Method
Det.
Limitb
(µg/L)
0.04
0.04
0.04
0.05
0.04
0.14
0.11
0.03
0.04
0.08
0.10
0.19
0.08
0.32
0.13
0.05
0.17
0.11
0.05
0.13
Data obtained by using Column 1 with a jet separator interface and a quadrupole mass
spectrometer (Section 11.3.1) with analytes divided among three solutions.
b
Replicate samples at the lowest concentration listed in Column 2 of this table were
analyzed. These results were used to calculate MDLs.
524.2-33
TABLE 5. ACCURACY AND PRECISION DATA FROM SEVEN DETERMINATIONS
OF METHOD ANALYTES IN REAGENT WATER USING THE CRYOGENIC
TRAPPING OPTION AND A NARROW-BORE CAPILLARY COLUMN 3a
True
Conc.
(µg/L)
Compound
Benzene
Bromobenzene
Bromochloromethane
Bromodichloromethane
Bromoform
Bromomethane
n-Butylbenzene
sec-Butylbenzene
tert-Butylbenzene
Carbon tetrachloride
Chlorobenzene
Chloroethane
Chloroform
Chloromethane
2-Chlorotoluene
4-Chlorotoluene
Cyanogen chlorideb
Dibromochloromethane
1,2-Dibromo-3-chloropropane
1,2-Dibromoethane
Dibromomethane
1,2-Dichlorobenzene
1,3-Dichlorobenzene
1,4-Dichlorobenzene
Dichlorodifluoromethane
1,1-Dichloroethane
1,2-Dichloroethane
1,1-Dichloroethene
cis-1,2 Dichloroethene
trans-1,2-Dichloroethene
1,2-Dichloropropane
1,3-Dichloropropane
2,2-Dichloropropane
1,1-Dichloropropene
cis-1,3-Dichloropropene
trans-1,3-Dichloropropene
Ethylbenzene
Hexachlorobutadiene
Isopropylbenzene
4-Isopropyltoluene
Mean
Accuracy
(% of True
Value)
0.1
0.5
0.5
0.1
0.1
0.1
0.5
0.5
0.5
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Rel.
Std.
Dev.
(%)
Method
Dect.
Limit
(µg/L)
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
99
97
97
100
99
99
94
90
90
92
91
100
95
99
99
96
92
99
92
97
93
97
99
93
99
98
100
95
100
98
96
99
99
98
6.2
7.4
5.8
4.6
5.4
7.1
6.0
7.1
2.5
6.8
5.8
5.8
3.2
4.7
4.6
7.0
10.6
5.6
10.0
5.6
6.9
3.5
6.0
5.7
8.8
6.2
6.3
9.0
3.7
7.2
6.0
5.8
4.9
7.4
0.03
0.11
0.07
0.03
0.20
0.06
0.03
0.12
0.33
0.08
0.03
0.02
0.02
0.05
0.05
0.05
0.30
0.07
0.05
0.02
0.03
0.05
0.05
0.04
0.11
0.03
0.02
0.05
0.06
0.03
0.02
0.04
0.05
0.02
0.1
0.1
0.5
0.5
99
100
98
87
5.2
6.7
6.4
13.0
0.03
0.04
0.10
0.26
524.2-34
TABLE 5. ACCURACY AND PRECISION DATA FROM SEVEN DETERMINATIONS
OF METHOD ANALYTES IN REAGENT WATER USING THE CRYOGENIC
TRAPPING OPTION AND A NARROW-BORE CAPILLARY COLUMN 3a
True
Conc.
(µg/L)
Compound
Methylene chloride
Naphthalene
n-Propylbenzene
Styrene
1,1,1,2-Tetrachloroethane
1,1,2,2-Tetrachloroethane
Tetrachloroethene
Toluene
1,2,3-Trichlorobenzene
1,2,4-Trichlorobenzene
1,1,1-Trichloroethane
1,1,2-Trichloroethane
Trichloroethene
Trichlorofluoromethane
1,2,3-Trichloropropane
1,2,4-Trimethylbenzene
1,3,5-Trimethylbenzene
Vinyl chloride
o-Xylene
m-Xylene
p-Xylene
Mean
Accuracy
(% of True
Value)
0.5
0.1
0.1
0.1
0.1
0.5
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
97
98
99
96
100
100
96
100
98
91
100
98
96
97
96
96
99
96
94
94
97
a
Rel.
Std.
Dev.
(%)
13.0
7.2
6.6
19.0
4.7
12.0
5.0
5.9
8.9
16.0
4.0
4.9
2.0
4.6
6.5
6.5
4.2
0.2
7.5
4.6
6.1
Method
Dect.
Limit
(µg/L)
0.09
0.04
0.06
0.06
0.04
0.20
0.05
0.08
0.04
0.20
0.04
0.03
0.02
0.07
0.03
0.04
0.02
0.04
0.06
0.03
0.06
Data obtained by using Column 3 with a cryogenic interface and a quadrupole mass
spectrometer (Section 11.3.3).
b
Reference 8.
524.2-35
TABLE 6. ACCURACY AND PRECISION DATA FROM SEVEN DETERMINATIONS
OF THE METHOD ANALYTES IN REAGENT WATER USING WIDE-BORE
CAPILLARY COLUMN 2a
Compound
Mean Accuracy
(% of True
Value, 2 µg/L
No.b
Conc.)
RSD
(%)
Mean Accuracy
(% of True
Value, 2 µg/L
Conc.)
RSD
(%)
Internal Standard
Fluorobenzene
1
–
–
–
–
2
3
98
97
1.8
3.2
96
95
1.3
1.7
37
38
4
5
6
7
39
40
41
8
42
97
102
99
96
89
55
89
102
101
84
104
4.4
3.0
5.2
1.8
2.4
27
4.8
3.5
4.5
3.2
3.1
113
101
102
100
90
52
87
100
100
92
103
1.8
1.9
2.9
1.8
2.2
6.7
2.3
2.8
2.9
2.6
1.6
9
10
43
44
11
97
110
91
89
95
2.0
5.0
2.4
2.0
2.7
95
2.1
13
45
46
47
14
15
16
17
18
19
99
93
100
98
38
97
102
90
100
92
2.1
2.7
4.0
4.1
25
2.3
3.8
2.2
3.4
2.1
Surrogates
4-Bromofluorobenzene
1,2-Dichlorobenzene-d4
Target Analytes
Benzene
Bromobenzene
Bromochloromethane
Bromodichloromethane
Bromoform
Bromomethane
n-Butylbenzene
sec-Butylbenzene
tert-Butylbenzene
Carbon tetrachloride
Chlorobenzene
Chloroethanec
Chloroform
Chloromethane
2-Chlorotoluene
4-Chlorotoluene
Dibromochloromethane
1,2-Dibromo-3-chloropropanec
1,2-Dibromoethanec
Dibromomethane
1,2-Dichlorobenzene
1,3-Dichlorobenzene
1,4-Dichlorobenzene
Dichlorodifluoromethane
1,1-Dichloroethane
1,2-Dichloroethane
1,1-Dichloroethene
cis-1,2-Dichloroethene
trans-1,2-Dichloroethene
524.2-36
d
108
108
100
3.1
4.4
3.0
95
94
87
94
2.2
5.1
2.3
2.8
d
85
100
87
89
85
3.6
2.1
3.8
2.9
2.3
TABLE 6. ACCURACY AND PRECISION DATA FROM SEVEN DETERMINATIONS
OF THE METHOD ANALYTES IN REAGENT WATER USING WIDE-BORE
CAPILLARY COLUMN 2a
Compound
1,2-Dichloropropane
1,3-Dichloropropane
2,2-Dichloropropanec
1,1-Dichloropropenec
cis-1,3-Dichloropropenec
trans-1,3-Dichloropropene
Ethylbenzene
Hexachlorobutadiene
Isopropylbenzene
4-Isopropyltoluene
Methylene chloride
Naphthalene
n-Propylbenzene
Styrene
1,1,1,2-Tetrachloroethane
1,1,2,2-Tetrachloroethane
Tetrachloroethene
Toluene
1,2,3-Trichlorobenzene
1,2,4-Trichlorobenzene
1,1,1-Trichloroethane
1,1,2-Trichloroethane
Trichloroethene
Trichlorofluoromethane
1,2,3-Trichloropropane
1,2,4-Trimethylbenzene
1,3,5-Trimethylbenzene
Vinyl chloride
o-Xylene
m-Xylene
p-Xylene
Mean Accuracy
(% of True
Value, 2 µg/L
No.b
Conc.)
RSD
(%)
20
21
102
92
2.2
3.7
103
93
2.9
3.2
25
48
26
49
50
27
51
52
53
28
29
30
54
55
56
31
32
33
34
35
57
58
36
59
60
61
96
96
91
103
95
1.7
9.1
5.3
3.2
3.6
99
100
88
101
95
2.1
4.0
2.4
2.1
3.1
e
93
102
95
99
101
97
105
90
92
94
107
99
81
97
93
88
104
97
a
RSD
(%)
e
7.6
4.9
4.4
2.7
4.6
4.5
2.8
5.7
5.2
3.9
3.4
2.9
4.6
3.9
3.1
2.4
3.5
1.8
f
98
Mean Accuracy
(% of True
Value, 2 µg/L
Conc.)
78
97
104
95
84
92
126
78
83
94
109
106
48
91
106
97
115
98
8.3
2.1
3.1
3.8
3.6
3.3
1.7
2.9
5.9
2.5
2.8
2.5
13
2.8
2.2
3.2
14
1.7
f
2.3
103
1.4
Data obtained using column 2 with the open split interface and an ion trap mass
spectrometer (Section 11.3.2) with all method analytes in the same reagent water solution.
b
Designation in Figures 1 and 2.
c
Not measured; authentic standards were not available.
d
Not found at 0.2 µg/L.
e
Not measured; methylene chloride was in the laboratory reagent blank.
f
m-Xylene coelutes with and cannot be distinguished from its isomer p-Xylene, No 61.
524.2-37
TABLE 7. ACCURACY AND PRECISION DATA FROM SEVEN DETERMINATIONS
OF METHOD ANALYTES IN REAGENT WATER USING WIDE-BORE
CAPILLARY COLUMN 4
Compound
Acetone
Acrylonitrile
Allyl chloride
2-Butanone
Carbon disulfide
Chloroacetonitrile
1-Chlorobutane
t-1,2-Dichloro-2-butene
1,1-Dichloropropanone
Diethyl ether
Ethyl methacrylate
Hexachloroethane
2-Hexanone
Methacrylonitrile
Methylacrylate
Methyl iodide
Methylmethacrylate
4-Methyl-2-pentanone
Methyl-tert-butylether
Nitrobenzene
2-Nitropropane
Pentachloroethane
Propionitrile
Tetrahydrofuran
True
Conc.
(µg/L)
Mean
Conc.
Detected
(µg/L)
Rel.
Std.
Dev.
(%)
Method
Dect.
Limit
(µg/L)
1.0
1.0
1.0
2.0
0.20
1.0
1.0
1.0
5.0
1.0
0.20
0.20
1.0
1.0
1.0
0.20
1.0
0.40
0.40
2.0
1.0
0.20
1.0
5.0
1.6
0.81
0.90
2.7
0.19
0.83
0.87
1.3
4.2
0.92
0.23
0.18
1.1
0.92
1.2
0.19
1.0
0.56
0.52
2.1
0.83
0.23
0.87
3.9
5.7
8.7
4.7
5.6
15
4.7
6.6
8.7
7.7
9.5
3.9
10
12
4.2
12
3.1
13
9.7
5.6
18
6.2
20
5.3
13
0.28
0.22
0.13
0.48
0.093
0.12
0.18
0.36
1.0
0.28
0.028
0.057
0.39
0.12
0.45
0.019
0.43
0.17
0.090
1.2
0.16
0.14
0.14
1.6
524.2-38
TABLE 8. ACCURACY AND PRECISION FROM FOUR DETERMINATIONS OF
METHOD ANALYTES IN THREE WATER MATRICES FORTIFIED AT 20 µg/L
Reagent Water
Compound
Acetone
Acrylonitrile
Allyl chloride
2-Butanone
Carbon disulfide
Chloroacetonitrile
1-Chlorobutane
t-1,2-Dichloro-2-butene
1,1-Dichloropropanone
Diethyl ether
Ethyl methacrylate
Hexachloroethane
2-Hexanone
Methacrylonitrile
Methylacrylate
Methyl iodide
Methylmethacrylate
4-Methyl-2-pentanone
Methyl-tert-butylether
Nitrobenzene
2-Nitropropane
Pentachloroethane
Propionitrile
Tetrahydrofuran
Raw Water
Tap Water
(% of
(% of
(% of
Mean Dev. True Mean Dev. True Mean Dev. True
(µg/L) (%) Value) (µg/L) (%) Value) (µg/L) (%) Value)
19
20
20
17
19
20
18
19
20
18
20
20
19
20
20
20
20
19
19
20
20
19
20
20
12
4.7
5.1
11
6.4
4.1
6.4
4.1
5.6
6.7
3.7
6.1
6.3
3.4
3.7
4.4
3.7
8.7
3.5
5.4
6.1
5.2
4.5
2.8
95
100
100
85
95
100
90
95
100
90
100
100
95
100
100
100
100
95
95
100
100
95
100
100
21
22
20
19
18
23
19
22
22
22
23
21
21
23
22
19
23
21
22
22
23
21
23
24
524.2-39
3.7
3.4
2.8
7.3
2.5
4.7
2.2
2.9
6.4
3.4
2.6
2.5
3.8
2.9
3.1
3.8
3.3
5.5
2.5
4.8
5.1
2.6
3.9
3.2
105
110
100
95
90
115
95
110
110
110
115
105
105
115
110
95
115
105
110
110
115
105
115
120
22
21
19
17
18
23
17
21
21
22
22
21
21
22
21
19
23
22
22
21
22
22
23
21
8.2
1.3
3.5
5.6
3.0
1.3
2.2
0.90
7.7
2.6
1.8
2.0
4.0
2.0
2.1
3.0
2.7
7.2
3.6
2.4
3.2
1.7
2.4
2.9
110
105
95
85
90
115
85
105
105
110
110
105
105
110
105
95
115
110
110
105
110
110
115
105
524.2-40
524.2-41
524.2-42
524.2-43
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement