APPENDIX A TO PART 136

METHODS FOR ORGANIC CHEMICAL ANALYSIS OF MUNICIPAL AND

INDUSTRIAL WASTEWATER

METHOD 624—PURGEABLES

1. Scope and Application

1.1 This method covers the determination of a number of purgeable organics. The

following parameters may be determined by this method: 

Parameter STORET No. CAS No.

Benzene ...................................... 34030 71-43-2

Bromodichloromethane .......................... 32101 75-27-4

Bromoform ................................... 32104 75-25-2

Bromomethane ................................ 34413 74-83-9

Carbon tetrachloride ............................ 32102 56-23-5

Chlorobenzene ................................ 34301 108-90-7

Chloroethane .................................. 34311 75-00-3

2-Chloroethylvinyl ether ......................... 34576 110-75-8

Chloroform ................................... 32106 67-66-3

Chloromethane ................................ 34418 74-87-3

Dibromochloromethane .......................... 32105 124-48-1

1,2-Dichlorobenzene ............................ 34536 95-50-1

1,3-Dichlorobenzene ............................ 34566 541-73-1

1,4-Dichlorobenzene ............................ 34571 106-46-7

1,1-Dichloroethane .............................. 34496 75-34-3

1,2-Dichloroethane .............................. 34531 107-06-2

1,1-Dichloroethane .............................. 34501 75-35-4

trans-1,2-Dichloroethene ......................... 34546 156-60-5

1,2-Dichloropropane ............................ 34541 78-87-5

cis-1,3-Dichloropropene .......................... 34704 10061-01-5

trans-1,3-Dichloropropene ........................ 34699 10061-02-6

Ethyl benzene ................................. 34371 100-41-4

Methylene chloride ............................. 34423 75-09-2

1,1,2,2-Tetrachloroethane ......................... 34516 79-34-5

Tetrachloroethene .............................. 34475 127-18-4

Toluene ...................................... 34010 108-88-3

1,1,1-Trichloroethene ............................ 34506 71-55-6

1,1,2-Trichloroethene ............................ 34511 79-00-5

Trichloroethane ................................ 39180 79-01-6

Trichlorofluoromethane .......................... 34488 75-69-4

Vinyl chloride ................................. 39175 75-01-4

1.2 The method may be extended to screen samples for acrolein (STORET No. 34210, CAS

No. 107-02-8) and acrylonitrile (STORET No. 34215, CAS No. 107-13-1), however, the

preferred method for these two compounds is Method 603.
1.3 This is a purge and trap gas chromatographic/mass spectrometer (GC/MS) method

applicable to the determination of the compounds listed above in municipal and

industrial discharges as provided under 40 CFR Part 136.1.

1.4 The method detection limit (MDL, defined in Section 14.1) for each parameter is 1

listed in Table 1. The MDL for a specific wastewater may differ from those listed,

depending upon the nature of interferences in the sample matrix.

1.5 Any modification to this method, beyond those expressly permitted, shall be

considered as a major modification subject to application and approval of alternate

test procedures under 40 CFR Parts 136.4 and 136.5. Depending upon the nature of

the modification and the extent of intended use, the applicant may be required to

demonstrate that the modifications will produce equivalent results when applied to

relevant wastewaters.

1.6 This method is restricted to use by or under the supervision of analysts experienced

in the operation of a purge and trap system and a gas chromatograph/mass

spectrometer and in the interpretation of mass spectra. Each analyst must

demonstrate the ability to generate acceptable results with this method using the

procedure described in Section 8.2.

2. Summary of Method

2.1 An inert gas is bubbled through a 5 mL water sample contained in a

specially-designed purging chamber at ambient temperature. The purgeables are

efficiently transferred from the aqueous phase to the vapor phase. The vapor is swept

through a sorbent trap where the purgeables are trapped. After purging is completed,

the trap is heated and backflushed with the inert gas to desorb the purgeables onto a

gas chromatographic column. The gas chromatograph is temperature programmed to

separate the purgeables which are then detected with a mass spectrometer.2,3

3. Interferences

3.1 Impurities in the purge gas, organic compounds outgassing from the plumbing ahead

of the trap, and solvent vapors in the laboratory account for the majority of

contamination problems. The analytical system must be demonstrated to be free from

contamination under the conditions of the analysis by running laboratory reagent

blanks as described in Section 8.1.3. The use of non-Teflon plastic tubing, non-Teflon

thread sealants, or flow controllers with rubber components in the purge and trap

system should be avoided.

3.2 Samples can be contaminated by diffusion of volatile organics (particularly

fluorocarbons and methylene chloride) through the septum seal into the sample

during shipment and storage. A field reagent blank prepared from reagent water and

carried through the sampling and handling protocol can serve as a check on such

contamination.

3.3 Contamination by carry-over can occur whenever high level and low level samples

are sequentially analyzed. To reduce carry-over, the purging device and sample

syringe must be rinsed with reagent water between sample analyses. Whenever an
unusually concentrated sample is encountered, it should be followed by an analysis of

reagent water to check for cross contamination. For samples containing large

amounts of water-soluble materials, suspended solids, high boiling compounds or

high pureeable levels, it may be necessary to wash the purging device with a

detergent solution, rinse it with distilled water, and then dry it in a 105°C oven

between analyses. The trap and other parts of the system are also subject to

contamination; therefore, frequent bakeout and purging of the entire system may be

required.

4. Safety

4.1 The toxicity or carcinogenicity of each reagent used in this method has not been

precisely defined; however, each chemical compound should be treated as a potential

health hazard. From this viewpoint, exposure to these chemicals must be reduced to

the lowest possible level by whatever means available. The laboratory is responsible

for maintaining a current awareness file of OSHA regulations regarding the safe

handling of the chemicals specified in this method. A reference file of material data

handling sheets should also be made available to all personnel involved in the

chemical analysis. Additional references to laboratory safety are available and have

been identified for the information of the analyst. 4-6

4.2. The following parameters covered by this method have been tentatively classified as

known or suspected, human or mammalian carcinogens: benzene, carbon

tetrachloride, chloroform, 1,4-dichlorobenzene, and vinyl chloride. Primary standards

of these toxic compounds should be prepared in a hood. A NIOSH/MESA approved

toxic gas respirator should be worn when the analyst handles high concentrations of

these toxic compounds.

5. Apparatus and Materials

5.1 Sampling equipment, for discrete sampling.

5.1.1 Vial—25 mL capacity or larger, equipped with a screw cap with a hole in the

center (Pierce #13075 or equivalent). Detergent wash, rinse with tap and

distilled water, and dry at 105°C before use.

5.1.2 Septum—Teflon-faced silicone (Pierce #12722 or equivalent). Detergent wash,

rinse with tap and distilled water, and dry at 105°C for one hour before use.

5.2 Purge and trap system—The purge and trap system consists of three separate pieces

of equipment: A purging device, trap, and desorber. Several complete systems are

now commercially available.

5.2.1 The purging device must be designed to accept 5 mL samples with a water

column at least 3 cm deep. The gaseous head space between the water column

and the trap must have a total volume of less than 15 mL. The purge gas

must pass though the water column as finely divided bubbles with a diameter

of less than 3 mm at the origin. The purge gas must be introduced no more

than 5 mm from the base of the water column. The purging device illustrated

in Figure 1 meets these design criteria.
5.2.2 The trap must be at least 25 cm long and have an inside diameter of at least

0.105 in. The trap must be packed to contain the following minimum lengths

of adsorbents: 1.0 cm of methyl silicone coated packing (Section 6.3.2), 15 cm

of 2,6-dyphenylene oxide polymer (Section 6.3.1), and 8 cm of silica gel

(Section 6.3.3). The minimum specifications for the trap are illustrated in

Figure 2.

5.2.3 The desorber should be capable of rapidly heating the trap to 180°C. The

polymer section of the trap should not be heated higher than 180°C and the

remaining sections should not exceed 200°C. The desorber illustrated in

Figure 2 meets these design criteria.

5.2.4 The purge and trap system may be assembled as a separate unit or be coupled

to a gas chromatograph as illustrated in Figures 3 and 4.

5.3 GC/MS system

5.3.1 Gas chromatograph—An analytical system complete with a temperature

programmable gas chromatograph suitable for on-column injection and all

required accessories including syringes, analytical columns, and gases.

5.3.2 Column—6 ft long x 0.1 in ID stainless steel or glass, packed with 1% SP-1000

on Carbopack B (60/80 mesh) or equivalent. This column was used to develop

the method performance statements in Section 14. Guidelines for the use of

alternate column packings are provided in Section 11.1.

5.3.3 Mass spectrometer—Capable of scanning from 20-260 amu every

seven seconds or less, utilizing 70 V (nominal) electron energy in the electron

impact ionization mode, and producing a mass spectrum which meets all the

criteria in Table 2 when 50 ng of 4-bromofluorobenzene (BFB) is injected

through the GC inlet.

5.3.4 GC/MS interface—Any GC to MS interface that gives acceptable calibration

points at 50 ng or less per injection for each of the parameters of interest and

achieves all acceptable performance criteria (Section 10) may be used. GC to

MS interfaces constructed of all glass or glass-lined materials are

recommended. Glass can be deactivated by silanizing with

dichlorodimethylsilane.

5.3.5 Data system—A computer system must be interfaced to the mass spectrometer

that allows the continuous acquisition and storage on machine-readable media

of all mass spectra obtained throughout the duration of the chromatographic

program. The computer must have software that allows searching any

GC/MS data file for specific m/z (masses) and plotting such m/z abundances

versus time or scan number. This type of plot is defined as an Extracted Ion

Current Profile (EICP). Software must also be available that allows integrating

the abundance in any EICP between specified time or scan number limits.

5.4 Syringes—5 mL, glass hypodermic with Luerlok tip (two each), if applicable to the

purging device.
5.5 Micro syringes—25 μL, 0.006 in. ID needle.

5.6 Syringe valve—Two-way, with Luer ends (three each).

5.7 Syringe—5 mL, gas-tight with shut-off valve.

5.8 Bottle—15 mL, screw-cap, with Teflon cap liner.

5.9 Balance—Analytical, capable of accurately weighing 0.0001 g.

6. Reagents

6.1 Reagent water—Reagent water is defined as a water in which an interferent is not

observed at the MDL of the parameters of interest.

6.1.1 Reagent water can be generated by passing tap water through a carbon filter

bed containing about 1 lb of activated carbon (Filtrasorb-300, Calgon Corp., or

equivalent).

6.1.2 A water purification system (Millipore Super-Q or equivalent) may be used to

generate reagent water.

6.1.3 Reagent water may also be prepared by boiling water for 15 minutes.

Subsequently, while maintaining the temperature at 90°C, bubble a

contaminant-free inert gas through the water for one hour. While still hot,

transfer the water to a narrow mouth screw-cap bottle and seal with a

Teflon-lined septum and cap.

6.2 Sodium thiosulfate—(ACS) Granular.

6.3 Trap materials

6.3.1 2,6-Diphenylene oxide polymer—Tenax, (60/80 mesh), chromatographic grade

or equivalent.

6.3.2 Methyl silicone packing—3% OV-1 on Chromosorb-W (60/80 mesh) or

equivalent.

6.3.3 Silica gel—35/60 mesh, Davison, Grade-15 or equivalent.

6.4 Methanol—Pesticide quality or equivalent.

6.5 Stock standard solutions—Stock standard solutions may be prepared from pure

standard materials or purchased as certified solutions. Prepare stock standard

solutions in methanol using assayed liquids or gases as appropriate. Because of the

toxicity of some of the compounds, primary dilutions of these materials should be

prepared in a hood. A NIOSH/MESA approved toxic gas respirator should be used

when the analyst handles high concentrations of such materials.
6.5.1 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. Weigh the flask to the nearest

0.1 mg.

6.5.2 Add the assayed reference material

6.5.2.1 Liquids—Using a 100 μL syringe, immediately add two or more drops

of assayed reference material to the flask, then reweigh. Be sure that

the drops fall directly into the alcohol without contacting the neck of

the flask.

6.5.2.2 Gases—To prepare standards for any of the four halocarbons that boil

below 30°C (bromomethane, chloroethane, chloromethane, and vinyl

chloride), fill a 5 mL valved gas-tight syringe with the reference

standard to the 5.0 mL mark. Lower the needle to 5 mm above the

methanol meniscus. Slowly introduce the reference standard above the

surface of the liquid (the heavy gas will rapidly dissolve in the

methanol).

6.5.3 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 assayed to be 96% or greater, the weight may be

used without correction to calculate the concentration of the stock standard.

Commercially prepared stock standards may be used at any concentration if

they are certified by the manufacturer or by an independent source.

6.5.4 Transfer the stock standard solution into a Teflon-sealed screw-cap bottle.

Store, with minimal headspace, at -10 to -20°C and protect from light.

6.5.5 Prepare fresh standards weekly for the four gases and 2-chloroethylvinyl ether.

All other standards must be replaced after one month, or sooner if comparison

with check standards indicates a problem.

6.6 Secondary dilution standards—Using stock solutions, prepare secondary dilution

standards in methanol that contain the compounds of interest, either singly or mixed

together. The secondary dilution standards should be prepared at concentrations such

that the aqueous calibration standards prepared in Section 7.3 will bracket the

working range of the analytical system. Secondary dilution standards should be

stored with minimal headspace and should be checked frequently for signs of

degradation or evaporation, especially just prior to preparing calibration standards

from them.

6.7 Surrogate standard spiking solution—Select a minimum of three surrogate compounds

from Table 3. Prepare stock standard solutions for each surrogate standard in

methanol as described in Section 6.5. Prepare a surrogate standard spiking solution

from these stock standards at a concentration of 15 μg/mL in water. Store the

solutions at 4°C in Teflon-sealed glass containers with a minimum of headspace. The

solutions should be checked frequently for stability. The addition of 10 μL of this
solution of 5 mL of sample or standard is equivalent to a concentration of 30 μg/L of

each surrogate standard.

6.8 BFB Standard—Prepare a 25 μg/mL solution of BFB in methanol.

6.9 Quality control check sample concentrate—See Section 8.2.1.

7. Calibration

7.1 Assemble a purge and trap system that meets the specifications in Section 5.2.

Condition the trap overnight at 180°C by backflushing with an inert gas flow of at

least 20 mL/min. Condition the trap for 10 minutes once daily prior to use.

7.2 Connect the purge and trap system to a gas chromatograph. The gas chromatograph

must be operated using temperature and flow rate conditions equivalent to those

given in Table 1.

7.3 Internal standard calibration procedure—To use this approach, the analyst must select

three or more internal standards that are similar in analytical behavior to the

compounds of interest. The analyst must further demonstrate that the measurement

of the internal standard is not affected by method or matrix interferences. Some

recommended internal standards are listed in Table 3.

7.3.1 Prepare calibration standards at a minimum of three concentration levels for

each parameter by carefully adding 20.0 μL of one or more secondary dilution

standards to 50 mL, 250 mL, or 500 mL of reagent water. A 25 μmL syringe

with a 0.006 in. ID needle should be used for this operation. One of the

calibration standards should be at a concentration near, but above, the MDL

(Table 1) and the other concentrations should correspond to the expected range

of concentrations found in real samples or should define the working range of

the GC/MS system. These aqueous standards can be stored up to 24 hours, if

held in sealed vials with zero headspace as described in Section 9.2. If not so

stored, they must be discarded after one hour.

7.3.2 Prepare a spiking solution containing each of the internal standards using the

procedures described in Sections 6.5 and 6.6. It is recommended that the

secondary dilution standard be prepared at a concentration of 15 μg/mL of

each internal standard compound. The addition of 10 μL of this standard to

5.0 mL of sample or calibration standard would be equivalent to 30 μg/L.

7.3.3 Analyze each calibration standard according to Section 11, adding 10 μL of

internal standard spiking solution directly to the syringe (Section 11.4).

Tabulate the area response of the characteristic m/z against concentration for

each compound and internal standard, and calculate response factors (RF) for

each compound using Equation 1. 
This equation corrects an error made in the original method publication (49 FR 43234, *

October 26, 1984). This correction will be formalized through a rulemaking in FY97.

Equation 1

where:

A = Area of the characteristic m/z for the parameter to be measured. s

A = Area of the characteristic m/z for the internal standard. is

C = Concentration of the internal standard. is

C = Concentration of the parameter to be measured. s

If the RF value over the working range is a constant (<35% RSD), the RF can

be assumed to be invariant and the average RF can be used for calculations.

Alternatively, the results can be used to plot a calibration curve of response

ratios, A /A , vs. concentration ratios C /C . s is s is

*

7.4 The working calibration curve or RF must be verified on each working day by the

measurement of a QC check sample.

7.4.1 Prepare the QC check sample as described in Section 8.2.2.

7.4.2 Analyze the QC check sample according to the method beginning in

Section 10.

7.4.3 For each parameter, compare the response (Q) with the corresponding

calibration acceptance criteria found in Table 5. If the responses for all

parameters of interest fall within the designated ranges, analysis of actual

samples can begin. If any individual Q falls outside the range, proceed

according to Section 7.4.4.

NOTE: The large number of parameters in Table 5 present a substantial

probability that one or more will not meet the calibration

acceptance criteria when all parameters are analyzed.

7.4.4 Repeat the test only for those parameters that failed to meet the calibration

acceptance criteria. If the response for a parameter does not fall within the

range in this second test, a new calibration curve or RF must be prepared for

that parameter according to Section 7.3.

8. Quality Control

8.1 Each laboratory that uses this method is required to operate a formal quality control

program. The minimum requirements of this program consist of an initial

demonstration of laboratory capability and an ongoing analysis of spiked samples to

evaluate and document data quality. The laboratory must maintain records to
document the quality of data that is generated. Ongoing data quality checks are

compared with established performance criteria to determine if the results of analyses

meet the performance characteristics of the method. When results of sample spikes

indicate atypical method performance, a quality control check standard must be

analyzed to confirm that the measurements were performed in an in-control mode of

operation.

8.1.1 The analyst must make an initial, one-time, demonstration of the ability to

generate acceptable accuracy and precision with this method. This ability is

established as described in Section 8.2.

8.1.2 In recognition of advances that are occurring in chromatography, the analyst is

permitted certain options (detailed in Section 11.1) to improve the separations

or lower the cost of measurements. Each time such a modification is made to

the method, the analyst is required to repeat the procedure in Section 8.2.

8.1.3 Each day, the analyst must analyze a reagent water blank to demonstrate that

interferences from the analytical system are under control.

8.1.4 The laboratory must, on an ongoing basis, spike and analyze a minimum of

5% of all samples to monitor and evaluate laboratory data quality. This

procedure is described in Section 8.3.

8.1.5 The laboratory must, on an ongoing basis, demonstrate through the analyses of

quality control check standards that the operation of the measurement system

is in control. This procedure is described in Section 8.4. The frequency of the

check standard analyses is equivalent to 5% of all samples analyzed but may

be reduced if spike recoveries from samples (Section 8.3) meet all specified

quality control criteria.

8.1.6 The laboratory must spike all samples with surrogate standards to monitor

continuing laboratory performance. This procedure is described in Section 8.5.

8.1.7 The laboratory must maintain performance records to document the quality of

data that is generated. This procedure is described in Section 8.6.

8.2 To establish the ability to generate acceptable accuracy and precision, the analyst must

perform the following operations.

8.2.1 A quality control (QC) check sample concentrate is required containing each

parameter of interest at a concentration of 10 μg/mL in methanol. The QC

check sample concentrate must be obtained from the U.S. Environmental

Protection Agency, Environmental Monitoring and Support Laboratory in

Cincinnati, Ohio, if available. If not available from that source, the QC check

sample concentrate must be obtained from another external source. If not

available from either source above, the QC check sample concentrate must be

prepared by the laboratory using stock standards prepared independently from

those used for calibration.
8.2.2 Prepare a QC check sample to contain 20 μg/L of each parameter by adding

200 μL of QC check sample concentrate to 100 mL of reagent water.

8.2.3 Analyze four 5 mL aliquots of the well-mixed QC check sample according to

the method beginning in Section 10.

8.2.4 Calculate the average recovery ( ) in μg/L, and the standard deviation of

the recovery (s) in μg/L, for each parameter of interest using the four results.

8.2.5 For each parameter compare s and with the corresponding acceptance

criteria for precision and accuracy, respectively, found in Table 5. If s and 

for all parameters of interest meet the acceptance criteria, the system

performance is acceptable and analysis of actual samples can begin. If any

individual s exceeds the precision limit or any individual falls outside the

range for accuracy, the system performance is unacceptable for that parameter.

NOTE: The large number of parameters in Table 5 present a substantial

probability that one or more will fail at least one of the

acceptance criteria when all parameters are analyzed.

8.2.6 When one or more of the parameters tested fail at least one of the acceptance

criteria, the analyst must proceed according to Section 8.2.6.1 or 8.2.6.2.

8.2.6.1 Locate and correct the source of the problem and repeat the test for all

parameters of interest beginning with Section 8.2.3.

8.2.6.2 Beginning with Section 8.2.3, repeat the test only for those parameters

that failed to meet criteria. Repeated failure, however, will confirm a

general problem with the measurement system. If this occurs, locate

and correct the source of the problem and repeat the test for all

compounds of interest beginning with Section 8.2.3.

8.3 The laboratory must, on an ongoing basis, spike at least 5% of the samples from each

sample site being monitored to assess accuracy. For laboratories analyzing one to 20

samples per month, at least one spiked sample per month is required.

8.3.1 The concentration of the spike in the sample should be determined as follows:

8.3.1.1 If, as in compliance monitoring, the concentration of a specific

parameter in the sample is being checked against a regulatory

concentration limit, the spike should be at that limit or one to five times

higher than the background concentration determined in Section 8.3.2,

whichever concentration would be larger.

8.3.1.2 If the concentration of a specific parameter in the sample is not being

checked against a limit specific to that parameter, the spike should be

at 20 μg/L or one to five times higher than the background

concentration determined in Section 8.3.2, whichever concentration

would be larger.
8.3.2 Analyze one 5 mL sample aliquot to determine the background concentration

(B) of each parameter. If necessary, prepare a new QC check sample

concentrate (Section 8.2.1) appropriate for the background concentrations in the

sample. Spike a second 5 mL sample aliquot with 10 μL of the QC check

sample concentrate and analyze it to determine the concentration after spiking

(A) of each parameter. Calculate each percent recovery (P) as 100 (A-B)%/T,

where T is the known true value of the spike.

8.3.3 Compare the percent recovery (P) for each parameter with the corresponding

QC acceptance criteria found in Table 5. These acceptance criteria were

calculated to include an allowance for error in measurement of both the

background and spike concentrations, assuming a spike to background ratio of

5:1. This error will be accounted for to the extent that the analyst's spike to

background ratio approaches 5:1. If spiking was performed at a concentration 7

lower than 20 μg/L, the analyst must use either the QC acceptance criteria in

Table 5, or optional QC acceptance criteria calculated for the specific spike

concentration. To calculate optional acceptance criteria for the recovery of a

parameter: (1) Calculate accuracy (X′) using the equation in Table 6,

substituting the spike concentration (T) for C; (2) calculate overall precision (S′)

using the equation in Table 6, substituting X′ for ; (3) calculate the range for

recovery at the spike concentration as (100 X′/T) ±2.44 (100 S′/T)%.7

8.3.4 If any individual P falls outside the designated range for recovery, that

parameter has failed the acceptance criteria. A check standard containing each

parameter that failed the criteria must be analyzed as described in Section 8.4.

8.4 If any parameter fails the acceptance criteria for recovery in Section 8.3, a QC check

standard containing each parameter that failed must be prepared and analyzed.

NOTE: The frequency for the required analysis of a QC check standard will

depend upon the number of parameters being simultaneously tested,

the complexity of the sample matrix, and the performance of the

laboratory. If the entire list of parameters in Table 5 must be measured

in the sample in Section 8.3, the probability that the analysis of a QC

check standard will be required is high. In this case the QC check

standard should be routinely analyzed with the spiked sample.

8.4.1 Prepare the QC check standard by adding 10 μL of QC check sample

concentrate (Section 8.2.1 or 8.3.2) to 5 mL of reagent water. The QC check

standard needs only to contain the parameters that failed criteria in the test in

Section 8.3.

8.4.2 Analyze the QC check standard to determine the concentration measured (A)

of each parameter. Calculate each percent recovery (P ) as 100 (A/T)%, where S

T is the true value of the standard concentration.

8.4.3 Compare the percent recovery (P ) for each parameter with the corresponding S

QC acceptance criteria found in Table 5. Only parameters that failed the test

in Section 8.3 need to be compared with these criteria. If the recovery of any

such parameter falls outside the designated range, the laboratory performance
for that parameter is judged to be out of control, and the problem must be

immediately identified and corrected. The analytical result for that parameter

in the unspiked sample is suspect and may not be reported for regulatory

compliance purposes.

8.5 As a quality control check, the laboratory must spike all samples with the surrogate

standard spiking solutions as described in Section 11.4, and calculate the percent

recovery of each surrogate compound.

8.6 As part of the QC program for the laboratory, method accuracy for wastewater

samples must be assessed and records must be maintained. After the analysis of five

spiked wastewater samples as in Section 8.3, calculate the average percent recovery

( ) and the standard deviation of the percent recovery (s ). Express the accuracy p

assessment as a percent recovery interval from -2s to +2s . If =90% and s =10%, pp p

for example, the accuracy interval is expressed as 70-110%. Update the accuracy

assessment for each parameter a regular basis (e.g., after each 5-10 new accuracy

measurements).

8.7 It is recommended that the laboratory adopt additional quality assurance practices for

use with this method. The specific practices that are most productive depend upon

the needs of the laboratory and the nature of the samples. Field duplicates may be

analyzed to assess the precision of the environmental measurements. Whenever

possible, the laboratory should analyze standard reference materials and participate in

relevant performance evaluation studies.

9. Sample Collection, Preservation, and Handling

9.1 All samples must be iced or refrigerated from the time of collection until analysis. If

the sample contains residual chlorine, add sodium thiosulfate preservative

(10 mg/40 mL is sufficient for up to 5 ppm Cl ) to the empty sample bottle just prior 2

to shipping to the sampling site. EPA Methods 330.4 and 330.5 may be used for

measurement of residual chlorine. Field test kits are available for this purpose. 8

9.2 Grab samples must be collected in glass containers having a total volume of at least

25 mL. Fill the sample bottle just to overflowing in such a manner that no air bubbles

pass through the sample as the bottle is being filled. Seal the bottle so that no air

bubbles are entrapped in it. If preservative has been added, shake vigorously for

one minute. Maintain the hermetic seal on the sample bottle until time of analysis.

9.3 Experimental evidence indicates that some aromatic compounds, notably benzene,

toluene, and ethyl benzene are susceptible to rapid biological degradation under

certain environmental conditions. Refrigeration alone may not be adequate to 3

preserve these compounds in wastewaters for more than seven days. For this reason,

a separate sample should be collected, acidified, and analyzed when these aromatics

are to be determined. Collect about 500 mL of sample in a clean container. Adjust

the pH of the sample to about 2 by adding 1+1 HCl while stirring vigorously. Check

pH with narrow range (1.4-2.8) pH paper. Fill a sample container as described in

Section 9.2.

9.4 All samples must be analyzed within 14 days of collection. 3
10. Daily GC/MS Performance Tests

10.1 At the beginning of each day that analyses are to be performed, the GC/MS system

must be checked to see if acceptable performance criteria are achieved for BFB. The 9

performance test must be passed before any samples, blanks, or standards are

analyzed, unless the instrument has met the DFTPP test described in Method 625

earlier in the day.10

10.2 These performance tests require the following instrumental parameters:

Electron Energy: 70 V (nominal)

Mass Range: 20-260 amu

Scan Time: To give at least five scans per peak but not to exceed seven

seconds per scan.

10.3 At the beginning of each day, inject 2 μL of BFB solution directly on the column.

Alternatively, add 2 μL of BFB solution to 5.0 mL of reagent water or standard

solution and analyze the solution according to Section 11. Obtain a

background-corrected mass spectrum of BFB and confirm that all the key m/z criteria

in Table 2 are achieved. If all the criteria are not achieved, the analyst must retune

the mass spectrometer and repeat the test until all criteria are achieved.

11. Sample Purging and Gas Chromatography

11.1 Table 1 summarizes the recommended operating conditions for the gas

chromatograph. Included in this table are retention times and MDL that can be

achieved under these conditions. An example of the separations achieved by this

column is shown in Figure 5. Other packed columns or chromatographic conditions

may be used if the requirements of Section 8.2 are met.

11.2 After achieving the key m/z abundance criteria in Section 10, calibrate the system

daily as described in Section 7.

11.3 Adjust the purge gas (helium) flow rate to 40 mL/min. Attach the trap inlet to the

purging device, and set the purge and trap system to purge (Figure 3). Open the

syringe valve located on the purging device sample introduction needle.

11.4 Allow the sample to come to ambient temperature prior to introducing it into the

syringe. Remove the plunger from a 5 mL syringe and attach a closed syringe valve.

Open the sample bottle (or standard) and carefully 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 5.0 mL. Since this process of taking an aliquot destroys the validity of the

sample for future analysis, the analyst should fill a second syringe at this time to

protect against possible loss of data. Add 10.0 μL of the surrogate spiking solution

(Section 6.7) and 10.0 μL of the internal standard spiking solution (Section 7.3.2)

through the valve bore, then close the valve. The surrogate and internal standards

may be mixed and added as a single spiking solution.
11.5 Attach the syringe-syringe valve assembly to the syringe valve on the purging device.

Open the syringe valves and inject the sample into the purging chamber.

11.6 Close both valves and purge the sample for 11.0 ±0.1 minute at ambient temperature.

11.7 After the 11-minute purge time, attach the trap to the chromatograph, adjust the

purge and trap system to the desorb mode (Figure 4), and begin to temperature

program the gas chromatograph. Introduce the trapped materials to the GC column

by rapidly heating the trap to 180°C while backflushing the trap with an inert gas

between 20 and 60 mL/min. for four minutes. If rapid heating of the trap cannot be

achieved, the GC column must be used as a secondary trap by cooling it to 30°C

(subambient temperature, if problems persist) instead of the initial program

temperature of 45°C.

11.8 While the trap is being desorbed into the gas chromatograph, empty the purging

chamber using the sample introduction syringe. Wash the chamber with two 5 mL

flushes of reagent water.

11.9 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. The trap temperature

should be maintained at 180°C. 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.

11.10 If the response for any m/z exceeds the working range of the system, prepare a

dilution of the sample with reagent water from the aliquot in the second syringe and

reanalyze.

12. Qualitative Identification

12.1 Obtain EICPs for the primary m/z (Table 4) and at least two secondary masses for

each parameter of interest. The following criteria must be met to make a qualitative

identification:

12.1.1 The characteristic masses of each parameter of interest must maximize in the

same or within one scan of each other.

12.1.2 The retention time must fall within ±30 seconds of the retention time of the

authentic compound.

12.1.3 The relative peak heights of the three characteristic masses in the EICPs must

fall within ±20% of the relative intensities of these masses in a reference mass

spectrum. The reference mass spectrum can be obtained from a standard

analyzed in the GC/MS system or from a reference library.

12.2 Structural isomers that have very similar mass spectra and less than 30 seconds

difference in retention time, can be explicitly identified only if the resolution between

authentic isomers in a standard mix is acceptable. Acceptable resolution is achieved if
the baseline to valley height between the isomers is less than 25% of the sum of the

two peak heights. Otherwise, structural isomers are identified as isomeric pairs.

13. Calculations

13.1 When a parameter has been identified, the quantitation of that parameter should be

based on the integrated abundance from the EICP of the primary characteristic m/z

given in Table 4. If the sample produces an interference for the primary m/z, use a

secondary characteristic m/z to quantitate.

Calculate the concentration in the sample using the response factor (RF) determined in

Section 7.3.3 and Equation 2.

Equation 2

where:

A = Area of the characteristic m/z for the parameter or surrogate standard to S

 be measured.

A = Area of the characteristic m/z for the internal standard. is

C = Concentration of the internal standard. is

13.2 Report results in μg/L without correction for recovery data. All QC data obtained

should be reported with the sample results.

14. Method Performance

14.1 The method detection limit (MDL) is defined as the minimum concentration of a

substance that can be measured and reported with 99% confidence that the value is

above zero. The MDL concentrations listed in Table 1 were obtained using reagent 1

water. Similar results were achieved using representative wastewaters. The MDL 11

actually achieved in a given analysis will vary depending on instrument sensitivity

and matrix effects.

14.2 This method was tested by 15 laboratories using reagent water, drinking water,

surface water, and industrial wastewaters spiked at six concentrations over the range

5-600 μg/L. Single operator precision, overall precision, and method accuracy were 12

found to be directly related to the concentration of the parameter and essentially

independent of the sample matrix. Linear equations to describe these relationships

are presented in Table 5.
References

1. 40 CFR Part 136, Appendix B.

2. Bellar, T.A. and Lichtenberg, J.J. “Determining Volatile Organics at

Microgram-per-Litre Levels by Gas Chromatography,” Journal American Water Works

Association, 66, 739 (1974).

3. Bellar, T.A. and Lichtenberg, J.J. “Semi-Automated Headspace Analysis of Drinking

Waters and Industrial Waters for Purgeable Volatile Organic Compounds,”

Measurement of Organic Pollutants in Water and Wastewater, C.E. Van Hall, editor,

American Society for Testing and Materials, Philadelphia, PA. Special Technical

Publication 686, 1978.

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 Part 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. Provost, L.P. and Elder, R.S. “Interpretation of Percent Recovery Data,” American

Laboratory, 15, 58-63 (1983). (The value 2.44 used in the equation in Section 8.2.3 is

two times the value 1.22 derived in this report.)

8. “Methods 330.4 (Titrimetric, DPD-FAS) and 330.5 (Spectrophotometric, DPD) for

Chlorine, Total Residual,” Methods for Chemical Analysis of Water and Wastes,

EPA-600/4-79-020, U.S. Environmental Protection Agency, Environmental Monitoring

and Support Laboratory, Cincinnati, Ohio 45268, March 1979.

9. Budde, W.L. and Eichelberger, J.W. “Performance Tests for the Evaluation of

Computerized Eas Chromatography/Mass Spectrometry Equipment and

Laboratories,” EPA-600/4-80-025, U.S. Environmental Protection Agency,

Environmental Monitoring and Support Laboratory, Cincinnati, Ohio 45268,

April 1980.

10. Eichelberger, J.W., Harris, L.E., and Budde, W.L. “Reference Compound to Calibrate

Ion Abundance Measurement in Gas Chromatography-Mass Spectrometry Systems,”

Analytical Chemistry, 47, 995-1000 (1975).

11. “Method Detection Limit for Methods 624 and 625,” Olynyk, P., Budde, W.L., and

Eichelberger, J.W. Unpublished report, May 14, 1980.

12. “EPA Method Study 29 EPA Method 624-Purgeables,” EPA 600/4-84-054, National

Technical Information Service, PB84-209915, Springfield, Virginia 22161, June 1984.
13. “Method Performance Data for Method 624,” Memorandum from R. Slater and

T. Pressley, U.S. Environmental Protection Agency, Environmental Monitoring and

Support Laboratory, Cincinnati, Ohio 45268, January 17, 1984.
Table 1—Chromatographic Conditions and Method Detection Limits

Parameter detection Retention

time (min.)

Method

limit(μ/L)

Chloromethane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 nd

Bromomethane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 nd

Vinyl chloride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8 nd

Chloroethane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 nd

Methylene chloride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 2.8

Trichlorofluoromethane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 nd

1,1-Dichloroethene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.0 2.8

1,1-Dichloroethane ..................................... 10.1 4.7

trans-1,2-Dichloroethene ................................ 10.8 1.6

Chloroform .......................................... 11.4 1.6

1,2-Dichloroethane ..................................... 12.1 2.8

1,1,1-Trichloroethane ................................... 13.4 3.8

Carbon tetrachloride ................................... 13.7 2.8

Bromodichloromethane ................................. 14.3 2.2

1,2-Dichloroproane .................................... 15.7 6.0

cis-1,3-Dichloropropene ................................. 15.9 5.0

Trichloroethene ....................................... 16.5 1.9

Benzene ............................................. 17.0 4.4

Dibromochloromethane ................................. 17.1 3.1

1,1,2-Trichloroethane ................................... 17.2 5.0

trans-1,3-Dichloropropene ............................... 17.2 nd

2-Chloroethylvinlyl ether ................................ 18.6 nd

Bromoform .......................................... 19.8 4.7

1,1,2,2-Tetrachloroethane ................................ 22.1 6.9

Tetrachloroethene ..................................... 22.2 4.1

Toluene ............................................. 23.5 6.0

Chlorobenzene ....................................... 24.6 6.0

Ethyl benzene ........................................ 26.4 7.2

1,3-Dichlorobenzene ................................... 33.9 nd

1,2-Dichlorobenzene ................................... 35.0 nd

1,4-Dichlorobenzene ................................... 35.4 nd

Column conditions: Carbopak B (60/80 mesh) coated with 1% SP-1000 packed in a 6 ft by

0.1 in. ID glass column with helium carrier gas at 30 mL/min. flow rate. Column

temperature held at 45°C for three minutes, then programmed at 8°C/min. to 220°C and

held for 15 minutes.

nd = Not determined.
Table 2—BFB Key m/z Abundance Criteria

Mass m/z Abundance criteria

50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-40% of Mass 95.

75 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30-60% of Mass 95.

95 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Base Peak, 100% Relative Abundance.

96 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9% of Mass 95.

173 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . <2% of Mass 174.

174 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . >50% of Mass 95.

175 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9% of Mass 174.

176 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . >95% but 101% of Mass 174.

177 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9% of Mass 176.

Table 3—Suggested Surrogate and Internal Standards

Compound Secondary masses Retention Primary

time (min) m/z a

Benzene d-6 ........................... 17.0 84 . . . . . . . . . . . . . . .

4-Bromofluorobenzene .................. 28.3 95 174, 176

1,2-Dichloroethane d-4 .................. 12.1 102 . . . . . . . . . . . . . . .

1,4-Difluorobenzene .................... 19.6 114 63, 88

Ethylbenzene d-5 ....................... 26.4 111 . . . . . . . . . . . . . . .

Ethylbenzene d-10 ...................... 26.4 98 . . . . . . . . . . . . . . .

Fluorobenzene ........................ 18.4 96 70

Pentafluorobenzene ..................... 23.5 168 . . . . . . . . . . . . . . .

Bromochloromethane . . . . . . . . . . . . . . . . . . . 9.3 128 49, 130, 51

2-Bromo-1-chloropropane ................ 19.2 77 79, 156

1,4-Dichlorobutane ..................... 25.8 55 90, 92

For chromatographic conditions, see Table 1. a
Table 4—Characteristic Masses for Purgeable Organics

Parameter Primary Secondary

Chloromethane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 52.

Bromomethane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 96.

Vinyl chloride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 64.

Chloroethane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 66.

Methylene chloride . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 49, 51, and 86.

Trichlorofluoromethane . . . . . . . . . . . . . . . . . . . . . . . . 101 103.

1,1-Dichloroethene . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 61 and 98.

1,1-Dichloroethane . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 65, 83, 85, 98, and 100.

trans-1,2-Dichloroethene . . . . . . . . . . . . . . . . . . . . . . . 96 61 and 98.

Chloroform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 85.

1,2-Dichloroethane . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 62, 64, and 100.

1,1,1-Trichloroethane . . . . . . . . . . . . . . . . . . . . . . . . . . 97 99, 117, and 119.

Carbon tetrachloride . . . . . . . . . . . . . . . . . . . . . . . . . . 117 119 and 121.

Bromodichloromethane . . . . . . . . . . . . . . . . . . . . . . . . 127 83, 85, and 129.

1,2-Dichloropropane . . . . . . . . . . . . . . . . . . . . . . . . . . 112 63, 65, and 114.

trans-1,3-Dichloropropene . . . . . . . . . . . . . . . . . . . . . . 75 77.

Trichloroethene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 95, 97, and 132.

Benzene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 . . . . . . . . . . . . . . .

Dibromochloromethane . . . . . . . . . . . . . . . . . . . . . . . . 127 129, 208, and 206.

1,1,2-Trichloroethane . . . . . . . . . . . . . . . . . . . . . . . . . . 97 83, 85, 99, 132, and

134.

cis-1,3-Dichloropropene . . . . . . . . . . . . . . . . . . . . . . . . 75 77.

2-Chloroethylvinyl ether . . . . . . . . . . . . . . . . . . . . . . . 106 63 and 65.

Bromoform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 171, 175, 250, 252, 254,

and 256.

1,1,2,2-Tetrachloroethane . . . . . . . . . . . . . . . . . . . . . . . 168 83, 85, 131, 133, and

166.

Tetrachloroethene . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 129, 131, and 166.

Toluene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 91.

Chlorobenzene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 114.

Ethyl benzene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 91.

1,3-Dichlorobenzene . . . . . . . . . . . . . . . . . . . . . . . . . . 146 148 and 113.

1,2-Dichlorobenzene . . . . . . . . . . . . . . . . . . . . . . . . . . 146 148 and 113.

1,4-Dichlorobenzene . . . . . . . . . . . . . . . . . . . . . . . . . . 146 148 and 113.
Table 5—Calibration and QC Acceptance Criteria-Method 624a

Parameter Range for Limit for Range for Range for P,

Q (μ/g/L) s (μ/g/L) (μ/g/L) P (%) s

Benzene .......................... 12.8 - 27.2 6.9 15.2 - 26.0 37 - 151

Bromodichloromethane .............. 13.1 - 26.9 6.4 10.1 - 28.0 35 - 155

Bromoform ....................... 14.2 - 25.8 5.4 11.4 - 31.1 45 - 169

Bromomethane .................... 2.8 - 37.2 17.9 D - 41.2 D - 242

Carbon tetrachloride ................ 14.6 - 25.4 5.2 17.2 - 23.5 70 - 140

Chlorobenzene .................... 13.2 - 26.8 6.3 16.4 - 27.4 37 - 160

Chloroethane ...................... 7.6 - 32.4 11.4 8.4 - 40.4 14 - 230

2-Chloroethylvinyl ether . . . . . . . . . . . . . D - 44.8 25.9 D - 50.4 D - 305

Chloroform ....................... 13.5 - 26.5 6.1 13.7 - 24.2 51 - 138

Chloromethane . . . . . . . . . . . . . . . . . . . . D - 40.8 19.8 D - 45.9 D - 273

Dibromochloromethane .............. 13.5 - 26.5 6.1 13.8 - 26.6 53 - 149

1,2-Dichlorobenzene ................ 12.6 - 27.4 7.1 11.8 - 34.7 18 - 190

1,3-Dichlorobenzene ................ 14.6 - 25.4 5.5 17.0 - 28.8 59 - 156

1,4-Dichlorobenzene ................ 12.6 - 27.4 7.1 11.8 - 34.7 18 - 190

1,1-Dichloroethane .................. 14.5 - 25.5 5.1 14.2 - 28.5 59 - 155

1,2-Dichloroethane .................. 13.6 - 26.4 6.0 14.3 - 27.4 49 - 155

1,1-Dichlorothene .................. 10.1 - 29.9 9.1 3.7 - 42.3 D - 234

trans-1,2-Dichloroethene ............. 13.9 - 26.1 5.7 13.6 - 28.5 54 - 156

1,2-Dichloropropane ................ 6.8 - 33.2 13.8 3.8 - 36.2 D - 210

cis-1,3-Dichloropropene .............. 4.8 - 35.2 15.8 1.0 - 39.0 D - 227

trans-1,3-Dichloropropene ............ 10.0 - 30.0 10.4 7.6 - 32.4 17 - 183

Ethyl benzene ..................... 11.8 - 28.2 7.5 17.4 - 26.7 37 - 162

Methylene chloride ................. 12.1 - 27.9 7.4 D - 41.0 D - 221

1,1,2,2-Tetrachloroethane ............. 12.1 - 27.9 7.4 13.5 - 27.2 46 - 157

Tetrachloroethene .................. 14.7 - 25.3 5.0 17.0 - 26.6 64 - 148

Toluene .......................... 14.9 - 25.1 4.8 16.6 - 26.7 47 - 150

1,1,1-Trichloroethane ................ 15.0 - 25.0 4.6 13.7 - 30.1 52 - 162

1,1,2-Trichloroethane ................ 14.2 - 25.8 5.5 14.3 - 27.1 52 - 150

Trichloroethene .................... 13.3 - 26.7 6.6 18.6 - 27.6 71 - 157

Trichlorofluoromethane .............. 9.6 - 30.4 10.0 8.9 - 31.5 17 - 181

Vinyl chloride ..................... 0.8 - 39.2 20.0 D - 43.5 D - 251

Q = Concentration measured in QC check sample, in μg/L (Section 7.5.3).

s = Standard deviation of four recovery measurements, in μg/L (Section 8.2.4).

 = Average recovery of four recovery measurements, in μg/L (Section 8.2.4).

P, P = Percent recovery measured, (Section 8.3.2, Section 8.4.2). s

D = Detected; result must be greater than zero.

Criteria were calculated assuming a QC check sample concentration of 20 μg/L. a

NOTE: These criteria are based directly upon the method performance data in Table 6.

Where necessary, the limits for recovery have been broadened to assure

applicability of the limits to concentrations below those used to develop

Table 6.
Table 6—Method Accuracy and Precision as Functions of Concentration—Method 624

Parameter recovery, precision, precision,

Accuracy, as Single analyst Overall

X' (μ/g/L) s ' (μ/g/L) S' (μ/g/L) r

Benzene ............................ 0.93C+2.00 0.26 -1.74 0.25 -1.33

Bromodichloromethane ................ 1.03C-1.58 0.15 +0.59 0.20 +1.13

Bromoform ......................... 1.18C-2.35 0.12 +0.36 0.17 +1.38

Bromomethane ...................... a 1.00C 0.43 0.58

Carbon tetrachloride .................. 1.10C-1.68 0.12 +0.25 0.11 +0.37

Chlorobenzene ...................... 0.98C+2.28 0.16 -0.09 0.26 -1.92

Chloroethane ........................ 1.18C+0.81 0.14 +2.78 0.29 +1.75

2-Chloroethylvinyl ether ............... a 1.00C 0.62 0.84

Chloroform ......................... 0.93C+0.33 0.16 +0.22 0.18 +0.16

Chloromethane ...................... 1.03C+0.81 0.37 +2.14 0.58 +0.43

Dibromochloromethane ................ 1.01C-0.03 0.17 -0.18 0.17 +0.49

1,2-Dichlorobenzene ................. b 0.94C+4.47 0.22 -1.45 0.30 -1.20

1,3-Dichlorobenzene .................. 1.06C+1.68 0.14 -0.48 0.18 -0.82

1,4-Dichlorobenzene .................. b 0.94C+4.47 0.22 -1.45 0.30 -1.20

1,1-Dichloroethane .................... 1.05C+0.36 0.13 -0.05 0.16 +0.47

1,2-Dichloroethane .................... 1.02C+0.45 0.17 -0.32 0.21 -0.38

1,1-Dichloroethene .................... 1.12C+0.61 0.17 +1.06 0.43 -0.22

trans-1,2,-Dichloroethene ............... 1.05C+0.03 0.14 +0.09 0.19 +0.17

1,2-Dichloropropane ................. a 1.00C 0.33 0.45

cis-1,3-Dichloropropene .............. a 1.00C 0.38 0.52

trans-1,3-Dichloropropene ............. a 1.00C 0.25 0.34

Ethyl benzene ....................... 0.98C+2.48 0.14 +1.00 0.26 -1.72

Methylene chloride ................... 0.87C+1.88 0.15 +1.07 0.32 +4.00

1,1,2,2-Tetrachloroethane ............... 0.93C+1.76 0.16 +0.69 0.20 +0.41

Tetrachloroethene .................... 1.06C+0.60 0.13 -0.18 0.16 -0.45

Toluene ............................ 0.98C+2.03 0.15 -0.71 0.22 -1.71

1,1,1-Trichloroethane .................. 1.06C+0.73 0.12 -0.15 0.21 -0.39

1,1,2-Trichloroethane .................. 0.95C+1.71 0.14 +0.02 0.18 +0.00

Trichloroethene ...................... 1.04C+2.27 0.13 +0.36 0.12 +0.59

Trichloroflouromethane ................ 0.99C+0.39 0.33 -1.48 0.34 -0.39

Vinyl chloride ....................... 1.00C 0.48 0.65

X' = Expected recovery for one or more measurements of a sample containing a

concentration of C, in μg/L.

S = Expected single analyst standard deviation of measurements at an average concentration r

found of , in μg/L.

S' = Expected interlaboratory standard deviation of measurements at an average

concentration found of , in μg/L.

C = True value for the concentration, in μg/L.

 = Average recovery found for measurements of samples containing a concentration of C,

in μg/L.

Estimates based upon the performance in a single laboratory. a 13

Due to chromatographic resolution problems, performance statements for these isomers are b

based upon the sums of their concentrations.