Loading (50 kb)...'

(continued)

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 1 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 1 to 5 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 1 to 5 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 wer 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 5:1.7 If spiking was performed at a concentration 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 recoveryof 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 X ; (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 anlaysis 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 (PS) as 100 (A/T)%, where T is the true value of the standard concentration.

8.4.3 Compare the percent recovery (PS) for each parameter with the corresponding 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 (P ) and the standard deviation of the percent recovery (sp). Express the accuracy assessment as a percent recovery interval from P —2sp to P + 2sp. If P =90% and sp=10%, for example, the accuracy interval is expressed as 70–110%. Update the accuracy assessment for each parameter a regular basis (e.g. after each five to ten 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 Cl2) to the empty sample bottle just prior to shipping to the sampling site. EPA Methods 330.4 and 330.5 may be used for measurement of residual chlorine. 8 Field test kits are available for this purpose.

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 1 min. 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. 3 Refrigeration alone may not be adequate to 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 to 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. 9 The 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 to 260 amu

Scan Time: To give at least 5 scans per peak but not to exceed 7 s 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 daiy 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 min at ambient temperature.

11.7 After the 11-min 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 4 min. If rapid heating of the trap cannot be achieved, the GC cloumn 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 4 min, recondition the trap by returning the purge and trap system to the purge mode. Wait 15 s 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 7 min, 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 s 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 s 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:

AS=Area of the characteristic m/z for the parameter or surrogate standard to be measured.

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

Cis=Concentration of the internal standard.

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. 1 The MDL concentrations listed in Table 1 were obtained using reagent water. 11 Similar results were achieved using representative wastewaters. The MDL 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.12 Single operator precision, overall precision, and method accuracy were 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
------------------------------------------------------------------------
Method
detection
Parameter Retention limit
time (min) (µg/
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 3 min., then
programmed at 8°C/min. to 220°C and held for 15 min.
nd=not determined.




Table 2_BFB Key m/z Abundance Criteria
------------------------------------------------------------------------
Mass m/z Abundance criteria
------------------------------------------------------------------------
50........................................ 15 to 40% of mass 95.
75........................................ 30 to 60% of mass 95.
95........................................ Base Peak, 100% Relative
Abundance.
96........................................ 5 to 9% of mass 95.
173....................................... <2% of mass 174.
174....................................... >50% of mass 95.
175....................................... 5 to 9% of mass 174.
176....................................... >95% but <101% of mass
174.
177....................................... 5 to 9% of mass 176.
------------------------------------------------------------------------




Table 3_Suggested Surrogate and Internal Standards
------------------------------------------------------------------------
Retention
Compound time Primary Secondary
(min) a m/z masses
------------------------------------------------------------------------
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
------------------------------------------------------------------------
a For chromatographic conditions, see Table 1.




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 624 a
----------------------------------------------------------------------------------------------------------------
Limit for
Range for Q s Range for X Range for P,
Parameter (µ/g/L) (µ/ (µ/g/L) Ps (%)
g/L)
----------------------------------------------------------------------------------------------------------------
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).
X= Average recovery of four recovery measurements, in µg/L (Section 8.2.4).
P, Ps= Percent recovery measured, (Section 8.3.2, Section 8.4.2).
D= Detected; result must be greater than zero.
a Criteria were calculated assuming a QC check sample concentration of 20 µg/L.
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
----------------------------------------------------------------------------------------------------------------
Single analyst
Parameter Accuracy, as recovery, precision, sr[prime] Overall precision,
X[prime] (µg/L) (µg/L) S[prime] (µg/L)
----------------------------------------------------------------------------------------------------------------
Benzene............................... 0.93C+2.00 0.26X-1.74 0.25X-1.33
Bromodichloromethane.................. 1.03C-1.58 0.15X+0.59 0.20X+1.13
Bromoform............................. 1.18C-2.35 0.12X+0.36 0.17X+1.38
Bromomethane a........................ 1.00C 0.43X 0.58X
Carbon tetrachloride.................. 1.10C-1.68 0.12X+0.25 0.11X+0.37
Chlorobenzene......................... 0.98C+2.28 0.16X-0.09 0.26X-1.92
Chloroethane.......................... 1.18C+0.81 0.14X+2.78 0.29X+1.75
2-Chloroethylvinyl ether a............ 1.00C 0.62X 0.84X
Chloroform............................ 0.93C+0.33 0.16X+0.22 0.18X+0.16
Chloromethane......................... 1.03C+0.81 0.37X+2.14 0.58X+0.43
Dibromochloromethane.................. 1.01C-0.03 0.17X-0.18 0.17X+0.49
1,2-Dichlorobenzene b................. 0.94C+4.47 0.22X-1.45 0.30X-1.20
1,3-Dichlorobenzene................... 1.06C+1.68 0.14X-0.48 0.18X-0.82
1,4-Dichlorobenzene b................. 0.94C+4.47 0.22X-1.45 0.30X-1.20
1,1-Dichloroethane.................... 1.05C+0.36 0.13X-0.05 0.16X+0.47
1,2-Dichloroethane.................... 1.02C+0.45 0.17X-0.32 0.21X-0.38
1,1-Dichloroethene.................... 1.12C+0.61 0.17X+1.06 0.43X-0.22
trans-1,2,-Dichloroethene............. 1.05C+0.03 0.14X+0.09 0.19X+0.17
1,2-Dichloropropane a................. 1.00C 0.33X 0.45X
cis-1,3-Dichloropropene a............. 1.00C 0.38X 0.52X
trans-1,3-Dichloropropene a........... 1.00C 0.25X 0.34X
Ethyl benzene......................... 0.98C+2.48 0.14X+1.00 0.26X-1.72
Methylene chloride.................... 0.87C+1.88 0.15X+1.07 0.32X+4.00
1,1,2,2-Tetrachloroethane............. 0.93C+1.76 0.16X+0.69 0.20X+0.41
Tetrachloroethene..................... 1.06C+0.60 0.13X-0.18 0.16X-0.45
Toluene............................... 0.98C+2.03 0.15X-0.71 0.22X-1.71
1,1,1-Trichloroethane................. 1.06C+0.73 0.12X-0.15 0.21X-0.39
1,1,2-Trichloroethane................. 0.95C+1.71 0.14X+0.02 0.18X+0.00
Trichloroethene....................... 1.04C+2.27 0.13X+0.36 0.12X+0.59
Trichloroflouromethane................ 0.99C+0.39 0.33X-1.48 0.34X-0.39
Vinyl chloride........................ 1.00C 0.48X 0.65X
----------------------------------------------------------------------------------------------------------------
X[prime]=Expected recovery for one or more measurements of a sample containing a concentration of C, in µg/
L.
Sr=Expected single analyst standard deviation of measurements at an average concentration found ofX, in µg/
L.
S[prime]=Expected interlaboratory standard deviation of measurements at an average concentration found ofX, in
µg/L.
C=True value for the concentration, in µg/L.
X=Average recovery found for measurements of samples containing a concentration of C, in µg/L.
a Estimates based upon the performance in a single laboratory. 13
b Due to chromatographic resolution problems, performance statements for these isomers are based upon the sums
of their concentrations.




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Method 625—Base/Neutrals and Acids

1. Scope and Application

1.1 This method covers the determination of a number of organic compounds that are partitioned into an organic solvent and are amenable to gas chromatography. The parameters listed in Tables 1 and 2 may be qualitatively and quantitatively determined using this method.

1.2 The method may be extended to include the parameters listed in Table 3. Benzidine can be subject to oxidative losses during solvent concentration. Under the alkaline conditions of the extraction step, a–BHC, ?–BHC, endosulfan I and II, and endrin are subject to decomposition. Hexachlorocyclopentadiene is subject to thermal decomposition in the inlet of the gas chromatograph, chemical reaction in acetone solution, and photochemical decomposition. N-nitrosodimethylamine is difficult to separate from the solvent under the chromatographic conditions described. N-nitrosodiphenylamine decomposes in the gas chromatographic inlet and cannot be separated from diphenylamine. The preferred method for each of these parameters is listed in Table 3.

1.3 This is a gas chromatographic/mass spectrometry (GC/MS) method2,14 applicable to the determination of the compounds listed in Tables 1, 2, and 3 in municipal and industrial discharges as provided under 40 CFR 136.1.

1.4 The method detection limit (MDL, defined in Section 16.1) 1 for each parameter is listed in Tables 4 and 5. 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 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 use of 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 A measured volume of sample, approximately 1–L, is serially extracted with methylene chloride at a pH greater than 11 and again at a pH less than 2 using a separatory funnel or a continuous extractor. 2 The methylene chloride extract is dried, concentrated to a volume of 1 mL, and analyzed by GC/MS. Qualitative identification of the parameters in the extract is performed using the retention time and the relative abundance of three characteristic masses (m/z). Quantitative analysis is performed using internal standard techniques with a single characteristic m/z.

3. Interferences

3.1 Method interferences may be caused by contaminants in solvents, reagents, glassware, and other sample processing hardware that lead to discrete artifacts and/or elevated baselines in the total ion current profiles. All of these materials must be routinely demonstrated to be free from interferences under the conditions of the analysis by running laboratory reagent blanks as described in Section 8.1.3.

3.1.1 Glassware must be scrupulously cleaned.3 Clean all glassware as soon as possible after use by rinsing with the last solvent used in it. Solvent rinsing should be followed by detergent washing with hot water, and rinses with tap water and distilled water. The glassware should then be drained dry, and heated in a muffle furnace at 400 °C for 15 to 30 min. Some thermally stable materials, such as PCBs, may not be eliminated by this treatment. Solvent rinses with acetone and pesticide quality hexane may be substituted for the muffle furnace heating. Thmrough rinsing with such solvents usually eliminates PCB interference. Volumetric ware should not be heated in a muffle furnace. After drying and cooling, glassware should be sealed and stored in a clean environment to prevent any accumulation of dust or other contaminants. Store inverted or capped with aluminum foil.

3.1.2 The use of high purity reagents and solvents helps to minimize interference problems. Purification of solvents by distillation in all-glass systems may be required.

3.2 Matrix interferences may be caused by contaminants that are co-extracted from the sample. The extent of matrix interferences will vary considerably from source to source, depending upon the nature and diversity of the industrial complex or municipality being sampled.

3.3 The base-neutral extraction may cause significantly reduced recovery of phenol, 2-methylphenol, and 2,4-dimethylphenol. The analyst must recognize that results obtained under these conditions are minimum concentrations.

3.4 The packed gas chromatographic columns recommended for the basic fraction may not exhibit sufficient resolution for certain isomeric pairs including the following: anthracene and phenanthrene; chrysene and benzo(a)anthracene; and benzo(b)fluoranthene and benzo(k)fluoranthene. The gas chromatographic retention time and mass spectra for these pairs of compounds are not sufficiently different to make an unambiguous identification. Alternative techniques should be used to identify and quantify these specific compounds, such as Method 610.

3.5 In samples that contain an inordinate number of interferences, the use of chemical ionization (CI) mass spectrometry may make identification easier. Tables 6 and 7 give characteristic CI ions for most of the compounds covered by this method. The use of CI mass spectrometry to support electron ionization (EI) mass spectrometry is encouraged but not required.

4. Safety

4.1 The toxicity or carcinogenicity of each reagent used in this method have 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 identified4–6 for the information of the analyst.

4.2 The following parameters covered by this method have been tentatively classified as known or suspected, human or mammalian carcinogens: benzo(a)anthracene, benzidine, 3,3'-dichlorobenzidine, benzo(a)pyrene, a-BHC, ß-BHC, d-BHC, ?-BHC, dibenzo(a,h)anthracene, N-nitrosodimethylamine, 4,4'-DDT, and polychlorinated biphenyls (PCBs). 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 or composit sampling.

5.1.1 Grab sample bottle—1-L or 1-gt, amber glass, fitted with a screw cap lined with Teflon. Foil may be substituted for Teflon if the sample is not corrosive. If amber bottles are not available, protect samples from light. The bottle and cap liner must be washed, rinsed with acetone or methylene chloride, and dried before use to minimize contamination.

5.1.2 Automatic sampler (optional)—The sampler must incorporate glass sample containers for the collection of a minimum of 250 mL of sample. Sample containers must be kept refrigerated at 4 °C and protected from light during compositing. If the sampler uses a peristaltic pump, a minimum length of compressible silicone rubber tubing may be used. before use, however, the compressible tubing should be throughly rinsed with methanol, followed by repeated rinsings with distilled water to minimize the potential for contamination of the sample. An integrating flow meter is required to collect flow proportional composites.

5.2 Glassware (All specifications are suggested. Catalog numbers are included for illustration only.):

5.2.1 Separatory funnel—2–L, with Teflon stopcock.

5.2.2 Drying column—Chromatographic column, 19 mm ID, with coarse frit

5.2.3 Concentrator tube, Kuderna-Danish—10-mL, graduated (Kontes K–570050–1025 or equivalent). Calibration must be checked at the volumes employed in the test. Ground glass stopper is used to prevent evaporation of extracts.

5.2.4 Evaporative flask, Kuderna-Danish—500-mL (Kontes K–57001–0500 or equivalent). Attach to concentrator tube with springs.

5.2.5 Snyder column, Kuderna-Danish—Three all macro (Kontes K–503000–0121 or equivalent).

5.2.6 Snyder column, Kuderna-Danish—Two-ball macro (Kontes K–569001–0219 or equivalent).

5.2.7 Vials—10 to 15-mL, amber glass, with Teflon-lined screw cap.

5.2.8 Continuous liquid—liquid extractor—Equipped with Teflon or glass connecting joints and stopcocks requiring no lubrication. (Hershberg-Wolf Extractor, Ace Glass Company, Vineland, N.J., P/N 6841–10 or equivalent.)

5.3 Boiling chips—Approximately 10/40 mesh. Heat to 400 °C for 30 min of Soxhlet extract with methylene chloride.

5.4 Water bath—Heated, with concentric ring cover, capable of temperature control (±2°C). The bath should be used in a hood.

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

5.6 GC/MS system:

5.6.1 Gas Chromatograph—An analytical system complete with a temperature programmable gas chromatograph and all required accessores including syringes, analytical columns, and gases. The injection port must be designed for on-column injection when using packed columns and for splitless injection when using capillary columns.

5.6.2 Column for base/neutrals—1.8 m long × 2 mm ID glass, packed with 3% SP–2250 on Supelcoport (100/120 mesh) or equivalent. This column was used to develop the method performance statements in Section 16. Guidelines for the use of alternate column packings are provided in Section 13.1.

5.6.3 Column for acids—1.8 m long × 2 mm ID glass, packed with 1% SP–1240DA on Supelcoport (100/120 mesh) or equivalent. This column was used to develop the method performance statements in Section 16. Guidelines for the use of alternate column packings are given in Section 13.1.

5.6.4 Mass spectrometer—Capable of scanning from 35 to 450 amu every 7 s or less, utilizing a 70 V (nominal) electron energy in the electron impact ionization mode, and producing a mass spectrum which meets all the criteria in Table 9 when 50 ng of decafluorotriphenyl phosphine (DFTPP; bis(perfluorophenyl) phenyl phosphine) is injected through the GC inlet.

5.6.5 GC/MS interface—Any GC to MS interface that gives acceptable calibration points at 50 ng per injection for each of the parameters of interest and achieves all acceptable performance criteria (Section 12) 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.

5.6.6 Data system—A computer system must be interfaced to the mass spectrometer that allows the contiluous 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 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.

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.

6.2 Sodium hydroxide solution (10 N)—Dissolve 40 g of NaOH (ACS) in reagent water and dilute to 100 mL.

6.3 Sodium thiosulfate—(ACS) Granular.

6.4 Sulfuric acid (1+1)—Slowly, add 50 mL of H2SO4 (ACS, sp. gr. 1.84) to 50 mL of reagent water.

6.5 Acetone, methanol, methlylene chloride—Pesticide quality or equivalent.

6.6 Sodium sulfate—(ACS) Granular, anhydrous. Purify by heating at 400 °C for 4 h in a shallow tray.

6.7 Stock standard solutions (1.00 µg/µL)—standard solutions can be prepared from pure standard materials or purchased as certified solutions.

6.7.1 Prepare stock standard solutions by accurately weighing about 0.0100 g of pure material. Dissolve the material in pesticide quality acetone or other suitable solvent and dilute to volume in a 10-mL volumetric flask. Larger volumes can be used at the convenience of the analyst. 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.

6.7.2 Transfer the stock standard solutions into Teflon-sealed screw-cap bottles. Store at 4 °C and protect from light. Stock standard solutions should be checked frequently for signs of degradation or evaporation, especially just prior to preparing calibration standards from them.

6.7.3 Stock standard solutions must be replaced after six months, or sooner if comparison with quality control check samples indicate a problem.

6.8 Surrogate standard spiking solution—Select a minimum of three surrogate compounds from Table 8. Prepare a surrogate standard spiking solution containing each selected surrogate compound at a concentration of 100 µg/mL in acetone. Addition of 1.00 mL of this solution to 1000 mL of sample is equivalent to a concentration of 100 µg/L of each surrogate standard. Store the spiking solution at 4 °C in Teflon-sealed glass container. The solution should be checked frequently for stability. The solution must be replaced after six months, or sooner if comparison with quality control check standards indicates a problem.

6.9 DFTPP standard—Prepare a 25 µg/mL solution of DFTPP in acetone.

6.10 Quality control check sample concentrate—See Section 8.2.1.

7. Calibration

7.1 Establish gas chromatographic operating parameters equivalent to those indicated in Table 4 or 5.

7.2 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 standards is not affected by method or matrix interferences. Some recommended internal standards are listed in Table 8. Use the base peak m/z as the primary m/z for quantification of the standards. If interferences are noted, use one of the next two most intense m/z quantities for quantification. (continued)