TRICHLOROETHYLENE by portable GC: METHOD 3701, Issue 2, dated 15 August 1994 - Page 3 of 3
3.
(4) Within 4 hrs after completion of sampling, introduce an aliquot of the sample into the GC (as in step 2.a). Obtain the TCE peak height of the injected sample.
CALIBRATION AND QUALITY CONTROL: 4.
5.
Perform the following in the laboratory before field work begins: a. Establish a laboratory calibration graph by at least three replicate determinations of at least six working standards. Plot peak height vs. mass of TCE. b. Determine detector drift, averaged over the time period(s) expected to be used in the field. c. Determine the ability of the GC column to separate the TCE peak from other substances known or predicted to be present in the field samples. Establish a daily calibration graph (peak height vs. ng of TCE) by triplicate determinations of working standards under the same conditions as for samples (step 2.a). Alternate analyses of samples and working standards, if possible.
CALCULATIONS: 6.
Calculate mass, W (ng), of TCE in sample by comparison of peak height with daily calibration graph (step 5). Determine concentration, C, of TCE in the injected sample, V (mL):
NOTE: Some GCs perform this calculation electronically. EVALUATION OF METHOD: This method was evaluated using an AID Model 590 portable GC. Gas bags containing known amounts of TCE in air were used to establish the calibration graph. The response of the portable GC was then compared to the concentration obtained from analysis of replicate charcoal tube samples taken from the same bag. A six-inch strip chart recorder was used to obtain peak height data from the portable GC. A limitation in the use of this type of portable GC (e.g., packed column, room temperature isothermal) is the limited ability to separate the analyte from any interferences present. In the evaluation of this method, a six-foot DC 200 column was used. Its ability to separate the TCE peak from other contaminants was not evaluated. However, the use of this or any other packed column operated at room temperature to separate complex mixtures is severely limited. Therefore, the application of this method should be confined to relatively uncomplicated atmospheres.
REFERENCES: [1] [2]
NIOSH Manual of Analytical Methods, 3rd ed., V. 2, NMAM 1022. U.S. Department of Health and Human Services, Publ. (NIOSH) 84-100 (1984). NIOSH Current Intelligence Bulletin 2, Trichloroethylene, NIOSH (June 6, 1975), U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 78-127 (1979).
METHOD WRITTEN BY: J.C. Posner, Ph.D., NIOSH/DPSE
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
