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 CARBON DIOXIDE: METHOD 6603, Issue 2, dated 15 August 1994 - Page 3 of 3 CALIBRATION AND QUALITY CONTROL: 4.

5.

Perform the following in the laboratory before field work begins: a. Establish a laboratory calibration graph with at least three replicate determinations of at least five working standards. Plot peak height vs. mass of carbon dioxide. 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 carbon dioxide peak from other substances known or predicted to be present in the field samples. Establish a daily field calibration graph (peak height vs. mass of carbon dioxide with 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 carbon dioxide in the sample by comparison of the sample peak height with the daily calibration graph (step 5). Determine the concentration, C, of carbon dioxide in the injected sample, V (mL): C = W/V (mg/m 3) NOTE: Some GCs will perform this calculation electronically.

EVALUATION OF METHOD: This method for carbon dioxide was evaluated in accordance with the criteria for validation described in Reference [3]. Evaluation was over the range 2270-10000 ppm using a Fisher-Hamilton Gas Partitioner Model 29 gas chromatograph with a thermal conductivity detector and a 5-mL gas sampling loop [1,2]. Recovery after storage of CO 2 at 5800 ppm for 7 days was 92.5% (Saran or Tedlar bags), and 99.5% (5-layer bags). Other GCs and columns other than the one used this evaluation are available for use for the determination of carbon dioxide.

REFERENCES: [1] [2] [3]

Documentation of the NIOSH Validation Tests, S249, U.S. Department of Health, Education, and Welfare Publ. (NIOSH) 77-185 (1977). NIOSH Manual of Analytical Methods, 2nd ed., Vol. 3, S249, U.S. Department of Health, Education, and Welfare (NIOSH) Publ. 77-157-C (1977). NIOSH Research Report - Development and Validation of Methods for Sampling and Analysis of Workplace Toxic Substances, U.S. Department of Health and Human Services, Publ. (NIOSH) 80-133 (1980).

METHOD WRITTEN BY: M. L. Woebkenberg, NIOSH/DPSE

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94