Page:NIOSH Manual of Analytical Methods - 2015.pdf/3

 CHLOROACETALDEHYDE: METHOD 2015, Issue 1, dated 15 August 1994 - Page 3 of 4

9.

10.

concentrations. b. Analyze together with samples and blanks (steps 11 through 13). c. Prepare calibration graph of µg chloroacetaldehyde/25 mL vs. peak area. Determine desorption efficiency (DE) at least once for each batch of silica gel used for sampling in the calibration range (step 8). Prepare three tubes at each of five concentrations plus three media blanks. a. Remove and discard the back sorbent section of a media blank sampler. b. Inject a known amount of standard ( ≤ 100 µL) directly onto front sorbent section with a microliter syringe. c. Cap the tube. Allow to stand overnight. d. Desorb (steps 5 through 7) and analyze together with working standards (steps 11 through 13). e. Prepare a graph of DE vs. µg chloroacetaldehyde recovered. Analyze three quality control blind spikes and five analyst spikes to ensure that the calibration graph and DE graph are in control.

MEASUREMENT: 11. 12. 13.

Set gas chromatograph according to manufacture's recommendations and to conditions given on page 2015-1. Inject 2-µL sample aliquot along with 3 µL of water as solvent flush. Measure peak area. NOTE: If peak area is above the linear range of the working standards, dilute an aliquot of the desorbed liquid, reanalyze, and apply the appropriate dilution factor in the calculations.

CALCULATIONS: 14.

15.

Determine the mass, µg (corrected for DE), of chloroacetaldehyde found in the sample front (W and back (W b) sorbent sections, and in the average media blank front (B f) and back (B b) sorbent sections. NOTE: If W b > W f/10, report breakthrough and possible sample loss. Calculate concentration, C, of chloroacetaldehyde in the air volume sampled, V (L):

EVALUATION OF METHOD: This method was evaluated over the range 1.8 to 6.4 mg/m 3 at 20 °C and 761 mm Hg using 3-L samples [1]. The concentration of chloroacetaldehyde in the test atmospheres was independently monitored using bubblers containing 15 mL deionized distilled water. Breakthrough from front sorbent sections occurred after sampling for 92 min at 0.2 L/min in an atmosphere containing 5.16 mg/m 3. The relative humidity was 80%. Samples collected at 1X the OSHA standard and stored at room temperature for 1 week lost 8.3% and 5.3% when the relative humidity was 20% and 80%, respectively. No correction for desorption efficiency was needed for loadings at 0.5-, 1-, and 2X the OSHA standard. Recoveries of samples collected at 80% RH had a positive bias of 3.4%, and samples collected at 20% RH had a negative bias of -4.2%. The overall mean bias was -0.4%.

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

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