Page:NIOSH Manual of Analytical Methods - 1400.pdf/3

 ALCOHOLS I: METHOD 1400, Issue 2, dated 15 August 1994 - Page 3 of 4

10.

a. Remove and discard back sorbent section of a media blank sampler. b. Inject a known amount of analyte 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 and 12). e. Prepare a graph of DE vs. mg analyte recovered. Analyze three quality control blind spikes and three analyst spikes to insure that the calibration graph and DE graph are in control.

MEASUREMENT: 11.

12.

Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 1400-1. Inject sample aliquot manually using solvent flush technique or with autosampler. NOTE: If peak area is above the linear range of the working standards, dilute with eluent, reanalyze and apply the appropriate dilution factor in calculations. Measure peak area. Divide the peak area of analyte by the peak area of internal standard on the same chromatogram.

CALCULATIONS: 13.

14.

Determine the mass, mg (corrected for DE) of analyte found in the sample front (W f) 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 analyte in the air volume sampled, V (L):

EVALUATION OF METHOD: Methods S56, S65 and S63 were issued on January 17, 1975 [3], and validated using 1-, 3- and 10-L air samples, respectively, of atmospheres generated in dry air by calibrated syringe drive from absolute ethanol, 2-propanol and t-butyl alcohol [1]. No stability studies were done. Overall precision and recovery were as shown below, representing non-significant bias in each method: Overall Precision Method (SˆrT) S56 S65 S63

0.065 0.064 0.075

Recovery (%) 103.6 96.7 100.3

Range Studied mg/m 3 mg per sample 900 to 3300 505 to 1890 165 to 600

1 to 4 1 to 5 1.5 to 6

Breakthrough @ 2X OSHA 1.6 L 6.0 L 17.0 L


 * Over the range studied. Each laboratory must do their own DE determinations.

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

Avg. DE 0.79* 0.93* 0.91*

Measurement Precision (Sr) 0.027 0.033 0.018