Page:NIOSH Manual of Analytical Methods - 1401.pdf/3

 ALCOHOLS II: METHOD 1401, Issue 2, dated 15 August 1994 - Page 3 of 4

10.

b. Inject a known amount of DE stock solution 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 1401-1. 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 (Wb) sorbent sections, and in the average media blank front (B f) and back (Bb) sorbent sections. NOTE: If Wb > Wf/10, report breakthrough and possible sample loss. Calculate concentration, C, of analyte in the air volume sampled, V (L):

EVALUATION OF METHOD: Methods S66 (n-butyl alcohol), S53 (sec-butyl alcohol), S64 (isobutyl alcohol), and S62 (n-propyl alcohol) were issued on January 17, 1975, and validated using 10-L air samples of atmospheres generated by injection of the pure alcohol into dry air using a calibrated syringe drive [1]. No stability studies were done. Overall precision and recovery were as shown below, representing non-significant bias in each method:

Method S66 S53 S64 S62

Overall Precision ˆ rT) (S

Recovery (%)

0.065 0.066 0.073 0.075

100.0 107.2 100.0 103.5

Range Studied mg/m3 mg per sample 170 270 180 225

to to to to

610 850 620 835

1.5 2.2 1.5 2.5

to to to to

6 9 6 10

Breakthrough @ 2X OSHA Avg. in Dry Air DE 35 15 31 19

L L L L

0.89 0.92 0.85 0.89

Measurement Precision (Sr) 0.021 0.028 0.023 0.016

REFERENCES: [1] [2]

Documentation of the NIOSH Validation Tests, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-185 (1977). User check, UBTL, NIOSH Sequence #3990-X (unpublished, November 3, 1983). NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94