Page:NIOSH Manual of Analytical Methods - 1404.pdf/3

 METHYLCYCLOHEXANOL: METHOD 1404, Issue 1, dated 15 August 1994 - Page 3 of 3 a. b.

10.

Remove and discard back sorbent section of a media blank sampler. Inject a known amount (2 to 20 µL) of a 50:50 mixture of methylcyclohexanol isomers 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 with working standards (steps 11 and 12) e. Prepare a graph of DE vs. mg methylcyclohexanol recovered. Analyze three quality control blind spikes and three analyst spikes to ensure 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 1404-1. 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 an aliquot of the desorbed liquid with methylene chloride, reanalyze and apply the appropriate dilution factor in calculations. Measure peak area.

CALCULATIONS: 13.

14.

Determine the mass, mg (corrected for DE), of methylcyclohexanol 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 methylcyclohexanol in the air volume sampled, V (L):

EVALUATION OF METHOD: This method was evaluated over the range 215 to 920 mg/m 3 and had an overall sampling and measurement precision, SˆrT, of 0.063. Concentrations obtained for seventeen generated samples averaged 2.9% higher than the independently determined concentration. Average recoveries of 2.71 mg of meta- and para- isomers of methylcyclohexanol was determined at 942 mg/m 3 while sampling 0.19 L/min. Breakthrough occurred in 116 min corresponding to a capacity of 20.8 mg per sample. Sample stability during storage was evaluated at 5.45 mg per sample. Samples showed 99.8% recovery after eight days of storage at ambient conditions compared to one-day old samples.

REFERENCES: [1] [2] [3]

Backup Data Report for Methylcyclohexanol, prepared under NIOSH Contract 210-76-0123 (1977). NIOSH Manual of Analytical Methods, 2nd. ed., V. 4, S374, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 78-175 (1978). NIOSH Pocket Guide to Chemical Hazards, U.S. Department of Health and Human Services, Publ. (NIOSH) 90-117 (1990), available as GPO Stock #1990-751-238 from Superintendent of Documents, Washington, DC 20402.

METHOD REVISED BY: M.J. Seymour, NIOSH/DPSE, originally evaluated under NIOSH Contract 210-76--123 (1977). NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94