Page:NIOSH Manual of Analytical Methods - 1300.pdf/3

 KETONES I: METHOD 1300, Issue 2, dated 15 August 1994 - Page 3 of 5

10.

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 1300-1. 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 CS 2, reanalyze, and apply the appropriate dilution factor in calculations. Measure peak area.

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: The methods on which this method was based were validated under NIOSH Contract CDC-99-74-45 [5]. Desorption efficiency was checked by spiking known amounts of the compounds (either neat or in solutions with CS 2) on coconut shell charcoal. Samples were generated for acetone, cyclohexanone, 2-pentanone, and methyl isobutyl ketone by heating a quantity of the liquid to just below its boiling point in a 3-necked, 500-mL round bottom flask. The compound was carried through a fixed-temperature condenser to the concentrations. Samples were generated for diisobutyl ketone and 2-hexanone using a syringe pump which delivered the compounds to a heated glass-lined inlet which was swept with nitrogen, carrying the vapor to the mixing chamber. Low-level desorption efficiency checks showed the DEs to be 70% and 76% for 0.024 and 0.096 mg/sample respectively for cyclohexanone and 87% for 0.052 mg/sample of MIBK [2]. Results of the evaluation experiments are given below.

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