Page:NIOSH Manual of Analytical Methods - 2529.pdf/3

FURFURAL: METHOD 2529, Issue 2, dated 15 August 1994 - Page 3 of 4 6. 7. 8.

Transfer front section with remaining glass wool plugs to a second vial. Add 2.0 mL toluene to each vial. Screw cap tightly onto each vial. Agitate vials in an ultrasonic bath for 30 min.

CALIBRATION AND QUALITY CONTROL: 9.

10.

11.

Prepare oxazolidine standard solutions. a. Add known amounts of furfural oxazolidine stock solution (equivalent to the range of the samples) to toluene in 10-mL volumetric flasks and dilute to the mark. b. Analyze (steps 12 and 13) with samples and blanks for qualitative identification of derivative peaks. Calibrate daily with at least six working standards covering the range of the samples. a. Weigh 120-mg portions of unused sorbent into vials. b. Add aliquots of calibration stock solution or dilutions thereof. Cap vials and allow them to stand overnight at room temperature. c. Desorb (steps 7 and 8) and analyze (steps 12 and 13) with samples and blanks. d. Prepare calibration graph (peak area vs. µg furfural). NOTE: Because the working standards are prepared on media blanks, no additional blank correction or desorption efficiency correction is necessary. Analyze three quality control blind spikes to ensure that the calibration graph is in control.

MEASUREMENT: 12.

13.

Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 2529-1. Inject 1-µL sample aliquot. NOTE: If the amount of oxazolidine in the aliquot exceeds the capacity of the column, dilute the sample with toluene and apply the appropriate dilution factor in calculations. Measure total peak area of the two analyte peaks. NOTE: On the DB-5 column, the oxazolidine derivative of furfural gives two peaks, since the diastereoisomers are resolved. t r for the furfural derivative = 5.0 and 5.3 min; glutaraldehyde derivative = 9.4 and 9.7 min; and t r for 2-(hydroxymethyl)piperidine = 2.6 min for these conditions.

CALCULATIONS: 14.

15.

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

EVALUATION OF METHOD: Atmospheres were generated by flash vaporization of an aqueous furfural solution into a stream of air flowing at a fixed rate [1]. Relative humidity during generation was 80% ±5%. The generator and sampling manifold system have been described previously [5]. Concentration of furfural vapor was independently verified by the 2,4-dinitrophenylhydrazine procedure of Lipari and Swarin [6]. The method was studied over the range of 2.6 to 40 mg/m 3 using 15-L samples. Desorption efficiencies on statically-spiked samples averaged 94% in the range 16 to 640 -µg per sample. Recovery of dynamically-generated samples was 93%, owing to breakthrough of furfural at the highest level studied (40 mg/m 3). Recovery was quantitative at lower levels. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94