FORMALDEHYDE: METHOD 2541, Issue 2, dated 15 August 1994 - Page 3 of 5
7. 8.
9.
in a vial. Transfer back section with remaining glass wool plugs to a second vial. Add 1.0 mL toluene to each vial. Crimp cap tightly onto each vial. NOTE: An appropriate internal standard, such as 1 µL/mL dimethylformamide, may be added at this point [3]. Agitate vials in an ultrasonic water bath for 60 min.
CALIBRATION AND QUALITY CONTROL: 10.
11.
Calibrate daily with at least six working standards, in duplicate, covering the range of interest. a. Weigh ten 120-mg portions of the coated sorbent into 4-mL vials with septum caps. If the bulk coated sorbent is not available, remove the front section from ten unused samplers (media blanks). b. Inject aliquots of formaldehyde stock solution into the vials at six different levels and allow to sit overnight at room temperature. Use serial dilutions of the calibration stock solutions to spike the absorbent in the range of interest. c. Desorb (steps 7 through 9) and analyze (steps 12 and 13) with samples and blanks. d. Prepare calibration graph (peak area or peak height) vs. µg of formaldehyde. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph is in control.
MEASUREMENT: 12.
13.
Set gas chromatograph to manufacturer's recommendations and to conditions given on page 2541-1. 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, reanalyze, and apply the appropriate correction factor in calculations. Measure peak area or peak height. For formaldehyde derivative t r = 6.4 min and for 2(hydroxymethyl)piperidine t r = 9.4 min under these conditions. NOTE: If necessary, verify the identity of the formaldehyde oxazolidine by comparison of retention time with an authentic sample (see APPENDIX C).
CALCULATIONS: 14.
15.
Determine the mass, µg (corrected for DE) of oxazolidine derivative found in the sample front (W f) and back (W b) sorbent sections from the calibration graph. NOTE: if W b > W f/10, report breakthrough and possible sample loss. Calculate concentration, C (mg/m 3), of formaldehyde in the air volume sampled, V (L):
NOTE: Because the working standards are prepared on media blanks, no additional blank correction is necessary. Report field blanks as samples.
EVALUATION OF METHOD: This method is similar to OSHA Method 52 [2]; however, the OSHA samplers contained 20% more coated sorbent than the samplers used in this method. In a study by OSHA, 5% breakthrough occurred after 396 min at a flow rate of 0.1 L/min and a test atmosphere concentration of 5.3 mg/m 3. The relative NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
