Page:NIOSH Manual of Analytical Methods - 2536.pdf/5

 VALERALDEHYDE: METHOD 2536, Issue 2, dated 15 August 1994 - Page 5 of 5 APPENDIX B: SORBENT PREPARATION (optional if commercially-prepared tubes are used): Add 1 g purified 2-(hydroxymethyl)piperidine in 50 mL toluene for each 9 g extracted XAD-2 sorbent. Allow this mixture to stand 1 h with occasional swirling. Remove the solvent by rotary evaporation at 37 °C. Dry at 130 Pa (1 mm Hg) at ambient temperature for approximately 1 h. To determine the amount of background for each batch, desorb several 120-mg portions of the coated sorbent with toluene and analyze (steps 7 through 13). No blank peak is expected for valeraldehyde. APPENDIX C: DESORPTION EFFICIENCY: The determination of desorption efficiency (DE) is not necessary when using the calibration procedure in step 10, although the DE should be determined once for each lot of sorbent used, using the following procedure: a. Prepare and analyze a set of valeraldehyde oxazolidine standard solutions (step 9.a) and a set of working standards (step 10), including media blanks. b. Treating the working standards as unknowns, read the mass (µg) of valeraldehyde oxazolidine found in each working standard (W), and in the average media blank (B). c. Using the mass of valeraldehyde, µg, spiked onto the working standard (W o) and the stoichiometric conversion factor of 2.13 between valeraldehyde and valeraldehyde oxazolidine, calculate the desorption efficiency:

d.

Prepare a graph of DE vs. µg valeraldehyde recovered per sample, (W - B)/2.13.

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