National Institute for Occupational Safety and Health

“ 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 hexane, reanalyze, and apply the appropriate dilution factor in calculations. ”

“ Samples of methylal in dry air were generated using a three-neck round-bottom generator flask containing the liquid methylal. An accurately measured flow of nitrogen gas was used to sweep the vapors out of the flask. Overall precision, s r, was 0.060 with average recovery of 104%. Desorption efficiency was 78, 81, and 88%, respectively, at 3.1, 6.2, and 12.3 mg methylal taken per sample. Breakthrough (5% on back section) occurred at 20 min when sampling an atmosphere containing 6250 mg/m 3 methylal at 0.183 L/min at 0% RH. Breakthrough at high humidity was not tested, nor was sample stability. ”

“ Desorb (steps 5 through 7) and analyze together with working standards (steps 11 and 12) . e. Prepare a graph of DE vs. mg methylal recovered. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph and DE graph are in control. ”