National Institute for Occupational Safety and Health

“ Prepare calibration graph (ratio of peak area of nitroethane to peak area of internal standard vs. μg nitroethane) . Determine desorption efficiency (DE) at least once for each lot of sorbent used for sampling in the range of interest. Prepare three tubes at each of five levels plus three media blanks. a. Inject a known amount (2 to 20 μL) of calibration stock solution, or a serial dilution thereof, directly onto front sorbent section (600 mg sorbent) with a microliter syringe. b. Cap the tube. Allow to stand overnight. ”

“ There were no statistically significant differences in the recoveries of 3-L samples collected from synthetic atmospheres containing 314 mg/m 3 nitroethane in humid air and stored for one or seven days at ambient temperatures prior to analysis. It was found necessary to separate the front and back sorbent sections immediately after sampling due to analyte migration during storage. Desorption efficiency averaged 0.88 in the range 0.47 to 1.9 mg per sample. A previous study found nitroethane to be unstable on activated charcoal [5] . ”

“ Sample at an accurately known flow rate between 0.01 and 0.05 L/min for a total sample size of 1.5 to 3 L. NOTE: High pressure drop across the sampler may occur at flow rates above 0.05 L/min, giving inaccurate sample volumes. ”