National Institute for Occupational Safety and Health

“ The method was evaluated over the range 0.05 to 0.5 μg of the seven nitrosamines per sample. Desorption efficiency was checked by spiking known amounts of the compounds on Thermosorb/N tubes and was found to be nearly 100% for all nitrosamines studied. The sampling device is small and interferences are minimal; large concentrations can be sampled (up to 1500 μg loading) with no breakthrough. Samples can be stored at room temperature for long periods of time ( ≥6 weeks) . ”

“ Add known amounts of the nitrosamines standard solution to eluent in 10-mL volumetric flasks and dilute to mark. b. Analyze together with samples and blanks (steps 19-22) . c. Prepare calibration graph (peak area of analyte vs. μg analyte) . Determine desorption efficiency (DE) at least once for each batch of Thermosorb/N tubes used. a. Inject a known amount of nitrosamine standard solution directly onto the Thermosorb/N tube with a microliter syringe. b. Cap the tube. Allow to stand overnight. ”

“ APPLICABILITY: The working range is 0.003 to 10 mg/m 3 for a 50-L air sample. If high ambient concentrations of nitrosamines are expected, another Thermosorb/N tube should be used as a back-up in sampling. ”