NITROSAMINES: METHOD 2522, Issue 2, dated 15 August 1994 - Page 3 of 4 16.
17.
18.
Calibrate daily with at least six working standards over the range of 0.05 to 0.5 µg of analyte per sample (0.025 to 0.25 µg/mL). a. 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. c. Desorb (steps 12 through 15) and analyze together with working standards (steps 19 through 22). d. Prepare a graph of DE vs. µg analyte recovered. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph and DE graph are in control.
MEASUREMENT: 19. 20. 21.
Set gas chromatograph and TEA to the conditions listed on page 2522-1. Inject sample aliquot manually, using solvent flush technique or with an autosampler. Approximate retention times of the seven nitrosamines at indicated column temperatures are: COMPOUND N-nitrosodimethylamine N-nitrosodiethylamine N-nitrosodipropylamine N-nitrosodibutylamine N-nitrosomorpholine N-nitrosopiperidine N-nitrosopyrrolidine
22.
COLUMN TEMP. °C 120 125 142 145 178 169 166
RETENTION TIME (MIN) 2.2 3.1 6.2 7.4 13.2 12.0 11.2
Measure peak area.
CALCULATIONS: 23. 24.
Determine the mass, µg (corrected for DE) of analyte found in the sample (W) and blank (B). Calculate concentration, C, analyte in the air volume sampled, V (L):
EVALUATION OF METHOD: 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). Some field samples were also used for evaluation of this method [2]. REFERENCES:
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
