National Institute for Occupational Safety and Health

“ The difference between the "found" and "true" concentrations may not represent a bias in the sampling and analytical method, but rather a random variation from the experimentally determined "true" concentration. Therefore, the method has no uncorrected bias. Storage stability studies on samples collected in a test atmosphere at a concentration of 5.80 mg/m 3 indicated that collected samples are stable for at least 7 days at 8 °C. Collection efficiency for the midget bubbler was determined to be 0.96 for an average of 24 samples and a correction must be applied. ”

“ Glass midget bubblers. Personal sampling pump, 0.1 to 0.2 L/min, and trap with flexible tubing. Trap is a midget bubbler or impinger with stem broke off. Volumetric flasks, 1-L, 500-mL, and convenient sizes for preparing stock standard solutions. Pipets, 10-mL, 5-mL, and other convenient sizes. Syringes for preparing spiked standard samples. Potentiostat with differential pulse polarographic capability. China marker. PTFE tubing 15 cm x 7-mm ID or PTFE plugs for sealing the inlet and outlet of the bubbler stem before shipment. ”

“ Add 5 mL formate buffer solution and swirl bubbler to mix contents well.
CALIBRATION AND QUALITY CONTROL: 9.
10.
Prepare at least six working standards having concentrations to cover the range of 6 to 280 μg per sample (corresponding to 0.1 to 4 times the OSHA standard) . a. Add appropriate aliquots ( ≤ 100 μL) of stock solution to 10 mL of hydroxylamine solution, followed by addition of 5 mL of formate buffer solution. b. Analyze with samples and blanks (step 11) . c. Prepare calibration graph of peak current vs. mass (μg) of crotonaldehyde per 15 mL of sample. ”