National Institute for Occupational Safety and Health

“ Prepare a calibration graph (peak area or peak height vs. mg of amine per sample) . Determine desorption (DE) at least once for each lot of silica gel used for sampling in the concentration range of interest. Prepare four tubes at each of five levels plus media blanks. a. Measure the amount of silica gel used in the front sorbent section into a vial. b. Inject a known amount (1 to 20 μL) of calibration stock solution, or a dilution there of directly onto the silica gel. c. Cap vial. Allow to stand overnight. ”

“ NOTE: The water in the ultrasonic bath can get hot (ca. 50-60 °C) during the desorption period. Therefore, all vials must be tightly capped to minimize evaporation losses. Neutralize the sample solution as follows: let silica gel particles settle for a few minutes. Transfer a 500-μL aliquot of the supernatant liquid to a clean vial. Add 500 μL 0.3 M KOH. (The pH of the solution should be greater than 10) . Analyze the solutions immediately (steps 12 through 14) . NOTE: Ensure that no silica gel is present when adding KOH to prevent loss of analyte [1] .
CALIBRATION AND QUALITY CONTROL: 9. ”

“ SPECIAL PRECAUTIONS: The amines are highly flammable and have strong ammoniacal odors. They can cause severe eye damage and can easily be absorbed through the skin [8] . Sulfuric acid is highly corrosive, and potassium hydroxide is caustic. All work with these compounds should be performed in a hood. Use proper protective clothing including gloves, safety glasses, and laboratory coat.
SAMPLING: 1. 2.
3.
4.
1. Sampler: glass tube flame-sealed ends, with plastic caps, 7 cm x 6-mm OD x 4-mm ID, containing two sections of 20/40 mesh silica gel (front = 150 mg; back = 75 mg) . ”