Page:NIOSH Manual of Analytical Methods - 2010.pdf/2

 AMINES, ALIPHATIC: METHOD 2010, Issue 2, dated 15 August 1994 - Page 2 of 4 EQUIPMENT:

REAGENTS: 1. 2. 3.

4.

5. 6. 7.

Sulfuric acid, 0.1 M, in 10% (v/v) aqueous methanol (90% H 2O + 10% methanol).* Potassium hydroxide (KOH) solution, 0.3 M.* Amines, highest purity available.* NOTE: Dimethylamine is commercially available as a 40% aqueous solution (Aldrich Co. or equivalent). Calibration stock solution.* Dilute 1 mL of amine to 10 mL with deionized water. Check concentration by titrating with standard sulfuric acid. Hydrogen, prepurified. Nitrogen, purified. Air, compressed and filtered.



See SPECIAL PRECAUTIONS.

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). Silanized glass wool plug precedes front. Urethane foam plugs, separate and retain the back section. Tubes are commercially available. 2. Personal sampling pump, 0.01 to 1 L/min, with flexible connecting tubing. 3. Refrigerated, bagged ("Blue-Ice," or equivalent). 4. Gas chromatograph, FID, integrator, and column (page 2010-1). 5. Vials, glass, 2-mL, with PTFE-lined caps. 6. Ultrasonic bath. 7. Syringes, 20-µL, 10-µL, 1-µL. 8. Pipets, 0.5-, 1-, 2-, and 10-mL. 9. Volumetric flasks, 10-mL. 10.File. 11.Tweezers.

Calibrate each personal sampling pump with a representative sampler in line. Break the ends of the samplers immediately prior to sampling. Attach sampler to pump with flexible tubing. Sample at an accurately known flow rate between 0.01 and 1.0 L/min for a total sample size of 3 to 30 L. Cap the samplers and pack securely for shipment with bagged refrigerant.

SAMPLE PREPARATION: 5. 6. 7.

8.

Place the front and back sorbent sections of the sampler tube in separate vials. Add the glass wool plug to the front sorbent section vial. Discard the foam plugs. Add 1.0 mL 0.1 M H2SO 4 in aqueous methanol. Tightly cap the vial. Agitate the vials in ultrasonic water bath for 3 h. 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.

Calibrate daily with at least six working standards covering the range of interest. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94