Page:NIOSH Manual of Analytical Methods - 1603.pdf/2

 ACETIC ACID: METHOD 1603, Issue 2, dated 15 August 1994 - Page 2 of 4 REAGENTS: 1.

2. 3. 4.

5. 6. 7.

EQUIPMENT:

Formic acid, aqueous 88% to 95%, high-purity (<0.02% acetic acid).* NOTE: The acetic acid content varies from lot to lot of formic acid. Test each lot before use. Glacial acetic acid, reagent grade.* Propionic acid, reagent grade. Eluent: Formic acid, 88% to 95%, with 0.1% v/v propionic acid or other suitable internal standard. Nitrogen, purified. Hydrogen, prepurified. Air, filtered.



1. Sampler: glass tube with plastic caps, 7 cm long, 6-mm OD, 4-mm ID, flame-sealed ends, containing two sections of activated (600 °C) coconut shell charcoal (front = 100 mg; back = 50 mg) separated by a 2-mm urethane foam plug. A silylated glass wool plug precedes the front section and a 3-mm urethane foam plug follows the back section. Pressure drop across the tube at 1 L/min airflow must be less than 3.4 kPa. Tubes are commercially available. 2. Personal sampling pump, 0.01 to 1 L/min, with flexible connecting tubing. 3. Gas chromatograph, flame ionization detector, integrator and column (see page 1603-1). 4. Vials, 2-mL, PTFE-lined caps. 5. Syringes, 10-µL and other convenient sizes for preparing standards, readable to 0.1 µL. 6. Volumetric flasks, 10-mL.

See Special Precautions

SPECIAL PRECAUTIONS: Care should be taken to avoid skin contact with formic acid and/or acetic acid. These reagents may cause severe burns.

SAMPLING: 1. 2. 3. 4.

Calibrate each personal sampling pump with a representative sampler in line. Break the ends of the sampler immediately before sampling. Attach sampler to personal sampling pump with flexible tubing. Sample at an accurately known flow rate between 0.01 and 1 L/min for a total sample size of 20 to 300 L. Cap the samplers and pack securely for shipment.

SAMPLE PREPARATION: 5. 6. 7.

Place the front and back sorbent sections of the sampler tube in separate vials. Discard the glass wool and foam plugs. Add 1.0 mL eluent to each vial. Attach crimp cap to each vial. Allow to stand 60 min with occasional agitation.

CALIBRATION AND QUALITY CONTROL: 8.

Calibrate daily with at least six working standards over the range 0.01 to 10 mg acetic acid per sample. a. Add known amounts of acetic acid to eluent in 10-mL volumetric flasks and dilute to the mark. b. Analyze together with samples and blanks (steps 11 and 12). c. Prepare calibration graph (ratio of peak area of analyte to peak area of internal standard vs. mg acetic acid). NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94