Page:NIOSH Manual of Analytical Methods - 2011.pdf/2

 FORMIC ACID: METHOD 2011, Issue 1, dated 15 August 1994 - Page 2 of 4 EQUIPMENT:

REAGENTS: 1. 2. 3.

4. 5.

6. 7. 8.

Acetone, ACS reagent grade. Water, deionized. Eluent: 2.5 m M Na 2B4O 7 · 10 H 2O. Dissolve 3.82 g Na 2B4O 7 · 10 H 2O in 4 liters high purity water. Filter if necessary to remove any particulate matter. Suppressor regenerant, 25 m N H2SO 4.* Calibration stock solution, 1 mg formate anion per mL. Dissolve 0.1511 g sodium formate (dried @ 110 °C for 4 h, stored in desiccator) in 100 mL deionized water. Formic acid, 88% or 95% (Optional; see Appendix A). Dioxane (Optional; see Appendix A). 0.1 M Na 2B4O 7 · 10 H 2O. Dissolve 145 g Na 2B4O 7 · 10 H 2O in 4 liters deionized water. Filter if necessary to remove particles > 1 µm.



See SPECIAL PRECAUTIONS.

1. Sampler: glass tube, 10 cm long, 7-mm OD, 4-mm ID, flamed-sealed ends with plastic 20/40 caps, containing 20/40 mesh washed silica gel (front = 400 mg, back = 200 mg) separated by a 4-mm urethane foam plug. A thick glass fiber filter plug precedes the front section and a 5-mm urethane foam plug follows the back section. Tubes are commercially available (ORBO-53, Supelco, or equivalent) or prepare according to APPENDIX B. Prefilter, PTFE, 25-mm, with porous plastic support pad. Pressure drop across the sampler at 1 L/min airflow must be less than 3.4 kPa. 2. Personal sampling pump, 0.05 to 0.2 L/min, with flexible polyethylene or PTFE tubing. 3. Ion chromatograph, with a conductivity detector, chart recorder, integrator, and column. 4. Vials, polyethylene, 20-mL, with plastic caps. 5. Micropipettes, with disposable plastic tips. 6. Volumetric flasks, 100-mL. 7. Pipet, 10-mL, graduated in 0.1-mL intervals. 8. Pipet, volumetric, 20-mL. 9. Syringes, 10-mL, plastic, with luer tip. 10. Filters, luer tip, with membrane filter, 13-mm, 0.45-µm pore size.

SPECIAL PRECAUTIONS: Users of this method should be acquainted with the degree of hazard of each chemical and take the proper precautions. Handle all hazardous chemicals in a fume hood.

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 a sampler to personal sampling pump with flexible tubing. Sample at an accurately known flow rate between 0.05 and 0.2 L/min for total volume of 1 to 24 L. Cap the tubes with plastic (not rubber) caps, plug filter cassettes, and pack securely for shipment. NOTE: Prefilters may be analyzed for particulate formates, or may be discarded.

SAMPLE PREPARATION: 5.

6. 7. 8.

Place the front with glass fiber filter plug and back sorbent sections of the sampler tube (and prefilter, optional) in separate 20-mL plastic vials. A glass rod may be used to push the contents out of the tube. Discard the foam plugs. Add 10 mL deionized water to each plastic vial. Loosely cap. Heat in boiling water for 10 min, cool, and analyze the same day the formic acid is desorbed. Transfer a portion of sample to a syringe fitted with an inline membrane filter, for direct injection or for transfer to autosampler vials. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94