Page:NIOSH Manual of Analytical Methods - 6013.pdf/2

 HYDROGEN SULFIDE: METHOD 6013, Issue 1, dated 15 August 1994 - Page 2 of 4 REAGENTS:

EQUIPMENT:

1. Ammonium hydroxide solution, 25%. 2. Hydrogen peroxide, 30%.* 3. Sodium hydroxide, 50% (w/v).* 4. Extraction soln: 0.2 M NH 4OH. 5. Eluent: 40 m M NaOH. Dilute 4.16 mL of 50% NaOH to 2 L with deionized water (degassed). 6. Suppressor regenerant: 0.025 N H2SO 4. Dilute 1.4 mL concentrated H 2SO 4 to 2 L with deionized water.* 7. Calibration Stock solution: 1 mg/mL (as anion). Dissolve 0.1814 g K 2SO 4 in 100 mL deionized water. 8. H2S, calibration gas mixture, or permeation device.
 * See Special Precautions

1. Sampler: glass tube, 10 cm long, 8-mm OD, 6-mm ID, flame-sealed ends with plastic caps, containing 20/40 mesh activated (600 °C) coconut shell charcoal (front = 400 mg, back = 200 mg) separated by a 6-mm urethane foam plug. A silanized glass wool plug precedes the front section and a 6-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. Zefluor PTFE prefilter, 0.45-µm, 25-mm, with porous plastic support pad in 25-mm cassette. NOTE: Some lots of charcoal have excessively high sulfur backgrounds, and/or desorption efficiencies. Screen each lot before field use. 2. Personal sampling pump, 0.1 to 1.5 L/min, with flexible connecting tubing. 3. Ion chromatograph, conductivity detector, integrator and columns (page 6013-1). 4. Centrifuge tubes, 15-mL, plastic with screw caps. 5. Syringes, 10-mL, polyethylene with luer tip. 6. Syringe filters, 13-mm, 0.45-µm pore size. 7. Vials, autosampler, 4-mL, PTFE-lined caps. 8. Micropipettes, disposable tips. 9. Pipettes, 2-, 3-, 5-mL. 10. Volumetric flasks, 10-, 25-mL. 11. Vortex mixer (optional).

SPECIAL PRECAUTIONS: Hydrogen peroxide is a strong oxidizer causing burns to skin and mucous membranes. Sulfuric acid and sodium hydroxide are extremely corrosive to all body tissue. Wear protective clothing and eye protection. All work should be performed in a fume hood. SAMPLING: 1. 2.

Calibrate each personal sampling pump with a representative sampler in line. Break the ends of the sampler and attach prefilter with a small piece of flexible tubing immediately before sampling. Attach sampler to personal sampling pump with flexible tubing. 3. Sample at an accurately known flow rate between 0.1 and 1.5 L/min for a total sample size of 15 to 40 L. 4. Cap the sorbent tubes with plastic caps and plug prefilter cassettes. Pack securely for shipment. NOTE: The prefilters may be discarded or analyzed for particulate sulfates by, e.g., Method 6004.

SAMPLE PREPARATION: 5. 6. 7.

Place the front and back sorbent sections of the sampler tube in separate screw-top centrifuge tubes. Discard the glass wool and foam plugs. Add 2.0 mL of 0.2 M NH 4OH and 5.0 mL H 2O 2 to each centrifuge tube. Attach screw cap and loosen 1/4 turn. Allow to react at least 10 min. Tighten cap and shake for 30 s or vortex 10 s. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94