Page:NIOSH Manual of Analytical Methods - 6009.pdf/2

 MERCURY: METHOD 6009, Issue 2, dated 15 August 1994 - Page 2 of 5 REAGENTS: 1. 2. 3. 4. 5.

6.

7.

8.

EQUIPMENT:

Water, organics-free, deionized. Hydrochloric acid (HCl), conc. Nitric acid (HNO 3), conc. Mercuric oxide, reagent grade, dry. Calibration stock solution, Hg 2+, 1000 µg/mL. Commercially available or dissolve 1.0798 g of dry mercuric oxide (HgO) in 50 mL of 1:1 hydrochloric acid, then dilute to 1 L with deionized water. Intermediate mercury standard, 1 µg/mL. Place 0.1 mL 1000 µg/mL stock into a 100 mL volumetric containing 10 mL deionized water and 1 mL hydrochloric acid. Dilute to volume with deionized water. Prepare fresh daily. Stannous chloride, reagent grade, 10% in 1:1 HCl. Dissolve 20 g stannous chloride in 100 mL conc. HCl. Slowly add this solution to 100 mL deionized water and mix well. Prepare fresh daily. Nitric acid, 1% (w/v). Dilute 14 mL conc. HNO 3 to 1 L with deionized water.

1. Sampler: glass tube, 7 cm long, 6-mm OD, 4mm ID, flame sealed ends with plastic caps, containing one section of 200 mg Hopcalite held in place by glass wool plugs (SKC, Inc., Cat. #226-17-1A, or equivalent). NOTE: A 37-mm, cellulose ester membrane filter in a cassette preceding the sorbent may be used if particulate mercury is to be determined separately. 2. Personal sampling pump, 0.15 to 0.25 L/min, with flexible connecting tubing. 3. Atomic absorption spectrophotometer with cold vapor generation system (see Appendix) or cold vapor mercury analysis system.* 4. Strip chart recorder, or integrator. 5. Flasks, volumetric, 50-mL, and 100-mL. 6. Pipet, 5-mL, 20-mL, others as needed. 7. Micropipet, 10- to 1000-µL. 8. Bottles, biological oxygen demand (BOD), 300-mL.
 * See SPECIAL PRECAUTIONS

SPECIAL PRECAUTIONS: Mercury is readily absorbed by inhalation and contact with the skin. Operate the mercury system in a hood, or bubble vented mercury through a mercury scrubber.

SAMPLING: 1. 2. 3.

4.

Calibrate each personal sampling pump with a representative sampler in line. Break ends of sampler immediately prior to sampling. Attach sampler to pump with flexible tubing. Sample at an accurately known rate of 0.15 to 0.25 L/min for a total sample size between 2 and 100 L. NOTE: Include a minimum of three unopened sampling tubes from the same lot as the samples for use as media blanks. Cap sampler and pack securely for shipment.

SAMPLE PREPARATION: 5. 6.

7. 8. 9.

Place the Hopcalite sorbent and the front glass wool plug from each sampler in separate 50-mL volumetric flasks. Add 2.5 mL conc. HNO 3 followed by 2.5 mL conc. HCl. NOTE: The mercury must be in the oxidized state to avoid loss. For this reason, the nitric acid must be added first. Allow the sample to stand for 1 h or until the black Hopcalite sorbent is dissolved. The solution will turn dark brown and may contain undissolved material. Carefully dilute to 50 mL with deionized water. (Final solution is blue to blue-green). Using a volumetric pipet, transfer 20 mL of the sample to a BOD bottle containing 80 mL of deionized water. If the amount of mercury in the sample is expected to exceed the standards, a smaller aliquot may be taken, and the volume of acid adjusted accordingly. The final volume in NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94