Page:NIOSH Manual of Analytical Methods - 5003.pdf/2

 PARAQUAT: METHOD 5003, Issue 2, dated 15 August 1994 - Page 2 of 3 REAGENTS: 1. 2. 3. 4. 5.

6.

EQUIPMENT:

Water, deionized, distilled. Acetonitrile, HPLC grade. 1-Heptanesulfonic acid, sodium salt. Paraquat dichloride.* Dry at 50 °C to remove water of hydration. Calibration stock solution, 0.002 mg paraquat cation/µL.* Dissolve 27.6 mg anhydrous paraquat dichloride in distilled water to make 10 mL solution. Prepare in duplicate. LC mobile phase, 25% acetonitrile in 0.01 M aqueous 1-heptanesulfonic acid, sodium salt. Add glacial acetic acid to bring pH to 3.2 ± 0.3.



1. Sampler: 1-µm PTFE filter, 37-mm diameter with backup pad in a two-piece filter cassette held together with tape or shrink bands. 2. Personal sampling pump, 1 to 4 L/min, with flexible connecting tubing. 3. HPLC, UV absorption detector at 254 nm, integrator and column (page 5003-1). 4. Vials, 20-mL, scintillation. 5. Pipets, 5-mL. 6. Microliter pipets or syringe, 1- to 250-µL. 7. Syringe, 20-µL, or fixed sample loop or autosampler for injections. 8. Volumetric flasks, 10-mL.

See SPECIAL PRECAUTIONS.

SPECIAL PRECAUTIONS: Paraquat is listed as a severe poison. Use care in handling [4,5]. SAMPLING: 1. 2.

Calibrate each personal sampling pump with a representative sampler in line. Sample at an accurately known flow rate between 1 and 4 L/min for a total sample size of 40 to 1000 L. Do not exceed 2 mg total dust on filter.

SAMPLE PREPARATION: 3. 4.

Carefully transfer the filter from the cassette to a vial using tweezers. Add 5 mL deionized, distilled water to each vial. Cap the vial and gently swirl it to dissolve the sample completely.

CALIBRATION AND QUALITY CONTROL: 5.

6.

Calibrate daily with at least six working standards covering the range 10 to 500 µg paraquat per sample. a. Add calibration stock solution with a microliter syringe to 5 mL water in a vial. b. Analyze together with samples and blanks (steps 7 through 9). c. Prepare calibration graph (response vs. µg paraquat). Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph is in control.

MEASUREMENT: 7. 8. 9.

Set HPLC to conditions given on page 5003-1. Inject sample aliquot using a syringe, a fixed volume sample loop or an autosampler. Measure peak response. NOTE 1: Retention time under these conditions is ca. 6 to 6.5 min. NOTE 2: If peak response is above the range of the working standards, dilute with deionized, distilled water, reanalyze, and apply the appropriate dilution factors in calculations. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94