Page:NIOSH Manual of Analytical Methods - 3510.pdf/2

 MONOMETHYLHYDRAZINE: METHOD 3510, Issue 1, dated 15 August 1994 - Page 2 of 3 EQUIPMENT:

REAGENTS: 1. 2. 3.

4.

5. 6.

Methylhydrazine sulfate *, ACS reagent grade. Hydrochloric acid, ACS reagent grade. Collection medium, 0.1 M hydrochloric acid. To 300 mL of distilled water in a 1000-mL volumetric flask, add 8.6 mL of concentrated hydrochloric acid with caution. Mix and bring to volume with distilled water. Phosphomolybdic acid solution. Dissolve 15 g of phosphomolybdic acid in 500 mL distilled water, allow to stand one day, and filter before use through a fluted paper filter. Water, deionized and distilled. Calibration stock solution, 1 mg/mL. Weigh 100 mg of methylhydrazine sulfate in a 100-mL volumetric flask and fill to the mark with 0.1 M hydrochloric acid.

See Special Precautions

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

Sampler: 25-mL bubbler with 15 mL 0.1 M hydrochloric acid. Personal sampling pump, 1.5 L/min, with flexible polyethylene or PTFE tubing. Glass or non-reactive stopper for bubbler. Glass tube, 5 cm long by 6-mm I.D., loosely packed with glass wool. Spectrophotometer, set at 730 nm. Spectrophotometer cells, 5-cm. Test tube, large. Volumetric flasks, 25-mL, 100-mL, 500-mL, 1000-mL. Pipets, 10-, 15-, 25-, and 50-µL; 10- and 15mL glass, delivery, with pipet bulb. Graduated cylinders, glass, 10-mL, 25-mL. Water bath at 87 °C. Stopwatch. Thermometer, ca. 0-120 °C.

SPECIAL PRECAUTIONS: Monomethylhydrazine may be fatal if inhaled, swallowed or absorbed through skin contact [5,6]. Contact may cause burns to skin and eyes. Vapor may cause irritation to eyes, nose, throat, and skin. Handle with caution and use appropriate protective equipment.

SAMPLING: 1. 2. 3. 4. 5.

Calibrate each personal sampling pump with a representative sampler in line. Transfer 15 mL 0.1 M hydrochloric acid to a bubbler. Connect outlet arm of bubbler to the glass-wool-packed tube (to prevent splashover into the pump) and then to the sampling pump with the flexible tubing. Sample at an accurately known rate between 0.5 and 1.5 L/min for a total air sample of 3 to 20 L. Remove bubbler stem and rinse with 0.1 M hydrochloric acid into bubbler body. Seal bubbler with an inert stopper for shipment in a suitable container in order to prevent damage during transit.

SAMPLE PREPARATION: 6. 7. 8.

Transfer the liquid from the bubbler, quantitatively, to a 25-mL volumetric flask. Add 7.5 mL of phosphomolybdic acid solution and bring volume to 25 mL with 0.1 M hydrochloric acid. Transfer an aliquot of this solution to a large test tube and heat to 87 °C for 50 min. Place test tube under running tap water to cool before measurement.

CALIBRATION AND QUALITY CONTROL: 9.

Prepare working standards over the range of 10 to 100 µg/25 mL. a. Add aliquots (10, 25, 50 and 100 µL) of calibration stock solution to 15 mL of 0.1 M hydrochloric acid in 25-mL volumetric flasks. Prepare a reagent blank using only 15 mL of NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94