Page:NIOSH Manual of Analytical Methods - 6002.pdf/4

 PHOSPHINE: METHOD 6002, Issue 2, dated 15 August 1994 - Page 4 of 4 CALCULATIONS: 19. Determine mass, µg (corrected for DE), of phosphine found in the sample front (W f) and back (Wb) sorbent sections, and in the average media blank front (B f) and back (Bb) sorbent sections. NOTE: If Wb>Wf/10, report breakthrough and possible sample loss. 20. Calculate concentration, C, of phosphine in the air volume sampled, V (L).

C

( Wf

Wb

Bf V

Bb )

, mg/m 3.

EVALUATION OF METHOD: 3 This method was validated over the range 0.195 to 0.877 mg/m at 19 C and 765.3 mm Hg using 16-L samples [1]. Desorption efficiency must be determined over the range used. The upper range of the method depends on the adsorptive capacity of the mercuric cyanide treated gel. This capacity may vary with the concentration of phosphine and other substances in the air. When an atmosphere at 90% relative humidity containing 0.957 mg/m3 of phosphine was sampled at a flow rate of 0.2 L/min, breakthrough was determined to occur at a sample volume of 20.75 liter (capacity = 19.86 µg PH 3).

REFERENCES: [1] [2] [3]

Backup Data Report for Phosphine, S332, prepared under NIOSH Contract No. 210-76-0123, March 17, 1978. NIOSH Manual of Analytical Methods, 2nd. ed., V. 5, S332, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 79-141 (1979). OSHA Analytical Methods Manual (USDOL/OSHA-SLCAL Method No. ID-80). Publ. No. (ISBN) 0-936712-66-X. American Conference of Governmental Industrial Hygienists, Cincinnati, OH.

METHOD REVISED BY: Charles Lorberau, NIOSH/DPSE.

APPENDIX: PREPARATION OF SAMPLING MEDIA Coating of Silica Gel 1. Dry 100 g of silica gel (45/60 mesh) at 90 C for 2 hours. 2. Prepare a 2% (w/v) mercuric cyanide solution in water (2 g Hg(CN) 2 in 100 mL water). 3. Add the dried silica gel to the mercuric cyanide solution and let set for 15 minutes with occasional stirring. 4. Drain the excess mercuric cyanide solution and dry the remaining silica gel at 90C for 3 hours. 5. Cool the silica gel to room temperature in a covered beaker. 6. Expose the silica gel to a humid atmosphere (>80% RH) for 24 hours. Preparing the sampling tubes 7. Place a plug of silylated glass wool at the end of a glass tube (6-mm O.D. and 4-mm I.D.) about 12 cm long. Pour 300 mg of the treated silica gel into the tube. Place another plug of silylated glass wool behind this front section. Add another 150 mg of the treated silica gel into the tube. Place a final plug of silylated glass wool behind this backup section. 8. Check the pressure drop of a representative sampler. The pressure drop across the tube must be less than 2 inches of mercury at a flow rate of 0.2 L/min. 9. Flame seal both ends of the sampling tubes.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition