Page:NIOSH Manual of Analytical Methods - 7903.pdf/6

 ACIDS, INORGANIC: METHOD 7903, Issue 2, dated 15 August 1994 - Page 6 of 6

APPENDIX: SAMPLING TUBE PREPARATION Silica gel cleaning procedure:	 Add 500 to 600 mL deionized water, slowly and with stirring, to ca. 200 mL volume of silica gel in 1-L beaker. When exothermal reaction has subsided, heat in boiling waterbath for ca. 30 min with occasional stirring. Decant and rinse four to five times with deionized water. Repeat cleaning procedure and dry overnight in 100 °C oven until free flowing. If blank of silica gel shows impurities upon analysis by ion chromatography, repeat cleaning procedure.

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Silica gel tubes: Pack glass tubes, 7-mm OD, 4.8-mm ID, 11 cm long, with 400 mg of 20/40 mesh washed silica gel in front section and 200 mg backup section. Use urethane foam plugs between sorbent sections and at back end. Hold front section in place with 6-mm diameter, 1-mm thick glass fiber filter plug (Gelman 66088).

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition