Page:NIOSH Manual of Analytical Methods - 2506.pdf/4

 ACETONE CYANOHYDRIN: METHOD 2506, Issue 2, dated 15 August 1994 - Page 4 of 5

REFERENCES: [1]	 Glaser, R. and P. Fey. Development of a Quantitative Sampling and Analytical Method for Acetone Cyanohydrin in Air (1981), available as Order No. PB 83-139-444 from NTIS, Springfield, VA 22161. [2]	 NIOSH Manual of Analytical Methods, 2nd. ed., V. 7, P&CAM 340, U.S. Department of Health and Human Services, Publ. (NIOSH) 81-141 (1981). [3]	 Criteria for a Recommended Standard...Occupational Exposure to Nitriles, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 78-212 (1978). METHOD WRITTEN BY: Robert Glaser, NIOSH/DPSE. APPENDIX: COLUMN PREPARATION AND GC MODIFICATION 1. Stationary phase preparation: Weigh 10 g Chromosorb T into a glass Petri dish or small bowl. Dissolve 0.5 g OV-17 in 50 mL acetone; pour this solution over the Chromosorb T. Using a small spatula, slowly stir the stationary phase into the solution while evaporating the solvent away under a stream of nitrogen. Avoid crushing the soft Chromosorb T. A portion of the coated Chromosorb T will adhere to the glass; do not attempt to recover this material. Continue to stir the support into the solution until the solvent has completely evaporated. After the solvent has evaporated, allow the coated Chromosorb T to dry completely under the nitrogen stream. Refrigerate the coated Chromosorb T at 0 °C until it is packed into the GC column. 2. Column preparation, GC modification: Although the column dimensions are 2 m long × 3.2-mm OD, a longer piece of PTFE tubing (2.3 m) should be used in order to allow fitting to the chromatograph. Measure the length of the injector zone from the injector port to the point of column attachment in the oven. Push a plug of silanized glass wool this distance (about 10 to 20 cm) into the front (injector) end of the column. Add the packing material from the other end of the column under vacuum to a point about 1 cm before the detector end of the column. A 2-m column requires ca. 5 g of packing material. Seal the detector end of the column with a 0.5-cm plug of silanized glass wool. If it is necessary to replace transfer lines (see below), do not fill the column completely; leave about 1 cm open at the detector end after insertion of the glass wool. Use plastic (nylon, PTFE, etc.) compression fittings to connect the column to the instrument. Slide the injection port compression fittings onto the column directly over the silanized glass wool plug. Remove the septum retainer fitting, the septum, and the injector liner from the GC injection port. Push the empty end of the column through the oven side of the injection port to the point where it is just flush with the external port opening. If the column is made from thin-walled PTFE tubing, do not tighten the compression fitting over the soft column packing; otherwise, the Chromosorb T may be crushed and a plug may develop that will block carrier flow. Trim any column overhang away from the outer edge of the injection port. It may be necessary to slide a small piece of oversize glass or PTFE tubing over the column into the injection port in order to center the column with the septum retainer fitting. Be careful not to block any holes drilled in the port for carrier flow. Gently tighten the compression fitting around the column over the glass wool plug. Replace the septum and septum retainer fitting. Because the analyte is thermally labile, it must not contact hot metallic or glass surfaces in the gas chromatograph. To eliminate this contact, push the end of the column into the detector port up to the detector itself. If the design of the instrument does not permit the column to be pushed up to the detector, the transfer line from the end of the column to the detector must be replaced with low deadvolume PTFE tubing. Use a 1.6-mm ID × 2.6-mm OD × 1 cm long PTFE plug to seal the detector end of NIOSH Manual of Analytical Methods (NMAM), Fourth Edition