Page:NIOSH Manual of Analytical Methods - 5602.pdf/5

 CHLORINATED AND ORGANONITROGEN HERBICIDES (AIR SAMPLING): METHOD 5602, Issue 1, dated 15 January 1998 - Page 5 of 14

APPENDIX - DIAZOMETHANE DERIVATIZING REAGENT The diazomethane generator (see Figure 3) consists of two 40-mL test tubes, each fitted with a two-hole rubber stopper. In one hole of the first test tube, a glass tube is placed which extends to within one centimeter of the bottom. The other end of the glass tube is connected to supply a of nitrogen. A short piece of Teflon® tubing is placed in the second hole and is directed to the bottom of the second tube through the second stopper. A third piece of Teflon® tubing leads from the second tube into the receiving flask. The first test tube contains a small quantity of diethyl ether. Nitrogen bubbled through the ether is led to the second tube containing 3 mL of a 37% KOH-in-water solution and 4 mLDiazald® Reagent,” which is prepared by dissolving 10 g of Diazald® in 100 mL of 1:1 Ethyl ether: Carbitol. Diethyl ether vapor in the first tube prevents loss of diethyl ether from the second tube by evaporation. Diethyl ether stabilizes diazomethane through adduct formation. The resulting diazomethane gas is swept by a flow of nitrogen gas into a flask of chilled (0 °C) methyl t-butyl ether/methanol extraction solvent (maximum volume, 500 mL). NOTE: KOH solution (37% w/v) will become weaker over time owing to adsorption of atmospheric carbon dioxide. Under such circumstances, diazomethane generation will be considerably slower.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition