Page:NIOSH Manual of Analytical Methods - 9201.pdf/4

 CHLORINATED AND ORGANONITROGEN HERBICIDES (PATCH): METHOD 9201, Issue 1, dated 15 January 1998 - Page 4 of 11

compounds. To determine the LODand LOQ values, a series of media-spiked standards was prepared in triplicate, analyzed, and fitted with a quadratic curve. The Limit of Detection (LOD) and Limit of Quantitation (LOQ) were estimated with Burkart’s Method[3]. Actual LOD and LOQ results were inconsistent owing to periodic low level interferences in the media. Therefore, higher arbitrary LODs and LOQs were selected in order to circumvent the problem. The higher LODs were assumed to be more realistic and were used for evaluation of the method. A set of samples for long-term storage study was prepared and analyzed after 1, 30, and 120 days. The results are summarized in Table 3. The day 1 results show that the compounds, except for 2,4-D acid and the 2,4-D-butoxy ester, give 90% or better recovery based on the amount spiked onto the samplers. When compared to day 1, the day 30 sample results were all92%. The PUF patch samples were shown to be stable for at least 30 days when refrigerated at 4C.

REFERENCES: [1] [2] [3]

NIOSH [1995]. Back-up data report for chlorinated organonitrogen and carboxylic acid herbicides. Prepared under NIOSH Contract 200-88-2618 (unpublished). Black TH [1983]. The preparation and reactions of diazomethane. Aldrichimica Acta 16(1). Burkart JA [1986]. General procedures for limit of detection calculations in the industrial hygiene chemistry laboratory, Appl Ind Hyg1(3):153-155.

METHOD WRITTEN BY: Don C. Wickman, John M. Reynolds, and James B. Perkins, DataChem Laboratories, Salt Lake City, Utah

APPENDIX. DIAZOMETHANE GENERATOR The diazomethane generator (see Figure 2) consists of two 40-mL test tubes, each fitted with a two-hole rubber stopper. A glass tube which extends to within one centimeter of the bottom of the first test tube is inserted in one hole of the stopper. The other end of the glass tube is connected to a supply of nitrogen. A short piece of PTFE 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 PTFE 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% (w/v) KOH/water solution and 4 mL “Diazald Reagent,” which is prepared by dissolving 10 g Diazald in 100 mL of 1/1 Ethyl ether/Carbitol. (Nitrogen becomes saturated with diethyl ether vapor in the first tube in order that nitrogen does not deplete the second tube of diethyl ether; diethyl ether stabilizes diazomethane through adduct formation.) The resulting diazomethane gas is swept into a flask of chilled (0 °C) isopropanol (maximum volume, 500 mL) by a flow of nitrogen gas. NOTE: The KOH solution (37% w/v) will become weaker over time from the absorption of atmospheric carbon dioxide. Under such circumstances,diazomethane generation will be considerably slower.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition