Page:NIOSH Manual of Analytical Methods - 5516.pdf/4

{{center|{{smaller|2,4- and 2,6-TOLUENEDIAMINE: METHOD 5516, Issue 2, dated 15 August 1994 - Page 4 of 5}} {{rule}} {{nop}} {{bold|EVALUATION OF METHOD: [1]}}

The relationship of peak height and concentration of 2,4- and 2,6-bisacetamidotoluene in methanol was found to be essentially linear over the ranges 0.05 to 141 μg/mL and 0.14 to 84 μg/mL, respectively. The time required for completion of the acetylation reaction was determined using samples equivalent to 0.7 μg of 2,4-toluenediamine and 0.9 μg of 2,6-toluenediamine in 15 mL of sampling medium. Aliquots (2 mL) were treated with 10 μL of acetic anhydride and allowed to stand 0.25 to 6 h before further workup and analysis. The acetylation of 2,6-toluenediamine was the slower reaction, but it appeared complete after 4 h. Sample stability was studied using solutions of 2,4- and 2,6-toluenediamine in sampling medium at levels corresponding to 0.89 and 0.74 μg per sample, respectively. The recoveries, ranging from 97% to 106%, suggested the samples were stable under the conditions of storage—1, 7, and 14 days at room temperature in the dark. The potential for interference from isocyanates was investigated by drawing air containing 7.3 μg each of 2,4- and 2,6-toluene diisocyanate through samples of 0.9 μg each of 2,4- and 2,6-toluenediamine in 15 mL of sampling medium. The recoveries from these samples, averaging 95%, suggested that, when compared to identical samples not treated with toluene diisocyanate, a small but statistically significant negative bias was caused by the isocyanate. Using the data from all of the recovery experiments, the relative standard deviation (S$t$) for 2,4-toluenediamine (0.74 and 0.83 μg per sample) ranged from 0.01 to 0.08 with a pooled average ($\overline{St}$) of 0.05 and for 2,6-toluenediamine (0.89 μg per sample) ranged from 0.02 to 0.14 with a pooled average ($\overline{St}$) of 0.06.

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{{center|{{smaller|NIOSH Manual of Analytical Methods (NMAM), Fourth Edition}}}}