ISOCYANATES: METHOD 5522, Issue 2, dated 15 January 1998 - Page 4 of 6 the DMSO solvent is hygroscopic, additional storage studies were conducted in the presence of 17% water for each of the four diisocyanate-tryptamine derivatives. Theaverage recovery for the four diisocyanatetryptamine derivatives measured at one level was 95.8% for a 28-day storage period. Some of the samples were stored over a period of several months. HDI derivative had a recovery of 96.4% after 4 months. MDI derivative was stable for 5 months with a 98.9% recovery. No interference in the method was found from acetone, methyl ethyl ketone, benzaldehyde, acetophenone, or cyclohexanone. Aromatic diamines with the same retention times as the analytes are potential interferences. Therefore, the use of an electrochemical detector is recommended for confirmation of isocyanate peaks. Because of the high solidification point of DMSO, the addition of a reagent to lower the freezing point was necessary for sampling in environments <60oF. An 80:20 DMSO:acetonitrile solution containing the derivatizing reagent is recommended. Recovery studies were conducted in 80:20 DMSO:acetonitrile. For each diisocyanate, liquid spikes were prepared in groups of six samples at 3 concentration levels. The average recoveries were 84% for 2,4-TDI, 104% for 2,6-TDI, 85% for HDI, and 88% for MDI. Storage stability studies of six samples at one level for each diisocyanate-tryptamine derivative yielded an average recovery for the four diisocyanate-tryptamine derivatives of 96% for 7 days and 95% for 28 days. For more detail, see the Backup Data Report for this method [1].
REFERENCES: [1] [2] [3]
Key-SchwartzRJ, Tucker SP [1994]. Backup data report for isocyanates, Method 5522, NIOSH/DPSE. Unpublished report. Wu WS, Stoyanoff RE, Szklar RS, Gaind VS, Rakanovic M [1990]. Application of tryptamine as a derivatising agent for airborne isocyanate determination. Analyst 115: 801-807. Schwope AD, Randel MA, Broome MG [1981]. Dimethyl sulfoxide permeation through glove materials. Am Ind Hyg Assoc J42(10): 722-725.
METHOD WRITTEN BY: Rosa J. Key-Schwartz, Ph.D. and Samuel P. Tucker, Ph.D., NIOSH/DPSE
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition
