Page:NIOSH Manual of Analytical Methods - 2535.pdf/4

 TOLUENE-2,4-DIISOCYANATE: METHOD 2535, Issue 2, dated 15 August 1994 - Page 4 of 5 EVALUATION OF METHOD: A variation of this method which involved normal-phase HPLC (Method P&CAM 326) was tested with fortified samplers and atmospheres generated with a diffusion cell [1,4]. Average recoveries of 2,4-TDIU from front sections of reagent-coated glass wool were 0.97 to 0.99 after applications of 1.0-, 2.1-, 9.9-, and 20.0-µg quantities of 2,4-TDI from a U-tube; Sr was 0.067 (21 samples, pooled). Sr was 0.033 (29 samples, pooled) for 67-L samples at 0.039 to 0.53 mg/m 3. The independent method used for evaluation was that of Meddle and Wood [7]. Average concentrations ranged from 0.054 to 0.46 mg/m by the independent method [1]. Conclusive evidence for bias in the reagent-coated glass wool method was not found. Breakthrough volume was 71 L (0.53 mg/m 3, 1 L/min); breakthrough volume was 279 L (0.14 mg/m 3, 1 L/min). 2,4-TDIU was stable on coated glass wool at room temperature in the dark for 14 days. The reagent, N-[(4-nitrophenyl)methyl]propylamine, is unstable [1]. Evaluation of samplers with 2,4-TDI aerosols was not performed. However, samplers were inefficient collectors when aerosol particles were present in an atmosphere of 4,4'-methylenediphenylisocyanate (MDI). The collection efficiency of each sampler for MDI was about 90% (flow rate, 1 L/min; total concentration of MDI in vapor and aerosol forms, about 0.52 mg/m 3; mass median diameter of MDI particles, about 0.6 µm; geometric standard deviation, about 2.2) [1]. REFERENCES: [1] [2]

[3]

[4] [5] [6] [7] [8]

Tucker, S. P., and J. E. Arnold. Anal. Chem., 54, 1137-1141 (1982). Swinehart, G., K. Mulligan, C. Rice, R. McKay, N. Gener, and G. E. Burroughs. "Hexamethylene Diisocyanate Monomer and Prepolymer Characterization," presented at the American Industrial Hygiene Conference, Dallas, TX (May 20, 1986). Carson, K. A. "Isocyanate Monitoring Using N-p-nitrobenzyl-N-propylamine glass fiber sampling tube," OEHL-82-022EH163HAE, Air Force Occupational Environmental Health Laboratory, Brooks AFB, TX (1982); report (No. AD-A119901) available from NTIS, Springfield, VA 22161. NIOSH Manual of Analytical Methods, 2nd ed., Vol. 6, P&CAM 326, U.S. Department of Health and Human Services, Publ. (NIOSH) 80-125 (1980). Sangö, C. J. Liq. Chromatogr ., 2, 763-774 (1979). Melcher, R. G. Anal. Chem., 55, 40R-56R (1983). Meddle, D. W., and R. Wood. Analyst (London), 95, 402-407 (1970). Hastings Vogt, C. R., C. Y. Ko and T. R. Ryan. J. Chromatogr ., 134, 451-458 (1977).

METHOD WRITTEN BY: Samuel P. Tucker, Ph.D., NIOSH/DPSE.

APPENDIX A: Determination of Purity of 2,4-TDI Dissolve 480 µL (365 mg, 0.00282 mole) dibutylamine in 10 mL tetrahydrofuran. Add 100 µL (122 mg, 0.000701 mole) 2,4-TDI. Stir the mixture and allow to stand 6 min. Add a few drops of bromocresol purple indicator solution. Prepare two additional samples in this manner. Titrate excess dibutylamine with 0.05 M HCl. Calculate percent purity, P, of 2,4-TDI for each sample:

where:

B = Molar quantity of dibutylamine before reaction (0.00282) V = Volume of 0.05 M HCl (L) M = Concentration of HCl (0.05 M) 2 = Number of moles of dibutylamine required to react with 1 mole of 2,4-TDI W = Molar quantity of 2,4-TDI added to tetrahydrofuran solution (0.000701) NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94

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