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 DYES, BENZIDINE-, o-TOLIDINE-, o-DIANISIDINE-: METHOD 5013, Issue 2, dated 15 August 1994 - Page 4 of 5

EVALUATION OF METHOD: This method was laboratory evaluated over the ranges listed in Table 1 [2]. The concentration of dye remaining after reduction varied from 0 to 6% as determined by visible spectrophotometry. The reduced free amine was confirmed by GC/MS. The lower end of the measurement range was defined as the level which gave at least 75% recovery with approximately 10% Sr. For C. I. Direct Red 28, the range covered 27.3 to 273 µg dye per sample. The lower level of this range gave 94.4% recovery ( Sr = 6.3%) based on free benzidine for six replicate samples. For the other three dyes the results were as follows: C. I. Direct Blue 6, 15.0 to 300.0 µg dye per sample, 100.3% recovery ( Sr = 4.34%); C. I. Direct Brown 95, 24.3 to 243 µg dye per sample, 78.5% recovery ( Sr = 6.7%); C. I. Direct Black 38, 12.5 to 250.0 µg dye per sample, 78.1% recovery ( Sr = 12.8%). The pooled precisions ( Sr) for samples at three concentrations in the measurement range for each dye are as follows: Direct Red 28, 0.045; Direct Blue 6, 0.061; Direct Brown 95, 0.072; Direct Black 38, 0.078. Since the method does not distinguish between various benzidine-based dyes, recovery correction factors cannot be applied unless a single known dye is contained on the filter. Recovery studies must be performed on the bulks collected with the samples because of variability in sample purity and variety of benzidine-based dyes. Recovery studies on spiked samples stored at 75% relative humidity indicated no change due to humidity in the recoveries or sample stability. A user check of this method [1] gave estimated LODs for benzidine (3 µg per sample; 0.7 µg/mL) and dianisidine (4.5 µg per sample; 1.1 µg/mL). The LODs could be lowered to 0.06 µg/mL for benzidine and 0.07 µg/mL for dianisidine by using fluorescent detection with excitation at 285 nm and emission at 375 nm.

REFERENCES: [1] [2] [3]

[4] [5] [6]

User check, Wisconsin Occupational Health Laboratory (NIOSH, unpublished, September 27, 1984). NIOSH Manual of Analytical Methods, 2nd ed., Vol. 6, P&CAM 325, U.S. Department of Health and Human Services, Publ. (NIOSH) 80-125 (1980). Kennedy, Eugene R. and Martha J. Seymour. Development of an Analytical Method for Benzidine-Based Dyes, Chemical Hazards in the Workplace Measurement and Control, ACS Symposium Series 149, American Chemical Society, Washington, DC, 21-35 (1981). Special Occupational Hazard Review for Benzidine-Based Dyes, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 80-109 (1979). NIOSH Manual of Analytical Methods, 2nd ed., Vol. 1, P&CAM 234, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-157-A (1977). Preventing Health Hazards from Exposure to Benzidine Congener Dyes, U.S. Department of Health and Human Services, Publ. (NIOSH) 83-105 (1983).

METHOD WRITTEN BY: Eugene R. Kennedy, Ph.D., Martha J. Seymour and Charles E. Neumeister, NIOSH/DPSE.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94