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Development of an analytical method for benzidine-based dyes.

Kennedy-ER; Seymour-MJ
Chemical Hazards in the Workplace, Measurement and Control. ACS Symp Ser 1981; :21-35
A high performance liquid chromatography (HPLC) method for determining benzidine (92875) in benzidine based dyes was developed. Standard solutions of benzidine in methanol were prepared. Filter samples were prepared with known volumes of the dye solution. Filters were dried in a dessicator. Total filter area was washed with 1 milliliter (ml) of water. A 1ml reduction/buffer solution without sodium-hydrosulfite was added. Filter and solution were placed in an ultrasonic bath for 15 minutes. A 1ml aliquot was transferred to a vial and 1ml of freshly prepared sodium- hydrosulfite in phosphate reduction buffer was added to reduce the samples to free benzidine, capped, and shaken several times. The original color of the solution changed or disappeared according to the dye present. A 10 microliter aliquot was injected into the liquid chromatograph. The method was evaluated with four benzidine based dye formulations ranging from 12 to 300 micrograms benzidine per sample. The measurement limit was 0.38 nanogram per microliter benzidine for known samples. Average recovery was between 98 and 106.0 percent. Analytical reproducibility was 10 percent the coefficient of variation at this limit. Variations resulted from the HPLC buffer concentration, column back pressure, and mobile phase composition. The four different benzidine based dye formulations passed the test for homogeneity except for the lowest concentration of Direct-Black-38 (1937377). The authors conclude that HPLC can be used to identify and quantify benzidine based dye containing samples and can be expanded to include samples taken from media other than air with minor modifications.
Analytical-methods; Workplace-studies; Industrial-hazards; Monitoring-systems; Analytical-models; Chemical-processing; Workers; Hazards; Monitors; Chemical-analysis
92-87-5; 1937-37-7
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Chemical Hazards in the Workplace, Measurement and Control. ACS Symposium Series No. 149