[Determination of benzidine in cotton cloth by high performance liquid chromatography(HPLC)]

In this paper, a method for determination of benzidine in cotton cloth by HPLC was studied. First, cotton cloth was treated by sodium dithionite at the temperature of (70 +/- 2) degrees C. On this condition, azo dyes in cotton cloth were reduced to benzidine. Then benzidine was extracted by diethyl ether in sodium hydroxide solution. Benzidine originating from cotton cloth was analysed by HPLC with a column of Hypersil ODS (5 microns, 15 cm x 4.6 mm i.d.), mobile phase of V (MeOH):V(H2O) = 75:25, flow rate of 0.6 mL/min, pressure of 17.7 MPa and detection at 254 nm. By comparison with the standard sample, the retention time of benzidine was about 2.5 min. Benzidine in three samples was determined through parallel experiment. The mass ratio of benzidine in cotton cloth was 94.01, 86.9 and 120.8 micrograms/g, and the average was 100.57 micrograms/g. The average recovery was 84.7%. The experiment expressed that benzidine originating from cotton cloth could be qualitatively and quantitatively determined by HPLC. The accuracy of the results of parallel experiments was related to the reducing process. When the reducing conditions were completely consistent, the result would be more accurate.