Direct HPLC Determination of n-Alkyl Benzene Sulfonates in Powder Detergent

A reversed phase HPLC method for determination of sodium n-alkyl benzene sulfonates (n-ABS) in powder detergent was proposed.Analytical conditions of the method were studied and the optimum conditions found were as follows: ① stationary phase: Venusil XBP-C18 (4.6 mm×250 mm,5 μm) chromatographic column;② mobile phase: a mixed solution of acetonitrile and aq.solution of 0.1 mol·L-1 NaClO4,mixed in the ratio of 6 to 4 by vol.;③ flow-rate of mobile phase: 1.0 mL·min-1;④ column temperature: 40 ℃;⑤ wavelength for UV-detection: 225 nm.By applying the conditions given above,homologues of n-ABS were very well separated and the average number of carbon atom and the average relative molecular mass of the sample were found;and in addition,isomers of n-ABS were also separated.By the proposed method,analysis of a sample was completed within 22 min.Linear regression equation of the standard curve was found as follows: y=7 552.4 x-5 282.3 (r=0.999 6),and detection limit (3S/N) found was 1 mg·L-1.Precision and recovery of the method were tested,and values of RSD (n=6) and recovery found were 0.3% and in the range of 96.3%-105.0%.