DETERMINATION OF BRONOPOL, BRONIDOX, AND METHYLDIBROMO GLUTARONITRILEIN COSMETICS BY LIQUID-CHROMATOGRAPHY WITH ELECTROCHEMICAL DETECTION

A method for the simultaneous determination of methyldibromo glutaroni trile, bronopol, and bronidox in cosmetics, based on liquid chromatogr aphy with electrochemical detection, is described. The method is suita ble for both aqueous products and emulsions. The detection limit is be tter than 0.002% for all analytes. Recoveries from an emulsion, spiked to concentrations of 0.03% of the analytes, were 100.4% for bronopol [relative standard deviation (RSD), 0.43%], 97.1% for bronidox (RSD, 0 .83%), and 98.4% for methyldibromo glutaronitrile (RSD, 1.7%). Repeata bilities were calculated from 10 replicate analyses of commercial samp les. The repeatability for bronopol from an emulsion containing 0.047% bronopol was 0.0027% (RSD, 1.99%); for bronidox from a lotion contain ing 0.027% bronidox, 0.0014% (RSD, 1.86%); and for methyldibromo gluta ronitrile from an emulsion containing 0.031% methyldibromo glutaronitr ile, 0.0019% (RSD, 2.16%). A ruggedness test showed that sample amount influenced the results for all 3 analytes. The results obtained for b ronidox also depended on detection parameters and composition of extra ction solvent. The method was applied to 138 cosmetic products and per formed trouble free during these analyses. Bronopol was found in 14 sa mples, and bronidox was found in 4 samples, including a baby hair loti on, in which it is prohibited. Methyldibromo glutaronitrile was presen t in 27 samples, including creams, lotions, and sun protection cosmeti cs.