Determination of Bronopol, Bronidox, and Methyldibromo Glutaronitrile in Cosmetics by Liquid Chromatography with Electrochemical Detection

Abstract

Abstract A method for the simultaneous determination of methyldibromo glutaronitrile, bronopol, and broni-dox in cosmetics, based on liquid chromatography with electrochemical detection, is described. The method is suitable for both aqueous products and emulsions. The detection limit is better 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%). Repeatabilities were calculated from 10 replicate analyses of commercial samples. The repeatability for bronopol from an emulsion containing 0.047% bronopol was 0.0027% (RSD, 1.99%); for bronidox from a lotion containing 0.027% bronidox, 0.0014% (RSD, 1.86%); and for methyldibromo glutaronitrile from an emulsion containing 0.031% methyldibromo glutaronitrile, 0.0019% (RSD, 2.16%). A ruggedness test showed that sample amount influenced the results for all 3 analytes. The results obtained for bronidox also depended on detection parameters and composition of extraction solvent. The method was applied to 138 cosmetic products and performed trouble free during these analyses. Bronopol was found in 14 samples, and bronidox was found in 4 samples, including a baby hair lotion, in which it is prohibited. Methyldibromo glutaronitrile was present in 27 samples, including creams, lotions, and sun protection cosmetics.