Rapid ultraviolet spectrophotometric determination of bronopol: application to raw material analysis and kinetic studies of bronopol degradation.

A simple and rapid spectrophotometric assay is described for bronopol determination in raw material. The method is based on the measurement of absorbance (at 244 nm) of bromonitroethanol (sodium salt of aci-form), the chromophoric derivative formed from bronopol instantaneously by a retroaldol reaction in the presence of 0.1 M NaOH. This derivative has a molar absorption coefficient of 8330 (at absorption maximum, 244 nm) and its absorbance follows a linear relationship with the concentration of bronopol within the range 5-25 micrograms ml-1. It has been validated that the spectrophotometric method can be applied successfully to the analysis of bronopol in raw material. The sensitivity of the method towards bronopol degradation in aqueous solution is comparable to that obtained by gas-liquid chromatography and enzymatic assays described elsewhere. Thus the proposed method is suitable for use in the study of the kinetics of bronopol degradation. A simple and sensitive detection of bronopol and bromonitroethanol (down to 2 micrograms) on a silica gel 60 F254 precoated thin layer chromatography plate based on the formation of the chromophoric derivative in the presence of ammonia vapour has been described.