Application of partial least-squares spectrophotometric-multivariate calibration to the determination of 2-sec-butyl-4,6-dinitrophenol (dinoseb) and 2,6-dinitro-p-cresol in industrial and water samples containing hydrocarbons

The present report describes the spectrophotometric determination of 2-sec-butyl-4,6-dinitrophenol (dinoseb) and 2,6-dinitro-p-cresol, two inhibitors of the styrene polimerization, in two very different types of matrices. One of them is present in an industrial distillation tower, and contains styrene and more than 60 hydrocarbons. Partial least-squares (PLS) multivariate calibration enabled us to determine both analytes without the necessity of applying extraction processes, as well as significantly reducing the time involved in the currently applied analytical method. The limit of detection for both compounds, referred to the industrial sample, was 1.0 μg ml−1, for concentration ranges of 0-261 μg ml−1 (dinoseb) and 0-448 μg ml−1 (2,6-dinitro-p-cresol). The method was successfully applied to real samples. In addition, dinoseb was simultaneously determined with 2,6-dinitro-p-cresol in hydrocarbon-water mixtures by PLS calibration. In this type of samples, the concentrations are significantly lower and thus a pre-concentration step through solid-phase extraction preceded the spectrophotometric measurements. The limits of detection for the simultaneous determination of dinoseb and 2,6-dinitro-p-cresol were 1.2 and 1.0 ng ml−1, respectively.