Solid-phase extraction and field-amplified sample injection-capillary zone electrophoresis for the analysis of benzophenone UV-filters in environmental water samples

Abstract

A field amplified sample injection-capillary zone electrophoresis (FASI-CZE) method for the analysis of benzophenone (BP) UV-filters in environmental water samples was developed, allowing the separation of all compounds in less than 8 minutes. A 9- to 25-fold sensitive enhancement was obtained with FASI-CZE, achieving limits of detection down to 21-59 µg/L for most of the analyzed BPs, with acceptable run-to-run and day-to-day precisions (relative standard deviations lower than 17%). In order to remove water sample salinity and to enhance FASI sensitivity, an off-line solid-phase extraction (SPE) procedure using a Strata X polymeric reversed-phase sorbent was proposed, obtaining recoveries up to 72-90% for most of benzophenones. With the combination of off-line SPE and FASI-CZE, limits of detection in the range 0.06-0.6 µg/L in a river water matrix, representing a 2400- to 6500-fold enhancement, were obtained. Method performance was evaluated by quantifying a blank river water sample spiked at 1 µg/L. For a 95% confidence level, no statistical differences were observed between found concentrations and spiked concentrations (probability at the confidence level, p value, of 0.60), showing that the proposed off-line SPE-FASI-CZE method is suitable for the analysis of benzophenone UV-filters in environmental water samples at low µg/L levels. The method was successfully applied to the analysis of BPs in river water samples collected before and after industrialized and urban areas, and in some drinking water samples.