Pivaloyl chloride as a new derivatization agent for parabens and its application in simultaneous derivatization and air-assisted liquid-liquid microextraction of the analytes in hygiene and personal care products

An air-assisted liquid-liquid microextraction method using of an extraction solvent (less dense than water) has been proposed for simultaneous derivatization and extraction of some p-hydroxybenzoic acid esters (parabens) in different samples before their determination with gas chromatography-flame ionization detection. The analytes are derivatized by a fast reaction occurring between parabens and pivaloyl chloride (as a derivatization agent) and extracted into toluene (as an extraction solvent) under mild conditions in a test tube. After performing the microextraction procedure, a home-made device (an inverse funnel having a capillary tube) is placed into the tube. A thin film of the extractant accumulated on the surface of the aqueous phase is transferred into the capillary part of the device. A fraction of the organic phase is removed by a microsyringe and injected into the separation system for analysis. Under optimum conditions, detection and quantification limits were between 0.60 and 1.0; and 1.7 and 3.1 ng mL(-1) in solution; and 6.0 x 10(-6) and 1.0 x 10(-5); and 1.7 x 10(-5) and 3.1 x 10(-5) g kg(-1) in solid, respectively. The enhancement and enrichment factors were obtained in the ranges of 492-650 and 380-410, respectively. Relative standard deviations were less than 6% (n = 6) for intra- and less than 9% (n = 4) for inter-day precisions calculated at a concentration of 50 ng mL(-1) of each analyte. The calibration graphs were linear with coefficients of determination >= 0.994. Finally, the selected parabens were successfully analyzed in various hygiene and personal care products by the proposed method.