Simple and Rapid Determination of Linear Alkylbenzene Sulfonates by In-Tube Solid-Phase Microextraction Coupled with Liquid Chromatography

Abstract

A simple and rapid method for the determination of linear alkylbenzene sulfonates (LAS) in aqueous samples was developed by using in-tube solid-phase microextraction (SPME) coupled with liquid chromatography (LC). Introducing a short section of open-tubular gas chromatography column as the extraction device, in-tube SPME method has been developed by Pawliszyn et al. for an effective on-line coupling of sample preparation and LC separation. As an open tubular capillary column for the in-tube SPME, we used a porous-layer open-tabular (PLOT) column with a porous layer on the inner wall and a larger surface area. The separation of LAS was carried out by using a mobile phase containing 65% acetonitrile and 35% sodium perchlorate aqueous solution (287 mM) with a Wakopak® WS AS-Aqua column. LAS in the sample solution was enriched through the capillary sequentially by using a microsyringe pump equipped with a gastight syringe and analyzed by using high performance liquid chromatography with fluorescence detection. The fluorescence excitation and emission were fixed at λex = 221 nm and λem =284 nm. With the optimum conditions, linear calibration curves were obtained from 0.2 to 25 μg/l. The detection limits based on 3σ were between 0.02 and 0.10 μg/l and the relative standard deviations of the method were between 1.6 and 12% (n = 5). The method was successfully applied to the determination of LAS in natural water samples. This method was applied to the determination of LAS in some urban river waters where domestic wastewater was discharged.