Determination of linear alkylbenzenesulfonates in water samples by immunoaffinity chromatography with fluorescence detection

A simple and fast immunochromatographic method is proposed for the determination of linear alkylbenzenesulfonates (LASs) in real water samples. The approach consists of the injection in a commercial Protein G column of a preincubated mixture containing linear sodium 4-dodecylbenzenesulfonate (LDS), which was chosen as a LAS model, polyclonal anti-LAS antibodies, and a fluorescent tracer based on the coupling of a LAS mimic to a fluorescein derivative. This approach allows the separation of free and bound tracer fractions without any additional elution step, and the direct measurement of the fluorescence of the free tracer through the peak height of the immunochromatogram, which was proportional to the analyte concentration. The immunocolumn can be used up to 50 times without eluting and regenerated for at least 15 times. The dynamic range of the method is 0.09-3.0 μg ml−1 LDS and the detection limit is 35 ng ml−1. The precision, expressed as relative standard deviation, ranges between 5.4 and 7.1%. The application of the method to the analysis of water samples (tap-, ground- and waste-water) was carried out including a previous solid-phase extraction step that allowed to obtain a detection limit of 7 ng ml−1, using 100 ml of water sample. The range of the standard deviation obtained was 4-10 and the recoveries obtained for spiked samples ranged from 85.8 to 110.8%.