Online coupling lab on valve-dispersive liquid–liquid microextraction-multisyringe flow injection with gas chromatography-mass spectrometry for the determination of sixteen priority PAHs in water

Abstract

A novel approach exploiting lab on valve-dispersive liquid–liquid microextraction-multisyringe flow injection analysis (LOV-DLLME-MSFIA) coupled to gas chromatography-mass spectrometry (CG-MS) is presented. The method is based on the aspiration and mixing of the sample and all required reagents in the holding coil of a LOV-MSFIA system and delivering it into a miniaturized LOV platform equipped with a conical tube used as an extraction chamber (EC), where the mixture of extraction solvent and disperser solvent is added at a high flow rate, resulting in the formation of a cloudy state and extraction of analytes of interest. Because the extraction and dispersive solvent mixture used has a density significantly higher than water, the resulting fine droplets in the mixture, which contain the extracted analyte, are self-sedimented in thirty seconds, not requiring centrifugation for separation of the extraction phase. Afterwards, the extracted fraction is aspirated and transferred to a rotary micro-volume injection valve (MIV), where finally it is introduced via an air stream into the injector of the GC, through a silica capillary transfer line with no stationary phase, used as interface. The potential of the devised LOV-DLLME-MSFIA/CG-MS assembly was demonstrated in the determination of polycyclic aromatic hydrocarbons (PAHs) in tap water, rain water, river surface water and raw landfill leachates. Under optimized conditions, good enrichment factors (EFs) (27–38) and acceptable total DLLME yields (80–102%) were obtained. Calibration curves were linear with correlation coefficients higher than 0.996 in the working range level of 0.25–250 μg L⁻¹, and relative standard deviations (RSD%) were lower than 5% (n = 5). Detection limits were within the range of 0.01–0.07 μg L⁻¹.