Air-assisted liquid-liquid microextraction method as a novel microextraction technique; application in extraction and preconcentration of phthalate esters in aqueous sample followed by gas chromatography-flame ionization detection.

A novel microextraction technique, air-assisted liquid-liquid microextraction (AALLME), which is a new version of dispersive liquid-liquid microextraction (DLLME) method has been developed for extraction and preconcentration of phthalate esters, dimethyl phthalate (DMP), diethyl phthalate (DEP), di-iso-butyl phthalate (DIBP), di-n-butyl phthalate (DNBP), and di-2-ethylhexyl phthalate (DEHP), from aqueous samples prior to gas chromatography-flame ionization detection (GC-FID) analysis. In this method, much less volume of an organic solvent is used as extraction solvent in the absence of a disperser solvent. Fine organic droplets were formed by sucking and injecting of the mixture of aqueous sample solution and extraction solvent with a syringe for several times in a conical test tube. After extraction, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by GC-FID. Under the optimum extraction conditions, the method showed low limits of detection and quantification between 0.12-1.15 and 0.85-4 ng mL(-1), respectively. Enrichment factors (EFs) and extraction recoveries (ERs) were in the ranges of 889-1022 and 89-102%, respectively. The relative standard deviations (RSDs) for the extraction of 100 ng mL(-1) and 500 ng mL(-1) of each phthalate ester were less than 4% for intra-day (n=6) and inter-days (n=4) precision. Finally some aqueous samples were successfully analyzed using the proposed method and three analytes, DIBP, DNBP and DEHP, were determined in them at ng mL(-1) level.