In-syringe-assisted dispersive liquid-liquid microextraction coupled to gas chromatography with mass spectrometry for the determination of six phthalates in water samples

A fully automated method for the determination of six phthalates in environmental water samples is described. It is based in the novel sample preparation concept of in-syringe dispersive liquid-liquid microextraction, coupled as a front end to GC-MS, enabling the integration of the extraction steps and sample injection in an instrumental setup that is easy to operate. Dispersion was achieved by aspiration of the organic (extractant and disperser) and the aqueous phase into the syringe very rapidly. The denser-than-water organic droplets released in the extraction step, were accumulated at the head of the syringe, where the sedimented fraction was transferred to a rotary micro-volume injection valve where finally was introduced by an air stream into the injector of the GC through a stainless-steel tubing used as interface. Factors affecting the microextraction efficiency were optimized using multivariate optimization. Figures of merit of the proposed method were evaluated under optimal conditions, achieving a detection limit in the range of 0.03-0.10 μg/L, while the RSD% value was below 5% (n = 5). A good linearity (0.9956 ≥ r(2) ≥ 0.9844) and a broad linear working range (0.5-120 μg/L) were obtained. The method exhibited enrichment factors and recoveries, ranging from 14.11-16.39 and 88-102%, respectively.