2010Dispersive Liquid-Liquid Microextraction Coupled.pdf

Dispersive Liquid-Liquid Microextraction Coupled with Dispersive μ-Solid-Phase Extraction for the Fast Determination of Polycyclic Aromatic Hydrocarbons in Environmental Water Samples Zhi-Guo Shi and Hian Kee Lee* Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543 A new two-step microextraction technique, combining dispersive liquid-liquid microextraction (DLLME) and dispersive microsolid-phase extraction (D-μ-SPE), was developed for the fast gas chromatographic-mass spec- trometric determination of polycyclic aromatic hydrocar- bons (PAHs) in environmental samples. A feature of the new procedure lies in that any organic solvent immiscible with water can be used as extractant in DLLME. A special apparatus, such as conical-bottom test tubes, and tedious procedures of centrifugation, refrigeration of the solvent, and then thawing it, associated with classical DLLME or similar techniques are not necessary in the new proce- dure, which potentially lends itself to possible automation. In the present D-μ-SPE approach, hydrophobic magnetic nanoparticles were used to retrieve the extractant of 1-octanol in the DLLME step. It is noteworthy that the target of D-μ-SPE was the 1-octanol rather than the PAHs. Because of the rapid mass transfer associated with the DLLME and the D-μ-SPE steps, fast extraction could be achieved. Parameters affecting the extraction efficiency were investigated in detail. The optimal conditions were as follows: vortex at 3200 rpm in the DLLME step for 2 min and in D-μ-SPE for 1 min and then desorption by sonication for 4 min with acetonitrile as the solvent. The results demonstrated that enrichment factors ranging from 110- to 186-fold were obtained for the analytes. The limits of detection and the limits of quantification were in the range of 11.7-61.4 pg/mL and 0.04-0.21 ng/mL, respectively. The linearities were 0.5-50, 1-50, or 2-50 ng/mL for different PAHs. Finally, the two-step extraction method was su