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Automated Agitation-Assisted Demulsification Dispersive Liquid–Liquid Microextraction

Guo, Liang, Chia, Shao Hua, Lee, Hian Kee
Analytical chemistry 2016 v.88 no.5 pp. 2548-2552
agitation, automation, centrifugation, detection limit, emulsions, gas chromatography, labor, liquid-phase microextraction, mass spectrometry, polycyclic aromatic hydrocarbons, river water, solvents, statistical analysis
Dispersive liquid–liquid microextraction (DLLME) is an extremely fast and efficient sample preparation procedure. For its capability and applicability to be fully exploited, full automation of its operations seamlessly integrated with analysis is necessary. In this work, for the first time, fully automated agitation-assisted demulsification (AAD)-DLLME integrated with gas chromatography/mass spectrometry was developed for the convenient and efficient determination of polycyclic aromatic hydrocarbons in environmental water samples. The use of a commercially available multipurpose autosampler equipped with two microsyringes of different capacities allowed elimination or significant reduction of manpower, labor, and time with the large-volume microsyringe used for liquid transfers and the small-volume microsyringe for extract collection and injection for analysis. Apart from enhancing accessibility of DLLME, the procedure was characterized by the application of agitation after extraction to break up the emulsion (that otherwise would need centrifugation or a demulsification solvent), further improving overall operational efficiency and flexibility. Additionally, the application of low-density solvent as extractant facilitated the easy collection of extract as the upper layer over water. Some parameters affecting the automated AAD-DDLME procedure were investigated. Under the optimized conditions, the procedure provided good linearity (ranging from a minimum of 0.1–0.5 μg/L to a maximum of 50 μg/L), low limits of detection (0.010–0.058 μg/L), and good repeatability of the extractions (relative standard deviations, below 5.3%, n = 6). The proposed method was applied to analyze PAHs in real river water samples.