Hollow fiber-based LPME

Rasmussen and Pedersen-Bjergaard reviewed the developments in hollow fiber-based LPME [198]. In hollow fiber-based LPME, anal)hes of interest are extracted from aqueous samples, through a thin layer of organic solvent immobilized within the pores of a porous hollow fiber, and into an acceptor solution inside the lumen of the hollow fiber. Subsequently, the acceptor solution is directly subjected to a final analysis by capillary gas chromatography (CGC), HPLC, CE, or MS without further efforts. In this review, it has been indicated that hollow fiber-based LPME may provide high analyte preconcentration and excellent sample cleanup, and has a broad apphcafion potential within areas such as... 

Ramos Paydn M, Bello L6pez mA, Fernandez-Torres R, Callejon Mochon M, Gomez Ariza JL. Application of hollow fiber-based liquid-phase microextraction (HF-LPME) for the determination of acidic pharmaceuticals in wastewaters. Talanta 2010 82 854-858. 

Ramos Payan M, Bello Lopez mA, Femandez-Torres R, Gonzalez JAO, Callejdn Mochon M. Hollow fiber-based liquid phase microextraction (HF-LPME) as a new approach for the HPLC determination of fluoroquinolones in biological and environmental matrices. J Pharm Biomed Anal 2011 55 332-341. 

FIGURE 12.2 Hollow-fiber devices for membrane extraction, (a) Hollow-fiber loops for equilibrium extraction redrawn after Liu et al. (From Liu, J.-F., Jbnsson, J.A., and Mayer, P., Anal. Chem., 77, 4800, 2005.) (b) Liquid-phase microextraction after Pedersen-Bjergaard and Rasmussen. (From Grpuhaug Halvorsen, T., Pedersen-Bjergaard, S., Reubsaet, J.L.E., and Rasmussen, K.E., J. Sep. ScL, 24, 615, 2001. With permission.) (c) Syringe-based hollow fiber LPME. (Erom Zhao, L. and Lee, H.K., Anal. Chem., 74, 2486, 2002. Copyright 2002 American Chemical Society. With permission.)... 

Another area in which SLMs have interesting prospects is sample preparation in analytical chemistry. Unlike in other fields where a high active area is required, the new trends are toward miniaturization, which in the case of SLM is represented by the hquid-phase microextraction (LPME) method based on porous hollow fibers [231]. The other issues being addressed are to improve automation and high throughput of the analytical methods, in which the SLM system is used as an analyte enrichment method [167, 232-234]. Additionally, the improvement of selectivity of SLM extraction is one of the main areas of interest see the immuno-SLM method example described earher. Several improvements in this methodology have recently been reported [35, 36, 235-237]. 

LPME has been accomplished either by extraction into a small droplet of organic solvent hanging at the end of a microsyringe needle [181-191] (microdrop) or into small volumes of acceptor solution present inside the lumen of porous hollow fibers [192-194]. In both the microdrop concept and in the hollow fiber format, the analytes of interest are extracted and preconcentrated into a few microliters of appropriate solvents. Because of this, LPME may be very effective for analyte enrichment and may result in a major reduction in the use of organic solvents. A detailed review based on hanging droplets in two- and three-phase LPMEs has been presented by Psillakis and Kalogerakis [195]. 

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