Microextraction Tech

Dispersive liquid-liquid microextraction (DLLME) is a consolidated sample treatment technique which is characterized by its high efficacy leading to high enrichment factors. In the normal mode, the technique consists of the dispersion of a mixture of disperser and extraction solvents into the aqueous sample. The dispersion forms a cloudy state consisting of a innumerable extractant droplets which favors the transference of the analyte from the bulk sample. Hashemi et al. (1) adapted this technique to the extraction of non-aqueous phases giving rise to the so-called reverse phase DLLME (RP-DLLME). Reverse DLLME has been recently applied by researchers of the University of Murcia (Spain) for the extraction of cadmium and lead from edible oils (2). This is a problem of concern due to the inherent toxicity of both elements and their capability to influence some oxidative reactions that may lead to toxic compounds. To perform the RP-DLLME the sample is extracted with a mixture containi...

Dispersive liquid-liquid microextraction (DLLME) is a consolidated technique in the treatment of liquid samples due to its rapidity and efficiency. In fact, the almost complete extraction of the analytes, with absolute recoveries near to 100%, can be achieved in a few minutes. In the classical DLLME approach a mixture of solvents, the disperser and extraction ones, is injected in the sample producing the efficient dispersion of the extractant which enhances the contact area with the sample. After dispersion, the extract is recovered by means of a centrifugation step. Despite its usefulness, the classical approach presents some limitations. For example, the requirement of a disperser solvent in the mL range is not completely compatible with a green procedure, although the typical solvents are not too toxic. Moreover, the disperser solvent may participate in the analytes partition, especially for polar analytes, increasing the solubility of the analytes in the sample. Air assist...

The efficient dispersion of the extracting phase into the sample is a useful strategy to enhance the kinetic of a given extraction technique. The dispersion enhances the contact area between phases making easier the transference of the target analytes across the interface. Dispersive procedures have been exploited both in the liquid and solid (micro)extraction techniques, being dispersive liquid-liquid microextraction (DLLME) a preeminent example. In DLLME, the dispersion of the extractant can be assisted chemically, by using a disperser solvent or surfactants, or applying an external energy source like ultrasounds. In a recent article, accepted for publication in Talanta, aerosol phase extraction (APE) has been proposed for the first time as an alternative to these conventional approaches (1). In APE the sample is nebulized by an inert gas into the extracting phase in the form of very small drops. APE presents two very positive aspects which must be highlighted. On the one han...

Dispersive liquid-liquid microextraction (DLLME) was firstly proposed by Rezaee et al. in 2006 (1) as a simple, rapid and cheap extraction technique capable to provide high recoveries and enrichment factors. In DLLME, the organic acceptor phase is dispersed into the sample assisted by an appropriate solvent or by an external energy source (like ultrasounds) producing a cloudy solution. As a consequence of the dispersion, the surface to volume ratio of the acceptor phase increases dramatically, making easier the mass transference through the interfase and therefore reducing the extraction times and increasing the enrichment factors. After the dispersion, the organic extractant should be recovered for its final analysis. This final step is the limiting factor of the technique since in most of the cases a centrifugation step is required. Despite its efficiency, the centrifugation step is an off-line process which avoids the potential automation of the technique and therefore its integra...