Three phase electroextraction

By -
In March we published a post about electromembrane extraction (EME), which was firstly proposed in 2006 by Pedersen-Bjergaard and Rasmussen. This microextraction technique is based on the voltage-assisted migration of the target analytes from two aqueous solutions, the sample and the acceptor phase, which are separated by a polymeric membrane where an organic solvent is immobilized in the form of a supported liquid membrane (SLM).

Recently, a research group of the University of Leiden at Netherlands has presented a three phase electroextraction technique that shares some of the principles of EME. The new technique is characterized by the extreme reduction of the required sample and extractant volumes and therefore it is especially interesting for bioanalytical applications. Moreover, the process is rapid and it has been coupled on line to nanoelectrospray direct infusion mass spectrometry.

The proposed manifold is schematically described in the Figure. 50 µL of an aqueous donor phase (or sample) are introduced in an eppendorf tube and 150 µL of an appropriate organic solvent (lighter than water) are immediately transferred to the vial forming a biphasic system. In a second step, a micropipette tip containing 2 µL of an acceptor phase is introduced in the organic solvent layer. In order to produce the electromigration of the analytes from the donor to the acceptor phase, two electrodes and a DC power supply are required. The electric contact between the aqueous phases is possible thanks to a two innovative aspects: the micropipette tip is made of a conductive polymer, and the positive electrode is partially covered by a protective PTFE coating. The extraction performance has been demonstrated in an impressive movie which is freely available in the journal web page (Link to supplementary information files)

Finally, the proposed technique was applied to the determination of some carnitines in human plasma giving enrichment factors up to 5.1 in only 3 min.

We strongly recommend this article to our readers and we invite to read with interest three aspects a) the effect of the phases composition on the electromigration of the analytes; b) the effect of the acceptor phase composition in the electrospray process efficiency and c) and the extraction-determination integration

Reference

(1) Three-Phase Electroextraction: A New (Online) Sample Purification and Enrichment Method for Bioanalysis. Link to the article

Comments

Post a Comment

Popular posts from this blog

Fabric phase sorptive extraction: a new generation green sample preparation strategy

By -
Image
by Dr. Abuzar Kabir, International Forensic Research Institute, Department of Chemistry and Biochemistry, Florida International University, Miami, Florida, USA Fabric phase sorptive extraction (FPSE), the most recent member of the sorptive microextraction family, has innovatively incorporated both solid phase microextraction (SPME) and solid phase extraction (SPE) techniques into a single technology platform. FPSE utilizes permeable natural/synthetic fabrics e.g., cotton, polyester, fiber glass supports to chemically bind sol-gel hybrid inorganic-inorganic sorbents. A 5 cm2unit of coated fabric (2.5 cm x 2.0 cm) is typically used as the extraction media which can be inserted directly into the sample container. Extraction of the analytes is generally expedited by using a magnetic stir bar to diffuse the analyts into the sample matrix so that rapid mass transfer from the sample matrix to the extraction medium takes place.Once the mass transfer equilibrium between the FPSE media and
Read more

Gold coated magnetic beads for electrochemical detection

By -
Image
This post summarizes an interesting article, recently accepted for publication in Analytical Chemistry, which presents an innovative use of magnetic beads. Researchers from the Osaka Prefecture University at Japan have proposed the synthesis of magnetic microbeads covered with a smooth gold layer that are used for the electrochemical detection of streptavidin (1). The synthesis, which is deeply described in the manuscript, consists of three well defined steps. First of all, the magnetic beads are introduced in a colloidal gold dispersion containing Au-nanoparticles (Au-NPs). Thanks to the opposite zeta potential of both materials (microbeads are negatively charged while Au-NPs present a positive charge), their assembly takes place by electrostatic interactions. However, the Au-NPs are not connected to each other and therefore the electrical resistance of the microbeads is too high. In a second step, the modified microbeads are dispersed in an aqueous medium containing HAuCl 4 as
Read more

Rotating Disk Sorptive Extraction

By -
Image
by Prof. Dr. Pablo Richter, Department of Inorganic and Analytical Chemistry, Faculty of Chemical and Pharmaceutical Sciences, University of Chile. The modern trends in analytical chemistry promote efficiency and green technology in sample preparation. In this context, our research team developed a new technique in 2009 that is capable of extracting pollutants from liquid samples on a rotating PTFE disk with one surface coated with an extraction phase [1]. The disk has embedded a miniature magnetic rod, which allows rotation. We have termed this procedure rotating-disk sorptive extraction (RDSE). RDSE is currently available in two configurations. In the classic version (Figure 1), the extraction phase is a polymeric film adhered to one side of the PTFE disk (configuration 1). In this configuration, polydimethylsiloxane (PDMS), nylon and octadecyl (C18) have been used as the sorptive material for the extraction of low-polarity analytes (Log Kow between 3 and 7) [1-12]. However
Read more