Hybrid microextraction using microporous silica as support of a thin solvent film

By -

A new microextraction approach which stands midway between solid phase microextraction (SPME) and single drop microextraction (SDME) has been recently reported by researchers of the University of Isfahan at Iran. The extraction device is quite similar to this employed in SPME, although a bare stainless steel wire is used instead of the classic fiber. The wire is chemically treated in order to anchor a nanolayer of silica on its surface. This synthesis is achieved by a hydrothermal reaction which simply consists on the immersion of the bare wire in a sodium hydroxide solution in close contact with a glass precursor. The reaction, which develops at high temperature, involves the dissolution of the glass precursor in the alkaline solution and its final deposition on the wire. As a result of the process, a microporous layer of silica with a thickness of ca. 14 µm is obtained in the surface of the metallic wire. For analytes extraction, the treated wire is immersed in an appropriate organic solvent which is immobilized by adsorption on the porous surface. This immobilized solvent is the final responsible of the extraction following the general principles of SDME.

This hybrid microextraction combines some of the strengths of SPME and SDME, avoiding their main shortcomings (see Figure 1). Carry over between samples is avoided since a new layer of solvent is used for each extraction. The selection of the extracting phase is more versatile in contrast with SPME where the type of commercially available phases is limited while the procedures for the lab-synthesis of special phases are complicated. Moreover, the hybrid microextraction requires very low volumes of solvent, being therefore a cheaper approach. Furthermore, the new proposal presents some advantages over SDME. On the one hand, the microdrop of solvent is mechanically stable on the wire and its surface to volume ratio is more favorable improving the kinetic of the extraction. The low amount of solvent used as extractant (0.18 µL, while the usual volume in SDME is 2 µL) provides also higher enrichment factors
Advantages of the hybrid microextraction over classic SPME and SDME


The proposed microextraction technique has been evaluated for the determination of some organophosphorous compounds in water by gas chromatography/nitrogen phosphor detection. The obtained results shows an excellent extraction efficacy with preconcentration factors as high as 3210. Moreover, the precision of the extraction was lower than 8.4 % (expressed as relative standard deviation) even when different devices are employed.

Readers are referred to the article, recently published in Analytica Chimica Acta, for further details. In the article they will find the detailed synthesis procedure of the modified wire as well as the optimization process. Special attention should be given to the final comparison between the proposal and conventional microextraction techniques like SPME, SDME or hollow fiber liquid phase microextraction. This final combination highlights the usefulness of the proposal.

References

Link to the article. Microporous silica with nanolayer structure coated with renewable organic solvent film as a novel extracting phase: A combination of solid- and liquid-phase microextraction.

Comments

  1. SCardenasMarch 28, 2012 at 12:33 PM

    This miniaturized technique is very interesting. I would like to know its compatibility with liquid and gas chromatographic separations and your opinion on its potential applicability

    ReplyDelete
    Replies
    1. Microextraction TechMarch 28, 2012 at 1:50 PM

      First of all, thank you very much for follow this blog. Concerning you question, I think that the technique can be coupled with both liquid and gas chromatography. However, the low solvent volume may be a limitation in HPLC, from the sensitivity point of view. In summary, this hybrid microextraction seems to be useful in a wide range of analytical problems. I´m sure that the authors will solve these doubts in further communications.

      Delete
  2. Akshara desaiJune 20, 2015 at 3:50 AM

    Thanks for sharing such a nice information. You can also visit Precision Drawell website for Micro Silica Manufactures In India.

    ReplyDelete

Post a Comment

Popular posts from this blog

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

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

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