Microextraction Tech

Microextraction is currently present in many analytical processes. Its advantages over conventional extraction approaches have been extensively pointed out and mainly refer to its simplicity and miniaturization while providing equal or even better analytical features. Also, the availability of the sorbents (carbon-based, silica, metallic, magnetic...), formats (fiber, capillary, powder, particles and membranes) and combinations among them make possible the processing of any sample-analyte binomial. A step forward in the development of novel sorbents phases is selectivity. Highly selective extractant allows to face the determination of the analytes in complex matrices such as biological fluids or food. Nickel foam The group of Prof. Zhang has proposed the synthesis and evaluation of molecularly imprinted polymers (MIPs) that allows the selective extraction of floxacin from water and biological samples. We are all aware about the ability of such polymeric phases to selective rec...

If you are interested in green analytical chemistry, this is an article for you. Researchers from the Wuhan University at China have recently proposed the use of pollen grains as sorbent in hydrophilic interaction solid phase extraction (1). These grains are characterized by a high superficial area (close to 20 m2/g), a high hydrophilic surface due to the presence of residual hydroxyl groups and particle size in the medium micrometer range. The selection of the proper variety of pollen to be used for analytical purposes is a critical issue according to the authors. They prefer pine pollen to bee pollen grains since the first one is more homogeneous from the chemical point of view and therefore it leads to more reproducible results. In addition, this type of pollen is available at higher amounts allowing the fabrication of many extraction cartridges for sample extraction. Figure 1. Pollen from a variety of common plants (Public domain image from wikipedia) Pollen grains cannot...

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...

Microextraction techniques can be considered within the Green Chemistry framework as they reduce the amount of materials and organic solvents required for the development of an analytical methodology. This green character is more marked when the microextraction technique is employed to the resolution of an environmental analytical problem. This post is focused on another green concern: the use of wastes for the fabrication of sorbent materials for analytical purposes. Researchers from the Federal University of Rio Grande do Sul (Brazil) have already proposed, in an article published in Journal of Hazardous Materials , the use of coffee grounds and eucalyptus sawdust for the preparation of activated carbon. According to the authors, these agro-industrial wastes are quite problematic since their natural degradation favors the proliferation of some harmful microorganisms. The synthesis of the activated carbon just involves various simple processes. First of all, the coffee grounds an...

Zinc oxide has been used as coating in solid phase microextraction (SPME) due to its good properties including thermal stability and affinity towards different analytes. In this sense, ZnO presents a high interaction with sulfur-containing molecules due to the strong coordination between Zn and S. However, this interaction is not completely exploited in SPME since pure ZnO coatings, prepared by sol-gel procedures, have a low surface area due to the enwrapping of ZnO nanoparticles (NPs) in the sol-gel network. In a recent article accepted for publication in Journal of Chromatography A, researchers from the Sun Ya-sen University at China have proposed a new approach to avoid this shortcoming. The proposal consists of the use of graphene as ZnO NPs support. The ZnO NPs are grown in the graphene (G) surface producing a composite which is final attached to a silica fiber by a sol-gel reaction in order to prepare the SPME coating. The whole synthetic procedure is described in detai...

Inside needle capillary microextraction (INCAT) is a promising solid phase microextraction (SPME) mode where the sorbent material is immobilized in the inner walls of a hollow stainless steel needle allowing the continuous sample flow through the extracting phase. Therefore, INCAT enhances the kinetic of the extractions and improves the preconcentration factors since larger sample volumes can be processed. Moreover, the extraction device is inexpensive, robust and it presents a higher mechanical stability compared to classic SPME fibers. Although conventional SPME materials can be employed as extracting phases in INCAT, new materials have been developed in this context. Bagher at al. have already described, in a research article published in the Journal of Separation Science, a nanocomposite for the extraction of polycyclic aromatic hydrocarbons in water (1). The nanocomposite is based on the combination of hexagonally ordered silica (SBA-15) and polyaniline, each component pl...

Zinc oxide (ZnO) nanoparticles have been successfully employed in different application fields due to their inherent characteristics such as wide band-gap or thermal stability. As with other nanomaterials, zinc oxide may exist in many structural forms depending on the synthetic process. In this sense, ZnO nanorods can be easily obtained in the laboratory by a hydrothermal treatment using zinc nitrate and hexamethylenetetramine as precursors. The concentrations of the precursors, as well as the temperature and incubation time, play a key role in the final physical characteristics of the product as it is indicated in Figure 1. Figure 1A shows a scanning electron micrograph of the ZnO nanoparticles before the hydrothermal reaction while Figures 1B-C illustrate the final product using different starting equimolar concentrations of the precursors (0.1 mM, 1mM and 10 mM, respectively). The average width and length of the nanorods increase with the initial concentration of precursors. H...

Cigarette filters (CFs) are employed to reduce the amount of smoke and toxic substances (tar and particulate matter) inhaled during smoking. Commercial filters usually consist on a large number of cellulose acetate fibers which act as particulate sieves as well as contaminant traps. The latter aspect, based on the chemical interaction of CFs with different organic substances, permits their use as sorptive phase in solid phase extraction (SPE). The first application of CFs in this context was published by Yan et al. in 2003 for the determination of traces of methylmercury by electrothermal atomic absorption spectrometry (ETAAS).

The usefulness of sorptive microextraction approaches, like solid phase microextraction (SPME) or stir bar sorptive extraction (SBSE), in the isolation and preconcentration of organic pollutants from water is well established in the scientific literature. Classic SPME or SBSE are mainly focused on the extraction of non-polar compounds since the typical coating, polydimethlysiloxane (PDMS), is hydrophobic. While the main pollutants considered 20 years ago had a hydrophobic nature, most of the emerging contaminants present a medium to high polarity. Therefore, new sorptive phases are desirable in order to extend the scope of these extraction techniques.