This review, with more than 170 references, presents a general overview of the use of magnetic nanoparticles (MNPs) to perform sample preparation. In this way, the main types of MNPs used for this purpose, such as magnetic molecularly imprinted polymer (MMIP), noble metal coated MNPs, carbon nanotubes (CNTs), quantum dots (QDs), silica, and surfactant are described in terms of their composition, properties, and synergetic potential. Finally, some examples of their analytical applications are reported, as well as pointing out possible future applications of MNPs in the analytical field.
A simple and rapid methodology to separate and characterize gold nanoparticles (AuNPs) in aqueous medium by capillary electrophoresis-evaporative light scattering detection (CE-ELSD) is presented.First, a controlled synthesis procedure to obtain water-soluble AuNPs, by varying the trisodium citrate concentration was described. These free AuNPs were separated by capillary zone electrophoresis (CZE) based on the differences in the charge-to-mass ratio of the AuNPscitrate in a mixed buffer of ammonium acetate (20 mM), containing tris(hydroxymethyl)-aminomethane (Tris, 20 mM) and 3-(cyclohexylamino)-1-propanesulfonic acid (CAPS; 10 mM) at pH 8.5.Under optimal working conditions, three small different-sized AuNPs were successfully separated whose average sizes were 3.5, 6.5 and 10.5 nm. The average diameter was lower than 1.2 nm for all of them (calculated by high-resolution transmission electron microscopy, TEM). Thus, this CE-based method was able to separate AuNPs that differ by only 3 nm in diameter. It can be a valuable methodology for the rapid and cost-effective characterization of other nanomaterials in the future in aqueous solutions.
A magnetic material based on N-methylimidazolium ionic liquid and Fe(3)O(4) magnetic nanoparticles incorporated in a silica matrix has been used to extract and preconcentrate sulfonylurea herbicides, such as thifensulfuron methyl (TSM), metsulfuron methyl (MSM), triasulfuron (TS), tribenuron methyl (TBM) and primisulfuron methyl (PSM) from polluted water samples, prior to their analysis by capillary liquid chromatography with a diode array detector (DAD). Under the optimum conditions, this method allows the determination of TSM, MSM, TS, TBM and PSM in a linear range between 5 and 100 ng mL(-1), with relative standard deviation values lower than 5.3% (n = 10), in all cases. Detection limits ranging between 1.13 and 2.95 ng mL(-1) were achieved. The usefulness of the proposed method was demonstrated by the analysis of river water samples, obtaining recoveries higher than 91%.
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