The progress of novel sorbents and their function in preconcentration techniques for determination of trace elements is a topic of great importance. This review discusses numerous analytical approaches including the preparation and practice of unique modification of solid-phase materials. The performance and main features of ion-imprinting polymers, carbon nanotubes, biosorbents, and nanoparticles are described, covering the period 2007-2012. The perspective and future developments in the use of these materials are illustrated.

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An easily performed, specific, sensitive, rapid, reliable and inexpensive procedure for the spectrofluorometric quantitation of ascorbic acid was proposed using acriflavine as a fluorescence quenching reagent. The procedure was based on the determined quenching effect of ascorbic acid on the natural fluorescence signal of acriflavine and the reaction between ascorbic acid and acriflavine in Britton-Robinson buffer solution (pH 6) to produce an ion-associated complex. The reduction in acriflavine fluorescence intensity was detected at 505 nm, while excitation occurred at 265 nm. The relationship between quenching fluorescence intensity (ΔF) and concentration of ascorbic acid was linear (R 2 = 0.9967) within the range 2-10 μg/ml and with a detection limit of 0.08 μg/ml. No significant interference was detected from other materials often found in pharmaceutical nutritional tablets. The obtained results were compared with those from high-performance liquid chromatography and appeared in good agreement, with no important differences in precision or accuracy. The proposed spectrofluorimetric method was used to determine the amount of ascorbic acid in a number of commercial pharmaceutical nutritional supplement tablets with a 95% confidence performance.

In the current study, poly(p-aminophenol) (PpAP), with starch and graphene oxide (GO), were successfully synthesised by oxidative polymerisation from p-aminophenol monomer in an aqueous alkaline medium using ammonium persulfate (APS) as an oxidising agent. The synthesised polymers were characterised using UV-Vis spectroscopy, Fourier transform infrared, thermogravimetric analysis, X-ray diffraction (XRD), and Brunauer-Emmett-Teller and zeta potential techniques. These techniques confirmed the presence of site-selective interaction between the conjugated PpAP chain and π-bonded surface, and thus the H-bonding of starch and GO. Further, the enhanced dye removal efficiency was ascribed to the improved morphology and the pore volume created by the entangled PpAP/Starch/GO. The influences of experimental conditions such as the polymer composite content, dye concentration, time, pH of the bath solution, and temperature on cationic dye adsorption were investigated. The adsorption data were fixed to the Langmuir isotherm (R 2 in the range between 0.997 and 0.9995) and showed a pseudo-second order (R 2 = in the range between 0.996 and 0.9996) kinetic model. Moreover, the polymer ternary composite was able to remove a large proportion (96.7%) of the cationic dye from water at pH 7. The thermodynamic investigation found that the adsorption process was spontaneous and endothermic. In addition, the synthesised adsorbent showed good reusability at six cycles. The data acquired suggest that the PpAP/Starch/GO composite can be effectively applied and reused as an inexpensive adsorbent material for removal of MB dye from water.

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