This work describes the synthesis and characterization of 2-aminothiazole-modified silica gel (SiAT), as well as its application for preconcentration (in batch and column technique) of Cu(II), Ni(II) and Zn(II) in ethanol medium. The adsorption capacities of SiAT determined for each metal ion were (mmol g(-1)): Cu(II)=1.20, Ni(II)=1.10 and Zn(II)=0.90. In addition, results obtained in flow experiments, showed a recovery of ca. 100% of the metal ions adsorbed in a column packed with 500 mg of SiAT. The eluent was 2.0 mol L(-1) HCl. The sorption-desorption of the studied metal ions made possible the development of a preconcentration method for metal ions at trace level in fuel ethanol using flame AAS for their quantification.

In the present study, a simple, rapid and sensitive method was developed for the determination of mercury concentrations in the muscle tissue of fish from the Brazilian Amazon using graphite furnace atomic absorption spectrometry (GFAAS) following acid mineralization of the samples in an ultrasonic cold water bath. Using copper nitrate as a chemical modifier in solution and sodium tungstate as permanent modifier, we were able to attain thermal stabilization of the mercury up to the atomisation temperature of 1600 °C in the GFAAS assay. The calculated limits of detection (LOD) and quantification (LOQ) were 0.014 and 0.047 mg kg(-1), respectively.

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Heavy metals (e.g., Cd, Cu, Hg, Pb) at trace levels are proven toxic elements and can be the cause of human health disorders. 1,2 Because the main sources of these metals for humans are water and food, monitoring the heavy metal content in natural waters is of paramount importance.The cadmium contamination in environmental samples is generally lower than 5 ng mL -1 , so very sensitive techniques are required for determinations. Several analytical techniques exist for determining trace levels of cadmium. 3,4 Flow injection preconcentration techniques are useful for application in determining heavy metal ions by flame absorption atomic spectrometry (FAAS), providing a superior performance because they allow for the enhancement of sensitivity, separation of the analyte from the matrix and reduction of the risk of contamination. [5][6][7][8] The Cd 2+ preconcentration with solid phase extraction (SPE) technique using highly selective sorbentpacked columns has been described elsewhere.9-11 Compatible detection limits were obtained by the SPE technique.In recent years, the use of chemically modified silica gel matrixes with attached groups having a selective affinity for metal ions has been described. [12][13][14][15] A manual procedure with this sorbent-packed column has been proposed for Cd preconcentration. 12,15 However, the routine application of this procedure is limited by the time necessary for each analysis (100 min for each determination).This work describes the analytical performance of a flow injection system with online preconcentration on a sorbent minicolumn packed with 2-aminothiazole-modified silica gel (SiAT) for determining Cd in a series of river water samples. The material was initially tested with a synthetic aqueous solution containing Cd 2+ ; after that it was used in real samples. ExperimentalReagents, analytical solutions and samples All the solutions were prepared with high purity chemicals and distilled-deionized water (Milli-Q system, Millipore). The hydrochloric and nitric acids used were of the brand Suprapur quality (Merck).Cadmium standard solutions (5 -50 µg L -1 ) were prepared by stepwise dilution from a 1000 mg L -1 stock solution (Merck Titrisol) with Milli-Q treated water, acidified with nitric acid to pH 2.The mini-column (a 5 cm long, 3 mm i.d. glass tube) was drypacked with 100 mg of SiAT.Samples of river water (Tietê, Parapanema and Parana rivers, SP, Brazil) were collected and immediately filtered through a 0.45 µm membrane. After acidification (pH < 2.0) with 6.0 mol L -1 HNO3 solution, the samples were stored in highly purified PE containers. Aliquots of 100 mL of the water samples were digested by oxidation with UV-photolysis in the presence of 0.01% of H2O2, using a low-pressure Hg-lamp integrated to a closed quartz vessel. 17The aqueous extract resulting was poured into a 100 mL volumetric flask and this solution was diluted to the final volume with deionized water. Imperatriz, MA, Brasil A rapid and sensitive method was developed to determine trace levels of Cd 2+...