Juracir Silva Santos

Uranium determination using atomic spectrometric techniques: an overview.

This review focuses on the determination of uranium using spectroanalytical techniques that are aimed at total determination such as flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma optical emission spectrometry (ICP-OES); and inductively coupled plasma mass spectrometry (ICP-MS) that also enables the determination of uranium isotopes. The advantages and shortcomings related to interferences, precision, accuracy, sample type and equipment employed in the analysis are taken into account, as well as the complexity and costs (i.e., acquisition, operation and maintenance) associated with each of the techniques. Strategies to improve their performance that employ separation and/or preconcentration steps are considered, with an emphasis given to solid-phase extraction because of its advantages compared to other preconcentration procedures.

Me-BTABr reagent in cloud point extraction for spectrometric determination of copper in water samples

A new preconcentration method using cloud point approach is proposed for copper determination. The reagent 2-[2´-(6-methyl-benzothiazolylazo)]-4-bromophenol (Me-BTABr) was used as a complexing agent and Triton X-114 was added as a surfactant. After phase separation, dilution of the surfactant-rich phase with acidified methanol was performed, and the copper content was measured by flame atomic absorption spectrometry. The proposed procedure allowed the determination of copper with detection limit of 1.08 µg L-1. The validation of the procedure was carried out by analysis of certified reference material. The method was successfully applied to copper determination in river and well water samples.

A new functionalized resin and its application in preconcentration system with multivariate optimization for nickel determination in food samples.

In this work, Amberlite XAD-2 resin functionalized with 4,5-dihydroxy-1,3-benzenedisulfonic acid was synthesized, characterized and applied as a new packing material for an on-line system to nickel preconcentration. The method is based on the sorption of Ni(II) ions in a minicolumn containing the synthesized resin, posterior desorption using an acid solution and measurement of the nickel by spectrophotometry (PAR method). The optimization of the system was performed using factorial design and Doehlert matrix considering five variables: eluent concentration, PAR solution pH, sample flow rate, PAR solution concentration and sample pH. Signals were measured as peak height by using an instrument software. Using the experimental conditions defined in the optimization, the method allowed nickel determination with achieved sampling rate of 25 samples per hour, detection limit (3s) of 2microgl(-1) and precision (assessed as the relative standard deviation) of 8.2-2.6%, for nickel solutions of 10.0-200.0microgl(-1) concentration, respectively. The experimental enrichment factor of the proposed system was 46, for 120s preconcentration time. The proposed procedure was applied for nickel determination in food samples. Recoveries of spike additions (5 or 10microgg(-1)) to food samples were quantitative (94-110%).

Synthesis and Application of a New Functionalized Resin in On‐Line Preconcentration of Lead

Abstract An on‐line system for preconcentration and determination of lead at µg L−1 level is proposed. Amberlite XAD‐2 functionalized with 2‐(2′‐benzothiazolylazo)‐p‐cresol (BTAC‐XAD) packed in a minicolumn was used as sorbent. Chemical and hydrodynamic variables were evaluated and the results demonstrated that lead can be determined using sample pH at 7.0–7.5, elution with 0.050 mol L−1 HCl and a sample flow rate of 6.0 mL min−1. Enrichment factors of 19, 43, and 60 were achieved by using the time‐based technique with preconcentration periods of 60, 120, and 180 s, respectively. Detection limit (3s) was 1.7 µg L−1 when used preconcentration time of 180 s. This procedure was applied to lead determination in natural water samples. Accuracy of procedure was confirmed by lead determination in certified reference materials.

Determination of lead in water samples after its separation and preconcentration by 4,5-dihydroxy-1,3-benzenedisulfonic acid functionalised polyurethane foam

A new sorbent based on polyurethane foam functionalised with 4,5-dihydroxy-1,3-benzenedisulfonic acid (Tiron-PUF) was synthesised. This material was used in the development of a procedure for preconcentration of lead, with subsequent detection by flame atomic absorption spectrometry (FAAS). The influence of some variables involved in the extraction process was studied. Analytical parameters were evaluated using 50 and 500 mL of Pb (II) solution. Under optimum conditions, the system showed enrichment factors of 38 (50 mL) and 114 (500 mL). The detection limits obtained were 0.5 and 1.1 µg L−1 when volumes of 500 and 50 mL of Pb (II), respectively, were used. The method was applied to the determination of lead content in well water and drinking water samples collected in the town of Amelia Rodrigues, Bahia, Brazil.