In this study, we propose a microextraction method for the determination of CdII in produced waters. The process is based on the conversion of CdII ions into a hydrophobic diethyldithiocarbamate (DDTC) complex with its subsequent dispersive liquid phase microextraction (DLPME) from the aqueous medium with chloroform. The organic phase was then diluted with ethanol and Cd absorbance was measured by graphite furnace atomic absorption spectrometry (GF AAS). The experimental conditions related to the DLPME process were investigated, and the best microextraction conditions were achieved at pH = 6.0 (acetate buffer), 7.5 × 10-6 mol L-1 of DDTC, and when using 200 µL of chloroform as the extracting solvent. No dispersing solvent was needed, which allowed the recovery of approximately 140 µL of chloroform extract. Pyrolysis and atomization temperatures of the GF AAS program were determined through the construction of the respective curves. The estimated limits of detection (LOD) and quantification (LOQ) were 5 and 17 ng L-1, respectively, whereas the enrichment factor for the method was 17. Six samples of seawater and five samples of produced waters with salinities between 30 and 270‰ were analyzed as well as two certified reference materials of saline waters.

This work reports the development of a simple and fast method for the spectrophotometric determination of Fe in diesel oil using the classic reaction with 1,10-phenanthroline after its extraction induced by emulsion breaking (EIEB). The extraction parameters of EIEB were optimized (concentration of HNO3 and Triton X-100® in the emulsifying solution) as well as the adjustment of the pH of the final solution, a necessary step to complete the colorimetric reaction. The developed method presented a limit of detection of 0.004 mg L-1 and a limit of quantification of 0.013 mg L-1 and was applied in the analysis of six samples of diesel oil with different specifications. The results were statistically similar to those obtained by graphite furnace atomic absorption spectrometry (GF AAS). A recovery test was also performed by spiking the samples with 1.0 mg L-1 of Fe in the form of an organometallic compound, yielding recovery percentages between 83 and 108%.

Cadmium is considered a potentially toxic element, since it doesn't perform any biological function and is highly cumulative. This element is usually found in environmental samples in very low concentrations. For this reason, there is a necessity to develop methods that allow sufficiently low detection limits. From this perspective, a simple, sensitive, selective and low cost methodology was developed for the determination of Cd by F AAS. The system involves the on-line pre concentration of cadmium onto a commercial polystyrene divinil benzene (PSDV) resin modified with phenylfluorone (PF). The experimental conditions (both chemical and physical) were optimized to achieve highest sensitivity. The modified resin had high chemical and physical resistance, and could be reused for 300 cycles without compromising the system's sensitivity. The obtained enrichment factor was around 8 times and accuracy, calculated as relative standard deviation (RSD), of 5.5% for cadmium concentration of 40 µg L-1. The limits of detection and quantification obtained were 0.15 and 0.49 µg L-1, respectively. This methodology proved to be applicable for samples of river waters, in which matrix interferences were not observed. In these samples recovery tests were conducted in order to evaluate the accuracy of the method, and these results varied between 89 and 118%.

This aim of this work was to compare two methods for copper determination in insulating oils from power transformers by GFAAS. The first method was extraction induced by emulsion breaking, which determined the preconcentration of copper in an aqueous solution and exhibited a limit of quantification of 0.27 µg L-1. Also, a second method based on the direct introduction of samples into GFAAS in the form of detergent emulsions, prepared with Triton X-114 and HNO3, was investigated. In this case, the limit of quantification was 1.7 µg L-1. Seven samples of used oils were successfully analyzed by both methods.

Este trabalho descreve o desenvolvimento de uma metodologia para a pré-concentração seletiva de Cu(II) usando espuma de poliuretano (PUF) como suporte e o negro de eriocromo T (EBT) como ligante. A extração quantitativa do Cu(II) foi obtida em um meio contendo 60 mg L-1 de EBT e pH 1,5 (ajustado com solução de HCl). O tempo mínimo para extração do Cu(II) foi de 30 min quando 200 mg de PUF foram agitados com 100 mL de amostra. A dessorção do Cu(II) retido na fase sólida pode ser obtida apenas quando a PUF carregada com o analito foi digerida em forno de microondas na presença de HNO3 concentrado (15 min, 600 W). O método foi aplicado na determinação de Cu(II) em águas por espectrometria de absorção atômica com chama. Testes de recuperação foram realizados pela adição de 20 e 100 µg L-1 de Cu(II) sendo observadas recuperações entre 99,4 e 107%.

This work reports the development of a methodology for the selective preconcentration of Cu(II) onto polyurethane foam (PUF) using the Eriochrome Black T (EBT) as ligand. The quantitative extraction of Cu(II) was achieved in a medium containing 60 mg L-1 of EBT and pH 1.5 (adjusted with HCl solution). The minimum time required to obtain total extraction of Cu(II) from solution was 30 min, when 200 mg of PUF were stirred with 100 mL of the samples. The recovery of Cu(II) from the solid-phase only could be performed by digesting the loaded PUF with concentrated HNO3 in a microwave oven (15 min, 600 W). The method was applied for the determination of trace concentrations of Cu(II) in waters by flame atomic absorption spectrometry. A recovery test was performed by spiking of the samples with 20 and 100 µg L-1 of Cu(II) and recovery percentages of 99.4-107% were obtained.

This paper reports the evaluation of extraction strategies for the treatment of medicine samples to determine chromium and nickel by GFAAS. Different approaches for extraction were evaluated and the most efficient involved magnetic stirring. The metals were quantitatively extracted by stirring 0.20 g samples with 25 mL of 2.0 mol L-1 HCl solution for 60 min. The developed method was successfully applied for the determination of Cr and Ni in tablets containing antibiotics and raw materials, with cephalexin and ciprofloxacin as active ingredients.

This work proposes a new simple and fast spectrophotometric method for cephalexin determination in pharmaceutical formulations. The method is based on the charge transfer reaction between cephalexin and quinalizarin in dimethylsulfoxide medium. Several analytical parameters related to the system were optimized and the reaction was characterized in terms of stoichiometry. Also, association constant and apparent molar absorptivity of the product were determined. The method presented a limit of detection of 0.46 mg L-1 and a quantification limit of 1.5 mg L-1. It was successfully applied in the determination of cephalexin in two samples of commercial pharmaceutical formulations.

Neste trabalho é proposto um novo método para a determinação espectrofotométrica simples e rápida de azitromicina em formulações farmacêuticas. O método está baseado na reação de transferência de carga entre a azitromicina e a quinalizarina em meio de metanol. O efeito de diversas variáveis foi avaliado com o intuito de alcançar máxima sensibilidade analítica. A reação de transferência de carga foi caracterizada, sendo determinadas a estequiometria da reação, a absortividade molar aparente e a constante de associação. Melhores resultados foram obtidos em meio de metanol e com uma concentração de quinalizarina de 50 mg L-1. Nestas condições, o ânion radicalar (produto da reação de transferência de carga) foi formado imediatamente após a mistura dos reagentes, apresentando máxima absorção em 564 nm. O método apresentou um limite de detecção de 0,35 mg L-1 e um limite de quantificação de 1,2 mg L-1, sendo aplicado com sucesso na determinação de azitromicina em três amostras de medicamentos comerciais contendo azitromicina.

This paper proposes a new method for simple and fast spectrophotometric determination of azithromycin in pharmaceutical formulations. The method is based on the charge transfer reaction between the azithromycin and quinalizarin in methanol medium. In order to achieve maximum sensitivity the effect of some chemical variables such as the type of solvent, reagent concentration and reaction time were evaluated. The reaction was characterized in terms of stability of the product formed and its stoichiometry, and the apparent molar absorptivity and association constant were derived. Best conditions for the analytical determination of azithromycin were observed in methanol medium with a quinalizarin concentration of 50 mg L-1. At these conditions, the radical anion (absorbing specie) was formed in the medium immediately after mixing of the reagents and showed maximum absorption at 564 nm. The method presented a limit of detection of 0.35 mg L-1 and a limit of quantification of 1.2 mg L-1. It was successfully applied in the determination of azithromycin in three commercial pharmaceutical formulations of azithromycin and no matrix interferences were observed.

This work presents a detailed study about the sorption of crystal violet (CV) cationic dye onto polyether type polyurethane foam (PUF). The sorption process was based on the formation of an ionic-pair between cationic dye and dodecylsulfate anion (SDS), which presented high affinity by PUF. Set-up employed in the study was built up by adjusting a 200 mg cylinder of PUF to the arm of an overhead stirrer. The system was characterized in relation to equilibrium and kinetic aspects and it was modeled by employing Langmuir and Freundlich isotherms. Obtained results showed that the ratio between SDS and MB concentrations played an important role on the sorption process. According to results found it was possible to retain up to 3.4 mg of dye from 200 mL of a 5.0 x 10-5 mol L-1 CV solution containing 1.25 x 10-4 mol L-1 SDS, which represented a removal efficiency of around 92%.

Este trabalho apresenta um método para a determinação de chumbo por ETAAS, baseado na amostragem sólida da espuma de poliuretano impregnada com o reagente 2-(2-tiazolilazo)-p-cresol (TAC) previamente utilizada para extrair o íon metálico da solução amostra. O processo de extração ocorreu em pH 10, tamponado com sistema borato, após 40 min de agitação das fases sólida e líquida. Os resultados obtidos mostraram a fácil eliminação da matriz do tubo de grafite, utilizando como pirólise a temperatura de 600 ºC, sem a adição de modificador químico de matriz. O método desenvolvido foi validado através da análise de materiais certificados de referência (amostras biológicas) e através de testes de recuperação em amostras salinas.

This work presents a method for lead determination by ETAAS, based on solid sampling of polyurethane foam (PUF) impregnated with the reagent 2-(2-thiazolylazo)-p-cresol (TAC) previously utilized to extract the metallic ion from sample solution. The extraction process occurred in a medium buffered in pH 10 with borate system, after 40 min of agitation between the solid and liquid phases. The obtained results showed the easily elimination of the matrix from the graphite tube by a pyrolysis step at 600 ºC, without using of any matrix modifier. The method was validated by analysis of certified materials (biological samples) and by using recovery tests employing saline samples.

Neste trabalho é apresentado um estudo referente à sorção do complexo cobre-dietilditiocarbamato, empregando espuma de poliuretano (EPU) como fase sólida. Foi observado que em pH 6,8 e na presença de DDTC 4,5 x 10-5 mol L-1 a sorção de Cu(II) (80 ou 150 µg L-1) foi máxima. O tempo requerido para que o equilíbrio fosse alcançado foi de 40 min. A partir dos dados deste experimento foi realizada uma caracterização cinética através da aplicação de três modelos, que revelaram que a difusão do complexo na interface entre sólido-líquido foi a etapa determinante na velocidade do processo sortivo. Pôde-se também afirmar que a sorção do complexo se dá através de um mecanismo similar aquele observado em extração líquido-líquido, usando éter como solvente. Testes com possíveis interferentes demonstraram a relativa seletividade da extração do complexo metálico, que pode ser melhorada com a presença de um agente mascarante adequado.

This paper presents a study about the sorption of copper-diethyldithiocarbamate complex onto polyurethane foam (PUF). It was observed that the maximum sorption of Cu(II) (80 or 150 µg L-1) was verified at pH 6.8 in presence of 4.5 x 10-5 mol L-1 DDTC. The shaking time needed to achieve the equilibrium was 40 minutes. From these data, a kinetic characterization was performed by applying three models, which revealed that a film diffusion process was a rate-determining mechanism. Results also indicated that a ether-like solvent extraction was the sorption mechanism. The investigation of many metallic ions as concomitants showed that the sorption by foam is relatively selective and it can be enhanced by using a suitable masking agent or incrementing the foam mass.