A sensitive method is proposed to determine antimony species using vortex-assisted ionic liquid-based liquid-phase microextraction and digital imaging colorimetry. SbIII forms a ternary complex with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol, ascorbic acid, and iodide in an acid medium. The acceptor phase consists of the ionic liquid 1-butyl-3-methylimidazole hexafluorophosphate, dispersed in the aqueous solution with a vortex stirrer. After centrifugation, SbIII was determined directly in the rich phase. SbV can also be measured by converting to reduced species. The method presented a limit of detection of 1.4 and 4.2 μg L-1 and an enrichment factor of 360. The precision (relative standard deviation) of the method is 7.0%. The procedure was applied to the speciation of antimony in river water and mineral water samples. Some results were compared with those obtained by electrothermal atomic absorption spectrometry (ET AAS). The method is an attractive alternative for determining antimony species, considering the aspects of green analytical chemistry.

The objective of this study was to develop a low-cost and eco-friendly adsorbent from agro-industrial waste for the removal of hexavalent chromium in the aqueous medium. The adsorbent (BMC) produced from yellow mombin (Spondias mombin L.) seeds was characterized by the determination of the chemical composition, thermal analysis (thermogravimetric (TG) analysis and differential thermal analysis (DTA)), Fourier transform infrared spectroscopy (FTIR), pH in suspension and determination of the point of zero charge (PZC). The presence of proteins, fats and carbohydrates (15.690, 1.004, and 73.706%, respectively) suggests that the material can be a promising adsorbent, given the availability of functional groups. The following conditions were set: pH 2.0, adsorbent mass 450 mg, and equilibrium was reached after 80 min. The maximum adsorption capacity was approximately 98%. Kinetic studies showed that the pseudo-second-order kinetic equation was the one that best adjusted to the experimental data. Under the conditions investigated, the Langmuir isotherm model described the best balance data, signaling the adsorption in monolayer. According to the results, it was found that the BMC showed an outstanding performance for the removal of CrVI ions and may become a viable and efficient alternative for the treatment of industrial effluents containing trace elements.

In the present paper, an automated online preconcentration system based on the use of two knotted reactors (KR) was developed for Mn determination in tea samples by flame atomic absorption spectrometry (F AAS). The system automation was performed by using four solenoid valves to switch sample streams and reagents. Valves were driven electronically by an integrated Darlington transistor circuit and controlled by an open-source Arduino hardware platform written in C language. The preconcentration was based on the precipitation process of metal ions complexed with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol (5-Br-PADAP) on the inner walls of the reactor, followed by elution with a solution of hydrochloric acid. The optimized system allowed the Mn determination with limit of detection (LOD) of 2.1 mg L-1, precision (relative standard deviation (RSD), 50.0 mg L-1) of 2.6% and enrichment factors of 8. The system presented a sampling frequency of 60 h-1. The method accuracy was evaluated by analysis of the certified reference material (CRM) apple leaves (NIST 1515) and by addition/recovery tests obtaining recoveries between 95.2 to 119%. This method was applied in the Mn determination in commercial tea samples purchased from local trade. Manganese levels were found in a concentration range of 2.95 to 123 µg g-1.

This study describes the preparation of a novel ion-imprinted polymer (IIP) to apply pre-concentration of cadmium ions in water samples of the Pontal Bay in Ilhéus, Brazil. First, cadmium ion was complexed with 2-(2-thiazolylazo)-p-cresol (TAC). Subsequently, there was the polymerization using ethylene glycol dimethacrylate and methacrylic acid monomers along with the radical azobisisobutyronitrile initiator. The mold ions were removed using 2:1 (v v-1) nitric acid. The thermal stability of the polymer was evaluated by thermogravimetry and the characterization was performed by Fourier transform infrared spectroscopy. The maximum adsorption capacity for IIP (qmax = 84.75 mg g-1) could be described by the Langmuir isotherm. The variables: sample flow rate, pH and eluent (nitric acid) were optimized using Box-Behnken design with determination by flame atomic absorption spectrometry (FAAS). The enrichment factor, as well as the limits of detection and quantification (LOQ), were found to be 44, 0.14 and 0.46 µg L-1, respectively. Selectivity was evaluated by using solutions containing CdII, CuII, NiII, PbII, CoII, SO42-, and Cl- ions. The concentration of cadmium ions in the samples varied between < LOQ to 1.25 µg L-1.

Este trabalho propõe a otimização multivariada de um procedimento para determinação de cádmio em amostras de chorume usando-se espectrometria de absorção atômica com chama após a extração em fase sólida usando-se uma minicoluna empacotada com Amberlite XAD-4 modificada com ácido 3,4-diidróxibenzoico. As variáveis relacionadas à pré-concentração (pH, razão de amostragem e concentração do tampão) foram otimizadas usando-se planejamento Doehlert. Duas ferramentas para modelagem estatística (regressão por mínimos quadrados e redes neurais artificiais) foram aplicadas aos dados e seus desempenhos foram comparados. Procedimentos de digestão do chorume por aquecimento em meio ácido e por radiação ultravioleta foram avaliados sendo este último mais adequado para evitar a perda de Cd por volatilização. O procedimento desenvolvido apresentou um fator de enriquecimento de 9 vezes com limites de detecção e de quantificação (3sb) de 0,72 e 2,4 µg L-1, respectivamente, e precisão - expressa como porcentagem do desvio padrão relativo - de 4,0 e 6,4% (RSD%, n = 4 para 5,0 e 20,0 µg L-1, respectivamente). Testes de adição/recuperação de Cd foram realizados obtendo-se valores entre 97 e 112%. O procedimento foi aplicado na determinação de cádmio em amostras de chorume coletadas no aterro sanitário do município de Jaguaquara-BA, Brasil.

This work proposes the use of multivariate optimization as a procedure for cadmium determination in leachate samples via flame atomic absorption spectrometry after solid phase extraction using a minicolumn packed with Amberlite XAD-4 modified with 3,4-dihydroxybenzoic acid. The variables related with the preconcentration (pH, sampling flow rate and buffer concentration) were optimized using Doehlert design. Two statistical modeling tools (least squares regression and artificial neural networks) have been applied to the data and their performances were compared. Digestion procedures of the leachate by heating in acid medium and ultraviolet radiation were evaluated being the latter more appropriate to prevent loss of Cd by volatilization. The developed procedure has promoted an enrichment factor of 9, with detection and quantification limits (3sb) of 0.72 and 2.4 µg L-1, respectively, and precision - expressed as relative standard deviation percentage - of 4.0 and 6.4% (RSD%, n = 4 for 5.0 and 20.0 µg L-1, respectively). Addition/recovery tests for Cd were carried out and values between 97 and 112% were obtained. The procedure was applied for cadmium determination in leachate samples collected at the sanitary landfill of Jaguaquara-BA, Brazil.

Desenvolveu-se um procedimento para determinação de cobre, ferro, chumbo e zinco em amostras de gasolina. O procedimento foi baseado na pré-concentração dos metais empregando uma resina modificada com o ácido 3,4-dihidroxibenzóico (XAD-DHB), seguida da dessorção com solução ácida. Os analitos no eluato foram determinados por espectrometria de absorção atômica em chama multielementar seqüencial (FS-FAAS). As amostras de gasolina foram preparadas como microemulsões misturando-se 80 mL de amostra com 17 mL de propan-1-ol e 3 mL de solução tampão (pH 10). As variáveis físico-químicas que influenciam no processo de extração foram otimizadas. Os LODs obtidos foram 2,2 µg L-1 para Fe, 3,1 µg L-1 para Cu, 2,3 µg L-1 para Pb, e 2,6 µg L-1 para Zn. Os valores de RSDs das concentrações dos analitos nas amostras enriquecidas com 0,05 e 0,1 mg L-1 de cada metal variaram de 5,8 a 9,7%. As recuperações variaram de 82 a 99%. O método foi aplicado na determinação dos analitos em níveis de µg L-1 em amostras de gasolinas coletadas em postos revendedores de Salvador, BA, Brasil.

A procedure was developed for determination of copper, iron, lead and zinc in gasoline. The procedure was based on the preconcentration of metals using a resin modified with 3,4-dihydroxybenzoic acid (XAD-DHB), followed by desorption with an acid eluent. The components in the eluate were then determined by fast sequence flame atomic absorption spectrometry (FS-FAAS). The gasoline samples were prepared as microemulsions by mixing 80 mL of sample with 17 mL of propan-1-ol and 3 mL of a buffer solution (pH 10). The chemical and physical variables influencing the extraction were optimized. The LODs obtained were 2.2 µg L-1 Fe, 3.1 µg L-1 Cu, 2.3 µg L-1 Pb and 2.6 µg L-1 Zn. The RSDs ranged from 5.8 to 9.7% in samples spiked with 0.05 and 0.1 mg L-1 of each metal and recoveries varied from 82 to 99%. The procedure was suitable for determination of the analytes at µg L-1 levels in gasoline samples collected from several gas stations in Salvador, State of Bahia, Brazil.

Um procedimento automatizado foi desenvolvido para determinação de quantidades traços de manganês provenientes de folhas de vegetais e águas de rio utilizando espectrometria de absorção atômica com chama (FAAS) após a pré-concentração em linha deste metal usando uma minicoluna de Amberlite XAD-4 modificada com 2-aminotiofenol. O sistema de pré-concentração baseia-se na extração em fase sólida do metal na minicoluna e eluição com ácido clorídrico 0,30 mol L-1, seguido de sua determinação. As variáveis associadas ao desempenho do sistema de pré-concentração, tais como, pH, vazão de amostragem e concentração do eluente foram otimizadas utilizando um simplex básico como técnica multivariada. O método desenvolvido gerou um fator de enriquecimento de 14 vezes atingindo um limite de detecção (3 σB) de 2,0 µg L-1 e precisão expressa como desvio padrão relativo de 2,2% (%RSD, n = 10; 30,00 µg L-1). O procedimento foi aplicado para a determinação de manganês em águas de rio coletada na área urbana de Jequié/Bahia. A exatidão do procedimento foi verificada usando-se materiais de referência certificados (folhas de macieira, NIST 1515 e folhas de espinafre, NIST 1570). O procedimento desenvolvido foi aplicado para a determinação de manganês em folhas de vegetais (cebolinha, espinafre, couve-flor e repolho).

An automated procedure was developed to determine trace amounts of manganese from vegetal leaves and river waters using flame atomic absorption spectrometry (FAAS) after online preconcentration of this metal using an Amberlite XAD-4 minicolumn modified with 2-aminothiophenol. The preconcentration system is based on the solid-phase extraction of the metal into the minicolumn and elution with 0.30 mol L-1 hydrochloric acid, followed by its determination. Variables associated with the preconcentration system performance, such as pH, sampling flow rate and eluent concentration were optimized using a basic simplex as multivariate technique. The developed method provides an improvement factor of 14 along with limit of detection (3σB) of 2.0 µg L-1, and precision expressed as a 2.2% relative standard deviation (RSD%, n = 10, 30.0 µg L-1). The procedure was applied to determine manganese in river waters collected from urban area of Jequié/Bahia. The accuracy of the procedure was checked by analysis of two certified reference materials (apple leaves, NIST 1515 and spinach leaves, NIST 1570). The developed procedure has been applied for manganese determination in vegetal leaves (chive, spinach, cauliflower and cabbage).

Neste trabalho, é proposto um novo método para a determinação de cobre, utilizando extração em ponto-nuvem. O reagente 2-[2´-(6-metil-benzotiazolilazo)]-4-bromofenol (Me-BTABr) foi usado como agente complexante e Triton X-114 foi adicionado como surfactante. Após a separação das fases, foi promovida a diluição da fase rica em surfactante com metanol acidificado, e o teor de cobre medido por Espectrometria de Absorção Atômica com chama. O procedimento proposto viabilizou a determinação de cobre com um limite de detecção de 1,08 µg L-1. O procedimento foi validado por meio da análise de material de referência certificado. O método foi aplicado com sucesso à determinação de cobre, em amostras de água de rio e poço.

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.