Meglumine antimoniate (MA) is a pentavalent antimony (SbV) drug recommended for the treatment of leishmaniasis. It is known that the trivalent antimony (SbIII) present as a residue in MA contributes to the drug side effects. In this article, multivariate optimization was used in the synthesis of MA in order to obtain a drug with low levels of SbIII. Four variables (source of antimony, temperature, water volume and pH) were preliminarily evaluated by 24-1 fractional factorial design. Central composite design (CCD) was used to determine the optimal synthesis conditions, using two different sources of SbV and the significant variables selected in a fractional factorial design. Response surface methodology obtained by CCD provided a model with non-significant regression (p = 0.05) for the synthetic route via KSb(OH)6. On the other hand, synthetic route via SbCl5 reached minimum value of SbIII content of 0.172% and significant regression, and it was selected for further evaluations. The analysis of MA formulations synthesized with SbCl5 under optimized conditions revealed the efficiency of multivariate optimization to reduce SbIII content. In addition, the monitoring of some physicochemical parameters of these formulations maintained at 40 ºC for 90 days, showed that stability was not altered at 95% confidence level.

This study proposes a procedure for speciation of antimony by hydride generation atomic absorption spectrometry in pentavalent antimony drugs. The SbIII content was determined by selective generation of SbH3 in medium with higher SbV concentration using 4 to 20-fold lower citric acid solutions than recommended in the available literature. The multivariate optimization of the methods was performed through factorial design followed by a central composite design (CCD). The limit of detection (LOD) and limit of quantification (LOQ) were calculated at 0.15 and 0.05 µg L-1 and 0.48 and 0.17 µg L-1, for total Sb and SbIII, respectively. The relative standard deviation (RSD) values ranged from 3.1 to 19.6% and 9.1 to 20.1%, while recovery ranged from 95.6 to 102.3% and 89.1 to 108.1%, for total Sb and SbIII, respectively. This method was applied for the analysis of meglumine antimoniate samples. Total Sb and SbIII concentrations ranged from 79.2 to 101.1 mg mL-1 and 0.08 to 0.41 mg mL-1, respectively.

O objetivo deste trabalho foi desenvolver um método para a determinação simultânea de Na, K e Ca em amostras de biodiesel por espectrometria de emissão atômica em chama, utilizando um detector de radiação eletromagnética contínua. Dois procedimentos foram utilizados para o preparo das amostras de biodiesel: diluição direta com querosene e emulsificação da amostra usando uma solução aquosa composta por HNO3, n-butanol e Triton X-100. A metodologia proposta apresentou boa linearidade, desvios padrão relativos menores que 5% e limites de quantificação de 0,05 e 0,02 mg kg–1 para Na e K, respectivamente, empregando emulsão ou diluição com solvente. Para Ca, o limite de quantificação foi de 0,2 e 1,0 mg kg–1, aplicando-se diluição direta com solvente e emulsão, respectivamente. O procedimento de emulsificação não sofreu influência da matriz quando foram realizados testes de recuperação (89-108%). A metodologia de referência (ABNT NBR 15553) foi utilizada para verificar a exatidão do método proposto, apresentando resultados consistentes ao nível de confiança de 95%, sendo apropriado para análises de rotina de amostras de biodiesel de diferentes oleaginosas.

This work aimed to develop a methodology for simultaneous determination of Na, K and Ca in biodiesel samples by flame atomic emission spectrometry, using a continuous electromagnetic radiation detector. Two procedures were employed for biodiesel sample preparation: direct dilution with kerosene and sample emulsification with HNO3, n-butanol and Triton X-100. The proposed methodology presented good linearity, relative standard deviations less than 5% and limits of quantification of 0.05 and 0.02 mg kg–1 for Na and K, respectively, using emulsification and solvent dilution. For Ca, the limit of quantification was 0.2 and 1.0 mg kg–1, applying direct dilution and emulsion, respectively. The emulsification procedure showed no matrix influence when recovery tests were performed (89-108%). Reference methodology (ABNT NBR 15553) was used to check the accuracy, presented consistent results at 95% confidence level, being suitable for biodiesel samples in a routine analysis.

Este trabalho foi conduzido para estudar a distribuição de Cu, Fe, Mn e Zn nas frações proteicas de amostras de trigo submetidas a um procedimento de extração sequencial. Maiores concentrações dos elementos foram determinadas na fração extraída com tampão Tris-HCl contendo 1% de dodecil sulfato de sódio (SDS). As frações da amostra de trigo obtidas após o procedimento de extração foram analisadas por eletroforese em gel de poliacrilamida unidimensional (1D SDS-PAGE) e as bandas de proteínas foram tratadas para quantificar os metais por espectrometria de absorção atômica em forno de grafite (GF AAS). Desta forma, foi possível associar os metais Cu, Fe, Mn e Zn às bandas proteicas de peso molecular específico. As frações proteicas da amostra de trigo foram analisadas por espectrometria de massas por tempo de vôo acoplada à ionização dessortiva de matriz por laser (MALDI-TOF-MS), após procedimento de digestão proteica, identificando-se as proteínas lipid transfer e grain softness, sendo esta última possivelmente associada ao metal manganês.

This work was initially conducted to study the distribution of Cu, Fe, Mn and Zn in the protein fractions of wheat sample subjected to sequential extraction procedure. The highest metal concentrations were determined in the fraction extracted with Tris-HCl buffer containing 1% sodium dodecyl sulfate (SDS). The fractions of wheat sample obtained after the extraction procedure were analyzed by one-dimensional polyacrylamide gel electrophoresis (1D SDS-PAGE) and protein bands were treated to quantify Cu, Fe, Mn, and Zn by graphite furnace atomic absorption spectrometry (GF AAS). Metals were associated to protein bands of specific molecular weight, determined using a standard protein. The protein fractions were also analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) after a typical protein digestion protocol, identifying lipid transfer protein and grain softness, the latter being possibly associated to Mn.

Elementos terras raras (ETR) fazem parte de um grupo peculiar de elementos químicos e sua determinação em amostras geológicas é importante e complexa, devido às baixas concentrações e problemas com interferências espectrais e não espectrais. Neste trabalho, planejamentos experimentais foram utilizados para otimizar as condições operacionais de um espectrômetro de emissão óptica com plasma indutivamente acoplado (ICP OES) para a determinação de ETR. A razão entre o sinal analítico dos ETR e o sinal de fundo (SBR) e a razão Mg II/Mg I foram avaliadas como respostas na otimização. De acordo com os resultados obtidos, três diferentes condições de operação foram selecionadas e classificadas como robusta, semi-robusta e melhor SBR. Limites de detecção (LOD), SBR e desvio padrão relativo de medidas de uma solução do branco (DPRbranco) foram determinados. Na condição semi-robusta (potência de 1250 W e vazão do gás nebulizador de 0,90 L min-1) foram obtidos LOD e DPRbranco mais baixos que nas outras condições estabelecidas.

Rare earth elements (REEs) is a peculiar group of chemical elements. Their determination in geological samples is important and complex due to their low concentrations and problems with spectral and non-spectral interferences. Herein, the operating conditions of an inductively coupled plasma optical emission spectrometer were optimized for the determination of REEs using experimental designs. The signal-to-background ratio (SBR) of the REEs emission signals and the Mg II/Mg I line intensity ratio were evaluated as response functions. According to the results obtained, three different sets of operating conditions were selected and classified as robust, semi‑robust and best SBR conditions. Limits of detection (LOD), SBR and relative standard deviation of the blank solution (RSDblank) were determined. The semi-robust condition (RF power of 1250 W and nebulizer gas flow rate of 0.90 L min-1) exhibited lower LOD and RSDblank than others tested operating conditions.

A sequential extraction procedure was applied to wheat and soybean seed samples. The total protein content (determined by two distinct methods: Bradford and bicinchoninic acid-BCA) and distribution of Cu, Fe, Mn and Zn in each fraction was determined. The sequential extraction employed four different solutions: water, 0.5 mol L-1 NaCl, ethanol/water (70:30 v v-1) and 0.5 mol L-1 NaOH. For both samples, the highest concentration of metals was observed in those extracts associated with globulin-type proteins using NaCl solution. Regarding protein content, higher levels were obtained using the BCA method.

Os sedimentos possuem propriedades de acumulação de poluentes e a determinação de elementos tóxicos nessas amostras permite avaliar o seu ciclo geoquímico. Arsênio e mercúrio foram determinados em 28 amostras de sedimento da Bacia do Rio São Francisco, Minas Gerais, Brasil, por geração de hidretos acoplada à espectrometria de absorção atômica (HG AAS). Foram empregados procedimentos de digestão pseudo-total empregando HCl:HNO3 (3:1 v/v) e extração parcial com HCl 1 mol L-1. Realizou-se ainda a determinação de Hg nas amostras sólidas, utilizando-se um analisador direto de mercúrio. Observou-se que 46% das amostras apresentaram concentrações de As acima do limite de nível 1 estabelecido pela Resolução 344/2004 do CONAMA e que 14% excederam o limite de nível 1 para Hg. As amostras com altas concentrações de Hg foram também analisadas por termodessorção acoplada à espectrometria de absorção atômica (TDAAS) para especiação e os termogramas apontaram somente a presença da espécie Hg(II)

Sediments have metal accumulation properties, then, an evaluation of their geochemistry cycle is feasible via toxic element determination of these samples. Arsenic and mercury determinations were accomplished in 28 sediment samples from the São Francisco River Basin, Minas Gerais, Brazil. For sample pretreatment were employed a pseudo-total digestion procedure with HCl:HNO3 (3:1 v/v) and a partial extraction procedure with 1 mol L-1 HCl. Arsenic and mercury were analysed by hydride generator atomic absorption spectrometry (HG AAS). Mercury determination was realized in the solid samples by direct mercury analyzer (DMA). It was observed that 46% of the samples presented arsenic concentrations above Brazil's legal limits, and 14% of samples exceeded the established mercury limit. The samples with high mercury content were also analysed by thermodesorption coupled to atomic absorption spectrometry (TDAAS) and only Hg(II) was identified

Uma análise de variância de três fatores foi usada para testar a significância do tipo de recipiente, tipo de material e número de replicatas na preparação de amostras de sedimento utilizando um banho ultra-sônico. A extração convencional com HCl 1,0 mol L-1, por 0,5, 4 e 12 h, foi modificada, e o banho ultra-sônico foi aplicado para diminuir o tempo de preparo de amostras. Os metais traço foram medidos por ICP OES. Os melhores resultados foram obtidos com frascos de Teflon® com base plana. Com exceção do Ni, constatou-se que é possível trabalhar no banho de ultrasom em triplicatas, sem comprometer a eficiência e/ou precisão da extração. A eficiência de extração melhorou com o aumento no tempo de sonicação de 1 para 50 min. Para a maioria dos elementos, a extração assistida por radiação ultra-sônica pode reduzir o tempo convencional de extração de 12 h para 50 min ou menos (i.e. 6 min para Pb). A precisão obtida foi comparável aos valores obtidos com a extração convencional. O método proposto é rápido, barato e uma boa alternativa para o levantamento da biodisponibilidade e potencial de mobilidade de metais em sedimentos.

A three factors analysis of variance was used to test the significance of the type of vessel, the type of material and the number of replicates in the preparation of sediment samples using an ultrasonic bath. The conventional extraction with HCl 1.0 mol L-1, for 0.5, 4 and 12 h, has been modified, applying an ultrasonic bath, in order to speeding up the sample preparation time. Trace metals were measured by an ICP OES. The best results were obtained using a Teflon® vessel with a flat bottom. For all metals but Ni it was demonstrated the feasibility of working in triplicates in the ultrasonic bath, without compromising the efficiency and/or the precision of the extraction. Leaching efficiency enhanced with increasing sonication time from 1 to 50 min. For most elements the ultrasound-assisted leaching could reduce the conventional extraction time from 12 h to 50 min or even less (i.e. 6 min for Pb). The precision obtained was comparable to values obtained for the conventional acid extraction. The proposed method is a fast, inexpensive and easy alternative for screening of the potential mobility and bioavailability of metals in sediments.

A espectrometria de absorção atômica com forno tubular na chama (TS-FF-AAS) foi empregada para a determinação de Cd e Pb em diferentes tipos de amostras brasileiras de tabacos após a pré-concentração no ponto nuvem (CP) otimizada por planejamento Doehlert. Para a separação das fases no procedimento por ponto nuvem, Triton® X-114 e 2-(bromo-2-piridilazo)-5-dietilaminofenol (Br-PADAP) foram utilizados como surfactante não iônico e agente complexante, respectivamente. Cádmio e chumbo foram determinados após digestão ácida e pré-concentração por ponto nuvem, sendo que as variáveis otimizadas por planejamento Doehlert foram: volume do agente complexante, volume de Triton® X-114 e pH. Um ponto de máximo foi obtido nas superfícies de resposta para Cd e Pb. Para as determinações dos elementos por TS-FF-AAS, um volume de amostra de 50 µL foi introduzido no tubo de Ni posicionado sobre a chama, usando ar como carregador na vazão de 0,4 mL min-1. Os limites de detecção e os desvios padrão relativos após a combinação de CP e TS-FF-AAS foram de 4,0 e 13 µg kg-1 e 3,1 e 0,7% para Cd e Pb, respectivamente. A exatidão do método proposto foi avaliada realizando-se testes de adição-recuperação e empregando-se material de referência certificado (folhas de chá e folhas de pessegueiro). As recuperações variaram de 93 a 103 e 93 a 107% para Cd e Pb, respectivamente. Todos os resultados obtidos para as amostras dos materiais de referência estão em concordância com os valores certificados a um nível de confiança de 95 ou 99% aplicando-se o teste t-Student.

A thermospray flame furnace atomic absorption spectrometer (TS-FF-AAS) was employed to determine Cd and Pb in different Brazilian tobacco samples. Sample pretreatment consisted of acid decomposition and cloud point (CP) preconcentration optimized by Doehlert design. To promote phase separation in the cloud point procedure, polyoxyethylene(8) isooctylphenyl ether (Triton® X-114) and 2-(bromo-2-pyridylazo)-5-diethyl-amino-phenol (Br-PADAP) were used as a nonionic surfactant and a complexing agent, respectively. The variables of the cloud point preconcentration procedure optimized by Doehlert design were: complexing agent volume, Triton X-114 volume, and pH. A response surface maximum point was obtained for Cd and Pb. For TS-FF-AAS, a sample volume of 50 µL was introduced into the hot Ni tube using air carrier at a flow rate of 0.4 mL min-1. The limits of detection and relative standard deviations obtained for Cd and Pb when CP and TS-FF-AAS were associated were 4.0 and 13 µg kg-1, and 3.1 and 0.7%, respectively. Accuracy was checked by addition-recovery experiments, as well as by using two certified reference materials (tea and peach leaves). Cadmium and lead recoveries ranged from 93 to 103 and 93 to 107%, respectively. All results obtained for reference materials were in agreement with certified values at 95 or 99% confidence levels by t-Student test.

The applicability of the recently proposed procedure based on gradual sample addition to microwave-assisted pre-heated concentrated acid is limited by the sample viscosity. In this work, lubricating oil samples with high viscosity were encapsulated and manually added to the microwave-assisted pre-heated concentrated digestion mixture. The procedure was applied for determination of Al, Ca, Cr, Cu, Fe, Mg, Ni, P, Pb, Si, Sn, Sr, V, W, and Zn in lubricating oil by inductively coupled plasma optical emission spectrometry (ICP OES). Determined and certified values for Ca, Mg, P, and Zn in lubricating oil were in agreement at a 95% confidence level.

The use of factorial design was evaluated for optimization of focused-microwave-assisted digestion of bean samples. Calcium, Fe, Mg, Mn and Zn percentual recoveries were determined in digestates after focused-microwave-assisted digestion according to factorial design procedures. A cavity microwave digestion was carried out to certify the elemental compositions obtained. The accuracy was checked using a standard reference material, the NIST SRM 8433 - Corn Bran. Results are in agreement with certified values at the 95% confidence limit when the Student t-test was used. Volumes of nitric and sulfuric acid, temperature, and the interplay between HNO3 and H2SO4 initial volumes were significant variables according to P-values in the analysis of variance (ANOVA).

A eficiência dos procedimentos de digestão em fornos de microondas pode ser afetada por parâmetros experimentais críticos, como massa de amostra, volume da mistura ácida, potência de radiação aplicada e o tempo da digestão. Neste trabalho foi proposta a utilização de um planejamento fatorial completo para a otimização da digestão de amostras de óleo lubrificante em forno de microondas, com recipientes fechados. O teor de carbono residual e a acidez final das soluções foram determinados em todos os digeridos provenientes do forno de microondas, como resposta ao planejamento fatorial. Cálcio, Cu, Mg, P, S e Zn foram determinados nos digeridos ácidos e a exatidão foi checada utilizando-se um material de referência certificado, NIST SRM 1848-Lubricating Oil Additive Package. Os resultados encontrados para as amostras e para o material de referência certificado estão em concordância a um nível de confiança de 95%. Tempo de digestão, potência de radiação aplicada, massa de amostra e as interações entre essas variáveis foram significativas (P < 5%), aplicando-se a análise de variância (ANOVA).

This work proposes the use of factorial design for optimization of microwave-assisted digestion of lubricating oil. The accuracy of digestion procedures is affected by critical experimental parameters, such as sample amount, concentrated acid volumes, microwave radiation applied power, and digestion time. The effects of these key variables on the microwave-assisted digestion efficiency were investigated. The residual carbon content and the acidity were determined in all digestates after microwave-assisted digestion as response of the factorial design. Calcium, Cu, Mg, P, S, and Zn were determined in oil digestates obtained by using two systems: a cavity- and a focused-oven. The accuracy was checked using one standard reference material, NIST SRM 1848 - Lubricating Oil Additive Package. All determined and certified values are in agreement at a 95% confidence level. The digestion time, microwave applied power, sample mass, and the interaction between these variables were significant according to P-values when the analysis of variance (ANOVA) was used.