RESUMO O sedimento é um dos compartimentos mais importantes dos ecossistemas aquáticos, possui papel importante no transporte e acumulação de metais. Este estudo teve por objetivo determinar a concentração de metais nas frações geoquímicas de sedimentos do Rio Bento Gomes, Pantanal de Poconé (MT) por meio da extração seletiva e sequencial, a fim de avaliar a distribuição e mobilidade dos metais. Os sedimentos foram coletados nos períodos seco e chuvoso em oito pontos distintos, e os metais (Fe, Mn, Cr, Cu, Zn e Ni) extraídos dos sedimentos por procedimentos de extração sequencial (baseada no protocolo proposto por BCR -Community Bureau of Reference) e de extração seletiva (baseada no protocolo 3050B da Environmental Protection Agency of the United States), utilizando-se materiais de referência certificados para validação do método analítico. Todos os metais apresentaram teores abaixo do limite previsto na Resolução CONAMA nº 454/2012 no período seco, com exceção do Ni no período chuvoso (maior que 18 mg kg-1). Os estudos de fracionamento indicaram que os metais foram encontrados nas frações mobilizáveis do sedimento, especialmente associados aos óxidos de ferro. Os metais mais móveis e, consequentemente, mais biodisponíveis, foram o manganês, zinco e níquel, principalmente na época chuvosa. Maiores teores de cobre foram encontrados nas frações residuais do sedimento, indicando baixa mobilidade no meio aquático. A sequência de mobilidade dos metais estudados foi Mn > Zn > Ni > Cr > Cu > Fe.

ABSTRACT The sediment is one of the major compartments of aquatic ecosystems, it plays an important role in the transport and accumulation of metal. This study aimed to determine the concentration of metals in geochemical fractions of the Bento Gomes River sediments, Pantanal of Poconé (MT) through selective extraction and sequential in order to assess the distribution and mobility of metals. The sediments were collected in the rainy and dry seasons in eight different points, and the metals (Fe, Mn, Cr, Cu, Zn and Ni) extracted from sediments by sequential extraction procedures (based on the proposed by BCR protocol - Community Bureau of Reference) and selective extraction (based on the 3050B protocol of the Environmental Protection Agency of the United States), using certified reference materials for validation of the analytical method. All metals showed levels below the limits established by CONAMA Resolution nº 454/2012 in the dry season, except for Ni in the rainy season (greater than 18 mg kg-1). The fractionation studies indicated that the metals were found in mobilized sediment fractions, especially associated with the iron oxides. The metals more mobile and hence more bioavailable, have been manganese, zinc and nickel, particularly in the rainy season. Largest copper contents were found in the residual fraction of the sediment, indicating low mobility in the aquatic environment. The sequence of mobility of the metals studied was Mn> Zn> Ni> Cr> Cu> Fe.

A simple, inexpensive, and clean methodology employing a combined spot test/diffuse reflectance spectroscopy procedure was developed and applied for the quality control analysis of lead in hair dyes, using a filter paper platform. The method is based on the complexation reaction of lead, present in a pH 2.8 buffer medium containing tartaric acid and sodium and potassium tartrate, with sodium rhodizonate (ROD) in an aqueous medium containing sodium dodecyl sulfate (SDS) surfactant, yielding a colored compound on the surface of a filter paper. The concentrations of ROD and SDS were optimized using experimental design. The linear range obtained for reflectometric measurements carried out at 545 nm was 4.70-140 mg L-1 of lead (R = 0.998), and the limits of detection and quantification were 1.12 and 3.75 mg L-1, respectively. The proposed method was successfully applied to the analysis of lead in progressive hair dyes.

Este artigo descreve o desenvolvimento e a aplicação de um dispositivo portátil, simples e barato para a determinação colorimétrica quantitativa de fármacos em formulações farmacêuticas. O sensor é um resistor detector de luz (RDL) colocado numa célula de PTFE e acoplado a um multímetro de baixo custo. Os estudos quantitativos foram realizados utilizando captopril/p-cloranil/H2O2 e metildopa/molibdato de amônio como sistemas reacionais. As curvas de calibração foram obtidas através da representação gráfica da resistência elétrica do RDL contra a concentração dos complexos coloridos formados nas faixas de 1,84 × 10-4 e 1,29 × 10-3 mol L-1 e 5,04 × 10-4 e 2,52 × 10- 3 mol L-1 para captopril/p-cloranil/H2O2 e de metildopa/molibdato de amônio, respectivamente, com bons coeficientes de determinação. As análises estatísticas dos resultados obtidos mostraram que não houve diferença significativa entre os métodos propostos e os métodos oficiais como evidente a partir dos testes "t-Student" eF-Fisher, com nível de confiança de 95%. Os resultados deste estudo demonstram que o instrumento proposto neste trabalho é simples, de fácil operação, baixo custo e apresentou boa exatidão e boa precisão para o doseamento de fármacos em medicamentos.

This article describes the application and performance of an inexpensive, simple and portable device for colorimetric quantitative determination of drugs in pharmaceutical preparations. The sensor is a light detector resistor (LDR) incorporated into a black PTFE cell and coupled to a low-cost multimeter (Ohmmeter). Quantitative studies were performed with captopril/p-chloranil/H2O2 and methyldopa/ammonium molybdate systems. Calibration curves were obtained by plotting the electrical resistance of the LDR against the concentration of the colored species in the ranges 1.84 × 10-4 to 1.29 × 10-3mol L-1 and 5.04 × 10-4 to 2.52 × 10-3 mol L-1 for captopril/p-chloranil/H2O2 and methyldopa/ammonium molybdate systems, respectively, exhibiting good coefficients of determination. Statistical analysis of the results obtained showed no significant difference between the proposed methodologies and the official reported methods, as evidenced by the t-test and variance ratio at a 95% confidence level. The results of this study demonstrate the applicability of the instrument for simple, accurate, precise, fast,in situ and low-cost colorimetric analysis of drugs in pharmaceutical products.

A flow injection spectrophotometric procedure for the determination of glyphosate in commercial formulations of herbicides is proposed. The determination is based on the reaction of glyphosate and p-dimethylaminocinnamaldehyde, in acid medium, yielding a colored compound (l máx = 495 nm). Under optimal conditions, Beer's law is obeyed in a concentration range 40-640 mg mL-1 with a correlation coefficient of 0.9996. The detection limit was 8.60 mg mL-1 for glyphosate. The method was successfully applied for the determination of glyphosate in commercial formulations of herbicides. Recovery of glyphosate from various commercial samples of herbicides range from 91.0 to 110%.

This work proposes a sequential injection analysis (SIA) system for the spectrophotometric determination of norfloxacin (NOR) and ciprofloxacin (CIP) in pharmaceutical formulations. The methodology was based on the reaction of these drugs with p-(dimethylamino)cinnamaldehyde in micellar medium, producing orange colored products (λmax = 495 nm). Beer´s law was obeyed in the concentration range from 2.75x10-5 to 3.44x10-4 mol L-1 and 3.26x10-5 to 3.54x10-4 mol L-1 for NOR and CIP, respectively and sampling rate was 25 h-1. Commercial samples were analyzed and results obtained through the proposed method were in good agreement with those obtained using the reference procedure for a 95% confidence level.

Um método espectrofotométrico simples, rápido, exato e barato foi desenvolvido para a determinação de tetraciclina e doxiciclina. O método é baseado na reação entre estas drogas e cloramina-T em meio alcalino produzindo produtos de cor vermelha com absorbância máxima em 535 e 525 nm para a tetraciclina e doxiciclina, respectivamente. As melhores condições para as reações foram encontradas utilizando métodos multivariados. A lei de Beer é obedecida no intervalo de concentração de 1,03 x 10-5 a 3,61 x 10-4 mol L-1 e 1,75 x 10-5 a 3,48 x 10-4 mol L-1 para a tetraciclina e doxiciclina, respectivamente. Os limites de quantificação foram 5,63 x 10-6 mol L-1 e 7,12 x 10-7 mol L-1 para a tetraciclina e doxiciclina, respectivamente. O método proposto foi aplicado com êxito na determinação destas drogas em formulações farmacêuticas e os resultados obtidos estão de acordo com os obtido pelo método comparativo em 95% de confiança.

A simple, rapid, accurate and inexpensive spectrophotometric method for the determination of tetracycline and doxycycline has been developed. The method is based on the reaction between these drugs and chloramine-T in alkaline medium producing red color products with absorbance maximum at the Λ = 535 and 525 nm for the tetracycline and doxycycline, respectively. The best conditions for the reactions have been found using multivariate method. Beer´s law is obeyed in a concentration ranges 1.03 x 10-5 to 3.61 x 10-4 mol L-1 and 1.75 x 10-5 to 3.48 x 10-4 mol L-1 for the tetracycline and doxycycline, respectively. The quantification limits were 5.63 x 10-6 mol L-1 and 7.12 x 10-7 mol L-1 for the tetracycline and doxycycline, respectively. The proposed method was successfully applied to the determination of these drugs in pharmaceutical formulations and the results obtained were in good agreement with those obtained by the comparative method at the 95% confidence level.

A simple and more environmentally friendly method by combined spot test-diffuse reflectance spectroscopy for determining metoclopramide in pharmaceutical formulations is described. The method is based on the reaction between metoclopramide and p-dimethylaminocinnamaldehyde, in the presence of HCl, producing a colored compound (λmáx = 580 nm) on the filter paper. The linear range was from 5.65 x 10-4-6.21x10-3 mol L-1 (r = 0.999). The limit of detection was 1.27 x 10-4 mol L-1. The proposed reflectometric method was applied successfully to the determination of metoclopramide in pharmaceuticals and it was favorably compared with the Brazilian or British Pharmacopoeia methods at 95% confidence level.

O coeficiente de atividade molar individual do íon fluoreto (yF) foi determinado a 25° C para valores de força iônica entre 0,100 and 3,00 mol L-1 (NaClO4) usando-se um eletrodo íon-seletivo. A dependência do coeficiente de atividade com a força iônica é explicada pela equação ΦF = log yF = 0,2315I - 0,041I². A função ΦF(I), foi associada a outras funções estimadas em trabalhos anteriores, por exemplo,ΦCu(I) para cobre, e ΦH(I) para íon hidrogênio, possibilitando a estimativa de constantes de estabilidade estequiométricas e termodinâmicas tanto para equilíbrios de protonação de alguns haletos e pseudo-haletos como para as constantes de formação de complexos 1:1 de metais bivalentes com fluoreto e pseudo-haletos. O procedimento de cálculo proposto é consistente com dados experimentais criticamente selecionados da literatura. Verificou-se que é possível usar ΦF(I) na previsão de parâmetros de equilíbrio termodinâmicos independentemente do caráter HSAB de Pearson .

The molar single ion activity coefficient (yF) of fluoride ions was determined at 25 °C and ionic strengths between 0.100 and 3.00 mol L-1 NaClO4 using an ion-selective electrode. The activity coefficient dependency on ionic strength was determined to be ΦF = log yF = 0.2315I - 0.041I². The function ΦF(I), combined with functions obtained in previous work for copper (ΦCu) and hydrogen (ΦH), allowed us to make the estimation of the stoichiometric and thermodynamic protonation constants of some halides and pseudo-halides as well as the formation constants of some pseudo-halides and fluoride 1:1 bivalent cation complexes. The calculation procedure proposed in this paper is consistent with critically-selected experimental data. It was demonstrated that it is possible to use ΦF(I) for predicting the thermodynamic equilibrium parameters independently of Pearson's hardness of acids and bases.

This paper reports an analytical method for the determination of ambroxol in micellar medium by spot test-diffuse reflectance spectroscopy. The reflectance measurements were performed analyzing the colored compound (λ= 520 nm) produced from the reaction between ambroxol and p-dimethylaminocinnamaldehyde on the surface filter paper. The linear range was from 1.21 × 10"3 to 9.65 × 10"3 mol L-1 (500 - 4000 μg mL-1). The limit of detection and quantification were 3.50 x 10-4 mol L-1 (145 μg mL-1) and 1.16 x 10-3 mol L-1 (481 μg mL-1), respectively. Five commercial samples were analysed and the results obtained by the proposed method were in good agreement with those obtained by the literature method at 95% confidence level.

This paper proposes a methodology for spectrophotometric determination of hexamethylenetetramine (HMT) by using chromotropic acid in a phosphoric acid media employing a domestic microwave oven as a source of heating. The reddish-purple soluble product is quantitatively formed after 30 s of irradiation and obeys the Beer´s law in the range between 0.1-1.2 mg L-1 HMT (r = 0.99925). The method was applied successfully in commercial pharmaceutical preparations containing dyes in their composition. The results showed that the method proposed is feasible for simplicity, speed, low cost, precision and accuracy when compared with United States Pharmacopeia official method.

A flow-injection (FI) spectrophotometric procedure is proposed for tetracycline (TC) and doxycycline (DXC) determination in pharmaceuticals. The method is based on the reaction of oxidation of these drugs by chloramine-T in alkaline medium producing red color products (λmax = 535 and 525 nm). Beer´s law is obeyed in the concentration range from 6.62 x 10-5 to 7.72 x 10-4 mol L-1 and 5.37 x 10-5 to 7.16 x 10-4 mol L-1 for TC and DXC, respectively. The analytical frequency was 50 h"1 and 45 h-1 for TC and DXC, respectively. The results obtained by the proposed method were in good agreement with those obtained by the official method at 95% confidence level.

A construção, avaliação e aplicação analítica de um sensor potenciométrico do tipo Pt|Hg|Hg2(Fur)2|Grafite, onde Fur significa íon 4-cloro-N-furfuril-5-sulfamoil-antranilato, são descritas. O eletrodo responde a Fur com sensibilidade de (-58,4 ± 0,9) mV década-1 no intervalo de 5,0 × 10-7-1,0 × 10-2 mol L-1, a pH 7,0-9,0 e com um limite de detecção de 3,8 × 10-7 mol L-1. O eletrodo é facilmente construído e de baixo custo, apresenta um rápido tempo de resposta (10-20 s) e pode ser usado por um período de 6 meses sem qualquer variação considerável nas suas características de desempenho. O eletrodo proposto mostrou boa seletividade na presença de várias substâncias, bem como na presença de alguns carboxilatos e ânions inorgânicos. O eletrodo foi aplicado com sucesso na determinação de furosemida em medicamentos, urina, soro sanguíneo e amostras comerciais de leite bovino.

The construction, evaluation and analytical application of a potentiometric sensor, namely, Pt|Hg|Hg2(Fur)2|Graphite, where Fur stands for 4-chloro-N-furfuryl-5-sulphamoyl-anthranilate ion, are described. This electrode has a linear dynamic range between 5.0 × 10-7-1.0 × 10-2 mol L-1 with a near-Nernstian slope of (-58.4± 0.9) mV decade-1 and a detection limit of 3.8 × 10-7 mol L-1. The potentiometric response is independent of the pH of the solution in the pH range 7.0-9.0. The electrode shows easy construction, low-cost, fast response time (within 10-20 s) and can be used for a period of 6 months without significant change in its performance characteristics. The proposed sensor displayed good selectivities over a variety of other anions (carboxylates and inorganic anions). Application of this potentiometric sensor for the furosemide determination in pharmaceuticals, urine, blood serum and commercial milk samples is reported.

This paper describes a simple and rapid spectrophotometric method for quantitative determination of sildenafil citrate based on its reaction with p-chloranil accelerated by hydrogen peroxide, producing a stable purple compound (λmax= 535 nm). In the absence of peroxide this reaction is very slow. The experimental conditions were optimized by using response surface methodologies. Beer's law is obeyed in a concentration range of 8.52 x 10-5 - 1.70 x 10-3 mol L-1 (r = 0.999). The detection limit was 1.96 x 10-5 mol L-1. The method was successfully applied for the determination of sildenafil citrate in medicines with good accuracy and precision.

No presente trabalho foi investigado o desenvolvimento de um método espectrofotométrico limpo para a determinação de formaldeído em amostras comerciais. A substituição de reagentes altamente perigosos foi explorada, de modo a atender aos princípios estabelecidos pela química verde. O método proposto baseou-se na reação entre formaldeído e ácido cromotrópico na presença de sulfato de magnésio, produzindo um complexo estável Mg2+/ciclotetracromotropileno (λmax = 535 nm). Não há relatos na literatura sobre a utilização da reação supramencionada na determinação de formaldeído. As condições experimentais foram otimizadas, aplicando-se a metodologia de superfície de resposta. A lei de Lambert-Beer é obedecida na faixa de concentração de 3 a 11 mg L-1 de formaldeído, com coeficiente de correlação de 0,999. O método proposto para a determinação de formaldeído foi aplicado em amostras comerciais de desinfetantes e defrizantes capilares. Os resultados compararam-se favoravelmente aos obtidos pelo método oficial, demonstrando exatidão e precisão satisfatórias.

A green spectrophotometric analytical method for determination of formaldehyde in commercial samples was designed and investigated. Replacement of hazardous reagents was explored to attain the clean chemistry standards. The method is based on formaldehyde reaction with chromotropic acid in the presence of magnesium sulphate producing a stable complex Mg2+/ cyclotetrachromotropylene (λmax = 535 nm). To the best of our knowledge, there are no reports on the use of the above mentioned reaction for this determination. The experimental conditions were optimized by the response surface methodologies. Beer's Law is obeyed in a concentration range of 3 to 11 mg L-1 of formaldehyde with a correlation coefficient of 0.999. The proposed method was applied for the determination of formaldehyde in commercial disinfectants and deffrizing hair products. The results were favorably compared with those of the official method, with good accuracy and precision.

Este artigo descreve um método simples, portátil e ambientalmente amigável para a rápida determinação de dipirona em medicamentos empregando a espectroscopia de reflectância difusa. O método proposto está baseado nas medidas de reflectância do composto alaranjado produzido na reação de spot-test entre dipirona e p-dimetilaminocinamaldeído (p-DAC), em meio ácido, usando papel de filtro como suporte sólido. Metodologias de planejamento de experimentos foram utilizadas para a otimização das condições experimentais. Todas as medidas de reflectância foram efetuadas em 510 nm e o intervalo linear foi de 1,42 <FONT FACE=Symbol>´</FONT> 10-4-2,85 <FONT FACE=Symbol>´</FONT> 10-3 mol L-1, com coeficiente de correlação de 0,999. Os limites de detecção (LOD) e de quantificação (LOQ) foram de 1,20 <FONT FACE=Symbol>´</FONT> 10-5 mol L-1 e 4,00 <FONT FACE=Symbol>´</FONT> 10-5 mol L-1, respectivamente. A precisão intradia e interdia foi avaliada na análise de uma solução de dipirona 7,90 <FONT FACE=Symbol>´</FONT> 10-4 mol L-1 (n = 10). Os coeficientes de variação foram 1,1 e 0,9%, respectivamente. O método proposto foi aplicado com êxito na determinação de dipirona em amostras comerciais de medicamentos. Não foram observadas interferências dos excipientes comuns em formulações farmacêuticas. Os resultados obtidos pelo método proposto estão em boa concordância com aqueles obtidos pelo procedimento da Farmacopéia Brasileira num nível de confiança de 95%.

This paper describes a simple, portable and environmentally friendly method for the rapid determination of dipyrone in pharmaceuticals by using diffuse reflectance spectroscopy. The proposed method is based on the reflectance measurements of the orange compound produced from the spot test reaction between dipyrone and p-dimethylaminocinnamaldehyde (p-DAC), in acid medium, using a filter paper as solid support. Experimental design methodologies were used to optimize the measurement conditions. All reflectance measurements were carried out at 510 nm and the linear range was from 1.42 <FONT FACE=Symbol>´</FONT> 10-4-2.85 <FONT FACE=Symbol>´</FONT> 10-3 mol L-1, with a correlation coefficient of 0.999. The limit of detection (LOD) and the limit of quantification (LOQ) were 1.20 <FONT FACE=Symbol>´</FONT> 10-5 mol L-1 and 4.00 <FONT FACE=Symbol>´</FONT> 10-5 mol L-1, respectively. The intraday precision and interday precision were studied for 10 replicate analyses of 7.90 <FONT FACE=Symbol>´</FONT> 10-4 mol L-1 dipyrone solution. The coefficients of variation were 1.1 and 0.9%, respectively. The proposed method was applied successfully to the determination of dipyrone in commercial brands of pharmaceuticals. No interferences were observed from the common excipients in formulations. The results obtained by the proposed method were favorably compared with those given by the Brazilian Pharmacopoeia procedure at 95% confidence level.