Spectrophotometric determination of paracetamol in pharmaceuticals using microwave-assisted hydrolysis and a micellar medium

A new spectrophotometric method employing a micellar medium is proposed for the determination of paracetamol in pharmaceuticals. The method is based on the acid hydrolysis of paracetamol to p-aminophenol (PAP), which under acidic conditions reacts with p-dimethylaminocinnamaldehyde (pDAC), producing a red compound (λmax = 530 nm). This reaction can be enhanced five-fold in the presence of sodium dodecyl sulfate (SDS). The effects of all the parameters involved in both the hydrolysis step and the derivatization reaction were investigated using experimental design methodologies. The method presented a linear range of 0.2 to 3.9 μg mL–1 and an excellent correlation coefficient (r = 0.9996). The limit of detection was estimated to be 30.0 μg/L. The technique was successfully applied for the determination of paracetamol in commercial brands of pharmaceuticals. No interferences from the excipients commonly used in commercial formulations were observed, and the results obtained compared favorably with measurements made using the United States Pharmacopeia procedure, at a 95 % confidence level.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Alternativas para o uso do glicerol produzido a partir do biodiesel

Nos últimos anos tem havido esforços consideráveis no desenvolvimento de novas tecnologias para a produção de produtos químicos a partir de recursos renováveis de biomassa, principalmente combustíveis, em resposta ao esgotamento da matéria-prima de origem fóssil e as preocupações com o meio ambiente. Entre os vários compostos derivados a partir da biomassa que têm sido propostos como matéria-prima para a produção de substâncias químicas, o glicerol é de interesse especial porque é produzido em grandes quantidades, como um coproduto durante a produção de biodiesel por meio de transesterificação. Com o rápido aumento da produção de biodiesel em todo o mundo, o mesmo acontece com a produção do glicerol. O recente aumento da produção de glicerol a partir do processo de fabricação de biodiesel criou um excesso no mercado, como resultado, são necessárias novas tecnologias para o uso do glicerol que é uma substância abundante e tem grande potencial para ser uma importante matéria prima para produção de produtos de alto valor agregado

Simple and lowecost transition metal-free borophosphate glass catalyst for aromatic alcohol oxidation by sodium hypochlorite

The oxidation of primary and secondary alcohols to their respective aldehydes/ketones is one of the most important reactions in fine chemistry due to the industrial application of these products. Based on this, a large number of new catalysts and oxidants have been tested using this reaction as a catalytic model, mainly looking for a process that ensures high aldehyde selectivity. In this paper, we have used moisture stable borophosphate glass doped with 10 mol% Al2O3 as a heterogeneous catalyst in the oxidation of sodium hypochlorite, an effective, greener, and low-cost oxidant, using acetonitrile as solvent under mild conditions. The glass catalyst mass and the particle size were evaluated, as were the reaction temperature and oxidant amount, to determine the ideal reaction conditions where the conversions achieved 87.0 mol% for 1-phenylethanol to acetophenone and 79.4 mol% for benzyl alcohol to benzaldehyde, with benzaldehyde selectivity above 95%. Although sodium hypochlorite is a strong oxidant, benzaldehyde was the main product of the oxidation of benzyl alcohol due to the formation of a biphasic organic-aqueous system that protects the aldehyde from oxidation and allows the reaction to occur without the use of a phase transfer catalyst (PTC). HPLC analysis of both phases showed that alcohols, aldehyde, and ketone were mostly present in the organic phase (concentrations above 98.7%). During the reaction, a small amount of alcohol is transferred to the aqueous phase, where the oxidation took place. Once formed, the products are transferred back to the organic phase. ICP-OES analysis indicates that borophosphate glass acts in the reaction by partially releasing phosphate-based groups, reducing the pH of hypochlorite to 9. In this sense, borophosphate glasses prove to be a simple and inexpensive alternative for the development of new catalysts

Desenvolvimento de novos procedimentos analíticos para a determinação de paracetamol em amostras de medicamentos

Este trabalho propõe o desenvolvimento de novos procedimentos analíticos voltados para a determinação de paracetamol em formulações farmacêuticas. Num primeiro momento, o procedimento foi baseado na hidrólise ácida do paracetamol (PCT) à p-aminofenol (PAP), seguido pela instantânea reação deste com p-dimetilaminocinamaldeído (p-DAC), em meio micelar, para formar um produto vermelho, o qual pôde ser monitorado por espectrofotometria (λmáx = 530 nm), 10 minutos após o início da reação. A hidrólise realizada em forno de microondas foi uma estratégia adotada como alternativa ao moroso processo de hidrólise convencional realizado em banho de água fervente. Estudos preliminares realizados em nosso laboratório, demonstraram ser efetiva a utilização de meio micelar – com dodecil sulfato de sódio (SDS), a fim de tornar o método mais sensível. Em seguida, os efeitos de todos os parâmetros envolvidos no processo analítico foram investigados em detalhes por meio de metodologias de planejamento de experimentos, para determinação das melhores condições experimentais para realização das análises. Sob as condições tidas como ideais, o método apresentou faixa linear de trabalho entre 1,3 x 10-6 – 2,6 x 10-5 mol L-1 (0,2 – 3,9 μg mL-1), com excelente coeficiente de correlação linear (r = 0,9996). O limite de detecção foi de 1,7 x 10-7 (30 ng mL-1). Num segundo momento, parte do procedimento analítico foi incorporada a um sistema automatizado de análise por injeção em fluxo com detecção espectrofotométrica. O novo procedimento analítico adotado apresentou uma ampla faixa linear de trabalho, entre 5,37 x 10-6 – 1,29 x 10-4 mol L-1 (0,8 – 19,5 μg mL-1), com coeficiente de correlação linear de 0,9998. O emprego deste sistema automatizado de análise proporcionou simplicidade e uma maior rapidez na realização das análises. Ambos os procedimentos...This work proposes the development of new analytical procedures for the determination of paracetamol in pharmaceuticals preparations. At first moment, procedure was based in the paracetamol (PCT) acid hydrolysis to p-aminofenol (PAP), followed by the instantaneous reaction of this with p-dimethylaminocinnamaldehyde (p-DAC), in micellar media in order to form a red product, which could be monitored by spectrophotometry (λmáx = 530 nm), 10 minutes after the beginning of the reaction. The hydrolysis carried out in microwave oven was a strategy adopted like alternative to the slow conventional hydrolysis carried out in boiling water bath. Preliminary studies carried out in the laboratory, showed to be efficient the utilization of micellar media – with dodecil sulphate of sodium (SDS) in order to obtain the most sensible method. Furthermore, the effects of all parameters involved in the analytic process were investigated in details by means of experiments planning methodologies for determination of the best experimental conditions to carry out the analysis. Under the ideals conditions, the method presented linear work range between 1.3 x 10-6 – 2.6 x 10-5 mol L-1 (0.2 – 3.9 mL-1), with excellent correlation coefficient (r = 0,9996). The limit of detection was 1.7 x 10-7 (30 ng mL-1) In a second moment, part of the analytical procedure was incorporated to an automated flow injection analysis with spectrophotometric detection. The adopted new analytical procedure presented a wide linear work range, between 5.37 x 10-6 – 1.29 x 10-4 mol L-1 (0.8 – 19.5 mL-1), with correlation coefficient of 0.9998. The employment of this automated system of analysis provided simplicity and a bigger quickness in the accomplishment of the analysis. Both the developed procedures were applied in the determination of paracetamol in medicines and were subsequently compared with the official method for the determination of PCT in pharmaceuticals formulations.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Caracterização físico-quimica da glicerina proveniente de usinas de biodiesel e determinação de metanol residual por CG com amostragem por headspace estático

A glicerina bruta emergente da cadeia de produção de biodiesel contém alguns produtos intermediários da reação, resíduos de catalisador, água, metanol e vem se tornando o novo desafio do Programa Nacional de Produção e Uso do Biodiesel – PNPB. Neste trabalho foi realizada a caracterização completa de amostras de glicerina bruta, glicerina loira e glicerina bidestilada. Os parâmetros analisados foram aspecto, pH, teor de água, teor de metanol, teor de matéria orgânica não glicerol (MONG), teor de glicerol, além da realização de ensaio qualitativo para presença de elementos metálicos e não metálicos. De acordo com os resultados obtidos, as características físico químicas variaram muito de uma amostra para outra. Esta diferença foi principalmente observada em decorrência de processos de transesterificação problemáticos ou mesmo devido aos tratamentos de purificação a que são submetidas as amostras de glicerina. Enquanto uma amostra de glicerina loira contém em torno de 80% de glicerol, em uma amostra de glicerina bruta este valor pode ficar abaixo de 50%. Os resultados mostraram também ser possível a obtenção de glicerol com alto grau de pureza, acima de 97%, a partir de amostras de glicerina bruta. O grau de purificação vai depender da aplicação a que estas se destinam, entretanto, a utilização de processos de tratamento incompletos ou inadequados compromete a qualidade do produto. Deste modo, a determinação de todos os parâmetros citados neste trabalho é de suma importância para fornecer dados que possam ser úteis no estabelecimento de padrões de qualidade para a glicerina. No que diz respeito ao teor de metanol, como não foi encontrado um método oficial na literatura, foi validado um novo procedimento analítico para determinação deste parâmetro, utilizando a técnica de CG-HS. As condições cromatográficas utilizadas foram injetor...The crude glycerin emerging from the biodiesel production process contains some intermediate products from reaction, residue of catalyst, moisture, methanol and for this reason is becoming the new challenge of the National Program of Production and Use of Biodiesel – PNPB. In this thesis it was performed a complete characterization of crude glycerin samples, blond glycerin samples and bi-distilled glycerin samples. All parameters analyzed were aspect, pH, water content, methanol content, material organic non-glycerol, glycerol content, as well as the qualitative determination of some metallic and non-metallic elements that may be present. According to the results obtained there was a great variation among the physic-chemical characteristics from the samples. This difference was mostly due to problematic transesterification process or due to some purification treatment which glycerin samples were submitted. While the glycerol content is around to 80% for a blond glycerin sample, this value may be bellow to 50% for crude glycerin samples. The results also showed it is possible to obtain glycerol of high purity grade, above to 97%, from crude glycerin samples. The desired purity grade depends on the future destination of the glycerin, however, the application of incomplete or inadequate treatment may compromise the quality of the product. Therefore, the determination of all physic-chemical parameters listed in this document becomes an important step to provide enough information to establish a quality standard for glycerin. Regarding the methanol content, since it was not found in literature an official method, it was developed and validated a new test procedure for this determination using GC-HS. The chromatographic conditions were PTV and FID temperatures at 300 °C. The oven temperature program was an initial hold at 50 °C for 3 min, followed... (Complete abstract click electronic access below

Potentiometric sensor for furosemide determination in pharmaceuticals, urine, blood serum and bovine milk

The construction, evaluation and analytical application of a potentiometric sensor, namely, Pt vertical bar Hg vertical bar Hg(2)(Fur)(2)vertical bar 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 x 10(-7)-1.0 x 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 x 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

Potentiometric sensor for sorbic acid determination in food products

The construction, evaluation and application of a new potentiometric sensor, namely, Pt vertical bar Hg vertical bar Hg(2)(SOB)(2) vertical bar Graphite, where SOB stands for sorbate ion, are described. This electrode has a wide linear dynamic range between 5.0 x 10(-7) and 1.0 x 10(-2) mol L(-1) with a near-Nernstian slope of (-58.6 +/- 1.3) mV decade(-1) and a detection limit of 4.3 x 10(-7) mol L(-1). The potentiometric response is independent of the pH of the solution in the pH range 6.0-9.0. The electrode is easily constructed at a relatively low-cost with fast response time (within 15-30 s) and can be used for a period of 4 months without significant change in its performance characteristics. The proposed sensor displayed good selectivities over a variety of other anions (carboxylates and inorganic anions). The potentiometric sensor was successfully applied to the determination of sorbic acid in real food samples, that is, soft drinks, skim yogurts, jams and sauces. (C) 2009 Elsevier Ltd. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Carbon Nuclear Magnetic Resonance Spectroscopic Profiles coupled to Partial Least-Squares Multivariate Regression for Prediction of Several Physicochemical Parameters of Brazilian Commercial Gasoline

Brazilian commercial gasoline follows a rigid quality control, regulated by Brazilian Government Petroleum, Natural Gas, and Biofuels Agency, ANP, following international analytical protocols, such as ASTM and ABNT, covered by Regulation ANP No. 309. Each property is a complicated function of the gasoline chemical composition, which would be represented by diverse types of mathematical correlations. However, these correlations are not adjusted to Brazilian gasoline, whose chemical composition is modified by anhydrous ethanol addition. The purpose of this work is to find correlations, using partial least-squares (PLS) regressions, between C-13 NMR Brazilian gasoline fingerprintings and several physicochemical parameters, such as relative density, distillation curve (temperatures related to 10, 50, and 90% of distilled volume, final boiling point and residue), octane numbers (motor and research octane number and antiknock index), hydrocarbon compositions (olefins, aromatics, and saturated) and anhydrous ethanol and benzene. 150 representative gasoline samples, collected randomly from different gas stations, were analyzed following international analytical protocols. All C-13 NMR spectroscopic fingerprintings, reported in parts per million (ppm), FIDs (free induction decays) were zero filled and Fourier transformed. A data matrix, composed of C-13 NMR chemical shifts and physicochemical parameters, was constructed and used in PLS regression. C-13 NMR fingerprinting of 100 gasoline samples were employed in the training set, and 50 samples formed the prediction set. In C-13 NMR-PLS models, root-mean square error of calibration (RMSEC) and prediction (RMSEP) were the mains parameters considered to select the "best model", which shown results roughly similar in magnitude to the repeatability and reproducibility of ASTM and NBR officials analytical protocols. C-13 NMR-PLS multivariate regression, as an alternative analytical methodology, offers an appealing procedure for commercial automotive gasoline quality control.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq