Produção de monoacilgliceróis e diacilgliceróis via glicerólise enzimática e destilação molecular

Monoacilglycerides and diacilglycerides are produced through lipase-catalyzed glycerolysis of soybean oil using Candida antarctica B in a solvent-free system. The reaction was carried out at a glycerol to triacylglycerol molar ratio of 8:1 with 2% of lipase. Acylglycerides, free fatty acids (FFA) and glycerol produced were separated employing the molecular distillation process. Starting from a product of enzymatic reaction 25.06% of triacylglycerols, 46.63% of diacylglycerides, 21.72% of monoacylglycerides, 5.38% of FFA and 1.21% of glycerol and after consecutively distillations, monoacylglycerides with 80% of purity was obtained and also oil with 54% of diacylglycerides to be used in human dietary.

Modelagem da combustão da dinitramida de amônio por simulação computacional

In this work, the combustion process of ammonium dinitramide, ADN, has been modeled in two different situations: decomposition in open environment, with abundant air and decomposition in a rocket motor internal environmental conditions. The profiles of the two processes were achieved, based on molar fractions of the species that compose the products of ADN combustion. The velocity of formation and quantity of species in the open environment was bigger than the ones in the rocket motor environment, showing the effect of the different atmosphere in the reactions kinetics.

Síntese enzimática de butirato de isoamila empregando lipases microbianas comerciais

Isoamyl butyrate production was investigated using free and immobilized lipases by esterification of butyric acid with isoamyl alcohol in a solvent-free system and in an organic media. Among the enzymes studied, Lipozyme TL IM was found to be the most active catalyst in n-hexane as a solvent. The effects of different solvents and the amount of water added on conversion rates were studied. A maximum conversion yield of 80% in n-hexano at 48 h was obtained under the following conditions: 3 g L-1 of Lipozyme TL IM, 30 ºC, 180 rpm of agitation, isoamyl alcohol to butyric acid molar ratio of 1:1 and acid substrate concentration of 0.06 M.

Alternativa potencial para aproveitamento do glicerol gerado na produção de biodiesel: síntese enzimática de monolaurina por esterificação

Esterification reactions of glycerol with lauric acid in solvent free system were carried out using lipases from several sources. All lipases were immobilized on polysiloxane-polyvinyl alcohol particles by covalent binding with high activity recovered. Among the tested enzymes, the Candida antarctica lipase allowed to attain the highest molar conversion (76%), giving similar proportions of monolaurin, dilaurin and low amount of trilaurin. To further improve the process, the Response Surface Methodology (RSM) was used and optima temperature and molar ratio glycerol to lauric acid were found to be 45 ºC and 5:1, respectively. Under these conditions, 31.35% of monolaurin concentrations were attained and this result was in close agreement with the statistical model prediction.

Método extendido de Hildebrand en la predicción de la solubilidad del ketoprofeno en mezclas cosolventes etanol + agua

Extended Hildebrand Solubility Approach (EHSA) developed by Martin et al. was applied to evaluate the solubility of ketoprofen (KTP) in ethanol + water cosolvent mixtures at 298.15 K. Calculated values of molar volume and solubility parameter for KTP were used. A good predictive capacity of EHSA was found by using a regular polynomial model in order five to correlate the W interaction parameter and the solubility parameters of cosolvent mixtures (δmix). Nevertheless, the deviations obtained in the estimated solubilities with respect to the experimental solubilities were on the same order like those obtained directly by means of an empiric regression of the logarithmic experimental solubilities as a function of δmix values.

Determinação espectrofotométrica de cefalexina em formulações farmacêuticas explorando a sua reação de transferência de carga com a quinalizarina

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.

Selective and non-extractive spectrophotometric determination of cefdinir in formulations based on donor-acceptor complex formation

Cefdinir has broad spectrum of activity and high prescription rates, hence its counterfeiting seems imminent. We have proposed a simple, fast, selective and non-extractive spectrophotometric method for the content assay of cefdinir in formulations. The method is based on complexation of cefdinir and Fe under reducing condition in a buffered medium (pH 11) to form a magenta colored donor-acceptor complex (λ max = 550 nm; apparent molar absorptivity = 3720 L mol-1 cm-1). No other cephalosporins, penicillins and common excipients interfere under the test conditions. The Beer's law is followed in the concentration range 8-160 µg mL-1.

Development of a flotation-spectrophotometric method for determination of cetylpyridinium chloride in pharmaceutical products

A new simple and sensitive flotation-spectrophotometric method for the determination of cetylpyridinium chloride (CPC) is reported. The method is based on the formation of an ion- associate between CPC and Orange II (OR) which is floated in the interface of aqueous phase and n-hexane by vigorous shaking. The aqueous solution was discarded and the adsorbed ion associate on to the wall of a separating funnel was dissolved in a small volume of methanol solvent and its absorbance was measured at 480 nm. The apparent molar absorptivity (Ε) of the ion associate was determined to be 4.12 x 10(5) L mol-1 cm-1. The calibration graph was linear in the concentration range of 15-800 ng mL-1 of CPC with a correlation coefficient of 0.9988. The limit of detection (LOD) was 10.8 ng mL-1. The relative standard deviation (RSD) for determination of 100 and 800 ng mL-1 of CPC was 3.47 and 2.04% (n=7), respectively. The method was successfully applied to the determination of CPC in a commercial mouth washer product.

Studies on the development of spectrophotometric method for the determination of haloperidol in pharmaceutical preparations

A spectrophotometric method based on the formation of ion-pair complex between haloperidol and eriochrome black T (EBT) at pH 1.85 has been described. The formed complex was extracted quantitatively into chloroform and measured at 510 nm. Infra red (IR) studies were performed to confirm the formation of ion-pair complex. Beer's law was obeyed in the concentration range of 2.0-9.0 µg mL-1 with molar absorptivity of 2.67 × 10(4) L mol-1 cm-1. The detection limit was found to be 0.18 µg mL-1. Statistical comparison of the results of the proposed method with those of the reference method shows excellent agreement and indicates no significant difference in accuracy and precision.

Fracionamento de cobre em proteínas do plasma, músculo e fígado de tilápia do Nilo

Copper fractionation in plasma, muscle and liver of Nile tilapia was performed after protein separation by 2D-PAGE. SR XRF analysis indicated the presence of copper in three protein spots of plasma, and in two protein spots of muscle and liver, respectively. Copper ions were found to be distributed mostly in proteins that had a molar mass of less than 54 kDa and greater than 13 kDa and a pI in the 5.3-9.3 range. The copper concentration bound to these proteins was determined by GFAAS which showed concentrations in the 1.20-4.82 mg g-1 range.

Photochemical characteristics of diclofenac and its photodegradation of inclusion complexes with β-cyclodextrins

Diclofenac is one of most frequently detected compounds in the water cycle. In this work, the effect of initial concentration, liquid inclusion complexes with β-Cyclodextrins (β-CDs) on the photodegradation of diclofenac were studied. Six phototransformation products were detected by HPLC chromatograms. UV-absorption spectra of diclofenac and phototransformation products were determined. One of the phototransformation products was identified. The degradation followed pseudo-first-order kinetics. The experiment showed that irradiation of diclofenac in the presence of β-CDs increase photodegradation rate and determined the optimal molar ratio of diclofenac to β-CDs as 1:2. The reduced photohaemolytic activity of diclofenac in the presence of β-CDs may be attributed to the sequestering and stabilizing of the radical intermediates and /or photoproducts by complexation.

Caracterização química dos géis produzidos pelas bactérias diazotróficas Rhizobium tropici e Mesorhizobium sp.

The exopolysaccharides with characteristics of gel produced by Rhizobium tropici (EPS RT) and Mesorhizobium sp (EPS MR) are acidic heteropolysaccharide composed mainly of glucose and galactose in a molar ratio of 4:1 and 5:1 respectively, with traces of mannose (~ 1%). Chemical analysis showed the presence of uronic acid, pyruvate and acetyl-substituents in the structures of both polymers. Experiments of gel permeation chromatography and polyacrylamide gel electrophoresis showed that EPS RT and EPS MR are homogeneous molecules with low grade of polydispersity. The EPS were characterized using spectroscopic techniques of FT-IR, ¹H and 13C-NMR.

Preparation of association compound between rhodium(II) citrate and β-cyclodextrin

Inclusion compound of rhodium(II) citrate with β-cyclodextrin in a 1:1 molar ratio was prepared using freeze-drying method. X-ray diffactometry, thermal analysis (TG/DTG/DSC), infrared and ¹H-NMR with ¹H spin lattice relaxation (¹H T1) measurements and 13C techniques were used to characterize the system prepared. The results indicated the formation of inclusion or association compounds between rhodium(II) citrate and β-cyclodextrin.

Caracterização composicional e transesterificação de óleo de microalga: uma abordagem computacional

A procedure for compositional characterization of a microalgae oil is presented and applied to investigate a microalgae based biodiesel production process through process simulation. The methodology consists of: proposing a set of triacylglycerides (TAG) present in the oil; assuming an initial TAG composition and simulating the transesterification reaction (UNISIM Design, Honeywell) to obtain FAME characterization values (methyl ester composition); evaluating deviations of experimental from calculated values; minimizing the sum of squared deviations by a non-linear optimization algorithm, with TAG molar fractions as decision variables. Biodiesel from the characterized oil is compared to a rapeseed based biodiesel.

Application of ftir in the determination of acrylate content in poly(sodium acrylate-co-acrylamide) superabsorbent hydrogels

Hydrogels have been prepared by free-radical solution copolymerization of acrylamide and sodium acrylate (NaAc), with molar ratio ranging from 25/75 to 80/20, respectively, using methylene bisacrylamide as the crosslinking agent. A FTIR spectroscopy procedure to determine the acrylate/acrylamide ratio in these hydrogels was proposed based on absorbance at 1410 cm-1 (nCOO-) and 2940 cm-1 (nCH and nCH2). A straight line with a good linear correlation coefficient (0.998) was obtained by plotting the acrylate content (Ac%) versus relative absorbance (Arel = A1410/A2940). Results were confirmed by the amount of sodium cation released in acid medium determined by atomic absorption spectrometry.