Electrochemical behavior of N-nitrosothiazolidine carboxilic acid on gold and mercury electrodes

The electrochemical behavior of N-nitrosothiazolidine carboxylic acid (NTAC) on gold and hanging mercury electrodes, using the cyclic and square wave voltammetries, was studied. Whereas NTAC suffer reduction in a single step on the mercury electrode, two peaks appears on the cyclic voltammograms on the gold electrode, one anodic peak overlaying the gold oxide process at 1.2 V and one cathodic peak at -0.41 V vs Ag/AgCl, KCl 3.0 mol L-1. The cathodic peak depends on the previous oxidation of NTAC at the electrode surface, presents irreversible and adsorption controlled characteristics and it is suitable for quantitative purposes.10671072Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Aspectos analíticos e regulatórios na determinação de resíduos de macrolídeos em alimentos de origem animal por cromatografia líquida associada à espectrometria de massas

This is an overview of LC-MS techniques applied for macrolide determination in food, including sample preparation and method validation, as well as the policies adopted by international agencies regarding their presence in food. Techniques for the analysis of macrolides in food normally include solid phase or liquid-liquid extraction followed by HPLC. UHPLC presents advantages in running time, detectability and solvent consumption. Triple-quadrupoles are the most common analyzers in instruments used for the determination of contaminants in food, but time-of-flight and ion-trap spectrometers have been successfully applied for analyses focusing on the investigation of structural formula or the presence of degradation products

Analytical and regulatory aspects for determination of macrolide residues in animal-derived foods by liquid chromatography associated with mass spectrometry

This is an overview of LC-MS techniques applied for macrolide determination in food, including sample preparation and method validation, as well as the policies adopted by international agencies regarding their presence in food. Techniques for the analysis of macrolides in food normally include solid phase or liquid-liquid extraction followed by HPLC. UHPLC presents advantages in running time, detectability and solvent consumption. Triple-quadrupoles are the most common analyzers in instruments used for the determination of contaminants in food, but time-of-flight and ion-trap spectrometers have been successfully applied for analyses focusing on the investigation of structural formula or the presence of degradation products.44946

GC-MS determination of organochlorine pesticides in medicinal plants harvested in Brazil

A method using Gas Chromatography coupled to Mass Spectrometry (GC-MS) for the determination of hexachlorobenzene, lindane, heptachlor, heptachlor epoxide, aldrin, dieldrin, endrin, 4,4'-DDT and 4,4'-DDE in leaves of Mikania laevigata, Maytenus ilicifolia and Cordia verbenacea was developed. Extraction of the pesticides was carried out by solid-liquid extraction (SLE), followed by clean-up in solid phase mixed cartridge (Florisil and silica-gel). Quantification was performed using GC-MS in the selected ion monitoring mode. Mean recovery rates of 70 to 124% were obtained. The inter-assay precision of a sample fortified with 200 ng g-1 of each pesticide was in the range of 1.0 to 7.3%. The quantitation limits ranged from 3.0 to 30 ng g-1 and were below the Maximum Residue Limit (MRL) for all the pesticides under study. The method was employed to analyze samples of Mikania laevigata, Maytenus ilicifolia and Cordia verbenacea from an experimental field in Paulínia, SP, Brazil. The samples presented contamination with dieldrin above the MRL established by the European Pharmacopoeia (50 ng g-1)

Dry matter accumulation and carbohydrate composition of a new cultivar of maize, "Sugary-Opaque-2-Waxy".

O acúmulo de matéria seca e a composição de carboidratos de uma nova cultivar de milho, o triplo mutante Sugary-Opaque-2-Waxy, foram estudados comparativamente em relação às cultivares Sugary-Opaque-2, Waxy-Sugary-Opaque-2 e uma cultivar de milho (Zea mays L.) normal. De uma maneira geral, todas as cvs. estudadas apresentaram, aos 25 dias após a polinização (DAP) teores semelhantes de açúcares solúveis redutores. As cultivares que continham o gene sugary apresentaram teores mais elevados de acúcares solúveis totais e de fitoglicogênio, em comparação com as cultivares com endospernia amiláceo. Uma relação inversa foi observada para o conteúdo de amido. A avaliação do acúmulo de matéria seca, em diferentes estádios de maturação, 15, 20, 25, 30 e 35 DAP, indicou que o milho normal e o triplo mutante apresentaram os maiores e menores valores de porcentagem de peso seco, respectivamente. O triplo mutante mostrou acúmulo de matéria seca mais lento do que seus ascendentes, proporcionando um período mais prolongado de colheita como milho verde, favorecendo o seu consumo in naturaDry matter accumulation and carbohydrate composition of a new cultivar of maize (Zea mays L.), te triple mutant Sugary-Opaque-2-Waxy, was comparatively studied in relation to the cultivars Sugary, Opaque-2, Waxy,Sugary-Opaque-2 and Maya Normal in general, all cultivars showed similar content of soluble reducing sugars. The cultivars with te sugary gene showed higher content of total soluble sugars and phytoglycogen than those with the starchy endosperm. The opposite was found to te starch content Maya Normal and te triple mutant showed, respectively, te higher and lower values for dry matter accumulation at the different stages of endosperm development (15, 20, 25, 30 and 35 days after poilination - DAP). The lower rate of dry matter accumulation suggests that te triple mutant would be more appropriate to be consumed as sweet corn

Validation of chromatographic methods for the determination of residues of veterinary drugs in foods

Different agencies that supply validation guidelines worldwide establish almost the same parameters to be evaluated in the validation process of bioanalytical methods. However, they recommend different procedures, as well as establish different acceptance criteria. The present review delineates and discusses the stages involved in the validation procedures of bioanalytical methods designed for determining veterinary residues in food, explaining the main differences in the guidelines established for this purpose by the main regulatory agencies in the world.1190119

Validação de métodos cromatográficos para a determinação de resíduos de medicamentos veterinários em alimentos

Different agencies that supply validation guidelines worldwide establish almost the same parameters to be evaluated in the validation process of bioanalytical methods. However, they recommend different procedures, as well as establish different acceptance criteria. The present review delineates and discusses the stages involved in the validation procedures of bioanalytical methods designed for determining veterinary residues in food, explaining the main differences in the guidelines established for this purpose by the main regulatory agencies in the world

Extraction of bioactive compounds from Peruvian purple corn cob by high isostatic pressure

The purple corn cob is an agro-industrial by-product that contains high-value bioactive compounds, which makes its use attractive for the development of extraction processes. The aim of this research was to extract the bioactive compounds from the purple corn cob by high isostatic pressure at different processing temperatures. Pressures of 0.01 MPa, 250 MPa, 450 MPa and 650 MPa for 3 minutes and at temperatures of 25 °C, 45 °C and 65 °C were used. High pressure extraction was compared with conventional extraction (2.5 h at 25°C). The purple corn cob extract obtained by isostatic processing at 650 MPa and 65 °C presented high antioxidant activity and content of bioactive compounds, unlike the conventional extraction of 2.5 h and 65 °C (p 0.05). Seven different anthocyanins were identified by liquid chromatography in the extracts obtained by high isostatic pressure (650 MPa at 65 °C) and hydroalcoholic maceration (2.5 h at 65 °C), mainly cyanidin-3-glucoside, pelargonidin-3-glucoside and peonidin-3-glucoside, and their respective malonyl derivatives. The high isostatic pressure increased the extraction of bioactive compounds by more than 50% and obtained them in shorter times, thus appearing as a new alternative, and eco-friendly method for the extraction of bioactive compounds from plant tissues

Yang-Mills instantons and dyons on homogeneous G_2-manifolds

We consider Lie G-valued Yang-Mills fields on the space R x G/H, where G/H is a compact nearly K"ahler six-dimensional homogeneous space, and the manifold R x G/H carries a G_2-structure. After imposing a general G-invariance condition, Yang-Mills theory with torsion on R x G/H is reduced to Newtonian mechanics of a particle moving in R^6, R^4 or R^2 under the influence of an inverted double-well-type potential for the cases G/H = SU(3)/U(1)xU(1), Sp(2)/Sp(1)xU(1) or G_2/SU(3), respectively. We analyze all critical points and present analytical and numerical kink- and bounce-type solutions, which yield G-invariant instanton configurations on those cosets. Periodic solutions on S^1 x G/H and dyons on iR x G/H are also given.Comment: 1+26 pages, 14 figures, 6 miniplot