Application of differential scanning calorimetry in hair samples as a possible tool in Forensic Science

The Differential Scanning Calorimetry (DSC) was used to study the thermal behavior of hair samples and to verify the possibility of identifying an individual based on DSC curves from a data bank. Hair samples of students and officials from Instituto de Química de Araraquara, UNESP were obtained to build up a data bank. Thus to sought an individual, under incognito participant of this data bank, was identified using DSC curves.

Thermal behavior of alginic acid and its sodium salt

An evaluation of hydration and thermal decomposition of HAlg and its sodium salt is described using thermogravimetry (TG) and differential scanning calorimetry (DSC). TG curves in N2 and air, were obtained for alginic acid showed two decomposition steps attributed to loss of water and polymer decomposition respectively. The sodium alginate decomposed in three steps. The first attributed to water loss, followed by the formation of a carbonaceous residue and finally the Na2CO3. DSC curves presented peaks in agreement with the TG data. In the IR alginic acid presented bands at 1730 and 1631 cm-1, while sodium alginate presented a doublet at 1614 e 1431 cm-1, evidencing the presence of salified carboxyl groups.

Utilização de um eletrodo de grafite recoberto com PbO2 incorporado em matriz de PVC como eletrodo indicador em titulações coulométricas

A aplicação de um eletrodo sensível a íons H3O+, obtido pelo recobrimento de um eletrodo de grafite com uma membrana polimérica contendo PbO2 incorporado em uma matriz de PVC (PbO2-PVC), como eletrodo indicador em titulações coulométricas de neutralização, foi investigada. As leituras dos potenciais foram feitas usando o eletrodo indicador de PbO2-PVC e para comparação dos resultados foi usado um eletrodo de vidro combinado (EVC). As curvas de titulação monitoradas com o eletrodo de PbO2-PVC apresentaram características semelhantes àquelas monitoradas com o EVC e os tempos de equivalência obtidos foram concordantes a um nível de confiança de 95%. O eletrodo de PbO2-PVC apresentou resposta linear no intervalo de pH 2 a 12 com inclinação de Nernst de -57,6 ± 0,1 mV/pH (r= 0,9998), sendo o tempo de resposta deste eletrodo bem menor do que aquele obtido com o EVC. O eletrodo de PbO2-PVC é de fácil construção, possui baixo custo e tempo de vida útil superior a 4 meses, equivalente a (pelo menos 1200 determinações por membrana polimérica).

Determinação do mecanismo de destruição de células mediado por meso-tetramesitylporfirina, octaetilporfirina, octaetilporfirina de vanadil e luz visível

A Terapia Fotodinâmica é um tratamento clínico empregado no combate a vários tipos de tumores. Nesta técnica, o paciente recebe uma certa dosagem de uma substância fotossensibilizadora que, por sua vez, acumula-se preferencialmente no tecido tumoral. Em seguida irradia-se luz visível, neste tecido, com a finalidade de se excitar o fotossensibilizador. Esta substância, excitada, pode transferir elétrons e/ou energia para o oxigênio, no estado fundamental, gerando espécies reativas de oxigênio como o radical superóxido e oxigênio singlete. O primeiro é gerado no mecanismo tipo I, pela transferência de elétrons, e o segundo no mecanismo tipo II, pela transferência de energia. Estas espécies reativas geram um estresse oxidativo, no tecido tumoral, levando as células cancerígenas à morte. Neste trabalho, foram avaliadas as propriedades fotossensibilizadoras de três porfirinas e constatou-se que as mesmas são capazes de destruir células, na presença de luz e oxigênio. Este evento foi mais pronunciado, na presença de água deuterada, e inibido por supressores de oxigênio singlete, indicando predominância do mecanismo tipo II.

Synthesis, characterization and thermal behaviour of solid state compounds of 4-methoxybenzoate with Manganese, Nickel and Copper

Solid state M-L compounds, where M stands for bivalent Mn, Ni, Cu and L is 4-methoxybenzoate, have been synthesized. Simultaneous thermogravimetry - differential thermal analysis (TG-DTA), X-ray powder diffractometry, infrared spectroscopy, elemental analysis and complexometry were used to characterize and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration, thermal stability and thermal decomposition of the isolated compounds.

Determinação de paracetamol em produtos farmacêuticos empregando um sistema de análise por injeção em fluxo com geração de ácido nitroso

O uso do ácido nitroso para determinação de paracetamol (acetoaminofenol) em formulações sólidas e líquidas empregando um sistema de análise por injeção em fluxo é descrito. A determinação da droga foi realizada pela reação do paracetamol com ácido nitroso gerado em linha e o produto dessa reação foi monitorado em 430 nm em meio alcalino. A curva analítica apresentou uma faixa de concentração de paracetamol variando entre 9,7x10-5 a 6,2x10-3 mol L-1 com um limite de detecção de 2,5x10-5 mol L-1. Os desvios padrão relativos foram menores que 2% para soluções contendo 1,2x10-4 e 2,8x10-4 mol L-1 de paracetamol (n=10) e uma freqüência de amostragem de 60 determinações por hora foram obtidos. Os resultados da determinação de paracetamol nas formulações farmacêuticas obtidas pelo procedimento em fluxo proposto estão em boa concordância com os resultados obtidos utilizando-se o procedimento da Farmacopéia Americana a um nível de confiança de 95% e dentro de uma faixa aceitável de erro.

Spectrophotometric determination of diclofenac in pharmaceutical preparations assisted by microwave oven

In this work, an effective and low-cost method for the determination of sodium or potassium diclofenac is proposed in its pure form and in their pharmaceutical preparations. The method is based on the reaction between diclofenac and tetrachloro-p-benzoquinone (p-chloranil), in methanol medium. This reaction was accelerated by irradiating of reactional mixture with microwave energy (1100 W) during 27 seconds, producing a charge transfer complex with a maximum absorption at 535 nm. The optimal reaction conditions values such as reagent concentration, heating time and stability of the reaction product were determined. Beer's law is obeyed in a concentration range from of 1.25x10-4 to 2.00x10-3 mol l-1 with a correlation coefficient of 0.9993 and molar absorptivity of 0.49 x10³ l mol-1 cm-1. The limit of detection (LOD) was 1.35x10-5 mol l-1 and the limit of quantification (LOQ) was 4.49x10-5 mol l-1. In the presence of the common excipients, such as glucose, lactose, talc, starch, magnesium stearate, sodium sulphite, titanium dioxide, polyethyleneglycol, polyvinylpirrolidone, mannitol and benzilic alcohol no interferences were observed. The analytical results obtained by applying the proposed method compare very favorably with those given by the United States Pharmacopeia standard procedure. Recoveries of diclofenac from various pharmaceutical preparations were within 95.9% to 103.3%, with standard deviations ranging from 0.2% to 1.8%.

Lychnophoric acid from Lychnophora pinaster: a complete and unequivocal assignment by NMR spectroscopy

The investigation of the hexane extract from aerial parts of Lychnophora pinaster provided, besides others substances, the E-isomer of lychnophoric acid, a sesquiterpene derivative previously isolated from L. affinis.

Synthetic model of a new deoxybenzoin derivative from Deguelia hatschbachii A.M.G. Azevedo

In this paper we describe the synthesis of 2´,4´-dimethoxy-8-(propyl-2-one)-deoxybenzoin, a new compound employed as a model for the comparison with the respective spectral data for 6',4-dihydroxy-3'-(3,3- dimethylallyl)-2",2"-dimethylchromene(5",6":5',4')-2'-methoxy-8-(propyl-2-one) deoxybenzoin, recently isolated from Deguelia hatschbachii A.M.G. Azevedo. Both compounds have a "propyl-2-one" group attached to C-8 of the deoxybenzoin skeleton, for which there is no precedent in the literature. The Friedel-Crafts reaction of 1,3-dimethoxybenzene with phenylacetyl chloride furnished 2´,4´-dimethoxydeoxybenzoin, that after reaction with allyl bromide gave 2´,4´-dimethoxy-8-(allyl)-deoxybenzoin . Wacker oxidation gave the desired model compound in 15% overall yield. The corresponding spectral data reinforced the structure previously determined for the natural product.

The Li+, Na+ and K+ ion exchange reaction process on the surface of mixed oxide SiO2/TiO2/Sb2O5 surface prepared by the sol-gel processing method

The porous mixed oxide SiO2/TiO2/Sb2O5 obtained by the sol-gel processing method presented a good ion exchange property and a high exchange capacity towards the Li+, Na+ and K+ ions. In the H+/M+ ion exchange process, the H+ / Na+ could be described as presenting an ideal character. The ion exchange equilibria of Li+ and K+ were quantitatively described with the help of the model of fixed tetradentate centers. The results of simulation evidence that for the H+ / Li+ exchange the usual situation takes place: the affinity of the material to the Li+ ions is decreased with increasing the degree of ion exchange. On the contrary, for K+ the effects of positive cooperativity, that facilitate the H+ / K+ exchange, were revealed.

Synthesis, structural and morphological characterization of CeO2-ZnO nanosized powder systems from Pechini's method

This work reports on the investigation of nanosized CeO2-ZnO systems prepared by Pechini's method. The structural and morphological characterization of CeO2-ZnO systems as well as the characterization of CeO2 and ZnO separately, showed that the employed method result in powders with spheroidal particles whose size are in the range 30 - 200 nm, which is appropriate to provide homogeneous suspensions. The ZnO present in the prepared mixed oxides seems to increase particle size distribution and to influence the arrangement of the particles after powder dispersion.

Use of experimental design in the optimisation of a solid phase preconcentration system for Cobalt determination by GFAAS

In this work is proposed a solid phase preconcentration system of Co2+ ions and its posterior determination by GFAAS in which fractional factorial design and response surface methodology (RSM) were used for optimization of the variables associated with preconcentration system performance. The method is based on cobalt extraction as a complex Co2+-PAN (1:2) in a mini-column of polyurethane foam (PUF) impregnated with 1-(2-pyridylazo)-naphthol (PAN) followed by elution with HCl solution and its determination by GFAAS. The chemical and flow variables studied were pH, buffer concentration, eluent concentration and preconcentration and elution flow rates. Results obtained from fractional factorial design 2(5-1) showed that only the variables pH, buffer concentration and interaction (pH X buffer concentration) based on analysis of variance (ANOVA) were statistically significant at 95% confidence level. Under optimised conditions, the method provided an enrichment factor of 11.6 fold with limit of detection and quantification of 38 and 130 ng L-1, respectively, and linear range varying from 0.13 to 10 µg L-1. The precision (n = 9) assessed by relative standard deviation (RSD) was respectively 5.18 and 2.87% for 0.3 and 3.0 µg L-1 cobalt concentrations.

Atividade eletrocatalítica de eletrodos compostos por Pt, RuO2 e SnO2 para a eletrooxidação de formaldeído e ácido fórmico

A atividade eletrocatalítica para a oxidação de ácido fórmico e formaldeído em eletrodos binários de Pt e SnO2 e ternários de Pt, RuO2 e SnO2 em diferentes composições, foi investigada através das técnicas de voltametria cíclica e cronoamperometria. Os materiais foram preparados por decomposição térmica de precursores poliméricos na temperatura de 400°C. Os experimentos de voltametria cíclica mostraram que os eletrodos mistos proporcionaram uma diminuição de ~100 mV (ERH) no potencial de pico de oxidação das moléculas orgânicas em relação ao eletrodo contendo somente Pt e indicaram que a composição Pt0,6Ru0,2Sn0,2Oy possui maior densidade de corrente de oxidação em potenciais inferiores ao potencial de pico. Os experimentos de cronoamperometria confirmam a contribuição da adição de SnO2 e RuO2 para o aumento da atividade catalítica em menores valores de potencial.

Thermal annealing effects on vanadium pentoxide xerogel films

The effect of water molecules on the conductivity and electrochemical properties of vanadium pentoxide xerogel was studied in connection with changes of morphology upon thermal annealing at different temperatures. It was demonstrated that the conductivity was increased for the samples heated at 150ºC and 270ºC compared to the vanadium pentoxide xerogel. It was also verified a stabilization of electrochemical processes of the insertion and de-insertion of lithium ions the structure of thermally annealed vanadium pentoxide.

Determination of hydrochlorothiazide in pharmaceutical formulations by diffuse reflectance spectroscopy

This paper describes a method for quantitative spot test analysis of hydrochlorothiazide using diffuse reflectance spectroscopy. The reflectance measurements were performed analyzing the colored compound (l = 585 nm) produced from the reaction between hydrochlorothiazide and p-dimethylaminocinnamaldehyde (PDAC) in acid medium. This reaction occurred on filter paper after heating to 80ºC for 8 minutes. Factorial designs allowed varying multiple reaction factors simultaneously in order to obtain the best reaction conditions. These factors included heating temperature, heating time, acid volume and PDAC volume. The linearity was studied in the range of 3.36x10-2 to 1.01x10-1 mol L-1 with a correlation coefficient of 0.998. The limit of detection was estimated to be 1.32x10² mol L-1. Commercial samples were analyzed using the proposed method and the results were favorably compared with those of the United States Pharmacopeia method, showing that quantitative spot test analysis by diffuse reflectance could be successfully used to determine hydrochlorothiazide in medicines.