ABSTRACT Folic acid is a B complex water-soluble vitamin that is essential to humans, and its deficiency can cause problems including congenital malformations in the fetus as well as heart disease. Most countries affected by diseases associated with a lack of folic acid now supplement foods with the vitamin. There is therefore a need for the development of new analytical procedures able to determine folic acid present in different matrices. This work describes the development of zero order and first order derivative spectrophotometric methods for the determination of folic acid in different pharmaceutical formulations, using 0.1 mol L-1 NaOH as solvent. The methods are shown to be simple, selective, and robust. Good linearity was achieved, with correction coefficients ≥0.9996 and limits of detection and quantification ranging from 0.64 to 0.75 and from 1.80 to 2.85 mg L-1, respectively. Recoveries of 98-104% were obtained in accuracy tests, and precision (as RSD) was between 0.2 and 4.8%. The methods can be used in routine analyses for quality control purposes, offering an alternative to the procedures already reported in the literature.

Simple, sensitive and accurate spectrophotometric derivative methods were developed for the simultaneous determination of olanzapine and fluoxetine hydrochloride in pharmaceutical formulations by derivative spectrophotometry. On all orders of derivative studied, the linear response range was 10 to 60 mg L-1, with limit of quantitation (LoQ) ranging from 0.73 to 1.49 mg L-1 for fluoxetine hydrochloride and from 0.18 to 0.96 mg L-1 for olanzapine. The best orders for derivative analyses showed recoveries ranging from 99 to 103% and from 98 to 100%, and inter-day accuracy < 2.1% and < 2.8%, for fluoxetine hydrochloride and olanzapine, respectively.

Spectrophotometric methods of zero order, first and second derived order had been developed for olanzapine determination in tablets using ethanol and isopropanol as solvent. The two solvents revealed to be adequate. For the three methods the calibration curve coefficient of correlation had been greater than 0.9998 with limit of detection varying from 0.068 to 0.190 mg L-1, in ethanol, and 0.026 to 0.205 mg L-1, in isopropanol. The inter-day precision was inferior to 1.1 and 1.9 mg L-1 for ethanol and isopropanol, respectively. The average recoveries varied from 98 to 101%, in ethanol and 99 to 103% in isopropanol.

Vitamin C degradation was evaluated in industrialized cashew juice of high pulp content and in cajuina by the method of Tillmans during eleven days of storage after the opening of the flask. For recently opened juices, vitamin C was found in the concentration range of 112 to 170 mg for 100 g of juice. The degradation of vitamin C in industrialized cashew juices changes when different additives are used. All of the cajuinas presented a vitamin C content below that specified on the label.

The concentrations of Cu, Pb, Zn, Cr, Ni, Al, Mn and Fe were measured by atomic absorption spectrometry, of 19 topsoil samples collected in the Teresina city urban area to discriminate natural and anthropic contributions and identify possible sources of pollution. The average concentrations of Cu, Zn, Pb and Cr of the urban soils were 6.11, 8.56, 32.12 and 7,17 mg/kg-1, respectively. Statistical analysis techniques, such as principal component analysis (PCA) and hierarchical cluster analysis (HCA), were used to analyze the data. Mn, Ni and Cr levels were interpreted as natural contributions, whereas Pb, Zn and, in part, Cu were accounted for mainly by anthropic activities. High Pb levels were observed in the ancient avenues.

This essay describes a new didactic approach, in according with the national curriculum guidelines for chemistry undergraduate courses in Brazil, employed during the one-semester course "Experimental General Chemistry" for chemistry undergraduate students at the Federal University of Piauí. The new approach has positively helped student's training by improving their reading skills and their understanding of scientific reports, by developing the use of electronic tools to search and to recover the required knowledge for their learning activities, and by improving their skills of understanding published texts and dealing with digital sources. At the same time the students are strongly stimulated to enter the research program for undergraduate students available at the University.

Esta pesquisa foi conduzida para avaliar a qualidade nutricional das refeições consumida pelas crianças, pertencentes à faixa etária de 2 a 6 anos, matriculadas em creches municipais de Teresina. Os dados foram obtidos durante o período de outubro de 1997 a março de 1998, adotando-se o método da pesagem direta dos alimentos. Para o cálculo da adequação nutricional utilizaram-se as médias do consumo de energia e nutrientes, comparadas às recomendações nacionais. O estudo revelou oferta insuficiente de energia, ferro, cálcio e vitamina A, com um consumo protéico e de vitamina C excedendo as recomendações. Os carboidratos contribuíram com 58,5 ± 3,0% das energias totais, as proteínas com 16,0 ± 1,3% e as gorduras com 25,5 ± 3,7%. A deficiência de energia e a inadequação de proteínas e demais nutrientes demonstram a necessidade de um contínuo monitoramento das metas do programa e o aperfeiçoamento do serviço visando à melhoria da qualidade das dietas, com especial atenção ao atendimento das recomendações nutricionais.

This investigation was carried out to evaluate the nutritional quality of the meal consumed by the children from 2 to 6 years old registered at municipal day-care centers in Teresina. The data were acquired in the period from October/97 to March/98, with the weighing of the food. For the calculation of suitability of the diets it was used the averages of the consumption of energy and nutrients, compared to the national recommendations. The study revealed insufficient offer of energy, iron, calcium and vitamin A. The protein and vitamin C were over the recommendation. The carbohydrate contributed with 58.5 ± 3.0% of the total calories, the proteins with 16.0 ± 1.3% and the fats with 25.5 ± 3.7%. The dietetic information showed a need to adopt a policy of seeking improvement of the quality of the diets, with special attention to the attendance of the nutritional recommendations.

The modern technological ability to handle large amounts of information confronts the chemist with the necessity to re-evaluate the statistical tools he routinely uses. Multivariate statistics furnishes theoretical bases for analyzing systems involving large numbers of variables. The mathematical calculations required for these systems are no longer an obstacle due to the existence of statistical packages that furnish multivariate analysis options. Here basic concepts of two multivariate statistical techniques, principal component and hierarchical cluster analysis that have received broad acceptance for treating chemical data are discussed.