Sonia Claudia do Nascimento de Queiroz

Métodos de extração e/ou concentração de compostos encontrados em fluidos biológicos para posterior determinação cromatográfica

When organic compounds present in biological fluids are analysed by chromatographic methods, it is generally necessary to carry out a prior sample preparation due the high complexity of this type of sample, especially when the compounds to be determinated are found in very low concentrations. This article describes some of the principal methods for sample preparation in analyses of substances present in biological fluids. The methods include liquid-liquid extraction, solid phase extraction, supercritical fluid extraction and extraction using solid and liquid membranes. The advantages and disadvantages of these methods are discussed.

Relationships of the minerals and fatty acid contents in processed turkey meat products

Abstract In this paper, the chemical composition of a set of processed foods made of turkey meat, including meatball, blanquet, hamburger, smoked chest, ham, smoked ham, roule and frankfurter, are reported. Each product was analyzed for content of saturated fats, mono- and polyunsaturated fats, non-identified fats, calcium, iron, phosphorus, magnesium, potassium, sodium and zinc. In average, fatty acids are present in approximately equivalent percent concentrations, i.e. saturated:monounsaturated:polyunsaturated ≅1:1:1. Sodium, the major mineral ranged from 681 to 1327 mg per 100 g of processed meat. Iron and calcium concentration ranges were 0.4–2.2 and 3.0–43.6 mg/100 g, respectively. The results were analyzed by the multivariate techniques, hierarchical cluster analysis (HCA) and principal component analysis (PCA). It was shown that HCA can group all the samples, according to their types, and into some extent also according their basic composition (only dark meat, white meat, meat with shortening added and frankfurter as single cluster). On the other hand PCA could better expose the relationship between the products according to their fatty acids and mineral composition. PC 1 discriminates fatty/lean products, while PC 2 discriminates the frankfurters by its content of salts added, Ca and Fe from milk and soy, all added during processing, and finally PC 4 which discriminates the white/dark meat products through Zn concentration from dark meat.

Resíduos de agrotóxicos em alimentos: uma preocupação ambiental global - Um enfoque às maçãs

This paper describes the use of pesticides in agriculture. Research has shown that significant quantities of pesticide residues have been found in many types of foods. Thus, an overview is given of pesticide residue determinations in fruits and vegetables, with special attention to apples. The toxicity and the adverse effects possibly caused by the exposure of these compounds are alerting the scientific community to develop studies about the validation of analytical methods for multiresidue pesticide determination in these samples. This review shows that pesticide-residue determination in apples is becoming a very important and challenging issue.32nd Annual Meeting of the Sociedade-Brasileira-de-Quimica : MAY 30-JUN 02, 2009 : Fortaleza, BRAZIL : Soc Brasileira Quim :

Determinação dos teores de minerais em sucos de frutas por espectrometria de emissão óptica em plasma indutivamente acoplado (ICP-OES)

Two sample preparation methods for the determination of minerals from grape juice were investigated for the purpose of methodological evaluation: using hydrochloric acid by shaking, and digestion in closed system, under pressure, using microwave power. The concentrations of minerals were evaluated by the technique of Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The minerals contents of Ca, P, Na, K, Mg, Zn, Fe, Mn, and Cu did not differ significantly at the level of 5% (it Tests F) for both methodologies used. The precision and accuracy of both methodologies were evaluated using grape juice. The extraction methodology with hydrochloric acid was used for the determination of mineral amounts in processed juices from pineapple, acerola, cashew, guava, mango, passion fruit and grape. To enhance the interpretation of the amounts of minerals, from a nutritional point of view, techniques of Principal Components Analysis (PCA) and Hierarchic Cluster Analysis were used (HCA).

Poly(methyloctadecylsiloxane) immobilized on silica by γ radiation for use in solid-phase extraction

This work presents a fast, easy and effective procedure to obtain silica-based C18 type sorbents for use in solid-phase extraction (SPE). The solid-phase was made by depositing a polymer, poly(methyloctadecylsiloxane) (PMODS), on the silica support followed by immobilization using gamma irradiation. The method presents an application of green chemistry in the analytical laboratory, since there are no toxic residues after the synthesis. Water samples spiked with a mixture of pesticides (benomyl, tebuthiuron, diuron, simazine, atrazine and ametryn) were extracted in the off-line mode in order to evaluate the performance of this sorbent.

Novos sorventes baseados em poli (metiloctilsiloxano) sobre sílica para uso em extração em fase sólida

This paper presents an easy and practical procedure to obtain silica-based C-8 type sorbents for use in solid-phase extraction. The materials are prepared by depositing poly(methyloctylsiloxane), PMOS, on the silica support. Two different treatments for immobilization were used: thermal treatment or gamma irradiation. Suitable recoveries were obtained after pre-concentration of dilute solutions, at the ng/L level, of a mixture of pesticides, indicating the good performance of the materials.