O enfoque da metrologia química em análises toxicológicas na atividade turfística: validação de método analítico para determinação de cafeína em matrizes biológicas

This paper proposes an alternate method to detect forbidden doping substances present in biological matrices of horseracing. The method was fully validated for caffeine, identified as the most frequent forbidden substance in the analysis conducted by the Antidoping Laboratory of the Brazilian Jockey Club, which adopts a zero threshold limit according to national and international horseracing practices. The metrological reliability of the method applied to toxicological analysis in biological matrices is discussed. Although the analytical method proposed for detection of a zero threshold level of the doping substance is qualitative, it was validated for the determination of the limiting value (also known as quantification limit value) introducing a criterion that prevents the issuing of incorrect results ("false-positives" and "false-negatives").

Promovendo a argumentação no ensino superior de química

Studies have demonstrated the importance of argumentation in science education. Based on this assertion, we have tried to develop argumentative abilities in chemistry undergraduate students through a teaching methodology based on case studies. The process culminated with class presentations by student groups about possible solutions for the cases. To assess the quality of students' argumentation, videotapes of group presentations were collected and analyzed using Toulmin's Argument Pattern (TAP). TAP illustrates the nature of an argument in terms of claims, data, warrants, backings, and rebuttals. The findings of this work support the idea that the case study approach is an effective strategy for enhancing students' ability to argument.

Visões de meio ambiente e suas implicações pedagógicas no ensino de química na escola média

This study was realized with high school Chemistry teachers from the region of and around Florianópolis (SC). It examines the pedagogical implications of these teachers' views on environmental issues, and discusses the possibilities and difficulties of bringing these issues into the Chemistry classroom. The semi-structured interviews were analyzed using Textual Discourse Analysis principles. The dominance of content-based teaching and traditional pedagogical approaches appears to hinder curricular changes. Most subjects pay little heed to environmental issues and their relation to Chemistry, and endorse a view of science as neutral, and the environment as anthropocentric - views far from Green Chemistry principles.

Uma visão da química bioinorgânica medicinal

Metals play a vital role in human and plant physiology and important research is directed towards exploring the interrelated mechanisms that govern their interactions with biomolecules. Bioinorganic medicinal chemistry studies the functions, processing, storage and applications of metal ions and their complexes in biological systems. This paper presents a brief discussion about on interactions of metals with biomolecules that determine their intracellular accumulation, where metal ions may fulfill essential functions in cellular metabolism or, in certain cases, exert toxic effects towards cells.

Composição química e atividade biológica das folhas e frutos de Triphasia trifolia

The chemical composition of the essential oils from leaves and fruits of Triphasia trifolia was analyzed by GC-FID and GC-MS. The major constituents of oil obtained from leaves were sabinene (35.4%) and myrcene (34.1%), while the prevalent compounds in oil from fruits were sabinene (37.2%), beta-pinene (23.95) and gamma-terpinene (16.3%). Both oils showed moderate antimicrobial activity. The fruit decoction was also investigated leading to the isolation of the coumarins isopimpinelin, (R)-byakangelicin and (S)-mexoticin. From leaves were isolated the coumarins (R)-byakangelicin, aurapten, (S)-mexoticin, isosibiricin, isomerazin and coumurrayin and the flavonoid vitexin. All coumarins showed cholinesterase inhibition on TLC tests.

Modificação química e física do amido de quirera de arroz para aproveitamento na indústria de alimentos

The study evaluated the efficiency of chemical (phosphorylation) and physical (extrusion) modifications of the starch of broken rice. Results demonstrated a reduction in the moisture content of extruded and phosphorylated broken rice and an increase in the ash content of phosphorylated broken rice. Both phosphorylation and extrusion increased cold water binding capacity, swelling power, and solubility. Extruded and phosphorylated pastes were stable under refrigeration, but only extruded paste was stable when submitted to freezing. Phosphorylated paste had the lowest viscosity and the highest stability during heating, while the extruded one gelatinized without heating, but had higher losses during heating.

De resíduo a insumo: a construção do caminho para uma química mais limpa através de um projeto de ensino

The discussion among teachers, students, and technicians about the destination of residues from chemistry laboratories led to a research project whose results were incorporated into a course in its daily practices. The treatment of the residues from argentimetric practices allowed us to establish cognitive relations of technological basis and of those related to the rising of the level of awareness about environmental aspects and social responsibility of chemistry professionals. The techniques and the results, from the economic point of view, namely that of value aggregation (metallic silver) and the conversion of the residue into input (potassium chromate solution) are shown.

Caracterização físico-química de complexo de inclusão entre hidroximetilnitrofurazona e hidroxipropil-beta-ciclodextrina

Hydroxymethylnitrofurazone (NFOH) is a prodrug that is active against Trypanosoma cruzi. It however presents low solubility and high toxicity. Hydroxypropyl-beta-cyclodextrin (HP-beta-CD) can be used as a drug-delivery system for NFOH modifying its physico-chemical properties. The aim of this work is to characterize the inclusion complex between NFOH and HP-beta-CD. The rate of NFOH release decreases after complexation and thermodynamic parameters from the solubility isotherm studies revealed that a stable complex is formed (deltaGº= 1.7 kJ/mol). This study focuses on the physico-chemical characterization of a drug-delivery formulation that comes out as a potentially new therapeutic option for Chagas disease treatment.

Comportamento de cristalização de lipídios estruturados por interesterificação química de banha e óleo de soja

The aim of this study was to evaluate the crystallization behavior of binary mixtures of lard and soybean oil in different ratios and their respective structured lipids obtained by chemical interesterification. Crystallization kinetics and polarized light microscopy were used to analyze the mixtures before and after interesterification. The addition of soybean oil changed the lard crystallization, by the effect of the dilution. Crystal diameter increased, while the number of crystals decreased, as a function of temperature. Interesterification resulted in the formation of fewer crystals, with larger diameter in comparison with the original mixtures.

A internet como fonte de informação bibliográfica em química

The internet is an important tool for obtaining information. It offers vast amounts of information ranging from basic to advanced, from general to specific. Nevertheless, its quality cannot be classified or graded. Furthermore, some technical and/or specific information may not be available for free. This work primarily shows the great utility of the internet for getting suitable information in Chemistry and emphasizes open access and quality sites in Chemistry. It directs the reader towards many useful sites within some branches of Chemistry that provide powerful tools of research and study that may not be obtained easily at a library.