Fluidos supercríticos em química analítica. III.: aplicações

The first two papers in this series described the basic theory involved in supercritical fluid chromatography (SFC), how the technique evolved from gas and liquid chromatography and how the instrumentation was developed. Over the last two years, a commercial, dedicated packed-column SFC/MS instrument appeared on the market. The SFC continues to grow in use, with fundamental developments, coupled with a steady rise in the number of industrial users and applications.

Monitoramento atmosférico passivo de SO2, NO2 e O3 em áreas urbanas e de influência industrial como prática de química ambiental para alunos de graduação

This study is a result of undergraduate student participation in the Environmental Chemistry discipline provided by the Chemistry Institute/UFBA. The students were involved in the development of passive samplers, a project of the LAQUAM (Environmental Analytical Chemistry Laboratory). The students' residences and other neighborhoods were used to create a passive sampling network, allowing the measurement of atmospheric levels of pollutants in urban areas and in those under industrial influence. The assembly of the passive samplers, including impregnation of filters and chemical analysis were part of the students' practice tasks. The results were analyzed taking into consideration the Brazilian legislation.

A criação do curso de engenharia química na escola nacional de química da universidade do Brasil

The goal of this work was to establish the origins of the chemical engineering course at the National School of Chemistry of the University of Brazil (at present, the School of Chemistry of the Federal University of Rio de Janeiro). There was a previous Industrial Chemistry course at the Higher School of Agriculture and Veterinary, established in 1920, following the French model. This course was the basis of the creation of the National School of Chemistry in 1933. During the 1940s, teachers and students claimed for a new course in true connection with the needs of the country and to reach full valorization of their job. The structure of the new Chemical Engineering course was approved in 1946 and the first class begun in 1952. This course was of great importance during the Brazilian industrial development during the 1950s and 1960s.

Efeito do processo de descafeinação com diclorometano sobre a composição química dos cafés arábica e robusta antes e após a torração

The decaffeinated coffee market has been expanding increasingly in the last years. During decaffeination, aroma precursors and bioactive compounds may be extracted. In the present study we evaluate the changes in the chemical composition of C. arabica and C. canephora produced by decaffeination using dichloromethane. A significant change in the chemical composition of both C. arabica and C. canephora species was observed, with differences between species and degrees of roasting. Major changes were observed in sucrose, protein and trigonelline contents after decaffeination. Changes in the levels of total chlorogenic acids and in their isomers distribution were also observed. Lipids and total carbohydrates were not affected as much. The sensory and biological implications of these changes need to be investigated.

Aplicações de nanoeletrodos como sensores na Química Analítica

Nanomaterials make up an emerging area in Chemistry and in the science of materials. This area constitutes the development of methods for synthesizing nanoscopic particles of a given material used for scientific investigation. Nanomaterials have a wide range of commercial possibilities and technological applications, including their use in analytical chemistry, as well as in electronics, optics, engineering, medicine, devices for liberation of drugs, bioencapsulation, among others. This paper presents a summary about nanoelectrodes, devices built from nanoparticles, which show great potential as electrochemical tools in many different types of analysis. The purpose of this paper is to review the construction methodologies of nanoelectrodes, and to point out their successful applicability in the various fields of immune assays and other analytical procedures with quantitative purposes.

Química Analítica de Processos

Process Analytical Chemistry (PAC) is an important and growing area in analytical chemistry, that has received little attention in academic centers devoted to the gathering of knowledge and to optimization of chemical processes. PAC is an area devoted to optimization and knowledge acquisition of chemical processes, to reducing costs and wastes and to making an important contribution to sustainable development. The main aim of this review is to present to the Brazilian community the development and state of the art of PAC, discussing concepts, analytical techniques currently employed in the industry and some applications.

Uso de artigos científicos em uma disciplina de Físico-Química

This paper describes the use of primary chemistry literature in a fifth-semester physical chemistry course for undergraduate chemistry students. The main goal is to expose students to the primary literature of physical chemistry, demonstrating how they can benefit from using it. The assignment addresses issues in chemical education such as scientific writing, relating lecture material to the real world, and conducting literature searches. The student evaluation of this assignment, consisting of two surveys and one focus group, showed its usefulness. The details of the evaluation instruments and their results are provided. Out of 45 students enrolled in the course, 30 (67%) students completed the assignment.

Caracterização química de extratos de Ocimum basilicum L. obtidos através de extração com CO2 a altas pressões

This work reports extraction yield and chemical characterization of the extracts obtained by high-pressure CO2 extraction of a cultivar of Ocimum basilicum L. The experiments were performed in the temperature range of 20 to 50 °C, from 100 to 250 atm of pressure. Chemical analyses were carried out by gas chromatography coupled to mass spectrometry, permitting to identify 23 compounds that were grouped into five chemical classes. Results showed that temperature and solvent density influenced positively the extraction yield. At 20 °C and 0.41 g cm-3 occurred a rise in the concentration of monoterpenes, oxygenated monoterpenes, sesquiterpenes and oxygenated sesquiterpenes.

Variação química do óleo essencial de Hyptis suaveolens (L.) Poit., sob condições de cultivo

This study was performed to establish the correlation between the growth conditions and essential oil composition of Hyptis suaveolens from Alfenas (MG), Brazil. The plants were grown in a greenhouse, four treatments were used and they were harvested at two different periods of time (60 and 135-day-old plants). The essential oil composition was determined by GC-MS analysis. The terpenes spathulenol, globulol, dehydroabietol, a-cadinol and beta-phellandrene were the major constituents found in the essential oil. Oxygenated sesquiterpenes represented the main group of constituents in most of the treatments. The major changes in the essential oil composition were found in 135-day-old plants grown under NPK deficiency. We also identified three groups of volatile components that have not been previously described in H suaveolens.

Influência da temperatura do ar de secagem sobre o teor e a composição química do óleo essencial de Lippia alba (Mill) N. E. Brown

Leaves of Lippia alba were submitted to six different drying treatments, using air at ambient temperature and heated up to 80 °C. The essential oil was extracted by steam distillation and analyzed by GC-MS. For the dried leaves, the oil content was reduced by 12 to 17% when compared with the fresh plant (0.66%). The major oil component was citral, representing 76% for the fresh plant, and varying from 82 to 84% for the dried material. These results showed that L. alba can be submitted to a drying process of up to 80 ºC without degradation and/or loss of the major, [LC1] active component.

Uma proposta para o ensino da Química Analítica Qualitativa

In recent years, because of the need for a more flexible curriculum established by the Curriculum Guidelines of the National Brazilian Education (law 9394/96), the pedagogical project of the Chemistry course of FFCLRP/USP has undergone alterations, amongst them the gradual reduction of the hours devoted to the discipline Qualitative Analytical Chemistry. In this context, this discipline has been carefully analyzed and reorganized in order to allow the elimination of redundancies and the introduction of activities considered important for the professional formation of both chemists and chemistry teachers. In this work, we will discuss the main strategies adopted in this reorganization with the objective of making the teaching/learning process more dynamic and efficient.

A formação do pós-graduando em química para a docência em nível superior

The article presents a brief analysis on chemistry post-graduate students' perception on teaching in higher education. This study was done based on the context of students' formation in chemistry post-graduate programs and makes suggestions on how to improve the formation process of post-graduate students in order to decrease the rupture between teaching and research in chemistry post-graduate programs.

Cromatografando em coluna com resina de almécega: um projeto para química orgânica experimental

The use of natural products to demonstrate the silica gel column chromatography technique is proposed in the present article. It describes the separation of the triterpenes alpha- and beta-amirin from the diol breine and maniladiol, obtained from almécega resin (Protium heptaphyllum March.). The experiment uses an accessible material, was accomplished in 4 h, and can be applied with success an the experimental course of organic chemistry for undergraduate students.

Experimentação em química de compostos organometálicos: preparação do cloreto de dicarbonilciclopentadienilferro(II)

In this work, we describe a new method for obtaining [Fe(CO)2[(eta5-C5H5)Cl] employing simple techniques and low-cost reagents. It is worth mentioning that this method is faster than others reported in the literature. It was applied in laboratory classes for undergraduate students, exploring different concepts in organometallic chemistry and discussing the steps involved in the synthetic route.