Air Pollution Investigation in Vitória Metropolitan Region, ES, Brazil

The application of Mössbauer spectroscopy, X-ray diffractometry, thermogravimetric analysis and PIXE in the characterization of the particulate matter in atmospheric aerosols in Metropolitan Region of Vitória (MRV), Brazil have been investigated. The main sources of particulate matter, natural, industrial and antropogenic from human activities, have been studied to identify its contribution in the atmospheric particles. During the years 1995 to 1999 samples of total suspended particles (TSP, Ø 100 m) were collected from four points within MRV. The inhalable particles (PM₁₀ Ø 10 m) and sedimented particles (SP) were also collected from the same region. A receptor modeling was used for the identification of the source of particulate matter in the collected urban aerosol.     

Determination of Diazepam in Human Plasma by Solid-Phase Microextraction and Capillary Gas Chromatography-Mass Spectrometry

A simple, sensitive, and reproducible solid-phase microextraction and capillary gas chromatography-mass spectrometry (SPME-GC-MS) method for determination of diazepam in human plasma is described. The optimum conditions for the SPME procedure were as following: direct extraction mode with a polydimethylsiloxane (PDMS) fiber (100 μm film thickness), 250 μL of sample plasma matrix modified with a solution containing sodium chloride (10% weight by volume) and 4.25 mL of a phosphate buffer solution (0.1mol L⁻¹, pH 6.9), extraction temperature 55°C under a magnetic stirring rate of 2500 rpm for 30 min, followed by the drug thermal desorption (250°C) in a GC injection port for 10 min. The limit of quantification of diazepam in plasma was 10.0 ng mL⁻¹, with a coefficient of variation lower than 14.0% and linearity from 10.0 to 1000.0 ng mL⁻¹, which allows diazepam analyses from sub to therapeutic levels.     

Studies by NMR of in vitro spontaneous oscillations of activity in enzymatic extracts

NMR has been used to study slow spontaneous oscillations previously observed for the activity of enzymes extracted from plant leaves and maintained under constant conditions. The randomly modulated period of these oscillations has a mean value of several hours. This phenomenon is interpreted in terms of synchronous transition among several conformational states of biomolecules.     

The effect of temperature on the analysis of metanephrine for catechol-O-methyltransferase activity assay by HPLC with electrochemical detection

The enzyme catechol-O-methyltransferase (COMT) plays an important role in the metabolism of catechol estrogens and degradation of the catecholamine neurotransmitters, such as epinephrine. Several analytical methods, mainly high-performance liquid chromatography with electrochemical amperometric detection, have been reported for the analysis of catecholamines and their metabolites in biological fluids. In this paper we report the relevance of controlling temperature in calibration procedures of metanephrine, an O-methylated product of catechol-O-methyltransferase, using epinephrine as substrate. The results at higher temperatures show shorter retention times of metanephrine, no undue band-broadening and increased electro signals. This study also showed that, despite different temperatures leading to similarly specific activities of recombinant human COMT as expected, there are additional advantages in flow analytical methods where good sensitivity, efficiency and selectivity is required, mainly in tissues with low levels of COMT activity.