Polycyclic aromatic hydrocarbons in Brazilian vegetables and fruits

Polycyclic aromatic hydrocarbons (PAHs) occur as contaminants in different types of food predominantly from environmental pollution, food packaging and food processing and the levels found depend on the source of the contamination. PAHs emissions from automobile traffic and industry activities were shown to influence the PAHs levels and profiles in vegetables and fruits grown nearby. The present study was carried out to determine the levels of PAHs in samples of lettuce, tomato, cabbage, apple, grape and pear, and use these data to further estimate the dietary exposure of Brazilians to PAHs. Samples of each fruit and vegetable were collected in six different places and analysed for ten PAHs. The analytical method involved saponification with methanolic KOH, liquid-liquid extraction with cyclohexane, clean-up on silica gel column and determination by high performance liquid chromatography using fluorescence detection. The mean levels of total PAHs were 13.53 mug/kg in lettuce, 9.50 mug/kg in tomato, 8.86 mug/kg in cabbage, 4.05 mug/kg in apple, 3.77 mug/kg in grape and 3.87 mug/kg in pear. Of the carcinogenic PAHs, benzo(a)anthracene was the most representative, being found in 89% of all samples analysed. Chrysene was not detected in any sample. (C) 2002 Elsevier Science Ltd. All rights reserved.141495

HPLC determination of caffeine in tea, chocolate products and carbonated beverages

Different brands of mate and black tea, chocolate products and carbonated beverages available on the Brazilian market were analysed for caffeine by high-performance Liquid chromatography with a UV-vis detector at 254 nm. The column was a reverse phase C18 and the mobile phase consisted of methanol-water (30:70, v/v), acetonitrile-water (10:90, v/v) and methanol-water (25:75, v/v) for tea, chocolate products and soft drinks respectively. Caffeine content ranged from 1.05 to 15.83 mg per cup in mate tea, from 32.21 to 36.23 mg per cup in black tea, from 0.14 to 0.95 mg g(-1) in chocolate products from 2.73 to 7.49 mg per can in guarana-type soft drinks and from 19.81 to 45.89 mg per can in cola soft drinks. These data indicate that the levels of caffeine in Brazilian teas, chocolates and soft drinks are within the ranges reported for similar products in other countries. (C) 1999 Society of Chemical Industry.79131861186

Self-consistent equilibrium calculation through a direct variational technique in tokamak plasmas

A self-consistent equilibrium calculation, valid for arbitrary aspect ratio tokamaks, is obtained through a direct variational technique that reduces the equilibrium solution, in general obtained from the 2D Grad-Shafranov equation, to a 1D problem in the radial flux coordinate rho. The plasma current profile is supposed to have contributions of the diamagnetic, Pfirsch-Schluter and the neoclassical ohmic and bootstrap currents. An iterative procedure is introduced into our code until the flux surface averaged toroidal current density (J(T)), converges to within a specified tolerance for a given pressure profile and prescribed boundary conditions. The convergence criterion is applied between the (J(T)) profile used to calculate the equilibrium through the variational procedure and the one that results from the equilibrium and given by the sum of all current components. The ohmic contribution is calculated from the neoclassical conductivity and from the self-consistently determined loop voltage in order to give the prescribed value of the total plasma current. The bootstrap current is estimated through the full matrix Hirshman-Sigmar model with the viscosity coefficients as proposed by Shaing, which are valid in all plasma collisionality regimes and arbitrary aspect ratios. The results of the self-consistent calculation are presented for the low aspect ratio tokamak Experimento Tokamak Esferico. A comparison among different models for the bootstrap current estimate is also performed and their possible Limitations to the self-consistent calculation is analysed

Contribution of guarana powder (Paullinia cupana) as a source of caffeine in the diet

Objective The present study was conducted in order to determine the caffeine levels in different brands of commercially available guarana powder. Methods The analytical methodology involved extraction with water clean-up with saturated basic lead acetate solution and determination by high performance liquid chromatography with diode array detector (200-400nm). 39 samples were purchased in the cities of Campinas and Ribeir (a) over tildeo Preto, SP between December 2003 and January 2004 and analyzed. Results The caffeine levels in the samples varied widely ranging from 9.52 to 36.71mg/g, probably due to differences in the origin of the raw material and to the types of processing that the guarana seeds are submitted to. In comparison to coffee, traditional source of caffeine in the diet, it is possible to verify that the average caffeine content in guarana powder is about four times higher than the quantities present in coffee. Conclusion Among guarana powder consumers, this product may be considered as an important source of caffeine in the diet. The association with other products containing caffeine suggests that the guarana powder consumption should be controlled as the debate regarding caffeine's safe dose of intake remains.201636