Use of sugar cane bagasse as solid phase extractor for cadmium determination by FAAS

The present paper describes the use of sugar cane bagasse as solid phase extractor for cadmium determination after complexation of the analyte with ammonium diethyldithiophosphate (ADDP) and sorption of the Cd-DDP complexes on the solid support. The concomitants were separated using a flow injection analysis (FIA) system coupled to flame atomic absorption spectrometry (FAAS) for determination. The main parameters such as ADDP concentration, acid medium, flow rate, reaction coil length, and reaction time were investigated.The results obtained with HNO3 showed good accuracy and precision. The enhancement factor was 20.5 times for a 120-second preconcentration time, and the analytical frequency was 25 determinations per hour. The calibration curve was linear over the concentration range of 1-40 mu g L-1 Cd with a LOD of 0.697 mu g L-1 Cd and a relative standard deviation of 0.96% after 12 successive measurements of 30 mu g L-1 Cd.The proposed method was evaluated for the FIA-FAAS analysis of certified reference materials (tomato leaves, spinach leaves, and bovine liver) and Cd-spiked foods (shrimp, sardine, tuna, chicken liver and bovine liver). Good recoveries (80.0-97.1%) for the Cd-spiked samples and certified reference materials were obtained. The results of bagasse-packed minicolumns were compared with Si-C,8 packed minicolumns. The F-test was applied between Si-C-18/Bagasse minicolumns, Si-C-18/certified values, and bagasse/certified values. It was found that the results were in agreement with the certified values at a 95% confidence level.

Direct determination of arsenic in sugar by GFAAS with transversely heated graphite atomizer and longitudinal Zeeman-effect background correction

A method has been developed for the direct determination of As in sugar by graphite furnace atomic absorption spectrometry with a transversely heated graphite atomizer (end-capped THGA) and longitudinal Zeeman-effect background correction. The thermal behavior of As during the pyrolysis and atomization steps was investigated in sugar solutions containing 0.2% (v/v) HNO3 using Pd, Ni, and a mixture of Pd + Mg as the chemical modifiers. For a 60-muL sugar solution, an aliquot of 8% (m/v) in 0.2% (v/v)HNO3 was dispensed into a pre-heated graphite tube at 70 degreesC. Linear analytical curves were obtained in the 0.25 - 1.50-mug L-1 As range. Using 5 mug Pd and a first pyrolysis step at 600 degreesC assisted by air during 40 s, the formation of a large amount of carbonaceous residue inside the atomizer was avoided. The characteristic mass was calculated as 24 pg As and the lifetime of the graphite tube was around 280 firings. The limit of detection (L.O.D.) based on integrated absorbance was 0.08 mug L-1 (4.8 pg As) and the typical relative standard deviation (n = 12) was 7% for a sugar solution containing 0.5 mug L-1. Recoveries of As added to sugar samples varied from 86 to 98%. The accuracy was checked in the direct analysis of eight sugar samples. A paired t-test showed that the results were in agreement at the 95% confidence level with those obtained for acid-digested sugar samples by GFAAS.

Influence of drying conditions on ascorbic acid during convective drying of whole persimmons

Degradation kinetics of food constituents may be related to the matrix molecular mobility by glass transition temperature. Our objective was to test this approach to describe ascorbic acid degradation during drying of persimmons in an automatically controlled tray dryer with temperatures (40 to 70 degrees C) and air velocities (0.8 to 2.0 m/s) varying according a second order central composite design. The Williams-Landel-Ferry model was satisfactorily adjusted to degradation curves for both control strategies adopted-constant air temperature and temperature fixed inside the fruit. Degradation rates were higher at higher drying temperatures, independent of the necessary time to attain the desired moisture content.

Identification of polycyclic aromatic hydrocarbons in sugar cane soot by gas chromatography mass spectrometry

Fly soot samples collected in the sugar cane fields after the process of burning were extracted in a Soxhlet apparatus (methylene chloride:methanol 4:1). The extracts were fractionated on silica gel Sep-Pak cartridges into three fractions. A gas chromatographic-mass spectrometric study of the fly soot extracts allowed the identification of the PAH with mutagenic and carcinogenic properties. Large amounts of aliphatic hydrocarbons, fatty acid esters and some PAHs were identified by GCMS in full scan mode. GC-MS in the selective ion monitoring mode (SIM) was suitable for the determination of many PAHs, which are often present in the burnt biomass. 31 PAHs and 7 thiophens derivatives were identified. The presence of these compounds should be regarded as a caution to workers and the general population to avoid exposure to the fly soot.

Isolation of a new L-amino acid oxidase from Crotalus durissus cascavella venom

A novel L-amino acid oxidase (LAO) (Casca LAO) from Crotalus durissus cascavella venom was purified to a high degree of molecular homogeneity using a combination of molecular exclusion and ion-exchange chromatography system. The purified monomer of LAO presented a molecular mass of 68 kDa and pI estimated in 5.43, which were determined by two-dimensional electrophoresis. The 71st N-terminal amino acid sequence of the LAO from Crotalus durissus cascavella presented a high amino acid sequence similarities with other LAOs from Colloselasma rhosostoma, Crotalus adamanteus, Agkistrodon h. blomhoffi, Agkistrodon h. halys and Trimeresurus stejnegeri. LAO displayed a Michaelis-Menten behavior with a kilometer of 46.7 mu M and an optimum pH for enzymatic activity of 6.5. Casca LAO induced a dose-dependent platelet aggregation, which was abolished by catalase and inhibited by indomethacin and aspirin. These results suggest that the production of H2O2 is involved in subsequent activation of inflammatory enzymes, such as thromboxane. Casca LAO also inhibited the bacterial Growth of Gram-negative (Xanthomonas axonopodis pv passiflorae) and Gram-positive (S. mutans) strains. Electron microscopy assessments of both bacterial strains suggest that the hydrogen peroxide produced by LAO induce bacterial membrane rupture and consequently loss of cytoplasmatic content. This LAO exhibited a high antileishmanic activity against the promastigote of Leishmania amazonensis in vitro, its activity was dependent on the production of hydrogen peroxide, and the 50% inhibitory concentration was estimated in 2.39 mu g/ml. (C) 2005 Elsevier Ltd. All rights reserved.

Synergism among lactic acid, sulfite, pH and ethanol in alcoholic fermentation of Saccharomyces cerevisiae (PE-2 and M-26)

The industrial production of ethanol is affected mainly by contamination by lactic acid bacteria besides others factors that act synergistically like increased sulfite content, extremely low pH, high acidity, high alcoholic content, high temperature and osmotic pressure. In this research two strains of Saccharomyces cerevisiae PE-2 and M-26 were tested regarding the alcoholic fermentation potential in highly stressed conditions. These strains were subjected to values up to 200 mg NaHSO3 l(-1), 6 g lactic acid l(-1), 9.5% (w/v) ethanol and pH 3.6 during fermentative processes. The low pH (3.6) was the major stressing factor on yeasts during the fermentation. The M-26 strain produced higher acidity than the other, with higher production of succinic acid, an important inhibitor of lactic bacteria. Both strains of yeasts showed similar performance during the fermentation, with no significant difference in cell viability.

Yield and quality of carrot seeds, cv. Brasilia, as a result of plant population, gibberellic acid and stage of maturity

'Brasilia' is a cultivar of carrot with characteristics suiting cultivation under hot conditions but with problems in seed production, arising from the conflicting requirements of root and seed production. One solution is to select cultivars requiring vernalisation and then to use GA(3) to induce flowering where the climate prevents this. There is, however, little information on plant population, seed maturity and harvesting time on which to base such a procedure. Accordingly this research was carried out to study the physiological quality and production of the seeds in plant populations from 25,000 to 800,000 plants/ha, in the seed-to-seed method of cv. Brasilia in Anapolis, GO, Brazil. In each population, two harvest methods (from first and second orders of umbels, or selected harvest, and remaining orders, or total harvest) and two stages of maturity (brownish, or mature seeds, and yellowish, or immature ones) were also evaluated. Two trials were carried out, with and without gibberellic acid. Seed was evaluated for physical characters, germination, vigour, 1000-seed weight, water content, dry matter and productivity. Seed was produced in both experiments (with or without GA3 spraying). Mature seed showed germination at least 30% greater than immature, and seed from the selected harvest showed germination 16% greater than from the total harvest. In increasing plant population to 200,000 plants/ha, seed quality was not affected, but productivity increased.