Determinação direta de crômio em açúcar e leite por espectrometria de absorção atômica com atomização eletrotérmica em forno de grafite

A fast and direct method for the determination of Cr in milk and cane sugar suspensions using graphite furnace atomic absorption spectrometry with Zeeman-effect background correction is described. No sample pre-treatment was necessary, minimizing the risk of contamination. The concentration of chromium in cane sugar was evaluated using Cr reference solutions prepared in 1% v/v HNO3 solution. The milk samples were introduced into the furnace with a mixture of amines for avoiding the autosampler blockage and foaming of milk. Chromium determination in milk was based on the standard additions method (SAM). The limit of detection and characteristic mass for cane sugar sample (30 muL) were 0,13 ng/ml and 4,3 pg, and for milk sample (10 muL) were 0,23 ng/ml and 7,8 pg, respectively. The graphite tube lifetime was 300 firings for sugar-cane sample and 100 firings for milk sample. The heating program was implemented in 68 s.

Estudo termogravimétrico e calorimétrico da algaroba

Humidity and ash content of powder and bran of algaroba pods are important quality parameters for biological control during storage. The studies of humidity and ash content were carried out conventional and thermogravimetric methods. Different values were obtained by the various methods. The thermogravimetric method was faster and required less sample for the humidity and ash analyses of the powder and bran of algaroba pods. The differential scanning calorimetry curves of the powder and bran of algaroba pods, dryed at 55 ºC, showed two peaks, one corresponding to the gelatinization of starch and the other to the vaporization of water. The samples dryed at 65, 75, 85, 95 and 105 ºC showed one peak, corresponding to the vaporization of water.

Redes neurais e suas aplicações em calibração multivariada

Neural Networks are a set of mathematical methods and computer programs designed to simulate the information process and the knowledge acquisition of the human brain. In last years its application in chemistry is increasing significantly, due the special characteristics for model complex systems. The basic principles of two types of neural networks, the multi-layer perceptrons and radial basis functions, are introduced, as well as, a pruning approach to architecture optimization. Two analytical applications based on near infrared spectroscopy are presented, the first one for determination of nitrogen content in wheat leaves using multi-layer perceptrons networks and second one for determination of BRIX in sugar cane juices using radial basis functions networks.

Influência do material do destilador na composição química das aguardentes de cana: parte II

The quantitative chemical analysis of the Brazilian sugar cane spirit distilled from glass column packaged with copper, stainless steel, aluminum sponge, or porcelain balls is described. The main chemical compounds determined by gas chromatography coupled with flame ionization (FID) and flame photometric (FPD) detectors and liquid chromatography coupled with diode array detector are aldehydes, ketones, carboxylic acids, alcohols, esters and dimethylsulfite (DMS). The spirits produced either in columns filled with copper or aluminum pot still exhibits the lowest DMS contents but the higher sulfate and methanol contents, whereas spirits produced in stainless steel or porcelain showed higher DMS concentration and lower teors of sulfate ion and methanol. These observations are coherent with DMS oxidation to sulfate, with methanol as by product, in the presence of either copper or aluminum.

Sucroquímica: síntese e potencialidades de aplicações de alguns derivados químicos de sacarose

The interest on the use of sucrose as raw material increased in the last years. In this work, the synthesis and applications of sucrose derivatives as esters, ethers, and other products are discussed in a concise manner aiming to presenting the sucrochemistry as a promising field in organic chemistry from a rather accessible, low-priced, ecological, and renewable source.

Uso de agrotóxicos em cana-de-açúcar na bacia do Rio Corumbataí e o risco de poluição hídrica

The state of São Paulo is the main Brazilian consumer of pesticides. Sugar cane, which uses a great amount of these products, is extensivelly cultivated in this state, such as in the Corumbataí river basin, an important source of water for the region. In order to implement an efficient and low-cost monitoring program, the temporal characterization of the use of pesticides on sugar cane in this basin was performed. After knowing the seasonal trends of consumption, a better choice of sampling time, became possible. The combination of data from this survey with partitioning indices, average doses and toxicological classifications showed to be important for defining the pesticides to be included in the monitoring program.

Diagnóstico ambiental de metais e organoclorados em córregos adjacentes a áreas de cultivo de cana-de-açúcar (Estado de São Paulo, Brasil)

Sugar cane cultivation in the State of São Paulo has expanded in the last years, with an annual production of 200•10(6) t in an area of 2.5• 10(6) hectares. The use of herbicides, pesticides and fertilizers in sugar cane plantations, together with deforestation of riparian vegetation, have caused impacts on the hydric resources of the adjacent areas. The aim of this work is to evaluate the influence of sugar cane plantations on streams in the central region of the State of São Paulo, studying 16 organochlorinated compounds and 7 metals (Cu, Fe, Cd, Zn, Mn, Cr and Ni) found in the sediments of 11 streams. The results show that there is a higher concentration of metals and organochlorinated compounds in streams without riparian vegetation when compared to forested areas.

Emprego do carvão ativado para remoção de cobre em cachaça

Copper content is of great concern among sugarcane-spirit producers. It is released from copper-made distillers, during the distillation process. Activated carbon has been used to remove copper. However, depending on the amount of carbon and the duration of reaction, it can also remove higher alcohols and esters, which are important in the final product. A sugarcane spirit with 9 mg L-1 of copper was shaken with 2 to 26 g L-1 of activated carbon, during 10 to 1440 minutes. Then, copper and organic compounds were measured. At least 12 g L-1 of carbon and 60 min shaking time were necessary to decrease copper bellow 5 mg L-1. However, other components of the product were also affected.

Determinação dos teores de cobre e grau alcoólico em aguardentes de cana produzidas no estado de Minas Gerais

The objective of this work was to investigate if producers of sugar cane spirits in Minas Gerais, Brazil, have improved the copper content of their products and also if they have adjusted to the new standards of identity for 'cachaça' and 'aguardente'. Seventy-one samples, obtained from May 2003 until March 2004, were analyzed. Mean copper content was 2.30 mg/L, which indicates a significant reduction in levels. The mean alcohol content was 45.6 % v/v. All of the 'aguardente' but only 79% of the 'cachaça' attended to the standard of identity for alcohol content for these products.

Desempenho de biomassas na adsorção de hidrocarbonetos leves em efluentes aquosos

Removal of hydrocarbons from aqueous effluents using biosorbents was investigated. The effluent was simulated by a dispersion of gasoline (simple hydrocarbons) in water. Corn-cob, wood powder, coconut mesocarp and sugar-cane bagasse were used as adsorbents and their performance verified by means of batch experiments performed in an agitated vessel. The influence of input variables such as hydrocarbon concentration, mass of biomass and agitation level on the adsorbents' capacity was studied by means of factorial design. The results indicated that, among the materials studied, coconut mesocarp and sugar-cane bagasse can be considered promising biomasses for treating aqueous effluents contaminated by hydrocarbons.

Teores de carbamato de etila e outros componentes secundários em diferentes cachaças produzidas em três regiões do estado de Minas Gerais: Zona da mata, sul de minas e vale do jequitinhonha

Minas Gerais is the highest producer of handmade spirits. Research has been carried out aiming to contribute to progress. Thus, the goal of this work is to evaluate the quality of spirits in three different regions of Minas Gerais state. We analyzed ethyl carbamate, alcoholic grade, volatile acidity, higher alcohols, aldehyde, esters, methanol, furfural and copper. The values obtained for ethyl carbamate varied from undetectable to 643.5 µg L-1, with only one region not following the legislation (150 µg L-1). Most of the compounds in the spirits were present within the limits estabilished by the legislation.

Aplicação da metodologia de planejamento fatorial e análise de superfícies de resposta para otimização da fermentação alcoólica

In the present work, the influence of the amount of nitrogen and phosphorus and degrees Brix on the yield and productivity of alcoholic fermentation has been evaluated. The methodology used was factorial design and response surface analysis. Within the range studied only for phosphorus a statistically significant effect was observed. The broth of sugar cane of the CB 453 variety already possessed enough nitrogen for the fermentation. The mathematical and empirical model was validated for productivity and not for yield. The concentration of alcohol produced in the fermentation was not enough to cause cellular growth inhibition.

Determinação de carbamato de etila em aguardentes de cana por CG-EM

A simple, specific and sensitive GC-MS procedure with ion m/z 62 was validated for the determination of ethyl carbamate (EC) in spirits. It exhibited linearity over the concentration of 30 to 600 μg/L with 30 μg/L limit of quantification. EC was detected in 70 of the 71 samples analyzed with levels from 33 to 2609 μg/L (mean level = 893 μg/L). 35% of the samples contained 500 to 1000 μg/L and 23% contained 150 to 500 and 1000 to 1500 μg/L. No significant correlation was found between EC and the levels of copper, pH and alcohol content of the samples.

Caracterização de cinza do bagaço de cana-de-açúcar para emprego como pozolana em materiais cimentícios

This work presents the results of morphological and physical-chemical characteristics of a sugar cane bagasse ash material sample produced under controlled burning conditions. The investigation was carried out by analyzing chemical composition, X-ray diffraction, 29Si nuclear magnetic resonance, morphology, thermal analysis, particle size, specific surface, and density. Moreover, the pozzolanic activity of the ash was evaluated by pozzolanic activity index and Chapelle's method. The results suggest that the sugar cane bagasse ash has adequate properties to be used as pozzolan in construction materials.

Teores de carbamato de etila em aguardentes de cana e mandioca: parte II

Herein, we report the concentration of ethyl carbamate (EC) and copper in 380 samples of sugar-cane spirit and 45 samples of manioc spirit as determined by GC-MS and FAAS respectively. The cyanide content determined spectrophotometrically is reported for the manioc spirit. Sugar cane spirit produced by alembic distillation (70,0 µg L-1) shown a lower content of EC than samples produced by column distillation (270 µg L-1). No simple correlation between the content of EC and copper for sugar cane spirit as well among the concentration of EC, copper, and cyanide for manioc spirit could be observed.