Comparison of USEPA 3050B and ISO 14869-1: 2001 digestion methods for sediment analysis by using FAAS and ICP-OES quantification techniques

A study of the partial USEPA 3050B and total ISO 14869-1:2001 digestion methods of sediments was performed. USEPA 3050B was recommended as the simpler method with less operational risk. However, the extraction ability of the method should be taken in account for the best environmental interpretation of the results. FAAS was used to quantify metal concentrations in sediment solutions. The alternative use of ICP-OES quantification should be conditioned by a previous detailed investigation and eventual correction of the matrix effect. For the first time, the EID method was employed for the detection and correction of the matrix effect in sediment ICP-OES analysis. Finally, some considerations were made about the level of metal contamination in the area under study.

Esterificação de ácidos graxos utilizando zircônia sulfatada e compósitos carvão ativado/zircônia sulfatada como catalisadores

In this work sulfated zirconia (SZr) and activated carbon/SZr composites produced by impregnation method with or without heating treatment step (CABC/SZr-I and CABC/SZr-I SC) and by the method of synthesis of SZr on the carbon (CABC/SZr-S) was used as catalysts in the esterification reactions of fatty acids. The SZr presented very active, conversions higher than 90% were obtained after 2 h of reaction. The activity of the composite CABC/SZr-I20%SC was up to 92%, however, this was directly related to time and temperature reactions. CABC/SZr-I and CABC/SZr-S were less active in esterification reactions, what could be attributed to its low acidity

Produção e caracterização de espumas cerâmicas obtidas a partir de lodo de anodização de alumínio

Ceramic foams were produced from a sludge generated in the aluminum anodizing process by using an industrial polyurethane foam (replication method) with open cell sizes of 10 ± 5 ppi (porosity = 97%) which were impregnated with suspensions containing 50-61 wt.% alumina, 1 wt.% citric acid, 6 wt.% bentonite and fired at 1600 ºC for 2 h. The aluminum anodizing sludge shows a high alumina content (87.5 wt.%) and a low particle size (~1.7 mm) after calcination and milling. The obtained filters show porosity of approximately 70%, filtration capability (mass water flow) of 1.7 kg/s and mechanical strength under compression of 2.40 MPa.

The contributions of Henri Victor Regnault in the context of organic chemistry of the first half of the nineteenth century

A very little known aspect of the scientific career of Regnault is his contribution to the emerging organic chemistry in the first half of the nineteenth century. The purpose of this article is not only to describe two of his most important researches in this field, as were the discovery of two series of halogenated derivates of certain organic compounds and the precise identification of some of the then recently discovered alkaloids, but also the main features that identified his research method. With the involvement in these subjects, Regnault unintentionally positioned himself in the midst of some of the polemics about the classification of organic compounds that characterized this age of science.

Constituintes químicos e avaliação da atividade antibacteriana de Macroptilium lathyroides (L.) Urb. (Fabaceae)

The chemical investigation of the stems and branches of Macroptilium lathyroides led to the isolation of a mixture of β-sitosterol and stigmasterol. The extracts from the roots allowed the isolation of lasiodiplodin, a mixture of stigmast-4-en-6β-ol-3-one and stigmast-4,22-dien-6β-ol-3-one, de-O-methyllasiodiplodin, genistein and lupinalbin A. The structures of the isolated compounds were assigned on the basis of their NMR data, including comparison of their spectral data with values described in the literature. The antibacterial activity of crude extracts from stems, branches and roots was evaluated. This is the first report involving the chemical investigation of this species.

Desenvolvimento do método de extração sólido-líquido com partição em baixa temperatura para determinação de inseticidas em grãos de milho ozonizados

The objective of this study was to optimize and validate a solid-liquid extraction method with low-temperature partitioning (SLE/LTP) for the analysis of pesticides. This method was coupled with gas chromatography (GC/ECD) and used to evaluate the degradation of bifenthrin and pirimiphos-methyl in maize grains on exposure to ozone. The optimized SLE/LTP-GC/ECD method is simple, effective and consumes low quantities of the solvent. It can be routinely used for the determination of bifenthrin and pirimiphos-methyl in maize samples. The use of this method of analysis determined that the levels of the insecticides in maize grains were reduced on exposure of the grains to the ozone gas. The observed reduction in the levels of insecticide was directly proportional to the increase in the concentration of the ozone gas.

Otimização e validação da extração sólido-líquido e purificação em baixa temperatura de HPAs em lodo de esgoto

In this study, a method of solid-liquid extraction and purification at low temperature (SLE-PLT) to determine 16 polycyclic aromatic hydrocarbons (PAHs) in sewage sludge was optimized and validated. The analyses were performed by HPLC-UV. The extraction phase, homogenization procedure, influence of pH, ionic strength and clean-up of the extracts were optimized. Recoveries were higher than 63.4% for 11 PAHs. The correlation coefficients were greater than 0.99 and limits of detection and quantitation were less than 0.060 and 0.15 µg g-1, respectively. These values were lower than the maximum residue limits of PAHs established by European legislation. SLE-PLT proved a more practical, economical method with fewer steps compared to Soxhlet extraction (reference method) for PAHs in sewage sludge.

MONITORAMENTO DE RESÍDUOS DE AGROTÓXICOS DA CLASSE DOS ORGANOFOSFORADOS POR CGDFC EM AMOSTRAS DE LEITE FLUÍDO E EM PÓ

Samples of whole fluid pasteurized, UHT and powdered milk were analyzed for the presence of organophosphorus pesticide residues (OPR) using the QuEChERS method with detection by GC-FPD and confirmation by UPLC-MS/MS. A total of 23% of fluid milk samples and 27% of powdered milk samples contained at least one organophosphorus residue. The OPR found in the samples showed these can reach the milk and remain even after pasteurization, sterilization and drying processes. Some domestic sanitary residues were also present in the powdered milk samples. These residues have no LMR in Brazilian food legislation and are therefore not taken into account in food intake evaluations. There was an unidentified chromatographic peak in 30% of all the liquid and powdered milk samples, indicating the presence of some other contaminant.

Covalent anion of Li(HF)3- system: an ab initio study

In this paper, we report the stability of the Li(HF)3- molecular anion calculated at the MP2/6-31++G** and CCSD(T)/6-31++G** level of theory. Five possible conformers of Li(HF)3- molecular anions have been determined employing ab initio MP2 method with 6-31++G** basis set. The most stable conformer of five Li(HF)3- anions is in a cyclic ring structure Li(HF)3-(1). From our calculations we show that the molecule is stable towards electron attachment, with an electron adiabatic electron affinity (AEA) of 199.5 meV (233.1 meV with zero point energy correction) and 471.3 meV at the MP2 and CCSD(T) levels, respectively. In addition we present vertical detachment energies of 230.2 meV and 795.8 meV at the MP2, CCSD(T), respectively. The importance of the latter has to do with the ability of experimental detection of this value.

Flow-batch analyser for preparation of calibration standard mixtures in simultaneous multicomponent spectrometric analysis

The application of multivariate calibration techniques to multicomponent analysis by UV-VIS molecular absorption spectrometry is a powerful tool for simultaneous determination of several chemical species. However, when this methodology is accomplished manually, it is slow and laborious, consumes high amounts of reagents and samples, is susceptible to contaminations and presents a high operational cost. To overcome these drawbacks, a flow-batch analyser is proposed in this work. This analyser was developed for automatic preparation of standard calibration and test (or validation) mixtures. It was applied to the simultaneous determination of Cu2+, Mn2+ and Zn2+ in polyvitaminic and polymineral pharmaceutical formulations, using 4-(2-piridilazo) resorcinol as reagent and a UV-VIS spectrophotometer with a photodiode array detector. The results obtained with the proposed system are in good agreement with those obtained by flame atomic absorption spectrometry, which was employed as reference method. With the proposed analyser, the preparation of calibration and test mixtures can be accomplished about four hours, while the manual procedure requires at least two days. Moreover, it consumes smaller amounts of reagents and samples than the manual procedure. After the preparation of calibration and test mixtures, 60 samples h-1 can be carried out with the proposed flow-batch analyser.

Synthesis and characterization of Fe(III)-doped ceramic membranes of titanium dioxide and its application in photoelectrocatalysis of a textile dye

Pure and Fe(III)-doped TiO2 suspensions were prepared by the sol gel method with the use of titanium isopropoxide (Ti(OPri)4) as precursor material. The properties of doped materials were compared to TiO2 properties based on the characterization by thermal analysis (TG-DTA and DSC), X-ray powder diffractometry and spectroscopy measurements (FTIR). Both undoped and doped TiO2 suspensions were used to coat metallic substrate as a mean to make thin-film electrodes. Thermal treatment of the precursors at 400ºC for 2 h in air resulted in the formation of nanocrystalline anatase TiO2. The thin-film electrodes were tested with respect to their photocatalytic performance for degradation of a textile dye in aqueous solution. The plain TiO2 remains as the best catalyst at the conditions used in this report.

Net melon resistance to Didymella bryoniae according to grafting and potassium levels

Chemical control of the fungus Didymella bryoniae, the causal agent of the disease gummy stem blight in melon, is frequently inefficient; thus, alternatives such as grafting and nutrition must be studied. Rootstocks and potassium levels were tested aimed at controlling this disease in net melon under protected environment. The melon hybrid 'Bônus II', ungrafted and grafted onto 'Dinero' melon and 'Strong Tosa' pumpkin rootstocks, was cultivated and inoculated by using the toothpick insertion method with 7-mm mycelial disks from the isolate D. bryoniae Dbr 37; for control, only toothpick insertion was used. The plants were subjected to the following potassium levels: 0, 62.5, 125, 187.5, 250 mg L-1. Grafted 'Bônus II' melon plants were resistant to the fungus, whereas ungrafted ones were susceptible. The adopted potassium levels did not influence the stem lesion size or the survival of plants.

Development of capacitive sensor for measuring soil water content

The irrigation management based on the monitoring of the soil water content allows for the minimization of the amount of water applied, making its use more efficient. Taking into account these aspects, in this work, a sensor for measuring the soil water content was developed to allow real time automation of irrigation systems. This way, problems affecting crop yielding such as irregularities in the time to turn on or turn off the pump, and excess or deficit of water can be solved. To develop the sensors were used stainless steel rods, resin, and insulating varnish. The sensors measuring circuit was based on a microcontroller, which gives its output signal in the digital format. The sensors were calibrated using soil of the type “Quartzarenic Neosoil”. A third order polynomial model was fitted to the experimental data between the values of water content corresponding to the field capacity and the wilting point to correlate the soil water content obtained by the oven standard method with those measured by the electronic circuit, with a coefficient of determination of 93.17%, and an accuracy in the measures of ±0.010 kg kg-1. Based on the results, it was concluded that the sensor and its implemented measuring circuit can be used in the automation process of irrigation systems.

Mapping of summer crops in the State of Paraná, Brazil, through the 10-day spot vegetation NDVI composites

The search for low subjectivity area estimates has increased the use of remote sensing for agricultural monitoring and crop yield prediction, leading to more flexibility in data acquisition and lower costs comparing to traditional methods such as census and surveys. Low spatial resolution satellite images with higher frequency in image acquisition have shown to be adequate for cropland mapping and monitoring in large areas. The main goal of this study was to map the Summer crops in the State of Paraná, Brazil, using 10-day composition of NDVI SPOT Vegetation data for 2005/2006, 2006/2007 and 2007/2008 cropping seasons. For this, a supervised digital classification method with Parallelepiped algorithm in multitemporal RGB image composites was used, in order to generate masks of Summer cultures for each 10-day composition. Accuracy assessment was performed using Kappa index, overall accuracy and Willmott's concordance index, resulting in good levels of accuracy. This methodology allowed the accomplishment, with free and low resolution data, of the mapping of Summer cultures at State level.

Evaluation of empirical methods to estimate reference evapotranspiration in Uberaba, State of Minas Gerais, Brazil

Evapotranspiration is the process of water loss of vegetated soil due to evaporation and transpiration, and it may be estimated by various empirical methods. This study had the objective to carry out the evaluation of the performance of the following methods: Blaney-Criddle, Jensen-Haise, Linacre, Solar Radiation, Hargreaves-Samani, Makkink, Thornthwaite, Camargo, Priestley-Taylor and Original Penman in the estimation of the potential evapotranspiration when compared to the Penman-Monteith standard method (FAO56) to the climatic conditions of Uberaba, state of Minas Gerais, Brazil. A set of 21 years monthly data (1990 to 2010) was used, working with the climatic elements: temperature, relative humidity, wind speed and insolation. The empirical methods to estimate reference evapotranspiration were compared with the standard method using linear regression, simple statistical analysis, Willmott agreement index (d) and performance index (c). The methods Makkink and Camargo showed the best performance, with "c" values ​​of 0.75 and 0.66, respectively. The Hargreaves-Samani method presented a better linear relation with the standard method, with a correlation coefficient (r) of 0.88.