Interfase y software de control para operar en sincronismo un automuestreador y un atomizador electrotérmico por filamento de tungsteno en espectrofotometría de absorción atómica

The interface and software for synchronous control of an autosampler and an electrothermal tungsten coil atomizer in atomic absorption spectrophotometry were developed. The control of the power supply, the trigger of the Read function of the spectrophotometer and the automatic operation of the autosampler was performed by software written in "TurboBasic". The system was evaluated by comparison of the repeatability of peak-height absorbances obtained in the atomization of lead by consecutive 10-µl injections of solutions (prepared in 0.2% v/v HNO3) using autosampler and manual sample introduction, and also by long term operation.

Estimating extreme value cumulative distribution functions using bias-corrected kernel approaches

We propose a new kernel estimation of the cumulative distribution function based on transformation and on bias reducing techniques. We derive the optimal bandwidth that minimises the asymptotic integrated mean squared error. The simulation results show that our proposed kernel estimation improves alternative approaches when the variable has an extreme value distribution with heavy tail and the sample size is small.

Osakemarkkinoiden hintareaktiot luottoluokituksen muutokseen eri lainsäädäntöympäristössä

Tämän tutkielman tarkoituksena on selvittää reagoivatko osakemarkkinat eritavoin luottoluokituksen muutokseen eri lainsäädäntöympäristöissä. Lisäksi selvitetään myös reagoivatko pienten yhtiöiden osakekurssit erilailla luottoluokituksen muutokseen kuin suurten yhtiöiden osakekurssit. Tutkimusmenetelmänä käytetään tapahtumatutkimusta ja aineiston muodostavat Moody'sin luottoluokitusilmoitukset vuosilta 2000-2007. Tutkielman kohdemaina ovat Iso-Britannia, Ranska sekä Pohjoismaat Empiiristen tulosten perusteella ainoastaan luottoluokituksen laskun yhteydessä näyttää siltä, että lainsäädäntöympäristön ja markkinareaktion suuruuden välillä on oletetunkaltainen yhteys. Yrityskokoluokista puolestaan suurten yhtiöiden osakkeet reagoivat yleisesti voimakkaammin luottoluokituksen muutokseen kuin pienten yhtiöiden osakekurssit.

Eletrodissolução de ligas de latão empregando sistemas de análise em fluxo para a determinação de cobre, zinco e chumbo por ICP-AES

An on-line electrodissolution procedure implemented in a flow injection system for determination of copper, zinc and lead in brasses alloys by ICP-AES is described. Sample dissolution procedure was carried out by using a PTFE chamber and a DC power supply with constant current. Solid sample was attached to chamber as anode and a gold tubing coupled in the chamber was used as cathode. An electrolytic solution flowing through the gold tubing closed the electric circuit with sample, in order to provide condition for electric dissolution when the DC power supply was switched on. The best results were achieved by using a 1.5 mol l-1 nitric acid solution as electrolyte and a 2.5 A current intensity. The procedure presented a good performance characterized by a relative standard deviation better than < 5% (n=5) and a sample throughput of 180 determinations per hour for Cu, Zn and Pb. Results were in agreement with those obtained by conventional acid dissolution (99% confidence level).

Fair value versus historical cost-based valuation for biological assets: Predictability of financial information

There is an intense debate on the convenience of moving from historical cost (HC) toward the fair value (FV) principle. The debate and academic research is usually concerned with financial instruments, but the IAS 41 requirement of fair valuation for biological assets brings it into the agricultural domain. This paper performs an empirical study with a sample of Spanish farms valuing biological assets at HC and a sample applying FV, finding no significant differences between both valuation methods to assess future cash flows. However, most tests reveal more predictive power of future earnings under fair valuation of biological assets, which is not explained by differences in volatility of earnings and profitability. The study also evidences the existence of flawed HC accounting practices for biological assets in agriculture, which suggests scarce information content of this valuation method in the predominant small business units existing in the agricultural sector in advanced Western countries

Extração por fluido supercrítico de alguns inseticidas carbamatos em amostras de batata, com determinação por HPLC/fluorescência e confirmação por HPLC/espectrometria de massas

Six supercritical fluid extraction (SFE) methods were tested, by varying the following operational parameters: CO2 pressure, time and temperature of extraction, type and proportion of static modifier, and Hydromatrix®/sample rate into cell. Firstly, insecticide carbamates were extracted from spiked potatoes samples (fortification level of 0,5 mg.Kg-1) by using SPE procedures, and then final extracts were analyzed HPLC/fluorescence. Good performance was observed with SFE methods that operated with values of temperature and CO2 pressure of 50 ºC and 350 bar, respectively. Best efficiency was obtained when it was used acetonitrile as a modifier (3% on the cell volume), and Hydromatrix®/sample rate of 2:1. Static time was of 1 min; total extraction time was of 35 min; dynamic extraction was performed with 15 mL of CO2, and it was used methanol (2 mL) for the dissolution of the final residue. In such conditions, pesticide recoveries varied from 72 to 94%, depending on the analyzed compound. In higher extraction temperatures, a rapid degradation was observed for some compounds, such as aldicarb and carbaryl; presence of their metabolites was further confirmed by HPLC-APCI/MS in positive mode. Detection limits for chromatographic analysis varied from 0,2 to 1,3 ng.

Preparação de amostra de fígado bovino e estudo de micro homogeneidade para a determinação de Cd E Pb por espectrometria de absorção atômica com atomização eletrotérmica e amostragem direta de sólido

This work describes a systematic study for bovine liver sample preparation for Cd and Pb determination by solid sampling electrothermal atomic absorption spectrometry. Samples were prepared using different procedures: (1) drying in a household microwave oven followed by drying in a stove at 60 ºC until constant mass, and (2) freeze-drying. Ball and cryogenic mills were used for grinding. Particle size, sample size and micro sample homogeneity were investigated. All prepared samples showed good homogeneity (He < 10) even for low sample mass, but samples dried in a microwave oven/stove and ground in a ball mill presented the best homogeneity.

Teores de corantes artificiais em alimentos determinados por cromatografia líquida de alta eficiência

Synthetic dyes are much used in processed foods. HPLC was applied to different types of snacks, such as colored cereals, chocolate confetti, chewing gums and candies for the determination of those additives. In the case of artificially colored breakfast cereals, 71% of the samples exceeded the allowed limits. Regarding the portions recommended for consumption by the makers of two of the samples, the amounts exceeded those allowed by the Brazilian legislation. In the case of chocolate confetti and candies none of the samples showed higher amounts than those allowed. However 37% of the chewing gum samples presented larger contents than the authorized ones, and one sample contained five times more synthetic dyes than allowed.

Pré-concentração de cádmio com Saccharomyces cerevisiae e determinação em águas fluviais usando espectrometria de emissão óptica com plasma indutivamente acoplado

A preconcentration method based on the use of Saccharomyces cerevisiae as sorbent material is proposed for the determination of Cd(II) in river water. The solid phase extraction was performed in batch mode and the determination of the analyte in the solid phase was easily carried out by introducing a slurry of the yeast (0.0625 g / 2.5 mL) directly into the ICP OES. A limit of detection of 0.11 µg L-1 and a sample throughput in the range of 4 - 54 sample h-1 were obtained. Determinations of cadmium in a certified sample and in real river water samples were in excellent agreement with the expected values.

Utilização de zeólitas sintetizadas a partir de xisto retortado na remoção de arsênio em águas contaminadas

The solid by-product of the oil shale processing (PETROBRAS - Brazil) was used as raw material to synthesize zeolites A and faujasite. Alkaline fusion followed by hydrothermal treatment was the synthesis procedure used, and five different starting material compositions were obtained. The more crystalline zeolite-type materials synthesized, the pretreated oil shale ash and commercial zeolites were used as adsorbents in the purification of pollutant solutions with arsenic. The zeolite-type material composed of a mixture of zeolite A (42.6%) and faujasite (52.9%) presented an ion exchange capacity comparable to the pure zeolites A and faujasite, much better than the pretreated ash.

Determinação turbidimétrica do antidepressivo amitriptilina em sistema fia explorando a formação do par iônico com lauril sulfato de sódio

The present work purposes the development of an analytical method for amitriptyline determination in pharmaceutical formulations using FIA system. It was based on interaction of amitriplyline with sodium lauryl sulphate in acid medium (pH 2.5) resulting in the ion-pair formation turbidimetrically detected at 410 nm. The fitting regression equation for range curve from 2.0 x 10-3 up to 3.2 x 10-3 mol L-1 was found to be analytical signal = -2.7417 + 0.1538 [amitriptyline] (r = 0.99991) with a detection limit of 1.8 x 10-3 mol L-1. The precision assessed as relative standard deviation (n = 10) was found to be 2.40 and 1.94%, for the respective concentration of amitriplyline 2.0 x 10-3 and 3.2 x 10-3 mol L-1 and the sample throughout was 60 h-1. The accuracy of method was successfully assessed in pharmaceutical formulation after comparison with a reference analytical method.

Determinação simultânea de creatinina e indicadores biológicos de exposição ao tolueno, estireno e xilenos em urina por cromatografia líquida de alta eficiência

A simple liquid chromatographic method for the simultaneous determination of creatinine, hippuric acid, mandelic acid, phenylglyoxylic acid and o, m and p-methylhippuric acids was developed and validated. Sample preparation was only dilution with water (1:10), followed by centrifugation. Analysis was performed in a reversed phase column (Lichrospher RP 8ec), 250 x 4.0 mm, with isocratic elution with phosphate buffer pH 2.3 and acetonitrile (90:10, v/v). The method presents adequate linearity, precision and accuracy and allows the simultaneous determination of the biomarkers of exposure to toluene, xylene and styrene together with creatinine, reducing cost and laboratory time.

HIV - recentes avanços na pesquisa de fármacos

The development of new antiretroviral drugs is a dynamic process that is continuously fueled by identification of new molecular targets and new compounds for know targets. The current available drugs can be classified into five categories: nucleoside analogues reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors, protease inhibitors, integrase inhibitors and entry inhibitors (fusion inhibitors and CCR5 antagonist). In addition, the maturation inhibitors may be considered as potential target for chemotherapeutic intervention. This review presents some anti-HIV agents that have already gone through the advance development process for final approval for the treatment of AIDS.

Un sistema para la deteccion de antioxidantes volatiles comunmente emitidos desde especias y hierbas medicinales

An apparatus which allows the direct measurement of the antioxidant capacity of volatiles compounds emitted from some herbs and culinary spices is described. The device comprises: a sample chamber, a mixing chamber, a pump and, a detection system. Volatiles from Clove (Syzygium aromaticum (L.) Merr. & L.M. Perry) were purged and captured into a DPPH-containing solution and changes in the absorbance were recorded on-line. Linear response was observed when temperature was set between 30-53 ºC; nitrogen flow was 15 mL min-1 during 60 min; DPPH concentration was 20 µmol L-1 and a sample size (powdered Clove) ranged between 200-1000 mg.

Variação sazonal da composição do óleo essencial de Myrcia salzmannii Berg. (Myrtaceae)

This work report the seasonal variation of composition of the volatile oils from leaves and from flowers of Myrcia salzmannii harvested in the sand dunes of Salvador, Bahia, northeastern region of Brazil in the years 2001 and 2003. The oils were analyzed by GC-FID and GC-MS being identified 49 components. Nine essential oil samples of leaves collected on different months and years and one sample of flowers were analyzed. β-Caryophyllene and α-humulene were the only compounds present in all of the samples being the first the majority compound.