Gisele G. Bortoleto

Determination of total inorganic arsenic in water using on-line pre-concentration and hydride-generation atomic absorption spectrometry.

A rapid and sensitive method for the on-line separation and pre-concentration of inorganic arsenic in water samples is described. The analyte in the pentavalent oxidation state is reduced to its trivalent form with l-cysteine and the total inorganic arsenic is sorbed onto activated alumina in the acid form in a mini-column coupled to a FI-HG AAS system. Afterwards, it is eluted with 3moll(-1) HCl. An enrichment factor of 7 was obtained, allowing an analytical flow rate of about 28 determinations per hour. The limits of detection (3sigma) and of quantification (10sigma) were calculated as LOD=0.15mugl(-1) of As and LOQ=0.5mugl(-1) of As, respectively. Relative standard deviations (n=10) less than 8% were obtained for different arsenic concentrations and the accuracy was verified by analysing certified reference materials. Different kinds of samples, such as mineral water, drinking water, river water and natural spring water were analyzed and good agreement was obtained with the values from spiked experiments.

Determination of cadmium by flame-atomic absorption spectrometry after preconcentration on silica gel modified with cupferron

A method for the determination of cadmium by flame atomic absorption spectrometry (FAAS) after its preconcentration onto a column containing silica gel modified with cupferron was developed. The pH, amount of adsorbent material, concentration of eluent, volume of sample and amount of Cd were optimized. The effect of several foreign ions was also investigated and showed that the retention of cadmium depended on the amounts of Zn(II) and Cu(II) present and that these interferences could be overcome by using a 0.05 mmol KI. An enrichment factor of up to 30 was obtained , the LOD was 0.5 µg L-1 (3s) and the LOQ was 2.0 µg L-1 (10s) with rsd of 1.1% (n = 10). The accuracy of the proposed method was ascertained by using certified reference material and the obtained result (3.93 ± 0.01 µg g-1) agrees with the certified value (4.15 ± 0.38 µg g-1). The determination of Cd in nail polish showed quantitative recoveries for the spiked samples. The proposed method is characterized by simplicity, efficiency and low cost.

Silica modified with zirconium oxide for on-line determination of inorganic arsenic using a hydride generation-atomic absorption system.

In the present work, an on-line pre-concentration system, using SiO(2)/ZrO(2) as solid phase adsorbent, for the determination of low concentrations of arsenic was developed. In this procedure, total inorganic arsenic present in the sample is reduced to As (III) with l-cysteine and the solution is passed into a glass column (varphi(i)=3mm; h=35mm) containing 70mg of SiO(2)/ZrO(2) (100-230 mesh) to retain the As (III), with the solution flowing at 3.2mLmin(-1). After 2min, the concentrated species are eluted with 3molL(-1) HCl (3.2mLmin(-1)) loading a 150muL loop while a 1.0% (m/v) sodium borohydride solution loads the other loop of a FI-HG AAS system. The elution step is carried out during 7s and, at the same time, the SiO(2)/ZrO(2) phase is regenerated for the next concentration cycle. The arsine generated is carried with N(2) (flow rate=90mLmin(-1)) to a quartz cell where the electrothermal atomization process occurs. Under these conditions, a 20-fold enrichment factor is obtained considering the increase of sensitivity in the analytical curve after the concentration step. The limits of detection and quantification were 0.05 and 0.35mugL(-1), respectively, with an injection frequency of about 28h(-1) and relative standard deviation lower than 8%. Four metallurgical reference materials were analyzed with the proposed method after their acid dissolution. The results obtained were in good agreement with certified values.

Marcos da história da radioatividade e tendências atuais

The first days of radioactivity, the discoveries of X-rays, radioactivity, of a- and b- particles and g- radiation, of new radioactive elements, of artificial radioactivity, the neutron and positron and nuclear fission are reviewed as well as several adverse historical marks, such as the Manhattan project and some nuclear and radiological accidents. Nuclear energy generation in Brazil and the world, as an alternative to minimize environmental problems, is discussed, as are the medicinal, industrial and food applications of ionizing radiation. The text leads the reader to reflect on the subject and to consider its various aspects with scientific and technological maturity.

Determinação de arsênio em águas contaminadas usando fluorescência de raios-X por energia dispersiva

This work proposes a simple, fast and inexpensive method to determine As in natural waters, using X-ray fluorescence. 50 µL of each sample containing 100 mg L-1 of yttrium as internal standard were deposited over a 2.5 µm thickness MylarTM film. The samples were dried at 50 °C for 2 h. X-ray spectra were obtained using an EDXRF apparatus. The accuracy was determined by analyte addition/recovery and by comparison with Hydride Generation Atomic Absorption Spectrometry (HG AAS). A recovery of about 100% was obtained and the results were in good agreement with HG AAS. The method showed a relative standard deviation of 6.8% and a detection limit of 10.5 µg L-1 of As.

Neutron activation analysis and X-ray Rayleigh and Raman scattering of hair and nail clippings as noninvasive bioindicators for Cu liver status in Labrador Retrievers

AbstractThe heritability of chronic hepatitis in the Labrador Retriever is studied with the aim of identifying the related gene mutation. Identification of cases and controls is largely based on instrumental neutron activation analysis (INAA) Cu determination in liver biopsies. The burden for these companion animals may be reduced if nail clippings and hair (fur) could serve as a noninvasive indicator for the hepatic Cu concentrations. No correlation was found between hepatic Cu concentrations and Cu concentrations in hair and nail samples. However, hair and nail samples were also analyzed by X-ray tube excitation, taking advantage of the X-ray Compton, Rayleigh, and Raman scattering which reflects the organic components such as the type of melanin. Principal component analysis provided first indications that some differentiation between healthy and sick dogs could indeed be obtained from hair and nail analysis. FigurePrincipal component analysis of scattered region of x-ray fluorescence spectra of Labrador dog nails, demonstrating the differentiation towards dogs with high and low Cu liver levels (respectively positive and negative PC2 values) reflecting hepatitis, as well as gender (PC1: negative values for female and positive values for males)

X-ray fluorescence and multivariate analysis for sucrose quantification in sugarcane

Currently the methods used for determining the sucrose content in sugarcane are made in the clarified juice. In this study portable energy dispersive X-ray fluorescence (EDXRF) together with chemometric tools was used to quantify sucrose through the stem, lief and juice. The best results were obtained for the stem, with means relative deviation of around 6%.