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A cloud point extraction procedure for pre-concentration and determination of cadmium and lead in drinking water using sequential multi-element flame atomic absorption spectrometry is described. 4-(2-thiazolylazo)-orcinol (TAO) has been used as complexing agent and the micellar phase was obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The conditions for reaction and extraction (surfactant concentration, reagent concentration, effect of incubation time, etc) were studied and the analytical characteristics of the method were determined. The method allows the determination of cadmium and lead with quantification limits of 0.30 µg L−1 and 2.6 µg L−1, respectively. A precision expressed as relative standard deviation (RSD, n = 10) of 2.3% and 2.6% has been obtained for cadmium concentrations of 10 µg L−1 and 30 µg L−1, respectively, and RSD of 1.3% and 1.7% for lead concentrations of 10 µg L−1 and 30 µg L−1, respectively. The accuracy was confirmed by an...

The present work proposes the use of Agave sisalana (sisal fiber) as an natural adsorbent for ions Pb(II) and Cd(II) biosorption from natural waters. The flame atomic absorption spectrometry was used for quantitative determination and study of the ions Pb(II) and Cd(II) adsorption on the solid phase. The Fourier transform infrared spectroscopy (FT IR) was used to investigate the sisal structure and the specific BET surface area was analyzed. The biosorption potential of sisal as biosorbent for the removal of the ions Pb(II) and Cd(II) from aqueous solution was investigate considering the followings parameters: pH, biomass amount and contact time. Langmuir and Freundlich isotherms were used to evaluate adsorption behavior of the ions on this solid phase. The results showed that sisal has a surface area to adsorption of 0.0233 m2 g− 1, and the OH and CO functional groups are the main involved in the biosorption. The best interpretation for the experimental data was given by Freundlich isotherm that proposes a monolayer sorption with a heterogeneous energetic distribution of active sites, accompanied by interactions between sorbed molecules. The maximum monolayer biosorption capacity was found to be 1.85 mg g− 1 for Cd (II) and 1.34 mg g− 1 for Pb (II) at pH 7 and 296 K. This phase solid can be used for biosorption of cadmium and lead in polluted natural waters.

A method was developed for determination of total antimony in hair samples from patients undergoing chemotherapy against Leishmaniasis based on the administration of pentavalent antimonial drugs. The method is based on microwave assisted digestion of the samples in a pressurized system, reduction of Sb5+ to Sb3+ with KI solution (10% w/v) in ascorbic acid (2%, w/v) and its subsequent determination by hydride generation atomic fluorescence spectrometry (HG-AFS). The proportions of each component (HCl, HNO3 and water) used in the digestion were studied applying a constrained mixtures design. The optimal proportions found were 50% water, 25% HNO3 and 25% HCl. Variables involved in the generation of antimony hydride were optimized using a Doehlert design revealing that good sensitivity is found when using 2.0% w/v NaBH4 and 4.4 mol L-1 HCl. Under the optimum experimental conditions, the method allows the determination of antimony in hair samples with detection and quantification limits of 1.4 and 4.6 ng g-1, respectively, and precision expressed as relative standard deviation (RSD) of 2.8% (n = 10 to 10.0 mg L-1). The developed method was applied in the analysis of hair samples from patients who take medication against Leishmaniasis.

The atemoya is a hybrid fruit obtained by crossing of cherimoya (Annona cherimola Mill.) with sweet sop (Annona squamosa L.). The information about chemical composition of atemoya is scarce. The mineral composition was evaluated employing Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES) and the centesimal composition and the physico-chemical parameters were assessed employing procedures described in the AOAC methods. The total phenolic compounds (TPC) and total flavonoids (TF) were determined using spectroanalytical methods. Considering the Reference Daily Intake (RDI), the concentrations of K, Cu and Vitamin C found in atemoya were the highest, representing about 32, 23 and 37% of the RDI, respectively. The total carbohydrates were 32 g 100g-1 and the soluble solids was equivalent to (32.50 ± 0.03) °Brix. The result for TPC was 540.47 ± 2.32 mgGAE 100 g-1 and the TF was 11.56 ± 1.36 mgQE 100 g-1. The exploratory evaluation of 42 atemoya samples was performed through Principal Component Analysis (PCA), which discriminated green and ripe fruits according to their mineral composition. The elements that contributed most for the variability between green and ripe fruits were: Ba, Ca, Cu, K, Mg and P.

This work proposes a procedure for the determination of total selenium content in shellfish after digestion of samples in block using cold finger system and detection using atomic fluorescent spectrometry coupled hydride generation (HG AFS). The optimal conditions for HG such as effect and volume of prereduction KBr 10 % (m/v) (1.0 and 2.0 ml) and concentration of hydrochloric acid (3.0 and 6.0 mol L(-1)) were evaluated. The best results were obtained using 3 mL of HCl (6 mol L(-1)) and 1 mL of KBr 10 % (m/v), followed by 30 min of prereduction for the volume of 1 mL of the digested sample. The precision and accuracy were assessed by the analysis of the Certified Reference Material NIST 1566b. Under the optimized conditions, the detection and quantification limits were 6.06 and 21.21 μg kg(-1), respectively. The developed method was applied to samples of shellfish (oysters, clams, and mussels) collected at Todos os Santos Bay, Bahia, Brazil. Selenium concentrations ranged from 0.23 ± 0.02 to 3.70 ± 0.27 mg kg(-1) for Mytella guyanensis and Anomalocardia brasiliana, respectively. The developed method proved to be accurate, precise, cheap, fast, and could be used for monitoring Se in shellfish samples.

Texto completo: acesso restrito. p.1128-1132 Submitted by Edileide Reis (leyde-landy@hotmail.com) on 2015-03-23T13:24:21Z No. of bitstreams: 1 Walter N. L. dos Santos.pdf: 138345 bytes, checksum: a3711fb85e7828413ceb554f9d4daa0d (MD5) Made available in DSpace on 2015-03-23T13:24:21Z (GMT). No. of bitstreams: 1 Walter N. L. dos Santos.pdf: 138345 bytes, checksum: a3711fb85e7828413ceb554f9d4daa0d (MD5) Previous issue date: 2013 This paper proposes a procedure for the determination of total arsenic in rice using slurry sampling and hydride generation atomic fluorescence spectrometry (HG AFS). During optimization, water, hydrochloric acid, and nitric acid solutions were tested as extractor. Best results were found using 2.0 mol L−1 nitric acid solutions. The slurries are prepared using 200 mg of rice sample, 5.0 mL of nitric acid solution, and sonication for 30 min. Then, an aliquot of 5.0 mL of the slurry was taken and 3.0 mL of 1.5 mol L−1 hydrochloric acid solution and 1.5 mL of 10 % potassium iodide in 2 % ascorbic acid solution were added. After 30 min, the volume was completed up to 10 mL with ultra-pure water and arsenic quantified by HG AFS. In these experimental conditions, the method allows the determination of arsenic employing external calibration, with limits of detection and quantification of 1.1 and 3.3 ng g−1 and precision expressed as relative standard deviation (%RSD) varying between 5.9 and 1.3 % for arsenic concentration of 0.12 and 0.47 μg g−1. Accuracy was confirmed by analysis of the NIES standard reference material for rice flour, SRM 10b. This method was used to determine the arsenic content in 20 rice samples that were purchased at supermarkets in Salvador, Bahia, Brazil. The arsenic content for the three types of rice (white, parboiled, and brown) varied from 0.12 and 0.47 μg g−1. Some of the samples were also analyzed by HG AFS after complete mineralization in block digester employing a reflux system (cold finger). A statistical test showed that there was no significant difference between the results obtained using slurry sampling and those obtained after complete digestion of the sample.