Tungsten permanent chemical modifier with co-injection of Pd(NO3)(2)+Mg(NO3)(2) for direct determination of Pb in vinegar by graphite furnace atomic absorption spectrometry

A tungsten carbide coating on the integrated platform of a transversely heated graphite atomizer (THGA((R))) used together with Pd(NO3)(2) + Mg(NO3)(2) as modifier is proposed for the direct determination of lead in vinegar by graphite furnace atomic absorption spectrometry. The optimized heating program (temperature, ramp time, hold time) of atomizer involved drying stage (110 degrees C, 5 s, 30 s; 130 degrees C, 5 s, 30 s), pyrolysis stage (1000 degrees C, 15 s, 30 s), atomization stage (1800 degrees C, 0 s, 5 s) and clean-out stage (2450 degrees C, I s, 3 s). For 10 mu L of vinegar delivered into the atomizer and calibration using working standard solutions (2.5-20.0 mu g L-1 Pb) in 0.2% (v/v) HNO3, analytical curve with good linear correlation (r = 0.9992) was established. The characteristic mass was 40 pg Pb and the lifetime of the tube was around 730 firings. The limit of detection (LOD) was 0.4 mu g L-1 and the relative standard deviations (n = 12) were typically <8% for a sample containing 25 pg L-1 Pb. Accuracy of the proposed method was checked after direct analysis of 23 vinegar samples. A paired t-test showed that results were in agreement at 95% confidence level with those obtained for acid-digested vinegar samples. The Pb levels varied from 2.8 to 32.4 pg L-1. Accuracy was also checked by means of addition/recovery tests and recovered values varied from 90% to 110%. Additionally, two certified reference materials were analyzed and results were in agreement with certified values at a 95% confidence level. (C) 2006 Elsevier Ltd. All rights reserved.

Use of sugar cane bagasse as solid phase extractor for cadmium determination by FAAS

The present paper describes the use of sugar cane bagasse as solid phase extractor for cadmium determination after complexation of the analyte with ammonium diethyldithiophosphate (ADDP) and sorption of the Cd-DDP complexes on the solid support. The concomitants were separated using a flow injection analysis (FIA) system coupled to flame atomic absorption spectrometry (FAAS) for determination. The main parameters such as ADDP concentration, acid medium, flow rate, reaction coil length, and reaction time were investigated.The results obtained with HNO3 showed good accuracy and precision. The enhancement factor was 20.5 times for a 120-second preconcentration time, and the analytical frequency was 25 determinations per hour. The calibration curve was linear over the concentration range of 1-40 mu g L-1 Cd with a LOD of 0.697 mu g L-1 Cd and a relative standard deviation of 0.96% after 12 successive measurements of 30 mu g L-1 Cd.The proposed method was evaluated for the FIA-FAAS analysis of certified reference materials (tomato leaves, spinach leaves, and bovine liver) and Cd-spiked foods (shrimp, sardine, tuna, chicken liver and bovine liver). Good recoveries (80.0-97.1%) for the Cd-spiked samples and certified reference materials were obtained. The results of bagasse-packed minicolumns were compared with Si-C,8 packed minicolumns. The F-test was applied between Si-C-18/Bagasse minicolumns, Si-C-18/certified values, and bagasse/certified values. It was found that the results were in agreement with the certified values at a 95% confidence level.

Evaluation of Ir, Ru, and W as permanent modifiers for the simultaneous determination of As, Bi, Pb, Sb, and Se in natural water by electrothermal atomic absorption spectrometry

Iridium-, Ru-, and W-coated platforms were prepared by thermal treatment of the transversely heated graphite atomizer and investigated for the simultaneous determination of As, Bi, Pb, Sb, and Se in tap water by electrothermal atomic absorption spectrometry. The maximum pyrolysis temperature for As and Bi increased in a modifier sequence W < Ru < Ir. For Pb, Sb, and Se, this sequence was W < Ru, It. Calculated characteristic masses in the presence of It, Ru, and W were 35, 33, and 35 pg for As; 63, 51, and 52 pg for Bi; 50, 32, and 34 pg for Pb; 40, 35, and 31 pg for Sb; and 39, 39, and 93 pg for Se, respectively. Ruthenium was elected as the optimum modifier.Repeatability of the measurements was typically < 6%. Recoveries of As, Bi, Pb, Sb, and Se added to tap water samples varied from 79 to 109%. Accuracy was also checked by analysis of five certified reference materials (CRMs) from the National Institute of Standards and Technology (NIST1640 - Trace Elements in Natural Water; NIST 1643d Trace Elements in Water) and High Purity Standards (Trace Metals in Drinking Water Standards, lots #812708, #591107, and #710710). A paired t-test showed that the results for the CRMs were in agreement at the 95% confidence level with the certified values. The graphite tube lifetime was about 650 firings. multi-element determination is particularly challenging due to the necessity of carefully optimizing compromise conditions.Based on the considerations listed above, the aim of this paper was to evaluate the behavior of Ir, Ru, and W as permanent modifiers for the simultaneous determination of As, Bi, Pb, Sb, and Se. The performance of the proposed procedure was also verified after the ETAAS analysis of tap waters and reference materials.

Reversible intermittent flow-injection determination of mercury in sediments and vinasses by cold vapor atomic absorption spectrometry

A reversible intermittent pow-injection procedure is proposed for the automated determination of mercury in sediments and vinasses by cold vapor atomic absorption spectrometry, CVAAS. Solutions of sample and stannous chloride are carried by two air streams and sequentially injected into the generator/separator chamber in a segmented asynchronous merging zone configuration. The intermittent flow in the forward direction carries the mercury vapor through the flow cell, and in the backward direction, if aspirates the the remaining solution from the vessel to waste. We investigated composition and concentration of reagents, pow rates, commutation times, reactor configuration, and conditions for mercury release. The accuracy was checked by mercury determination in a certified sediment and spiked vinasses and river waters. The system handles about 100 samples per hour (0.50-5.00 mu g L-1), consuming ca. 2.5 mL of sample and 50 mg of SnCl2 per determination; Good recoveries (92-103%) were obtained with spiked samples. Results are precise (RSD <3% for 2.5 mu g Hg L-1, n = 12) and in agreement with values for certified reference material at 95% confidence level. (C) 1999 John Wiley & Sons, Inc.

Seasonal influence on hematologic values and hemoglobin electrophoresis in Brazilian Boa constrictor amarali

As ectothermic animals, snakes depend exclusively on the environment for proper temperature maintenance, which may greatly influence their activity. Twenty-five adult Boa constrictor amarali snakes maintained in captivity were used to determine the influence of seasons on their hematologic values and electrophoretic profile of hemoglobin. A complete blood cell count (CBC) and examination for hemoparasites were performed in the summer and winter of 2004. Hemoglobin was stored for later electrophoresis. Significant differences (P < 0.05) were obtained in RBC, WBC. lymphocyte, thrombocyte, and monocyte counts, demonstrating the importance of the period of the year in the interpretation of reference values in these animals. Two snakes were detected with blood parasites (Hepatozoon sp.) in the winter and four in the summer. although it appears that their presence did not cause any significant alterations in the CBC. The electrophoretic analysis of the samples demonstrated two-four hemoglobin bands in this species.

Design of a CMOS voltage reference using current-model approach

A voltage reference with low sensibility to temperature and power-supply that can generate flexible reference values (from milivolts to several volts) is proposed. Designed for AMS 0.35μm CMOS process, the circuit provides a stable output voltage working in the temperature range of -40-150°C. The proposed reference provides a nominal output voltage of 1.358V with a power-supply of 3.3V. © 2011 IEEE.

A simple method based on HR-CS FAAS for multi-element determination of Cu, Fe, Mn and Zn in medicinal plants

A simple method to determine Cu, Fe, Mn and Zn in single aliquots of medicinal plants by HR-CS FAAS is proposed. The main lines for Cu, Mn and Zn, and the alternate line measured at the wing of the main line for Fe at 248.327 nm allowed calibration within the 0.025 - 2.0 mg L-1 Cu, 1.0 - 20.0 mg L-1 Fe, 0.05 - 2.0 mg L-1 Mn, 0.025 - 0.75 mg L-1 Zn ranges. Nineteen medicinal plants and two certified plant reference materials were analyzed. Results were in agreement at a 95% confidence level (paired t-test) with reference values. Limits of detection were 0.12 μg L-1 Cu, 330 μg L-1 Fe, 1.42 μg L-1 Mn and 8.12 μg L-1 Zn. Relative standard deviations (n=12) were ≤ 3% for all analytes. Recoveries in the 89 - 105% (Cu), 95 - 108% (Fe), 94 - 107% (Mn), and 93 - 110% (Zn) ranges were obtained.

Simple procedure for nutrient analysis of coffee plant with energy dispersive X-ray fluorescence spectrometry (EDXRF)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Desenvolvimento de um sensor de amálgama sólido para a determinação de enxofre em microemulsões de biodiesel

Pós-graduação em Química - IQ

Determinação simultânea de 'CD' e 'PB' e de 'CR' e 'NI' em plantas medicinais empregando a espectrometria de absorção atômica com amostragem direta de suspensões

Pós-graduação em Química - IQ

Establishing the reference range for t lymphocytes subpopulations in adults and children from Brazil

Os valores de referências de linfócitos T existentes no Brasil são baseados em dados originados de outros países. Não existem dados locais da variação normal para estes parâmetros em adultos e crianças brasileiras. Avaliamos a variação normal encontrada em doadores de sangue de cinco grandes cidades brasileiras em diferentes regiões e em crianças residentes em Salvador e Rio de Janeiro. Todas as amostras foram processadas por citometria de fluxo. Os resultados foram analisados de acordo com região, gênero e estilo de vida dos doadores. Um total de 641 adultos (63% homens) e 280 crianças (58% meninos) participaram do estudo. Valores absolutos de CD3+ e CD4+ foram significantemente maiores no gênero feminino (adultos e crianças). Maiores valores de CD4+ em adultos foram associados com tabagismo, enquanto que maiores valores de CD8+ foram encontrados entre crianças do sexo feminino. Adultos das regiões sul e sudeste apresentaram maiores valores absolutos para todas as células T enquanto que adultos da região norte, apresentaram menores valores. Indivíduos residentes no nordeste e centro-oeste obtiveram contagens intermediárias para todas as populações de células T. Entretanto, estas diferenças entre as regiões, não demonstraram diferença estatística. No Brasil, gênero e tabagismo foram os principais determinantes para diferenças em valores de referências de linfócitos T.

Amostragem de sólidos em espectrometria de absorção atômica de fonte contínua com alta resolução: análise de plantas medicinais

Pós-graduação em Química - IQ

A simple and fast method for assessment of the nitrogen-phosphorus-potassium rating of fertilizers using high-resolution continuum source atomic and molecular absorption spectrometry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

High-throughput sugarcane leaf analysis using a low cost closed-vessel conductively heated digestion system and inductively coupled plasma optical emission spectroscopy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Elementos-traço em dois latossolos após aplicações anuais de lodo de esgoto por treze anos

This experiment aim was to evaluate the contamination of the trace elements (TE) arsenic, barium, cadmium, chromium, copper, mercury, molybdenum, nickel, lead, selenium, and zinc considered in the CONAMA resolution 375 after 13 years long using sewage sludge (SS) as fertilizer in two soils: an Eutroferric Clayed Red Latosol (Rhodic Eutrudox - RE) and a Dystrophic Red Latosol (Typic Haplorthox - TH). Experiment in the field under maize cultivation had four treatments (0, 5, 10, and 20 t of SS ha(-1), dry weight), five replications and an experimental design in randomized blocks. The agrochemicals (dolomitic limestone, single superphosphate, and potassium chloride), SS, soils, and the certified reference materials were digested according to the USEPA 3051A method and the chemical elements were quantified by ICP OES. The TE contents found in the agrochemicals used should not cause immediate environmental impact. The higher TE values were found in the RE and they did not reach the agricultural (more stringent) Investigation Level (IL) yet, according to 420 CONAMA resolution. Persisting the actual SS fertilization amount applied in the soil and the TE concentration in the SS is foreseen that Ba, Cd, Cr, Cu, Ni, and Zn will be the first elements to reach the IL in the RE.