Determination of Cd and Pb in fuel ethanol by filter furnace electrothermal atomic absorption spectrometry

A method was developed for quantification of Cd and Pb in ethanol fuel by filter furnace atomic absorption spectrometry. Filter furnace was used to eliminate the need for chemical modification, to stabilize volatile analytes and to allow the application of short pyrolysis step. The determinations in samples were carried out against calibration solutions prepared in ethanol. Recovery tests were made in seven commercial ethanol fuel samples with values between 90 and 120%. Limits of detection were 0.1 µg L-1 for Cd and 0.3 µg L-1 for Pb. Certified water samples (APS 1071, APS 1033, NIST 1643d, NIST 1640) were also used to evaluate accuracy and recoveries from 86.8% to115% were obtained

Calibration techniques and modifiers for the determination of Cd, Pb and Tl in biodiesel as microemulsion by graphite furnace atomic absorption spectrometry

Different calibration approaches and modifiers were tested for Cd, Pb and Tl determination in biodiesel by graphite furnace atomic absorption spectrometry (GF AAS). Microemulsions were prepared by mixing 2 g of biodiesel, 1 mL of a 10% (v/v) nitric acid aqueous solution and n-propanol to a 10 mL final volume. Pyrolysis temperatures of 600 °C for Cd and Tl with Pd as permanent modifier, and 800 °C for Pb with Ru as permanent modifier were used. Atomization temperatures were also optimized. Calibration solution prepared in aqueous medium did not correct non-spectral interferences, but matrix matching calibration using base oil led to accurate results with recoveries from 80 to 116%. The RSD values were lower than 8% for Cd and Pb and the LOD values were 0.5 ng g-1 for Cd, 6 ng g-1 for Pb and 1 ng g-1 for Tl. The obtained results using the analyte additions method or by matrix matching calibration were in agreement, confirming the accuracy of the proposed procedure. Organometallic standards were not required and different samples were analyzed

Determination of trace metals in electrolytic copper by ICP OES and ICP-MS

The performance of axial view ICP OES and ICP-MS techniques were compared through the determination of As, Fe, Mn, Pb, Sb and Sn in electrolytic copper. Samples were prepared by two procedures: 1. Total dissolution with 5 % v/v HNO3 and 2. Dissolution with 1.4 % v/v HNO3 plus 2.0 % v/v H2SO4, followed by separation of the Cu by electrodeposition. The methods were applied for the analysis of standard copper solutions, using calibration against aqueous solutions with or without the addition of Cu. The results obtained by the two techniques were similar, but the separation of Cu from the sample matrix proved to be more adequate for practical reasons.<br>O presente trabalho apresenta um estudo comparativo das técnicas ICP-MS e ICP OES com configuração axial e também de dois métodos diferentes de tratamento das amostras, ou seja, por dissolução total com e sem separação do cobre por eletrodeposição, para as determinações de As, Fe, Mn, Pb, Sb e Sn em amostras de cobre eletrolítico. Amostras comerciais e industriais foram dissolvidas com HNO3 5% v/v e o cobre foi eletrodepositado em meio de HNO3 (1,4% v/v) e H2SO4 (2,0% v/v). Verificou-se que a separação do cobre foi eficiente, contudo se constatou contaminação de Fe e Sn durante o processo de eletrodeposição. As determinações foram realizadas utilizando-se um ICP OES Axial Varian (Vista Pro) e um ICP-MS Perkin Elmer (Elan Sciex 6000). Foi aplicada a calibração externa, com soluções padrão contendo ou não cobre na concentração equivalente à da amostra. Os limites de detecção (3s, n=10) para a técnica de ICP OES foram bastante semelhantes na presença ou não do cobre). Já usando ICP-MS, os limites foram melhores na ausência do cobre. Com o objetivo de estabelecer o nível de significância entre as técnicas de quantificação, ou seja, entre ICP OES e ICP-MS,foi aplicado o teste t emparelhado, que demonstrou, para um nível de confiança de 95%, não haver diferença significativa, tanto para as soluções sem ou com cobre. Os resultados obtidos no presente trabalho demonstraram que as técnicas ICP-MS e ICP OES fornecem resultados similares em determinadas faixas de concentração dos analitos, podendo ambas serem utilizadas, no controle de qualidade do cobre eletrolítico. Contudo, a técnica ICP-MS foi superior em termos de limite de detecção

Spectrophotometric determination of manganese in steels by on-line electrochemical oxidation

The aim of this work is to propose a flow spectrophotometric procedure for manganese determination in steel based on electrochemical oxidation of Mn(II) to Mn(VII) at a Pt electrode surface by means of the catalytic effect of Ag(I). The on-line oxidation step was obtained by injecting sample and electrolyte solution directly into an electrolytic cell. After electrolysis, the injectate was homogenized by bubbling air. The permanganate ions produced were passed through the spectrophotometer where absorbance was monitored at 545 nm. Effects of direct current, silver concentration, timing, flow rates, concentration and composition of support electrolyte were investigated. Direct current and silver content manifested themselves as the most relevant parameters. For determination of manganese in the 5.00 - 150 mg L -1 range (r=0,9998) and 60 s electrolysis time, the sample throughput was 20 h -1. Accuracy was assessed by analyzing ten steel standard reference materials. Results are precise (R.S.D. <3%) and in agreement with certified values of reference materials and with standard methods at 95% confidence level