In the present paper, a preconcentration procedure based in the coprecipitation of copper by silver dichromate (Ag2CrO4) and consecutive determination by flame atomic absorption spectrometry (FAAS) was proposed. The experimental factors were optimized from application of the Doehlert matrix and the conditions set: chromate concentration 5.8 × 10-4 mol L-1, silver concentration 1.1 × 10-3 mol L-1, pH 7.3 and disperser concentration HNO3 0.38 mol L-1. Under these conditions, analytical parameters of the procedure were obtained, with the quantification limits of 0.76 µg L-1, precision (based in the relative standard deviation, RSD %) with values lower than 2.7%, and preconcentration factor of 28. The accuracy of the procedure was given by addition/recovery test in water samples groundwater and mineral, and by comparison with results obtained by ICP-MS. The procedure developed presented be simple, sensitive and low cost, thus can be applied in the preconcentration and determination of copper in several water samples.

Dois métodos para determinação de vanádio em óleo combustível são propostos utilizando GF AAS. O primeiro é baseado na preparação de uma microemulsão da amostra que é diretamente injetada no tubo de grafite. As temperaturas de pirólise e atomização, 1500 e 2700 ºC, respectivamente, foram otimizadas a partir das curvas de temperatura. Para este procedimento obteve-se um limite de detecção de 0,10 mg g-1 e uma massa característica de 87 pg. O outro método utiliza digestão da amostra com ácido sulfúrico, ácido nítrico e peróxido de hidrogênio. As temperaturas de pirólise e atomização, otimizadas, foram 1000 e 2700 ºC, respectivamente. Para este procedimento, obteve-se um limite de detecção de 0,25 µg g-1 e uma massa característica de 63 pg. A exatidão de ambos os métodos foi confirmada pela análise do material de referência certificado NIST SRM 1634c-trace metals in fuel oil.

Two methods for vanadium determination in fuel oil are proposed using GF AAS. The first is based on the preparation of a microemulsion followed by direct injection into the graphite tube. The pyrolysis and atomization temperatures, 1500 and 2700 ºC, respectively, were chosen from the temperature curves. This procedure allows determination of vanadium with a detection limit of 0.10 µg g-1 and characteristic mass of 87 pg. The other method uses total acid digestion of the sample with sulfuric acid, nitric acid and hydrogen peroxide. In this procedure, the pyrolysis and atomization temperatures recommended were 1000 and 2700 ºC, respectively. Among the analytical characteristics for this method are a detection limit of 0.25 µg g-1 and a characteristic mass of 63 pg. The accuracy of both procedures was confirmed by the determination of vanadium in the certified reference material NIST SRM 1634c-trace metals in fuel oil.