Evaluation of Brazilian and Venezuelan Crude Oil Samples by Means of the Simultaneous Determination of Ni and V as Their Total and Non-volatile Fractions Using High-Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry

• Published in: Energy & fuels 2010-11, Vol.24 (11), p.5907-5911
• Main Authors: Quadros, Daiane P. C, Chaves, Eduardo S, Lepri, Fábio G, Borges, Daniel L. G, Welz, Bernhard, Becker-Ross, Helmut, Curtius, Adilson J
• Format: Article
• Language: English
• Subjects: Fossil Fuels
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/ef100148d

The simultaneous determination of Ni and V as their total and non-volatile fractions in crude oil samples using high-resolution continuum source graphite furnace atomic absorption spectrometry is proposed. The simultaneous determination was possible because a secondary Ni line at 305.432 nm and a secondary V line at 305.633 nm are within the wavelength interval covered by the linear charge-coupled device array detector. Moreover, both analytes have similar volatility, enabling the use of the same pyrolysis and atomization temperatures. Oil-in-water emulsions were used for crude oil sample preparation. Nitric acid was added to the emulsion only for the determination of total Ni and V concentrations. In the absence of the acid, the volatile fractions have been lost in the pyrolysis stage and only the thermally stable fractions were determined. The concentration of the volatile fractions could be obtained by difference. The results for the total concentrations were in agreement with the certified values or those reported in the literature, with minor exceptions, for previously analyzed samples, according to a 95% statistical confidence interval. The limits of detection (3s; n = 10) were 3 μg g−1 for Ni and 1 μg g−1 for V. The precision, expressed as the relative standard deviation, was better than 9%. The characteristic mass values were 320 and 85 pg for Ni and V, respectively.