Journal
TALANTA
Volume 144, Issue -, Pages 1052-1058Publisher
ELSEVIER
DOI: 10.1016/j.talanta.2015.07.060
Keywords
Microwave-assisted wet digestion; Ultraviolet digestion; Petroleum coke analysis; ICP-OES; Diluted acids; Green sample preparation; Ni; V and S determination
Categories
Funding
- Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)
- Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)
- Fundacao de Amparo a Pesquisa do Estado do Rio Grande do Sul (FAPERGS)
- Centro de Pesquisa e Desenvolvimento Leopoldo Americo Miguel de Mello (CENPES-PETROBRAS)
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A method for the simultaneous determination of Ni, V and S in petroleum coke by inductively coupled plasma optical emission spectrometry (ICP-OES) after microwave-assisted ultraviolet digestion (MW-UV) in closed vessels was proposed. Digestion was performed using electrodeless discharge lamps positioned inside quartz vessels and turned on by microwave radiation. The following parameters were evaluated: HNO3 concentration (15 mL of 1, 4, 7, 10 or 14.4 mol L-1), volume of H2O2 (30%, 1 or 3 mL), sample mass (100, 250 or 500 mg) and heating time (40 or 60 min) with or without the use of UV lamps. Digestion efficiency was evaluated by the determination of the residual carbon content (RCC) in digests. Using UV lamps lower RCC was obtained and the combination of 4 mol L-1 HNO3 with 3 mL of H2O2 and 60 min of heating allowed a suitable digestion of up to 500 mg of petroleum coke (RCC < 21%). The agreement with the reference values for Ni, V and S (obtained by digestion of petroleum coke by microwave-induced combustion) and with a certified reference material of petroleum coke was between 96 and 101%. The proposed method was considered as advantageous when compared to American Society for Testing and Materials method because it allowed the simultaneous determination of Ni, V and S with lower limit of detection (0.22, 0.12 and 8.7 mu g g(-1) for Ni, V and S, respectively) avoiding the use of concentrated nitric acid and providing digests suitable for routine analysis by ICP-OES. (C) 2015 Elsevier B.V. All rights reserved.
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