Multivariate optimization of a procedure employing microwave-assisted digestion for the determination of nickel and vanadium in crude oil by ICP OES.

Autor: Dos Anjos SL; Universidade Federal da Bahia, Instituto de Química, Grupo de Pesquisa em Química e Quimiometria, CEP 40170-290 Salvador, BA, Brazil; Instituto Nacional de Ciência e Tecnologia, INCT de Energia e Ambiente, Universidade Federal da Bahia, 40170-290 Salvador, BA, Brazil., Alves JC; Universidade Federal da Bahia, Instituto de Geociências, CEP 40170-290 Salvador, BA, Brazil., Rocha Soares SA; Universidade Federal da Bahia, Instituto de Geociências, CEP 40170-290 Salvador, BA, Brazil., Araujo RGO; Universidade Federal da Bahia, Instituto de Química, Grupo de Pesquisa em Química e Quimiometria, CEP 40170-290 Salvador, BA, Brazil; Instituto Nacional de Ciência e Tecnologia, INCT de Energia e Ambiente, Universidade Federal da Bahia, 40170-290 Salvador, BA, Brazil., de Oliveira OMC; Universidade Federal da Bahia, Instituto de Geociências, CEP 40170-290 Salvador, BA, Brazil., Queiroz AFS; Universidade Federal da Bahia, Instituto de Geociências, CEP 40170-290 Salvador, BA, Brazil., Ferreira SLC; Universidade Federal da Bahia, Instituto de Química, Grupo de Pesquisa em Química e Quimiometria, CEP 40170-290 Salvador, BA, Brazil; Instituto Nacional de Ciência e Tecnologia, INCT de Energia e Ambiente, Universidade Federal da Bahia, 40170-290 Salvador, BA, Brazil. Electronic address: slcf@ufba.br.
Jazyk: angličtina
Zdroj: Talanta [Talanta] 2018 Feb 01; Vol. 178, pp. 842-846. Date of Electronic Publication: 2017 Oct 07.
DOI: 10.1016/j.talanta.2017.10.010
Abstrakt: This work presents the optimization of a sample preparation procedure using microwave-assisted digestion for the determination of nickel and vanadium in crude oil employing inductively coupled plasma optical emission spectrometry (ICP OES). The optimization step was performed utilizing a two-level full factorial design involving the following factors: concentrated nitric acid and hydrogen peroxide volumes, and microwave-assisted digestion temperature. Nickel and vanadium concentrations were used as responses. Additionally, a multiple response based on the normalization of the concentrations by the highest values was built to establish a compromise condition between the two analytes. A Doehlert matrix optimized the instrumental conditions of the ICP OE spectrometer. In this design, the plasma robustness was used as chemometric response. The experiments were performed using a digested oil sample solution doped with magnesium(II) ions, as well as a standard magnesium solution. The optimized method allows for the determination of nickel and vanadium with quantification limits of 0.79 and 0.20μgg -1 , respectively, for a digested sample mass of 0.1g. The precision (expressed as relative standard deviations) was determined using five replicates of two oil samples and the results obtained were 1.63% and 3.67% for nickel and 0.42% and 4.64% for vanadium. Bismuth and yttrium were also tested as internal standards, and the results demonstrate that yttrium allows for a better precision for the method. The accuracy was confirmed by the analysis of the certified reference material trace element in fuel oil (CRM NIST 1634c). The proposed method was applied for the determination of nickel and vanadium in five crude oil samples from Brazilian Basins. The metal concentrations found varied from 7.30 to 33.21μgg -1 for nickel and from 0.63 to 19.42μgg -1 for vanadium.
(Copyright © 2017. Published by Elsevier B.V.)
Databáze: MEDLINE
Externí odkaz: