Dos Anjos Shirlei L, Alves Jeferson C, Rocha Soares Sarah A, Araujo Rennan G O, de Oliveira Olivia M C, Queiroz Antonio F S, Ferreira Sergio L C
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.
Universidade Federal da Bahia, Instituto de Geociências, CEP 40170-290 Salvador, BA, Brazil.
Talanta. 2018 Feb 1;178:842-846. doi: 10.1016/j.talanta.2017.10.010. Epub 2017 Oct 7.
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, 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 for nickel and from 0.63 to 19.42μgg for vanadium.
本研究采用微波辅助消解优化样品前处理程序，结合电感耦合等离子体发射光谱法（ICP OES）测定原油中的镍和钒。优化步骤采用二水平全因子设计，涉及以下因素：浓硝酸和过氧化氢体积以及微波辅助消解温度。以镍和钒的浓度作为响应值。此外，基于浓度与最高值归一化建立了多响应值，以确定两种分析物之间的折衷条件。采用Doehlert矩阵优化ICP OE光谱仪的仪器条件，以等离子体稳健性作为化学计量学响应值。实验使用掺杂镁（II）离子的消解油样溶液以及标准镁溶液进行。优化后的方法对于0.1g消解样品，镍和钒的定量限分别为0.79和0.20μg/g。通过对两个油样进行五次重复测定来确定精密度（以相对标准偏差表示），镍的结果为1.63%和3.67%，钒的结果为0.42%和4.64%。还测试了铋和钇作为内标，结果表明钇能使该方法具有更好的精密度。通过分析燃油中认证参考物质微量元素（CRM NIST 1634c）确认了准确性。所提出的方法应用于测定来自巴西盆地的五个原油样品中的镍和钒。镍的金属浓度在7.30至33.21μg/g之间，钒的金属浓度在0.63至19.42μg/g之间。
