Preparation of a reference material for crude oil trace elements: Study of homogeneity and stability

Trace elements can be found naturally in crude oil or can be added during the production process, transport, or storage. Due to the complexity of the determination of trace elements in crude oil, which is mainly accomplished using multi-element techniques, many reports have been published describing the optimization of instrumental parameters, the development of procedures for sample preparation, and new sample introduction devices. The goal of such research is to improve the sensitivity, precision, and accuracy of the measurements. In all the cases mentioned above, the use of reference materials (RMs) and certified reference materials (CRMs) is recommended to verify the accuracy of the new methods proposed. This paper describes the development of a natural-matrix reference material for quantification of vanadium, nickel, magnesium, sodium, calcium, strontium, and barium in crude oil. 3 kg of crude oil was processed and distributed into 115 units, each containing 20 g. The homogeneity and stability of the prepared reference material were investigated using atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP OES), and inductively coupled plasma mass spectrometry (ICP-MS) techniques. The results were evaluated using standard univariate analysis of variance (ANOVA), regression analysis, and principal component analysis (PCA). Statistical evaluation of the data showed good homogeneity and stability of the candidate reference material under the conditions studied.