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

Abstract

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.

Endospores associated with deep seabed geofluid features in the eastern Gulf of Mexico

“…Heavy metals are prevalent in crude oils can be used as proxies to understand the origins and processes of oil formation (dos Anjos et al, 2018 ; Maryutina & Timerbaev, 2017 ; Mdluli et al, 2020 ; Sokol et al, 2018 ; Walkner et al, 2017 ). In marine sediments, heavy metals tend to be present in high concentrations in deep‐to‐shallow conduit features like faults, trenches and subduction zones, due to mineral dissolution with upward fluid flow (Cangemi et al, 2010 ; Welty et al, 2018 ).…”

Functionalized and Platinum-Decorated Multi-Layer Oxidized Graphene as a Proton, and Electron Conducting Separator in Solid Acid Fuel Cells

“…The mass fraction of platinum on graphene samples was determined using inductively coupled plasma optical emission spectroscopy (ICP OES, SPECTRO Ciros Vision, SPECTRO Analytical Instruments GmbH, Kleve, Germany). The use of analytical techniques such as ICP OES provides more precise and accurate results regarding analyte concentration determination [97][98][99]. The platinum sample was digested in 28% vol/vol acid solution with a 6:1 volume ratio of HCl:HNO 3 in Millipore water for 30 min.…”

Recent Progress in Fast Sample Preparation Techniques

“…Compared to conventional digestion systems, microwave-assisted digestion shows higher digestion efficiency, more eco-friendly, and better instrument compatibility . Nowadays, this technique can combine with inductively coupled plasma to analyze heavy metal elements in foodstuff and oil samples.…”