Integrated Analytical Characterization and Chemometric Classification of Selected Nigerian Crude Oils Using Physicochemical Analysis, GC–MS, ATR-FTIR Spectroscopy, and ICP–OES

Abstract

The comprehensive characterization of crude oil is essential for petroleum quality evaluation, refinery optimization, and environmental management. This study employed an integrated analytical approach combining physicochemical analyses, Gas Chromatography–Mass Spectrometry (GC–MS), Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy, Inductively Coupled Plasma Optical Emission Spectroscopy (ICP–OES), and chemometric techniques to characterize five Nigerian crude oils (Bonny Light, Forcados Blend, Qua Iboe, Escravos, and Brass River). Physicochemical analysis showed density values of 0.822–0.857 g cm⁻³, API gravity of 32.8–40.4°API, viscosity of 3.95–8.31 cSt, and sulfur content of 0.11–0.36 wt.%, confirming that all samples are light sweet crude oils. GC–MS analysis revealed that n-paraffins (34.12–42.36%) constituted the dominant hydrocarbon fraction, whereas aromatic hydrocarbons accounted for 11.58–15.57%, with Brass River crude exhibiting the highest aromatic content. ATR-FTIR spectra displayed characteristic aliphatic C–H stretching bands at 2921–2926 cm⁻¹ and 2852–2855 cm⁻¹, confirming the predominance of saturated hydrocarbons, while weaker aromatic and carbonyl absorption bands indicated lower concentrations of aromatic and oxygenated compounds. ICP–OES analysis showed calcium (23.46–36.85 mg kg⁻¹), iron (16.27–28.94 mg kg⁻¹), vanadium (5.18–10.74 mg kg⁻¹), and nickel (3.96–8.43 mg kg⁻¹) as the principal trace metals. Pearson correlation analysis demonstrated strong inverse relationships between API gravity and density (r = −0.985) and viscosity (r = −0.964), whereas Principal Component Analysis explained 86.9% of the total variance within the first two principal components. Hierarchical Cluster Analysis classified Qua Iboe and Bonny Light as compositionally similar high-quality crude oils and distinguished Brass River as the most compositionally distinct sample. The integrated analytical methodology proved effective for crude oil fingerprinting, quality assessment, refinery feedstock evaluation, and petroleum classification.