Optimization And Validation Of Analytical Methods For Trace Metal Analysis In Heavy Crude Oils By Flame Atomic Absorption Spectrophotometry

Abstract

Background -The determination of trace metals in heavy crude oils is essential for quality assessment, environmental monitoring, and refining processes. Various analytical methods are employed for this purpose, with flame atomic absorption spectrophotometry (FAAS) being widely used due to its accuracy and cost-effectiveness. However, method optimization and validation are crucial to ensure reliable results. Aim and Objectives Aim -To optimize and validate analytical methods for trace metal analysis in heavy crude oils using Flame Atomic Absorption Spectrophotometry (FAAS) for improved accuracy and reliability. Objectives Compare sample preparation methods (Dry Ashing, Direct Dilution, Standard Addition) for metal analysis. Optimize FAAS parameters to enhance detection accuracy and precision. Assess the impact of API gravity and sulfur content on metal concentrations. Identify and correct matrix interferences affecting FAAS measurements. Establish a validated method for routine trace metal analysis in petroleum samples. Methods-Heavy crude oil samples were collected from selected oil fields and subjected to three different sample preparation methods: dry ashing-acid dissolution (DA), direct dilution (DD), and standard addition (SA). FAAS was used to determine the trace metal concentrations. The methods were validated by assessing precision, accuracy, detection limits, and matrix effects. Correlations between metal concentrations and crude oil properties, such as API gravity and sulfur content, were analyzed statistically. Results-The DA method exhibited superior accuracy and precision compared to DD and SA methods, particularly for heavy crude oils with low API gravity. The V/Ni ratio ranged between 3.5 and 5.2, indicating the sapropelic nature of the organic matter. A strong inverse correlation was observed between metal content and API gravity (R² > 0.88). Additionally, sulfur content showed a significant positive correlation with V and Ni concentrations. The SA method was found to be effective in minimizing matrix interferences, especially in highly viscous crude oils. Conclusion-FAAS is a reliable technique for trace metal analysis in heavy crude oils, provided that appropriate sample preparation methods are used. The DA method is recommended for improved accuracy, while the SA method offers a viable alternative for highly viscous samples. The findings highlight the importance of method optimization in crude oil analysis to enhance data reliability for industrial and environmental applications.