A green sample preparation strategy for Cl and S determination in crude oil by ion chromatography

A fast, eco-friendly, and straightforward method was developed for digesting crude oil using microwave-induced combustion (MIC), followed by Cl and S determination by ion chromatography (IC). The procedure involves directly weighing the crude oil on a filter paper disc placed on a quartz holder. The diluted reagents used included 6 mL of 50 mmol l^-1 NH₄OH, 50 µL of 6 mol l^-1 NH₄NO₃, and 20 bar of oxygen. Accuracy was evaluated using the certified reference material NIST 1634c and by comparing the results as outlined by American Society for Testing and Materials (ASTM) methods D6470-99(2020) for Cl and D7876-13(2018) for S. The MIC demonstrated an agreement of >95% in both evaluations. To assess the environmental impact of the proposed and official methods, the White Analytical Chemistry metric was employed. This approach enabled us to evaluate the ecological, analytical, and practical parameters, yielding scores of 82.5 and 64.0 for Cl, and 81.9 and 64.4 for S, for MIC and the ASTM methods, respectively. Under optimized conditions, MIC combined with IC proved efficient for the simultaneous determination of Cl and S in crude oil, surpassing traditional ASTM methods in analytical accuracy, environmental impact, and operational practicality. The proposed method offers an alternative for routine analysis in petrochemical laboratories, providing faster processing, reduced reagent consumption, and diminished environmental impact.