Comparative Evaluation of Organic Solvent Extraction for GC-MS Profiling of Petroleum Hydrocarbons in Groundwater and Refinery Wastewater Samples from the Fergana Oil Refinery, Uzbekistan

Abstract

Petroleum hydrocarbons are among the major environmental contaminants released into aquatic systems through petroleum refining operations, industrial activities and wastewater discharge processes. Accurate determination of these compounds requires efficient extraction procedures and reliable analytical techniques, as the extraction step greatly influences hydrocarbon recovery and analytical sensitivity. In the present study, the extraction performance of selected organic solvents, namely chloroform, n-hexane and carbon tetrachloride, was comparatively evaluated for petroleum hydrocarbon analysis in natural and industrial wastewater samples using gas chromatography–mass spectrometry (GC-MS). Natural and wastewater samples were collected from different locations associated with the Fergana Oil Refinery, Uzbekistan, including observation boreholes, wastewater discharge points, wastewater collection basins and treated wastewater outlets. Prior to extraction and chromatographic analysis, the physico-chemical properties of the collected samples were investigated to assess variations in water quality and contamination characteristics. GC-MS analysis enabled the successful identification of petroleum hydrocarbon compounds distributed across different molecular fractions. Comparative assessment of the extraction solvents demonstrated significant differences in extraction efficiency and chromatographic performance. Among the investigated solvents, chloroform exhibited superior extraction capability, providing broader chromatographic coverage and higher hydrocarbon recovery compared with n-hexane and carbon tetrachloride. Statistical analysis further confirmed significant variations among the extraction solvents (p < 0.05). The wastewater samples showed substantially higher petroleum hydrocarbon concentrations than groundwater samples, reflecting the greater impact of petroleum refining and wastewater discharge activities on industrial water systems. The developed analytical method demonstrated satisfactory analytical performance with acceptable precision, reproducibility and recovery characteristics. The findings indicate that optimization of extraction conditions significantly influences petroleum hydrocarbon determination and may contribute to improved environmental monitoring and contamination assessment of petroleum-affected water systems.