Development and Optimization of Analytical methods for Sulfolane and BTEX Quantification in Environmental samples

Abstract

Sulfolane is an industrial solvent widely used in various industries, particularly the petrochemical sector. It is highly mobile in the environment due to its water miscibility at slightly above room temperature and minimal adsorption onto most soil types. Furthermore, sulfolane is a relatively stable compound, with aerobic biodegradation serving as its primary degradation pathway. However, its high mobility allows it to contaminate groundwater, where anaerobic conditions can lead to prolonged persistence. Additionally, sulfolane can migrate into fractured rock structures within groundwater zones, where small pores may trap contaminants, further prolonging environmental contamination. Given the large annual volumes of sulfolane usage, accidental releases are inevitable. Despite significant gaps in toxicological research, sulfolane is recognized as a neurotoxin and may disrupt multiple physiological systems, including the circulatory, hepatic, and reproductive systems. Due to these potential health risks, it is crucial to conduct environmental risk assessments, beginning with the measurement of sulfolane concentrations in environmental matrices. Sulfolane is rarely used in isolation and is often co-released with other organic solvents and chemicals. Its physicochemical properties, particularly its high solubility in both water and organic solvents, can influence the environmental distribution of co-contaminants. One important group of such co-contaminants commonly associated with sulfolane in the petrochemical industry are BTEX (benzene, toluene, ethylbenzene, and xylenes). BTEX compounds are well-established environmental pollutants with documented adverse effects on human health, including neurotoxicity, hematologic malignancies and damage to multiple organ systems. Therefore, monitoring BTEX alongside sulfolane is essential to understanding potential interactions and cumulative risks. In this study, two gas chromatography-mass spectrometry (GC-MS) methods were developed, optimized, and validated for the quantification of sulfolane in rock and groundwater samples. The methods were designed to be simple and environmentally friendly, minimizing the use of organic solvents. Due to the distinct characteristics of each matrix, tailored extraction techniques were employed. For rock samples, a microwave-assisted extraction method using methanol was developed to expedite contaminants extraction. The method was validated, and sulfolane stability in methanol extracts was assessed, confirming its stability for up to one year post-collection. The method was applied to 109 rock core samples from a contaminated site in Alberta, Canada, revealing sulfolane contamination in only one sample, while toluene and ethylbenzene were the most prevalent contaminants. For groundwater samples, an in-vial extraction method utilizing dichloromethane was developed. The method was validated, and assessed for ruggedness. Benzene was identified as the most susceptible to loss during sample preparation. Stability assessments showed that sulfolane remained stable in refrigerated water samples for up to 23 days. The method was then applied to 97 surface water and groundwater samples collected from a contaminated site in Alberta, Canada. Results indicated that sulfolane concentrations exceeded Health Canada's maximum acceptable contamination levels in 17 out of 50 locations, whereas only a few samples exhibited BTEX concentrations exceeding regulatory guidelines. Overall, this study successfully developed and validated methods for detecting sulfolane in environmental samples, contributing to a better understanding of its distribution in contaminated sites. However, further sampling and analysis are required to comprehensively assess sulfolane’s fate and transport at the study site.