Simultaneous analysis of sulfolane and BTEX in rock samples by gas chromatography–mass spectrometry

Sulfolane is a water-miscible industrial solvent that has been widely utilized in various industries. Once released into the environment, it can infiltrate fractured rock structures in groundwater zones, leading to long-term contamination. Benzene, toluene, ethylbenzene, and xylenes (collectively known as BTEX) are commonly associated with sulfolane in the petrochemical industry. The presence and mobility of sulfolane can influence the distribution and transport behavior of BTEX at contaminated sites. Therefore, simultaneous analysis and monitoring of these compounds are crucial for understanding the source and fate of contamination.

In this study, a gas chromatography-mass spectrometry (GC–MS) method was developed and validated for the simultaneous quantitation of sulfolane and BTEX in rock samples. To address the slow release of sulfolane observed in certain samples when left in methanol and to facilitate rapid analysis, a microwave-assisted extraction (MAE) method was optimized for sample preparation. Analysis of spiked samples yielded recoveries of 86 % to 115 % for the various analytes, with relative standard deviations of up to 7.9 %. The validated method was then applied to rock samples collected from a contaminated site in central Alberta, Canada. All analyzed samples were contaminated with toluene. Only one sample was found to be contaminated with sulfolane. Ethylbenzene, o-xylene, m/p-xylene and benzene were detected in 82 %, 44 %, 40 %, and 4 % of the samples, respectively. Although the concentrations of these contaminants were all below the Alberta Tier 1 Soil Remediation Guidelines, the sampling covered only a limited depth. Therefore, additional sampling and investigation are necessary to conclusively determine the status of persistent contamination at the site.