Ionic Liquid Cosolvents: An Effective Way To Analyze Chemical Spills In Shale Energy Basins

Over the past decade, scientists have scoured through shale energy basins across the United States to analyze and better understand the environmental implications of unconventional oil and gas development (UD). The growing body of research indicates that UD does not alter the environment in a systematic fashion, but rather on an episodic basis.

Nonetheless, numerous studies have characterized the occurrence of groundwater and surface contamination, observed instances of atmospheric insult, and chronicled the manifestation of hazardous surface spills. As the industry continues to evolve in the directions of better risk mitigation and greater environmental stewardship, so too have the analytical tools that can be utilized for characterizing aberrant contamination events.

Recently, our team developed a novel method for the characterization of BTEX compounds (benzene, toluene, ethylbenzene, and xylene isomers) in variable soil compositions using room temperature ionic liquids (RTILs) in headspace gas chromatography-mass spectrometry (HS-GCMS). This is significant given that BTEX is generally a strong indicator of contamination from hydrocarbon extraction, and the accuracy of BTEX analysis has traditionally been contingent upon soil composition. That is to say that by implementing the standardized methods established by the Environmental Protection Agency (EPA), the level of accuracy for quantifying BTEX would vary greatly depending on the proportion of sand, clay, and loam in any given sample.

Such an analytical limitation is particularly problematic when trying to rapidly assess the breadth of a soil contamination event across a highly variable landscape, as is often the case in shale energy basins. On the contrary, the use of RTIL cosolvent during headspace extraction circumvents this issue and affords analysts the ability to rapidly assess and quantify the presence of BTEX under a wide range of soil conditions.

Ultimately, this novel method for soil analysis allows for the use of a “universal” calibration curve, as RTILs were found to normalize the response for BTEX between the varying soil compositions investigated in the study. This saves time, as soil samples no longer need to be “matrix-matched” in order to calibrate the instrument. When applying this method to assess soils in areas associated with UD related activity, it was interesting to find quantifiable amounts of BTEX in a particular sample, which was comprised from soil obtained at a decommissioned produced water retention pond. This is of concern, as these compounds are being adsorbed by the soil, thus prolonging potential environmental and human exposure.

This study, ‘Matrix-effect-free determination of BTEX in variable soil compositions using room temperature ionic liquid co-solvents in static headspace gas chromatography mass spectrometry’ was published in the journal Analytica Chimica Acta.  The work was performed by researchers and affiliates with the Collaborative Laboratories for Environmental Analysis and Remediation at the University of Texas at Arlington.