Microwave-Assisted Rapid Extraction of Chlorinated Solvents from Low Permeability Rock Samples

Rock matrices, as low-permeability media, play a critical role in controlling the persistence and fate of groundwater contaminants. Accurately quantifying contaminant mass stored in these matrices is therefore essential for understanding contamination transport processes. In this study, a microwave-assisted extraction (MAE) method was developed to accelerate the complete extraction of trichloroethylene (TCE) from rock samples. Because microwave–sample interactions depend on multiple factors, extraction conditions, including solvent type, temperature, and extraction time, were optimized using dolostone samples collected from industrial sites with decades-old contamination in Guelph, Canada. Method performance was evaluated through extensive comparison of the newly developed MAE procedure with a conventional shake-flask extraction method used as a reference. In addition, the necessity of field preservation was assessed, given its importance in the overall analytical workflow and accuracy of total mass concentrations and mass stored. The MAE method provided recoveries comparable to or greater than those obtained with the reference method, while avoiding several drawbacks of the shake-flask approach, such as sample cross-contamination during prolonged extraction times over several weeks. Its shorter processing time and faster turnaround support rapid, field-based decision-making. Field preservation was determined to be essential, as non-preserved samples consistently yielded lower measured concentrations than preserved samples.