Chemical constituents and analytical approaches for hydraulic fracturing waters

Hydraulic fracturing fluids contain a mix of organic and inorganic additives in an aqueous media. The compositions of these mixtures vary according to the region or company use, thus making the process of identifying individual compounds difficult. The analytical characterization of such mixtures is important in order to understand the transport, environmental fate and ultimate potential health impact in various water compartments associated with hydraulic fracturing. Organic compound classes include solvents, gels, biocides, scale inhibitors, friction reducers, surfactants and other related compounds. These contaminants are usually present in trace amounts, so sophisticated analytical methodologies are needed in order to fully characterize the chemical composition of fracking fluids. The current state of knowledge of chemical components and approaches for their analysis is reviewed here. In recent years, modern analytical methodologies, such as gas chromatography–mass spectrometry (GC–MS) have been specifically used to identify organic chemical components of fracking fluids and/or flowback and produced waters associated with the process of hydraulic fracturing. Other techniques such as liquid chromatography–mass spectrometry (LC–MS) have not been explored in detail yet. In this review a detailed description of chemical constituents present in hydraulic fracturing waters will be given, as well as an evaluation of the analytical techniques used for their unequivocal determination.