Identification of Proprietary Amino Ethoxylates in Hydraulic Fracturing Wastewater Using Liquid Chromatography/Time-of-Flight Mass Spectrometry with Solid-Phase Extraction

This work describes the discovery of amino-poly(ethylene glycol)s, amino-poly(ethylene glycol) carboxylates, and amino-poly(ethylene glycol) amines in 20 produced water samples from hydraulic fracturing in the western United States. These compounds, with masses in the range of m/ z 120-986, were identified using solid-phase extraction and liquid chromatography/quadrupole time-of-flight mass spectrometry. The polymeric sorbent, Oasis HLB, gave good recovery for all three ethoxylated surfactants and desalted the samples, which significantly reduced suppression of the mass spectral signal allowing detection and identification. The Kendrick mass defect, mass spectra, fragmentation pathways, and pure standards were used for confirmation. Finally, because these compounds are not explicitly listed in FracFocus reports, rather they are categorized as a proprietary surfactant blend; their identification is an important step in understanding the chemistry, treatment, and possible toxicity of hydraulic fracturing wastewater.