Quaternary ammonium compounds (QACs) are a diverse group of organic chemicals with molecular masses ranging from 100 to 600 g/mol and alkyl side-chains of 2 to 20 C atoms. Consequently, the physicochemical properties of compounds within this group are highly variable, particularly with respect to their hydrophobicity and water solubility. The large variation in hydrophobicity as well as their permanent positive charge make this group of compounds challenging to analyze by liquid chromatography coupled to mass spectrometry (LC-MS). Given the abundant use of QACs as solvents, herbicides, surfactants, and disinfectants, a sensitive and robust method to detect these compounds in the environment is important. The majority of QACs are released into the environment through wastewater effluents due to their use in personal care products (fabric softeners, soaps, hair products) and as emerging solvents in the chemical industry. While hydrophobic QACs with long side-chains (10 to 20 C atoms) adsorb strongly to sewage sludge and sediments, short-chained (2 to 10 C atom) QACs are likely to remain in the water phase. We developed a method for the quantification and identification of QACs with alkyl side-chains of 2 to 18 C atoms in water samples by high resolution and accurate mass (HRAM) on an Orbitrap mass spectrometer. Optimal retention, good peak-shapes, and minimal carry-over was achieved for 25 QACs with nano-flow, hydrophilic interaction liquid chromatography (HILIC). The 25 QAC standards could be quantified based on their accurate mass down to injected amounts of 1-20 pg. With a sample preparation procedure including solid-phase extraction onto a mixed-mode sorbent material, quantification limits for QACs in 100 mL water samples were in the low ng/L range. Currently, this method is feasible for quantifying 25 QACs as well as for suspect-screening of other QACs in surface water and wastewater effluent samples. Furthermore, we are in the process of developing a sample preparation procedure for sediment samples, which will be used to screen for past usage of long-chained QACs in Minnesota.

Quantification and suspect-screening of hydrophobic and hydrophilic quaternary ammonium compounds in water samples by LC-HRAM-MS/MS

255th National Meeting (2018)

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