Volatile organic compound (VOC) emissions from the usage of benzalkonium chloride and other disinfectants based on quaternary ammonium compounds

Quaternary ammonium compounds (QACs) are a class of molecules commonly used as residential and industrial disinfectants whose prevalence has increased in recent years and during the COVID pandemic. QACs are typically considered relatively inert and nonvolatile; however, little is known about the propensity of QAC commercial products (CPs) to emit volatile organic compounds (VOCs) during usage. We performed a series of environmental chamber and solution headspace measurements using a Vocus proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) to examine VOC emissions during simulated spraying of a dilute solution of pure benzalkonium chloride (BAC), several CPs whose primary active ingredients include BAC and didecyl dimethyl ammonium chloride (DDAC), and a CP containing a novel silyl-based QAC. A number of VOCs were observed during spraying of pure BAC solution, including functionalized benzyl compounds, chlorotoluenes, and small functionalized hydrocarbons; these VOCs may be derived from the BAC synthesis process. Similar emission signatures were also detected from CPs, though specific source attribution was challenging due to the chemical complexity of commercial formulations, which include molecules to aid in solubilizing and stabilizing QACs (among other roles). Headspace measurements of the silyl-QAC suggest a functionalized propyl-silyl molecule is volatilized whose exact origin and structure could not be determined. Functionalized benzyl compounds are detected at the C₇H₇⁺ ion as well as at the protonated [M]H⁺ species or other ions, providing insight into the structures that can give rise to the C₇H₇⁺ ion signature that has commonly been detected during PTR-ToF measurements of indoor and urban environments. Within the pure BAC solution, the identified benzyl molecules may not account for the entirety of the measured C₇H₇⁺ signal, leaving open the possibility that unidentified VOCs are also present. Overall, the present measurements show that QAC solutions are not inherently inert or nonvolatile and will emit a variety of VOCs depending on the identity and purity of the contained QACs and product formulation.