Technical note | Determination of Benzalkonium Chloride in Commercial Disinfectant Formulations by Quantitative NMR Spectroscopy

Abstract

A biofouling treatment protocol for Royal Australian Navy vessels involves dosing with commercial disinfectant solutions containing the biocide benzalkonium chloride (BAC). In this work a single pulse proton Nuclear Magnetic Resonance (NMR) spectroscopic method was developed in order to permit the determination of BAC content in commercial formulations without suppression of the water resonance. The formulations were directly aliquoted into a NMR tube into which a stem coaxial insert, containing a reference solution of dimethylsulfone in deuterated lock solvent, was added. The samples were not filtered, diluted or concentrated and were quantified by comparison to a linear regression curve prepared from a commercially available standard. Eight samples from two commercial formulations were analysed with total BAC content determined to be 39-43 g/L for the Conquest® formulations and 40-60 g/L for the Quatsan® formulations.

Executive Summary

A biofouling treatment protocol for Royal Australian Navy vessels involves dosing with commercial disinfectant solutions containing benzalkonium chloride (BAC); a molluscicide and antifouling chemical. In order to determine the efficacy of this treatment protocol, it is necessary to determine the concentration of BAC in each treatment solution. Conventional methods for BAC quantitation utilise liquid or gas chromatography. Whilst highly sensitive, these techniques require significant sample preparation such as filtration, solvent extraction, derivatisation and dilution. Nuclear Magnetic Resonance (NMR) spectroscopy is an alternative technique for the analysis of such samples, often without the requirement for solvent extraction, dilution or filtration. In this work, proton NMR spectroscopy was used to quantitate BAC content in commercial disinfectant formulations without suppression of the water resonance. The formulations were directly aliquoted into an NMR tube into which a stem coaxial insert, containing a reference solution of dimethylsulfone in D2O, was added. The samples were not filtered, diluted or concentrated and were quantified by comparison to a linear regression curve prepared using a commercially available BAC standard. Eight samples from two commercial formulations were analysed with total BAC content determined to be 39-43 g/L for the Conquest® formulations and 40-60 g/L for the Quatsan® formulations. The methods and results presented herein will be used in a separate study to assess the efficacy of BACs as antifouling agents under realistic field conditions.