Determination of Three Benzalkonium Chloride Homologues in Environmental Water by Ultra High Performance Liquid Chromatography- Quadrupole/Electrostatic Field Orbitrap High Resolution Mass Spectrometry

Benzalkonium chloride has a non-oxidizing bactericidal effect and is widely used in medical and health service. With the discharge of sewage into the environment, benzalkonium chloride has been identified as a harmful compound that may seriously inspect susceptible organisms in the ecosystem. Exact quantitative analysis of benzalkonium chloride in environmental water is of great significance for human and ecological environmental health. However, low content of benzalkonium chloride exist in environmental water. The interference of a complex matrix causes false positive results to occur easily. Therefore, the detection method is required to have lower detection limits and more accurate qualitative analysis ability.

To establish a method for the determination of three benzalkonium chloride homologues (n-C₁₂H₂₅-C₉H₁₃NCl, n-C₁₄H₂₉-C₉H₁₃NCl, n-C₁₆H₃₃-C₉H₁₃NCl) in environmental water.

Ultra-high performance liquid chromatography quadrupole/electrostatic field orbitrap high resolution mass spectrometry (UPLC-Q-Orbitrap HRMS) was used. The sample was filtered through a 0.22μm membrane, and then mixed with the same volume of methanol. The mobile phase consisted of 10mmol/L ammonium acetate aqueous solution which contained 1% (V/V) triethylamine as mobile phase B and methanol as phase A, with gradient elution. Accucore C18 column (150mm×2.1mm, 2.6μm) was used to separate the baseline of three benzalkonium chloride within 6 minutes, and the data were collected by electrostatic field orbitrap mass spectrometry in SIM mode at 60, 000 resolution.

The contents of three benzalkonium chloride within the range of 0.10-10.0μg/L had a linear relationship (r>0.999). The detection limits ranged from 0.03 to 0.06μg/L. The recoveries of three kinds of benzalkonium chloride were 86.7%-111.2%.

Verified by samples, this method meets the detection limits and has anti-interference abilities of three benzalkonium chloride homologues in surface water and shallow groundwater. Moreover, it was identified that the suspected disrupting chemical of cetyl dimethyl benzyl ammonium chloride is propylene glycol fatty acid ester at m/z 360.323.