Development of Methodology to Determine Benzalkonium Chloride in Tear Fluid

Benzalkonium chloride is used as a biocide preservative in majority of multidose eye drop formulations. Due to its detergent nature this compound can have deleterious consequences to eye tissues, including conditions such as dry eye syndrome or worsening of glaucoma. Complex and unpredictable pharmacokinetics and toxicology among other factors lead to absence of universally and routinely applied method to determine this substance in the eye. In this study we seeked to create the validation criteria meeting method to determine benzalkonium chloride in live subjects‘ tear fluid, comprising specimen collection by Schirmer‘s test strips, transfer of analyte to sample using extraction with organic solvents, and ultra-high performance liquid chromatography – tandem mass spectrometry sample analysis. Methodology development results indicated reliable analyte extraction efficiency, rapidness of analysis, good precision, and suitable linearity for clinically relevant concentration range. However, some drawbacks were highlighted as well, such as analyte overlapping signal generation which in turn compromises the identification of analyte detection and quantification limits. In addition, clinical benefits of the method are elusive as no significant relationship between known concentrations of benzalkonium chloride in eye drops taken by patients and those determined in respective tear fluid samples was found. In conclusion, the developed method needs more thorough validation and further research for clinical applicability