An ion chromatographic method with conductivity detection for the precise and accurate analysis of lithium ions in phosphate-buffered saline, used as a cervicovaginal lavage (CVL) fluid, was developed and validated. The lithium ion dilution factor during the CVL is used to calculate the volume of cervicovaginal fluid (CVF) collected. Initial CVL Li(+) concentrations of 1mM and 10mM were evaluated. The method is robust, practical, and afforded an accurate measurement (5% of the measurement, or better) at 24μL of vaginal fluid simulant collected per mL of CVL fluid, as low as 5μLmL(-1) using 10mM Li(+) with a measurement accuracy of 6.7%. Ion chromatograms of real-world CVL samples collected in vivo from common animal models (sheep and pig-tailed macaque) and a human volunteer demonstrate that the analysis is interference-free. The method is readily transferrable and should enable the accurate measurement of CVF volume collected during CVLs benefitting a broad range of research disciplines, including pharmacokinetic, pharmacodynamic, metabolomic, and microbiome studies.
Keywords: Cervicovaginal fluid dilution; Cervicovaginal lavage; Ion chromatography; Lithium.
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