Zeitschrift für antimikrobielle Wirkstoffe

A Rapid, High-Throughput Iodometric Titration Method for the Determination of Active Chlorine Content of Topical Antiseptic Solutions

Abstract

Mangum LC, Garcia GR, Niece KL, Wenke JC and Akers KS

Objective: A considerable number of commercially available topical antiseptic solutions rely on free available chlorine as an active ingredient due to its broad-spectrum antimicrobial activity, but limited empirical knowledge exists of the degradation kinetics of chlorine-based solutions in contact with host tissue. To better inform clinical practice, we developed and qualified a rapid and sensitive semi-automated microtiter plate-based iodometric titration assay suitable for the rapid determination of free available chlorine in small samples of dilute antiseptic solutions following contact with biological materials.
Methods: The chlorine determination method described here utilizes a novel stepwise iodometric titration approach performed entirely on a plate reader spectrophotometer equipped with a standard automatic syringe dispenser module. In this method, both titrant addition and colorimetric monitoring steps are carried out automatically, providing significantly higher sample throughput with reduced technical error when compared to the manual titration approach typically used for this type of analysis. Assay qualification was performed by measuring free available chlorine in commercial Dakin’s solution at a range of concentrations during contact with human plasma n vitro and rat muscle tissue in a simulated wound model (ex vivo).
Results: The practical lower limit of quantitation for a 200 μl sample using this assay was found to be approximately 0.001% mass available chlorine and agreement was excellent between measured and nominal percent mass available chlorine over the range concentrations tested. Contact with biological material was found to cause loss of reactive chlorine in Dakin’s solution in seconds to minutes.
Conclusion: The semi-automated available chlorine determination method described here represents numerous improvements to traditional iodometric titration approaches by substantially decreasing required sample volume, drastically increasing throughput, and minimizing manual sample handling and error. We feel this novel method will be of value to other researchers investigating the degradation kinetics of chlorine-based solutions to improve clinical practice.