Iodometry

Abstract: 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.

Abstract: A rapid and simple method by high performance liquid chromatography (HPLC) was studied for the determination of thioglycolic acid (TGA) and dithiodiglycolic acid (DTDGA) in hair-waving solutions. A reverse phase ODS-silica was used as a column, and the eluent was 15% methanol adjusted to pH 2.0 with phosphoric acid. Chromatograms were monitered at UV 220 nm. DTDGA showed a single peak when the eluent pH was below 2.0. Sample solutions were prepared by a simple procedure, direct dilution with water. By using model samples containing 2, 5 and 7% of TGA, the proposed (HPLC) method was compared with iodometric determination. TGA data by HPLC method agreed with iodometric data, and the recoveries of DTDGA spiked to a model sample at the level of 0.5-3.0% were 102-106% by HPLC method, but 40-90% by iodometry.

Abstract: Two simple, rapid and reliable methods are described for the determination of captopril in pharmaceutical preparations using chloramine-T as the oxidimetric reagent In the titrimetric method, 1-12 mg of the sample are treated with a measured excess of chloramine-T in hydrochloric acid medium, followed by the determination of the residual oxidant by iodometry The reaction follows 1:3 stoichiometry The limit of detection and quantification were found to be 028 and 094 mg, respectively The spectrophotometric procedure is also based on the redox reaction with a known excess of chloramine-T in hydrochloric acid medium However, here the unreacted chloramine-T is determined by reacting with indigocarmine and measuring the absorbance at 610 nm The absorbance is found to increase linearly with the increasing concentration of captopril, which is corroborated by the calculated correlation coefficient value of 09942 The system obeys Beer's law for 0-50 μg quantities of captopril in an overall volume of 10 ml The molar absorptivity and the Sandell sensitivity were calculated to be 237×10 4 lmol - 1 cm - 1 and 918 ngcm - 2 , respectively The limits of detection and determination were found to be 0068 and 0230 μgml - 1 , respectively The methods were applied successfully to the determination of captopril in tablets The reliability of the assay methods was established by parallel determinations by the official iodometric method and recovery studies