Assay of Iodine Monochloride Via Iodination of 2‐chloroaniline Using Reversed‐phase Liquid Chromatography

Iodine monochloride is conventionally determined using the sodium thiosulphate titration method. Recently, mono-iodination of 2-chloroaniline in N,N-dimethylformamide has been reported in the presence of iodine monochloride. A reversed-phase high-performance liquid chromatography method for the assay of iodine monochloride on the C18 column has been developed via the iodination of 2-chloroaniline. Chromatographic separation was achieved using gradient elution with water and acetonitrile as mobile phase at 1 ml/min flow rate and detection at 304 nm. The elution of 2-chloro-4-iodoaniline was observed at 5.492 min. Under the given experimental conditions, an excess of 2-chloroaniline dissolved in acetonitrile reacted with a known amount of pure iodine monochloride resulting in 2-chloro-4-iodoaniline. The amount of 2-chloro-4-iodoaniline formed is a measure of the initial iodine monochloride concentration, thus providing the assay of iodine monochloride. The method was validated as per the guidelines of the International Conference on Harmonization guidelines and found to be linear (r(2) = 0.999) and accurate (98%-102%) for iodine monochloride concentrations ranging from 0.4 to 1.2 mg/ml. The intra-day and inter-day precision were within 1%. The validated method was successfully applied to determine the assay of commercially available iodine monochloride, Wijs solution, and in-situ generated iodine monochloride samples. Thus, a novel, simple, accurate, and precise HPLC method has been developed for iodination monochloride assay.