Assay and purity evaluation of 5-chlorooxindole by liquid chromatography

5-Chlorooxindole (5-CO) is a starting material for tenidap sodium, a pharmaceutical drug candidate produced by Pfizer. To insure potency and purity of the drug substance, it is necessary to demonstrate that commercial supplies of 5-CO are free from elevated levels of chemical analogs that could be carried through the synthetic scheme. This is accomplished using a single highly specific normal-phase chromatographic system that allows the quantitation of 5-CO concomitantly with all of its potential positional isomers. This paper describes the chromatographic system and its supportive validation data.