Determination of trace levels of oxytocin in pharmaceutical solutions by high-performance liquid chromatography

A high-performance liquid chromatographic assay has been developed for quantitating oxytocin in common large volume parenteral intravenous solution matrices. Separation is accomplished by a reversed-phase mechanism using a C18 column. The analyte is detected fluorimetrically after post-column derivatization with fluorescamine. Reaction efficiency is controlled by the use of a reaction buffer which is added separately from the fluorescamine via a dual pump reactor system. Given the low analyte concentration [40 parts per billion (10(9)) or less], the samples are concentrated on-line through the use of a trapping column and switching valve. To improve productivity, pre-concentration and analysis of adjacent samples is timed to occur concurrently. Performance of the assay is characterized by a high degree of accuracy, precision and ruggedness; the system is capable of distinguishing between the analyte, matrix components, impurities and common degradates.