Simultaneous quantitation of morphine and paraben preservatives in morphine injectables

A high-performance liquid chromatographic method for the simultaneous determination of morphine sulfate, methylparaben, and propylparaben in morphine sulfate injection was developed. A reversed-phase system, based on an octadecylsilane stationary phase, was used with a binary solvent mobile phase consisting of methanol--phosphate buffer (pH 4.0) containing methanol (5%) delivered at a constant rate (0.6:0.4 ml/min) using a two-pump system. The detector response at 254 nm was linear with the amount injected over a wide range, allowing rapid and reproducible quantitation of each component.