Simultaneous quantification of released succinic acid and a weakly basic drug compound in dissolution media

A HPLC-method was developed to determine both fenoldopam, a weakly basic drug and succinic acid, a pH-adjuster for this drug in dissolution media. The usual assays for succinic acid were not applicable due to its low UV-absorption, the low pH-value of samples or the presence of buffer salts and fenoldopam. The described method is a simple non-ion-pair reversed phase HPLC-method using a fast scanning UV-detector and a PC software program for the quantification of both components. Succinic acid is detected at 205 nm and fenoldopam at 225 nm. The UV-spectrum is used to determine peak purity and to identify peaks (carried out at a 99.9% match). This is especially important as in some of the investigated samples an unknown peak elutes immediately after succinic acid, resulting in spurious high contents, if mistaken for succinic acid. The simple method accomplished the simultaneous quantification of both, succinic acid and fenoldopam, by an accurate, precise, specific and reproducible assay, with a linear range covering all concentrations relevant for dissolution testing. The method is stability indicating and can also be used for the quantification of fumaric acid, another pH-adjuster in dissolution media together with fenoldopam.