Simultaneous determination of lidocaine hydrochloride, hydrocortisone and nystatin in a pharmaceutical preparation by RP-LC

A liquid chromatographic (LC) method was developed to analyze a formulation (mouthwash) containing lidocaine hydrochloride, hydrocortisone and nystatin. A single LC method with UV detection was developed. A Waters Symmetry C18 HPLC column (150 mm ×  4.6 mm, 5 μm) was used as stationary phase and the assay was performed with gradient elution using mobile phases containing methanol - 0.1 M NaH2PO4 with a pH that was previously adjusted to 4.5 with dilute phosphoric acid. The sample pretreatment was performed by treating the formulation with methanol followed by filtration. After method development, the influence of the different chromatographic parameters on the separation, the interference of other active compounds and excipients, linearity, accuracy, repeatability and intermediate precision were investigated. The method was shown to be selective, linear, accurate, precise and repeatable. Finally, the content of the compounds in the formulation was determined.