Extraction-Spectrophotometric Determination of Lidocaine Hydrochloride in Pharmaceuticals

Simple, selective and highly detectable spectrophotometric method has been developed and validated for the determination of Lidocaine hydrochloride in standard and commercial solutions .The method is based on the formation of a soluble colored Lidocaine hydrochloride-eriochrome black T ion-pair complex at pH 1.80. The colored complex was extracted quantitatively into chloroform and measured at 508 nm. Beer’s law was obeyed in the concentration range of 0.10-10 mg L -1 with molar absorptivity of 2.3623 x104 L mol-1 cm-1.The limits of detection and quantification were 0.024 mg L -1, and 0.100 mg L -1 respectively. Using Job’s continuous variations method, the stoichiometry of the ion-pair complex was found to be 1-1. Intra-day accuracy and precision of the method were estimated with a relative error (0.57%), and the relative standard deviation (0.25-1.23). This developed method has been successfully employed to determine concentration of Lidocaine hydrochloride in injection and spray without interference by the common co-formulated substances.The numerical results obtained using both proposed and official methods were in concordance with each other.