RP – HPLC Simultaneous Estimation of Diclofenac Diethylamine and Lidocaine in Pharmaceutical Gel Formulation

A new specific, precise, accurate and robust RP-HPLC method has been developed for the simultaneous determination of Lidocaine and Diclofenac Diethylamine in a pharmaceutical gel formulation. The chromatographic separation was carried out at Jasco HPLC system consisting of Jasco PU 2075 pump having browin software.The stationary phase was PrincetonSPHER 100 C18 column (250mm X 4.6mm, 5μ).The mobile phase was Acetonitrile: Potassium dihydrogen phosphate (0.01M): Butane sulfonic acid sodium salt (45:55:0.1%), and adjust to pH 6.8± 0.05 with triethylamine. Detection was carried out at 261nm using Jasco UV 2075. The flow rate was 1.0ml/min and retention time was about 5.7min and 14.025min.for Diclofenac Diethylamine and Lidocaine respectively. The linearity was obtained in the concentration range of 20-300ug/ml and 50-500ug/ml for Lidocaine and Diclofenac Diethylamine respectively. Mean percentage recoveries were 99.84% for Lidocaine and 99.78% for Diclofenac Diethylamine. The LOD of Lidocaine and Diclofenac Diethylamine was found to be 20 μg/ml and 12.0 μg/ml whereas the LOQ was 35 μg/ml and 60 μg/ml respectively. The assay values of both the analytes was found to be well within the limits that is 101.5% and 98.25% for Lidocaine and diclofenac Diethylamine respectively. Percentage relative standard deviation of percent assay values for replicate sample preparation was 1.11% for Lidocaine and 0.95% for Diclofenac Diethylamine .The method was robust with respect to change in flow rate, and composition of mobile phase.