Development of a Simple Isocratic HPLC-UV Method for the Simultaneous Analysis of Repaglinide and Metformin Hydrochloride in Nanoemulsion Formulations and Commercial Tablets

This study was aimed to develop and validate an HPLC-UV method for simultaneous analysis of metformin HCl (MET HCl) and repaglinide (REP) in nanoemulsion (NE) formulations and commercial tablets. MET HCl and REP-containing NE formulations (NE-1 and NE-2) were prepared. The droplet size and PDI values of NE formulations were found in the range of 100.631 +/- 0.504-173.356 +/- 2.432 nm and 0.128 +/- 0.005-0.227 +/- 0.004, respectively. Separation and analysis were performed on a C18 column (4.6 x 250 mm; 5 mu m) using a mobile phase including methanol:ethanol:ultrapure water mixture at pH adjusted to 3.0 with formic acid (30:40:30, v/v/v) and 242 nm was used for UV detection. The method is linear in a concentration range of 1 - 48 mu g/mL for both MET HCl and REP. The retention times of MET HCl and REP were found to be 2.1 and 8.2 min, respectively. The limits of detection (LOD) were 0.174 mu g/mL for MET HCl and 0.210 mu g/mL for REP. The limits of quantification (LOQ) were 0.526 mu g/mL for MET HCl and 0.637 mu g/mL for REP. The values of relative error and relative standard deviation (%) for both active substances were found to be lower than +/- 2% and 2%, respectively. This method was successfully applied for the simultaneous analysis of MET HCl and REP in NEs and commercial tablets.