An efficient hydrophilic interaction liquid chromatographic method for the simultaneous determination of metformin and pioglitazone using high-purity silica column

Hydrophilic interaction liquid chromatography (HILIC) provides a feasible approach to effectively separate polar compounds in complex matrices. Herein, a simple, reproducible and efficient HILIC method was developed for the simultaneous determination of pioglitazone. HCl (PIO) and metformin HCl (MET) in rabbit plasma. High-purity silica column was used for rapid and efficient separation of these co-administered drugs. The chromatographic parameters were optimized for best separation. The proposed HILIC system provides high separation efficiency with good peak shape compared to reversed phase (RP) chromatography. Additionally, a simple isocratic elution mode with a mobile phase composed of a mixture of methanol and 10 mM phosphate buffer (pH 3.0) (94:6, v/v) was used and the effluent was monitored at 230 nm. The method was validated in accordance with the requirements of US-FDA guidelines and was found to behave efficiently for the intended purpose. The correlation coefficient of 0.9992 was obtained in the concentration ranges of 0.5-100 μg mL−1. The limits of detection (S/N = 3) and quantification (S/N = 10) were 0.16 and 0.5 ng mL−1, respectively. The retention times were 3.4 and 5.0 min for PIO and MET, respectively. Plasma levels were successfully determined in rabbit with satisfactory precision and accuracy. In addition, the stability tests in rabbit plasma proved reliable stability under the experimental conditions. The developed HILIC method was applied successfully to study the pharmacokinetic behaviors of the studied analytes in rabbit plasma after a single oral dose containing PIO and MET.