Objective: The aim of this study was to develop a simple, rapid, efficient, cost effective and reproducible, stability indicating reverse phase high performance liquid chromatography method (RP-HPLC) for dosage of metformin in human plasma and erythrocytes.
Methods: In this method, the plasma or erythrocyte proteins were precipitated using Perchloric acid: acetonitrile (50 % v/v) mixture and the supernatant liquid were injected into the HPLC system. The separation was achieved with a symmetry C8 column with the mobile phase containing 10 % water and 90 % sodium dihydrogen phosphate buffer (5.8 mM), the pH was adjusted to 3.8 with Phosphoric acid. The temperature was elevated to 25 °C. The detection was done by a UV detector at 232 nm.
Results: The retention time was observed at around 4.412 min for metformin and 6.022 for lansoprazole an internal standard (IS). The response was linear over a range of 2-32µg ml-1, the coefficient of determination (r²) was found to be (r² =0. 9988). The lowest limit of quantification and detection was 0.1 µg/ml and 0.3 µg/ml respectively. No endogenous substances were found to interfere with the peaks of the drug. The intra-day and inter-day coefficient of variations was 2.1 % or less for all the selected concentrations. The relative errors at all the studied concentrations were 3.5 % or less.
Conclusion: The HPLC method described in this article was simple, selective, reproducible, linear, and precise, it can be applied for therapeutic drug monitoring of metformin in human plasma and erythrocytes
