Simple HPLC-UV method for the quantification of metformin in human plasma with one step protein precipitation

This study presents the optimization of a simple HPLC-UV method for the determination of metformin in human plasma. Ion pair separation followed by UV detection was performed on deproteinized human plasma samples. The separation was carried out on a Discovery Reversed Phase C-18 column (250 × 4.6 mm, 5 μm) with UV detection at 233 nm. The mobile phase contained 34% acetonitrile and 66% aqueous phase. Aqueous phase contained 10 mM KH2PO4 and 10 mM sodium lauryl sulfate. Aqueous phase pH was adjusted to 5.2. The mobile phase was run isocratically. The flow rate of the mobile phase was maintained at 1.3 ml/min. The linearity of the calibration curve was obtained in the concentration range of 0.125–2.5 μg/ml and coefficient of determination (R2) was found to be 0.9951. The lowest limit of quantification and detection was 125 and 62 ng/ml respectively. No endogenous substances were found to interfere with the peaks of drug and internal standard. The intra-day and inter-day coefficient of variations was 6.97% or less for all the selected concentrations. The relative errors at all the studied concentrations were 5.60% or less. This method is time efficient and samples are easy to prepare with minimum dilution. So, it can be applied for monitoring metformin in human plasma.