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 determina-tion of metformin in human plasma. Ion pair separation followed by UV detection was performedon deproteinized human plasma samples. The separation was carried out on a Discovery ReversedPhase C-18 column (250·4.6 mm, 5lm) with UV detection at 233 nm. The mobile phase contained34% acetonitrile and 66% aqueous phase. Aqueous phase contained 10 mM KH2PO4and 10 mMsodium lauryl sulfate. Aqueous phase pH was adjusted to 5.2. The mobile phase was run isocrati-cally. The flow rate of the mobile phase was maintained at 1.3 ml/min. The linearity of the calibra-tion curve was obtained in the concentration range of 0.125–2.5lg/ml and coefficient ofdetermination (R^2) was found to be 0.9951. The lowest limit of quantification and detection was125 and 62 ng/ml respectively. No endogenous substances were found to interfere with the peaksof 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 were5.60% 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.