Two simple, accurate and reproducible methods have been developed for the
determination of repaglinide and metformin as bulk or simultaneously in their combined
dosage form. The first is a reversed phase HPLC method using C18 column, mobile
phase consisting of methanol-0.2% heptane sulphonate sodium (70:30 v/v) at a flow rate
of 1ml/min and UV detection at 240 nm. Beer's plot shows good correlations in the
concentration range of 1-10 μgml-1 for both drugs. The second method is a derivative
spectrophotometry, in which the two drugs were quantified using second derivative
responses at 287 nm for repaglinide and at 234 or 252 nm for metformin with a linearity
range of 5- 40 or 2-12 μgml-1 for the two drugs, respectively. The proposed methods were
validated and successfully applied to the determination of both drugs in their
pharmaceutical formulation with mean recoveries of 99.58-100.45 ± 0.386-0.931. The
results obtained were statistically compared to those obtained from a reference method
and were found to be in good agreement.
