Simultaneous Estimation of Metformin HCl and Sitagliptin Phosphate in Tablet Dosage Forms by RP-HPLC.

A simple, precise, rapid and accurate reverse phase HPLC method was developed for the estimation of Metformin HCl and Sitagliptin PO₄ in tablet dosage forms. An Xterra C18, 250x4.6 mm, column with 5 μm particle size and the mobile phase consisting of 0.03M K₂HPO₄ in water pH-3.2 adjusted with o-Phosphoric Acid: Acetonitrile in the gradient mode was used. The flow rate was 1.0 ml/min and the effluents were monitored at 207 nm. The retention times were 2.510 min for Metformin HCl and 7.673 min for Sitagliptin PO₄. The detector response was linear in the concentration of 14–168 mcg/mL for Metformin HCl and 1.3–15.6 mcg/mL for Sitagliptin PO₄. The respective linear regression equation being Y= 48822.5x+10329 for Sitagliptin PO₄ and Y= 70435x+238894 for Metformin HCl. The Limit of Detection (LOD) is 0.13 mcg and 0.14 mcg for Sitagliptin PO₄ and Metformin HCl respectively. The Limit of Quantification (LOQ) is 0.39 mcg for Sitagliptin PO₄ and 0.42 mcg for Metformin HCl. The percentage assay of Metformin HCl and Sitagliptin PO₄ was 99.46% and 99.19% respectively. The method was validated by determining its accuracy, precision and system suitability. The results of the study showed that the proposed RP-HPLC method is simple, rapid, precise and accurate, which is useful for the routine determination of Metformin HCl and Sitagliptin PO₄ in bulk drug and in its pharmaceutical dosage forms.