Facile HPLC/UV method for determination of metformin and 1-cyanoguanidine using novel halogenated stationary phase

Metformin is the most prescribed drug for diabetes. We aimed to develop a new HPLC method for determination of metformin and its main impurity 1-cyanoguanidine in raw material and its pharmaceutical tablets. The separation was achieved on pentabromobenzyl column using a mixture of 20% 10.0 mM phosphate buffer (pH 5.5) and 80% methanol as a mobile phase at a flow rate of 1.0 mL min-1 and UV detection at 227 nm. The analysis time was less than 4.0 minutes. The method was linear through concentration ranges of 3.0 – 80 µg mL-1 and 0.5 – 10 µg mL-1 and detection limits of 0.73 µg mL-1 and 0.11 µg mL-1 for metformin and 1-cyanoguanidine, respectively. The method was successfully applied for determination of metformin in bulk and pharmaceutical dosage forms. The high sensitivity of the developed method allowed for determination of 1-cyanoguanidine below its specified limits in metformin raw material and tablets.