Organic Impurities: Metformin Hydrochloride Buffer pH 3.5, Mobile phase, Dilute phosphoric acid, Diluent, Sample stock solution, Sample solution, and Chromatographic system: Proceed as directed in Assay, Procedure 2: Metformin Hydrochloride. Standard stock solution: Use the Standard solution prepared as directed in Assay, Procedure 2: Metformin Hydrochloride. Standard solution: 0.0002 mg/mL of USP Metformin Hydrochloride RS in Diluent from Standard stock solution Sensitivity solution: 0.0001 mg/mL of USP Metformin Hydrochloride RS in Diluent from the Standard solution