Optimization of a solid phase extraction and hydrophilic interaction liquid chromatography-tandem mass spectrometry method for the determination of metformin in dietary supplements and herbal medicines

► An analytical method based on HILIC-MS/MS for determination of metformin was developed. ► PCX and PSA were used as extraction/clean-up adsorbent to increase the efficiency of the extraction. ► The two-step extraction process was successfully applied to the clean-up dietary supplements and herbal medicines.