A composite consisting of sulfo-functionalized magnetic graphene and mesoporous silica for extraction of metformin and glimepiride prior to their determination by liquid chromatography tandem mass spectrometry

A new sorbent was synthesized for restricted-access matrix solid phase extraction (RAM-SPE) of the diabetes drugs metformin (MET) and glimepiride (Glim). Mesoporous silica layers were placed on Fe 3 O 4 -magnetized graphene modified with sulfo-functionalized pore walls (denoted as magG@mSiO 2 -SO 3 H composites). The composites have a large specific surface (173 m 2 ·g −1 ), appropriate pore sizes (typically 3.7 nm), and sulfo-functionalized pore walls. Magnetic separation can be accomplished within 10 s. The unique properties of the composites allow both MET and Glim to be selectively and quickly extracted from plasma sample. Following magnetic separation and elution by 50% aqueous acetonitrile with 4% ammonium solution, the two drugs were quantified by LC-MS/MS analysis. The assay has high selectivity, good linearity (2.5–4000 ng•mL −1 for MET and 0.02–1600 ng•mL −1 for Glim), a low detection limit (as low as 60 pg•mL −1 for MET and 1 pg•mL −1 for Glim), excellent recovery (above 92.2%), and good precision (RSDs