Determination of Clinically Very Basic Compounds by Nanoscale Liquid Chromatography with Tandem Mass Spectrometry

A simple nanoscale liquid chromatographic method with tandem mass spectrometry (LC‐MS‐MS) was developed for the determination of very basic compounds, biguanides, such as metformin and phenformin. Plasma samples were deproteinated and acidified with heptafluorobutyric acid (HFBA) and the resulting supernatant injected into the nanoscale separation system. Chromatography was carried out using a short reversed‐phase C18 column under isocratic elution with methanol‐40 mM aqueous HFBA (75∶25, v/v) at a flow rate of 800 nL/min. Therapeutic monitoring on metformin and phenformin to minimize adverse side effects is important. The main advantage of the nanoscale method is the lower consumption of organic solvent. This nanoscale method is suitable for the investigation and monitoring of the concentration of oral antihyperglycemic drugs in clinical patients.