A simultaneous determination method for 5‐fluorouracil and its metabolites in human plasma with linear range adjusted by in‐source collision‐induced dissociation using hydrophilic interaction liquid chromatography–electrospray ionization–tandem mass spectrometry

We applied a new technique for quantitative linear range shift using in‐source collision‐induced dissociation (CID) to complex biological fluids to demonstrate its utility. The technique was used in a simultaneous quantitative determination method of 5‐fluorouracil (5‐FU), an anticancer drug for various solid tumors, and its metabolites in human plasma by liquid chromatography–electrospray ionization–tandem mass spectrometry (LC/ESI‐MS/MS). To control adverse effects after administration of 5‐FU, it is important to monitor the plasma concentration of 5‐FU and its metabolites; however, no simultaneous determination method has yet been reported because of vastly different physical and chemical properties of compounds. We developed a new analytical method for simultaneously determining 5‐FU and its metabolites in human plasma by LC/ESI‐MS/MS coupled with the technique for quantitative linear range shift using in‐source CID. Hydrophilic interaction liquid chromatography using a stationary phase with zwitterionic functional groups, phosphorylcholine, was suitable for separation of 5‐FU from its nucleoside and interfering endogenous materials. The addition of glycerin into acetonitrile‐rich eluent after LC separation improved the ESI‐MS response of high polar analytes. Based on the validation results, linear range shifts by in‐source CID is the reliable technique even with complex biological samples such as plasma. Copyright © 2016 John Wiley & Sons Ltd.