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.