Development of a Liquid Chromatography-Negative ESI-Tandem Mass Spectrometry Method for Ibuprofen with Minimization of Matrix Effects Associated with Phospholipids

Phospholipids are known to cause matrix ionization effects during LC/MS/MS analysis of biological samples. Matrix effects involving endogenous phospholipids in the negative ESI mode have been investigated in this work for the determination of ibuprofen in human plasma. Glycerophosphocholines (GPChos) and 2-lysoglycerophosphocholines (2-lyso GPChos) were monitored as markers for endogenous matrix components. Various extraction solvents were evaluated to assess their abilities to remove phospholipids from plasma samples to minimize matrix effects. Post-column infusion experiments were applied to chromatographically resolve matrix effects that resulted from endogenous phospholipids. The resulting method was validated and linearity was obtained over a concentration range of 50 to 10,000ng/mL.