Simultaneous determination of free and total choline and l-carnitine in infant formula using hydrophilic interaction liquid chromatography with tandem mass spectrometry.

A quick, simple, and reliable method was developed for the simultaneous determination of free and total choline and l-carnitine in infant formula employing a novel hydrophilic interaction liquid chromatography with tandem mass spectrometry method. Microwave-assisted hydrolysis was used to shorten the hydrolysis time to only 15 min. A novel Click XIon zwitterionic stationary phase was chosen because it gave better retention, perfect resolution, and sharper symmetrical peaks compared to traditional columns. The matrix effect under different experimental conditions was evaluated by using the matrix effect factor, which employs stable isotopically labeled internal standards and is more appropriate for evaluating the matrix effect related to endogenous analytes. The accuracy and precision of the method were validated with certified reference materials. The fortified recovery values for choline and l-carnitine were between 85.0 and 104% with relevant standard deviations <5.0%. The established method was applied to the analysis of real infant formulas, demonstrating its applicability and feasibility.