A chromatographic approach to avoid the matrix effect caused by sodium acetate clusters in the liquid chromatography coupled with electrospray ionization mass spectrometry analysis of free fatty acids in human plasma

Liquid chromatography coupled with electrospray ionization mass spectrometry (LC-ESI-MS) is widely used for the analysis of biological samples in pharmacokinetic studies, clinical diagnostics, and therapeutic drug monitoring. However, matrix effects caused by coexisting substances in samples often compromise analytical sensitivity and accuracy. Our study showed that sodium acetate clusters, formed from sodium ions in human plasma and acetate ions in mobile phase, interfered with the detection of free fatty acids (FFAs) in a reversed-phase (RP) LC-ESI-MS analysis. To address this issue, we employed a trimodal column (reversed-phase/weak anion-exchange/weak cation-exchange), which effectively separates the sodium ions from FFAs and successfully reduces the matrix effects. Owing to its high compatibility with conventional octadecylsilyl (ODS) bonded column, enabling easy implementation into existing ODS-based methods, the trimodal column offers a promising new chromatographic strategy for mitigating matrix effect caused by sodium acetate clusters in RPLC-ESI-MS bioanalysis.