Impact of ion suppression by sample cap liners in lipidomics.

Contamination from the polymeric material released by vial caps used for sample introduction in liquid chromatography can significantly affect the signal of the analyte of interest. In particular, repeated injections from the same sample vial can enhance this suppressing effect. Multiple injections of the same sample are often used in metabolomics and lipidomics during routine analyses. Here we demonstrate how the presence of contaminant polymers, originating from the vial closures, significantly influences the estimation of the relative amount of endogenous lipids in human plasma. Furthermore, this can negatively impact other operations in mass spectrometric analysis, such as instrument equilibration and tuning or the common use of technical replicates to improve confidence in data interpretation. Our observations provide critical information on how to improve future analyses through the use of appropriate vial caps, solvents, chromatographic separations and equipment.