Exploration of matrix effect. In LC-MS analyses, post-column infusion of analytes-of-interest while injecting a matrix sample is a common procedure to get insight in how and when the analytes are affected by matrix effect . To assess the potential of PCIS correction for a given LC-MS method, it is useful to start by infusing a mix of analytes-of-interest and exploring the infusion profiles. Even though PCIS correction can in general be helpful to correct for any unexpected sources of matrix effect, it will be particularly useful for methods with analytes eluting in known high-suppression zones. Next to providing information on the extent of matrix effect, we propose using the infusion experiment data to estimate the number of different PCISs necessary to correct for the complete set of analytes. It is known that an analyte might be more or less prone to matrix effect depending on its ionization energy and proton affinity . Also other (physicochemical) properties have been reported in models predicting ionization efficiencies .