What is the role of post-column infusion in evaluating matrix effects?

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Post-column infusion tests how matrix components affect ionization in LC-MS by watching the analyte signal as the sample elutes. In the setup, you infuse a constant amount of the analyte (or a standard solution) into the mass spectrometer after the LC column while running a matrix sample. If substances in the matrix co-elute with the analyte, they can suppress or enhance ionization, causing the signal to dip or spike at those retention times. This visual map shows where and how strongly matrix effects occur, guiding adjustments to sample prep, chromatography, or the use of internal standards to compensate. It isn’t about replacing calibration standards, changing instrument temperature, or measuring retention time.