Before testing this, it is important to consider the limitations of PCIS. If working well, it can correct for matrix effect during ionization, but LC-MS/MS analyses have additional sources of variation. Correcting variability in sample preparation recovery or matrix effects other than during ionization (such as differences in target solubility or adsorption to vial surfaces between matrix and neat solution) still requires an ISTD spiked at the start of the sample preparation. To correct for sample injection volume, an external standard (ESTD) could be spiked in the last step of the sample preparation. When using PCIS correction, these spiked ISTDs or ESTDs should also be corrected with a PCIS. Instead of a spiked ISTD per analyte, a single ISTD is expected to correct for the sample preparation recovery of a whole range of analytes. With the aim of the present study being to show the potential of PCIS, sources of variability other than during ionization are not within the scope of this study and all samples were spiked after the sample preparation.