Finally, we explored how PTMs impact proteoform migration and detection times on the ZipChip CE-MS platform as understanding these can aid with proteoform identification when potential components have similar masses. The ZipChip platform separates analytes through differences in electrophoretic mobility, which is a function of an analytes size and charge . Calculating the charge to mass ratios (z/m) of the identified proteoforms will give an indication of their order of detection, as proteins with a larger positive z/m are expected to migrate through the chips channel faster, and thus be detected in the MS earlier. ProtPi () was utilized to determine the theoretical charge (z) of each identified proteoform at pH 2.4 (the pH of the peptide BGE) and then this value was used along with their respective theoretical masses (m) to calculate their respective z/m values. Our initial general observation across all serotypes tested was that VP1 proteoforms were detected first, followed by VP2 proteoforms and VP3 proteoforms (Figure ). This was previously seen by Zhang et al and is expected based off the calculated z/m values of the expected predominant proteoform for each VP ((Ac)VP1, VP2, and (Ac)VP3). When focusing on proteoforms with PTMs, we saw that, across serotypes, the phosphorylated proteoform of a VP was always detected after its unphosphorylated counterpart (Figure ). Such observations are a consequence of the negatively charged phosphate reducing the overall charge of the proteoform while also increasing its mass. This leads to lower z/m ratios of the phosphorylated proteoforms compared to their unphosphorylated counterparts (Table ), resulting in slower migration through the chip and later detection.