Imaged capillary isoelectric focusing (iCIEF) is widely used for protein charge heterogeneity analysis during development and manufacturing of biotherapeutic drugs. Although iCIEF can indicate the presence of a charge isoform at a specific isoelectric point, it generally cannot provide molecular structure information. To address this analytical need, our group at Pfizer initiated a multi-month project to evaluate a novel iCIEF-MS platform recently described by Mack and coworkers at IntabioRef1. By using microfluidic chip-based technology, the Blaze system directly couples iCIEF with MS analysis via an on-chip ESI tip, enabling MS spectra to be collected for iCIEF peaks. We will report results from our evaluation of this iCIEF-MS system using a variety of mAb test samples.