CE-SDS is the micro electrophoretic analogue of traditional slab-gel size-based separations (e.g. SDS-PAGE). Analytes are complexed with SDS and injected into a narrow-bore glass capillary filled with an uncrosslinked polymer sieving matrix. A high voltage applied across the capillary drives the anionic SDS complexes toward the detection window; their migration is retarded in a size-dependent manner by differential interaction with the sieving matrix. NISTmAb RM 8671 monomeric purity was measured by CE-SDS under non-reducing conditions (nrCE-SDS) according to the qualified method protocol . Glycan occupancies of the heavy chain and relative abundance of non-reducible species were measured by CE-SDS under reducing conditions (rCE-SDS) according to the qualified method protocol . The electropherograms of the CE-SDS analyses of RM 8671 were consistent in all salient features to that observed previously with PS 8670 . The results for RM 8671 compared to PS 8670 method qualification results are presented in Table S8 (see ESM) and Fig. 5. In addition to the calculated physicochemical reference values listed in ESM Table S8, it was determined that method performance (migration times and relative abundance) of individual, resolved components (monomer, light chain, heavy chain, etc.) may be useful to the stakeholder in comparing performance of orthogonal assays likely to be developed with the NISTmAb. Therefore additional Tables S9, S10, S11, and S12 are included in the ESM for PS 8670 (from the qualification exercise) and RM 8671 lots 14HB-D-001, 14HB-D-002, and 14HB-D-003 respectively.Fig. 5Homogeneity of RM 8671 lots by monomeric purity, measured by nrCE-SDS. The measured range for PS 8670 during qualification is included for comparison. Error bars represent ±3uc based on ANOVA analysis for each lot (n = 3 for RM 8671 lots) or from intermediate precision data for PS 8670 Qualification 