Updated publication reference for PubMed record(s): 33555887. This work presents methods for identifying and then creating a mass spectral library for disulfide-linked peptides originating from the NISTmAb, a reference material of humanized IgG1k monoclonal antibody (RM 8671). Analyses involved both partially-reduced and non-reduced samples under neutral and weakly basic conditions, followed by nanoflow liquid chromatography tandem mass spectrometry (LC-MS/MS).