Single-cell Proteomics has emerged as an extremely promising new field capable of unlocking the vast cellular heterogeneity that defines biology, disease, and therapeutic response. However, it presents enormous challenges, including maximizing both quantitative signal and experimental throughput. We utilize the multiplexed method (e.g., SCOPE-MS/SCOPE2) in which individual cells’ proteomes are labeled, pooled, and combined with abundant carrier material using TMT tags, improving both peptide identification and cell throughput. Still, accurate quantitation via TMT reporter ions remains challenging, in part due to the co-isolation artifacts they suffer. TMT complement (TMTc) ions, consisting of the peptide plus TMT balancer moieties, have the potential to provide quantitative read-outs essentially free of co-isolation artifacts, so long as they can be sufficiently resolved.