For optimal accuracy, we recommend assessing purity via flow cytometry. The Anti-Human CD138 (Syndecan-1) Antibody, Clone MI15 (Catalog #60003) can be used for this purpose. Note, however, that the antibody clone can be partially blocked. Hence, titration of the antibody will be important when assessing purity of the sample after CD138+ plasma cell isolation. The antibody concentration will need to be adjusted until the fluorescent antibody signal reaches a plateau during flow cytometric assessment. Alternative approaches to to assess purity via flow cytometry are: Intracellular detection of κ (kappa) and λ (lambda) light chains with the appropriate fluorchrome-conjugated anti-human monoclonal antibodies against these respective antigens. Use of fluorochrome-conjugated Anti-Human CD38 Antibody, Clone HIT2 (Catalog #60014) and Anti-Human CD45 Antibody, Clone HI30 (Catalog #60018) to detect CD38+CD45variable cells. Use of a fluorochrome-conjugated secondary antibody, such as Goat Anti-Mouse IgG (H+L) Antibody, Polyclonal (Catalog #60138). For recommendations on how to include appropriate controls for flow cytometry and the best practices for gating please see the Tech Tip: Considerations for Flow Cytometry Gating