I’m using your Quantum Simply Cellular (QSC) beads to quantitate cell surface receptors, but I’m fixing my cells as part of my standard prep. Do I also need to fix the beads as well?

Sample handling/prep can certainly play a large role in quantitative flow cytometry, although we recommend against using fixation steps for our beads, as many of the fixatives are known solvents of our polystyrene particles (e.g. formaldehyde or paraformaldehyde). As such, exposure to these solvents risks modifying the particle, mainly the particle surface which was specifically characterized in ABC or MESF units (for QSC or Quantum MESF kits respectively). To best replicate conditions between the beads and cells, use the same suspending buffer conditions, but remove the fixative agent for the beads. Impacts of fixation can be investigated by comparing measured ABC/MESF values for unfixed and fixed cells (the latter at various durations as needed, e.g. 4 hours, 8 hours, and 24 hours).