Any single-cell suspension where cells are between 500 nm and 20 μm can be run. Samples can be provided in 5-ml Falcon tubes, 15-ml Falcon tubes, Eppendorf tubes, multi-well plates, or slides.
Cells can be at a concentration of up to 5 million per mL in PBS or media, but serum should be limited to 2 percent serum, as more than this can affect the charge applied to the stream. You can also add HEPES (25 mM), EDTA (1 mM) or DNAse (10 U/ml) to avoid clumping. If you are concerned that your sample is too concentrated, bring in some media to dilute your sample. Filter your cells through a cell strainer or filter-top tube.