Which technique is used to count the number of cells and differentiate between dead and live cells?

Flow cytometry is a powerful technique used to count cells while simultaneously differentiating between live and dead cells. This method utilizes laser-based technology to analyze the physical and chemical characteristics of particles in a fluid as they pass through a detection apparatus. During flow cytometry, cells can be stained with specific dyes that indicate viability; for instance, certain fluorescent dyes will penetrate only dead cells, while others will stain live cells. This allows for precise quantification and differentiation of cell populations based on their viability status.

In contrast, centrifugation is primarily a method for separating components of a mixture based on density and does not provide information on cell viability or count. Staining, while it can indicate cell viability if specific dyes are used, does not in itself allow for accurate counting of cells unless combined with another technique. Microscopy can be used for counting cells as well and could potentially assess viability with the right staining techniques, but it lacks the efficiency and automation that flow cytometry offers for counting large populations of cells.