What is hydrodynamic focusing primarily used for in flow cytometry?

Hydrodynamic focusing is a critical technique utilized in flow cytometry to ensure that cells or particles are aligned in a single file as they pass through the laser beam for analysis. This precise alignment is crucial because it allows the detectors to accurately capture and analyze the light scatter and fluorescence emitted from each individual cell or particle.

In hydrodynamic focusing, a sample stream containing the cells is surrounded by a sheath fluid. This arrangement causes the cells to be focused into a narrow stream, which minimizes the occurrence of multiple cells passing through the laser beam simultaneously. As a result, each cell can be analyzed independently, enabling accurate measurements of their properties, such as size, shape, and fluorescence intensity.

The other options do not describe the primary function of hydrodynamic focusing. While high temperatures, sample mixing, and enhancing fluorescent labeling are important considerations in flow cytometry, they do not pertain to the specific role of hydrodynamic focusing in positioning cells for optimal detection.