Abstract: An apparatus and method for verifying the drop delay in a flow cytometer, which is indicative of the time that elapses from a moment at which a particle of interest is detected at an interrogation point in the flow of cytometer to the moment at which a sorting condition, such as a charging potential, is applied in response to the detection to a droplet forming at a droplet forming location in the flow cytometer. The apparatus and method analyzes the content of the droplets formed by the flow cytometer, and based on the analysis, provides an indication as to whether the drop delay time at which the flow cytometer is operating is correct. Specifically, the charging potential should be applied to the droplet containing the detected particle of interest. The content of the droplets can be analyzed at the droplet formation point, or at a location downstream of the droplet formation point, to detect the presence or absence of a particle of interest that was detected at the interrogation point in the flow cytometer.

Abstract: A multi-laser flow-cytometry system provides for inter-location emissions crosstalk cancellation, through either pulse subtraction or gating, to avoid false triggering based on shadow (pre- and post-) pulses that occur when red-excited red emissions are detected by a photodetector arranged to detect blue-excited red emissions. This overcomes a problem of undercounting of counting beads that led to misdeterminations of cell counts when blue-excited red fluorescence detections were used as a trigger. The approach also provides for more accurate quantitative data regarding fluorochrome emissions amplitudes.