Random Cell Arrival

In a well-mixed cell suspension, the cells are, in principle, randomly distributed throughout the sample. Although it would be advanta

Figure 1.2.5 In a flow cell, the sensing region is contained within a chamber with transparent sides. Although not shown here, the cell usually has a square or rectangular cross section. The flow cell optical configuration may be combined with jet-in-air sorting by replacing the exit section with a jet-forming orifice.

Figure 1.2.5 In a flow cell, the sensing region is contained within a chamber with transparent sides. Although not shown here, the cell usually has a square or rectangular cross section. The flow cell optical configuration may be combined with jet-in-air sorting by replacing the exit section with a jet-forming orifice.

geous to control the interval at which cells arrive at the sensing region, there is no way to do so, and in fact cell arrival time tends to follow a random distribution called the Poisson distribution. A number of effects may cause the actual arrival rate to deviate from the theoretical Poisson distribution: for instance, cells in the sample tube may not be mixed adequately, or may adhere to each other and tend to clump.

The random arrival of cells at the sensing area presents problems for the signal processing electronics of the cytometer. A cell may arrive too soon after the previous cell so that the cytometer is not ready to measure it, or even worse, two cells may be so close together that the cytometer sees them as one. Inevitably, a certain percentage of measurements cannot be made satisfactorily. Such problems are alleviated if the average cell arrival rate is kept low, but this means that samples take longer to process.

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