To optimize cell separations by centrifugal elutriation, we constructed an on-line computer-controlled multiparametric light-scatter system. A bypass sample flow, at the outlet of an elutriation rotor, is hydrofocussed and three scatter parameters of each cell are determined up to a maximum of 15,000 cells/second. The 18-bit representation of the parameter values are cumulatively stored by means of a direct memory access interface. The histogram memory is continuously displayed to provide information on the number and type of cells that are elutriated. A special purpose operating system, implemented on a stand-alone computer configuration, allows a high data-acquisition rate and ample data processing capacity. In addition, a local network driver was constructed to facilitate off-line detailed analysis of the data. The equipment is well suited to monitor the centrigural elutriation process. The flexibility of the system allows an extension of the monitor to computer-controlled elutriation.

Spectral decomposition of flow cytometric datafiles of arbitrary dimension reveal information of both the signal and the noise cornponents that constitute the histograms. This spectral information is used to construct a low-pass digital filter, which removes the cal parameters. high-frequency noise from the actual data. It is shown that this procedure guarantees nontrivial smoothing of the flow cytometric data in accordance with the local experimental situation. Gs a consequence optimal reconstruction of the signal is possible, which facilitates unambiguous interpretation of the data files and mathematical estimation of the statisti-