Home Cytometry History Individual Histories Robert C. Leif

Robert C. Leif

The photograph shows me with the Automated Multiparameter Analyzer for Cells, AMAC I. I designed the electro-optical flow transducer and voltage sensing bridge circuit to detect the electronic volume (Coulter Volume). Richard (Rick) Thomas built the power supplies, assembled the device, and operated it. While I worked for Wallace Coulter, I used his current sensing, single ended circuit. Rick Thomas went on to create the Beckman Coulter Cell Lab Quanta flow cytometer, which I believe employs potential sensing rather than a current sensing electronics.

One of the major reasons that I went to Coulter was that Wallace and Walter Hogg had invented-created an instrument that would do combined radiofrequency, RF, and conventional electronic cell volume measurements, DC. Wallace named the ratio of the RF to DC impedance opacity. My group was able to demonstrate that the opacity was related to buoyant density, which, in turn, is related to cell age, at least in the case of blood erythrocytes and bone marrow. My goal was to combine these two electronic modalities with fluorescence and light scattering measurements. I was finally able to achieve this just prior to the end of my stay at Coulter. The combination of the two electronic parameters with median angle light scattering, ca. 45°, was the basis for the Coulter 5-part differential white cell counter.

The relationship between the multiparameter spectra and the cell types was deduced by separating the blood leukocytes by buoyant density centrifugation in linear gradients with one aliquot of each sample being analyzed by the cytometer and the other being prepared by centrifugal cytology.

Subsequently, I was able to equip a prototype of the leukocyte analyzer, which was designed and engineered by others, with a spherical flow cell that had a square orifice. This instrument measured the previous electronic impedance and light scattering parameters together with fluorescence. Although, I was kindly permitted by Wallace to publish this work, unfortunately the instrument was never commercialized.

Automated Multiparameter Analyzer for Cells Proposal

Multi-Parameter Transducer Cytometry

Two-Dimensional Impedance Studies