Flow cytometric electronic direct current volume and radiofrequency impedance measurements of single cells and particles

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Abstract
A flow‐system instrument is described that uses direct current and radiofrequency (rf) currents to detect simultaneously the low and high frequency impedance changes produced by biologic cells or particles suspended in saline traversing through a 93‐μm diameter sensing orifice. For nonmembranous particles and plastic microspheres both the Coulter direct current volume and rf‐parameter signals are proportional to particle volume. Cells having an intact plasma membrane produce rf‐impedance changes dependent additionally on the electrical properties of the plasma membrane and intracellular structures. Thus, biologically different cells having the same Coulter direct current volume can be distinguished if they differ in their electrical rf impedance properties.