Liquid metering and transfer valve assembly particularly for flow

Abstract

A metering and transfer valve assembly particularly for use in particle analyzing apparatus for the study of particles in liquid suspension, the valve assembly having at least pair of inner and outer valve elements coaxially arranged in face to face frictional sealing engagement with a center valve element, each of the valve elements being independently rotatable, first passages defining a first flow path through the assembly, second passages defining a second flow path through the assembly, the first passages including a metering chamber for measuring and transferring a precise sample aliquot of sample flowing in the first flow path into the second flow path, the first flow path leading to a first exterior location and the second flow path leading to a second exterior location, and a drive fluid being introduced to the second flow path subsequent to transfer of said aliquot thereto for propelling said aliquot along the second flow path to the second esterior destination, the second destination being a flow scanning cell whereby an absolute count of the full content of said aliquot can be established. The first destination can be a flow scanning cell and the first flow path can lead liquid sample to said flow scanning cell before the aliquot is transferred to said path. A method of cytometric analysis is described as well as apparatus utilizing said valve assembly.