Abstract: An apparatus is provided for hematology testing, which has a sensing unit defining a counting orifice for the flow of a blood sample through the counting orifice to analyze the blood sample, and a pump unit having three syringes. A first syringe is coupled in fluid communication with the sensing unit on the inlet side of the counting orifice for injecting a stream of blood sample through the counting orifice. A second syringe is coupled in fluid communication with the sensing chamber on the inlet side of the counting orifice for simultaneously injecting a sheath of fluid surrounding the sample stream on the inlet side of the counting orifice. And a third syringe is coupled to the sensing chamber on the outlet side of the counting orifice for aspirating a sheath of fluid from the sensing chamber surrounding the sample stream on the outlet side of the counting orifice.

Abstract: A method and apparatus are provided for differentiating cells in an automated particle analyzer, such as for use in hematological analysis, by measuring apparent cell size (or volume), membrane integrity and intracellular complexity ("voltaic fragility"). The cells are suspended in a selected reagent mixture including an electrolytic fluid, such as diluent, and if necessary, one or more membrane-modifying agents are selected and mixed in relative quantities in order to selectively alter the membrane structure (i.e., the membrane integrity) of certain cells and thereby enhance cell discrimination. A predetermined dc voltage is applied across a sensing orifice to thereby create a dc electric field within and around the orifice, and the reagent mixture is passed through the center of the orifice.

Abstract: In an apparatus for fluid analysis, such as hematologic analysis, a plurality of reagent-mixture components are each injected by a respective pump through a valve matrix and into a flow-injection unit. The flow-injection unit defines a mixing chamber including a plurality of protuberances or nubs projecting inwardly toward the center of the chamber, and spaced relative to each other both axially and radially. As the reagent-mixture components are injected into the mixing chamber, the nubs agitate the fluid flow and create turbulence, thereby dispersing the reagent-mixture components and in turn mixing the components together to create a reagent mixture. The flow rates of the reagent-mixture components are adjusted in order to select the reagent-mixture ratio as the components are combined in the flow-injection unit to thereby create the selected reagent mixture.