Particle or cell analyzer and method

A particle analyzing apparatus comprising:

• a capillary tube having an internal cross-sectional area, a first end and a second end opposite to the first end, said first end being adapted to be suspended for direct immersion into a sample fluid containing particles to be analyzed, said capillary tube including an analyzing region;
• a source of light;
• an optical system configured to receive and focus the light from said source to form and direct a rectangular beam through said capillary to define the analyzing region in said capillary tube;
• a pump connected to the second end of the capillary tube, said pump being adapted to be capable of drawing a known volume of the sample fluid through the first end into the capillary tube and passing through said analyzing region;
• at least one first detector for detecting fluorescent light emitted by particles excited by said beam;
• and
• a tee structure having a first, second, and third connections;
• a first conduit extending from the first connection and connected to the second end of the capillary tube;
• a second conduit and a valve connected to the second connection and a waste dump;
• and
• said pump is connected to the third connection;
• whereby when the valve is closed, the pump draws the sample fluid from the first end of the capillary tube through said capillary tube, and wherein the second conduit has an internal cross-sectional area that is larger than the cross-sectional area of the capillary tube such that when the valve is opened the pump discharges substantially all the fluid sample previously drawn through the capillary tube to the waste dump.