Device and process for mixing a sample and a diluent

Apparatus for controlling the dilution of a sample in a diluent in the analysis of the sample in a detector

• comprising the combination of
• a cavity having a non-wetting porous membrane separating said cavity into a supply chamber and a dilution chamber,
• a supply of a sample liquid,
• a first conduit for transporting the sample liquid from the supply to the supply chamber and from the supply chamber to a discharge means,
• a first valve positioned in said first conduit between the supply and the supply chamber actuable to close and hold sample liquid in said conduit and supply chamber,
• a second valve positioned in said first conduit between said supply chamber and said discharge actuatable to close and hold sample liquid in said conduit and supply chamber,
• a reservoir comprised of said first and second valves, said supply chamber and said first conduit,
• a means for selectively applying pressure on said sample liquid in said reservoir, including said first conduit and supply chamber, positioned between said second valve and said supply chamber,
• said pressure applying means having a control for varying the applied pressure,
• said first and second valves, pressure applying means and control being operative to initiate and cease the application of pressure on said transported sample liquid in said supply chamber in excess of the minimum liquid entry pressure differential
• a second conduit for transporting a diluent stream through said dilution chamber, which diluent stream transported through said dilution chamber draws not more than minute amounts of sample through the membrane in the absence of a minimum liquid entry pressure upon the sample in the supply chamber,
• an analyzer for sensing said sample in the diluent so constructed and arranged as to receive diluted sample from the dilution chamber,
• said membrane being impervious to the passage, in a controllable detectable amount, of said sample from the supply chamber to the dilution chamber in the absence of the application of pressure in the reservoir on the transported sample liquid in excess of the minimum liquid entry pressure differential
• said minimum liquid entry pressure differential being the differential across the membrane to provide sample penetration through the pores and no substantial sample penetration through the membrane material.