Patent GB-774711-A (GB)
Title: Apparatus for analyzing liquids which contain a crystalloid substance and a non-crystalloid substance
Inventor: SKEGGS LEONARD TUCKER
IPC: F04B43/08
Filed: 1954-09-13
Abstract: A solution of urease for use in the determination of urea in body fluids (see Group III) is prepared by stirring ground Jack Bean meal with distilled water, refrigerating, decanting, clarifying in a centrifuge or by filtration, and then dialyzing against a saline solution.  The product is evaporated under vacuum to a thick paste and mixed with glycerol.ALSO:<PICT:0774711/III/1> In apparatus for the automatic analysis of liquids, e.g. body fluids, which contain a crystalloid substance and a non-crystalloid substance, the crystalloid constituent is separated, e.g. by dialysis, from a flowing stream of the liquid and transferred to a second flowing liquid stream, the crystalloid content of which is determined, e.g. colorimetrically.  The apparatus shown diagrammatically may be used for the determination of glucose or urea in blood or other body fluid. For the determination of glucose, the body fluid, which may be diluted if desired, is pumped from container 41 and mixes in line 123 with saline solution from container 43.  The mixture flows through lines 126, 128 to the upper half of dialyzer 24, where it follows a tortuous course in contact with semi-permeable pellicle 27 made of "Cellophane" (Registered Trade Mark), parchment, or animal membrane. Glucose diffuses through the pellicle 27 into an aqueous solution of potassium ferricyanide pumped from containers 51, 53 into the lower part of the dialyzer.  This solution leaving the dialyzer passes through coil 63 in water bath 64 where it is heated to bring about reduction of potassium ferricyanide to potassium ferricyanide by the glucose, with an accompanying loss of colour.  The solution is cooled in coil 66 by a current of air from blower 68 and then flows through line 70a to a cylindrical passage 74 in a photo-electric indicating device (see Group XL(b)).  Light from source 32 passes through adjustable transparent plunger 76 and the liquid in passage 74, and then through coloured filter 90 to a photoelectric cell, connected to an amplifier, meter, and recorder 13.  Waste liquid flows out at 78. In the estimation of urea, the sample is mixed with a buffer solution containing potassium dihydrogen phosphate, sodium hydroxide, and sodium chloride, which is pumped from container 93, and with a solution of urease (see Group IV(b)) from container 95. Before passing to the dialyzer, the mixture flows through coil 98 which is heated by water bath 99 in order that the urease may convert the urea to an ammonium salt.  The ammonium salt diffuses into water flowing through the lower part of the dialyzer and this solution passes through pipe 146 to reaction tube 112 where it mixes with Nessler's reagent from container 114 and the colour developed is measured in the photometric system as for glucose. The sample and the various reagents are supplied at constant rate in the required proportions by means of pump 21 which comprises a plurality of parallel metal fingers actuated by a cam and cam shaft and pressing consecutively against sections of highly flexible tubes.  Different samples may pass through the apparatus in series and may be separated by air drawn in through lines 46, 55.