Patent GB-1457491-A (GB)
Title: Analysis system
Inventor: STEIN BERNARD
IPC: G01N27/416
Filed: 1975-03-26
Abstract: 1457491 Determination of blood gases and pH INSTRUMENTATION LABORATORY Inc 26 March 1975 [27 June 1974] 12743/75 Headings G1B and G1N [Also in Division F2] An analysis system which may be used for determination of oxygen and carbon dioxide and of the pH in blood comprises Figs. 1, 4 a thermostatting chamber 20, first and second flow-through measuring cells 24, 26 mounted in the chamber, the chambers having a common inlet port 74, a common outlet port 76, sampling mechanism 34 and a conduit 70 connecting the sampling mechanism to the inlet port of the measuring cells, positive displacement pump means 42 and conduits 202, 96, 98 connecting the outlet ports from the measuring cells to the pump means, and flush fluid supply means 64, 38, the sampling mechanism being movable between a first position (the raised position shown in Fig. 4) for taking in a sample to be analyzed and a second position in which the sampling tube is immersed in flush fluid in the flush fluid supply means 38, the pump causing flow of the sample or of the flush fluid through both the measuring cells. In the system shown, the measuring cells comprise oxygen electrode 24, carbon dioxide electrode 26 and pH electrode 22, the sample liquid flowing from sampler mechanism 36 through heater 58 (which is itself in the thermostatting chamber) and conduit 74 to a measuring cell chamber 76 which is bounded by the surfaces of the electrodes Fig. 7. The sample liquid then flows through conduit 78, through a calibrating valve-member 52 and by conduit 202 to pH electrode 88, past calibrating electrode 50 and through pump 42 to waste at 66. The results of the measurements are displayed at 158, 168, 180. Buffer solution from supplies 60, 62 are used for calibration of the pH electrode and gases from sources at 146, 148 are used to calibrate the electrodes.  The electrode assembly may comprise Fig. 7 oxygen electrode 24 which has cathode wire 250 sealed in glass envelope 252 with its tip 254 exposed and covered with oxygen-permeable membrane 256, and a silver/silver chloride anode 258; carbon dioxide electrode 26 which has pH-sensitive glass membrane 260, chamber 262 housing silver/ silver chloride electrode 264, outer chamber 266 filled with electrolyte and containing silver/silver chloride reference electrode 270, disposed over the end of the assembly a spacer membrane 272 and a carbon-dioxide-permeable membrane 274, the oxygen and carbon dioxide electrodes being seated on sealing membranes 284, 256; and pH electrode 22, Fig. 9 the pH electrode being fed with sample liquid flowing through a passageway aligned with 214 from the chamber 76 shown in Fig. 7 into conduit 306 of the electrode, the electrode comprising capillary section 300 which includes pH-sensitive glass section 88, silver/silver chloride halfcell 302 disposed in electrolyte chamber 304, the capillary section having tip portion 308 carried in seal 310 in member 312 which provides a leak junction flow-path having a "jog" 314, 316 extending to part 318 adjacent polycarbonate membrane 90, the other surface of membrane 90 being exposed to electrolyte from a reservoir (94 in Fig. 4) in which is disposed a saturated calomel halfcell reference electrode 28, the sample liquid flowing to waste via 96.