Abstract: Analyzers determine the concentration of a test substance by measuring the change of pH in a sample liquid after reaction of the test substance with a reactant. The analyzers have a tube connected between first and second microcapillary pH electrodes. In a first embodiment, the tube functions as a reaction chamber by having a reactant immobilized on a wall of the tubing or confined within the tubing. In a second embodiment, the reactant and test substance are mixed upstream relative to the first and second microcapillary pH electrodes, with the tubing serving as a delay circuit for a kinetic measurement. Output signals of the microcapillary flow-through electrodes are used to determine a change in pH, the change in pH being indicative of the concentration of the test substance.

Abstract: A method and apparatus for the determination of the concentration of certain chemical substances such as glucose, urea, enzymes, etc. in biological solutions such as blood, serum, urine, using a technique of differential pH measurement using two pH electrodes, and measuring pH changes in the solutions after the addition of specific reagents, the concentration being determined according to the formula[sample]=FCAL.times.(.DELTA.pH.sub.c -.DELTA.pH.sub.b -.DELTA.pH.sub.o)wherein [sample] is the concentration of the substance in the sample, FCAL is a calibration factor, .DELTA.pH.sub.c is the measured pH of the reacted sample, .DELTA.pH.sub.b is a pH correction for the reaction initiating compound, and .DELTA.pH.sub.o is a correction for background pH changes.