Abstract: A body fluid sample is diluted with a diluent which comprises an aqueous solution containing bis(2-hydroxyethyl)-iminotris(hydroxymethyl)methane and boric acid to obtain a diluted body fluid sample, and the ion concentration in the diluted body fluid sample is determined with ion-selective electrodes, whereby the variation width of pH in the diluted body fluid sample can be held down to a narrow range. As a result the determination can be made without exerting adverse effects on the ion-selective electrodes, and errors in determination can be markedly reduced as compared with cases where the conventional diluents are used.

Abstract: An apparatus and method for analyzing at least two analytical items in a sample solution in a single container, wherein a series of transparent containers supported on a rotatable disc pass over a sample-receiving position, a first reagent solution-adding position, a second reagent solution-adding position, an optical path of a photometer, a solution-discharging device and a washing device. In the sample-receiving position, a fixed volume of sample is introduced into one of the transparent containers. In the first reagent solution-adding position, the first reagent solution is introduced into the transparent container, whereby a reaction is allowed to proceed. Subsequently, the container is passed across an optical path, and absorbance of light by the reaction solution is measured, to provide first measurements.

Abstract: In analysis of a liquid sample by adding a reagent to a liquid sample, thereby initiating reaction, and measuring a rate of the reaction, thereby quantitatively determining an analytical item being contained in the sample and taking part in the reaction, the analysis is carried out by measuring a physical quantity of the liquid sample, setting an effective limit level for the sample, then adding a reagent to the sample, measuring a physical quantity of the resulting liquid mixture, and computing the analysis value of the desired analytical value of the sample from the physical quantities so far measured before the effective limit level is reached. An exact effective limit level can be automatically set for the individual sample, and thus an analysis value can be obtained with high exactness.