Abstract: A pH sensor includes a substrate formed of an electrically conductive carbon material. A hydrogen ion-sensitive layer is formed on the substrate surface. The layer is formed of an electrooxidation polymer of a nitrogen-containing aromatic compound selected from the group consisting of 1-aminopyrene and a mixture of 1-aminopyrene and pyridine.

Abstract: A pH measurement device includes working and reference electrodes. The working electrode has a linear electrically conductive substrate, at least a distal end surface of which consists of platinum, and a selective hydrogen ion permeable layer formed on the distal end face of the substrate. The reference electrode includes an electric conductor formed to be insulated from the working electrode and surrounding the working electrode, a polymer-silver (I) complex layer formed on the outer circumferential surface of the conductor, and an ion-conductive layer containing an anionic compound and formed on the complex layer. The pH of a solution is measured in accordance with a difference between a potential of the working electrode and that of the reference electrode.

Abstract: A body fluid-filtering device includes a housing provided with a body fluid inlet, a filtrate outlet and a filtration residue outlet, and a filtering means disposed in the housing and including first and second filtering elements alternately superposed on each other with a space therebetween. The first and second filtering elements are each formed of a meshed core material and filtering membranes which cover both sides of the core. The core material of the first filtering element has openings of 700 to 1300 microns, and the core material of the second filtering element has openings of 300 microns or less.