Abstract: In a diffraction grating grooves having at least two kinds of grating constants are alternately arranged so as to repetitive at a constant period.

Abstract: An electrochemical sensor is formed having a working electrode for detecting hydrogen peroxide surrounded by a cylinder portion, and with an enzymecontaining membrane at its tip. The membrane has a porous layer permeable to hydrogen peroxide between a layer containing an immobilized enzyme capable of decomposing hydrogen peroxide and a layer containing an immobilized enzyme capable of decomposing a substrate to form hydrogen peroxide. The cylinder portion is embedded in the layer containing the hydrogen peroxide decomposing enzyme and surrounds the working electrode such that the electrode is in contact with the porous layer but is not in contact with the layer containing the hydrogen peroxide decomposing enzyme. The layer containing the hydrogen peroxide forming enzyme is on a side of the porous layer opposite the electrode so as not to contact the electrode. Activity of the hydrogen peroxide decomposing enzyme is no more than one-fourth of the activity of the hydrogen peroxide forming enzyme.

Abstract: A recess of a predetermined thickness is formed in the bottom of a cylindrical vessel and a hole for the liquid-junction is formed at the center of the recess, to which is joined a resilient NH.sub.4.sup.+ selective membrane. Since the NH.sub.4.sup.+ selective membrane has a thickness larger by about 0.1 mm than the depth of the recess, the NH.sub.4.sup.+ selective membrane is protruded out of the bottom of the vessel by so much. A polyester woven fabric on which urease is immobilized is attached to the vessel so as to cover the NH.sub.4.sup.+ selective membrane. Since the immobilized enzyme membrane is applied with an appropriate tension by the slightly protruded ion selective membrane, bondability between the two membranes can be improved.

Abstract: A liquid film type, anion-selective electrode of the present invention is suitable for measuring a chloride ion concentration of blood. A sensitive film contains a plurality of plasticizers having different dielectric constants, an anion-sensitive substance and a polymeric support material for supporting them. An appropriate content of o-nitrophenyloctylether having a high dielectric constant is 5-30% by weight, an appropriate content of n-tetradecyl alcohol having a low dielectric constant 5-40% by weight, and an appropriate content of dimethyldioctadecylammonium chloride as the anion-sensitive substance is 5-30% by weight. An electrode for measuring anions with such a sensitive film has less adverse affect by protein on measurements. The sensitive film further containing n-dodecyl alcohol has a much smaller error of measurement.

Abstract: A sensing membrane is fixed to one end of a tube comprising polyvinyl chloride. An aqueous sodium chloride solution is contained in the tube, and is in contact with an internal electrode wire. The sensing membrane comprises a support substance of polyvinyl chloride, a sensing substance of quaternary ammonium salt having an alkyl chain having 8 to 16 carbon atoms, and a plasticizer of normal decyl alcohol. Anions in a body fluid sample can be measured with a small measurement error by an electrode provided with the sensing membrane of that composition.