| abstract |
An enzyme electrode, specific binding or the like electrochemical assay method capable of performing always stably high detection sensitivity (responsibility) and reappearance even in the case of blood, urine and the like samples that contain interfering substances and also of applying suitably to disposable use, and a novel p-phenylenediamine compound which is used in the assay method. Particularly, an electrochemical assay method in which a substance in a liquid sample is assayed using at least one oxidoreductase, wherein an oxidoreductase, an electron mediator and an electrode which performs electron transfer with the mediator are arranged in the assay system, and a compound of the following formula [I] or a salt thereof is used as the mediator which is highly soluble in water, dried (by freeze-, vacuum- or air-drying) easily and stable under dry condition, shows a high electron transfer rate with enzymes and is almost free from the influence of interfering substances in blood, urine and the like samples:n wherein R 1 to R 4 may be the same or different from one another and each means a hydrogen, a straight- or branched-chain alkyl group having 1 to 4 carbon atoms, optionally having a substituent, providing that at least one of R 1 to R 4 has one or more groups selected from hydroxyl, mercapto, carboxyl, phosphonooxy and sulfo. |