IMMUNOASSAY PROTECTING SOL PARTICLE FROM DISINTEGRATION

PROBLEM TO BE SOLVED: To provide a sol particle immunoassay method which does not cause coagulation and brings discoloring. SOLUTION: First, a fluid sample containing an object of analysis is added to a cushioned water system containing a metal particle colloid on whose surface a bind partner specific to the object of analysis or its analogue is bound and a polymer which is bound with the bind partner to protect the metal particles. Next to this, an instabilizing agent which coagulates a metal particle colloid is added to coagulate the metal particles unprotected by a polymer. After this, spectral analysis of the colloidal metal particles is performed, and by comparing its result with a known result, the concentration of the object of analysis is measured.