Abstract: A chromogenic solution for enzyme immunoassay. A stabilizing agent is added to chromogenic solutions containing chromogen of the hydrogen donor type. The stabilizing agent is an alkylhydroxylamine, preferably N,N-diethylhydroxylamine. The N-N diethylhydroxylamine retards degradation of the solution of the chromogen in solvent and is particularly effective in retarding discoloration of a chromogen-solvent solution placed in storage over an extended period of time. The alkylhydroxylamine preferably in the form of N,N-diethylhydroxylamine has the additional property that it does not adversely affect the activity of enzymes employed in enzyme immunoassays. It also does not interfere with binding specificity or reactivity of antibodies.

Abstract: Colorimetric detection of bindable substances such as antibodies and antigens using chromogens of improved sensitivity and stability. The chromogens take the form of activated solutions containing tetramethylbenzidine or water soluble derivatives of tetramethylbenzidine. Such chromogens are of particular use in home testing applications for detection of antigens such as human chorionic gonadotropin, human luteinizing hormone, and gonococcus bacteria, as well as the detection of antibodies for these substances.