Abstract: The present invention concerns a novel method and kit system for the detection of solid-phase bound primary amines, secondary amines, or thiol groups comprising adding a fluid to said substrate and further comprising adding a novel reagents to said substrate and recording a colour reaction on said substrate that comprise said amine or said thiol groups. The method and kit of present invention can be used for the quantitative determination of organic substituents with primary or secondary amines or with thiol groups immobilized on or in insoluble materials.