As an excellent element-specific detection technique,ICP-MS has been successfully extended to biological application such as immunoassay and DNA hybridization through the efforts of our and other groups in recent years[1-3].In this report,we would like to extend ICP-MS to the study of reaction mechanism in organic chemistry.As an example,a rapid screening of the copper intermediates in Cu(I)-catalyzed azide– alkyne cycloaddition was realized.The mononuclear and dinuclear copper intermediates by using 63Cu+ and 65Cu+ ions as catalyst with or without ligands protection both are successfully observed,while the copper intermediates without ligand protection are very active,which are extremely difficult to be observed by other existing techniques.The alkynyl group in the copper-intermediates was further identified by isotope reagents of phenylacetylene and phenylacetylene-D as reactant,respectively.In addition,capturing mononuclear and dinuclear Zn(I)-intermediates,other than Cu(I)-intermediates,in azide-alkyne cycloaddition were also achieved.This study provided not only a tool to rapid screen the intermediates in the reaction of azide-alkyne cycloaddition,but also provided a universal platform to study the mechanism of organic reactions catalyzed by unstable metal(I)ions,so as to discover new candidates of metal(I)catalysts.