Relative to the synthetic work which inspired this study, we (a) used a lower tem- perature, (b) worked at a microgram scale instead of at mg or g scales, (c) took no special precautions to exclude oxygen or adventitious water, and (d) deviated substantially from the 1:1 azide:alkyne stoichiometry used in synthetic work, in order to ensure azide and catalyst were present in excess. Our initial success with this pilot reaction suggested that RuAAC could be a viable derivatization tool for analysis of internal alkynes, as shown in Scheme 1.