novel method and reagents for generating reversibly tagged saccharides , aldehydes , carboxyl acids , or orthoacetates useful in analytical and diagnostic applications are disclosed . saccharides are coupled at the reducing end to tagging moieties comprising a reagent selected from a ortho - diaminobenzoic - peptide , an aldo - imidazole or n - methylated aldo - imidazole , or an ortho - phenyldiamine or substituted opd . the tagged saccharide further comprising detectable or functional groups coupled to the tagging moiety are provided . kits and reagents for chromatography and mass spectrometry are disclosed .