Recently we have shown that, in difference to most of polysaccharides, which are considered as electroinactive, chitosan samples containing both glucosamine (GlcN) and N-acetylated glucosamine (GlcNAc) residues are involved in the catalytic hydrogen evolution reaction (CHER) at mercury electrodes, and can be determined by voltammetric or chronopotentiometric stripping. Here we show that polysaccharides and oligosaccharides composed of GlcN, but not those containing only GlcNAc residues, take part in CHER, allowing their easy label-free electrochemical detection. GlcNAc-containing oligosaccharides can be easily transformed into electroactive species by deacetylation using hot KOH treatment. This procedure can be applied also to electroinactive GlcNAc-containing glycans, frequently occurring in glycoproteins, allowing their electrochemical determination at submicromolar level. (C) 2015 Elsevier Ltd. All rights reserved.