Purifying and analysing sulfated oligosaccharides by mass spectrometry often constitutes a challenge. We present here a single step method to isolate sulfated compounds from a complex mixture of neutral and acidic oligosaccharide-alditols. The strategy relies on the exclusion of sulfated molecules from strong cation exchange resin. By testing a wide range of reduced mucin type O-glycans isolated from different biological sources, we demonstrate that this method permits, without prior chemical modification, the specific purification of sulfate-containing oligosaccharides present in any quantity from very complex mixtures of molecules.