Fig. 1.

On-chip enrichment of acidic N-glycans. a Diagram of the specialized TiO₂-PGC chip. b Extracted compound chromatograms (ECC) of N-glycans detected in the load, flow-through (neutral N-glycans) and eluate fractions (acidic N-glycans) of the TiO₂ enrichment column as analyzed by liquid chromatography coupled with nanoelectrospray ionization quadrupole time-of-flight mass spectrometry in the positive mode. c TiO₂ enrichment column selectively captures acidic N-glycans. Neutral N-glycans (blue dot) do not efficiently bind to TiO₂ and are recovered in the flow-through fraction, whereas acidic N-glycans are retained on TiO₂ during the load and flow-through steps and are eluted with the elution buffer. The enrichment recovery rates (numbers beside the dots) of five acidic N-glycan standards (red dots with black circles) are also given