Analysis of Oligo-κ-carrageenan by Reversed Phase Ion-pair Ultra Performance Liquid Chromatography Coupled with Electrospray Ionization-Time of Flight-Mass Spectrometry

The reverse phase ion-pair ultra performance liquid chromatography coupled with electrospray ionization time of flight mass spectrometry (RPIP-UPLC-ESI-Q-TOF-MS) method was developed for the analyses and elucidation of sulfated oligosaccharides. Mass spectra were obtained by ESI-Q-TOF-MS in both positive and negative ionization modes. Oligo-κ-carrageenans were separated on BEH C18 column using heptylamine (20 mM, pH 4) as the ion-pairing reagent and A (H2O with 25% heptylammonium formate) and B (MeOH with 25% heptylammonium formate) as gradient eluent. Thus, oligo-κ-carrageenans were separated until pentatetrasaccharides were obtained. In addition, abundant structural information was obtained through the MS spectrometric analysis, and all acid hydrolyzed oligo-κ-carrageenans were identified as odd-numbered oligosaccharides. To further confirm these compounds, polyacrylamide gel electrophoresis (PAGE) was carried out. Furthermore, the described method has wide applicability to rapidly screen and provide structural information of oligo-κ-carrageenans.