Online comprehensive hydrophilic interaction chromatography × reversed phase liquid chromatography coupled to mass spectrometry for in depth peptidomic profile of microalgae gastro-intestinal digests

In this study, a comprehensive hydrophilic interaction chromatography × reversed phase coupled to high resolution mass spectrometry was developed for the peptide profile of microalgae formulations subjected to gastro-intestinal digestion. A BEH Amide column was employed in the first dimension, while a BIOshell ES-C18 Peptide in the second. As modulation interface, two trapping columns, in house packed with 1.9 μm fully porous monodisperse C18 particles characterized by high retention and efficiency, were tested and compared with SecurityGuard C18 cartridges, together with a dilution flow, to reduce first dimension mobile phase strength. The platform was coupled to both diode array detector and Orbitrap mass spectrometry. The developed setup provided high peak capacity (nc: 957) in only 60 min and a good orthogonality (A0: 0.70). The employment of the custom made C18 traps resulted in improved sensitivity (signal enhancement = 4) and a higher number of peptides detected (+58) especially of short lenght (≤ 6 aminoacids), with respect to the setup based on the security guard C18 traps. 184 phycocyanin-derived peptides were detected in Klamath and Spirulina gastro-intestinal digests, whose sequence and protein origin has been elucidated in detail by mass spectrometry. The results show the potential of the developed HILIC × RP-MS platform for in depth peptide mapping of microalgae and its possible application to highlight the products of gastro-intestinal digestion of other microalgae species.