Comparison of Online Comprehensive HILIC x RP and RP x RP with Trapping Modulation Coupled to Mass Spectrometry for Microalgae Peptidomics

In this work, two online comprehensive two-dimensional liquid chromatography platforms, namely Hydrophilic interaction liquid chromatography x Reversed phase (HILIC x RP) and Reversed phase x Reversed Phase (RP x RP) coupled to mass spectrometry, were compared for the analysis of complex peptide samples. In the first dimension, a HILIC Amide and C18 Bioshell peptide (150 x 2.1 mm, 1.7 and 2.0 mu m) columns were selected, while, in the second dimension, a short C18 (50 x 3.0 mm, 2.7 mu m) Bioshell peptide column was used. Two C18 trapping columns (10 x 3.0 mm, 1.9 mu m), characterized by high retention and surface area, were employed as modulation interface in both HILIC x RP and RP x RP methods. The LC x LC platforms were coupled to UV and tandem mass spectrometry detection and tested for the separation and identification of two gastro-intestinal digests of commercial microalgae formulations (Spirulina Platensis and Klamath). Their performances were evaluated in terms of peak capacity, maximum number and properties of identified phycocyanin peptides. Our results showed that the HILIC x RP approach provided the highest peak capacity values (n(c)HILIC x RP: 932 vs.n(c)RP x RP: 701) with an analysis time of 60 min, while the RP x RP approach was able to identify a slight higher number of phycocyanin derived peptides (HILIC x RP: 88 vs. RP x RP: 103). These results point out the flexibility and potential of HILIC x RP and RP x RP based on trapping modulation for peptide mapping approaches.