Development of an improved online comprehensive hydrophilic interaction chromatography × reversed-phase ultra-high-pressure liquid chromatography platform for complex multiclass polyphenolic sample analysis

In this study, an improved online comprehensive two-dimensional liquid chromatography platform coupled to tandem mass spectrometry was developed for the analysis of complex polyphenolic samples. A narrowbore hydrophilic interaction chromatography column (150 × 2.0 mm, 3.0 μm, cross-linked diol) was employed in the first dimension, while a reversed-phase column based on monodisperse sub-2 μm fully porous particles (50 × 3.0 mm, 1.9 μm d.p.) with high surface area (410 m2/g) was employed in the second dimension. The combination of a trapping column modulation interface with the high retentive fully porous monodisperse reversed-phase column in the second dimension resulted in higher peak capacity values (1146 versus 867), increased sensitivity, sharper and more symmetrical peaks in comparison with a conventional loop-based method, with the same analysis time (70 min). The system was challenged against a complex polyphenolic extract of a typical Italian apple cultivar, enabling the simultaneous separation of multiple polyphenolic classes, including oligomeric procyanidins, up to degree of polymerization of 10. Hyphenation with an ion trap time-of-flight mass spectrometer led to the tentative identification of 121 analytes, showing how this platform could be a powerful analytical tool for the accurate profiling of complex polyphenolic samples.