Retention characteristics of poly(N-(1H-tetrazole-5-yl)-methacrylamide)-bonded stationary phase in hydrophilic interaction chromatography.

A Poly(N-(1H-tetrazole-5-yl)methacrylamide)-bonded (PTZ) stationary phase has recently gained increased attention in hydrophilic liquid chromatography (HILIC) mode for separation of polar compounds and is now commercially available as DCpak PTZ. It is chromatographically characterized in this work. The property of the new column was proven to be the most hydrophilic and acidic by separation of mixtures of purines and pyrimidines (theophylline, theobromine, uridine and 2'-deoxyuridine) in comparison to other two commercial columns Luna HILIC and LiChrospher Diol column. The retention mechanism of the new column was investigated by design-of-experiment (DoE) approach using factorial design models. Water/acetonitrile ratio in the mobile phase, buffer salt concentration and buffer pH were considered factors employing the purine/pyrimidine mixture and glucose derivatives as test samples. The resultant retention model coefficients and contour plots documented the complementary retention and selectivity profiles of the new PTZ column as compared to Diol and Luna HILIC. Moreover, it became clearly evident that the PTZ column exhibits its best HILIC performance at eluent pH ≥ 5 because the NH group in tetrazolyl moiety is dissociated under these conditions. The applicability and great potential of the new HILIC column was proven by the chromatographic separation of complex mixtures of very hydrophilic glucose and glucose derivatives (sucrose, glucosamine, glucuronic acid, glucose-1-phosphate and trehalose, glucose, maltose, glucosamine-6-phosphate, glucose-6-phosphate and gluconic acid δ-lactone) as well as monosaccharides found in N-glycans. It is concluded that the new DCpak PTZ HILIC column could have good prospects for the separation of polar compounds e.g. in metabolomics and glycomics.