Enhanced fluidity liquid chromatography of inulin fructans using ternary solvent strength and selectivity gradients

Highlights: • Enhanced fluidity liquid chromatography was used to separate 47 inulin-type fructans. • A custom ternary gradient instrument was designed to implement selectivity gradients. • Selectivity ternary gradients showed advantage over solvent strength gradients. - Abstract: The value of exploring selectivity and solvent strength ternary gradients in enhanced fluidity liquid chromatography (EFLC) is demonstrated for the separation of inulin-type fructans from chicory. Commercial binary pump systems for supercritical fluid chromatography only allow for the implementation of ternary solvent strength gradients which can be restrictive for the separation of polar polymeric analytes. In this work, a custom system was designed to extend the capability of EFLC to allow tuning of selectivity or solvent strength in ternary gradients. Gradient profiles were evaluated using the Berridge function (RF₁), normalized resolution product (NRP), and gradient peak capacity (P_c). Selectivity gradients provided the separation of more analytes over time. The RF₁ function showed favor to selectivity gradients with comparable P_c to that of solvent strength gradients. NRP did not strongly correlate with P_c or RF₁ score. EFLC with the hydrophilic interaction chromatography, HILIC, separation mode was successfully employed to separate up to 47 fructan analytes in less than 25 min using a selectivity gradient.