A detailed evaluation of the advantages and limitations of online RP-LC×HILIC compared to HILIC×RP-LC for phenolic analysis

Improving the Accuracy of Predictive 2D-LC Optimization Strategies: Incorporation of Simulated Elution Profiles to Account for Injection Band Broadening in Online Comprehensive Two-Dimensional Liquid Chromatography

“…■ EXPERIMENTAL SECTION Materials. Gallic acid (1), catechin (2), caffeic acid (3), vanillic acid (4), rutin (6), resveratrol (8), quercetin (9), naringenin (10), uracil, toluene, formic acid (FA), and HPLC grade methanol (MeOH) were purchased from Sigma-Aldrich (Darmstadt, Germany). Aspalathin (5) and isovitexin (7) were Deionized water was obtained using a Milli-Q water purification system (Millipore, Milford, MA).…”

“…More complete method optimization approaches based on multiobjective or Pareto optimization have been proposed for method development in comprehensive multidimensional LC. − These methodologies generally use algorithms to calculate the performance of separations that would result from all possible combinations of experimental parameters being optimized, within user-specified ranges. Computerization of these approaches allows for a large number of parameters to be simultaneously optimized, and routinely more than 10,000 combinations of experimental parameters are considered during optimization.…”

Impact of conditioning runs on hydrophilic interaction chromatography repeatability and its application as a second dimension in online comprehensive two‐dimensional liquid chromatography

“…The less retained compounds elute from 1 D column just after the 1 D dead time, meanwhile the 2 D column experiences a certain number of conditioning runs. In LC×LC analysis using HILIC as 2 D, the slow 1 D and the fast 2 D typically result in 6 and 12 CRs during the 1 D t 0 [8,21,22,30]. Unfortunately, due to the very wide elution range of the hyaluronic hydrogel solutes in HILIC, combined with the high viscosity of the large amount of water required at the end of the gradient, the 2 D separation extended to 1.1 min.…”

“…Few attempts explored the use of HILIC in gradient mode as a 2 D. In the development of RPLC×HILIC methods for peptides [30] and lipids analysis [22,31], equilibration volumes of three to six volumes (V c ) of HILIC column, as it is typically used for one-dimensional RPLC, were employed. For the analysis of phenolic compounds [21], samples from traditional Chinese medicine [32], and a chiral LC×HILIC method used for amino acid separation [33], equilibration volumes of one-to two-column volumes, typical for second-dimensional RPLC, were utilized. In a recent study, the 2 D HILIC column was equilibrated with less than one-column volume (0.6 V c ) [34], without any distortion of the spots, which indicates repeatability between modulations.…”

“…This improvement is mainly due to the desolvation process promoted by the high proportion of ACN in HILIC, as well as to the ionization mechanisms, such as proton transfer, pKa of analytes in the mobile phase, and mobile phase pH [18]. A comparative study of HILIC×RPLC and RPLC×HILIC for the analysis of phenolic compounds demonstrated the detection of a higher number of compounds when HILIC was used as the 2 D before MS [21]. A similar result was observed in the comparison of RPLC×HILIC and HILIC×RPLC dimension orders for lipid profiling in a biological sample [22].…”