Hydrophilic interaction liquid chromatography (HILIC) provides an alternative approach to effectively separate small polar compounds on polar stationary phases. The purpose of this work was to review the options for the characterization of HILIC stationary phases and their applications for separations of polar compounds in complex matrices. The characteristics of the hydrophilic stationary phase may affect and in some cases limit the choices of mobile phase composition, ion strength or buffer pH value available, since mechanisms other than hydrophilic partitioning could potentially occur. Enhancing our understanding of retention behavior in HILIC increases the scope of possible applications of liquid chromatography. One interesting option may also be to use HILIC in orthogonal and/or two-dimensional separations. Bioapplications of HILIC systems are also presented.Figure

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The goal of the study was to investigate separation mechanism of selected “essential” amino acids (leucine, isoleucine, threonine, tryptophan, proline, and glycine) and vitamin B6 in hydrophilic interaction liquid chromatography (HILIC) with the evaporative light scattering detection. Chromatographic measurements were made on three different HILIC columns: amide-silica (TSK-gel Amide-80), amino-silica (TSK-gel NH2-100), and cross-linked diol (Luna HILIC). The retention behaviour of the analytes was investigated as a function of different binary hydro-organic mobile phases containing 10–90 % (v/v) acetonitrile. The compounds studied were separated under isocratic and gradient conditions. The best results of tested biologically active compounds separation were obtained on the TSK-gel NH2-100 column. TSK-gel NH2 column showed mixed HILIC–ion-exchange mechanism, the highest separation efficiency and better selectivity and resolution for tested analytes than the other studied column, especially at concentration of water in mobile phase lower than 30 % (v/v). Special attention was dedicated to the study of interactions among the stationary phase, mobile phase and the analytes.

The objectives of this study were to investigate the molecular mechanisms of retention of selected fungicides and to classify stationary phases used for RP-HPLC. Chromatographic measurements were made using eight physicochemically diverse HPLC columns which were evaluated for analysis of nine biologically active compounds (strobilurins and triazoles). QSRRs were derived for the logarithms of the retention factors normalized to a hypothetical zero percent organic modifier in the mobile phase, log k W . Structural descriptors of the pesticides were used to describe their chromatographic retention behaviour under the given LC conditions. The next step was the correlation between retention data, log k W , and the structural descriptors of the analytes from molecular modelling.

The goal of the study was to investigate the retention mechanism of selected fungicides in hydrophilic interaction liquid chromatography (HILIC) and per aqueous liquid chromatography (PALC). Chromatographic measurements were made on four physicochemically diversified HILIC columns, which were evaluated for the analysis of nine biologically active compounds, such as strobilurins and triazoles. The effects of the operating conditions on separations were investigated, including the concentration of the organic solvent in the aqueous-organic (acetonitrile) mobile phase. The results were compared, and it was shown that two different retention mechanisms dominate in PALC at low acetonitrile concentrations and in HILIC at high acetonitrile concentrations.