ИСТИНА

Hydrophilic interaction liquid chromatography (HILIC) is a promising tool for determination of diverse polar compounds in complex samples of various nature. Plenty of interactions take place resulting in solute retention in this chromatographic system of polar stationary phase and water-organic solvent mixture. It is believed that the main types of retention mechanisms in HILIC are partitioning, adsorption and electrostatic interactions. The ratio of these mechanisms depends on the nature of solute and stationary phase, and mobile phase composition. The in-depth understanding of retention mechanism, and as a result understanding of the approaches for managing selectivity, is crucial for the development of HILIC method.Thus, the aim of the work was a systematic evaluation of three main types of mechanisms for different solute-adsorbent-eluent compositions using linear models lgk’=f(mobile phase parameter) corresponding to the mechanisms. The test analytes represented groups of strong and weak acids and bases differing by hydrophilicity. We used commercially available and homemade stationary phases with various functional groups, including unmodified silica, amino, diol, and zwitterionic phases. The mobile phase composition (acetonitrile content, pH and counterion concentration) was varied. Independent variation of mobile phase pH and eluting ion concentration allowed to clearly demonstrate the changes of electrostatic interactions between analyte and stationary phase caused by the changes of their ionization state. The influence of pH on partitioning and adsorption, and of acetonitrile content on electrostatic interactions was also shown. The influence of the nature of adsorbent’s functional groups on the ratio of the mechanisms was indicated.