Univerzita Pardubice Fakulta chemicko- technologická

Univerzita Pardubice

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English

Publikace detail

Role of water in aqueous normal phase LC

Autoři: Jandera Pavel | Soukup Jan | Staňková Magda | Janás Petr

Rok: 2015

Druh publikace: ostatní - přednáška nebo poster

Strana od-do: nestránkováno

Tituly:

Jazyk	Název	Abstrakt	Klíčová slova
eng	Role of water in aqueous normal phase LC	In the past years, LC on polar stationary phases with mobile phases containing organic solvent and less than 5–40% water (HILIC) has become the primary method for separation of polar compounds, namely pharmaceuticals or biopolymers. The adsorption of water on fifteen polar stationary phases from acetonitrile-rich aqueous-organic mobile phases was determined using frontal chromatography combined with Karl Fischer titration. The adsorbed amount can be described by Langmuir isotherms and strongly depends on the type of stationary phase. Less than one monomolecular water layer was adsorbed on chemically modified hydrosilated silica at the saturation capacity, while more than one water layer was up-taken on more polar nitrile and diol stationary phases. The strongest affinity to water was observed on zwitterionic stationary phases, where equivalents to 6 - 10 water layers were adsorbed. The adsorbed water participates in the retention process. We compared three model equations for predicting the effect of water in the mobile phase on the sample retention. Respecting the actual concentration of water in gradient elution in calculations, the retention of various polar sample compounds such as phenolic acids and flavones can be accurately predicted from the parameters determined under isocratic conditions. Many polar columns show dual retention mechanisms, HILIC in the acetonitrile-rich mobile phases and RP in more aqueous ones and can be used in alternating two-mode operations for enhancing the separation selectivity and peak capacity. The mobile phase range suitable for HILIC separations increases with increasing column saturation capacity for water. We fabricated zwitterionic sulfobetaine (poly)methacrylate micro-columns by in-situ polymerization using cross-linkers with larger polar molecules, which provide the efficiency of up to 70 000 theoretical plates/m.	HILIC; Dual retention mechanism; Adsorption of water; Gradient elution; Polar columns