ИСТИНА

The interest to formation of stationary phases that can be used for separating substances of different nature is growing over last years. The majority of mixed-mode resins are based on silica and have limited chemical stability. Attachment of hydrophilic positively charged functional layer to the surface of poly(styrene-divinylbenzene) (PS-DVB) is promising for creating mixed-mode stationary phases that are stable over entire pH range. The presence of aromatic substrate is responsible for the separation of hydrophobic analytes in RP HPLC mode, hydrophilic compounds are retained on hydrophilic groups of functional layer in HILIC mode, and the presence of quaternary ammonium groups provides the separation of anions in suppressed ion chromatography (IC) mode. The work proposes different ways of obtaining mixed-mode stationary phases, such as grafting polyelectrolytes formed in situ from diepoxide and secondary amine, covalent attachment of polyethylenimine, quaternized with glycidol, and combination of these techniques. The prospects of oxidizing double bonds on the surface of PS-DVB and the attachment of hydrophilic layer on the resulting epoxy groups for hydrophilicity increase of mixed-mode phases of different structures were demonstrated. Applicability of mixed-mode stationary phases for determining analytes of different charge and hydrophilicity was shown. Obtained resins allowed the simultaneous determination of 21 anions with efficiency up to 38000 tp/m including inorganic anions, alkylphosphonic, haloacetic, and other organic acids in IC mode. Mixed-mode resins were also able to separate water-soluble vitamins, amino acids, sugars, nucleobases and nucleosides in HILIC mode and fat-soluble vitamins, alkylbenzenes, chloro- and nitrophenols in RP HPLC mode.