Amino-Functionalized Monolithic Poly(glycidyl methacrylate-co-divinylbenzene) Ion-Exchange Stationary Phases for the Separation of Oligonucleotides

Abstract

Monolithic capillary columns were prepared by thermal initiated copolymerization of glycidyl methacrylate (GMA) and divinylbenzene (DVB) inside silanized 200 µm i.d. fused silica capillaries. Polymerization mixtures containing different amounts of porogen (1-decanol and tetrahydrofuran (THF)) and different ratios of monomer and crosslinker were used for synthesis. For characterization the pore size distribution profiles of the resulting monoliths were determined by mercury intrusion porosimetry. The morphology of the copolymer was investigated by scanning electron micrographs (SEM). A high linear dependence between flow rate and pressure drop was achieved which indicates that the polymer is pressure-stable even at high flow rates. After characterization the produced GMA-DVB monoliths, which contain reactive epoxide groups, were modified by reaction with diethylamine to obtain a poly(3-diethylamino-2-hydroxypropyl methacrylate-co-divinylbenzene) ion-exchange monolithic stationary phase. The synthesized monoliths contain ionizable amino groups that are useful for anion-exchange chromatography (AEC). Poly(3-diethylamino-2-hydroxypropyl methacrylate-co-divinylbenzene) monolithic columns allowed a fast and highly efficient separation of a homologous series of phosphorylated oligothymidylic acids [d(pT)12-18]. Since durability is an important parameter of chromatographic column characterization, the separation performance for d(pT)12-18 in a freshly produced capillary column and on the same column after 100 chromatographic runs was compared.