Ring-opening metathesis polymerization-derived monolithic strong anion exchangers for the separation of 5′-phosphorylated oligodeoxythymidylic acids fragments

Ring-opening metathesis polymerization (ROMP) derived monoliths were prepared from 5-norborn-2-enemethyl bromide (NBE-CH2Br) and tris(5-norborn-2-enemethoxy)methylsilane ((NBE-CH2O)3SiCH3) within the confines of surface-silanized borosilicate columns (100 mm × 3 mm I.D.), applying Grubbs' first generation benzylidene-type catalyst [RuCl2(PCy3)2(CHPh)]. Two monoliths of the same recipe were converted into strong anion-exchangers applying two different approaches. Monolith I was prepared by a two-step reaction of the poly(NBE-CH2-Br) moieties with diethyl amine forming a weak-anion exchanger followed by reaction (quaternization) with ethyl iodide. Monolith II was prepared via a single-step reaction of the poly(NBE-CH2-Br) moieties with triethyl amine. The resulting monolithic anion-exchangers prepared demonstrated a good aptitude for the anion-exchange separation of single-stranded nucleic acids (ss-DNA). However, monolith II showed superior separation efficiency compared to monolith I indicated by sharper analyte peaks and better resolution values for the 5′-phosphorylated oligodeoxythymidylic acids fragments. On monolith II, the seven fragments of [d(pT)12-18] were baseline separated in less than 9 min. The influence of the buffer pH on the separation efficiency was studied applying a phosphate (0.05 mol/L, pH 7 and 8) and Tris-HCl buffer (0.05 mol/L, pH 9), respectively.