Poly(cyclooctene)-based monolithic columns for capillary high performance liquid chromatography prepared via ring-opening metathesis polymerization

Monolithic columns for capillary HPLC were prepared via ring-opening metathesis polymerization (ROMP) from cis-cyclooctene (COE), tris(cyclooct-4-enyl-1-oxy)methylsilane (CL) as monomers, 2-propanol and toluene as porogens and RuCl2(Py)2(IMesH2)(CHC6H5) (Py = pyridine, IMesH2 = 1,3-dimesityl-4,5-dihydroimidazolin-2-ylidene) as initiator within the confines of 200 μm i.d. fused silica columns. For evaluation of the novel monolithic capillary HPLC columns, a protein standard consisting of six proteins in the molecular weight range of 5800–66000 g/mol, i.e. ribonuclease A, insulin, albumin, lysozyme, myoglobin and β-lactoglobulin, was used. Reproducibility of synthesis was checked by determining the relative standard deviation (RSD) in retention times (tR), which was found to be in the range of 2.9–3.9% for all analytes. Variations in polymer kinetics were realized by adding different amounts of free pyridine and had a significant influence on the monolithʹs morphology, the backpressure and retention times. On the contrary, variations in monomer content and COE to CL ratio showed only minor changes on these parameters. Long-term stability of 1000 runs at 50 °C showed excellent stability of the columns and no significant alteration in separation performance was observed in combination with slightly decreased retention times (approx. 1.6–7.2% for all analytes).