High-performance separation of small inorganic anions on a methacrylate-based polymer monolith grafted with [2(methacryloyloxy)ethyl] trimethylammonium chloride

A glycidyl methacrylate-co-ethylene dimethacrylate monolith in capillary format (100 microm/id) has been grafted with chains of poly([2(methacryloyloxy)ethyl] trimethylammonium chloride (poly-META) and applied to the ion-chromatographic separation of selected inorganic anions. Grafting chains of META onto the generic monolithic scaffold resulted in a monolith with 'electrolyte responsive flow permeability', which manifested as increased permeability in the presence of electrolyte solutions. Using an eluent of 2 mM sodium benzoate and on-column contactless conductivity detection, a test mixture of six common anions was isocratically separated and detected within 12 min, with the first four anions baseline resolved within a retention time window of 3.2 min. Retention time precision was < or = 1.2% for all anions tested. Separation efficiencies of 15,000 N/m were achieved for fluoride at 1 microL/min, with column efficiencies up to 29,500 N/m obtained at a lower flow rate of 100 nL/min. Furthermore, repeatability of the column modification procedure using photografting methods was acceptable, with retention times between replicate columns matching within 9%.