Construction of polymer monolithic columns in polypropylene ink‐pen tubes for separation of proteins by cation‐exchange chromatography

We describe the synthesis of polymer monoliths inside polypropylene tubes from ink pens. These tubes are cheap, chemically stable, and resistant to pressure. UV‐initiated grafting with 5 wt% benzophenone in methanol for 20 min activated the internal surface, thus enabling the covalent binding of ethylene glycol dimethacrylate, also via photografting. The pendant vinyl groups attached a poly(glycidyl methacrylate‐co‐ethylene glycol dimethacrylate) monolith prepared via photopolymerization. These tubes measured 100–110 mm long, with 2 mm of internal diameter. The parent monoliths were functionalized with Na2SO3 or iminodiacetate to produce strong and weak cation exchangers, respectively. The columns exhibited permeabilities varying from 2.7 to 3.3 × 10−13 m2, which enabled the separation of proteins at 500 µL/min and back pressures