Chemical composition of plasma treated polyimide microspheres

Synthetic carbon microspheres for chromatography were obtained from porous copolymer of 4,4′-bis(maleimidodiphenyl)methane (BM) and divinylbenzene (DVB) using arc discharge argon plasma treatment. Chemical structure of the obtained material was determined by elemental analysis, scanning electron microscopy with X-ray detector, acid and base titrations, and atomic absorption spectroscopy. The results suggest that the carbon microspheres contain copper coming from the plasma reactor electrodes. To remove it two complexion agents were used: EDTA and 20% HNO3. Copper can be removed from the surface using these methods. The other amount was permanently built into internal structure of the microspheres.