On-line preconcentration of proteins in capillary electrochromatography using PLOT-columns based on hyperbranched polymers
In our study we have investigated the potential of using of new water-soluble oligosaccharide derivatives hyperbranched polyethylenimin with molecular weight 25 kDa and different degree of modification maltose (PEI-Mal A - 77% modified, PEI-Mal С - 32% modification), as the stationary phase in capillary electrochromatography (CEC) for the separation and concentration of proteins (albumin, insulin, myoglobin, lysozyme). It was synthesized columns with thin porous layer of sorbent on the inner surface of the fused silica capillary (PLOT-column) based on the hyperbranched polymer. We have investigated the possibility of different techniques of on-line preconcentration of analytes to reduce the detection limits of analytes in CEC. We have estimated comparative parameters such as detection limits, efficiency and separation selectivity. It was shown that the combination of sample stacking with electrokinetic injection (FESI) and large volume sample sacking allows achieving the concentration factors up to 1000. Established principles have been tested on real objects (urine, blood serum).