A method of characterizing a polypeptide, comprising providing a first capillary channel having a separation buffer disposed within, wherein the separation buffer comprises a non-crosslinked polymer solution, a buffering agent, a detergent, and a lipophilic dye. The separation buffer is provided such that, at the time of detection, the detergent concentration in the buffer is not above the critical micelle concentration. The polypeptide is introduced into one end of the capillary channel. An electric field is applied across a length of the capillary channel, which transports polypeptides of different sizes through the polymer solution at different rates. The polypeptide is then detected as it passes a point along the length of the capillary channel.