Referenced Capacitively Coupled Conductivity Detector for Capillary Electrophoresis

A dual capacitively coupled contactless conductivity detector for capillary electrophoresis was developed. The two channels are arranged in a bridge configuration so that one of them acts as a reference whose signal is subtracted. This effectively compensates for the baseline conductivity of the separation buffer so that the electronic zero setting is not necessary. Changes in the buffer composition are automatically accounted for, as are temperature drifts. The system is demonstrated for the detection of inorganic model cations in capillary electrophoresis. Besides the use with two separate capillaries, one of which solely serves as reference, it was also found possible to use a single capillary which is looped back through the reference cell.