Improved capacitively coupled conductivity detector for capillary electrophoresis

The new features of the capacitively coupled contactless conductivity detector for capillary electrophoresis described are higher peak-to-peak excitation voltages for the detector cell of up to 250 V, a pick-up amplifier in close proximity to the electrode and synchronous detection. The electrical performance of the cell was characterized and found to follow readily predictable patterns. The alterations led to a higher signal strength, a better signal-to-noise ratio (S/N) and improved stability. The 3 X S/N detection limits obtained for inorganic cations and anions are in the range 0.1-0.2 muM. For the indirect detection of model compounds of organic cations and anions (aliphatic amines and sulfonates), detection limits of typically 1 muM were achieved.