Dual photometric-contactless conductometric detector for capillary electrophoresis

A combined detection system involving simultaneous absorption photometric and contactless conductometric measurements at the same place of the fused-silica separation capillary has been designed. The measurements are mutually independent and the static and dynamic properties of the detection are fully comparable with those characteristic of individual photometric and conductometric detectors. Optical fibers are used to carry the photometric signal, whereas the conductometric signal is obtained from electrodes placed on the outer side of the capillary wall at a frequency in a range from 100 to 500kHz. The detector is especially advantageous in analyses of mixtures containing both organic and inorganic ions. The limits of detection (LOD) and dynamic (DR) or linear dynamic (LDR) ranges have been determined for potassium ion (conductometry) and salicylate (photometry), obtaining 3.5 and 20µM for the LOD, 0.1-5000 and 50-10000µM for the DR, and 10-50000 and 50-40000µM for the LDR, for K+ and salicylate, respectively. The reliability of the detector was demonstrated on an analysis of a real sample of an infusion solution (Vishnevski solution).