Dual photometric-contactless conductometric detector for capillary electrophoresis

A combined detection system involving simultaneous absorption photometric a nd contactless conductometric measurements at the same place of the fused-s ilica separation capillary has been designed. The measurements are mutually independent and the static and dynamic properties of the detection are ful ly comparable with those characteristic of individual photometric and condu ctometric detectors. Optical fibers are used to carry the photometric signa l, 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 500 kHz. The detector is especially advantageous in analyses of mixtures co ntaining both organic and inorganic ions. The limits of detection (LOD) and dynamic (DR) or linear dynamic (LDR) ranges have been determined for potas sium ion (conductometry) and salicylate (photometry), obtaining 3.5 and 20 muM for the LOD, 0.1-5000 and 50-10000 muM for the DR, and 10-50000 and 50- 40 000 muM for the LDR, for Kf and salicylate, respectively. The reliabilit y of the detector was demonstrated on an analysis of a real sample of an in fusion solution (Vishnevski solution). (C) 2001 Elsevier Science B.V. All r ights reserved.