| Abstract
| - Two redox indicators, thionine and phenosafranine, weresuccessfully immobilized on an affinity chromatographygel and were shown to retain their redox activity.Theformal potentials (versus the standard hydrogen electrode) near pH 7 were determined to be 52 mV forimmobilized thionine and −286 mV for immobilizedphenosafranine. It was demonstrated that the immobilized indicators can be packed in a flow cell and monitoredspectrophotometrically to determine their speciation.Theabsorption spectra and electrochemical behavior of theindicators were only slightly affected by immobilizationonthe gel. For both indicators, immobilization causedtheformal potential to decrease (15−20 mV) and the absorption spectrum to shift to higher wavelengths (20−40 nm)with respect to the free (unbound) indicators. Theseimmobilized redox indicators couple with some redox-active species [Cr(VI), O2, and Fe(II)] that areimportantin environmental samples.
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