VOLTAGE-SCAN FLUOROMETRY OF ROSE-BENGAL ION AT THE 1,2-DICHLOROETHANE WATER INTERFACE

A new approach to ion sensing has been presented. Transfer of Rose Bengal (RB) anions from the aqueous phase (W) to the 1,2-dichloroethane (DCE) phase accompanied by the linear sweep of the voltage across the interface is monitored as an increase in fluorescence intensity (F) from RB dianions transferred to the DCE phase. RB in W can be detected down to 20 nM as a peak on a F vs time curve. The peak height (DELTAF(p)) is proportional to the concentration of the dye anion ((b)c(RB)W) up to 2 muM. At higher concentrations, DELTAF(p) vs (b)c(RB)W plot gradually deviates from the straight line. DELTAF(p) is inversely proportional to the square root of the scan rate. The Lambert-Beer's law in conjunction with the concentration profile of transferred ions in the DCE phase accounts for the salient features of the F vs t curves.