Abstract
The factors which influence the pH response range of physically immobilised 3,4,5,6-tetrabromophenolsulfonephthalein (TBPSP) have been studied. The electronic properties of the support matrix cause an increase in the apparent p K a (p K app ) of the immobilised indicator, for electron donating matrices, and a decrease in p K app , for electron withdrawing matrices. A theoretical model, based on the Kubelka-Munk theory, has been formulated and may be used to predict the pH versus reflectance response of TBPSP immobilised on IRA-400 anion-exchange resin. Increasing the immobilised indicator concentration may be used to decrease the p K app and increase the pH sensitivity of the immobilised reagent phase. For TBPSP immobilised on IRA-400 an increase in solution ionic strength causes an increase in p K app which may be described using the Davies equation.
Published Version
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