The modelling and control of the pH response of an immobilised indicator

✍ Scribed by M.E.J. Baker; R. Narayanaswamy

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 467 KB
• Volume: 29
• Category: Article
• ISSN: 0925-4005
• DOI: 10.1016/0925-4005(95)01709-7

✦ Synopsis

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 pK~ (PKapp) of the immobilised indicator, for electron donating matrices, and a decrease in pKapp, 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 pKap p 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 PKap p which may be described using the Davies equation.