CELLULOSE-BASED BULK PH OPTOMEMBRANES

The paper presents an efficient technique for the preparation of pH-se nsitive bulk optomembranes for fiber optic chemical sensors (FOCS). Th e method is based on the physical entrapment of the reagent molecules in the bulk of cellulose acetate membranes. The durable immobilization of a pH indicator is achieved by the addition of an appropriate ion-b alance reagent to the cellulose matrix. The composition and thickness of the pH-sensitive layer containing Congo red (basic pH chromoionopho re) were optimized. The best performance (dynamic range, response time ) were obtained for 10 mu m membranes containing 30% of a wetting agen t and a hydrophilic plasticizer. The efficiency of this immobilization technique was also verified for unmodified acidic pH indicators: Brom othymol blue and Thymol blue. (C) 1998 Elsevier Science S.A. All right s reserved.