A new solid-state pH sensor and its application in the construction of allsolid-state urea biosensor

A new solid-state pH sensor is developed using neutral poly(3-cyclohexyl th iophene) assembled over a Pt disk electrode. The new sensor is developed fo llowing two different approaches; 1) the neutral poly(3-cyclohexyl thiophen e) dissolved in chloroform and subsequent coating on to a Pt disk electrode ; 2) the neutral polymer is incorporated into plasticized poly(vinyl chlori de) matrix membrane. In both cases the polymer modified electrode is sensit ive to pH and a reversible super Nerstian behavior is observed. The typical response of the pH sensor and its reversibility are reported. The polymer coated electrode is subsequently used to construct an all solid-state urea sensor. The construction of this new urea sensor involves the following two major steps; a) 20 mu L of urease solution (40 mg/mL) is allowed to assemb le overnight at 4 degrees C over neutral poly (3-cyclohexyl thiophene) modi fied electrode; b) an organically modified sol-gel layer is allowed to form over the urease adsorbed polymer modified electrode. The new solid-state u rea sensor provides excellent reproducibility of the measurements and is st able for 3 months when stored at 4 degrees C under dry condition. The typic al response of the solid-state urea sensor and the calibration plot of urea analysis are reported.