The sol-gel method offers a possibility of preparing glassy materials at room temperature that that can support the immobilization of different reagents. The sol- gel method is, especially, well suited for thin-film fabrication and electrochemical studies due to their excellent physical and chemical stability and ease with which they can be prepared. The species embedded in the inert and stable solid matrices usually preserve their functional characteristics and do not leach out our leach out very slowly when an appropriate entrapment procedure is used. A renewable three-dimensional chemically modified carbon ceramic electrode containing Ru [(tpy)(bpy)Cl] PF6 was constructed by sol-gel technique. It exhibits an excellent electro-catalytic activity for oxidation of L-cysteine and glutathione at pH range 2-8. Cyclic voltammetry was employed to characterize the electrochemical behaviour of the chemically modified electrode. The electrocatalytic behaviour is further exploited as a sensitive detection scheme for L-cysteine and Glutathione by hydrodynamic amperometry. Optimum pH value for detection is 2 for both L-cysteine and glutathione. The catalytic rate constants for L-cysteine and glutathione were determined, which were about 2.1x103 and 2.5x103 m-1s-1, respectively. Under the optimized condition the calibration curves are linear in the concentration range 5-685 and 5-700 µM for L-cysteine and Glutathione determination, respectively. The detection limit (S/N=3) and sensitivity is 1 µM, 5 nA/µM for L-cysteine and 1 µM, 7.8 nA/µM for glutathione. The relative standard deviation (RSD) for the amperogram's currents with five injections of L-cysteine or Glutathione at concentration range of linear calibration is <1.5%. The advantages of this amperometric detector are: high sensitivity, good catalytic effect, short response time (t<3 s), remarkable long-term stability, simplicity of preparation and reproducibility of surface fouling (RSD for six successive polishing is 3.
