Optochemical sensors based on organic polymeric thin or thick films have been investigated considerably in the last decade. Organic indicator dyes and the immobilization technique play important roles in the development and design of the optode. Normally, the immobilization of the indicator is achieved by absorption [17], chemical bonding or physical entrapment into the support materials. However, after immobilization process, the group which is responsible for the chemical interaction is often inaccessible to the analyte. Yet, the immobilized indicator often prohibits the reversible response, as a result of very strong binding of the analyte. Therefore, there is much interest in the immobilization technique, which prevents leaching of indicators, and imparts a rapid response, reversibility and long lifetime to the sensors.