A new ion sensor based on fiber optics

A fluorimetric ion sensor based on fiber optics has been developed that employs Rhodamine 6G hydrophobically and electrostatically "trapped" on a Nafion film. The sensor is based on the measurement of quenching or enhancement of the Rhodamine 6G fluorescence by various ions. It was found that ions such as Co²⁺, Cr³⁺, Fe²⁺, Fe³⁺, Cu²⁺, Ni²⁺ and NH⁺₄ rapidly quench the Rhodamine 6G fluorescence at an initial rate that depends on the concentration of the ion. This quenching is then readily reversed by the addition of "reverser" ions such as H⁺, Li⁺, Na⁺, K⁺, Ba²⁺, Ca²⁺, Mn²⁺, Zn²⁺ and Mg²⁺. Again, the initial rate for the attainment of the original fluorescence was found to depend on the concentration of the reverser ion. Therefore, by monitoring the quenching directly the concentration of quencher ions can be determined. In addition, by loading the film with quencher and monitoring the initial rate of return towards the original baseline signal, it is possible to determine non-quenching ions.