Optical sensor for seawater salinity

An optical sensor for the measurement of salinity in seawater has been deve loped. It is based on a chloride-quenchable fluorescent probe (lucigenin) i mmobilized on a Nafion film. Two approaches for measuring salinity via chlo ride concentration are presented. In the first, a change in salinity corres ponds to a change in the fluorescence intensity of lucigenin. In the second , the fluorescence intensity information is converted into a phase angle in formation by adding an inert phosphorescent reference luminophore (a ruthen ium complex entrapped in poly(acrylonitrile) beads). Under these conditions , the chloride-dependent fluorescence intensity of lucigenin can be convert ed into a chloride-dependent fluorescence phase shift which serves as the a nalytical information. This scheme is referred to as dual lifetime referenc ing (DLR). The sensor was used to determine the salinity in seawater and br ackish water of the North Sea.