A NEW FLUORESCENCE TECHNIQUE TO MEASURE THE TOTAL ABSORPTION-COEFFICIENT IN FLUIDS

Conventional fluorescence methods are usually applied for the detectio n of fluorescent substances. A simple technique taking into account no nfluorescent substances has been introduced applying two different sig nals: (i) the linear or conventional fluorescence (CF) occurring at re latively short path-lengths of the exciting radiation in the fluids, a nd (ii) the multi-path saturation fluorescence (MPSF) originating at l ong path-lengths, as in multi-path reflection cells, where the radiati on is fully absorbed by the fluid. A relation between the fluorescence signals and the absorption coefficients of fluorescent and nonfluores cent substances has been theoretically derived. An experiment has been performed with drinking water polluted by aromatic substances. The fl uorescence ratio between CF and MPSF obtained has yielded the total ab sorption. Thus, it has been influenced by both fluorescent and nonfluo rescent substances. In comparison to the conventional absorption techn ique, CF/MPSF has been characterized by high correlations to substance concentrations and has shown a much higher sensitivity. The method of CF/MPSF combines the advantage of fluorescence being very sensitive a nd of absorption spectrometry measuring the total absorption coefficie nt.