Self-referencing fiber-optic fluorescence sensor for turbid samples

A novel single-fiber optical sensor was developed to measure solute fluorescence and to estimate a correction factor to compensate for the signal attenuation caused by suspended particles. The latter was effected using a reference fluorescer mounted beyond the end of the fiber tip. This sensor is intended for monitoring of contaminants in model aquifers and is adaptable to held use. The suspensions tested were Ca-montmorillonite, polystyrene latex beads, and silica. A tracer dye was used as the test analyte so that sorption of the sample onto the suspended particles would be negligible. The relationship between the reference fluorescence attenuation and the analyte attenuation agreed approximately with geometric prediction and could be determined without knowledge of the particle size distribution or the type of particles used. The results indicated that corrected solute fluorescence intensities could be obtained by successively sending an analyte excitation wavelength and a reference excitation wavelength into the fiber-optic sensor.