Abstract: A method determines the concentration of a chemical of interest in a solution. A permeable membrane is placed in the solution and a ligand is exuded through the membrane to continually renew the ligand at the surface of the membrane which is in contact with the solution. Complexes of the ligand with the chemicals of interest are formed where the ligand renewed membrane is in contact with the solution. Illuminating the ligand renewed membrane with radiation from a distance from the membrane induces a fluorescence by the formed complexes on the ligand renewed membrane by the illuminating radiation. The fluorescence from the illuminated complexes on the ligand renewed membrane are detected from a distance from the membrane to provide a determination of the concentration of the chemical of interest in the solution.

Abstract: A fiber optic based chemical sensor detects chemical species in solution. A fluorogenic indicator is forced through an ultrafiltration membrane into an analyte solution. Complex formation between indicator molecules and target ions occurs at the membrane-solution interface where light from a bifurcated fiber optic cable stimulates fluorescence. Fluorescent emission from a sample is transmitted back up the fiber optic cable to a linear photo diode detector. The sensor responds linearly to increasing and decreasing concentration changes on time scales of one second. Chemical modification of an indicator solution enhanced sensitivity.