FLUOROMETRIC FIBER OPTIC DROP SENSOR FOR ATMOSPHERIC HYDROGEN-SULFIDE

A fluorometric technique based on a liquid drop excited from its inter ior by an optical fiber is described for the measurement of low concen trations of atmospheric hydrogen sulfide (H2S). A drop of alkaline flu orescein mercuric acetate (FMA) solution is suspended in a flowing air sample stream and serves as a renewable sensor. An optical fiber cont ained within the conduit that forms the drop, brings in the excitation beam; the fluorescence emission is measured by an inexpensive photodi ode positioned close to the drop. As H2S in the sample is collected by the alkaline drop, it reacts rapidly with FMA resulting in a signific ant decrease in fluorescence intensity, proportional to the concentrat ion of H2S sampled. The chemistry of this uniquely selective reaction has been well established for many years, the present technique permit s a simple fast inexpensive near real-time measurement with very littl e reagent consumption. Even without prolonged sampling/preconcentratio n steps, limits of detection (LODs) in the double digit ppbv range is readily attainable. (C) 1997 Elsevier Science B.V.