INVESTIGATION OF POTENTIAL SENSITIVE FLUORESCENT DYES FOR APPLICATIONIN NITRATE SENSITIVE POLYMER MEMBRANES

The applicability of various potential-sensitive dyes (PSD) for optica l sensing of anions is reported. Specifically, nitrate-responsive poly mer membranes have been developed which are composed of a plasticized polymer, an anion exchange catalyst, and a fluorescent dye. On exposur e to nitrate, the fluorescence intensity of such membranes increases, while the wavelengths of the excitation and emission maxima remain vir tually unchanged. The membranes typically are 2-4 mu m thick and exhib it highest sensitivity to nitrate in the 2 to 200 mgl(-1) range. Signa l changes on exposure to 100 mmol/l nitrate can be as high as +300%. T he detection limit is 0.2 mgl(-1). The cationic PSD octadecyl acridine organe was tested in combination with a tin-organic and an indium-org anic anion carrier rather than with tridodecylmethylammonium chloride, but both carriers were found to display no improved selectivity.