APPLICATION OF POTENTIAL-SENSITIVE FLUORESCENT DYES IN ANION-SENSITIVE AND CATION-SENSITIVE POLYMER MEMBRANES

The applicability of two potential-sensitive dyes (PSDs) for optical s ensing of ions is reported. In particular, nitrate-and nitrite-respons ive as well as potassium-and mercury-sensitive polymer membranes have been developed. In general, membranes are composed of a plasticized po lymer, an ion carrier and a fluorescent dye which optically transduces the extraction of the analyte ion in the polymer matrix. The nitrate sensor membrane is composed of rhodamine B octadecylester and the anio n-exchange catalyst is tridodecylmethylammonium chloride. Both are dis solved in plasticized PVC. The nitrite sensor is based on the same dye and the same polymer matrix but with benzyl-bis(triphenylphosphine) p alladium(II) chloride acting as the nitrite-selective carrier. The pot assium sensor membrane consists of the carbocyanine dye DiOC16(3), val inomycin and a lipophilic berate salt. The mercury 'sensor' is based o n the irreversible decomposition of berate by mercury ions and is comp osed of DiOC16(3) and berate only. All sensor membranes have been inve stigated in terms of signal change, sensitivity, stability, limits of detection and the selectivity for the analyte over interferent ions. T he mechanism of the sensor membranes is discussed on the basis of chan ges of the microenvironment of solvatochromic dyes, which result in an alyte-dependent signal changes.