Anion Analysis 1 - Simultaneous Determination of Chloride and Bromide by a Fluorescence Quenching Method

Introduction Fluorescence spectrophotometry in its pure form is inherently a very sensitive analytical method. Single molecules have been observed in fluorescence microscopy due to the very low signal in the absence of fluorescent analytes (often referred to as zero background) and the possibility of producing many photons from a single molecule using a very bright excitation source. There are two types of fluorometric methods used in the determination of inorganic species. Direct methods involve the formation of a fluorescent chelate and the measurement of its fluorescence. Indirect methods are based on the quenching of a fluorescent indicator by the species being determined. The latter technique has been most widely used for anion analysis. Note that the indirect method (used here) is not a zero background method as regards the analyte. The quenching, a decrease in fluorescence intensity, of a fluorescent indicator (usually an aromatic organic dye) can be described by the Stern Volmer equation: