Trace Analysis of Nonfluorescent Ions by Association with a Fluorescent Probe in the Solid State

Abstract

Selectively excited probe-ion luminescence (SEPIL) is a potentially useful technique for the determination of trace inorganic ions (1). Gustafson and Wright (2) have developed a method for the determination of the fluorescent rare earths by coprecipitation into CaF₂. Fluorescence from a specific crystallographic site of a specific rare earth ion in the lattice can be selectively excited and monitored with a nitrogen-laser-pumped dye laser and a high resolution monochromator. The fluorescence intensity obtained from the solid can then be related to the rare earth concentration in solution prior to precipitation. Detection limits are in the picogram per millileter range, generally below those of comparable methods. This technique can be applied to the analysis of nonfluorescent ions as well (3). If a new crystallographic site is formed by the presence of a nonfluorescent impurity ion residing near a fluorescent probe ion in the lattice, the probe-ion luminescence from that site is dependent upon the nonfluorescent analyte concentration. In the present study, the nonfluorescent rare earths are determined using a fluorescent rare earth, erbium, as the probe (4). In the future, we hope that this technique can be extended to include actinide and transition metal determinations.