TRACE ANALYSIS OF NON-FLUORESCENT IONS BY ASSOCIATIVE CLUSTERING WITH A FLUORESCENT-PROBE

A new method for ultra-trace determination of the nonfluorescent rare earths, La, Ce, Gd, Lu, as well as yttrium and thorium has been developed using the technique of selectively excited probe ion luminescence (SEPIL). An Er3+ ion acts as a fluorescent probe of a CaF2 precipitate to detect the presence of other ions which have coprecipitated into the lattice. Association of the Er3+ ion with a nonfluorescent analyte Ion forms a new crystallographic site in the lattice which can be selectively excited with a tunable dye laser. An aliquot of an unknown solution is added to a solution containing calcium and erbium. When fluoride is added to precipitate CaF2, the erbium and analyte ions coprecipitate. The solid is ignited at a high temperature and then cooled to 13 K to observe fluorescence. Calibration curves are linear over four orders of magnitude with estimated detection limits as low as 4 pg and an RSD of 5 %. © 1979, American Chemical Society. All rights reserved.