DETERMINATION OF COPPER AT NG ML(-1)-LEVELS BASED ON QUENCHING OF THEEUROPIUM CHELATE LUMINESCENCE

The work describes a novel assay for copper at trace levels. Aqueous C u2+ ions efficiently quench the luminescence of a europium-terpyridine -polyaminopolycarboxylate chelate. Both static and dynamic quenchings were identified and separated by time-resolved luminescence spectrosco py. Single exponential decay was observed throughout, with decay times ranging from 1261 us, in the absence of copper, to 750 mu s at 300 ng ml(-1) copper, reflecting strong dynamic quenching. The calibration g raph obeys the Stern-Volmer equation and is given for the 0-300 ng ml( -1) range. The quenching constant was determined at 1.39 x 10(5) lmol( -1) and the 3SD limit of detection was 7 ng ml(-1). Time-resolved lumi nescence spectroscopy provided additional selectivity for copper by di scriminating static quenching by other heavy metals. Thus, solely stat ic quenchers Zn2+ Cd2+, Hg2+ and Pb2+ did not interfere, whereas the r elative interference by dynamic quenchers was 0.16% (Fe3+), 1.15% (Co2 +), 0.38% (Ni2+), 3.81% (Cr3+) and 3.03% (Mn2+). The quenching mechani sm is discussed. The method appears suitable for industrial and enviro nmental applications. (C) 1998 Elsevier Science B.V.