Detection of nanomolar concentrations of copper(II) with a Tb-quinoline-2-one probe using luminescence quenching or luminescence decay time

We present a time-resolved (gated) luminescence-based method for determination of Cu2+ ions ill microtiterplate format in the nanomolar concentration range using the novel long-lived terbium-[1-methyl-4-hydroxy-3-(N-2-ethyl-5-aminothiadiazolyl-)-carbamoyl-quinoline-2-one] (TbL) complex. The probe works best in Tb:L = 1:2 stoichiometry at neutral pH. The dynamic range is from 10 to 300 nmol L-1 of Cu2+ and the limit of detection is 4.3 nmol L-1. This is the lowest limit of detection achieved so fat for luminescent lanthanide-based probes for copper. It is shown that gating can efficiently Suppress intense. short decaying background fluorescence e.g. that of Rhodamine 6G. The assay call be performed by measurement of luminescence decay time, as well. Stern-Volmer studies indicate that static quenching dominates over dynamic quenching. TbL2 was tested for the effect of some relevant interferents and the assay was applied to the determination of copper in tap water samples. The results achieved were in good agreement with those of a reference method. (C) 2009 Elsevier B.V. All rights reserved.