Rhod-5N as a fluorescent molecular sensor of cadmium(II) ion.

The photophysical and complexing properties of Rhod-5N (commercially available) in MOPS buffer are reported. This fluorescent molecular sensor consists of a BAPTA chelating moiety bound to a rhodamine fluorophore. Its fluorescence quantum yield is low and a drastic enhancement of fluorescence intensity upon cation binding was observed. Special attention was paid to the complexation with Cd2+, a well known toxic metal ion. Possible interference with other metal ions (Na+, K+, Mg2+, Ca2+, Zn2+, Pb2+) was examined. Rhod-5N was found to be highly selective of Cd2+ over those interfering cations except Pb2+. The limit of detection is 3.1 microg l(-1).