Simultaneous determination of cadmium (II) and zinc (II) by molecular fluorescence spectroscopy and multiple linear...

The work that is reported here concerns a method that allows the simultaneous determination of cadmium (II) and zinc (II) in aqueous solution by molecular fluorescence spectroscopy using 9-(1',4',7',10',13'-pentaazacyclopentadecyl)-methylanthracene. For this chemosensor, the fluorophore pi-system is insulated from an azacrown donor by one methylene group. A self-quenching mechanism, resulting from an electron transfer from the nitrogens of the azacrown to the excited aromatic system, essentially precludes fluorescence emission. Fluorescence is restored when cadmium (II) or zinc (II) are chelated by the macrocycle. The difference between the emission spectra profiles of the free chemosensor, the cadmium and the zinc chelates is such that the concentration determination of the two metals and the remaining free chemosensor is possible at the nanomolar scale in only one experiment using a multiple linear regression algorithm. Usefulness and convenience of this simple method is proven by steady state and kinetic quantitative determination experiments.