In this work, a fluorometric approach for the selective determination of calcium by using CdTe
nanocrystals as chemosensors, was developed. The quantum dots interacted not with the metal, but
with a ligand that also bonded the metal. The fluorescence response was modulated by the extension of
the competitive metal–ligand binding, and therefore the amount of free ligand. CdTe quantum dots
(QDs) with different capping layers were evaluated, as the QDs surface chemistry and capping nature
affected recognition, thus the magnitude of the ensuing fluorescence quenching. The developed
procedure was automated by using a multipumping flow system.
Upon optimization, thioglycolic acid (TGA) and EDTA were selected as capping and ligand,
respectively, providing a linear working range for calcium concentrations between 0.80–3.20 mg L1
,
and a detection limit of 0.66 mg L1
. A quenching mechanism relying on nanocrystal destabilization
upon detachment of surface Cd by the ligand was proposed.