title: Competitive metal-ligand binding between CdTe quantum dots and EDTA for free Ca2+ determination.
abstract: 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 L(-1), and a detection limit of 0.66 mg L(-1). A quenching mechanism relying on nanocrystal destabilization upon detachment of surface Cd by the ligand was proposed.
authors.affiliation: REQUIMTE, Department of Chemical Sciences, Laboratory of Applied Chemistry, Faculty of Pharmacy, University of Porto, Rua de Jorge Viterbo Ferreira no. 228, 4050-313 Porto, Portugal.
authors.forename: S Sofia M
authors.initials: SSM
authors.lastname: Rodrigues
authors.affiliation: QUIANE, Department of Analytical Chemistry, Faculty of Sciences, University of Valladolid, Paseo de Belén 7, 47011 Valladolid, Spain.
authors.forename: Diego R
authors.initials: DR
authors.lastname: Prieto
authors.affiliation: REQUIMTE, Department of Chemical Sciences, Laboratory of Applied Chemistry, Faculty of Pharmacy, University of Porto, Rua de Jorge Viterbo Ferreira no. 228, 4050-313 Porto, Portugal. Electronic address: dsmribeiro@gmail.com.
authors.forename: David S M
authors.initials: DSM
authors.lastname: Ribeiro
authors.affiliation: QUIANE, Department of Analytical Chemistry, Faculty of Sciences, University of Valladolid, Paseo de Belén 7, 47011 Valladolid, Spain.
authors.forename: Enrique
authors.initials: E
authors.lastname: Barrado
authors.affiliation: REQUIMTE, Department of Chemical Sciences, Laboratory of Applied Chemistry, Faculty of Pharmacy, University of Porto, Rua de Jorge Viterbo Ferreira no. 228, 4050-313 Porto, Portugal.
authors.forename: João A V
authors.initials: JAV
authors.lastname: Prior
authors.affiliation: REQUIMTE, Department of Chemical Sciences, Laboratory of Applied Chemistry, Faculty of Pharmacy, University of Porto, Rua de Jorge Viterbo Ferreira no. 228, 4050-313 Porto, Portugal. Electronic address: joaolms@ff.up.pt.
authors.forename: João L M
authors.initials: JLM
authors.lastname: Santos
mesh_terms: D001667:Binding, Competitive; D019187:Cadmium Compounds / Q000737:chemistry*; D002118:Calcium / Q000032:analysis*; D002413:Cations, Divalent; D060766:Drinking Water / Q000737:chemistry*; D004492:Edetic Acid / Q000737:chemistry; D005453:Fluorescence; D005470:Fluorometry; D006801:Humans; D008024:Ligands; D057230:Limit of Detection; D045663:Quantum Dots / Q000737:chemistry*; D013691:Tellurium / Q000737:chemistry*; D013864:Thioglycolates / Q000737:chemistry
chemical_list: D019187:Cadmium Compounds; D002413:Cations, Divalent; D060766:Drinking Water; D008024:Ligands; D013864:Thioglycolates; C017487:2-mercaptoacetate; D004492:Edetic Acid; D013691:Tellurium; C028337:cadmium telluride; D002118:Calcium
keywords: Calcium; EDTA; Multipumping flow system; Photoluminescence quenching; Quantum dots