title: Selective extraction and release using (EDTA-Ni)-layered double hydroxide coupled with catalytic oxidation of 3,3',5,5'-tetramethylbenzidine for sensitive detection of copper ion.
abstract: Copper is an important heavy metal in various biological processes. Many methods have been developed for detecting of copper ions (Cu(2+)) in aqueous samples. However, an easy, cheap, selective and sensitive method is still desired. In this study, a selective extraction-release-catalysis approach has been developed for sensitive detection of copper ion. Ethylenediaminetetraacetic acid (EDTA) chelated with nickel ion (Ni(2+)) were intercalated in a layered double hydroxide via a co-precipitation reaction. The product was subsequently applied as sorbent in dispersive solid-phase extraction for the enrichment of Cu(2+) at pH 6. Since Cu(2+) has a stronger complex formation constant with EDTA, Ni(2+) exchanged with Cu(2+) selectively. The resulting sorbent containing Cu(2+) was transferred to catalyze the 3,3',5,5'-tetramethylbenzidine oxidation reaction, since Cu(2+) could be released by the sorbent effectively and has high catalytic ability for the reaction. Blue light emitted from the oxidation product was measured by ultraviolet-visible spectrophotometry for the determination of Cu(2+). The extraction temperature, extraction time, and catalysis time were optimized. The results showed that this method provided a low limit of detection of 10nM, a wide linear range (0.05-100μM) and good linearity (r(2)=0.9977). The optimized conditions were applied to environmental water samples. Using Cu(2+) as an example, this work provided a new and interesting approach for the convenient and efficient detection of metal cations in aqueous samples.
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Sheng
authors.initials: S
authors.lastname: Tang
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Yuepeng
authors.initials: Y
authors.lastname: Chang
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
authors.forename: Guo Hui
authors.initials: GH
authors.lastname: Chia
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore; National University of Singapore Environmental Research Institute, T-Lab Building #02-01, 5A Engineering Drive 1, Singapore 117411, Singapore; Tropical Marine Science Institute, National University of Singapore, S2S, 18 Kent Ridge Road, Singapore 119227, Singapore. Electronic address: chmleehk@nus.edu.sg.
authors.forename: Hian Kee
authors.initials: HK
authors.lastname: Lee
mesh_terms: D001560:Benzidines / Q000737:chemistry*; D002384:Catalysis; D002413:Cations, Divalent / Q000032:analysis / Q000302:isolation & purification; D003300:Copper / Q000032:analysis* / Q000302:isolation & purification; D060766:Drinking Water / Q000032:analysis; D004492:Edetic Acid / Q000737:chemistry*; D004784:Environmental Monitoring / Q000379:methods; D006878:Hydroxides / Q000737:chemistry*; D057230:Limit of Detection; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry*; D010084:Oxidation-Reduction; D045483:Rivers / Q000737:chemistry; D012623:Seawater / Q000032:analysis; D052616:Solid Phase Extraction / Q000379:methods*
chemical_list: D001560:Benzidines; D002413:Cations, Divalent; D060766:Drinking Water; D006878:Hydroxides; C021758:3,3',5,5'-tetramethylbenzidine; D003300:Copper; D009532:Nickel; D004492:Edetic Acid
keywords: 3,3′,5,5′-Tetramethylbenzidine; Copper ion; Ethylenediaminetetraacetic acid; Layered double hydroxide; Selective extraction