title: Selective binding of NH4 + by redox-active crown ethers: application to a NH4 + sensor.
abstract: Two redox-active crown ethers, (1,1'- bi-2-naphthyl)-23-crown-6 incorporating 9,10-anthraquinone (BNAQ) and 1,4-benzoquinone (BNBQ), were synthesized and employed in the selective binding of NH(4)(+) over K(+). Their applications to NH(4)(+) detection were studied by cyclic voltammetry and amperometry in aqueous media. The results showed that the magnitude of the quinone redox peak decreased linearly as the concentration of NH(4)(+) increased, indicating the formation of BNAQ-NH(4)(+) and BNBQ-NH(4)(+) complexes. Formation constants of BNAQ-NH(4)(+) and BNBQ-NH(4)(+) complexes were determined to be 4.3 x 10(3) and 4.0 x 10(3) M(-1), respectively, which were 2 orders of the magnitude greater than those of BNAQ-K(+) and BNBQ-K(+) complexes. The (1)H NMR titration method carried out in DMSO-d(6) showed that both complexes possessed 1:1 stoichiometry, and association constants were determined to be 648 +/- 35 and 600 +/- 47 M(-1) for BNAQ-NH(4)(+) and BNBQ-NH(4)(+), respectively. Interference effects from other alkali and alkaline earth metal ions in the analysis of NH(4)(+) were also investigated. The BNAQ-modified sensor showed a linear response from 1.0 microM to 1.0 mM for NH(4)(+), and the detection limit was determined to be 0.9 +/- 0.03 microM.
authors.affiliation: Department of Chemistry and Center for Innovative Bio-physio Sensor Technology, Pusan National University, Keumjeong-ku, Pusan 609-735, South Korea.
authors.forename: Md Aminur
authors.initials: MA
authors.lastname: Rahmen
authors.forename: Nak-Hyun
authors.initials: NH
authors.lastname: Kwon
authors.forename: Mi-Sook
authors.initials: MS
authors.lastname: Won
authors.forename: Myung-Ho
authors.initials: MH
authors.lastname: Hyun
authors.forename: Yoon-Bo
authors.initials: YB
authors.lastname: Shim
mesh_terms: D000880:Anthraquinones / Q000138:chemical synthesis / Q000737:chemistry; D016227:Benzoquinones / Q000138:chemical synthesis / Q000737:chemistry; D001665:Binding Sites; D015374:Biosensing Techniques / Q000379:methods*; D043844:Crown Ethers / Q000138:chemical synthesis / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure; D010084:Oxidation-Reduction; D011188:Potassium / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*
chemical_list: C500012:(1,1'- bi-2-naphthyl)-23-crown-6 incorporating 1,4-benzoquinone; C500011:(1,1'- bi-2-naphthyl)-23-crown-6 incorporating 9,10-anthraquinone; D000880:Anthraquinones; D016227:Benzoquinones; D043844:Crown Ethers; D000644:Quaternary Ammonium Compounds; D011188:Potassium