title: Ultrasensitive and ultraselective impedimetric detection of Cr(VI) using crown ethers as high-affinity targeting receptors.
abstract: Detection of Cr(VI) by electrochemical methods generally focuses on noble-metal-modified electrodes in strong acid solution using voltammetric techniques. In this work, we report a new strategy to detect Cr(VI) as HCrO4(-) at pH 5.0 in drinking water using electrochemical impedance spectroscopy. The strategy is based on the high-affinity and specific binding of crown ethers (i.e., azacrown) to HCrO4(-), which forms sandwich complexes between them via hydrogen bonds and moiety interactions with K(+) captured by azacrown on its self-assembled Au electrode surface. This then blocks the access of redox probes (Fe(CN)6(3-/4-)) to the self-assembled Au electrode, further resulting in an increase in the electron transfer resistance. This method offers a detection limit of 0.0014 ppb Cr(VI) with a sensitivity of 4575.28 kΩ [log c (ppb)](-1) over the linear range of 1-100 ppb (R(2) = 0.994) at pH 5.0. In addition, the azacrown self-assembled Au electrode has good selectivity for Cr(VI) with good stability and low interferences. This approach can be performed on spiked Cr(VI) as well as real samples. To the best of our knowledge, this is the first example of electrochemical impedimetric sensing that allows ultrasensitive and ultraselective detection of Cr(VI).
authors.affiliation: Nanomaterials and Environmental Detection Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences , Hefei 230031, People's Republic of China.
authors.forename: Juan
authors.initials: J
authors.lastname: Wei
authors.forename: Zheng
authors.initials: Z
authors.lastname: Guo
authors.forename: Xing
authors.initials: X
authors.lastname: Chen
authors.forename: Dong-Dong
authors.initials: DD
authors.lastname: Han
authors.forename: Xiang-Ke
authors.initials: XK
authors.lastname: Wang
authors.forename: Xing-Jiu
authors.initials: XJ
authors.lastname: Huang
mesh_terms: D002857:Chromium / Q000032:analysis*; D043844:Crown Ethers / Q000737:chemistry*; D058266:Dielectric Spectroscopy / Q000379:methods; D060766:Drinking Water / Q000032:analysis*; D057230:Limit of Detection; D008958:Models, Molecular; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D043844:Crown Ethers; D060766:Drinking Water; D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion