Article

Trace Copper Ion Detection by the Suppressed Decolorization of Chromotrope 2R Complex

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Abstract

Chromotrope 2R (CR) is a monoazo dye, which can be easily degraded under ultraviolet C (UVC) light irradiation. However, the degradation extent of CR is suppressed after it is chelated with Cu2+ ions, forming a coordination complex (Cu2+-CR). This phenomenon was developed as a novel method for the quantitative detection of Cu2+ ions, which is based on determining the change of the absorbance (DA, the absorbance of Cu2+-CR complex subtracted by that of CR after UVC light irradiation) by UV–visible absorption spectrum. Under the optimal detection conditions, the DA at 509 nm highly depends on the concentration of Cu2+ ions in the range from 5.0 *10-9 to 1.0*10-6 M as expressed by the following equation: DA = 0.3066 + 0.03605 lg c with the correlation coefficient of r = 0.9912. The limit of detection (ld) is 3.4 nM as calculated by the formula 3o= 0.3066 + 0.03605 lg ld. This method provides affordable and selective detection of Cu2+ ions and was used to detect the Cu2+ ions in a human hair sample.

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We have developed a simple and homogeneous fluorescence assay, comprised of 3-mercaptopropionic acid (MPA) and DNA-Cu/Ag nanoclusters (NCs) in aqueous solution, for the detection of Cu(2+) ions. The fluorescence of the DNA-Cu/Ag NCs was quenched by MPA, which was recovered in the presence of Cu(2+) ions. This MPA-induced fluorescence quenching arises through changes in the DNA conformation that occur after interactions between MPA and the Cu/Ag clusters. The MPA-induced fluorescence quenching displayed typical characteristics in Stern-Volmer plots; it followed a static quenching mechanism. The presence of Cu(2+) ions resulted in the oxidation of MPA to form a disulfide compound, leading to recovery of the fluorescence of the DNA-Cu/Ag NCs. The fluorescence of the DNA-Cu/Ag NCs in the presence of MPA increased upon increasing the concentration of Cu(2+) ions over the range from 5 to 200 nM. The DNA-Cu/Ag NC probe provided the limit of detection (at a signal-to-noise ratio of 3) for Cu(2+) ions of 2.7 nM, with high selectivity (by at least 2300-fold over other tested metal ions). We validated the practicality of using this probe for the detection of Cu(2+) ions in environmental samples through analyses of Montana soil and pond water samples.
Article
A Cu(2+)-specific colorimetric sensor 1, which is stabilized by an intramolecular hydrogen bonding, was designed and developed. The color of 1 changes from purple to blue on addition of 1.0 muM Cu(2+) in aqueous buffer solution, which can be detected by the naked eye. The analytical detection limit for Cu(2+) by the naked eye is as low as 1.0 muM. The stoichiometry for 1 and Cu(2+) in complex is 2:1 in aqueous solution.
Article
An effective dual-DNAzyme-based unimolecular probe design employing intramolecular signal transduction is demonstrated. The probe is composed of three domains: a DNA-cleaving DNAzyme, a substrate, and an HRP-mimicking DNAzyme. When the probe meets its target, cleavage of the substrate by the DNA-cleaving DNAzyme activates the HRP-mimicking DNAzyme, producing a colorimetric signal. The Cu(2+)-dependent DNAzyme engineered to demonstrate this design revealed a sensitivity corresponding to 65 ppb, which is sufficient to detect Cu(2+) in drinking water. The new probe has excellent selectivity toward Cu(2+). This three-component design is simple and easy to engineer. It may provide the basis for future development of other nucleic acid-based probes for toxicological and environmental monitoring.
Article
Procedures are described for measurement of dissolved copper with long pathlength Teflon AF-2400 liquid core waveguides. Using a 4.4 m waveguide, absorbance versus concentration is linear for copper concentrations between 1 and 160 nM. The molar absorbance of copper complexed with bathocuproine disulfonate is nearly identical for pathlengths between 1 cm and 4.4 m. Our 4.4 m waveguide system provided a 0.4 nM detection limit with no sample preconcentration. The methods developed in this study have been used to determine copper concentrations in natural seawater, river water, and commercial drinking water.
Article
Methods for the direct determination of copper and cadmium in seawater were described using a graphite furnace atomic absorption spectrometer (GFAAS) equipped with a transversely heated graphite atomizer (THGA) and a longitudinal Zeeman effect background corrector. Ammonium nitrate was used as the chemical modifier to determine copper. The mixture of di-ammonium hydrogen phosphate and ammonium nitrate was used as the chemical modifier to determine cadmium. The matrix interference was removed completely so that a simple calibration curve method could be applied. This work is the first one with the capability of determining cadmium in unpolluted seawater directly with GFAAS using calibration curve based on simple aqueous standards. The accuracy of the methods was confirmed by analysis of three kinds of certified reference saline waters. The detection limits (LODs), with injection of a 20-mul aliquot of seawater sample, were 0.06 mug l(-1) for copper and 0.005 mug l(-1) for cadmium.
Article
(Figure Presented) Just one click, and the color's gone: In the presence of Cu2+ with sodium ascorbate as a reductant, gold nanoparticles that have azide- and alkyne-terminated groups undergo aggregation as the result of CuI-catalyzed click chemistry. This process can be monitored by eye without the aid of instruments (NPs=nanoparticles).
Article
Formation of a luminescent device by the Huisgen 1,3-dipolar cycloaddition reaction between a Eu(III) complex and dansyl azide is reported. This reaction is catalyzed by a common biological copper(I) complex [GS--Cu(I)], and the resultant copper(I) catalytic sensor shows a 10-fold enhancement of europium luminescence emission.
Article
A new infrared sensing scheme based on an evanescent wave was proposed in this work for selective detection of copper ion in aqueous solutions. This sensing scheme is based on the band-shifting technique to overcome the limitation that metal ions do not absorb IR radiation. To demonstrate that the proposed mechanism is feasible, both theoretical considerations and practical examination of copper ions in aqueous solutions were investigated. The IR sensor was constructed by surface modification with L-(-)proline to selectively interact with copper ions by formation of stable square-planar complexes. After complexation, the absorption bands of the immobilized L-(-)proline exhibits a band shift and could be used to monitor the quantity of metal ions in aqueous solutions. To immobilize L-(-)proline on the surface of a sensing element and increase the stability of the modified phase in aqueous solutions, poly(vinylbenzyl chloride) was coated onto the sensing element for further immobilization of L-(-)proline. A sensitive and a water-stable L-(-)proline phase was obtained. This sensing phase is selective and sensitive to copper ions due to the large formation constant between the copper ions and L-(-)proline. Factors, such as the copper ion concentration, response time, solution pH, long-term stability, regeneration efficiency, and the matrix effect, were investigated. Results indicated that the pH effect was significant but could be controlled by buffering the sample solutions. Using the optimal conditions found in this work, the detection limit could be lower than 0.7 microM and the linear regression coefficients in standard curves could be higher than 0.99 for a concentration range from 5 to 200 microM.
Article
Copper deficiency is an established cause of hematological abnormalities but is frequently misdiagnosed. Copper deficiency can present as a combination of hematological and neurological abnormalities and it may masquerade as a myelodysplastic syndrome. We reviewed the records of patients with hypocupremia and hematologic abnormalities identified between 1970 and 2005. Patients with hypocupremia unrelated to copper deficiency (e.g. Wilson's disease) were excluded. Forty patients with copper deficiency and hematological abnormalities were identified. Ten patients (25%) had undergone bariatric (weight reduction) surgery and an additional 14 patients (35%) had undergone surgery on the gastrointestinal tract, most commonly gastric resection. In 12 cases, no cause for copper deficiency was identified. Anemia and neutropenia were the most common hematologic abnormalities identified and the majority of the patients also had neurologic findings, most commonly due to myeloneuropathy. Abnormalities observed on bone marrow examination including vacuoles in myeloid precursors, iron-containing plasma cells, a decrease in granulocyte precursors and ring sideroblasts may be valuable clues to the diagnosis. Copper deficiency is an uncommon but very treatable cause of hematologic abnormalities.
Article
There has been steadily growing interest in the participation of metal ions (especially, zinc, copper, and iron) in neurobiological processes, such as the regulation of synaptic transmission. Recent descriptions of the release of zinc and copper in the cortical glutamatergic synapse, and influencing the response of the NMDA receptor underscore the relevance of understanding the inorganic milieu of the synapse to neuroscience. Additionally, major neurodegenerative disorders, including Alzheimer's disease and Parkinson's disease, are characterized by elevated tissue iron, and miscompartmentalization of copper and zinc (e.g. accumulation in amyloid). Increasingly sophisticated medicinal chemistry approaches, which correct these metal abnormalities without causing systemic disturbance of these essential minerals, are being tested. These small molecules show promise of being disease-modifying.
Article
In the present paper, a new spirobenzopyran derivative was synthesized and applied in simultaneously colorimetric and fluorescence ratiometric detections of Cu2+. In contrast to the virtually photochromic character of the common spirobenzopyrans in most organic solvents, this spirobenzopyran is colorless in organic aqueous solution even irradiating by ultraviolet light. The formation of red merocyanine in an ethanol-aqueous solution is only induced by Cu2+ coordination. Furthermore, the closed form of the spirobenzopyran is highly fluorescent. Upon complexation with Cu2+, it displays not only decreasing in the initial fluorescence emission band but also appearing in a new emission at long wavelength. Thus, the Cu2+ quantitative measure can be achieved by fluorescence ratiometry. With the optimum conditions described, the Cu2+ concentration can be determined from 5.13 x 10(-7) M to 3.81 x 10(-4) with a detection limit of 1.06 x 10(-7) M. Both the color and the fluorescence changes of the spirobenzopyran are extremely specific for Cu2+ over biologically relevant substrates, which meet the selectivity requirements for biomedical application. Serum divalent copper values were determined using this spirobenzopyran, which fell into the normal range of the content reported in the literature and were in good agreement with those obtained by atomic absorption spectroscopy. The combined data from fluorescence titrations and 1H NMR measurements indicate that the new emission of the spirobenzopyran generated by Cu2+ is the result of the metal-induced ring opening and conformation restriction by Cu2+ liganding with the opened merocyanine form and the subsequent reduction of the intramolecular charge transfer of the merocyanine.