FRET-based sensor for imaging chromium(III) in living cells

On the basis of fluorescent resonance energy transfer from 1,8-naphthalimide to rhodamine, a fluorophore dyad (FD8) containing rhodamine and a naphthalimide moiety was synthesized as a Cr3+-selective fluorescent probe for monitoring Cr3+ in living cells with ratiometric fluorescent methods.     

嵌段分子筛聚合材料P123-SH萃取分离-石墨炉原子吸收光谱法分析痕量铬的形态

研究了嵌段分子筛聚合材料P123-SH萃取分离-石墨炉原子吸收光谱法对尿中痕量铬的形态分析方法,探讨了嵌段分子筛聚合材料P123-SH吸附铬的原理和最佳条件。在pH 7.0、常温下,Cr3+和Cr(Ⅵ)被很好的分离,且Cr3+可被该材料定量吸附,其吸附容量为6.15 mg/g。吸附的Cr3+可用2 mol/L的HCl洗脱,用石墨炉原子吸收法测定洗脱下来的Cr3+,往溶液中加入0.1%抗坏血酸将Cr(Ⅵ)还原为Cr3+测总铬,Cr(Ⅵ)含量为总铬减去Cr3+,方法测定Cr3+的检出限为0.011μg/L(3σ,n=11),线性范围为0.1～10μg/L,加标回收率在94%～106%之间,对0.50μg/L的Cr3+溶液平行测定7次,RSD为3.6%。方法可应用于生物样品和环境样品中痕量铬的形态分析。     

On-line electrochemical oxidation of Cr(III) for the determination of total Cr by flow injection-solid phase spectrophotometry.

A novel on-line oxidation method of ultra-trace Cr(III) dissolved in natural water has been developed using a flow electrolysis cell. This method was successfully applied to the determination of the total Cr concentration by flow injection-solid phase spectrophotometry using diphenylcarbazide as a coloring agent. With the applied potential of 1.35 V (vs. Ag/AgCl) and the flow rate of 0.80 cm(3) min(-1), Cr(III) was quantitatively oxidized to Cr(VI) at room temperature. The total Cr concentration of sub-microg dm(-3) in 3 - 4 samples could be determined within 1 h using an aqueous sample volume of 7.1 cm(3). The analytical values of the total Cr concentration in natural water were in good agreement with those obtained by ICP-MS. The detection limit of the proposed method was 0.014 microg dm(-3) (3sigma, n = 7). This method could be applied to the specific determination of Cr(III) and Cr(VI) in river water samples.     

Speciation of Cr(III) and Cr(VI) in water after preconcentration of its 1,5-diphenylcarbazone complex on amberlite XAD-16 resin and determination by FAAS

A simple and sensitive method for the speciation, separation and preconcentration of Cr(VI) and Cr(III) in tap water was developed. Cr(VI) has been separated from Cr(III) and preconcentrated as its 1,5-diphenylcarbazone complex by using a column containing Amberlite XAD-16 resin and determined by FAAS. Total chromium has also been determined by FAAS after conversion of Cr(III) to Cr(VI) by oxidation with KMnO₄. Then, Cr(III) has been calculated by subtracting Cr(VI) from the total. The effect of acidity, amount of adsorbent, eluent type and flow rate of the sample solution on to the preconcentration procedure has been investigated. The retained Cr(VI) complex was eluated with 10 ml of 0.05 mol l⁻¹ H₂SO₄ solution in methanol. The recovery of Cr(VI) was 99.7±0.7 at 95% confidence level. The highest preconcentration factor was 25 for a 250 ml sample volume. The detection limit of Cr(VI) was found as 45 μg l⁻¹. The adsorption capacity of the resin was found as 0.4 mg g⁻¹ for Cr (VI). The effect of interfering ions has also been studied. The proposed method was applied to tap water samples and chromium species have been determined with the relative error <3%.     

Fluorescence turn-on chemosensor for Hg~(2+) based on a rhodamine derivative and its application in bioimaging

A fluorescence turn-on chemosensor based on rhodamine B derivative (FD10) has been developed as a highly sensitive chemosensor for Hg2+. A prominent fluorescence enhancement was measured in the presence of Hg2+, which was in agreement with the changes in the absorption spectrum. Furthermore, by means of laser scanning fluorescence microscopy experiments, it was demonstrated that FD10 was cell-permeable and could be used as a fluorescent probe for monitoring Hg2+ in living cells.     

Novel Y-type two-photon active fluorophore: synthesis and application in fluorescent sensor for cysteine and homocysteine

A novel Y-shaped two-photon active material FD3 based on the imidazole core has been synthesized and exhibited intense two-photon excited fluorescence with two-photon absorption cross-section of more than 9000 GM. Importantly, FD3 could be used as a potential two-photon excited fluorescent sensor for cysteine and homocysteine.     

Polyacrylamide gels formed with Cr+3 ion and Cr(acetate)3: Thermodynamically and kinetically controlled crosslinking reactions

The gelation of buffered aqueous Cr⁺³/polyacrylamide (PAAm) solutions has been studied over the pH range 2-11. With Cr⁺³ supplied as Cr(NO₃)₃ and a 7.5% hydrolyzed PAAm the upper limit for gelation was about pH 7, but Cr(acetate)₃/PAAm solutions gelled as high as pH 9. Evidence is presented that the formation of unreactive colloidal Cr(OH)₃(H₂O)₃, rather than polymer crosslinking, is favored thermodynamically for Cr⁺³/PAAm solutions at pH > 7. The crosslinks formed in Cr(acetate)₃/PAAm solutions at pH 7–9 are deduced to be kinetically controlled products. Independent evidence for the kinetic stability of Cr⁺³/PAAm gels above pH 7 has also been obtained. Other observations relevant to the mechanism of crosslinking of PAAm with Cr(acetate)₃ are described.     

Determination of Cr3+, CrO42-, and Cr2O72- in environmental matrixes by high-performance liquid chromatography with diode-array detection (HPLC-DAD)

A high-performance liquid chromatographic method with diode array detection (HPLC-DAD), based on chelation with ammonium pyrrolidinedithiocarbamate (APDC), has been developed for the determination of chromium species. Determination of Cr3+, CrO42-, and Cr2O72- was performed for standards and synthetic environmental matrixes. This method is robust, rugged, and can be used for rapid routine determination of chromium species with high precision and reliability. Sample pretreatment is simple. The method is capable of discriminating not only between Cr(III) and Cr(VI) but also between the chemical forms of Cr(VI) - CrO42- and Cr2O72-. By analysis of numerous samples the method has been shown to be selective, sensitive, and free from matrix interference, which is crucial for the determination of chromium species in difficult-to-analyze environmental matrixes. This method has been validated by means of an interlaboratory study. Although different speciation techniques were used during this study, there was good agreement between results from the two laboratories. The method detection limits were 7 and 4 mg L(-1) for Cr3+ and Cr2O72-, respectively. Recoveries of the analytes from spiked samples were 98% and 100% for Cr3+ and Cr2O72-, respectively. Both were based on a 10-mL sample volume spiked with 0.4 mg L(-1) chromium.     

Isolated heterometallic Cr7Ni rings grafted on Au(111) surface

A study of the deposition of heterometallic antiferromagnetically coupled rings onto gold surfaces is reported. Two new {Cr7Ni} rings, [NH2nPr2][Cr7NiF8(3-tpc)16] (1) (where 3-tpc=3-thiophenecarboxylate) and [nBuNH2CH2CH2SH] [Cr7NiF8(O2CtBu)16] (2) have been made and structurally characterized. They have been deposited from the liquid phase on Au(111) and the adsorbed molecules compared by means of scanning tunneling microscopy (STM) and X-ray photoemission spectroscopy (XPS). In both cases a two-dimensional distribution of individually accessible {Cr7Ni} heterometallic rings on the gold surface has been obtained, exploiting the direct grafting of sulfur-functionalized clusters. There is a competition between the chemisorption of the {Cr7Ni} clusters and a thiolic self-assembled monolayer (SAM) formed by free ligands. In 2, the presence of a single sulfur ligand should force the molecule to graft with the ring axis normal to the surface. The cluster stability in the STM images and the S-2p energy positions demonstrate, for both functionalizations, the strength of the grafting with the gold surface.     

Chromium(III) ion-selective electrode based on 4-dimethylaminoazobenzene

A PVC-based membrane of 4-dimethylaminoazobenzene reveals a Nernstian potentiometric response (with slope of 19.5+/-0.6 mV/decade and a correlation coefficient of 0.999) for Cr(III) over a wide concentration range (1.66 x 10(-6)-1.0 x10(-2) mol dm(-3)). The potential of this electrode is independent of pH in the range of 3.0-5.5. It has a fast response time of about 10 s and was used for a period of 3 months with good reproducibility. The detection limits of this membrane electrode was 8 x 10(-7) M. the proposed electrode has been used as an indicator electrode in the potentiometric titration of Cr(III) with EDTA. This sensor exhibits a very good selectivities for Cr(III) over a wide variety of metal ions.     

Speciation of chromium by selective separation and preconcentration of Cr(III) on an immobilized nanometer titanium dioxide microcolumn

Nanometer titanium dioxide immobilized on silica gel (immobilized nanometer-scale TiO2 particles) was prepared by a sol-gel method and characterized by X-ray diffraction and scanning electron microscopy. The adsorptive behavior of Cr(III) and Cr(VI) on immobilized nanometer TiO2 was assessed. Cr(III) was selectively sorbed on immobilized nanometer TiO2 in the pH range of 7-9, while Cr(VI) was found to remain in solution. A sensitive and selective method has been developed for the speciation of chromium in water samples using an immobilized nanometer TiO2 microcolumn and inductively coupled plasma atomic emission spectrometry. Under optimized conditions (pH 7.0, flow rate 2.0 mL/min), Cr(III) was retained on the column, then eluted with 0.5 mol/L HNO3 and determined by ICP-AES. Total chromium was determined after the reduction of Cr(VI) to Cr(III) by ascorbic acid. The adsorption capacity of immobilized nanometer TiO2 for Cr(III) was found to be 7.04 mg/g. The detection limit for Cr(III) was 0.22 ng/mL and the RSD was 3.5% (n = 11, c = 100 ng/ mL) with an enrichment factor of 50. The proposed method has been applied to the speciation of chromium in water samples with satisfactory results.     

Characterization and X-ray absorption spectroscopic studies of bis[quinato(2-)]oxochromate(V)

A new Cr(V) complex, K[CrVO(qaH3)2].H2O (Ia; qaH3 = quinato = (1R,3R,4R,5R)-1,3,4,5-tetrahydroxycyclohexanecarboxylato(2-)), synthesized by the reaction of K2Cr2O7 with excess qaH5 in MeOH (Codd, R.; Lay, P. A. J. Am. Chem. Soc. 1999, 121, 7864-7876), has been characterized by microanalyses, electrospray mass spectra, and UV-visible, CD, IR, EPR, and X-ray absorption spectroscopies. This complex is of interest because of its ability to act as both a structural and a biomimetic model for a range of Cr(V) species believed to be generated in vivo during the intracellular reduction of carcinogenic Cr(VI). The Na+ analogue of Ia (Ib) has also been isolated and characterized by microanalyses and IR and X-ray absorption spectroscopies. The reaction of Cr(VI) with MeOH in the presence of qaH5 that leads to I proceeds via a Cr(IV) intermediate (observed by UV-visible spectroscopy), and a mechanism for the formation of I has been proposed. DMF or DMSO solutions of I are stable for several days at 25 degrees C, while I in aqueous solution (pH = 4) disproportionates to Cr(VI) and Cr(III) in minutes. The likely structures in the solid state for Ia (14 K) and Ib (approximately 293 K) have been determined using both single-scattering (Ia,b) and multiple-scattering (Ia) analyses of XAFS data. These analyses have shown the following: (i) In agreement with the results from the other spectroscopic techniques, the quinato ligands are bound to Cr(V) by 2-hydroxycarboxylato moieties, with Cr-O bond lengths of 1.55, 1.82, and 1.94 A for the oxo, alcoholato, and carboxylato O atoms, respectively. (ii) The position of an oxo O atom is somewhat disordered. This is consistent with molecular mechanics modeling of the likely structures. The XAFS, EPR, and IR spectroscopic evidence points to the existence of hydrogen bonds between the oxo ligand and the 3,4,5-OH groups of the quinato ligands in the solid state of I.     

同时吸附油和六价铬离子复合材料的制备及性能

以亲油疏水型三元乙丙橡胶(EPDM)作为基体, 焙烧Fe2O3和阴离子交换树脂201Х7作为填料, 利用熔融共混的方法, 制备一种可以同时吸附油和六价铬离子的用于污水处理的复合材料, 这种材料能够悬浮于油水界面处. 当焙烧Fe2O3和阴离子交换树脂的用量比例不同时, 材料吸附性能变化很大. 实验结果表明, 在保证复合材料密度介于油水密度之间的前提下, 随着焙烧Fe2O3含量的增加, 材料的吸油性能不断增大; 随着阴离子交换树脂含量的增加, 材料对六价铬的吸附性能不断增加. 在油水共存体系中, 复合材料对两种污染物的吸附率同时达到最佳时, 两种填料的比例可以确定, 因油品的不同而不同. 在油水共存体系中, 复合材料对油和六价铬的总吸附能力要远大于复合材料分别在单一吸附介质中的吸附能力.     

Fluorescence turn-on chemosensor for Hg<Superscript>2+</Superscript> based on a rhodamine derivative and its application in bioimaging

A fluorescence turn-on chemosensor based on rhodamine B derivative (FD10) has been developed as a highly sensitive chemosensor for Hg²⁺. A prominent fluorescence enhancement was measured in the presence of Hg²⁺, which was in agreement with the changes in the absorption spectrum. Furthermore, by means of laser scanning fluorescence microscopy experiments, it was demonstrated that FD10 was cell-permeable and could be used as a fluorescent probe for monitoring Hg²⁺ in living cells. Supported by the National Natural Science Foundation of China (Grant No. 20801015) and Shanghai Leading Academic Discipline Project (Grant No. B108)     

Chromium speciation in natural waters using serially connected supported liquid membranes

A supported liquid membrane (SLM) method for the speciation of chromium has been developed. The method is based on selective extraction and enrichment of anionic Cr(VI) and cationic Cr(III) species in two serially connected SLM units. Methyltricaprylammonium chloride (Aliquat) and di-(2-ethylhexyl) phosphoric acid (DEHPA), respectively were used as the selective extractants in the membrane liquid. Graphite furnace atomic absorption spectrometry (GFAAS) was utilised for final determination. Optimised conditions for the DEHPA membrane were, sample solution at pH 3, acceptor solution 0.1 M HNO₃ and 10% w/w carrier in kerosene. The corresponding values for the Aliquat membrane were pH 7, 0.75 M HNO₃ and 6% w/w carrier in di-n-hexylether. This gave extraction efficiencies for Cr(III) and Cr(VI) of 90 and 40%, respectively. The method was used to measure the concentration of Cr III and Cr VI in surface water from an abandoned tannery site. Storage experiments at different pH showed that preservation at neutral pH gave almost constant values over a period of one month. At acidic pH (pH=3.0) the concentration of Cr(VI) decreased rapidly while the concentration of Cr(III) increased. The detection limit, expressed as three times the standard deviation of enriched blank samples was 0.01 μg l⁻¹.     

Synthesis and characterization of a chromium(V) cis-dioxo bis(1,10-phenanthroline) complex and crystal and molecular structures of its chromium(III) precursor

The first structurally characterized Cr(V) dioxo complex, cis-[CrV(O)2(phen)2](BF4) (2, phen=1,10-phenanthroline) has been synthesized by the oxidation of a related Cr(III) complex, cis-[Cr(III)(phen)2(OH2)2](NO3)3.2.5H2O (1, characterized by X-ray crystallography), with NaOCl in aqueous solutions in the presence of excess NaBF4, and its purity has been confirmed by electrospray mass spectrometry (ESMS), EPR spectroscopy, and analytical techniques. Previously reported methods for the generation of Cr(V)-phen complexes, such as the oxidation of 1 with PbO2 or PhIO, have been shown by ESMS to lead to mixtures of Cr(III), Cr(V), Cr(VI), and in some cases Cr(IV) species, 3. Species 3 was assigned as [CrIV(O)(OH)(phen)2]+, based on ESMS and X-ray absorption spectroscopy measurements. A distorted octahedral structure for 2 (CrO, 1.63 A; Cr-N, 2.04 and 2.16 A) was established by multiple-scattering (MS) modeling of XAFS spectra (solid, 10 K). The validity of the model was verified by a good agreement between the results of MS XAFS fitting and X-ray crystallography for 1 (distorted octahedron; Cr-O, 1.95 A; Cr-N, 2.06 A). Unlike for the well-studied Cr(V) 2-hydroxycarboxylato complexes, 2 was equally or more stable in aqueous media (hours at pH=1-13 and 25 degrees C) compared with polar aprotic solvents. A stable Cr(III)-Cr(VI) dimer, [Cr(III)(Cr(VI)O4)(phen)2]+ (detected by ESMS), is formed during the decomposition of 2 in nonaqueous media. Comparative studies of the oxidation of 1 by NaOCl or PbO2 have shown that [Cr(V)(O)2(phen)2]+ was the active species responsible for the previously reported oxidative DNA damage, bacterial mutagenicity, and increased incidence of micronuclei in mammalian cells, caused by the oxidation products of 1 with PbO2. Efficient oxidation of 1 to a genotoxic species, [Cr(V)(O)2(phen)2]+, in neutral aqueous media by a biological oxidant, hypochlorite, supports the hypothesis on a significant role of reoxidation of Cr(III) complexes, formed during the intracellular reduction of Cr(VI), in Cr(VI)-induced carcinogenicity. Similar oxidation reactions may contribute to the reported adverse effects of a popular nutritional supplement, Cr(III) picolinate.     

Synthesis and Properties of Novel (Tricarbonyl)(heptalene)chromium Complexes

A number of novel (tricarbonyl)chromium complexes of heptalenes 10 – 13, 16 – 20 and 23 – 25 have been prepared by reaction of the heptalenes with [Cr(CO)₃L₃] (L=NH₃, Py; cf. Schemes 3–6). Surprisingly, the off‐state complexes 17 and 19 , in which the Cr(CO)₃ group complexes on the diester ring, have been obtained with excellent regioselectivity. The directing effect of ester C=O groups on the regioselectivity of the Cr(CO)₃ coordination to heptalene rings has been discussed. These complexes undergo thermal rearrangements via 1,2‐intra‐ring shift and inter‐ring migration of the Cr(CO)₃ fragment to give the thermodynamically more stable on‐state complexes 16 and 27 , respectively (cf. Schemes 8 and 9). The analogous thermal behavior of other prepared complexes has also been investigated. A new procedure for the selective preparation of complexes 10 and 13 , in which the Cr(CO)₃ group is coordinated to the phenyl ring of the styryl substituent has also been developed (Scheme 7). The attachment of the Cr(CO)₃ fragment to the phenyl group has a visible influence on the UV/VIS behavior of the on‐state complexes 10 and 13a , as well as on the photochemical behavior of the DBS isomers 13a / 13b (cf. Scheme 10).     

Linear trichromium complexes with direct Cr to Cr contacts. 2. Compounds with Cr3(dipyridylamide)4(3+) cores

Seven compounds having in common a Cr3(dpa)4(3+) core (dpa = di(2-pyridyl)amide ion) have been prepared and all shown to have an unsymmetrical chain of three Cr atoms. This chain can be described as a pair of quadruply bonded Cr(II) atoms to which a Cr(III) atom is attached. No symmetrical chain has been found, contrary to a previous preliminary report. The seven compounds have been well characterized crystallographically, and their short and long Cr to Cr distances (A, in parentheses) are: 1 [Cr3(dpa)4Cl2]Cl.2CH2Cl2.THF (2.12, 2.47), 2 [Cr3(dpa)4Cl2]AlCl4.CH2Cl2 (2.011, 2.555), 3 [Cr3(dpa)4Cl2]FeCl4.CH2Cl2 (2.009, 2.562), 4 [Cr3(dpa)4Cl2]I3.THF.2H2O (2.08, 2.49), 5 [Cr3(dpa)4Cl2]PF6.2CH2Cl2 (2.08, 2.48), 6 [Cr3(dpa)4(BF4)F]BF4.2CH2Cl2 (1.900, 2.595), 7 [Cr3(dpa)4ClF]BF4.CH2Cl2.C6H14 (2.039, 2.507). Magnetic susceptibility measurements on 1 and 2 reveal mueff = 3.85 +/- 0.05 muB from 10 to 300 K.     

Comparison of a novel thin-layer chromatographic-fluorescence detection method with a spectrofluorometric method for the determination of 7-hydroxycoumarin in human urine.

A novel method for the determination of 7-hydroxycoumarin in human urine which combines thin-layer chromatography (TLC) with fluorescence detection (FD) has been devised. The limit of detection (1 ng/ml) enables determination of 7-hydroxycoumarin after both administration of coumarin and environmental exposure to this fragrance material. When compared to a spectrofluorometric method of analysis, the TLC-FD method proved to be more selective for the analysis of 7-hydroxycoumarin in human urine.     

A novel fluorescent sensor for Cr3+ based on rhodamine-cored poly (amidoamine) dendrimer

A novel poly (amidoamine) (PAMAM) dendrimer, comprising rhodamine B unit in the core and 1-phenyl-3-methyl-5-pyrazolone unit at the periphery, has been synthesized and characterized. The dendrimer shows dramatic increase in its fluorescence intensity in the presence of proton and metal cations, especially in the presence of Cr(3+). The complex formed by dendrimer and Cr(3+) in ethanol solution has also been studied, considering the potential application for Cr(3+) fluorescent sensor. The influence of the unique chemical structure and resulted photoinduced electron transfer, as well as spirolactam ring-opening on the photophysical properties of the product has been investigated.