Oxidation of diclofenac by permanganate: Kinetics,products and effect of inorganic reductants

The large consumption and discharge of diclofenac (DCF) lead to its frequent detection in surface water and groundwater, posing great threats to humans and ecosystems. This study explored the oxidation kinetics of DCF by permanganate (Mn(VII)), and expounded the underlying reason for the unusual pH-dependency that was unclear in previous studies. The kinetics of DCF analogues (i.e., aromatic secondary amines) by Mn(VII) oxidation were comparatively investigated. Then, a tentative kinetic model involving the formation of an intermediate between Mn(VII) and DCF or its analogues was proposed to fit the pH-rate profile. Since DCF contained two chloro groups, and a carboxyl group which could be ionized by negative electrospray ionization, a precursor ionization scanning approach was used for the first time for detection of N-containing chlorinated oxidation products. New degradation pathways of DCF containing ring opening, carboxylation, carbonylation, electrophilic addition, hydroxylation and dehydrogenation were proposed based on the identified oxidation products. Moreover, it was demonstrated that the introduction of various reducing agents such as Mn(II), Fe(II) and bisulfite significantly improved the oxidation kinetics of DCF by Mn(VII). The positive effects of Mn(II) and Fe(II) were mainly attributed to the accelerated formation of MnO₂ that acted as a catalyst or co-oxidizer contributing to DCF degradation. The presence of bisulfite caused two-stage kinetics, where a sharp drop of DCF concentration followed by a slowdown of DCF removal. In the first stage, potent reactive manganese species (e.g., Mn(III), Mn(V), and Mn(VI)) and sulfate radical were generated during reaction of bisulfite with Mn(VII), whereas bisulfite was depleted fast due to excess Mn(VII) concentrations and the system became the Mn(VII)/MnO₂ system in the second stage. These results provide new insight into reaction mechanism of DCF with Mn(VII) as well as propose a feasible strategy for enhancing the treatment of DCF contaminated water by Mn(VII).     

季铵功能化的金属有机骨架对水中双氯芬酸钠的高效吸附与去除

通过两步合成法制备了季铵功能化的金属有机骨架MIL-101（Cr）即MIL-101（Cr）-NMe₃,并考察了该材料对双氯芬酸钠（DCF）的吸附行为。通过不同浓度的DCF在MIL-101（Cr）-NMe₃吸附剂上的动力学数据,以及在不同温度下的吸附平衡等温线和MIL-101（Cr）-NMe₃吸附剂的重复使用性能考察,发现该材料对DCF的吸附过程符合准二级动力学方程,吸附平衡等温线符合Langmuir等温吸附模型,在20℃下的最大吸附量为310.6 mg/g,5次循环使用后吸附量未明显减少。MIL-101（Cr）-NMe₃对DCF的吸附作用机理可归结为静电相互作用和π-π相互作用,吸附效果远大于未修饰氨基的MIL-101（Cr）。可以预见该材料对水中DCF的去除具有良好的应用前景。     

Nematic-fluid structure in wall-field geometry. II. The direct correlation function

An explicit expression for the wall-nematic direct correlation function (DCF) is obtained for any orientation of the wall with respect to an external orienting field. It is found that inside the surface of the wall, the DCF rapidly tends to a function of the nematogen orientation and depends only on parameters of the bulk fluid. We suggest that the wall-nematic DCF can be used as an ansatz for the colloid-nematic DCF in dilute nematic colloids. The reliability of this ansatz is investigated at different field strengths in both isotropic and nematic regions. Our calculations for spherical colloidal particles show that this approximation is valid for colloidal particles that are large, but well within the physically realistic size range. The ansatz could also be applied to nonspherical colloidal particles.     

Direct correlation function for the square-well potential

An analytical expression of direct correlation function (DCF) for the square-well potential is developed. The development is based on the first-order mean spherical approximation and its extension to the functionality of the existing radial distribution function. The developed DCF is a combination of a special polynomial function introduced in this work. The combination is piecewise in four regions [0, lambda - 1], [lambda - 1,2 - lambda], [2 - lambda,1], and [1,lambda] for lambda < 1.5 or [0,2 - lambda], [2 - lambda, lambda - 1], [lambda - 1, 1], and [1, lambda] for lambda > 1.5. In addition, the DCF is continuous to second-order inside hard core and discontinuous at r=1 and r=lambda outside it. The behavior of DCF is analyzed by some detail calculations.     

Simultaneous determination of diclofenac and its common counter‐ions in less than 1 minute using capillary electrophoresis with contactless conductivity detection

This paper presents a method for fast and simultaneous determination of diclofenac (DCF) and its common counter‐ions (potassium, sodium, and diethylammonium) using CE with capacitively coupled contactless conductivity detection (CE‐C⁴D). On the basis of a single electropherogram (about 50 s), the proposed method allows the determination of the stoichiometry, absolute quantification and evaluation of the degradation degree of the active pharmaceutical ingredient (DCF). A linear working range from 100 to 500 μmol/L was obtained for all analytes in an equimolar TRIS/TAPS (10 mmol/L) solution as the background electrolyte as well as adequate LOD (7, 6, 7, and 10 μmol/L for K⁺, Na⁺, diethylammonium, and DCF, respectively). The proposed method was applied to the analysis of pharmaceutical formulations (tablets and spray form) with similar results to those achieved by HPLC (DCF) or flame photometry (K and Na) at a 95% confidence level.     

Direct correlation functions of binary mixtures of hard Gaussian overlap molecules

We study the direct correlation function (DCF) of a classical fluid mixture of nonspherical molecules. The components of the mixture are two types of hard ellipsoidal molecules with different elongations, interacting through the hard Gaussian overlap (HGO) model. Two different approaches are used to calculate the DCFs of this fluid, and the results are compared. Here, the Pynn approximation [J. Chem. Phys. 60, 4579 (1974)] is extended to calculate the DCF of the binary mixtures of HGO molecules, then we use a formalism based on the weighted density functional theory introduced by Chamoux and Perera [J. Chem. Phys. 104, 1493 (1996)]. These results are fairly in agreement with each other. The pressure of this system is also calculated using the Fourier zero components of the DCF. The results are in agreement with the Monte Carlo molecular simulation.     

Analysis of the validity of perturbation density functional theory: based on extensive simulation for simple fluid at supercritical and subcritical temperature under various external potentials

Because of the scarcity of available simulation data for confined hard-core attractive Yukawa model fluid, extensive Monte Carlo (MC) simulation research for this fluid under the influence of various external potentials were carried out. The present MC simulation results were employed to test a performance of the third-order perturbation density functional theory (DFT) based on a high order direct correlation function (DCF) [S. Zhou and E. Ruckenstein, Phys. Rev. E. 61, 2704 (2000)]. It was found that the present perturbation DFT formalism is soundly structured only if the imported second-order DCF is reliable. In this case, the accuracy of the results can be satisfactory or even very high for various types of external potentials. Further, the associated adjustable parameter can be universal, i.e., independent of the particular external field responsible for the generation of a nonuniform density profile. Dependence of both the maintenance of the reliability of the formalism and holding of the universality of the adjustable parameter on the accuracy of the imported bulk second-order DCF can be strengthened by the large difference between the external field investigated and that caused by a single hard wall used for specification of the adjustable parameter. In case the gaseous density in the subcritical region is below the coexistence density, an excellent performance of the present formalism is observed even for the mean spherical approximation's second-order DCF as an input. This advantageous property, combined with the fact that the present formalism needs only the second-order DCF of fluid at the coexistence state as an input, enables the present formalism to be a very good theoretical tool for the investigations of wetting and prewetting transitions.     

Flow-Injection Spectrophotometric Determination of Diclofenac or Mefenamic Acid in Pharmaceuticals

 Two flow injection (FI) spectrophotometric methods are proposed for the determination of diclofenac (DCF) or mefenamic acid (MF) in bulk samples and pharmaceuticals. Both methods are based on the reaction of DCF or MF with potassium ferricyanide in a sodium hydroxide medium. The absorbance of the orange products obtained is measured at 455 nm for DCF and 465 nm for MF. The corresponding calibration graphs are linear over the range 0.20–20.0 mg L⁻¹ for DCF and 1.00–100 mg L⁻¹ for MF, while the limits of detection were 0.05 and 0.18 mg L⁻¹, respectively. Received March 27, 2000. Revision November 15, 2000.     

NMR study on the low-affinity interaction of human serum albumin with diclofenac sodium

The low-affinity interaction between human serum albumin (HSA) and Diclofenac sodium (DCF) was studied using NMR techniques. Both 13C-NMR chemical shift and linewidth show that the dichlorophenyl ring in DCF molecule plays a primary role in its interaction with HSA. Langmuir adsorption isotherm was applied to evaluate the association constant K and the number of binding sites n of the drug/HSA complex through (1)H-NMR spin-lattice relaxation measurement. The results indicate that Langmuir isotherm can perfectly explain the capacity of low-affinity binding of proteins for the ligands.     

Enhanced visible photocatalytic degradation of diclofen over N-doped TiO2 assisted with H2O2: A kinetic and pathway study

Increasing discharge and inadequate removal of pharmaceutical compounds pose significant concerns over global aquatic systems and human health. The accomplishment of affordable and safe water requires a stringent elimination of these micropollutants. This study evaluated the performance of Visible/N-doped TiO₂ and Visible/N-doped TiO₂/H₂O₂ processes using a submerged photocatalytic membrane reactor (SMPR) with suspended N-doped TiO₂ to address the removal of diclofenac (DCF). The kinetic and pathway of photodegradation of DCF were of particular interest in this study. The initial DCF concentrations upon the experiments were also examined using a wide range of 5–50 mg/L and 20–100 mg L⁻¹ for Vis/N-doped TiO₂, and Vis/N-doped TiO₂/H₂O₂ process, respectively. The results indicated that higher initial concentration reduces the efficiency of the process, but one with H₂O₂ demonstrated an enhanced performance. The experimental data were found to fit well a pseudo-first-order kinetic model. Our findings demonstrated the analogous pathways of DCF for both processes. The Vis/N-doped TiO₂/H₂O₂ process tends to hasten the degradation rate as evidenced by the disappearance of some DCF byproducts at a similar irradiation period as compared to the other. The study provided useful information of the degradation rate and the potential formation of DCF intermediates upon the hybrid photocatalytic systems, therefore being of importance for scaling-up as well as evaluating potential detoxification of DCF upon the novel photocatalytic system.     

三氟化硼乙醚溶液中卤代芴的电化学聚合

在三氟化硼乙醚(BFEE)溶液中9-溴芴和9,9-二氯芴可以直接阳极氧化制备聚(9-溴芴)和聚(9,9-二氯芴).单体在BFEE中的起始氧化电位远低于在乙腈体系中的起始氧化电位.聚(9-溴芴)和聚(9,9-二氯芴)均可溶于强极性有机溶剂,如二甲基亚砜、四氢呋喃等,并分别表现出良好的蓝色和黄绿色发光性能,其电导率测定为10-1S/cm.红外光谱和核磁共振波谱表明聚合反应主要发生在2,7位.     

Bond-forming reactions of dications with molecules: a computational and experimental study of the mechanisms for the formation of HCF2+ from CF3(2+) and H2

The QCISD and QCISD(T) quantum chemical methods have been used to characterize the energetics of various possible mechanisms for the formation of HCF2+ from the bond-forming reaction of CF3(2+) with H2. The stationary points on four different pathways leading to the product combinations HCF2+ + H+ + F and HCF2+ + HF+ have been calculated. All four pathways begin with the formation of a collision complex [H2-CF3]2+, followed by an internal hydrogen atom migration to give HC(FH)F2(2+). In two of the mechanisms, immediate charge separation of HC(FH)F2(2+) via loss of either HF+ or a proton, followed by loss of an F atom, yields the experimentally observed bond-forming product HCF2+. For the other two mechanisms, internal hydrogen rearrangement of HC(FH)F2(2+) to give C(FH)2F(2+), followed by charge separation, yields the product CF2H+. This product can then overcome a 2.04 eV barrier to rearrange to the HCF2+ isomer, which is 1.80 eV more stable. All four calculated mechanisms are in agreement with the isotope effects and collision energy dependencies of the product ion cross sections that have been previously observed experimentally following collisions between CF3(2+) and H2/D2. We find that in this open-shell system, CCSD(T) and QCISD(T) T1-diagnostic values of up to 0.04 are acceptable. A series of angularly resolved crossed-beam scattering experiments on collisions of CF3(2+) with D2 have also been performed. These experiments show two distinct channels leading to the formation of DCF2+. One channel appears to correspond to the pathway leading to the ground state 1DCF2+ + D+ + F product asymptote and the other to the 3DCF2+ + D+ + F product asymptote, which is 5.76 eV higher in energy. The experimental kinetic energy releases for these channels, 7.55 and 1.55 eV respectively, have been determined from the velocities of the DCF2+ product ion and are in agreement with the reaction mechanisms calculated quantum chemically. We suggest that both of these observed experimental channels are governed by the reaction mechanism we calculate in which charge separation occurs first by loss of a proton, without further hydrogen atom rearrangement, followed by loss of an F atom to give the final products 1DCF2+ + D+ + F or 3DCF2+ + D+ + F.     

Fluorescent sensors for specific RNA: a general paradigm using chemistry and combinatorial biology

Here, we describe a new paradigm for the development of small molecule-based RNA sensors. We prepared a series of potential PET (photoinduced electron transfer) sensors on the basis of 2',7'-dichlorofluorescein (DCF) fluorophore conjugated with two aniline derivatives as electron donors (quenchers). NMR and fluorescent spectroscopic analyses of these DCF derivatives revealed the correlation between the conformations, the PET, and the fluorescent intensities of these DCF derivatives, enabling us to select a sensor candidate. RNA aptamers were raised against the aniline-based quencher via in vitro selection (SELEX). One of these aptamers enhanced the fluorescence intensity of the DCF-aniline conjugate in a concentration-dependent manner. To demonstrate the power and generality of this approach, additional in vitro selection was performed and aptamers from this selection were found to have similar activities. These results show that one can develop fluorescence-inducing reporter RNA and morph it into remotely related sequences without prior structural insight into RNA-ligand binding.     

Application of spinel-structured MgFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles for simultaneous electrochemical determination diclofenac and morphine

The paper describes a sensitive method for simultaneous sensing of morphine (MOR) and diclofenac (DCF). The surface of a MgFe₂O₄/graphite paste electrode was modified with multi-walled carbon nanotubes, and the resulting sensor was characterized by cyclic voltammetry, differential pulse voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The electrode showed an efficient synergistic effect in term of oxidation of DCF and MOR, with sharp oxidation peaks occurring at +0.370 and 0.540 V (vs Ag/AgCl) at pH 7.0. The calibration plot for MOR is linear in the 50 nM to 920 μM concentration range, and the detection limit is 10 nM (at a signal-to-noise ratio of 3). The respective data for DCF are 100 nM to 580 μM, with a 60 nM LOD. The sensor was applied to the determination of MOR and DCF in spiked serum and urine samples, with recoveries ranging between 91.4 and 100.7 %.

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Graphical abstract A sensitive method for simultaneous sensing of morphine (MOR) and diclofenac (DCF) is described. The surface of MgFe₂O₄/graphite paste electrode was modified with multi-walled carbon nanotubes, and the resulting sensor showed an efficient synergistic effect in terms of oxidation of DCF and MOR. The calibration plot for MOR is linear in the 50 nM to 920 μM concentration range, and the detection limit is 10 nM. The respective data for DCF are 100 nM to 580 μM, with a 60 nM LOD.

     

Singlet oxygen generated from the decomposition of peroxymonocarbonate and its observation with chemiluminescence method

The decomposition of peroxymonocarbonate (HCO(4)(-)) has been investigated by flow-injection chemiluminescence (CL) method. An ultraweak CL was observed during mixing the bicarbonate and hydrogen peroxide solution in organic cosolvent. An appropriate amount of fluorescent organic compounds, such as dichlorofluorescein (DCF), was added to the HCO(4)(-) solution, a strong CL was recorded. Based on studies of the spectrum of fluorescence, CL and UV-vis spectra, electron spin trapping (ESR) technique, mass spectra (MS) and comparison with H(2)O(2)/hypochlorite (ClO(-)) and H(2)O(2)/molybdate (MoO(4)(-)) systems, the CL mechanism was proposed. The reaction is initiated by unimolecular homolysis of the peroxo O-O bond in HO-OCOO(-) molecule. It was suggested that the bond rearrangement within radicals yield superoxide ion (O(2)(*-)). The interaction of superoxide ion with perhydroxyl radical produces singlet oxygen ((1)O(2)). The energy transfers from singlet oxygen to DCF forming an excited energy acceptor (DCF*). Luminescence (lambda(max)=509 nm) was emitted during the relaxation of the energy acceptor to the ground state.     

A kinetics,isotherms, and thermodynamic study of diclofenac adsorption using activated carbon prepared from olive stones

The objective of this work was to study the efficiency of activated carbon prepared from agricultural waste (olive stones; OS) on diclofenac (DCF) adsorption in aqueous solutions. The prepared charcoals were characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM)/Energy Dispersive X-Ray Analyser (EDX), and Brunauer–Emmett–Teller (BET) analysis techniques. The results show that DCF adsorption is favorable in acid medium and low temperature. The adsorption kinetics follows a pseudo-second-order kinetic model. The adsorption was found to be spontaneous (ΔG°?相似文献   

Polymer density functional theory approach based on scaling second-order direct correlation function

A second-order direct correlation function (DCF) from solving the polymer-RISM integral equation is scaled up or down by an equation of state for bulk polymer, the resultant scaling second-order DCF is in better agreement with corresponding simulation results than the un-scaling second-order DCF. When the scaling second-order DCF is imported into a recently proposed LTDFA-based polymer DFT approach, an originally associated adjustable but mathematically meaningless parameter now becomes mathematically meaningful, i.e., the numerical value lies now between 0 and 1. When the adjustable parameter-free version of the LTDFA is used instead of the LTDFA, i.e., the adjustable parameter is fixed at 0.5, the resultant parameter-free version of the scaling LTDFA-based polymer DFT is also in good agreement with the corresponding simulation data for density profiles. The parameter-free version of the scaling LTDFA-based polymer DFT is employed to investigate the density profiles of a freely jointed tangent hard sphere chain near a variable sized central hard sphere, again the predictions reproduce accurately the simulational results. Importance of the present adjustable parameter-free version lies in its combination with a recently proposed universal theoretical way, in the resultant formalism, the contact theorem is still met by the adjustable parameter associated with the theoretical way.     

A density-functional theory study of the confined soft ellipsoid fluid

A system of soft ellipsoid molecules confined between two planar walls is studied using classical density-functional theory. Both the isotropic and nematic phases are considered. The excess free energy is evaluated using two different Ans?tze and the intermolecular interaction is incorporated using two different direct correlation functions (DCF's). The first is a numerical DCF obtained from simulations of bulk soft ellipsoid fluids and the second is taken from the Parsons-Lee theory. In both the isotropic and nematic phases the numerical DCF gives density and order parameter profiles in reasonable agreement with simulation. The Parsons-Lee DCF also gives reasonable agreement in the isotropic phase but poor agreement in the nematic phase.     

Density functional theory of inhomogeneous liquids. I. The liquid-vapor interface in Lennard-Jones fluids

A simple model is proposed for the direct correlation function (DCF) for simple fluids consisting of a hard-core contribution, a simple parametrized core correction, and a mean-field tail. The model requires as input only the free energy of the homogeneous fluid, obtained, e.g., from thermodynamic perturbation theory. Comparison to the DCF obtained from simulation of a Lennard-Jones fluid shows this to be a surprisingly good approximation for a wide range of densities. The model is used to construct a density functional theory for inhomogeneous fluids which is applied to the problem of calculating the surface tension of the liquid-vapor interface. The numerical values found are in good agreement with simulation.