Journal- Chinese Chemical Society Taipei

Published by Wiley-VCH Verlag
Online ISSN: 2192-6549
Print ISSN: 0009-4536
For the first time the technique of fast continuous cyclic voltammetry is used as a highly sensitive detection method for the monitoring of paromomycin in a flow-injection system. A special computer-based numerical calculation method (using fast Fourier transformation) is introduced here for the enhancement of the analyte signal and noise reduction.This research includes the observation of the effects of various parameters (rest potential, sweep rate and delay time) on the sensitivity of the detection system. Furthermore, a potential waveform, consisting of the potential steps for cleaning, accumulation and the step for the potential ramp of the analyte, was applied to an Au disk microelectrode in a continuous way.Eventually, the method was found to be linear for the concentration range of 160–160,000 pg/mL (r = 0.999) with a limit of detection (LOD) and quantitation (LOQ) 49.25 and 160 pg/mL, respectively. The stripping time was less than 300 ms, while the detection limit was about 10,000 times lower than that of the most sensitive reported method.As a result, the system illustrates the requisite accuracy, sensitivity, precision and selectivity to assay paromomycin in capsules.
The comments of Guseinov are critically analyzed. Contrary to his comments, it is pointed out that our formula for two-center overlap integrals over Slater type orbitals have been derived independently, not derived from the earlier works of Guseinov by changing the summation indices. Therefore, our algorithm is original, is not affected from possible instability problems and can be used in large scale calculations without loss of significant figures. Meanwhile, it should be stressed that his comment on the transformation of our formula into his formula proves the correctness of our algorithm and therefore can be regarded as a nice sound of science.
We clarify the relationships between the eight structural types of toroidal carbon nanotubes (TCNTs), which can be identified as the eight corners of a cube of structural transformation. The four families with Dnh symmetry can be related by rim rotations, and the same is true for those with Dnd symmetries. These two sets are then connected by horizontal shiftings, thereby completing the cube. Moreover, we further point out that there are five more highly symmetric Dnh structural types that can be derived from performing the generalized Stone-Wales transformatoin on certain TCNTs with Dnh structural types.
The values of K j for N = 6, µ = 3 and a = 2.5 are presented. The filled circles indicates the K j values, while the dotted lines shows the trend. The data shown, from the lowest to the highest curve, correspond to b + δV = 3, 4, 5, 6 and 7, respectively.
The current-concentration relation of the present model is compared with that obtained through Brownian dynamics and molecular dynamics simulations[40]. The filled circles are the simulated current-concentration relation of wild-type Kv1.2 channel. The filled squares are the simulated current-concentration relation of mutated Kv1.2 channel in which two of the proline residues were replaced by aspartate residues. The current values of all of these data were multiplied by 6 so that they can be in the same scale as the currents calculated from the present model. The five lines are the current-concentration relation calculated from the present model. The number of binding sites is assumed to be 4. Other parameters are a = 2.5, µ = 3, δ = 10, κ = 1, β = 1, and membrane voltage V = 0.12. The five curves, from the bottom to the top, correspond to b = 0, 1, 2, 3 and 4, respectively.
It has long been accepted that the multiple-ion single-file transport model is appropriate for many kinds of ion channels. However, most of the purely theoretical works in this field did not capture all of the important features of the realistic systems. Nowadays, large-scale atomic-level simulations are more feasible. Discrepancy between theories, simulations and experiments are getting obvious, enabling people to carefully examine the missing parts of the theoretical models and methods. In this work, it is attempted to find out the essential features that such kind of models should possess, in order that the physical properties of an ion channel be adequately reflected.
Computed potential energy surfaces are often required for computation of such parameters as rate constants as a function of temperature, product branching ratios, and other detailed properties. For some dynamics methods, global potential energy surfaces are required. In this case, it is necessary to obtain the energy at a complete sampling of all the possible arrangements of the nuclei, which are energetically accessible, and then a fitting function must be obtained to interpolate between the computed points. In other cases, characterization of the stationary points and the reaction pathway connecting them is sufficient. These properties may be readily obtained using analytical derivative methods. We have found that computation of the stationary points/reaction pathways using CASSCF/derivative methods, followed by use of the internally contracted CI method to obtain accurate energetics, gives usefull results for a number of chemically important systems. The talk will focus on a number of applications including global potential energy surfaces, H + O2, H + N2, O(3p) + H2, and reaction pathways for complex reactions, including reactions leading to NO and soot formation in hydrocarbon combustion.
The photocatalytic degradation of phorate in aqueous suspensions was examined with the use of titanium dioxide (TiO2) as a photocatalyst. About 99% of phorate was degraded after UV irradiation for 60 min. The photodegradation of phorate followed pseudo-first-order kinetics and parameters such as pH of the system, TiO2 dosage, and presence of anions were found to influence the reaction rate. To obtain a better understanding of the mechanistic details of this TiO2-assisted photodegradation of phorate with UV irradiation, the intermediates of the processes were separated, identified, and characterized by the solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) techniques. The probable photodegradation pathways were proposed and discussed. To the best of our knowledge, this is the first study that reports the degradation pathways of phorate. The electrical energy consumption per order of magnitude for photocatalytic degradation of phorate was also calculated and showed that a moderated efficiency (EEO = 96 kWh/(m3 order)) was obtained in TiO2/UV process.
The denaturing kinetics for a model system. Initially the external conditions make the local free energy difference = 2k B T . At the moment when the scaled time τ = 0, the external conditions are suddenly changed so that the local free energy difference abruptly changes into = −2.5k B T .  
The denaturing kinetics of the same model system as that shown in Fig. (1). The instantaneous activities are plotted against time. The thinner line depicts the non-cooperative case, while the thick line corresponds to the case in which J = 0.5k B T .  
The denaturing kinetics of the same model system as that shown in Fig. (1). The thinner lines depict the non-cooperative case, while the thick lines correspond to the case in which J = 0.5k B T . The solid lines are the instantaneous activities subtracted by the equilibrium activities, and the dotted lines are the rate factors 2Γ 2 σ /  
The denaturing kinetics of a similar model system as that shown in Fig. (1). The thinner lines depict the non-cooperative case, while the thick lines correspond to the case in which J = −0.5k B T . The solid lines are the instantaneous activities subtracted by the equilibrium activities, and the dotted lines are the rate factors 2Γ 2 σ /  
The logarithm of the apparent rate constant k obs is plotted against the local free energy change ¯ = /k B T for three different values of ¯ J: 0 (dashed line), 1/4 (thin solid line) and 1/2 (thick solid line).  
In this work we focused on the kinetics of a one-dimensional Ising system (1DIS) with constant nearest-neighbor interaction (NNI). The exact solution of both thermodynamics and kinetics of this system under quasi-chemical approximation (QCA) had been shown in the literature, and the equilibrium solution was exact. In this work, it was discussed why QCA applied the best in the case of 1DIS with constant NNI. Furthermore, extension had been made to discuss that due to this special reason, perhaps the kinetics of the system under QCA is the correct steady-state kinetics. Inspired by this observation, the activity and activity coefficients of the system was studied closely to re-examine the form of the equation of motion under QCA. A novel concept---the instantaneous activities and the corresponding instantaneous activity coefficients---was introduced, and in terms of these quantities the kinetics seemed to be much simpler and physically more meaningful. The chevron plot of this system was also discussed and new way of looking at the \emph{rollover} of chevron plots was presented.
The effects of imperfect gate operations in implementation of Shor's prime factorization algorithm are investigated. The gate imperfections may be classified into three categories: the systematic error, the random error, and the one with combined errors. It is found that Shor's algorithm is robust against the systematic errors but is vulnerable to the random errors. Error threshold is given to the algorithm for a given number $N$ to be factorized.
Time-dependent wave packet calculations for the reaction H+HCl and its isotopic reactions are carried out on the potential energy surface (PES) of Bian and Werner (BW2) [Bian, W.; Werner, H. -J., J. Chem. Phys. 2000, 112, 220]. Reaction probabilities for the exchanged and abstraction channels are calculated from various initial rotational states of the reagent. Those have then been used to estimate reaction cross sections and rate constants which also are calculated and explained by the zero-point energy and the tunneling effect. The results of this work were compared with that of previous quasiclassical trajectory calculations and reaction dynamics experiments on the abstraction channel. In addition, the calculated rate constants are in reasonably good agreement with experimental measurements for both channels. Key words: ab initio, H/D+ DCl/HCl, collision energy, integral cross section, rate constan
An efficient synthesis of novel mono and bis-1,2,3-triazoles 3′-azido-2′-deoxythymidine (AZT) derivatives via copper(I)-catalyzed 1,3-dipolar cycloaddition reaction is described. Starting from AZT and terminal alkyne derivatives, mono and bis-1,2,3-triazole AZT derivatives are regioselectively obtained in good yields under mild conditions using CuSO4·5H2O and sodium ascorbate as a catalyst system, and t-BuOH/H2O (1:1, v/v) as a co-solvent. The structures of these compounds were elucidated by IR, HR MS and NMR.
A new method has been described to determine both benzodiazepines (six) and tricyclic antidepressants (four) simultaneously in saliva by HPLC with a UV detector set at 240 nm using cholchicine as the internal standard. A careful specific sequential solid-phase elution was optimized and performed to elute benzodiazepines using a mixture of methanol-acetonitrile (1:1 v/v) followed by the elution of tricyclic antidepressants with methanol. Separation of the compounds was performed on a Kromasil column (250 × 4 mm, 5 μm) by a gradient eluents consisting of 0.05 M CH3COONH4-acetonitrile-methanol (55:15:30 v/v/v). The results were linear for both benzodiazepines and tricyclic antidepressants up to 20 ng μL-1 with the correlation coefficients greater than 0.998. The sensitivity limits, LOD and LOQ were 0.08-0.34 ng μL-1 and 0.28-1.13 ng μL-1, respectively. The method is simple, fast and reliable with good specificity and sensitivity, will be suitable for use in a clinical setting, where there is a concomitant use of 1,4-benzodiazepines and tricyclic antidepressants.
Our previous experimental results have shown that ergosta-4,6,8(14),22-tetraen-3-one (ergone) is one of the main bioactive components of Polyporus umbellatus. The efficacy of ergone binding to human serum albumin (HSA) is critical for pharmacokinetic behavior of ergone. The interactions between ergone and HSA under simulative physiological conditions were investigated by the methods of fluorescence spectroscopy, absorption and circular dichroism spectroscopy. Fluorescence data revealed that the fluorescence quenching of HSA by ergone was the result of the formation of the ergone-HSA complex. According to the modified Stern-Volmer equation, the binding constants (Ka) between ergone and HSA were determined. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) for the reaction were calculated to be 0.989 kJ mol-1 and 11.214 J mol-1 K-1, indicating that the hydrogen bonds and hydrophobic interactions played a dominant role in the binding of ergone to HSA. The conformational investigation showed that the presence of ergone decreased the α-helical content of HSA and induced the slight unfolding of the polypeptides of protein. Furthermore, displacement experiments using warfarin and ibuprofen indicated that ergone could bind to site I of HSA, which was also in agreement with the results of the molecular modeling.
The organic tribromide, [H2-cryptand 222](Br3)2 was synthesized and characterized by X-ray rystallography, and was utilized as an active catalyst for the N-boc protection of amines. The method is general for the preparation of N-boc derivatives of aliphatic (acyclic and cyclic), aromatic, primary and secondary amines. We also applied our new reaction protocols for the N-boc protection of some new amines and spectral and physical data for the obtained products are reported.
An efficient and stereoselective synthesis of the C1-C9 moiety of the 7,8-O-isopropylidene protected iriomoteolide 3a derivative has been accomplished. In our strategy, we employed olefin cross-metathesis of the L-(+)-tartaric acid derivative (((4S,5S)-2,2-dimethyl-5-vinyl-1,3-dioxolan-4-yl)methoxy)(tert-butyl)diphenylsilane with a synthesized methyl (S)-3-methylhex-5-enate to successfully provide the correct olefin geometry of the desired fragment.
INTRODUCTION From a sur vey of atomic tran si tions us ing the multiconfigurationDirac -Fock (MCDF) method, Feldman, Indelicato and Sugar 1 re ported that a for bid den tran si tion between the low est fine-structure lev els of (3d 4 ) J = 2 and J = 3 was to be ob served in the op ti cal re gion for most high-Z ti tanium-like ions. Be sides its po ten tial im por tance for high-temperature plasma di ag nos tics, the tran si tion serves as a test-ground for many-body atomic struc ture the o ries, as will be seen shortly. The first ob ser va tion of the tran si tion was made by Mor gan et al. 2 for Xe 32+ and Ba 34+ . How ever, mea sured wavelengths were found to have an un ex pect edly large dis crepancy ( 5%) from state-of-the-art MCDF calculations. 3 Indelicato 4 tried to re fine the MCDF cal cu la tions by in cl
Mesoporous ZrMCM-41 nanoparticles were synthesized by a usual way where tetraethyl-orthosilicate (TEOS) and zirconium nitrate were used as the inorganic precursors. The obtained nanoscale ZrMCM-41 was characterized by X-ray diffraction, N2 physis-sorption, scanning electron microscopy and transmission electron microscopy. Characterization results revealed that zirconium salt added in the synthesis had a crucial effect on the assembly of nanoscale ZrMCM-41 with relatively uniform particle size, which was rarely observed in reported studies for ZrMCM-41 synthesized using the similar method. Meanwhile, the possible mechanism behind the synthesis was discussed based on the character of hydrolysis and condensation of TEOS and the mild acidic environment induced by the hydrolysable zirconium salt under aqueous conditions. Thus obtained nanoscale ZrMCM-41 with developed pore structures may be advantageous to general applications in catalysis or adsorption host-guest chemistry in terms of efficient mass transport of guest molecules.
Poly(2-hydroxyethyl methacrylate-ethylene dimethacrylate) (PHEMA-EDMA) beads were produced by free radical co-polymerization of 2-hydroxyethyl methacrylate (HEMA) and ethylene dimethacrylate (EDMA). Then, metal complexing ligand alizarin yellow was covalently attached onto PHEMA-EDMA beads. The resulting resin has been characterized by FT-IR and studied for the preconcentration and determination of trace Pb(II) ion from solution samples. The optimum pH value for sorption of the metal ion was 5. The sorption capacity of functionalized resin is 100 mg.g-1. The chelating resin can be reused for 20 cycles of sorption-desorption without any significant change in sorption capacity. A recovery of 96% was obtained for the metal ion with 0.1 M nitric acid as eluting agent. The equilibrium adsorption data of Pb(II) on modified resin were analyzed by Langmuir and Freundlich models. Based on equilibrium adsorption data the Langmuir and Freundlich constants were determined 2.571 and 418.7 at pH 5 and 25 °C. The method was applied for lead ions determination from well water sample.
Aryl perfluorooctanesulfonates (fluorous sulfonate) have been developed as triflates and nonaflates alternatives for Pd-catalyzed coupling reactions to form C-C, C-N, C-S, C-H, and C-CN bonds. They also serve as phase-tags for fluorous solid-phase extraction (F-SPE) to facilitate product purifications. Other synthetic techniques such as microwave reactions and multicomponent reactions are combined with the fluorous linker strategy to further increase synthetic efficiency. The utility of fluorous sulfonate linkers in the synthesis of biologically interested library scaffolds is summarized in this short review article.
We developed a simple, rapid and reliable method for determination of 20 common amino acids based on derivatization with 9-fluorenylmethyl chloroformate (FMOC-Cl) and RP-LC/UV, this method was first introduced into quantitative analysis of amino acids. The amino groups of amino acids were trapped with FMOC-Cl to form amino acid-FMOC-Cl adducts which can be suitable for LC-UV. Chromatographic separation was performed on a C18 column with a mobile phase gradient consisting of acetonitrile and sodium acetate solution. This method was shown to be sensitive for 20 common amino acids. In the intra-day precisions assay, the range of RSDs was 3.21-7.67% with accuracies of 92.34-102.51%; for the inter-day precisions assay, the range of RSDs was 5.82-9.19% with accuracies of 90.25-100.63%. The results also indicated that solutions of amino acids-FMOC-Cl can be kept at room temperature for at least 24 h without showing significant losses in the quantified values. The validated method was successfully applied to the determination of major four kinds of amino acids in R. isatidis samples (Arg, Pro, Met and Val). The total content of amino acids in different origin R. isatidis was 13.32-19.16 mg/g. The differences between R. isatidis samples were large using HCA.
Reaction of cyclic β-dicarbonyl compounds such as pyrimidine-(1H,3H,5H)-2,4,6-trione (BA), 1,3-dimethyl pyrimidine-(1H,3H,5H)-2,4,6-trione (DMBA) and 2-thioxo-pyrimidine-(1H,3H,5H)-4,6-dione (TBA) with cyanogen bromide in acetone and 2-butanone in the presence of triethylamine afforded a new class of stable heterocyclic spiro[furo[2,3-d]pyrimidine-6,5′-pyrimidine]2,2′,4,4′,6′(3H,3′H,5H)-pentaones (dimeric forms of barbiturate) at 0 °C and ambient temperature. Structure elucidation was carried out by X-ray crystallographic, 1H NMR, 13C NMR, two dimensional NMR, FT-IR spectra, mass spectrometry and elemental analysis. The mechanism of product formation is discussed. The reaction of DMBA with cyanogen bromide in the presence of triethylamine also afforded trimeric form of barbiturate of uracil derivatives in good yield. The reaction of selected acyclic β-dicarbonyl compounds with cyanogen bromide in the presence of triethylamine in acetone and/or diethyl ether has also been investigated under the same condition. Diethyl malonate and ethyl cyanoacetate brominated and also ethyl acetocetate both brominated and cyanated on active methylene via cyanogen bromide.
A magnetic adsorbent was synthesized by modification of activated carbons with magnetic iron oxide nanoparticles (AC-MIONs). The preparation method is fast and could be carried out in an ordinary condition. The AC-MIONs were used as quite efficient adsorbents for separation of methylene blue (MB) from aqueous solution in a batch process. The effect of different parameters such as pH, temperature, electrolyte concentration, contact time and interfering ions on the removal of MB were studied. The adsorption data were analyzed by Langmuir and Freundlich isotherm models and a maximum adsorption amount of 47.62 mg g-1 and a langmuir adsorption equilibrium constant of 3.0 L mg-1 were obtained. The obtained results revealed that AC-MIONs were effective adsorbents for fast removal of MB from different aqueous solutions. This adsorbent was successfully used for removal of MB from Karoon River water.
Neodymium is applied widely in agriculture to improve crop nutrition and incidentally in fertilizers, yet little is known of its effect on the biological function of human serum albumin (HSA). The interaction of Nd3+ to HSA has been investigated mainly by fluorescence spectra, UV–vis absorption spectra and circular dichroism (CD) under simulative physiological conditions. Fluorescence data revealed that the quenching mechanism of HSA by Nd3+ was a static quenching process and the binding constant is 5.71 × 104 L mol-1 and the number of binding sites is 1 at 292 K. The thermodynamic parameters (ΔH0 = -20.79 kJ mol-1, ΔG0 = -26.58 kJ mol-1, and ΔS0 = 19.85 J mol-1 K-1) indicate that electrostatic effect between the protein and Nd3+ is the main binding force. The distance r = 2.91 nm between donor (HSA) and acceptor (Nd3+) was obtained according to Förster's nonradiative energy transfer. In addition, UV–vis, CD and synchronous fluorescence results showed that the addition of Nd3+ changed the conformation of HSA.
A highly selective PVC membrane electrode for Al3+ based on salicylaldehyde salicyloyl hydrazone as a neutral carrier has been prepared and studied. The sensor exhibits a good response for Al3+ over a linear range of 9.0 × 10-6 to 1.0 × 10-1 mol/L, with a Nernstian slope of 20.0 ± 0.2 mV/decade and detection limit of 7.0 × 10-6 mol/L. Selectivity coefficients determined by the method of separate solution indicate high selectivity for Al3+. The response mechanism was discussed in view of UV-Vis spectroscopy technique and the A.C. impedance technique. It was used as an indicator electrode in potentiometric titration of Al3+ with EDTA and in the determination of Al3+ in real samples. The electrode has a relatively fast response time, long life time and satisfactory stability.
A new speciation and preconcentration method based on dispersive liquid-liquid microextraction has been developed for trace amounts of As(III) and As(V) in urine and water samples. At pH 4, As(III) is complexed with ammoniumpyrrolidine dithiocarbamate and extracted into 1-Hexyl-3-methylimidazolium hexafluorophosphate, as an ionic liquid (IL) and As(III) is determined by electrothermal atomic absorption spectrometery (ETAAS). Arsenic(V) in the mixing solution containing As(III) and As(V) was reduced by using KI and ascorbic acid in HCl solution and then the procedure was applied to determination of total arsenic. Arsenic(V) was calculated as the difference between the total arsenic content and As(III) content. The effect of various parameters on the recovery of the arsenic ions has been studied. Under the optimum conditions, the enrichment factor 135 was obtained. The proposed method was successfully applied to the determination of trace amounts of As(III) and As(V) in water and biological samples.
Simple, isocratic and rapid RP-HPLC method has been developed for the simultaneous analysis of gemifloxacin and H2-receptor antagonists i.e. Cimetidine, Famotidine and Ranitidine, in bulk, pharmaceutical formulation and human serum. Separation was achieved on the RP-Mediterranea column [C18 (250 × 4.6 mm, 5 μ)] at ambient temperature using mobile phase consisting of acetonitrile: methanol: water (20:28:52 v/v/v pH 2.8 adjusted by phosphoric acid). Flow rate was 1.0 mL/min with an average operating pressure of 180 kg/cm2. Gatifloxacin (GATI) was used as an internal standard (IS). Quantitation was achieved with UV detection at 221, 256 and 267 nm, respectively. Linear calibration curves, at concentration ranges of 0.05-37.5 μgmL-L with a correlation coefficient of ±0.9994. The detection and quantification limits were in the ranges of 0.023-0.250 μgmL-L and 0.071-0.756 μgmL-L, respectively. Friedman's and Student's t-test were applied to correlate these results. Method was validated in terms of selectivity, linearity, precision, robustness, recovery, limits of detection and quantitation and is applicable to the routine analysis of GFX and H2-receptor antagonists, alone or in combination.
Antioxidant activity of compounds 4e, 4h and 4i and BHT using DPPH free radical scavenging method after 30 min. of incubation.  
Antioxidant activity of compounds 4e, 4h and 4i and BHT using DPPH free radical scavenging method after 1 hr of incubation.  
Comparsion of antioxidant activity of compounds 4e, 4h and 4i and BHT using DPPH free radical scavenging method after 30 min. and 1 hr of incubation.  
Physical data of compounds 4a-m
New Schiff base derivatives, 2,2′-[naphthalene-2,7-diylbis(oxy)]bis[N′-substituted acetohydrazide] (4a-m) were synthesized by the acid catalyzed condensation of aryl/hetero aromatic aldehydes with 2,2′- [naphthalene-2,7-diylbis(oxy)]diacetohydrazide (3) under reflux temperature and ultrasonic irradiation. These Schiff base derivatives were confirmed through spectral characterization using IR, 1H NMR, 13C NMR and mass spectra. All the synthesized compounds were screened for their antioxidant activity using DPPH free radical scavenging method.
INTRODUCTION Col li sion pro cesses of pro tons and anti-protons on hydro gen at oms are one of the mostim por tant and the mostsimple cases of atomic col li sion re search. It is eas ily con sid ered thattheinteractionofprojec tile par ti cleandelectron is opposite to each other and the tra jec tory ef fect is re verse, whereas vir tual pho ton in ter ac tion due to the mo tion of pro jec tile chargedpar ti cles is independentofthesignofelec tric charge. Thecompar i sonoftwoprocesses will givede tailed in for mation on the fun da men tal mech a nism of the few-particle dynamicprocess. BesidesthetraditionalBornapprox i mation method in highenergy col li sions, for ex ci ta tion pro cess by pro ton im pact, there are also the close cou pling method by Frisch et al. 1 and by Toshima, 2 clas sic tra jec tory methodby Illescas 3 and lattic time-dependent method by Schultz et al. 4 As for the ex ci ta tion pro ces
A simple and sensitive method based on dispersive liquid-liquid microextraction (DLLME) in conjunction with high performance liquid chromatography-diode array detection (HPLC-DAD) has been developed for the quantitative analysis of patulin in apple juice and concentrate samples. The effect of extraction and disperser solvent (nature and volume), pH of sample solution, extraction time and extraction temperature was investigated. Under the optimal conditions the linear dynamic range of patulin was from 8.0 to 40.0 μg L-1 with a correlation coefficient of 0.9993 and a detection limit of 4.0 μg L-1. The relative standard deviation (RSD) was less than 5.9% (n = 5) and the recovery values were in the range of 94-97%. Finally the proposed method was successfully applied for the analysis of patulin in apple juice and concentrate samples.
Carbonyls' 2π orbital populations, [2π], in W(CO)5L {L = PPh3, PPh2Me, PPhMe2} have been determined by NMR spin-lattice relaxation techniques. Experimental values of axial [2π], compared with those reported for PMe3 and P(OMe)3, reveal that PMe3 is a slightly better π-acid than PPh3. Through space interactions between carbonyl and phenyl groups are insignificant since values of [2π] do not vary significantly in the series of phosphines, going from PMep3 to PPh3. Natural bond orbital (NBO) studies indicate that π-accepting capabilities for these phosphines are primarily governed by the nature of P-C anti-bonding, σ*P-C. Compared with PPh3, the better π-accepting σ*P-C, as well as the better s-donating lone-pair LP(P), in PMe3 can both be explained by the higher extents of rehybridization of the coordinated phosphorus atom. Based on this rehybridization argument, the NBO predicted order of increasing π-acidic strengths PPh3 < PPh2Me < PPhMe2 < PMe3, which cannot be clearly distinguished by NMR experiments, is ascribed to the same NBO trend of σ-donating capabilities in a synergistic manner. Effects of coordination on P-Y (Y = C, O, F) bonding strengths in phosphines (or phosphites) are depending on two conflicting effects: rehybridization of LP(P) and the hyperconjugative-like dπ → σ*P-Y back-donation.
A fast and direct competitive biomimetic enzyme-linked immunosorbent assay (BELISA) method was developed for the determination of methimazole (MMZ) in urine sample based on a molecularly imprinted film as an artificial antibody. This is the first example to monitor methimazole with a direct competitive biomimetic enzyme-linked immunosorbent assay (BELISA) method. The imprinted film was directly synthesized on the well surface of MaxiSorp polystyrene 96-well plate and characterized. The results showed that it exhibited an antibody-like binding ability, rapid adsorption speed, high stability, which was particularly advantageous and suitable for BELISA development. The BELISA method established in this paper had a higher selectivity for MMZ than for the structurally related compounds and the IC50 (calculated as the concentration giving 50% inhibition of color development) and the detection limit values under optimized experimental conditions were 70 ± 4 μg L-1 and 0.9 ± 0.04 μg L-1, respectively. The method was applied to the determination of MMZ in spiked urine sample with excellent recoveries ranging from 90% to 95%, and the imprinted film was able to be reused for 20 times without loss of sensitivity. The results obtained by BELISA correlated well with that obtained by the high performance liquid chromatography (HPLC) method.
Cupric oxide is a p-type semiconductor with a narrow band-gap which is suitable for catalysis, electrochemical cells, field emission devices and gas sensor applications. Despite considerable efforts devoted to the preparation of the nanosized CuO, there is a lack of information about ultrasonic-assisted (US) preparation methods. Nanosized cupric oxide was successfully prepared through different ultrasonic-assisted (US) preparation methods. Furthermore, the influence of preparation method on the structure, morphology and optical properties of nanosized CuO has been reported. XRD patterns were identical to the single-phase pure CuO with a monoclinic structure. The enhancement of the crystallinity and crystallite size was observed for the sample prepared through the US thermal decomposition. The absorption band of CuO nanocrystals prepared through the US liquid hydrolysis shows a clear red shift of about 40 nm compared to those obtained with other preparation methods. Our results indicated that almost spherical CuO nanoparticles with an average size of 65 nm were prepared during the US thermal decomposition, while CuO rod-like nanostructures with an average diameter of about 16 nm were obtained via the US liquid hydrolysis method. The band gap values of nanosized CuO samples were larger than the reported value for the bulk CuO. Synthesized CuO samples by US methods with adjustable and controllable properties make the applicability of cupric oxide even more versatile.
The paper presents a novel method for the flotation separation of Pb2+ with ternary association complex system prior to the determination by spectrophotometry. The effects of different parameters, such as the dosages of KI and hexa decyl trim ethyl ammonium bromide (CTMAB), various salts and acidity etc. on the flotation yield of Pb 2+ have been investigated to select the experimental conditions. The possible flotation mechanism of Pb2+ was discussed. The results showed that by controlling pH1.0, in the presence of 1.0g NaNO3, when the dosage of 0.1 mol¡¤L-1 KI solution was 1.00 mL and 0.01 mol¡¤L-1CTMAB solution was 0.50 mL respectively, the water-insoluble ternary association complex of (CTMAB)2(PbI4) which produced by Pb2+ and I-, CTMAB cation (CTMAB+) floated above water phase and liquid-solid phases were formed with clear interface, while Fe2+, Co2+, Ni2+, Zn2+, Mn2+ and Al3+ could not be floated, so Pb2+ was floated quantitatively at pH1.0. Thereby, the quantitative separation of Pb2+ from the above metal ions could be achieved. A new method of determination of trace lead by flotation separation was established. The proposed method has been successfully applied to the determination of Pb2+ in the sample of synthetic water and the flotation yield was96.3%~106.6%.
We present in this paper an extension of a recently proposed deconvolution procedure to compare directly the theoretical and experimental spectrum of a doubly excited ultra-narrow and nearly symmetric resonance in atomic photoabsorption. Our discussion is based on a set of analytical relations in terms of the variations of i) the ratio between the resonance width ¡ and the experimental energy resolution - in the limit when ¡i =- ¿ 1 and ii) the column density nl of the media in a photoabsorption experiment.
INTRODUCTION The in ter ac tion of highly charged ions (HCI) with surfaces is asub ject of in creas ing in ter est. 1-3 Ba sically, three steps are in volved in the in ter ac tion of HCIwith sur faces: (1) the for ma tion of hol low at oms or ions above sur faces; (2) the de cay of hol low at oms or ions at or be low sur faces and (3) total neu tral iza tion ofhollow at omsorionsinthebulkofma terials. 1 The for ma tion of hol low at oms or ions is strongly related to the HCI's im pact ve loc ity, in ci dent an gle and other dynamicparameters. 4 In the fi nal neu tral iza tion step, hol low at oms or ions emit the Au ger elec trons 5,6 or x-rays. 7-9 The emittedx-raycanprovide static informationofhollow at oms or ions in the bulk of ma te ri als from the en ergy po si tion and thedynamicinformationfromthespec tral inten sity. Usually, the Hartree-Fock method is used to study the en ergy struc ture of h
Various novel barbituric and thiobarbituric acid derived sulphonamides were synthesized in excellent yield via three components single pot reaction; and these were screened for in vitro urease inhibition studies against jack bean urease. The compounds 1-7 were found to exhibit a low to moderate activity whereas compounds 8-14 showed a significant activity (88.3-99.9% inhibition determined at 500 μM concentration). Structures of the synthesized compounds were confirmed by 1H-NMR, 13C-NMR, mass spectrometry and elemental analysis data.
A glassy carbon (GC) electrode modified with silver pentacyanonitrosylferrate (AgPCNF) film as a redox mediator was fabricated. Cyclic voltammetry was used to study the redox property of AgPCNF modified electrode. The modified electrode showed a well-defined redox couple due to [AgIFeIII/II(CN)5NO]1-/2-system. The effects of scan rates, supporting electrolytes and solution pHs were studied on the electrochemical behavior of the modified electrode. The feasibility of using the AgPCNF modified electrode to measure L-cysteine was investigated. It showed an excellent electrocatalytic activity towards the oxidation of L-cysteine and the anodic currents were proportional to the L-cysteine concentration in the range of 0.1 μM to 20 μM, the linear regression equation is Ipa(μA) = -68.58 - 5.78CL-cysteine (μM), with a correlation coefficient 0.998 for N = 23. The detection limit was down to 3.5 × 10-8 M (three times the ratio of signal to noise).
A series of novel β-lactams derived from natural gallic acid were conveniently synthesized via classical Staudinger ketene-imine cycloaddition reaction. Their structures were confirmed by satisfactory analytical and spectroscopic methods. The preliminary bioassay showed that some of the target compounds exhibited obvious insecticidal activity against Heliothis armigera at the dosage of 0.2 mg/mL.
We herein report a mercury-free approach for the sensitive determination of trace Pb2+ in seawater using differential pulse stripping voltammetric (DPSV) method with a novel columnar glassy carbon electrode (CGCE). Compared with the conventional disk glassy carbon electrode with the same diameter, it has much larger electrochemical area (0.627 ± 0.003 cm2). The CGCE shows good accumulation ability and consequently acceptable behavior which makes it suitable as a working electrode in the DPSV determination of Pb2+ with the great advantage of the avoidance of harmful mercury. Using acidified artificial seawater as supporting electrolyte, there was a good linear relationship between the peak currents and the concentration of Pb2+ in the range of 0.6∼140.0 μg L-1 with a detection limit of 0.3 μg/L (S/N = 3) when the accumulation time was 300 s. The method was employed to determine trace levels of Pb2+ in real seawater samples successfully.
Thiourea is an inexpensive, efficient and mild catalyst for the synthesis of Knoevenagel condensation of pyrozoles derivate. In the presence of 10 mol% of thiourea, pyrazole aldehyde react with active methylene compound under microwave-assisted solvent-free conditions at 300 W for 2-5 min to give corresponding products in good yields.
Four different seaweed extracts were employed as the dyes of dye sensitized solar cells (DSSCs) to investigate the light-electron efficiency. The sensitizers, extracted from Nannochloropsis spp., Tetraselmis spp., Gracilaria spp., and Ulvales spp., showed their light-electronic transfer ability in different light intensities. Among them, Ulvales output a higher light-voltage, about 0.4 V. The output voltage increased when light intensity increased. Gracilaria extract produced a higher output voltage at 35 Lux, but its output voltage decreased over 500 Lux. The sensitizers extracted from these seaweeds had monochromatic incident photon-to-electron conversion efficiencies (IPCE) between 23-61% in 220-260 nm wavelengths. Among them, Ulvales output higher IPCE than Tetraselmis and Nannochloropsis. SEM analysis of DSSC surfaces revealed that the efficiency of seaweed DSSCs was governed by chlorophyll size. The chlorophyll particle size of Ulvales spp. was the largest. The chlorophyll particle size of Gracilaria spp. was the smallest and yielded the lowest IPCE.
An ultra-high-pressure liquid chromatography/MS3 (UPLC-MS3) method has been developed and validated for the quantitative determination of four major TSNAs in mainstream cigarette smoke using MS3 scan mode on a hybrid triple quadrupole-linear ion trap mass spectrometer. The new method combining the UPLC with MS3 scan mode offers decreased sample analysis time and good selectivity. After mainstream cigarette smoke was collected on a Cambridge filter pad, the particulate matter was extracted with ammonium acetate solution and analyzed by UPLC-MS3 using isotopically labeled analogues as internal standards. Four TSNAs were completely separated on an Agilent XDB-C18 UPLC column using isocratic elution during a 6 min LC run time. Excellent linearity was obtained over the concentration range of 1.0-150.0 ng/mL for all TSNAs with values for correlation coefficient (r) between 0.9985-0.9994. Limits of detection (LOD) of each TSNA varied from 0.023 to 0.067 ng/mL, and lower limits of quantification (LLOQ) varied from 0.077 to 0.223 ng/mL, respctively. The recovery of each TSNA was from 89.2 to 106.8%. The method achieved excellent reproducibility with RSD 2.1-6.8% for intra-assay and 3.4-9.1% for inter-assay. This method can be used as an effective approach to significantly improve the detection capability for TSNAs in complex matrices.
Two copper(II) complexes type [Cu(en)X2](ClO4)2, where en = ethylenediamine and X = pyridine, 1 or imidazol, 2 have been synthesized and prepared on the bases of elemental analysis, spectroscopic and molar conductance measurements. The X-ray crystal analysis of these complexes demonstrated that the copper(II) ions are in square planar environments through coordination by two nitrogen atoms of the ethylenediamine and two nitrogen atoms of two pyridine or imidazol molecules and the ClO4- ions are bound weakly above and below of the molecular plane. The complexes show three ions behavior in all solvents. The complexes are soluble in various solvents and are solvatochromic. The solvatochromism of the complexes were investigated by UV-Vis spectroscopy with different solvent parameters such as DN, AN, α and β using multiple linear regression (MLR) method. The results suggested that the DN parameter of the solvent has the most contribution to the shift of the d-d absorption band of the complex 1 but in complex 2 the DN and β have almost similar importance in the observed variation in the shift of the νmax values with solvent nature.
Gold nanoparticles (AuNPs) were electrodeposited on the surface of pencil graphite (PG) by fast scan cyclic voltammetry without using any additives in acidic medium. The effect of deposition time on the size of electrodeposited AuNPs was investigated in sulfuric acid as a supporting electrolyte. The deposition time was varied by varying the scan rate, number of cycles and applied potential range. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used for characterization of PG and electrodeposited AuNPs. The results confirmed that nanosized gold particles (20 ± 8 nm) were deposited on the PG substrate with almost spherical geometry.
A validated spectrophotometric method has been developed for the determination of uranyl ion in soil samples. The method is based on the complexation reaction between uranyl ion and rifampicin in methanol-water medium at room temperature. The method is followed spectrophotometrically by measuring the absorbance at 375 nm. Under the optimized experimental conditions, Beer's law is obeyed in the concentration range of 1.35–20.25 μg mL-1 with apparent molar absorptivity and Sandell's sensitivity of 8.0 × 103 L mol-1cm-1 and 0.042 μg/cm2/0.001 absorbance unit, respectively. The interference of a large number of anions and cations has been investigated and the optimized conditions developed have been utilized for the determination of uranium(VI) in soil samples. The three sigma detection limit (n = 9) for uranyl ion was found to be 0.20 μg mL-1. The proposed method was successfully applied to the determination of uranyl ion in soil samples.
The first total synthesis of the linear diarylheptanoid 1-(4″-methoxyphenyl)-7-(4′-hydroxyphenyl)-(E)-hept-2-ene, which has a uniquely nonconjugated olefin, was achieved. The synthetic route employed an olefin cross-metathesis as a key step. Beginning with commercially available 3-(4-hydroxyphenyl)propan-1-ol, the final product was made in three steps with a 52% yield.
The thermodynamics and mechanism of the reaction of elemental mercury with ozone has been studied computationally. The effect of water and water dimer molecules on the reaction has also been investigated. For dry reaction, we obtained two pathways and geometry optimization, atoms in molecules analysis and vibrational frequencies of all component of reaction have been used for confirming of reaction mechanism. Thermodynamic variable of reaction has been calculated. For the reaction in the presence of the water, our studies focus on ozone-mercury complex reaction with water and water dimer and obtained the mechanism of reactions. Comparison of wet and dry reaction shows the energy profile of reaction decreases with water molecule correspond to experimental prediction. Calculated thermodynamic variable of all reaction shows the Gibbs free energy of reaction decreases with the number of water molecule.
We have measured, by means of ultrafast x-ray absorption and optical spectroscopy, the M-O (M=Fe, Co) and Co-N metal to ligand bond length change as a function of time and the formation and decay of the excited states and intermediate species, after excitation with a 267 nm femtosecond pulse. These experimental data combined with DFT calculations allowed us to determine the mechanism of electron transfer operating in the redox reaction of two metal-ligand complexes, [M(III)(C2O4)3]3- and [Co(III)(NH3)6 ]3+. Based on the data we find that, even though both molecules are excited into their charge transfer band, the redox reaction of [M(III)(C2O4)3]3- proceeds via intermolecular electron transfer while [Co(III)(NH3)6 ]3+ electron transfer mechanism is intramolecular.
Anodic deposition and cathodic stripping of bromide at varying concentrations in 0.1 N KNO3 medium at silver electrode was studied by constant current method. The apparent coulometric efficiency could be explained with Laitinen's model. Modified Tafel plots were given and the transfer coefficient, α, was calculated to be 0.5 for the reversible anodic step. Two distinct steps in anodic deposition of bromide were definitely observed. Reduction of oxygen with low current density in 0.1 N KNO3 and at silver electrode was examined and was found to do no harm if deaeration was done by Meites technique. Constant current potentiometry model was proposed to explain the potential concentration relation.
A green protocol has been developed for the synthesis of 1H‐pyrazolo[1,2‐b]phthalazine‐5,10‐diones by one‐pot cyclocondensation reaction of phthalhydrazide, aromatic aldehydes, and malononitrile or ethyl cyanoacetate using sulfonic acid functionalized SBA‐15 (SBA‐Pr‐SO3H) as a heterogeneous solid acid catalyst under solvent‐free conditions. A green protocol has been developed for the synthesis of 1H‐pyrazolo[1,2‐b]phthalazine‐5,10‐diones by one‐pot cyclocondensation reaction of phthalhydrazide, aromatic aldehydes, and malononitrile or ethyl cyanoacetate using sulfonic acid functionalized SBA‐15 (SBA‐Pr‐SO3H) as a heterogeneous solid acid catalyst under solvent‐free conditions.
Top-cited authors
Fang-Rong Chang
  • Kaohsiung Medical University
Chung-Yi Chen
  • Fooyin University
Che-Ming Teng
  • National Taiwan University
Ching-Kuo Lee
  • Taipei Medical University
Shoei-Sheng Lee
  • National Taiwan University