The present paper contains the reaction mechanism of the rare earth complex with 2-(2-arsenophenylazo)-7-(2, 6-dichloro-4-fluoro-phenylazo)- 1, 8-dihydroxynaphthalene-3, 6-disulfonic acid (DCF-arsenazo) studied prelim...The present paper contains the reaction mechanism of the rare earth complex with 2-(2-arsenophenylazo)-7-(2, 6-dichloro-4-fluoro-phenylazo)- 1, 8-dihydroxynaphthalene-3, 6-disulfonic acid (DCF-arsenazo) studied preliminarily with a fully automated stopped-flow analyzer. A method with a high sensitivity and selectivity is proposed for the simultaneous determination of samarium and gadolinium based on the differential kinetic reaction of the rare earth complex with DCF-arsenazo. Sm and Gd in their concentrated oxides were determined with the relative errors less than 6%.展开更多
A stopped-flow reversed flow injection method for the determination of free cyanide is proposed. Pyridine-barbituric acid mixture is injected in the flow system as reagent to form the colour species with cyanide. The ...A stopped-flow reversed flow injection method for the determination of free cyanide is proposed. Pyridine-barbituric acid mixture is injected in the flow system as reagent to form the colour species with cyanide. The flow is stopped when the reagent zone comes in the flow cell, where absorbance-time data are collected at 580nm wavelength. The linear range of the determination is 0.1 -10μg/ml CN-. The sampling rate is 60h-1 and the relative standard deviation is 1.6% (n=16) at 5.0 μg/ml CN-1 level. With satisfactory results, the proposed method was applied to the determination of free cyanide in wastewater without sample pretreatment.展开更多
A highly sensitive stopped-flow spectrophotometry kinetic method was proposed for quantification phenoxyl radicals based on their accelerating effect on the oxidation of nicotinamide adenine dinucleotide （NADH）. Phe...A highly sensitive stopped-flow spectrophotometry kinetic method was proposed for quantification phenoxyl radicals based on their accelerating effect on the oxidation of nicotinamide adenine dinucleotide （NADH）. Phenoxyl radicals generated from as low as 1×10^-8 mol/L 2,4-DCP can be readily detected with the proposed method and the detecting limit was 2.5×10^-9 mol/L.展开更多
The characteristic of Myoglobin as mimetic enzyme was studied and applied in the determination of HeO2 with o-phenylenediamine as substrate. The absorbanee obtained at 40 ℃ was found to be proportional to the concent...The characteristic of Myoglobin as mimetic enzyme was studied and applied in the determination of HeO2 with o-phenylenediamine as substrate. The absorbanee obtained at 40 ℃ was found to be proportional to the concentration of H2O2 in the range of 2.0×10^-5- 2.0×10^-7 mol/L, with a correlation coefficient of 0.999 1. The proposed meth od is simple and highly sensitive to a detection limit of 2.7 × 10^-8 mol/L. The relative standard deviations were within 5% for the determination of different concentrations of H2O2. Satisfied results were obtained in the determination of H2O2 in rainwater by this method, and the recoveries were at the range of 97.2%-105.4%.展开更多
The effects of poisoning materials on catalytic activity and isospecificity of the supported Ziegler-Natta catalyst were investigated.A minor amount of simple structure of Lewis base,i.e.,methanol,acetone,ethyl acetat...The effects of poisoning materials on catalytic activity and isospecificity of the supported Ziegler-Natta catalyst were investigated.A minor amount of simple structure of Lewis base,i.e.,methanol,acetone,ethyl acetate,was introduced into the catalyst slurry for partial poisoning catalytic active centers.It was found that the variations in deactivation power were in the order of methanol>acetone>ethyl acetate.The kinetic investigation via stopped-flow polymerization showed that poisoning compounds cau...展开更多
The effects of vanadate on human erythrocyte membrane have been investigated with stopped-flow and equilibrium fluorescence quenching techniques. The equilibrium study showed a half-quenching concentration(K 1/2 ) of ...The effects of vanadate on human erythrocyte membrane have been investigated with stopped-flow and equilibrium fluorescence quenching techniques. The equilibrium study showed a half-quenching concentration(K 1/2 ) of 0.27 mmol.L-1. The stopped-flow experiment exhibited a fast rise (tsk1/f1 S) and a slow drop (tin 1~2 min) in fluorescence. Based on the results and that from the across membrane transport of vanadate, a kinetic model is proposed which suggests that the membrane proteins experience a series of conformational changes before and during the quenching of the intrinsic fluorescence. These changes are induced mainly by three kinds of interactions: (i) the long-distance, non-specific interaction between the vanadate and the erythrocyte membrane surface, (ii) the charge interaction between the vanadate and parts of the membrane proteins, and(iii) the binding of the vanadate to some membrane proteins.展开更多
The alkali-hydrolysis of D-glucono-delta-lactone (GDL) was investigated by chiral Raman and circular dichroism (CD) spectroscopies in combination with density functional theory calculation. Based on the characteristic...The alkali-hydrolysis of D-glucono-delta-lactone (GDL) was investigated by chiral Raman and circular dichroism (CD) spectroscopies in combination with density functional theory calculation. Based on the characteristic CD bands of GDL and its hydrolysis product, the dynamics of hydrolysis was studied using stopped-flow CD method. Using chiral Raman spectroscopy (CRS), the stereochemical change of GDL owing to the hydrolysis reaction was discussed on the vibrational scale. The CRS results show that the ring-opening due to hydrolysis has a great influence on the chiral structure around the car-bonyl group, which was evidenced by the disappearance of the CRS band at 1735 cm-1 (C== O stretching vibrational mode). In addition, the change of positions and intensity of CRS bands was also observed, which was ascribed to the perturbation around the C2, C3, C4 and C5 carbons due to ring-opening. It is worthy to note that the stereochemistry of C2, C3, C4 and C5 had no fundamental change during the hydrolysis reaction, which was reflected in the maintenance of the signs of the CRS bands. Our results demonstrate that in comparison with CD technique, CRS may provide more detailed structural information of chiral molecules and open up new vistas of research for chiral reactions.展开更多
基金Supported by the National Natural Science Fundation of China
文摘The present paper contains the reaction mechanism of the rare earth complex with 2-(2-arsenophenylazo)-7-(2, 6-dichloro-4-fluoro-phenylazo)- 1, 8-dihydroxynaphthalene-3, 6-disulfonic acid (DCF-arsenazo) studied preliminarily with a fully automated stopped-flow analyzer. A method with a high sensitivity and selectivity is proposed for the simultaneous determination of samarium and gadolinium based on the differential kinetic reaction of the rare earth complex with DCF-arsenazo. Sm and Gd in their concentrated oxides were determined with the relative errors less than 6%.
基金This study was supported by the National Natural Science Foundation of China
文摘A stopped-flow reversed flow injection method for the determination of free cyanide is proposed. Pyridine-barbituric acid mixture is injected in the flow system as reagent to form the colour species with cyanide. The flow is stopped when the reagent zone comes in the flow cell, where absorbance-time data are collected at 580nm wavelength. The linear range of the determination is 0.1 -10μg/ml CN-. The sampling rate is 60h-1 and the relative standard deviation is 1.6% (n=16) at 5.0 μg/ml CN-1 level. With satisfactory results, the proposed method was applied to the determination of free cyanide in wastewater without sample pretreatment.
基金The authors gratefully acknowledge financial support from the National Natural Science Foundation of China （No. 20275027 and No. 20377032）.
文摘A highly sensitive stopped-flow spectrophotometry kinetic method was proposed for quantification phenoxyl radicals based on their accelerating effect on the oxidation of nicotinamide adenine dinucleotide （NADH）. Phenoxyl radicals generated from as low as 1×10^-8 mol/L 2,4-DCP can be readily detected with the proposed method and the detecting limit was 2.5×10^-9 mol/L.
基金Supported by the National Natural Science Foun-dation of China (20275027) the Natural Science Foundation ofHubei Province (2004ABA182) .
文摘The characteristic of Myoglobin as mimetic enzyme was studied and applied in the determination of HeO2 with o-phenylenediamine as substrate. The absorbanee obtained at 40 ℃ was found to be proportional to the concentration of H2O2 in the range of 2.0×10^-5- 2.0×10^-7 mol/L, with a correlation coefficient of 0.999 1. The proposed meth od is simple and highly sensitive to a detection limit of 2.7 × 10^-8 mol/L. The relative standard deviations were within 5% for the determination of different concentrations of H2O2. Satisfied results were obtained in the determination of H2O2 in rainwater by this method, and the recoveries were at the range of 97.2%-105.4%.
基金The authors gratefully acknowledge the Thailand Research Fund(TRF)Royal Golden Jubilee program for the financial support.
文摘The effects of poisoning materials on catalytic activity and isospecificity of the supported Ziegler-Natta catalyst were investigated.A minor amount of simple structure of Lewis base,i.e.,methanol,acetone,ethyl acetate,was introduced into the catalyst slurry for partial poisoning catalytic active centers.It was found that the variations in deactivation power were in the order of methanol>acetone>ethyl acetate.The kinetic investigation via stopped-flow polymerization showed that poisoning compounds cau...
基金Project supported by the National Natural Science Foundation of China (Grant No. 29471007).
文摘The effects of vanadate on human erythrocyte membrane have been investigated with stopped-flow and equilibrium fluorescence quenching techniques. The equilibrium study showed a half-quenching concentration(K 1/2 ) of 0.27 mmol.L-1. The stopped-flow experiment exhibited a fast rise (tsk1/f1 S) and a slow drop (tin 1~2 min) in fluorescence. Based on the results and that from the across membrane transport of vanadate, a kinetic model is proposed which suggests that the membrane proteins experience a series of conformational changes before and during the quenching of the intrinsic fluorescence. These changes are induced mainly by three kinds of interactions: (i) the long-distance, non-specific interaction between the vanadate and the erythrocyte membrane surface, (ii) the charge interaction between the vanadate and parts of the membrane proteins, and(iii) the binding of the vanadate to some membrane proteins.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 20621063, 20773123, and 20673110)Programme for Strategic Scientific Alli-ances between China and the Netherlands (Grant No. 2008DFB50130)
文摘The alkali-hydrolysis of D-glucono-delta-lactone (GDL) was investigated by chiral Raman and circular dichroism (CD) spectroscopies in combination with density functional theory calculation. Based on the characteristic CD bands of GDL and its hydrolysis product, the dynamics of hydrolysis was studied using stopped-flow CD method. Using chiral Raman spectroscopy (CRS), the stereochemical change of GDL owing to the hydrolysis reaction was discussed on the vibrational scale. The CRS results show that the ring-opening due to hydrolysis has a great influence on the chiral structure around the car-bonyl group, which was evidenced by the disappearance of the CRS band at 1735 cm-1 (C== O stretching vibrational mode). In addition, the change of positions and intensity of CRS bands was also observed, which was ascribed to the perturbation around the C2, C3, C4 and C5 carbons due to ring-opening. It is worthy to note that the stereochemistry of C2, C3, C4 and C5 had no fundamental change during the hydrolysis reaction, which was reflected in the maintenance of the signs of the CRS bands. Our results demonstrate that in comparison with CD technique, CRS may provide more detailed structural information of chiral molecules and open up new vistas of research for chiral reactions.
