摘要:

AbstractThe paper presents a novel method for the separation/enrichment of copper using microcrystalline absorption system prior to the determination of trace copper by spectrophotometry. The effects of different parameters, such as the dosages of KI and cetyltrimethyl ammonium chloride (CTMAC), various salts and acidity etc on the enrichment yield of Cu2+have been investigated to select the experimental conditions. The possible enrichment mechanism of Cu2+was discussed. The results showed that under the optimum conditions, cetyltrimethyl ammonium chloride cation (CTMAC+) reacted with I−to produce the microcrystalline matter (Ms‐M) of (CTMAC+ṁI−), Cu2+in the solution was absorbed on the surface of Ms‐M of (CTMAC+ṁI−) and reacted with I−to form the precipitation of CuI, Cu2+was completed enriched on the Ms‐M of (CTMAC+ṁI−). Thereby Cu2+was separated completely from K+, Na+, Ca2+, Mg2+, Zn2+, Ni2+, Co2+, Mn2+, Fe2+and Al3+at pH 4.0. A new method of determination of trace copper was established. The proposed method has been successfully applied to the determination of trace Cu2+in the sample of human hair, and the results agreed well with AAS method. The recoveries were 94.5% ∼ 105.6%, and

ISSN:0009-4536    

DOI:10.1002/jccs.201000053

出版商:WILEY‐VCH Verlag    

年代:2010

数据来源: WILEY

摘要:

AbstractThis report describes the capability of two facile, sensitive and concentrative methods for quantification of sub‐ppm levels of copper in different solutions using octadecyl silica bonded phase membrane (OSPM) disks. The first standpoint is based on introduction a homogenized miscellaneous solution of copper‐1‐(2‐pyridylazo)‐2‐naphtol (PAN) to the surface of an OSPM disk. The second perspective is the usual manner and is performed by impregnation or modification of the sorbent surface. All the affecting experimental variables such as pH, amount of modifier, eluent type, concentration of each metal and ligand, surfactant type, sample and eluent flow‐rate, time and disk capacity are also tested. The results reveal that the first way is considerably more time consuming. However, the second method possesses high break‐through volume (2000 mL) and lower detection limit (0.01 ng mL−1). Both the methods have been successfully applied for isolation and determination of trace copper in different aqueous

ISSN:0009-4536    

DOI:10.1002/jccs.201000054

出版商:WILEY‐VCH Verlag    

年代:2010

数据来源: WILEY

摘要:

AbstractA microchip capillary electrophoresis with amperometric detection, μCE‐EC, for the analysis of phenolic acids is described. The problem of noise‐laden signal under high electric field was tackled by adopting the end‐channel design of electrode configuration: more specifically with the end‐wrapped electrode configuration. At full stretch of effort, a finely tuned electrode could bring the detection limit well below micro molars for dopamine. At the end of the 10‐cm serpentine micro‐channel, a Pt electrode biased at +0.9 V (vs. Ag/AgCl) served as the working electrode. Injection of gentisic acid, protocatechuic acid, vanillic acid,p‐coumaric acid, caffeic acid, ferulic acid, sinapic acid and chlorogenic acid gave repeatable results: the migration time deviating within 3.80% (n = 7) and peak current between 1.45 and 4.50%. Under the optimized conditions, the detection limits for phenolic acids could be brought down to the range between 1.82 μM and 19.85 μM at S/N = 3. The regression coefficient of the calibration curve over the range between 10 and 800 μM was better than 0.995. The merits of increased efficiency with serpentine channel and improved sensitivity with end‐wrapped electrode are promising. Beer samples were tested for feasibilit

ISSN:0009-4536    

DOI:10.1002/jccs.201000055

出版商:WILEY‐VCH Verlag    

年代:2010

数据来源: WILEY

摘要:

AbstractCo‐administration of statins with angiotensin converting enzyme inhibitors is most common, since there is strong synergy between hypertension and hypercholesterolemia in terms of risk factors for the development of cardiovascular diseases. Rapid liquid chromatographic procedure proposed for analysis of captopril and statins in pharmaceutical preparations and human serum using acetonitrile:water (60:40 v/v) as a mobile phase, adjusting pH to 2.9 with UV detection at 230 nm. The advantages of this method include good and rapid separation, well resolved peaks, and only a small amount of sample is required for assay and adequate precision. The method showed good linearity in the range of 2.5‐100 μgmL−1for captopril and 0.625‐25 μgmL−1for statins with a correlation coefficient of 0.9999. The recovery of captopril and statins (rosuvastatin, atorvastatin and simvastatin) was>99.9% and>99.3%, respectively. The proposed method may be used for the quantitative analysis of captopril and statins alone or in combination in bulk drugs, dosage formulations and in

ISSN:0009-4536    

DOI:10.1002/jccs.201000056

出版商:WILEY‐VCH Verlag    

年代:2010

数据来源: WILEY

摘要:

AbstractThe dehydration, thermal decomposition and transition phase stage of Zn(II)‐diclofenac compound were studied by simultaneous TG‐DTA and DSC techniques. The TG and DSC curves of this compound were obtained with the mass of sample of 2 and 5 mg. Additionally, DSC curves were carried out in opened and closed α‐alumina pans under static and nitrogen atmosphere. The DTA and DSC curves show that this compound possesses exothermic transition phase between 170‐180 °C, which it is irreversible (monotropic reaction). The kinetics study of this transition phase stage was evaluated by DSC under non‐isothermal conditions. The obtained data were evaluated with the isoconversional method, where the values of activation energy (Ea/ kJ mol−1) was plotted in function of the conversion degree (α). The results show that due to mass sample, different activation energies were obtained. From these curves a tendency can be seen where the plots maintain the same profile for closed lids and almost run parallel

ISSN:0009-4536    

DOI:10.1002/jccs.201000057

出版商:WILEY‐VCH Verlag    

年代:2010

数据来源: WILEY

摘要:

AbstractThe sol‐gel technique was used to construct copper hexacyanoferrate (CuHCNF) modified composite ceramic carbon electrodes (CCEs). The modified CCE was prepared manually by carefully mixing the dispersed graphite powder with Cu powder. Copper hexacyanoferrate (CuHCNF) film has been deposited on the surface of CCE by a simple electroless dipping into a potassium hexacyanoferrate solution method. The cyclic voltammograms of the resulting surface modified CCE under optimum conditions show a well‐defined redox couple due to the K2CuII[FeIII/II(CN)6] system. The electrochemical properties and stability of the modified electrode were investigated by cyclic voltammetry. The effect of different alkali metal cations in the supporting electrolyte on the behavior of the modified electrode was studied and the transfer coefficient (α) and charge transfer rate constant (ks) for the electron transfer between the electrode and modifier layer were calculated. The experimental results show that the peak potential and peak current vary with different alkali metal cations. An extensive study showed that the response of the modified electrode is not affected within a pH range of 2‐8. The modified electrode was used for electrocatalytic determination of sulfite in hard sugar

ISSN:0009-4536    

DOI:10.1002/jccs.201000058

出版商:WILEY‐VCH Verlag    

年代:2010

数据来源: WILEY

摘要:

AbstractThe synthesis of (±)‐curcuphenol1, (±)‐curcudiol2, (±)‐curcuhydroquinone3and (±)‐curcuquinone4had been achieved, in which the Johnson‐Claisen rearrangement was use

ISSN:0009-4536    

DOI:10.1002/jccs.201000059

出版商:WILEY‐VCH Verlag    

年代:2010

数据来源: WILEY

摘要:

AbstractIn recent years, on‐line coupling of separation and activity determination techniques has been achieved by mixing a free radical solution with the eluate of an HPLC column. Such techniques enable the rapid and selective detection of radical scavenging substances in the sample preparation. This study investigates the antioxidant properties of the leaves ofKoelreuteria henryiL. using a microarray reader and HPLC. The antioxidant, 1,3,4,5‐tetra‐O‐galloylquinic acid(1), was first isolated from this plant and estimated using LC‐MS/MS and NMR methods. The scavenger activity of (1) was then determined using 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical and xanthine oxidase (XOD) assays, producing an IC50of 7.1 μM and 6.7 μM, respectively. Results show that this compound has an excellent antioxidant effect in comparison with quercetin.This study shows that it is possible to rapidly identify the antioxidant constituents ofK. henryiL. using the hyphenated DPPH (or XOD) assays and

ISSN:0009-4536    

DOI:10.1002/jccs.201000060

出版商:WILEY‐VCH Verlag    

年代:2010

数据来源: WILEY

摘要:

AbstractThe effective utilization of waste rice husk requires detailed studies on the kinetics and mechanism of their thermal and chemical treatment. The present work is a comparative study on the thermo‐chemical and kinetic characteristics of thermal degradation of raw and treated with NaOH rice husk. The optimal conditions for extraction of SiO2from rice husk in the form of Na2SiO3were determined using thermal analysis (TA), scanning electron microscope (SEM) and elemental analysis. The experiments were carried out under conditions of non‐isothermal heating in air and nitrogen atmosphere. Using different kinetic models, the values of the effective kinetic parameters, characterizing the destruction process were determi

ISSN:0009-4536    

DOI:10.1002/jccs.201000061

出版商:WILEY‐VCH Verlag    

年代:2010

数据来源: WILEY

摘要:

AbstractA set of descriptors was derived from a matrix of three structural variables of the natural amino acid, including Van Der Waal's volume, net charge index and hydrophobic parameter of side residues. They were selected from many properties of amino acid residues, which were the primary properties to influence the interaction between peptides and its protein receptor. They were then applied to structure characterization and QSAR analysis on agiotensin‐converting enzyme inhibitor di‐peptides by using orthogonal signal correction (OSC) method combined with partial least squares (PLS) method. The results of QSAR analysis on di‐peptides obtained are as following: the cross‐validation correlative coefficient (Q2) was 0.817, and the correlative coefficient (R2) was 0.838, and the root mean‐square (RMS) was 0.410. Test sets of peptides were used to validate the quantitative model, and it was shown that all these QSAR models had good predictability for outside samples. The results showed that, in comparison with the conventional descriptors, this descriptors was a useful structure characterization parameter for peptide QSAR analysis, and also showed that the OSC‐PLS method is better than the traditional

ISSN:0009-4536    

DOI:10.1002/jccs.201000062

出版商:WILEY‐VCH Verlag    

年代:2010

数据来源: WILEY