A New Tool in Metabolism Research—Combination of OPLC On-Line Radioactivity Detection with HPLC—RD Technique

JPC – Journal of Planar Chromatography – Modern TLC - This paper reports a recently developed technique, coupling of optimum-performance laminar chromatography (OPLC) with online...     

An Unexpected Frequency Response of A Piezoelectric Quartz Crystal Sensor to the Density and Viscosity of the Liquid

An unexpected frequency response for a piezoelectric quartz crystal (PQC) sensor to liquid density and viscosity was reported. For a PQC oscillating in a liquid phase, the frequency shifts (△f) show a wave-shape response to liquid density (p) and viscosity 03) in fine structure, ifthe longitudinal wave effect was not eliminated. This result is different from the well-knownlinear relationship between of Af and (ρη)1/2. An oscillating frequency-temperature curve of thesensor was observed and explained.     

Preparation of A New Fiber by Sol-gel Technology in Solid-phase Microextraction （SPME）

The sol-gel technology is applied for the preparation of solid-phase microextraction (SPME) fiber. The fiber demonstrates high thermal stability, efficient extraction rate and the selectivity for non-polar or low-polar analytes. Efficient SPME-GC-FID analyses of benzenetoluene-ethylbenzene-xylenes (BTEXs) and low-polar halocarbon were achieved by the sol-gel coated DSDA-DDBT-TiO2 fiber. Some parameters of the SPME fiber for the determination of halocarbon in aqueous sample were investigated.     

Heterophase Reactions of Hydrazine Vapor with Copper(I) π-Complexes at the Surface of a Piezoelectric Quartz Crystal

Quartz Crystal Microbalance (QCM) was used to study heterophase reactions of hydrazine vapor with solid copper(I) -complexes Cu₂Cl₂ · DVB, CuCl · AA, (HDAA)CuCl₂, and Cu(HMA) · H₂O (where DVB is CH₂=CH-C₆H₄-CH=CH₂, AA is CH₂=CH-CH₂-NH₂, HDAA is (CH₂=CH-CH₂)₂NH₂ ⁺, and HMA is the HOOC-CH=CH-COO^-. It was found that all the complexes can add hydrazine reversibly. However, in contrast to ionic complexes, molecular complexes gradually decomposed while reacting with the vapor of N₂H₄. The kinetic parameters such as the rate constants of forward and reverse heterophase reactions were determined. Complex Cu(HMA) · H₂O was found to be most sensitive to the vapor of N₂H₄.     

In Situ Monitoring of the Generation of Monodisperse Silica Particles during the Hydrolysis of Tetraethyl Orthosilicate with Piezoelectric Quartz Crystal Impedance Analyzer

The piezoelectric quartz crystal(PQC)impedance analyzer was used to monitor in situ the generation of monodisperse silica particles during the hydrolysis of tetraethyl orthosilicate (TEOS) and their adsorption onto and Au electrode in alcohol solutions containing water(6-15mol/L)and ammonia(0.2-2.0 mol/L).The equivalent circuit parameters,the resonance frequencies and the half-peak width values of the conductance spectra of the PQC resonance were obtained.The resonant frequency decreased notably while the motional resistance changed very slightly(within 1Ω during the hydrolysis reaction,suggesting that the mass effect dominated the adsorption of generated monodisperse silica particles on the gold electrode in this system.Changes in f0 indicated that the ammonia concentration affected the hydrolytic reaction obviously,and the influence of water concentration on the reaction was small while the water was significantly excessive.Kinetics of monodisperse silica particle adsorption occurring at the electrode i solution interface was analyzed using a first-order reaction scheme.In addition,the electrolyte-induced precipitation of the monodisperse silica of adsorbed particles per area and the converge of monodisperse silica particles were obtained from scanning electron nicroscope(SEM)observations.     

A New Method for Decreasing Mass Limit of Detection and Increasing Number of Theoretical Plates in Capillary Electrophoresis with Amperometric Detection

Much attention has been focused recently on pushing down the limit of detection (LOD)1-3. LOD in terms of amount is a combination of concentration LOD and the volume of sample required. The detection of small amount of sample can be achieved by reducing the sample volume, lowering the sample concentration LOD or a combination. Sampling with capillary can reduce sample volume to nL-pL level. To lower the concentration LOD is related to improve the signal-to-noise ratio. In the prese…     

A New Method for Decreasing Mass Limit of Detection and Increasing Number of Theoretical Phates in Capillary Electrophoresis with Amperometric Detection

A new method aws developed to decrease the mass limit of detection (LOD) and increase the number of theoretical plates(N)in capillary electrophoresis with amperometric detcction.When the single microcylinder electrode,the 10 μm ID capillary with the etched detection end and the in-capillary alignment were used,the mass LOD for phenol was reduced 124 times and N was increased 36 times in comparison with the normal situation.     

The Crystal Structure of a Potassium Channel— A New Era in the Chemistry of Biological Signaling

The similarity to crown ethers is apparent when the arrangement of the oxygen atoms of the carbonyl groups of the protein backbone in the structure of the potassium channel (see schematic drawing of a section of the structure) found in the bacterium Streptomyces lividans is considered. This particular part of the channel pore acts as the selectivity filter, with the permeability of the channel for K⁺ being as much as 10 000 times greater than for the Na⁺ ion. In fact, in this area of the structure two K⁺ ions are located, a feature that enables high flux through the channel.     

A Quartz Crystal Microbalance Characterization of Metal‐Oil Interfaces and Interactions with Wax Molecules

The solid‐liquid interface between stainless steel and model petroleum fluids is investigated at isothermal conditions using a quartz crystal microbalance. AISI 316 (Fe/Cr18/Ni10/Mo3) stainless steel is chosen to represent the metal surface. Paraffin components dissolved in dodecane constitute the petroleum fluid phase. Commercial macro‐crystalline and micro‐crystalline waxes provide primarily linear and branched paraffin components, respectively. Paraffin solubility conditions are established through a van't Hoff relationship. Model fluids prepared with the single‐component alkanes n‐C₃₆ or n‐C₃₀ paraffin provide well‐defined solubility conditions. Monitored changes in resonance frequency and energy dissipation of the quartz crystal resonator immersed in the model fluids confirm that no continual deposition of paraffin components occurs at isothermal conditions. Solid paraffin crystals dispersed in solution show no adherence to the stainless steel surface. The absence of attractive interactions between the stainless steel surface and the dispersed paraffin crystals suggests that a surface adsorption and/or surface nucleation mechanism is responsible for the formation of incipient paraffin wax deposits under nonquiescent conditions.     

A New Voltammetric Enzyme Immunoassay System for the Detection of Alkaline Phosphatase

Enzymes are widely used as labels in immunoassay and especially useful at low concentrations of the analyte in the sample. Most routine detection methods are based on the formation of color or fluorescent products, which are determined by spectropho-tometry or fluorometry, respectively. Electrochemical detection has been applied to the enzyme immunoassay with the potentials of combining the low detection limits and good selectivity of electroanalytical chemistry with the specificity of immun…     

Synthesis,Crystal Structure and Biothiols Detection Capability of a New “off-on” Fluoresent Probe

Biothiols such as cysteine(Cys), homocysteine(Hcy) and glutathione(GSH) act as critical roles in maintaining biological redox homeostasis, which is crucial for a plenty of physiological and pathological processes. Therefore, the detection of biothiols is very important and beneficial for many applications. Herein, we have designed and developed a new crystal dimethyl 4-(2,4-dinitrophenylsulfonyloxy)pyridine-2,6-dicarboxylate(P) with 2,4-dinitrobenzene-1-sulfonyl(DNBS) pendant for light-up and detection of biothiols(Cys was selected as the analyte model). The fluorescence "off-on" switch is triggered by the cleavage of DNBS unit by the interaction with biothiols via nucleophilic aromatic substitution reaction. The turn-on fluorescent probe exhibited excellent selectivity and sensitivity toward biothiols.     

A New Glucuronidated Metabolite of Andrographolide in Human

A new andrographolide metabolite 1 was isolated from human urine samples after oral administration. The structure was determined to be 3-carbonylandrographolide-19-O-β-D-glucuronide on the basis of chemical evidences and spectral analysis, especially by 2D-NMR techniques.     

A Study on Adsorption of Electrogenerated Cystine Precipitate onto An Electrode using Electrochemical Quartz Crystal Impedance System

Insiluquartzcrystalimpedance(QCI)measurementduringelectrochemicalperturbationshasfoundwideapplicationsininvestigatingmetalandpolymerdepositionetc'-',asitprovidesmultidimensionalinsitupiezoelectricinformation.QCIanalysishasbeenbasedontheButterworth-VanDyke(BVD)equivalentelectricalcircuitcomposedofamotionalarmandastaticarminparallel.Themotionalarmcontainsthreeequivalentcircuitelementsinseries,namely,themotionalresistanceRI,themotionalinductanceL,andthemotionalcapacitanceC,,whilethestaticar…     

Capillary Electrophoretic Determination of Jinggangmycin A in Formulations Using Direct UV Detection

A simple, fast and reliable method was developed for the analysis of jinggangmycin A （validamycin A） in commercial formulations. The running buffer used was acetate buffer （100 mmol/L, pH 4.7） with 15 kV as the applied voltage. The detection was achieved by using direct UV mode at 200 nm and the detection limit was 0.2 μg/mL. Linearity in the concentration range of 5-500 μg/mL was excellent （RE 〉 0.999）. The run-to-run repeatability （n = 3）, as expressed by the relative standard deviation （RSD） for migration times and peak areas were less than 0.5% and 3.0% respectively. The mean recovery ranged from 97.2% to 101.4%.     

Crystal Structure of Carboxypeptidase a Complexed with an Inactivator in a New Crystalline Form

1INTR0DUCTIONInrecentyears,zinc-containingmeta1loenzymeshavereceivedspecialattentionbecauseoftheroletheyplayintheetiologyofmanyseriousdiseases.Theyserveastargetsinthedesignoftherapeuticallyusefulinhibitorsoftheseenzymes.Inthisre-spect,carboxypeptidaseA(CPA),awell-studiedzinc-containingmetalloex-opeptidase,bearsanunusualimportancebecauseitservesasamodelformanymetal-loenzymes.Thetertiarystructure0fCPAinc1udingthatoftheactivesitehasbeenwellcharacterizedalth0ughthecataIyticmechanismatthemo…     

The Synthesis of 1－（4－（N－methylsulfamylmethyl）phenyl－4－ethoxycarbonyl－2－methyl－pyrrole．A New Method of Pyrrole Synthesis

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Synthesis and Crystal Structure of A New Armed-tetraazacrown Ether and Its Liquid Membrane Transport of Alkali Metal Cations

Introduction　　Transportofcationsacrossanorganicliquidmem branewhichseparatestwowaterphaseshasbeenexten sivelyinvestigated .1Thesyntheticmacrocyclicligands ,suchascrownethers ,areusuallyusedasmodelcarrierstomimicthenaturallyoccurringantibioticmacrocycleswhichhavebeenshowntoalterthepermeabilityofbiologicalmembranestocertaincations .2 ,3 Thus ,theyhaveimpor tantapplicationsinbothchemistryandbiologytoselectivecomplexationofvariousmetalcations .4 ,5Itwasreportedthatthedivalenttransition metalcomp…     

A New Advance in Preparation of Mo-S(O) Clusters

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A New Electrochemical Sensor Based on Carbon Black Modified With Palladium Nanoparticles for Direct Determination of 17α-Ethinylestradiol in Real Samples

Electrochemical sensors to quantify concentrations of emerging pollutants have attracted great attention from the industry and scientific community. Nanomaterials such as carbon black have been applied in sensors to identify substances that are toxic to the environment and human health due to their excellent electroanalytical properties. The aim of the study was to develop a novel electrochemical sensor for the endocrine disruptor hormone determination. To our knowledge, for the first time the synthesis of material based on carbon black containing immobilized palladium nanoparticles, with the application for the hormone ethinylestradiol, is reported in the literature. The material was synthesized, characterized, and applied to the determination in tap water and human urine of the synthetic hormone 17α-ethinylestradiol (EE2), which is currently considered an emerging pollutant. The morphology, structure and electrochemical performance of the sensors were characterized by scanning electron microscopy (SEM) and cyclic voltammetry (CV). Differential pulse voltammetry (DPV) in sodium phosphate buffer solution at pH 5.0 allowed the generation of a method to quantify the concentration of 17α-ethinylestradiol in a linear range of 0.5–119.0 μmol L⁻¹, obtaining 81.0 nmol L⁻¹ of calculated limit of detection (LOD). The system was efficient in detecting 17α-ethinylestradiol in real urine samples and showed no interferences for ascorbic acid, uric acid, progesterone, and dopamine. It is noteworthy that the results obtained showed good recovery values, considering that the urine samples were not previously treated or pre-concentrated, which suggests the development of an electrochemical sensor that works in situ and in real time to monitor relevant substances in the control clinical and environmental, with the possibility of point-of-care analyses.