On-Plate Electrochemical Detection for Thin-Layer Chromatography

Abstract

Voltammetric electrochemical detection (ECD) coupled with thin-layer chromatography (TLC) was demonstrated for the quantification of trace organic compounds directly on a TLC plate. the electrochemical detection solvent was a thin layer of aqueous potassium chloride. For undeveloped plates, detection limits for p-anisidine and p-phenetidine were 10 ng and 13 ng, respectively. Linearity was demonstrated over nearly 2 orders of magnitude. After development, detection limits increased by approximately a factor of ten. Advantages of this method over other quantitative TLC methods include sensitivity, speed, simplicity, and cost. in addition, this method is selective for electrochemically active compounds. Major sources of experimental error include spot size reproducibility, working electrode placement, and supporting electrolyte film thickness.     

Determination of Pongamol and Karanjin in Karanja Oil By Reverse Phase Hplc

ABSTRACT

Pongamol and karanjin, naturally present in karanja (Pongamia glabra) oil possess potential UV A and UV B sunscreen activities, respectively. A reverse phase high performance liquid chromatography (RP-HPLC) method has been developed for direct estimation of these constituents of karanja oil. This method of analysis requires no sample preparation of active ingredients. The analysis uses methanol, water and acetic acid in the ratio of 85: 13.5: 1.5 as mobile phase at a flow rate of 0.5 ml/ min on a Kromasil 100 C18 column, ex Tracer (250mm X46mm, particle size 5 microns) and dual wavelength detection at 350 and 300 nm. 2-ethylhexyl-p-methoxy cinnamate (Parsol MCX) was used as the internal standard. The identical UV spectrum of the chromatographic region (upslope, apex and downslope) confirmed that the analysis was free from substrate interference. The detection limits for pongamol and karanjin were found to be 0.1 μg/ml.     

Potentiometric Flow-Injection Determination of Sugars Using a Metallic Copper Electrode

Abstract

The determination of reducing sugars is shown to be possible by use of potentiometric detection with a metallic copper indicator electrode by either flow-injection analysis (FIA) or high-performance liquid chromatography. Various sugars including arabinose, maltose, sorbose, glucose, fructose, sucrose, lactose and xylose, give an electrode response when injected into different carrier streams composed of cupric ions in weakly complexing ligand solutions comprised of either ammonia or tartrate. Optimization of response depends on flow-rate, temperature, pH, and concentrations of carrier components. Chromatography using a cation-exchange column and post-column addition of carrier reagents similar to those used for FIA is demonstrated to give detectable separation of four sugar components with umole injection quantities.     

Potential propelling and rotating functions of propeller-type complexes. III. Detection of the propelling motion in fac-tris(S-2,3-diaminopropionato)cobalt(III) in an aqueous solution upon IR irradiation

Circular dichroism spectra of the fac and mer isomers of tris-cobalt(III) complexes of S-2,3-Hdap (Hdap?=?diaminopropionic acid); fac and mer-[Co(S-dap)₃] (Λ or Δ), and [Co(en)₃]³⁺ (Λ or Δ, en?=?ethylenediamine) in an aqueous solution without and upon IR irradiation were measured. The detection of the propelling motion that corresponds to circular dichroism spectral changes of the propeller-type complex, fac-[Co(S-dap)₃] in an aqueous solution upon IR irradiation gave good agreement with the computer-simulation result, that is, the propelling (translation and rotation) motion occurs in propeller-type metal complexes in aqueous solution as a consequence of an appropriate energy supply, which had been obtained by theoretical study based on molecular dynamics (MD) simulations by the use of AMBER 6 program.     

适配体生物传感器在病原微生物检测中的应用

适配体是通过指数富集系统进化技术(SELEX)体外筛选得到的一类能够特异性地结合小分子物质、蛋白,甚至整个细胞的寡核苷酸序列.由于具有制备简便、易于修饰、稳定性好等特点,适配体已广泛应用于构建生物传感器,实现对病原微生物的识别和检测.本文在阐述适配体基本原理的基础之上,结合近年来病原微生物适配体研究领域的最新研究成果,综述以病原微生物为目标的适配体筛选技术的最新进展;列举目前已经筛选获得的病原微生物(原生生物、病毒、细菌)适配体;综述适配体生物传感器在病原微生物检测中的应用.并展望了适配体生物传感器在病原微生物检测领域的发展趋势.     

Detection of Galactose and Lactose by a Poly(Amphiphilic Pyrrole)-Galactose Oxidase Electrode

Abstract

The entrapment of galactose oxidase (GAO) on an electrode surface by coadsorption with a cationic amphiphilic pyrrole and electropolymerization of this pyrrole monomer is described. This simple and rapid procedure for biosensor construction provides very fast responsive and sensitive GAO-based sensors to galactose and lactose. The electrode response is based on the electrochemical detection of enzymically generated hydrogen peroxide. The stability, optimum pH and selectivity of the bioelectrode as well as the characteristics of the immobilized galactose oxidase have been determined. Poly(amphiphilic pyrrole) films have been electrogenerated on the surface of the bioelectrode and the effect of such additional coatings on the biosensor selectivity have also been examined.     

废渣中Pb、Cr、Ba、As测定方法的改进

本文利用高频电感耦合等离子体－发射光谱仪直接测定了印钞厂废渣中的Pb、Cr、Ba、As4种微量元素。方法简便、快速、可靠,具有良好的精密度和准确度。相对标准偏差为1．3％－5．8％,回收率为94％－103％。测定结果令人满意。     

Thermal decomposition of silica based surface compounds as a source of volatile standards. A new approach to the generation of gaseous calibration mixtures

A new approach to the preparation of standard gaseous mixtures based on thermal decomposition of surface compounds, has been reviewed. The method is used to prepare standard mixtures containing volatile analytes such as thiols, isothiocyanates, carbon monoxide, carbon dioxide, ammonia, amines, ethylene and methyl chloride. The method enables the preparation of the standard immediately before a calibration step. It is specially useful for the generation of standard mixtures containing volatile, malodorous, unstable and toxic compounds. Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September 1–3, 1999     

Liquid chromatographic separation of fluoroquinolone antibacterials used as veterinary drugs

Summary A liquid chromatographic method has been developed to separate a series of quinolones which are widely used as veterinary drugs: danofloxacin, difloxacin, enrofloxacin (and its metabolite ciprofloxacin), marbofloxacin, norfloxacin and sarafloxacin. Separation was performed by using an end-capped high-purity silica-based C₈ column and a mobile phase consisting of acetonitrile-aqueous oxalic acid buffer solution. In order to establish the optimal conditions for an isocratic separation, a three-factor Doehlert experimental design was applied. Gradient elution was applied which reduced analysis time. Figures of merit of the method proposed, with fluorimetric detection, were evaluated.     

近红外光谱在转基因玉米检测识别中的应用

随着转基因食品的推广应用,人们越来越关心其食用安全性。以转基因玉米及其亲本为实验材料,借助于近红外光谱仪对转基因玉米及其亲本进行了识别分析：扫描区间为12 000～4 000 cm-1,分辨率为4 cm-1,扫描次数为64次;以三层误差反向传播算法(简称BP算法)进行数据处理。结果显示通过扫描光谱及数学和计算机软件分析,非常准确、方便地识别了转基因农产品。所以通过近红外光谱所建立的转基因BP-网络识别模型完全可用于实际应用。近红外分析还具有无污染、成本低等优点,是一种极具前景的转基因食品安全检测识别技术。