Hailin Ge

Electrochemical chromatography —packings, hardware and mechanisms of interaction

Abstract The purpose of this review is to consider the development of the liquid chromatographic technique wherein the imposition of small electrical potentials are used to induce changes in retention, in order to effect a separation. The term electrochemical chromatography is proposed for this technique in keeping with the existing nomenclature. The available mechanisms of electrochemical control over the chromatographic behaviour are discussed with their dependency upon the type of packing material. Preparation of the stationary phases and column designs are also discussed. Recent progress using conducting polymers, such as polypyrrole, as modifiers for suitable supports is given, with the conclusion that these materials may provide the foundations for the development of electrochemical chromatography into a routine and useful analytical method.

Ion exchange properties of polypyrrole

Abstract In this work the anion exchange behavior of polypyrrole was studied. Results indicated that the ion exchange selectively series was determined by the size of the anions incorporated during polymer synthesis. In addition, changes in pH and ionic strength effected the rate of ion exchange as did application of electrical potentials to the polymer.

High-performance liquid chromatography on polypyrrole-modified silica

Abstract Bare silica and C 18 -bonded silica were modified with polypyrrole chloride and polypyrrole chloride-dodecyl sulfate. The packing materials were characterised using scanning electron microscopy, energy dispersive X-ray analysis, elemental analysis and surface area analysis. Both reversed-phase and anion-exchange chromatographic behaviour were determined using a selection of test compounds.

Electrochemically Controlled Liquid Chromatography on Conducting Polymer Stationary Phases

Abstract Electrochemically controlled high performance liquid chromatography (EC/HPLC) using a conducting polymer stationary phase, has been investigated in the present paper. Polypyrrole coated reticulated vitreous carbon (RVC) particles have been employed as the stationary phase. Chromatographic characterization has been carried out using various molecular probes. The results indicate that chromatographic retention can be altered by the imposition of small electrical potentials on the stationary phase and that such effects can be used to improve the separation of certain compounds.

Polypyrrole-coated silica as a new stationary phase for liquid chromatography

SummaryPolypyrrole chloride and polypyrrole dodecylsulfate coated-silica packing materials have been synthesized. Reverse-phase chromtographuy was employed to characterise both packings. A series of test compounds with known properties was used as molecular probes. They included benzene and derivatives, basic drugs, and polyaromatic hydrocarbons. A commericial C18 column was also used for the purpose of comparison in some cases.

Determination of trace amounts of chloramines by liquid chromatographic separation and amperometric detection

Abstract The detection of chloramines by monitoring electrochemical reduction processes on a glassy carbon electrode was investigated. Liquid chromatographic separation using a C18 column followed by amperometric or spectrophotometric detection were compared. The results indicate that amperometric detection is the more sensitive, especially for dichloramine.

Development of a polymer dispersed-mercury modified electrode

Abstract A polymer dispersed-mercury modified electrode, which was prepared by coating polypyrrole on a thin mercury film electrode using fast-sweep voltammetry, has been developed. The electrode was tested and compared with a conventional thin-film mercury electrode in a stationary cell. The new polymeric electrodes were also employed in a flow-through electrochemical cell using reversed-pulse amperometric detection. The selectivity of the polymeric electrode was modified by incorporating different counter ions during the polymerization process.

Properties of thermally treated polypyrroles

Abstract The effect of thermal treatment on polypyrrole chloride and polypyrrole dodecyl sulphate has been studied. Changes in surface texture, electroactivity, composition and polarity after thermal treatment have been determined using scanning electron microscopy, cyclic voltammetry, fast atom bombardment mass spectrometry and gas chromatography, respectively.

Use of Overoxidised Polypyrrole as a Chromium(VI) Sensor

Abstract A new Cr(VI) sensor has been developed in this work. The sensor was prepared by coating a layer of polypyrrole on a gold electrode and then oxidising the polymer film by scanning to anodic potentials. This pretreatment procedure decreased the background current usually associated with the electroactivity of the polymer. Determination of Cr(VI) using this sensor was investigated. It was found that Cr(VI) was preconcentrated upon application of an anodic potential (+0.80 V). Detection limits of the order of 10 ppb Cr(VI) were obtained.

Incorporation of various counter-ions during electropolymerization of 3-methylpyrrole-4-carboxylic acid

Incorporation of perchlorate (ClO4−), tetrafluoroborate (BF4−), hexafluorophosphate (PF6−) and p-toluene sulfonate (PTS−) into poly(3-methylpyrrole-4-carboxylic acid) (PMPC) during electropolymerization was considered in this work. Potentiodynamic, potentiostatic and galvanostatic polymerization methods were employed, and the corresponding cyclic voltammograms, chronoamperograms and chronopotentiograms were recorded. Preliminary characterization of the resultant polymers was carried out using scanning electron microscope, energy dispersive X-ray analysis and cyclic voltammetry after growth.