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181.
Nanocomposite electrodes offer exciting new possibilities in electroanalytical chemistry. In this preliminary study, nanocomposite electrodes made of carbon nanofibers and black wax were characterized and investigated as novel substrates for metal deposition and stripping processes. Carbon nanofibers were grown from ethylene-hydrogen gas mixtures over Fe-Ni-Cu (85:10:5) nanoparticle catalysts at 600 degrees C and then embedded in Apiezon black wax under vacuum at 140 degrees C. The resulting nanocomposite electrodes showed (i) good conductivity, (ii) a wide potential window in aqueous solutions, (iii) low background currents, (iv) near steady state voltammetric responses with substantial Faradaic currents and (v) sharply peaked fast scan metal stripping responses. Zinc is a notoriously difficult metal to determine in aqueous solutions, because its deposition and stripping are accompanied by hydrogen evolution at extreme negative potentials. It therefore provided a challenging test for our new nanocomposite electrode. Although numerous complications associated with the hydrogen evolution process could not be eliminated, remarkably clear voltammograms could be obtained even at scan rates of 40 V s(-1). 相似文献
182.
In order to confirm the solution structure of [(GS)2AsSe]− (GS = glutathione), we have investigated the retention behaviour of a [(GS)2AsSe]−/oxidized glutathione (GSSG) mixture on a Sephadex G‐25 (SF) column with Tris buffers (0.1 mol dm−3, pH 8.0) containing various surfactants at concentrations above the critical micellar concentration (CMC): hexadecyltrimethlammonium bromide (HDTAB; 30, 40 and 50 mmol dm−3); dodecyltrimethylammonium bromide (DDTAB; 50 mmol dm−3); and sodium lauryl sulfate (SLS; 50 mmol dm−3). An inductively coupled plasma atomic emission spectrometer (ICP AES) provided simultaneous on‐line detection of arsenic, selenium and sulfur in the column effluent. The chromatographic retention behaviour was used to investigate the association of both compounds with the positively charged micelles (HDTAB and DDTAB mobile phases). The relative strength of association with the micelles provided insight into the effective negative charge on [(GS)2AsSe]− and GSSG. The chromatograms obtained with 50 mmol dm−3 HDTAB indicated that two glutathione molecules are associated with the elution of an arsenic–selenium compound. Combined, these chromatographic data strongly support the spectroscopically derived solution structure of [(GS)2AsSe]−. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献