ELECTROCATALYSIS ON ELECTROCHEMICALLY PRETREATED GLASSY-CARBON ELECTRODE

The surface structure of glassy carbon electrode subjected to "galvanostat" pretreat- ment and its electrocatalytic behaviour in the presence of ascorbic acid, catechol and hydroquinone were studied by means of cyclic voltammetry, chronoamperometry, chronocoulometry and scanning electron microscopy. The electrocatalytic mechanism was discussed, which was due to the adsorption and the catalysis of functional groups at the electrode surface. Three separated peaks from the mixture of catecnol, hydroq...

RESEARCHES ON CHEMICALLY MODIFIED ELECTRODES - ELECTROCHEMISTRY OF 1-12 PHOSPHOMOLYBDIC HETEROPOLY ANION FILM MODIFIED ELECTRODE

A monolayer of 1:12 phosphomolybdic anion (PMo_(12)) was modified electrochemically on a glassy carbon electrode and its electrochemical behavior was studied with cyclic voltammetry (CV). It is shown that PMo_(12) film is adsoibed strongly on the surface of glassy carbon electrodes, H~+ ions in the solution plays an important role in the electrochemical processes of PMo_(12) film modified electrodes, whereas other anions, such as Cl~-, NO_3~-, SO_4~(2-), ClO_4~- and PO_4~(3-) etc., do not take par...

A NEW TYPE OF ION-SELECTIVE ELECTRODE FOR NONAQUEOUS SOLUTION

A new type of ion-selective electrode-water membrane system is proposed and an assumption of water membrane is confirmed. A NdCl_3 water membrane electrode has be- en made te demonstrate its applicability to the determination of Nd (PMBP)_3 (PMBP=1- phenyl-3-methyl-4-benzoyl-5-pyrazolone)in cyclohexanone. Conditions for stabilizing potential of reference electrode in nonaqueous system are optimized. It is observed that the potential response on the surface of two immiscible solution is bidirection...

INVESTIGATION OF MICROSTRUCTURE AT IRON TETRAPHENYLPORPHYRIN MODIFIED CLASSY CARBON ELECTRODE BY XPS

Microstructure of the glassy carbon surface modified with iron tetraphenyfporphyrin (FeTPP) by heat treatment has been studied by XPS,, DTA and TG. XPS spectra of Fe 2P_3\2 level in FeTPP and iron tetraphenylporphyriu/glassy carbon (FeTPP/GC) have shown that a bond can be formed between the glassy carbon surface and both the central metal iron ion and the macrocyclic, ligand, which loses its four phenyl groups during the beat treatment. The relationship between the surface mierostructure of FeTPP/GC and the...

An electrochemical DNA sensor based on electrodepositing aluminum ion films on stearic acid-modified carbon paste electrode and its application for the detection of specific sequences related to bar gene and CP4 Epsps gene

An electrochemical DNA biosensor was fabricated by immobilizing DNA probe on aluminum ion films that were electrodeposited on the surface of the stearic acid-modified carbon paste electrode (CPE). DNA immobilization and hybridization were characterized with cyclic voltammetry (CV) by using methylene blue (MB) as indicator. MB has a couple of well-defined voltammetric redox peaks at the CPE. The currents of redox peaks of MB decreased after depositing aluminum ion films on the CPE (Al(III)/CPE) and increased dramatically after immobilizing DNA probe (ssDNA/Al(III)/CPE). Hybridization of DNA probe led to a marked decrease of the peak currents of MB, which can be used to detect the target single-stranded DNA. The conditions for the preparation of Al(III)/CPE, and DNA immobilization and hybridization were optimized. The specific sequences related to bar transgene in the transgenic corn and the PCR amplification of CP4 epsps gene from the sample of transgenic roundup ready soybean were detected by differential pulse voltammetry (DPV) with this new electrochemical DNA biosensor. The difference between the peak currents of MB at ssDNA/Al(III)/CPE and that at hybridization DNA modified electrode (dsDNA/Al(III)/CPE) was applied to determine the Specific sequence related to the target bar gene with the dynamic range comprised between 1.0 X 10(-7) mol/L to 1.0 x 10(-4) mol/L. A detection limit of 2.25 x.10(-8) mol/L. of oligonucleotides can be estimated.

Preliminary analysis of grain-size populations with environmentally sensitive terrigenous components in marginal sea setting

Terrigenous components were separated from the bulk sediment of Core A7 from the Okinawa Trough and Core A37 from the Ryukru Trench and grain-size distributions of these sub-samples were analyzed. Based upon an analysis of the grain-size data of the two sedimentary sequences, grain-size populations are identified to be sensitive to sedimentary environmental changes. The modal values and size ranges of the two main grain-size populations in Core A7 are evidently different from those of Core A37, indicating the spatial variability of sediment sources and transport processes between the two places. The downcore variations in the content of the environmentally sensitive grain-size populations reveal that during the accumulation of sedimentary material the environment remained relatively stable at the site where Core A7 was collected, except for the apparent events for the formation of two turbidite layers and a volcanic ash layer. However, the sedimentary sequence of Core A37 shows six sedimentary cycles, indicating a highly variable sedimentary environment at this location.

Fabrication of Bismuth/Multi-walled Carbon Nanotube Composite Modified Glassy Carbon Electrode for Determination of Cobalt

A bismuth/multi-walled carbon nanotube (Bi/MWNT) composite modified electrode for determination of cobalt by differential pulse adsorptive cathodic stripping voltammetry is described. The electrode is fabricated by potentiostatic pre-plating bismuth film on an MWNT modified glassy carbon (GC) electrode. The Bi/MWNT composite modified electrode exhibits enhanced sensitivity for cobalt detection as compared with the bare GC, MWNT modified and bismuth film electrodes. Numerous key experimental parameters have been examined for optimum analytical performance of the proposed electrode. With an adsorptive accumulation of the Co(II)-dimethylglyoxime complex at -0.8 V for 200 s, the reduction peak current is proportional to the concentration of cobalt in the range of 4.0x10(-11)-1.0x10(-7) mol/L with a lower detection limit of 8.1x10(-11) mol/L. The proposed method has been applied Successfully to cobalt determination in seawater and lake water samples.

Ionophore Based Bismuth Film Electrode for Lead

A Nafion/ionophore, 4-tert-butylcalix[4]arene-tetrakis(N,N-dimethylthioacetamide) composite coated and bismuth film modified glassy carbon electrode. (GC/NA-IONO/BiFE) was described to determine trace lead sensitively and selectively. The characteristics of such modified GC/NA-IONO/BiFE were studied by scanning electron microscopy and cyclic voltammetry. The influence of various experimental parameters upon the stripping lead signal at the GC/NA-IONO/BiFE was explored. Under the optimized conditions, the differential pulse voltammetric stripping response is highly linear over the 0.1-8.0 nM lead range examined (180s preconcentration at -1.2V), with a detection limit of 0.044nM and good precision (RSD=5.4% at 0.5nM). Also applicability to seawater samples was demonstrated at such modified electrode. The high selectivity of ionophore coupled with the excellent electrochemical characteristics of bismuth endow the GC/NA-IONO/BiFE a promising and robust tool for monitoring of trace lead rapidly and precisely.

Sensitive and Rapid Detection of Genetic Modified Soybean (Roundup Ready) by Loop-Mediated Isothermal Amplification

Using the LAMP method, a highly specific and sensitive detection system for genetically modified soybean (Roundup Ready) was designed. In this detection system, a set of four primers was designed by targeting the exogenous 35S epsps gene. Target DNA was amplified and visualized on agarose gel within 45 min under isothermal conditions at 65 degrees C. Without gel electrophoresis, the LAMP amplicon was visualized directly in the reaction tube by the addition of SYBR Green I for naked-eye inspection. The detection sensitivity of LAMP was 10-fold higher than the nested PCR established in our laboratory. Moreover, the LAMP method was much quicker, taking only 70 min, as compared with 300 min for nested PCR to complete the analysis of the GM soybean. Compared with traditional PCR approaches, the LAMP procedure is faster and more sensitive, and there is no need for a special PCR machine or electrophoresis equipment. Hence, this method can be a very useful tool for GMO detection and is particularly convenient for fast screening.