| The emergence of chemically modified electrode prompted the development of electrochemistry, which has become an important research direction in the field of modern electroanalytical chemistry. The aim of chemically modified electrodes is to carry out the molecular design on the electrode surface. In other words, some molecule, ion and polymer with excellent properties are immobilized on electrode surface and the electrode with specially chemical and physical properties is obtained.At present voltammetry determination of chromium focus on improving the reaction system and pay no attention to electrode modification. Solid silver-amalgam electrode modified with Diethylenetriaminepentaacetic acid (DTPA) has been fabricated to detect chromium species utilizing the electrode surface DTPA pre-extraction and the catalytic system Cr(III)-DTPA-NO3-. By use of this method, the samples need no pretreatment and just change the way of pre-concentration, the Cr(VI) and inorganic Cr(III) has been detected respectively. The peak current linear with the Cr(VI) and inorganic Cr(III) concentrations were, respectively, 5×10-9～5×10-6 mol/L and 1×10-8～5×10-6 mol/L. The detection limit and the recovery of Cr(VI) and inorganic Cr(III) were, respectively, 1.6×10-10 mol/L and 5.1×10-9 mol/L. The results suggested that this modified electrode was effective for the determination of trace amount of Cr(VI) and inorganic Cr(III).Voltammetry determination of chromium must needs a certain catalyst system or a periode preconcentration time, so this method quite difficulty to real-time and continuous determination of chromium which keeping the sample integrated and approaching to practical situation. Potentiometric method provided a convenient, fast and'on-line'analytical method. However, these electrodes suffer from the disadvantages of difficulty in fabrication, especially in miniaturization and microfabrication. One of the important aspects of using modified wire ion-selective microelectrodes is that it not only needs a very small volume of sample, but also has other advantages such as the elimination of the inner reference solution, the decrease in the time, lower cost, mechanical flexibility (i.e., the electrode can be used at any angle), and the possibility of miniaturization and microfabrication, even making intercellular or other in vivo electrochemical measurements possible. A new microelectrode for micro-amount chromium(III) determination was prepared. For this purpose, fuchsin basic was electro polymerized onto a carbon micro disc electrode (Ф200μm), diethylenetriamminepentaacetic acid (DTPA) was then self-assembled on the electrode surface by the reaction between DTPA and poly(fuchsin basic). The electrode gave a linear response in Cr3+ ions concentration range of 1.0×10-6～1.0×10-4 mol/L and has the Nernstian slope of 32.5±0.4 mV per decade. The detection limit is 3.6×10-7 mol/L. The response time of the electrode is less than 1.2 s, and it can be used for at least 2 months with limited considerable divergences in its potentials. The proposed electrode was applied for monitoring the chromium ion level in wastewater of chromate industries.Growth and adaptation ability of biology were enslaved to their nutrient uptake and emission. Membrane-transport processes was the key link of the nutrient uptake and emission processes, ion flux of the cell surface was the nutrient uptake and emission processes concrete reflection. A new all solid-state selective microelectrode for chromium(III) fluxes determination was prepared. For this purpose, fuchsin basic was electro polymerized onto a Pt micro disc electrode (Ф20μm), diethylenetriamminepentaacetic acid (DTPA) was then self-assembled on the electrode surface by the reaction between DTPA and poly(fuchsin basic). Chromium(III) fluxes along the roots of hyper-accumulator plants Leersia hexandra Swartz has been investigated. In the root zones 1.0 to 1.5 mm behind tips the chromium(III) ion influx obviously. At 1.2 mm behind tips, the concentration of the chromium(III) in daytime lower and more oscillatory then at night.The resistance of plants to metals includes avoidance and tolerance, while the organic acids with chelating ability in plants play an important role in the detoxification of metals both externally and internally. Iridium metal wire modified iridium oxide has been developed for detection of the organic acid. The dimensions and response time allowed that use this electrode (Ф20μm) in the measuring H+ fluxes along Leersia hexandra Swartz roots. H+ fluxes showed marked spatial and exhibited an oscillatory pattern. In the external metal detoxification, Leersia hexandra Swartz roots excrete organic acids into rhizosphere, and the metal pollutants are detained outside the roots by the formation of metal-organic acid complex, and their toxicity is reduced.
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