The Electrochemical Determination Of Nitric Oxide In Seawater Media And The Influnces Of Nitric Oxide On Haeterosigma Akashiwo

Nitric oxide (NO), an important green house gas, is the key to damage ozonosphere and it is harmful to environment and human being. In recent, many researches have indicated nitric oxide is a new signal messenger which plays a great role in organism. The study on the function and status of nitric oxide in oceanic ecological system is very scarce for being short of effective research methods. However, it is necessary to study nitric oxide in marine for discovering the influence of nitric oxide on oceanic ecological system and understanding the process of biological nitrogen cycle. In this paper the author researched the direct methods for the measurement of NO in seawater for the first time by the use of amperometry and apply it to researching alga.This work includes: (1) confirm the determination method of nitric oxide in the medium of natural seawater-the electrocatalytic oxidation method, and discuss the measurement mechanism by voltammogram with homemade modified platinum electrodes for the first time; (2) obtain the practical determination method of nitric oxide in the medium of natural seawater by amperometry with ISO-NOPMC NO microsensors and the recovery method of the sensor for the first time; (3) study the influence of nitric oxide on Haeterosigma akashiwo, and the variation of nitric oxide in alga solution by the use of electrochemical method for the first time; discuss the relation between the NO production by Haeterosigma akashiwo and NR activity, nitrite concentration.The main results were summarized as follows:1. The study of the electrochemical determination of nitric oxide in the medium of natural seawater with homemade modified platinum electrodes(1) The straight dripping method was used to modify the platinum electrode with Nafion. Obvious oxidation of NO occurred at about 0.8Vby scanning from 0.2V to IV on the HY-1CZ polarograph. The Nafion thickness of the modified platinum electrode must be appropriate. If too thin, the stability and selectivity of the electrode will decrease; if too thick, the response current to NO will decrease.(2) The selectivity of the Nafion modified platinum electrode was discussed. As a kind of cation resin, the Nafion film can effectively prevent the oxidation of NO2~ at the electrode surface in seawater.(3) Nafion film has the function of enriching nitric oxide and the mechanism was alsodiscussed.(4) The comparison between Nafion and Co(salen)/Nafion modified electrodes indicates Co(salen)/Nafion modified electrode has the better stability, sensitivity and lower detection limit. When the concentration of nitric oxide were the same, the current on the Co(salen)/Nafion modified electrode was higher than that on the Nafion modified electrode, and the enrichment time on the Co(salen)/Nafion modified electrode was less than that on the Nafion modified electrode. These results proved that the Nafion and Co(salen) modified platinum microelectrodes showed electrocatalytic oxidation of nitric oxide in seawater.(5) The catalyze mechanism of Co(salen) to nitric oxide were discussed. As Co(salen) is a four-complexes molecule, the top and nether rooms of the plane would be empty to form axes complexation with nitric oxide so as to catalyze oxidation reaction of the nitric oxide on the electrode.2. The electrochemical detection of nitric oxide in the medium ofseawater(1) The Study about the response of ISO-NOPMC NO microsensors to nitric oxide in distilled water, Martin artificial seawater, Fleming artificial seawater, filtered seawater (0.45 m) , alga culture solution and natural seawater was carried out. The results indicate: 1) In distilled water the responses of ISO-NOPMC NO microsensors are the best, the response current to the same NO concentration is higher (the detection limit is 3.5 10mol/L (S/N>3)) and the form of the current-time curve is fine compared with that in the other mediums. In the other mediums, the form of the current-time curves get irregular along with the more and more compound complex medium, but the response...