| This paper was mainly designed to determine the nitric oxide in the medium of natural seawater. The following several aspects were carried through: (I) confirmed the determination method of nitric oxide in the medium of natural seawater- the electrochemical method; (2) modified the working electrode by two methods, confirmed the best conditions of each method and compared the two modified methods through several aspects, also compared by the ISO-NOPMC microsensor.The main results were summarized as follows:1. Nation modified platinum electrode(1) The nitric oxide in the medium of natural seawater was determined using Nafion modified platinum electrode for the first time, the best conditions are found as follows: the time of exclusion of oxygen bubbled with nitrogen for the electrochemical cell is 30min, the preparation time of saturated solution is 30min, the enrichment time is 5min and the electrochemical responses of the modified platinum microelectrode to NO were evaluated by scanning from 0.2v to Iv. The relation between the peak height and the NO concentration is linear for NO concentrations ranging from 1~76.9umol/L for Nafion modified electrode and the detection limit is 1umol/L. The experiment of precision shows that the standard deviation is 2.04X 10-2 and the relative standard deviation is 0.47%.(2) Two methods including the adsorption method and the straight drippingmethod were used to modify the platinum electrode. In the adsorption method, the time of the electrode adsorption is 7s; there is no curve if the time is too short and the curve appearing when the time is 5s. In the straight dripping method, the function of the selectivity film could be exerted as well when 2uL5% Nafion was dripped to the electrode surface,(3) The selectivity of the electrode was also studied. Nafion covering at the electrode surface as cation exchange resin could effectively prevent the disturb by some impurity ion as nitrite ion accordingly achieve the good selectivity of nitric oxide.(4) Nafion film has the function of enriching nitric oxide and also the mechanism was discussed.2. Co(salen)/Nafion modified platinum electrode(1) The nitric oxide in the medium of natural seawater was determined using Co(salen)/Nafion modified platinum electrode for the first time, the best conditions are found as follows: the time of exclusion of oxygen bubbled with nitrogen for the electrochemical cell is 30min, the preparation time of saturated solution is 30min, the enrichment time is 3min when the concentration of nitric oxide is 10-6 mol/L and 7min when 10-7 mol/L and the electrochemical responses of the modified platinum microelectrode to NO were evaluated by scanning from 0.2v to Iv. The relation between the peak height and the NO concentration is linear for NO concentrations ranging from 0.1-9.9umol/L for Co(salen)/Nafion modified electrode and the detection limit is 0.1umol/L. The experiment of precision shows that the standard deviation is 1.04X10-2 and the relative standard deviation is 0.24%.(2) Two methods including one-step and two-step methods were used to modify the platinum electrode. In the two-step method, the experiment conditionswere confirmed, namely after modified by Nafion film, the electrode was dipped in saturated solution of Co(salen) for 24h. The electric current would decrease if the dipping time were too long. At the same time, the electrodes modified by the two methods were compared; the one that modified by two-step method was better of stability and recruit, so it was used in this experiment.(3) The self-assemble of Co(salen) on Nafion film and the catalyze mechanism of Co(salen) to nitric oxide were discussed. As Co(salen) 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.3. The compare between Nafion and Co(salen)/Nafion modifiedelectrodes(1) When the concentrati...
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