| In view of excessive applications of fertilizer, and irrigation of waste water, the content of nitrate and nitrite are significantly high in some vegetables in some cities in China. Over-dose nitrate and nitrite will result in cancer in both people and animals. But the existing methods for determining of the content of nitrate and nitrite is very complicated, and is time consuming and work demanding. The whole process needs expensive instruments. So, the study of a simple, quick and low-cost method of the determination of the content of nitrate and nitrite is sensible both in reality.The experiment used Chinese cabbage, Pakchoi, rape, spinach, lettuce, cucumber,tomato eggplant, green pepper, radish, potato as the experiment materials, we developed the determination of the content of nitrate and nitrite and fast evaluation method, they are: electrode method and visual colorimetric analysis. Result of test is satisfaction.The electrode method uses a battery composed of nitrate ion selective electrode and calomel electrode to determine the electro-motive force (E)of the nitrate ion in vegetables. We calculated the concentration of nitrate ion through a linear regression formula. The determination of the content of nitrite is realized by oxidizing the nitrite to nitrate, this is through adding concentrated sulphuric acid and potassium permanganate solution. Through the linear regression equation, we calculated the total content of nitrate, the content of nitrite is calculated by two processes: first, plus the content of nitrate from the total,and second, multiply 0.742.The visual colorimetric analysis uses salicylic acid. We evaluated the pollution extent of the nitrate in the vegetables according to the evaluating standard of the pollution extent of the nitrate drew up by WHO and FAO. Contrasted the developing yellow color with the standard card.The determination of the content of nitrate and nitrite in vegetables using the nitrate ion selective electrode is simple, quick, and with a good selectivity, the rate of recovery for nitrate and nitrite is 93%—105% and 92%—105% respectively, this is in accord with the demanding of quantitative analysis. The relative error for nitrate and nitrite is —5.15%—4.22% and — 7 55%—7.40% respectively. Visual colorimetric analysis is simple in the process and with a low require for the reagents, in the process, no special treatment and expensive instruments are needed, the cost is low, and it is simple to manipulate. The results are satisfactory for thesemi-quantitative analysis of samples.Tt is seen ,both the electrode method and the visual colorimetric analysis are feasible for the simultaneous determination of a quantity of samples, they are not confined to the analyzers and the manipulation places, they cater to the quality control of the existing vegetables sale system in China.The study and application of a quick determination method for the nitrate and nitrite of vegetables and fast evaluation method provid scientific ,accurate ,quick ,notary date and way and import role of environmental protection, in ensuring a good health for the peoples. It also plays a important role in the aspects below: the variety and form choices of nitrogenous fertilizers, a proper application amount of nitrogenous fertilizers, the popularizing of the technique of prescription application, the coordinate application of chemical nitrogenous fertilizer and organic nitrogenous fertilizer, a scientific topdressing method, the selection of low nitrate content variety, the enhancing of saving and processing technique of vegetables. All the above are beneficial for the pretreatment of vegetables and bettering of the eating habits of the consumers.
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