Vegetables are the main sources of nitrate and nitrite in food. The presence of nitrate and nitrite at high level may cause negative impact on health, because nitrite and nitrate when reduced to nitrite, may react with alkyl amine or amide to form carcinogenic nitrosamine. The purpose of this research was to analyze nitrite and nitrate in several vegetables in Medan City. Samples were obtained from Berastagi Supermarket. Nitrite levels were analyzed by visible spectrophotometry method at maximum wavelength of 540 nm after derivatization with sulfanilic acid and N-(1-naphthyl) ethylenediamine dihydrochloride in acetic acid solution. Nitrate was assayed as nitrite after nitrate reduced into nitrite by Zn in acidic condition. The condition for nitrate reduction was optimized using concentrated HCl, HCl 1 N, and without the addition of HCl. The results showed that the nitrate reduction process with Zn using HCl 1 N was found to be the optimal condition. The results showed that levels of nitrite and nitrate in analyzed samples varied significantly. Spinach contained the highest levels of nitrite (24.681 mg/kg) while watercress contained the lowest levels of nitrate (4.662 mg/kg). However spinach contained the highest levels of nitrate (103.73 mg/kg) while kale contained the lowest levels of nitrate (9.68 mg/kg). The results of this study indicated that the nitrate levels are higher than nitrite levels in analyzed vegetables.
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