Flow Injection Analysis of Nitrate and Nitrite in Vegetables

Based on the reduction from nitrate to nitrite through a Zn-C powder mixture column,a new method for the determination of nitrate and nitrite in vegetables using flow injection analysis were proposed.Samples were homogenized and extracted,and the extract was decolorized and divided into two portions.The nitrite content in one portion was directly determined by hydrochloride naphthalene ethylenediamine colorimetry,and another was determined by the same method after nitrate was reduced to nitrite.The content of nitrate was calculated by subtraction method.The linear range of nitrite was 0.12.4μg/ml,the detection limit 0.01 μg/ml,the range of relative standard deviation from 0.03% to1.8%,and the sample determination frequency 10 samples/h.