硝态氮是植物最主要的氮源。植物体内硝态氮含量反映了土壤中硝态氮的供应情况，可作为土壤氮肥的指标。测定植物体内的硝态氮含量，不仅能够反映出植物的氮素营养情况，而且对鉴定蔬菜和以植物为原料的加工制品的品质也有重要的意义。 测定原理：在浓酸条件下，NO₃⁻与水杨酸反应，生成硝基水杨酸，硝基水杨酸在碱性条件下（PH>12）呈黄色，在一定范围内，其颜色深浅与含量成正比，可比色测定计算得硝态氮含量。
Nitrate nitrogen is the primary nitrogen source for plants. The nitrate nitrogen content in plants reflects the availability of nitrate nitrogen in the soil and can serve as an indicator of soil nitrogen fertility. Determining the nitrate nitrogen content in plants not only reveals the nitrogen nutritional status of the plants but also plays an important role in assessing the quality of vegetables and processed products derived from plant materials. Principle of determination: Under concentrated acid conditions, NO₃⁻ reacts with salicylic acid to form nitrosalicylic acid, which exhibits a yellow color under alkaline conditions (pH>12). Within a certain range, the color intensity is proportional to the concentration, allowing colorimetric determination to calculate the nitrate nitrogen content.
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