石墨消解仪-自动定氮法测定植物果实中的全氮

通过测定植物果实中的氮元素含量,能够掌握植物生长状况,为提高优质果实的产量提供重要信息。目前分析测试植物果实中全氮的方法为传统凯氏定氮法,主要步骤为消解、蒸馏和滴定,消解时间约90min,蒸馏滴定时间约10～20min,分析测定过程较为繁琐,容易产生人为误差,不适于大批量植物果实样品的分析检测。为了缩短植物果实样品全氮的分析测定时间、提高工作效率,避免人为误差以及解决消解过程中样品飞溅和白烟逸出的问题,本文使用石墨消解仪对样品进行消解,加入浓硫酸和催化剂并加盖回流塞,使用全自动定氮仪进行分析测定,消解过程中样品不发生损失,白烟不逸出,消解时间约50min,蒸馏时间约3min,试剂消耗量小,相对误差和相对标准偏差均小于5%。本文建立的方法能够满足实验室快速、准确检测大批量植物样品中全氮的分析需求,已在中国地质调查局地调招标项目和河北省农用地土壤污染状况详查项目中得到了应用。

Determination of Total Nitrogen in Plant Fruits by Graphite Digestion Apparatus and Automatic Azotometer

BACKGROUND: By measuring the nitrogen content in plant fruits, the growth status of plants can be grasped and important information for improving the yield of high-quality fruits can be provided. At present, the traditional Kjeldahl method is used to determine nitrogen in plant fruits. The main steps are digestion, distillation and titration. The digestion time of traditional method is 90 minutes, and the titration and distillation time is 10-20 minutes. The determination process is complicated and produces errors, which is not suitable for the analysis of large amounts of plant fruits.
OBJECTIVES: To shorten the analysis and determination time of total nitrogen in plant fruit samples, improve work efficiency, avoid artificial errors, and solve the problems of sample splashing and white smoke escaping during digestion.
METHODS: A graphite digestion instrument was used for digestion. Concentrated sulfuric acid and a catalyst were added, the reflux plug was capped, and an automatic nitrogen determination instrument was used for analysis.
RESULTS: The sample did not splash and the white smoke did not escape. The digestion time was 50 minutes and the distillation time was 3 minutes. The reagent consumption was reduced by 2mL. The relative error and relative standard deviation were less than 5%.
CONCLUSIONS: The established method meets the needs of the laboratory to quickly and accurately detect total nitrogen in large amounts of plant samples. It has been applied in the detailed survey project of the China geological survey bidding project and the detailed investigation of the soil pollution status of agricultural land in Hebei Province.