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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. [ABSTRACT FROM AUTHOR]