Calibration of Kjeldahl nitrogen analyzer
Xuancheng Standard Metrology Institute,Xuancheng 242000,China
摘要：建立凯式定氮仪的校准方法。根据 GB/T 33862—2017《全（半）自动凯氏定氮仪》，结合仪器的组成和原理，选取示值误差、回收率、测量重复性作为仪器的校准项目，给出参数指标和具体的校准方法。利用尿素、硫酸铵和氯化铵三种标准物质分别对同种型号的仪器进行了校准验证。结果表明，氮元素的仪器测量范围为 0.1～210 mg，示值误差在±1%内，回收率为99%～101%，测量重复性不大于0.5%。3种标准物质均可用于计量校准，氯化铵、硫酸铵标准物质的示值误差和重复性均优于尿素标准物质。验证试验结果表明，该校准方法给出的计量特性及技术指标较为合理，方法切实可行，可用于凯式定氮仪的校准。
Abstract：The calibration method of Kjeldahl nitrogen analyzer was established. According to GB/T 33862—2017 Full (semi) Automatic Kjeldahl Nitrogen Analyzer, combined with the composition and principle of the instrument, the indication error, recovery and measurement repeatability were selected as the calibration items of the instrument, and the parameter indicators and specific parameters were given. The instruments of the same type were calibrated and verified using three standard materials of urea, ammonium sulfate and ammonium chloride. The results showed that the instrument could measure nitrogen in the range of 0.1-210 mg with the indication error within ±1%, the recovery rate was 99%-101%, and the measurement repeatability was not more than 0.5%. All of the three standard materials could be used for measurement calibration. Taking ammonium chloride and ammonium sulfate as the standard materials, the indication error and repeatability were better than that with urea as the standard material. The verification test showed that the measurement characteristics and technical indicators given by this calibration method were reasonable, the method was feasible, and it could be used for the calibration of Kjeldahl nitrogen analyzers.
Keywords：Kjeldahl nitrogen analyzer; working principle; metrological characteristics; calibration; method validation
YIN Chunqian. Calibration of Kjeldahl nitrogen analyzer[J]. Chemical Analysis and Meterage，2022，31(12)：69.