气相分子吸收光谱法测定土壤中铵态氮和硝态氮的含量

通过测定土壤中铵态氮和硝态氮的含量,能够为农业领域土壤精准施肥和土壤的环境保护提供重要参考。目前基于分光光度法的土壤中铵态氮和硝态氮的分析方法容易受到提取试液颜色、浑浊度、其他共存离子等干扰不能直接测定,必须进行脱色等前处理操作,费时耗力。因此,本文建立了一次性同时浸提,不经脱色处理,采用气相分子吸收光谱法测定农田土壤中铵态氮和硝态氮含量的方法。利用该方法测定农田土壤中铵态氮和硝态氮,避免了繁琐的显色反应过程,一个批次样品(50个)的分析流程仅需5h。在0.10~2.00mg/L(铵态氮)和0.20~4.00mg/L(硝态氮)浓度范围内,工作曲线线性良好;方法检出限分别为0.013mg/kg及0.002mg/kg;相对标准偏差(RSD)<1%;加标回收率为96.3%~100.7%。较之基于传统分光光度法的国家标准方法,本方法在检出限、精密度和回收率等指标方面均有显著改善,能够满足农田土壤中铵态氮和硝态氮的批量精准分析需求。

Determination of Ammonium Nitrogen and Nitrate Nitrogen in Soil by Gas Phase Molecular Absorption Spectrometry

BACKGROUND: Determination of ammonium nitrogen and nitrate nitrogen in soil makes great sense for indication of the nutrient status and environment evaluation of soil. The standard methods based on spectrophotometry are susceptible to interference from the color of the extraction test solution, turbidity, and other coexisting ions. Moreover, those methods are time-consuming due to the demand of decoloration.
OBJECTIVES: To establish a convenient and high sensitivity method for the determination of ammonium nitrogen and nitrate nitrogen in soil, based on simultaneous extraction.
METHODS: Ammonium nitrogen and nitrate nitrogen in soil were simultaneously extracted with KCl solution without decoloration, and determined by gas phase molecular absorption spectrometry.
RESULTS: 50 samples were determined within 5h due to the avoidance of the color reaction process. The dynamic linear ranges of ammonium nitrogen and nitrate nitrogen were 0.10-2.00mg/L and 0.20-4.00mg/L, respectively. The detection limits were 0.013mg/kg and 0.002mg/kg, respectively. The recoveries ranged from 96.3% to 100.7%, and the relative standard deviation was below 1%.
CONCLUSIONS: Compared with the national standard method based on traditional spectrophotometry, this method has significantly improved the detection limit, precision and recovery. The method can be widely used in the field of detection of ammonium nitrogen and nitrate nitrogen in farmland soil.