Institute of Chemistry, São Paulo State University (UNESP), Araraquara City 14800-060, São Paulo State, Brazil.
Institute of Chemistry, São Paulo State University (UNESP), Araraquara City 14800-060, São Paulo State, Brazil.
Spectrochim Acta A Mol Biomol Spectrosc. 2022 Dec 15;283:121737. doi: 10.1016/j.saa.2022.121737. Epub 2022 Aug 10.
Raman spectroscopy (RS) was used to identify and quantify different nitrogen species in fertilizers. This is a fast and inexpensive method that requires no extensive sample preparation. Urea and nitrate were determined at 1000 and 1045 cm, respectively. Calibration plots obtained for these analytes showed adequate linearity, with regression coefficients (r) of 0.9989 and 0.9976, respectively. Ammonium was determined by difference after total N determination by high-resolution continuum source flame molecular absorption spectrometry (HR-CS FMAS), which provided a calibration plot with r = 0.9960. The inline coupling of RS and HR-CS FMAS allowed for a fast sequential determination of ammonium, nitrate, and urea, with limits of detection of 0.03 mg/L ammonium, 0.03 mg/L nitrate, and 0.01 mg/L urea. Relative standard deviations were ≤ 11 %, and the external standard calibration method provided accurate results for all analytes determined in certified reference materials, raw materials, and commercial samples of fertilizers. For comparison purposes, all samples were also analyzed by traditional Kjeldahl method. The RS HR-CS FMAS method was further validated by addition and recovery experiments, which provided recoveries in the 93 - 113 % range.
拉曼光谱（RS）用于鉴定和定量肥料中的不同氮化物。这是一种快速且廉价的方法，无需进行广泛的样品制备。尿素和硝酸盐分别在 1000 和 1045 cm 处测定。这些分析物的校准曲线显示出足够的线性，相关系数（r）分别为 0.9989 和 0.9976。总氮通过高分辨率连续光源火焰分子吸收光谱法（HR-CS FMAS）测定后，通过差减法测定铵，其校准曲线的 r 为 0.9960。RS 和 HR-CS FMAS 的在线耦合允许快速顺序测定铵、硝酸盐和尿素，检测限分别为 0.03 mg/L 铵、0.03 mg/L 硝酸盐和 0.01 mg/L 尿素。相对标准偏差均≤11%，外标校准法为所有在认证参考物质、原材料和肥料商业样品中测定的分析物提供了准确的结果。为了比较目的，所有样品也通过传统的凯氏定氮法进行了分析。通过添加和回收实验进一步验证了 RS HR-CS FMAS 方法，回收率在 93-113%范围内。
