离子选择电极阵列测定土壤中硝态氮

土壤硝态氮反映土壤短期氮素供应水平,实时了解土壤硝态氮的含量为精准农业和农业面源污染防控提供支撑,因此,在线实时检测土壤硝态氮方法突破就显得十分迫切。土壤硝态氮中的硝酸根离子在土壤中的高水溶性和流动性为全固态硝酸根离子选择电极高敏感检测土壤中硝态氮提供了条件,固态硝态氮离子选择电极的离子选择膜反应硝酸根离子在被测溶液中的浓度。采用全固态硝酸根离子选择电极ELIT NO₃^-,且与温度电极和pH电极融合组成电极阵列对土壤饱和溶液中的硝酸根离子进行检测。设计了高输入阻抗运算放大电路对电极信号进行采集,并通过微处理控制蠕动泵完成土壤硝态氮待测溶液连续流动测定及实时传输结果。实验结果表明,电极响应时间≤15 s,斜率-51.63 mV/decade,线性范围10^-5~10^-2.2 mol/L,最低检测限10^-5.23 mol/L。相对标准差在0.78%~4.5%,加标回收率均在90.0%~110%。与紫外可见分光光度法测试结果相比,相关系数(R²)为0.9952,为土壤硝态氮在现场检测奠定技术基础。

Determination of Nitrate Nitrogen in Soil by Ion-Selective Electrode Array

Soil nitrate nitrogen reflects the short-term soil nitrogen supply level,real-time determination of nitrate nitrogen is a powerful method for precision agriculture and reducing agricultural non-point source pollution.High water solubility and mobility of nitrate ions in soil,it provides the conditions for the rapid and sensitive detection of nitrate nitrogen in soil by all-solid ion selective electrode.The all-solid nitrate ion selective electrode was optimized and fused with temperature electrode and pH electrode to form an electrode array for the detection of nitrate nitrogen in saturated soil solution.An operational amplifier with high input impedance is designed to collect the electrode signal,the continuous flow measurement of soil nitrate nitrogen solution to be measured and the transmission of test results were completed by controlling the peristaltic pump through micro-treatment.The experimental results show that the electrode response time is less than or equal to 15 s,the slope is-51.63 mV/decade,the linear range is 10^-5—10^-2.2 mol/L,the minimum detection limit is 10^-5.23 mol/L,the relative standard deviation of standard addition is within 0.78%—4.5%,and the recovery of standard addition is within 90.0%-110%.The correlation coefficient(R²)was 0.9952 with the national standard method of ultraviolet-visible(UV-Vis)spectrophotometry is in line with the development requirements of on-site measurement equipment.