基于斜率-截距校正算法的番茄营养液ISE监测

摘要

利用斜率-截距校正算法(SBC)解决离子选择电极连续在线测量电势漂移问题,结合Nernst线性模型预测无土栽培番茄苗期至果期营养液NO3-N、K+、Ca2含量变化.结果表明:SBC校正算法可有效减少离子选择电极(ISE)电势漂移,提高线性预测模型重复性,校正后ISE响应斜率漂移范围不超过0.4 mV/decade,截距漂移范围可控制在1 mV以内.SBC校正算法可提高Nernst线性模型预测精度,NO3-N、K+、Ca2含量预测平均相对误差分别从校正前的43.31％、38.46％、93.83％降至校正后的5.99％、7.44％、27.96％.校正后ISE可实现番茄营养液在线连续监测,反映营养液中目标离子含量变化.番茄花期养分吸收较活跃,NO3-N、K+、Ca2含量分别下降45.19％、36.46％和27.92％.%Monitoring macronutrients in hydroponic nutrient solution is a vital task for tomato growth.Ionselective electrodes (ISEs) were used to detect the NO3-N,K+,Ca2+ concentrations.The slope and bias correction (SBC) method was applied to alleviate the signal drift of ISEs due to continuous immersion in nutrient solutions.The slopes of response Nernst equation for NO3-,K +,Ca2+ ISEs were decreased to 0.05,0.39 and 0.04,and intercept potentials were reduced to 0.12 mV,0.93 mV and 0.10 mV,respectively.It indicted the capacity of slope and bias correction method as improving the repeatability and consistency of each ISE's Nernst equation.Then the NO3-N,K+ and Ca2+ concentrations were predicted by Nernst model,and they were measured by spectrographic method to provide standard values.The predicted accuracy of NO3-N,K +,Ca2 + concentrations was improved after using slope and bias correction method,providing by the relative errors were significantly reduced from 43.31％,38.46％ and 93.83％ to 5.99％,7.44％ and 27.96％,respectively.It was obvious that the results obtained from ISEs coupled with slope and bias correction method could indeed reflect the macronutrients component in tomato nutrient solutions.The assimilation of macronutrients was activated in flower stage,with the decrease of 45.19％,36.46％ and 27.92％ for NO3-N,K+ and Ca2+ concentrations,respectively.