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针对国家环境保护标准(HJ537—2009)中规定氨氮测定的蒸馏-中和滴定法所使用的滴定终点判定方法-混合指示剂法存在变色不敏锐、人眼辨色能力差及难以实现滴定终点自动判定等问题,研究提出一种操作简单、灵敏度高的电位滴定法,以替代传统的指示剂法,提高滴定终点判定的准确性。同时,基于反馈控制和专家控制的基本原理,设计了几种快速滴定的自动控制策略,并对滴定系统进行计算机仿真。结果表明,专家-PID控制策略能使自动电位滴定系统的最大误差小于0.0064 mg/L,滴定时间小于66 s,能实现滴定终点的自动、快速和精准判定。
End-point determination method for distillation-neutralization titration method for ammonia-nitrogen determination specified in National Environmental Protection Standard (HJ537-2009) - Mixed indicator method is not sensitive to discoloration, poorly discriminating human eyes and difficult to achieve titration end point automatic And other issues, the study proposed a simple, high sensitivity potentiometric titration method to replace the traditional indicator method to improve the accuracy of determination of the end point of titration. At the same time, based on the basic principle of feedback control and expert control, several rapid titration automatic control strategies were designed and the titration system was simulated by computer. The results show that the expert-PID control strategy can make the maximum error of the automatic potentiometric titration system less than 0.0064 mg / L and the titration time less than 66 s, which can achieve automatic, rapid and accurate determination of titration end point.