Research And Development On The Phosphate Ion-selective Electrode

Phosphorus is an indispensable element for animal and plant life, but excessive phosphorus discharged into rivers and lakes will lead to water pollution. Among the methods of phosphate detection, most of them need to add some chemical reagents, and this will cause secondary pollution to the environment. Compared with other methods, the ion-selective electrode has advantages of simple and rapid analysis, high sensitivity, and low cost, and the most important advantage is no added chemical reagent in the process of detectiont. Therefore, ion-selective electrodes are chosen to develop phosphate ion sensor based on the Nernst in this paper. The main contents are listed as follows:(1)In order to detect the concentration of phosphate in water, a kind of solid-state film phosphate ion which is based on glassy carbon electrode as basal electrode has been developed. Co SO4 and Na2SO4 are polymerized under certain conditions by Cyclic Voltammetry method. Based on the orthogonal experiments, the best preparation condition of electrode can be obtained. Many performance indexes of the electrode can be obtained by using direct potentiometric determination. The electrode has a slope of-41.7m V/decade and a detection limit of 6.3 × 10-5mol / L and the linear potential response in the concentration range of 10-1 to 10-4mol/L. The electrode has a shorter response time and good stability. For the electrode with cobalt as the base, the problem of measurement needs to be oxidized has been solved. The method has certain significance for the detection of phosphate.(2)In order to improve the service life of the solid phosphate ion selective electrode membrane and the electrode substrate in detection, a phosphate ion selective electrode, which used glassy carbon electrode as substrate, was developed for determination of phosphate concentration in water based on phase transfer catalyst. The characteristics of the electrode were evaluated by using direct potentiometric determination. The electrode exhibited linear potential response in the concentration range of 10-1 to 10-5mol/L and a low detection limit of 3.36 × 10-6mol / L. It also had a shorter response time and good stability.(3)In order to solve the damage of solid electrode membrane and electrode base in detection, a liquid phosphate ion selective electrode is sdudied. The composition of membrane is 0.43 g PVC, 0.03 g TDMAC, 5ml o-NPOE dissolved in 10 ml Tetrahydrofuran. The electrode has a slope of-32.8m V/decade, the linear potential response in the concentration range of 10-1 to 10-4mol/L and long using time. The method has certain significance for the detection of phosphate.(4)In order to aviod the detection added chemical reagents and the secondary pollution to the environment, according to the distribution coefficient and Nernst equation,a math model of the relationship between the response potential and the p H value of the solution and ion concentration is established so as to improve the accuracy of the electrode. It has successfully solved the need to add a buffer solution. It has certain significance for the possibility of on-line real-time monitoring of phosphate.