A Novel Ion Selective Potentiometric Sensor Based On Cotton Thread

As we all know,heavy metal ions are harmful to our environment,animals and plants.Therefore,the detection and recognition of heavy metal ions is of great significance.Ion-selective electrode is a kind of electrochemical sensor which can detect the activity or concentration of the substance to be measured in the solution through the membrane potential.The relationship between the potential difference formed by the electrode and the content of the substance to be measured conforms to the Nernst equation.This paper is devoted to the effective and cheap solid-state ion selective electrode preparation and research and development,as a carrier for electrode using cotton in cotton thread coated on the surface of the conductive layer,ion selective layer,insulation,sealing,by using different ion selective carrier,the preparation of a series of effective potassium,sodium ion selective electrode and lead,mercury ion electrode.Compared with the traditional ion-selective electrode,the all-solid ion-selective electrode based on cotton thread has no internal electrolyte,the preparation process is more convenient,the electrode does not need special maintenance,and its stability and repeatability performed well as the traditional ion-selective electrode.At the same time,the all-solid ion selective electrode prepared by this method is cheap,easy to be miniaturized,and can meet the requirements of field detection in different environments.This topic mainly carries on the following two aspects of work:（1）Preparation of potassium and sodium ion selective electrodes.In this chapter,an all-solid ion-selective electrode preparation technology with simple process and high sensitivity was proposed to solve the shortcomings of the current ion-selective electrode preparation technology,such as complexity and expensiveness,and it was successfully applied to the detection of potassium and sodium ions in human urine.The commercial sodium ion selective carrier X and potassium ion selective carrier I were mixed with ion exchanger,polyvinyl chloride and 1-nitro-2-（n-octyloxy）benzen evenly and coated on the cotton thread substrate coated with conductive ink.The sodium ion and potassium ion selective electrode on the cotton thread substrate were prepared respectively.By measuring the potential of these electrodes in their ionic standard solution,it is found that they have a good Nernst response with slopes of 58.5 m V/decade（Na ion）and 59.0 m V/decade（K ion）,which are very close to the theoretical value of 59.2 m V/decade.At the same time,the ion response time of this kind of electrode is relatively fast to the traditional ones（less than 10seconds）,the electrode stability is performed well（less than 0.1m V/min in 5 minutes,less than 0.05m V/min in 30 minutes）,and it shows good reusability（no obvious change after 20times of recycling）.（2）Preparation of lead ion recognition electrode.Cotton thread base in the previous chapter solid-state ion selective electrode preparation methods,we designed and synthesized a series of tetrathiafulvalene（TTF）replaced by pyridine derivatives（C1～C4）,as the N atom in the pyridine ring has good interaction with most metals,so the molecules is expected to be used as ion selective carrier.By optimizing the ratio of ion-selective carrier to ion exchanger,we found that the all-solid ion-selective electrode using the TTF molecule substituted by such pyridine as the ion-selective carrier has a good recognition performance and exhibits a Nernst response to lead ions.The Nernst slopes of C3 and C4 as lead ion selective carriers are 29.01m V/decade and 28.96 m V/decade,respectively（close to the theoretical value of 29.6m V/decade）.The detection range is 1×10^-6 M to 1×10^-2 M.Therefore,using the pyridine substituted TTF molecule as the ion selective electrode has a good ability of lead ion recognition and detection.