| High content of ammonia nitrogen will lead to the occurrence of water eutrophication and aquatic organisms have a certain degree of toxic effects,so the process of aquaculture ammonia nitrogen content has been measured as one of the important parameters of the water suitable for aquaculture.At present,the widely used Nessler's reagent spectrophotometry and ammonia gas sensing method in the detection of ammonia nitrogen still have some shortcomings that can not meet the needs of the actual aquaculture process.Because of its high selectivity,low detection limit,convenient detection and easy destruction,solid-state ion selective electrode has wide application prospect in the field of aquaculture.In this thesis,the performance of ammonium ion selective electrode based on polyaniline modified many kinds of conductive matrix materials for detecting ammonium ion content in water was studied,and the copolymer with polyaniline and graphene was used as the solid state contact layer to prepare more excellent performance Solid-state ammonium ion selective electrode,a series of studies on its related performance parameters were carried out.Finally,a composite electrode with solid-state reference electrode and solid-state ammonium ion-selective electrode was prepared and its performance was studied.Specific work as follows:Polyaniline was deposited on a copper wire and silver filament conductive substrate by potentiostatic method and a solid-state ammonium ion selective electrode was successfully prepared by the Czochralski method.Electrodes with titanium dioxide(TiO2)semiconductors as conductive substrates are not capable of detecting ammonium ions in water because the conductivity of semiconductors is still not sufficient to meet the needs of solid-state ion selective electrodes.The detection range of the solid-state ammonium ion selective electrode with polyaniline solid state contact layer is 10-5 mol/L to 10-2 mol/L,the sensitivity is 20.68 mV/Dec and the correlation coefficient is 0.996 The detection range of the solid-state ammonium ion selective electrode with polyaniline as the solid-state contact layer was 10-4 mol/L to 10-1 mol/L and the sensitivity was 75.10 mV/Dec.The correlation coefficient was 0.998.Porous copper increases the surface area ratio of the base electrode to a certain extent compared with that of copper wire and also increases conductivity.Porous copper as the conductive matrix material,polyaniline solid-state contact layer solid ammonium ion selective electrode detection ranges of 10-5 mol/L to 10-1 mol/L,the sensitivity of 42.50 mV/Dec,the correlation coefficient of 0.998.The reduced graphene oxide,polyaniline and reduced graphene oxide copolymer were deposited on the porous copper conductive substrate by potentiostatic method and cyclic voltammetry respectively.The detection range of the solid-state ammonium ion selective electrode with porous copper as the conductive matrix material and the graphene solid-state contact layer is 10-6 mol/L to 10-1 mol/L,the sensitivity is 44.80 mV/Dec and the correlation coefficient is 0.999.The detection range of the solid-state ammonium ion-selective electrode with polyaniline and reduced graphite oxide copolymer as the solid-state contact layer was 10-6 mol/L to 10-1 mol/L and the sensitivity was 58.91 mV/Dec,the correlation coefficient is 0.999,Porous copper as the conductive matrix material,polyaniline and reduced graphite oxide copolymer thin film solid state contact layer solid ammonium ion selective electrode detection mechanism for two aspects,on the one hand polyaniline and reduced graphite oxide copolymer has very good Conductivity,and its unique three-dimensional structure to improve the electron transfer rate and shorten the electron in the solid state contact layer and the ion-selective membrane transmission distance;the other hand,it is the polyaniline with the redox capacitance and reduction of graphite oxide Dilatancy has the double-layer capacitance of the composite role.The electrode has a fast response time with good stability and only has a potential drift of 1.8 mV over a 100-hour test period.The selectivity coefficient of the electrode to interfering ions such as sodium,potassium,copper,calcium,magnesium and zinc is less than 10-2,indicating that the electrode has good anti-interference ability against other ions in water.The electrode has good resistance to natural light,but when the air is blown into the solution,the potential has changed a lot,basically stable at 200 mV.A water film is not formed on the surface of the electrode because the reduced graphene oxide is hydrophobic.The electrode can be successfully used for the detection of ammonia nitrogen in actual aquaculture water,which is only 5%compared with the detection result of Nessler's reagent spectrophotometry.Solid state reference electrode was successfully prepared on stainless steel tube by hot dipping method and electrolytic chlorination method.The potential of the solid-state reference electrode prepared by hot dip coating was not stable during the detection.The potential changed by 9 mV during the detection time of 100 s,and the potential of the electrode changed with the passage of time.The potential difference between Ag/AgCl electrodes changes from about 100 mV to about 25 mV.The solid reference electrode prepared by electrolytic chlorination method was relatively stable in the process of detection,and remained at about 185 mV.And the potential of the electrode drifted from 185 mV to 175 mV for only 6 days,only 10 mV.In 3 days the electrode potential drift is less than 5 mV,with relatively good value.Porous copper as the conductive matrix material,polyaniline and reduced graphite oxide copolymer thin solid state contact layer of solid-state ammonium ion selective electrode and electrolytic chlorination method of the solid-state reference electrode composite electrode in the detection process is very good Stability.The detection range of the composite electrode is still 10-6 mol/L to 10-1 mol/L,but the sensitivity is reduced from 58.91 mV/Dec to 23.43 mV/Dec.The composite electrode used in the actual aquaculture water ammonia concentration test,the error of about 15%. |
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