Development And Performance Comparison Of Novel All Solid Ammonium Ion Selective Electrodes Based On O-phenylenediamine And 18-crown-6

The ocean is a natural treasure trove of resources,which is an important boost to economic development.However,marine pollution is becoming more and more serious during the development of the oceans.Excessive NH4+ and other nutrients cause red tide and algal bloom,which can cause great toxicity to marine organisms and aquatic organisms in rivers and lakes.Therefore,it is necessary to develop an ammonium ion-selective electrode for rapid and accurate determination of ammonium ion,which can be used as a significant technical means for monitoring NH4+ content.In this paper,two novel all-solid ammonium ion selective electrodes with silver/nano-silver as the substrate,polyaniline as the conductive layer,poly-o-phenylenediamine and 18-crown-6 as sensitive membrane were developed,respectively.The electrode preparation,response principle,characterization such as CV,EIS,SEM,performances test including slope,response range,detection limit,selectivity,reproducibility,stability and lifespan and application are discussed.Ammonium ion selective electrode based on o-phenylenediamine was with silver/nano-silver as the substrate,polyaniline as the conductive layer,poly-o-phenylenediamine as the sensitive film.Nano-silver was obtained by electrodeposition in 0.1 mol/L silver nitrate standard solution at potential of 500 mV and frequency of 50 Hz sine half-wave.The polyaniline and poly(o-phenylenediamine)through cyclic voltammetry at 0.1 mol/L hydrochloric acid and 0.08 M hydrochloric acid-o-phenylenediamine solution scanned at 3 circles and 4 circles,respectively.The electrodes were with the slope of 54.99-55.70 mV/decade,the response range of 10-1-2×10-5 mol/L and the detection limit of 1.2×10-5 mol/L.Meanwhile its response time was short about 0.5-2 s,the impedance about 70 ? and lifespan up to 147 days.It can be seen from the SEM spectrum that the films are dense,homogeneous and closely connected,and the poly(o-phenylenediamine)films are in the form of Flaky structure with size of 0.5-5 ?m.The membrane of 18-crown-6-based ammonium ion selective electrode was prepared by scanning at 4 circles with potential of 0.3 V in hydrochloric acid-18-crown-6 solution,which was irregular spherical at the diameter of 0.1-0.3 ?m under scanning electron microscope.The slope was closer to the theoretical slope than the ammonium ion-selective electrode based on o-phenylenediamine,which was 55.36-55.64 mV/decade.The response range of the electrode was 10-1-10-4 mol/L,with the detection limit of 4.3×10-5 mol/L and the response time of 0.5-3 s.The impedance of the electrode was about 100 ? and the life of 68 days,and it has a good selectivity for the ammonium ion.The slope of ammonium ion selective electrode based on the 18-crown-6 is slightly larger than that of the o-phenylenediamine-based ammonium ion selective electrode,but it is slightly inferior to the latter in terms of lifetime,selectivity,and response time.In this study,the preparation of all solid state ammonium ion selective electrodes is simple with small size.It is easy to carry and easy to integrate with other sensors,which can realize multi parameter measurement.The life of 147 days and good stability are expected to be widely used in the fields of long time monitoring for NH4+,such as coastal waters,rivers,lakes and so on.In addition,the electrode response time is short and the impedance is small,which can provide more accurate measurement results.