Application Of Solid-contact Ammonia Nitrogen Sensor In Environmental Monitoring

The ammonia nitrogen(TAN)pollution is an important part of the water pollution.Excessive TAN in water will cause serious toxic effects to the aquatic animals and plants and thus destroy the balance of aquatic ecosystem.In this thesis,we developed a solid-contact ammonia nitrogen sensor based on the ion-selective electrode(ISE).The conventional liquid membrane electrode and the internal solution were replaced by an all-solid-state ammonium-sensitive electrode and the hydrogel of polyvinyl alcohol(PVA)for the first time,which could greatly improved the sensitivity of the solid-contact ammonia nitrogen sensor and can be used for the monitoring of TAN in the environment.The detail works of this thesis are as follows:1.Construction of the solid-contact ammonia nitrogen sensor based on the NH4+-ISE: It was composed of the hydrophobic conductive polymer,polymeric ion-sensitive membrane,polyvinyl alcohol hydrogel,reference electrode and the hydrophobic gas-permeable membrane.Nonactin was used as the ionophore to prepare the all-solid-state NH4+-ISE.The use of PVA hydrogel instead of conventional internal solution placed above the ammonium-selective electrode greatly improved the stability of the sensor.A hydrophobic gas-permeable membrane was covered on the top of the hydrogel layer to eliminate the interferences of ions in the solutions.Through the optimization of the factors such as the concentration and volume of the PVA hydrogel,the types of gas-permeable membranes and temperature,we realize the construction of the solid-contact ammonia nitrogen sensor.2.The application of the solid-contact ammonia nitrogen sensor in the monitoring of the TAN in seawater: Through the study of the complex environment in seawater and the analysis of simulated seawater samples,the detection TAN in seawater was realized by the proposed ammonia nitrogen sensor using the standard addition method,which successfully achieve the application of the solid-contact ammonia nitrogen sensor in environmental monitoring.3.The preliminary construction of the solid-contact ammonia nitrogen sensor based on the H+-ISE: On the basis of the above ammonia nitrogen sensor,we developed a new type of all-solid-state H+-ISE by altering the composition of the polymeric membrane cocktail.The proposed all-solid-state H+-ISE achieves a linear response over the pH range 4.5-10.5 and exhibits a quick response to the change of the concentration of H+,which realizes the preliminary construction of the new type of the solid-contact ammonia nitrogen sensor.A new type of ammonia nitrogen sensor will be established by further research,which can achieve the detection of TAN by measuring the change of pH.