Development And Optimization Of Total Phosphorus And Total Nitrogen Measuring Instrument

Total phosphorus and total nitrogen are important indicators to measure the quality of marine ecological environment,if the concentration of total phosphorus and total nitrogen in sea water is too high,it will cause ecological problems such as eutrophication of water body and so on,therefore,accurate determination of total phosphorus and total nitrogen concentration is of great significance for early warning of seawater eutrophication and protection of the marine ecological environment.National standard test methods for total phosphorus and total nitrogen in seawater are tedious and time-consuming,can not meet the requirements of continuous online monitoring of total phosphorus and total nitrogen in seawater.Therefore,developing an automatic measuring instrument which can achieve online and rapid detection of total nitrogen and total phosphorus in seawater is of great significance to improve the level of water quality monitoring in China.The research used microwave-persulfacte digestion technique combined with sequential injection valve laboratory technology to determinate the concentration of total phosphorus and total nitrogen in water sample,and the digestion conditions,the total phosphorus chromogenic conditions,the total nitrogen reduction and chromogenic conditions color were optimized.The experiments of interfering ions and salinity interfering indicated that,the main component ions and salinity in seawater affected the determination of this method,and could use standard solution of corresponding salinity to eliminate the interference.Under the optimum digestion and determination conditions,total phosphorus and total nitrogen all had good linear in the range of 0⁵ mg·L^-1,the linear correlation coefficient were all 0.999,the precision of total phosphorus was 2.47%,the precision of total nitrogen was 2.39%,the detection limit of total phosphorus was 0.0050 mg·L^-1,the detection limit of total nitrogen was 0.0066 mg·L^-1,total phosphorus recovery rate was greater than 94%,total nitrogen recovery rate was greater than 96%,they all meeted the requirements of the determination of total phosphorus and total nitrogen.Basing on the earlier experimental data,the design of total phosphorus and total nitrogen automatic measuring device was completed.Put forward the system structure of the device,each parts of the hardware,the system flow of the device and the overall appearance design of the instrument,laid the foundation for the development of measuring instrument of total phosphorus and total nitrogen.