Study On The Determination Technology Of Phosphate In Water

Phosphate in water is a necessary substance for biological growth,which has an important impact on the ecosystem.In recent years,eutrophication has become more and more serious due to a large number of domestic sewage,industrial waste discharge and aquaculture pollution,phosphate is becoming a major pollutant in coastal waters.Therefore,phosphate in water is a necessary item for ecological environment monitoring.Phosphate in water quality is an important nutrient element in water environment.The accurate determination of phosphate in water quality is of great significance to the further study of marine productivity and material circulation.As a result of physical and chemical processes,especially the consumption and transformation of nutrients(mainly inorganic nutrients)by biological activities,the concentration of major nutrients in untreated water samples changed rapidly after collection.For these active substances,it has become an urgent problem to select suitable storage methods so that their concentrations and chemical forms can be stored for a long time.The results of the ―sample preserved material‖ experiment showed that phosphate in water was more likely to be preserved in plastic bottles.However,the composition of seawater is very complex,and different parameters may affect the concentration of active phosphate in different directions and degrees.During the discussion of single variable control,samples with low bioactivity may be more suitable for preservation.The preservation and pretreatment techniques of seawater samples are directly related to the accuracy of the analytical results.In this paper,the container,preservation reagent and preservation time which affect the preservation period of water samples in the process of phosphate determination in water are studied and analyzed.At the same time,the uncertainty of determination of phosphate by flow analysis method was discussed.An experimental was studied to explore an effective,convenient and practical preservation method to improve the accuracy of active phosphate detection.Through the statistics of the experimental results to explore the comparability of two different determination methods of phosphate in water,as well as the comparability of phosphate determination methods in surface water,estuarine water,and seawater,promote the popularization and application of automatic analysis technology.The effects of salinity,concentration and biological activity on the determination and preservation of active phosphate were investigated by means of controlled variables.At the same time,the whole process of phosphate determination shall be controlled to ensure the quality,including the process of sampling vessel,method and operation process.To control the quality of the sample preservation and transportation process;Controlling the preservation condition and method of the sample;Identify the matters needing attention in the sample detection process.Ensure that the sample detection results are true,effective,controllable and traceable,and apply the experimental results to the actual monitoring work,with verify the standard curve,testing the standard solution and testing the parallel samples.In this paper,the effective storage time of seawater samples was studied by experiments at – 20℃.And the influence of some physical and chemical parameters of seawater on the storage time of samples.The results showed that the concentration of active phosphate changed with time in 35 days.The data analyzed by the instrument showed that the concentration of the sample increased at the beginning of storage and began to decrease at the 8th day,so that the concentration dropped to a lower level at the 15 th day and was close to the initial concentration.From then on until the 35 th day,the sample concentration changed little;there are some minor differences between manual analysis data and instrument data.In general,the concentration of manual analysis data has been in an increasing state,but the degree of increase is not obvious,and the sample state is stable within 3 to 18 days of storage.The freezing storage time before sample treatment has a certain influence on the concentration of different samples,when the storage time is analyzed by using the processing time as the starting point of the sample storage time,the variation of the sample concentration with time is different.Due to the complex composition of seawater,different parameters may affect the concentration of active phosphate in different directions and degrees.During the discussion of controlling a single variable,there is no obvious influence of a single parameter in the selected sample range.In order to verify the feasibility and reliability of the conclusions in practical application,a method verification experiment was carried out in August 2017.Select plastic bottles to store the samples for 30 days under the freezing condition of-20 ℃.The samples were analyzed by national standard method as control group data.Parallel samples were analyzed by flow analysis method as experimental group.,It was found that there was no significant difference between the two methods through t-test,and the relative deviation of the data involved in the experiment was within the allowable limit.It was proved that the difference between parallel samples was small,and the above preservation method could better ensure the relative stability of the sample concentration in the preservation process.In this paper,the linear regression equation y = bx + a is obtained by the signal response of a group of six independent parallel samples with specific concentration gradient.the propagation coefficients of y,a,b and the standard deviation are calculated by establishing a mathematical model to determine the uncertainty of the flow injection analyzer.In this experiment,the uncertainty in the determination of active phosphate in water by flow injection analysis was evaluated by introducing three uncertainty components: input quantity(y),input quantity(b)and input quantity(a).The input(y)should consider the process of fitting the standard curve,the process of preparing the standard solution,the non-repeatability of solution measurement of unknown concentration,and the display error of instrument readings.System errors such as environment,operation,etc.are characterized by the repeatability of a set of 12 parallel data.The results show that the input(b)has the largest component proportion of uncertainty,which indicates that human factors and environmental factors influence the experimental analysis to a certain extent in the process of standard curve configuration;secondly,the uncertainty component introduced by the input(y)shows that the experimental results are restricted by the accuracy of instruments,instruments and standard materials.The input quantity(a)representing the linear fit introduces the least uncertainty component.