Study On The Method Of Rapid Field Detection Of Nitrogen Nutrients In Clean Water

The traditional spectrophotometric method for the detection of ammonia nitrogen and nitrate nitrogen needs to be carried out in the laboratory,which has the advantages of high sensitivity,low detection limit and good accuracy.However,it is difficult to achieve field detection and the timeliness of detection results is poor due to the time-consuming,complicated operation,high requirements for hardware equipment and the need to prepare multiple reagents.In this study,a hand-held multi-parameter detection colorimetric device was used for the rapid detection of nitrogen factors in water,and a fast detection method for ammonia nitrogen by improved salicylic acid method and nitrate nitrogen by chromic acid method was established.In this paper,the reagent ratio of the two methods were optimized,and the ammonia nitrogen mixed chromogenic agent M and nitrate nitrogen mixed chromogenic agent N were developed to realize the rapid field detection of nitrogen nutrients(ammonia nitrogen and nitrate nitrogen)in water,which can significantly improve the detection efficiency.The main research contents are as follows:(1)Study on rapid field detection method of ammonia nitrogen: The ratio of mixed chromotropic agent M was determined by orthogonal experiment,and it could be stored for 28 days under dark conditions.The optimal test conditions were determined as red light source of 710 nm,reaction time and temperature of the system were 15 minutes and 35℃,respectively,and the amount of chromogenic agent was0.5 g.The method was evaluated by linear test,precision,detection limit and spiked recovery rate.The results showed that the mass concentration of ammonia nitrogen in this method had good linearity with the absorbance in the range of 0～2 mg/L,and the linear correlation coefficients of the regression equations of three parallel measurements were all greater than 0.9990,which met the linear test requirements of the method verification.The detection limit was 0.0044 mg/L,indicating high sensitivity of the instrument.The relative standard deviation was between 1.6% and6.6%,indicating good precision of the method.The spiked recovery was between98.0% and 100%,indicating high accuracy of the method.Bland-altman method was used to analyze the actual water sample detection results of this method and the national standard method.The results showed that more than 95% of the points fall within the consistency limit,indicating that the two methods had high consistency and could be used interchangeable.Compared with the national standard salicylate photometric method,this method shortens the reaction time,improves the analysis efficiency,has the advantages of simple operation,low analysis cost,and it is feasible.(2)Study on rapid field detection method of nitrate nitrogen: The optimum ratio of mixed chromogenic agent N was determined by single factor experiment,and it could be stored for 28 days under dark conditions.The optimal test conditions were determined as follows: the detection light source was 420 nm violet light,the reaction time was 15 minutes,the amount of chromogenic agent was 0.05 g,and the amount of 70% sulfuric acid was 7.0 m L.The results showed that the mass concentration of nitrate nitrogen in this method had good linearity with the absorbance in the range of0～25 mg/L,and the linear correlation coefficients of the regression equations of three parallel measurements were all greater than 0.9990,which met the linear test requirements of the method verification.The detection limit was 0.05 mg/L,indicating high sensitivity of the instrument.The relative standard deviation was between 1.5% and 3.1%,indicating good precision of the method.The spiked recovery was between 98.9% and 104%,indicating high accuracy of the method.Bland-altman method was used to analyze the actual water sample detection results of this method and the national standard method.The results showed that more than95% of the points fall within the consistency limit,indicating that the two methods had high consistency and could be used interchangeable.Compared with the national standard thymol spectrophotometry,the national standard method requires the use of spectrophotometer,preparation of a variety of reagents.Reagents are liquid reagents,not easy to save,and sample concentration values need to be plotted and calculated.The rapid field detection method in this study is solid powder,which is convenient for transportation and storage,and has few operation steps and low technical requirements.Therefore,it has a good application prospect in the field of environmental monitoring.