Improvement of Potentiometric Determination of Ammonium Ions in Surface Waters for the Samples with a High Concentration
The problem of choosing a technique for determining ammonium ions, in concentrations above 1 gm/cdm, in surface waters, as in complex matrix, is one of the important problems of monitoring the condition of water bodies contaminated with ammonium salts. The solution to this problem will allow us to reliably assess the ecological condition of water bodies and the degree of reduction of environmental load during pollution elimination measures. Potentiometric methods have high accuracy and sensitivity, they are economical and make it possible to determine the analyte in turbid and colored matrices. Accordingly, potentiometric methods of analysis can be used to determine ammonium ions in surface waters because of their obvious advantages. But, conventional potentiometric determination techniques have several disadvantages. For example, great time consumption and low reproducibility due to preliminary distillation. In addition, high concentrations of ammonium ions and the complexity of the surface water composition lead to problems with the use of the calibration graph method, since in the process of determination it is necessary to apply multiple dilution, which results in an error in the determination. Accordingly, the possibility of using the additive method in conjunction with dilution was investigated. The article presents the main results of a validation study of an improved method for the quantitative determination of ammonium ion concentrations in the range from 2.0 gm/cdm to 9.0 gm/cdm with the help of the potentiometric method using the additive method in conjunction with dilution. The values of indicators of repeatability, reproducibility and accuracy of the method were established and turned out to be 6, 10 and 26%, respectively. The insignificant difference in the accuracy of the results obtained using the improved method and the prototype method was established.
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