Известия Томского политехнического университета: Инжиниринг георесурсов (May 2019)
Complexometric differential determination of copper (II) and zinc (II) using mathematical model of the titration process
Abstract
Relevance of the research is caused by the necessity to improve the method of potentiometric analysis of multicomponent mixtures. The main aim of the study consists in development of the method for complexometric-differentiated determination of copper (II) and zinc ions (II) from a single solution by potentiometric titration with computer processing of the titration method results by fragmentary linearization. The methods used in the study: titration with visual indication of the equivalence point, potentiometry, computer processing the results of the titration method fragmented linearization. For separate determination of metals, which give the close strength complexonates, the authors have proposed the method of potentiometric titration with variation of the medium acidity at titration. The data of potentiometric titration were processed by linearization. The method is based on construction of mathematical model of the logarithmic titration curve, which is converted by the change of variables into linear regression response. The result. The authors studied the conditions of the differentiated complexometric titration of copper (II) and ions zinc (II) using Pb-selective electrode (ISE-Pb) as the indicator one. Potentiometric determination of the mixture of copper (II) and zinc ions (II), which give the close strength complexonates, was carried out by varying the medium acidity at titration. In more acidic medium (acetate buffer) the authors defined copper ions and in alkaline medium (ammonium buffer) they fixed the second titration discontinuity corresponding to the total content of copper and zinc ions. The proposed method for the separate determination of copper (II) and zinc ions (II) under their mixture was tested on the titration data of the model binary mixtures and on real object. Conclusions. The authors proposed the simple method of the differentiated potentiometric determination of Cu (II) and Zn (II) ions at joint presence using ISE-Pb as the indicator electrode. The value of the relative standard deviation of the examined ions in the model binary mixtures is within the range from 0,006 to 0,2 at content of each component of the mixture from 1 to 25 mg in 50 ml of the examined solution. The advantage of the method proposed is in simultaneous determination of one aliquot part of the solution of two components of the mixture without their preliminary separation by the titration data. The results of latten Ls-59-1potentiometric analysis for the content of basic components by the proposed methods did not show statistically significant differences with the data obtained according to the standard techniques. The application of linearization for processing the curves of potentiometric titration increases selectivity of titrimetric determinations by varying the medium acidity at titration. This extends the possibilities of potentiometric determination of multi-component systems.
