pH-metric method determining the solubility and solubility products of slightly soluble salts of arbitrary composition

The developed method of determining KS from pH metric data has a number of advantages compared to those used traditionally. First, in place of the residual concentrations of the salt components, only the pH value of the saturated solution is used in the derived expressions. Thus, the number of independent variables, which need to be measured experimentally, is reduced. Furthermore, the potentiometric method, used to determine the pH, is sufficiently accurate, simple and universal and does not necessitate the use of ion-selective electrodes. At the same time, the residual concentrations are usually measured by chemical methods, which are inferior in most cases, for several reasons, compared to the potentiometric method. Second, the KS value calculated by the developed method has a thermodynamic character. The organization of the experiment must be appropriate to the applied equations. Therefore, it is necessary to draw attention to the need for high accuracy in the process of preparing the initial solutions, because the initial concentrations of the precipitate components are included in the calculation formulas. The developed method for determining Ks can be applied for systems of any degree of complexity, which contain additional complexing agents.

Potentiometric determination of organic acids in the medicinal plant raw material

Aim. To analyze the results of the quantitative content of the amount of organic acids in rhizomes with roots of Rumex confertus, rhizomes with roots of Sanguisorba officinalis, roots of Rosa majalis and roots of Rosa canina, roots of Arctium minus and roots of Arctium tomentosum, herb of Bidens tripartite by the potentiometric method, which is available in the monograph “Hibiscus” in the SPhU 2.0. Materials and methods. The study subjects were batches of rhizomes with roots of Rumex confertus, rhizomes with roots of Sanguisorba officinalis, roots of Rosa majalis and roots of Rosa canina, roots of Arctium minus and roots of Arctium tomentosum, herb of Bidens tripartite. The quantitative content of the amount of organic acids was determined by the potentiometric method from the monograph “Hibiscus” SPhU 2.0 using a HI 2550 potentiometer of the “HANNA instruments” company (Germany). Results and discussion. The highest content of the amount of organic acids, among the study subjects was in roots of Arctium minus (from 1.02 ± 0.04 % to 1.05 ± 0.04 %). At the same time, in roots of Arctium tomentosum this amount was almost 3 times lower (from 0.36 ± 0.01 % to 0.37 ± 0.01 %). In the batches of roots of Rosa majalis the content of this group of compounds was almost 2 times higher than in roots of Rosa canina. In rhizomes with roots of Rumex confertus and rhizomes with roots of Sanguisorba officinalis the content of the amount of organic acids differed insignificantly. In herb of Bidens tripartite the content of this group of compounds was 0.78 ± 0.03 – 0.79 ± 0.03 %. In different batches of one type of the raw material the quantitative content of the amount of organic acids varied slightly. Conclusions. For the first time, the quantitative content of the amount of organic acids has been determined in the batches of rhizomes with roots of Rumex confertus, rhizomes with roots of Sanguisorba officinalis, roots of Rosa majalis and roots of Rosa canina, roots of Arctium minus and roots of Arctium tomentosum, herb of Bidens tripartite using the potentiometric method which is available in the monograph “Hibiscus” in the SPhU 2.0. It has been found that the highest content of the amount of organic acids is observed in roots of Arctium minus (not less than 1.02 %) and herb of Bidens tripartite (not less than 0.78 %). The results obtained will be used in further research when creating new herbal medicines with the anti-inflammatory and antimicrobial activity.

Novel potentiometric sensors for determination of ondansetron hydrochloride in pure and dosage form

A new and sensitive potentiometric method has been developed and characterized for four novel sensors responsive to ondansetron hydrochloride.

Inexpensive ion-selective electrodes for the simultaneous monitoring of potassium and nitrate concentrations in nutrient solutions

A fast, simple and inexpensive potentiometric method has been developed for the determination of the major ions potassium and nitrate in nutrient solutions, by means of ion-selective electrodes (ISEs) based...

Study of the Complex Formation Process in the Iron (III)-1-Phenyl-2,3-Dimethylpyrazolin-5-Thion-6 mol/l HCl + Acetone System by the Potentiometric Method

The complex formation of iron (III) ions in a wide range of temperatures in a mixed solvent was studied by the potentiometric method using a redox electrode based on 1-phenyl-2,3-dimethylpyrazoline-5-thione and its oxidized form. The study shows that titration of the iron (III)--1-phenyl-2,3-dimethylpyrazoline-5-thione--6 mol/l HCl (HCl + acetone, ratio 1:3) system at a temperature of 273--318 K results in a regular increase in the potential indicator electrode. It was found that in the system under consideration four complex forms of compositions are formed: [FeL(H2O)5]3+, [FeL2(H2O)4]3+, [FeL3(H2O)3]3+ and [FeL4(H2O)2]3+. For each complex particle, their stability constants are determined by the Bjerrum method. Summarizing the experimental and theoretical data, it was established that the iron (III) complexes obtained in the 6 mol/l HCl medium are more stable than the complexes obtained in a mixed solvent with 1-phenyl-2,3-dimethylpyrazoline-5-thione. The values ΔH and ΔG of reactions of the formation of 1-phenyl-2,3-dimethylpyrazoline-5-thione complexes were found by Clark --- Glu method using the regression method. The corresponding patterns in the change in values ΔH, ΔG and ΔS of formation of complexes were revealed. To determine the region of dominance and the maximum yield of a particular complex particle, depending on the concentration of the organic ligand in the solution, distribution diagrams were constructed, according to which the maximum yield of a complex particle and the region of its dominance can be found at any point The work was carried out in accordance with the research plan of the laboratory "Synthesis and testing of coordination compounds" named after Corresponding Member of Tajik Academy of Sciences, Dr. Sc. (Chem.), Professor A.A. Aminjanov, Research Institute of the Tajik National University (project no. 0119TJ01007)