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The combined method based on phase-solubility technique and capillary zone electrophoresis (PS-CZE) was suggested for the determination of binding (stability) constants of cyclodextrins (CD) complexes with water-insoluble organic compounds that have no or weak UV chromophores. In this method, the insoluble compounds are agitated at the desired temperature in CD solutions with different concentration up to the attainment of equilibrium and then CZE is used to determine the concentration of the compounds that have passed into the solutions. To avoid precipitation and complex dissociation, the background electrolyte (BGE) for CZE should contain ethanol and, if necessary, cyclodextrin. The samples should be diluted with the BGE without CD so that the CD concentrations in BGE and samples were equal to preclude a baseline shift. Using the suggested approach, the inclusion complexes between betulinic and betulonic acids, pentacyclic lupane-type triterpenes, and hydroxypropyl-β- and γ-cyclodextrins (HP-β-CD and HP-γ-CD) were studied. It was found that solubility of the acids studied in HP-β-CD solutions did not differ from their solubility in pure water. That is, the HP-β-CD complexes of the acids studied were not formed in noticeable amount. At the same time, the acids formed inclusion complexes with HP-γ-CD, what possibly was caused by the greater size of the HP-γ-CD molecule as compared to HP-β-CD. To determine binding constants by Higuchi and Connors method, the acids solubility was determined by CZE after their agitation in the solutions of HP-γ-CD (with 0.6 molar substitution) at 25 °C for 3 days. The dependences of acids solubility on HP-γ-CD concentration deviated from straight line in the range of high concentration (A mode). This can be explained by a self-association of HP-γ-CD molecules. Using the linear segment of the solubility dependences on CD concentration, the binding constants were determined. Their logarithms for the HP-γ-CD complexes with betulonic and betulinic acids were 3.88 ± 0.14 and 3.82 ± 0.12, respectively.

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In this work, the electrooxidation as environmentally clean technology has been studied to the degradation of Mordant Blue 13 azo dye (MB13) using boron-doped diamond (p-Si/BDD) and oxide ruthenium titanium (Ti/RuTiO (DSA)) anodes in various water matrices: distilled water (DW), hot tap water (HTW), and simulated wastewaters with (SWS) and without surfactant (SW). The influence of experimental parameters, such as current density, initial dye concentration, electrolysis time/specific charge, and pH on the MB13 degradation rate, current efficiency, and energy consumption, has been determined. The enhanced rate of both color and chemical oxygen demand (COD) removal in sulfate aqueous solutions with BDD was observed, which indicates that sulfate (SO) radicals along with OH ones might be responsible for the degradation process. The MB13 decolorization process obeyed a pseudo-first-order reaction kinetics with the apparent rate constant from 7.36 × 10 min to 4.39 × 10 min for BDD and from 9.2 × 10 min to 2.11 × 10 min for DSA depending on the electrolysis conditions. The effect of water matrix on the decolorization and COD removal efficiency has been evaluated. Inorganic ions, mordant salt, and surfactant contained in simulated effluents decelerated the COD decay compared to DW and HTW for the both anodes; meanwhile, they differently affected the discoloration process. A comparison of the specific energy consumption for each electrocatalytic material under different experiment conditions has been made. The BDD electrode was more efficient than the DSA to oxidize the MB13 dye in all kinds of water.

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