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O.v. Antropova - One of the best experts on this subject based on the ideXlab platform.
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Solubility Diagram of (lithium sulfate + sodium sulfate + rubidium sulfate)(aq) at the temperature 298.15 K
The Journal of Chemical Thermodynamics, 1994Co-Authors: A. M. Kalinkin, S. K. Vasin, O.v. AntropovaAbstract:Abstract The phase-equilibrium Diagram of (lithium sulfate + sodium sulfate + rubidium sulfate)(aq) at T = 298.15 K has been calculated using Pitzer et al .'s equations. A new compound 5Li 2 SO 4 ·Na 2 SO 4 ·2Rb 2 SO 4 ·2H 2 O has been isolated. The results of the calculation have been confirmed by an experimental study of the Solubility. The molar Gibbs free energy of formation of the triple sulfate at T = 298.15 K according to the reaction: 5Li 2 SO 4 ·H 2 O(cr) + Na 2 SO 4 ·10H 2 O(cr) + 2Rb 2 SO 4 (cr) = 5Li 2 SO 4 ·Na 2 SO 4 · 2Rb 2 SO 4 ·2H 2 O(cr) + 13H 2 O(1) was found to be Δ c G o m = -(39.2 ± 0.5) kJ·mol -1 ( p o = 10 5 Pa).
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Solubility Diagram of lithium sulfate sodium sulfate rubidium sulfate aq at the temperature 298 15 k
The Journal of Chemical Thermodynamics, 1994Co-Authors: A. M. Kalinkin, S. K. Vasin, O.v. AntropovaAbstract:Abstract The phase-equilibrium Diagram of (lithium sulfate + sodium sulfate + rubidium sulfate)(aq) at T = 298.15 K has been calculated using Pitzer et al .'s equations. A new compound 5Li 2 SO 4 ·Na 2 SO 4 ·2Rb 2 SO 4 ·2H 2 O has been isolated. The results of the calculation have been confirmed by an experimental study of the Solubility. The molar Gibbs free energy of formation of the triple sulfate at T = 298.15 K according to the reaction: 5Li 2 SO 4 ·H 2 O(cr) + Na 2 SO 4 ·10H 2 O(cr) + 2Rb 2 SO 4 (cr) = 5Li 2 SO 4 ·Na 2 SO 4 · 2Rb 2 SO 4 ·2H 2 O(cr) + 13H 2 O(1) was found to be Δ c G o m = -(39.2 ± 0.5) kJ·mol -1 ( p o = 10 5 Pa).
A. M. Kalinkin - One of the best experts on this subject based on the ideXlab platform.
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Solubility Diagram of (lithium sulfate + sodium sulfate + rubidium sulfate)(aq) at the temperature 298.15 K
The Journal of Chemical Thermodynamics, 1994Co-Authors: A. M. Kalinkin, S. K. Vasin, O.v. AntropovaAbstract:Abstract The phase-equilibrium Diagram of (lithium sulfate + sodium sulfate + rubidium sulfate)(aq) at T = 298.15 K has been calculated using Pitzer et al .'s equations. A new compound 5Li 2 SO 4 ·Na 2 SO 4 ·2Rb 2 SO 4 ·2H 2 O has been isolated. The results of the calculation have been confirmed by an experimental study of the Solubility. The molar Gibbs free energy of formation of the triple sulfate at T = 298.15 K according to the reaction: 5Li 2 SO 4 ·H 2 O(cr) + Na 2 SO 4 ·10H 2 O(cr) + 2Rb 2 SO 4 (cr) = 5Li 2 SO 4 ·Na 2 SO 4 · 2Rb 2 SO 4 ·2H 2 O(cr) + 13H 2 O(1) was found to be Δ c G o m = -(39.2 ± 0.5) kJ·mol -1 ( p o = 10 5 Pa).
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Solubility Diagram of lithium sulfate sodium sulfate rubidium sulfate aq at the temperature 298 15 k
The Journal of Chemical Thermodynamics, 1994Co-Authors: A. M. Kalinkin, S. K. Vasin, O.v. AntropovaAbstract:Abstract The phase-equilibrium Diagram of (lithium sulfate + sodium sulfate + rubidium sulfate)(aq) at T = 298.15 K has been calculated using Pitzer et al .'s equations. A new compound 5Li 2 SO 4 ·Na 2 SO 4 ·2Rb 2 SO 4 ·2H 2 O has been isolated. The results of the calculation have been confirmed by an experimental study of the Solubility. The molar Gibbs free energy of formation of the triple sulfate at T = 298.15 K according to the reaction: 5Li 2 SO 4 ·H 2 O(cr) + Na 2 SO 4 ·10H 2 O(cr) + 2Rb 2 SO 4 (cr) = 5Li 2 SO 4 ·Na 2 SO 4 · 2Rb 2 SO 4 ·2H 2 O(cr) + 13H 2 O(1) was found to be Δ c G o m = -(39.2 ± 0.5) kJ·mol -1 ( p o = 10 5 Pa).
S. K. Vasin - One of the best experts on this subject based on the ideXlab platform.
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Solubility Diagram of (lithium sulfate + sodium sulfate + rubidium sulfate)(aq) at the temperature 298.15 K
The Journal of Chemical Thermodynamics, 1994Co-Authors: A. M. Kalinkin, S. K. Vasin, O.v. AntropovaAbstract:Abstract The phase-equilibrium Diagram of (lithium sulfate + sodium sulfate + rubidium sulfate)(aq) at T = 298.15 K has been calculated using Pitzer et al .'s equations. A new compound 5Li 2 SO 4 ·Na 2 SO 4 ·2Rb 2 SO 4 ·2H 2 O has been isolated. The results of the calculation have been confirmed by an experimental study of the Solubility. The molar Gibbs free energy of formation of the triple sulfate at T = 298.15 K according to the reaction: 5Li 2 SO 4 ·H 2 O(cr) + Na 2 SO 4 ·10H 2 O(cr) + 2Rb 2 SO 4 (cr) = 5Li 2 SO 4 ·Na 2 SO 4 · 2Rb 2 SO 4 ·2H 2 O(cr) + 13H 2 O(1) was found to be Δ c G o m = -(39.2 ± 0.5) kJ·mol -1 ( p o = 10 5 Pa).
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Solubility Diagram of lithium sulfate sodium sulfate rubidium sulfate aq at the temperature 298 15 k
The Journal of Chemical Thermodynamics, 1994Co-Authors: A. M. Kalinkin, S. K. Vasin, O.v. AntropovaAbstract:Abstract The phase-equilibrium Diagram of (lithium sulfate + sodium sulfate + rubidium sulfate)(aq) at T = 298.15 K has been calculated using Pitzer et al .'s equations. A new compound 5Li 2 SO 4 ·Na 2 SO 4 ·2Rb 2 SO 4 ·2H 2 O has been isolated. The results of the calculation have been confirmed by an experimental study of the Solubility. The molar Gibbs free energy of formation of the triple sulfate at T = 298.15 K according to the reaction: 5Li 2 SO 4 ·H 2 O(cr) + Na 2 SO 4 ·10H 2 O(cr) + 2Rb 2 SO 4 (cr) = 5Li 2 SO 4 ·Na 2 SO 4 · 2Rb 2 SO 4 ·2H 2 O(cr) + 13H 2 O(1) was found to be Δ c G o m = -(39.2 ± 0.5) kJ·mol -1 ( p o = 10 5 Pa).
Thorsteinn Loftsson - One of the best experts on this subject based on the ideXlab platform.
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soluble 1 1 complexes and insoluble 3 2 complexes understanding the phase Solubility Diagram of hydrocortisone and γ cyclodextrin
International Journal of Pharmaceutics, 2017Co-Authors: Christian Schönbeck, Günther H.j. Peters, René Holm, Tobias Madsen, Thorsteinn LoftssonAbstract:Abstract The molecular mechanisms underlying the drug-solubilizing properties of γ-cyclodextrin were explored using hydrocortisone as a model drug. The BS-type phase-Solubility Diagram of hydrocortisone with γ-cyclodextrin was thoroughly characterized by measuring the concentrations of hydrocortisone and γ-cyclodextrin in solution and the solid phase. The drug-solubilizer interaction was also studied by isothermal titration calorimetry from which a precise value of the 1:1 binding constant (K11 = 4.01 mM−1 at 20 °C) was obtained. The formation of water-soluble 1:1 complexes is responsible for the initial increase in hydrocortisone Solubility while the precipitation of entities with a 3:2 ratio of γ-cyclodextrin:hydrocortisone is responsible for the plateau and the ensuing strong decrease in Solubility once all solid hydrocortisone is used up. The complete phase-Solubility Diagram is well accounted for by a model employing the 1:1 binding constant and the Solubility product of the precipitating 3:2 entity ( K 32 S = 5.51 mM 5 ) . For such systems, a small surplus of γ-cyclodextrin above the optimum concentration may result in a significant decrease in drug Solubility, and the implications for drug formulations are briefly discussed.
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Soluble 1:1 complexes and insoluble 3:2 complexes – Understanding the phase-Solubility Diagram of hydrocortisone and γ-cyclodextrin
International journal of pharmaceutics, 2017Co-Authors: Christian Schönbeck, Tobias Løvgren Madsen, Günther H.j. Peters, René Holm, Thorsteinn LoftssonAbstract:Abstract The molecular mechanisms underlying the drug-solubilizing properties of γ-cyclodextrin were explored using hydrocortisone as a model drug. The BS-type phase-Solubility Diagram of hydrocortisone with γ-cyclodextrin was thoroughly characterized by measuring the concentrations of hydrocortisone and γ-cyclodextrin in solution and the solid phase. The drug-solubilizer interaction was also studied by isothermal titration calorimetry from which a precise value of the 1:1 binding constant (K11 = 4.01 mM−1 at 20 °C) was obtained. The formation of water-soluble 1:1 complexes is responsible for the initial increase in hydrocortisone Solubility while the precipitation of entities with a 3:2 ratio of γ-cyclodextrin:hydrocortisone is responsible for the plateau and the ensuing strong decrease in Solubility once all solid hydrocortisone is used up. The complete phase-Solubility Diagram is well accounted for by a model employing the 1:1 binding constant and the Solubility product of the precipitating 3:2 entity ( K 32 S = 5.51 mM 5 ) . For such systems, a small surplus of γ-cyclodextrin above the optimum concentration may result in a significant decrease in drug Solubility, and the implications for drug formulations are briefly discussed.
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Evaluation of cyclodextrin solubilization of drugs
International Journal of Pharmaceutics, 2005Co-Authors: Thorsteinn Loftsson, Dagný Hreinsdóttir, Már MássonAbstract:Abstract The most common stoichiometry of drug/cyclodextrin complexes is 1:1, i.e. one drug molecule forms a complex with one cyclodextrin molecule, and the most common method for stoichiometric determination during formulation studies is the phase-Solubility method. However, in recent years it has becoming increasingly clear that solubilizing effects of cyclodextrins are frequently due to the formation of multiple inclusion and non-inclusion complexes. The aqueous Solubility of 38 different drugs was determined in pure aqueous solution, aqueous buffer solutions and aqueous cyclodextrin solutions, and the apparent stability constant ( K 1:1 ) of the 1:1 drug/cyclodextrin complexes calculated by the phase-Solubility method. For poorly soluble drugs (aqueous Solubility S 0 ) is in general much larger than the intercept of the phase-Solubility Diagram ( S int ) resulting in non-linearity of otherwise linear ( A L -type) phase-Solubility Diagram. This can lead to erroneous K 1:1 -values. A more accurate method for determination of the solubilizing efficiency of cyclodextrins is to determine their complexation efficiency (CE), i.e. the concentration ratio between cyclodextrin in a complex and free cyclodextrin. CE is calculated from the slope of the phase-Solubility Diagrams, it is independent of both S 0 and S int , and more reliable when the influences of different pharmaceutical excipients on the solubilization are being investigated.
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Self Association and Cyclodextrin Solubilization of NSAIDs
Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2002Co-Authors: Audur Magnusdottir, Már Másson, Thorsteinn LoftssonAbstract:The phase Solubility profiles with HPβCD of thesodium salt of the NSAIDs(non-steriodal anti-inflammatory drugs) ibuprofen anddiflunisal were studied. Theslopes of the phase Solubility Diagrams were determinedfor the sodium salt of ibuprofenat pH 6.1, 6.3 and 6.7, and for the sodium salt ofdiflunisal at pH 6.1 and 8.4. In allcases the slope of the phase Solubility Diagram wasgreater than unity. These resultssuggested that the stoichiometry of the complex formedwas greater than unity withrespect to the drug. However molecular modeling, NMRand UV studies clearlyshowed that the complex stoichiometry was 1:1. Theseconflicting results can beexplained by applying the theory developed for micellarforming compounds. Thusthe solubilization of the drugs is due partially frominclusion complex formation andpartially from solubilization by aggregation. Wehave therefore demonstrated that theSolubility of drugs in a cyclodextrin solution isexplained not only by inclusioncomplex formation but also by non-inclusion associationof the uncomplexed drugwith the complex.
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Self-association and cyclodextrin solubilization of drugs.
Journal of pharmaceutical sciences, 2002Co-Authors: Thorsteinn Loftsson, Már Másson, Audur Magnusdottir, J. F. SigurjónsdóttirAbstract:The phase Solubility profiles with HPβCD of thesodium salt of the NSAIDs(non-steriodal anti-inflammatory drugs) ibuprofen anddiflunisal were studied. Theslopes of the phase Solubility Diagrams were determinedfor the sodium salt of ibuprofenat pH 6.1, 6.3 and 6.7, and for the sodium salt ofdiflunisal at pH 6.1 and 8.4. In allcases the slope of the phase Solubility Diagram wasgreater than unity. These resultssuggested that the stoichiometry of the complex formedwas greater than unity withrespect to the drug. However molecular modeling, NMRand UV studies clearlyshowed that the complex stoichiometry was 1:1. Theseconflicting results can beexplained by applying the theory developed for micellarforming compounds. Thusthe solubilization of the drugs is due partially frominclusion complex formation andpartially from solubilization by aggregation. Wehave therefore demonstrated that theSolubility of drugs in a cyclodextrin solution isexplained not only by inclusioncomplex formation but also by non-inclusion associationof the uncomplexed drugwith the complex.
U. Kiełkowska - One of the best experts on this subject based on the ideXlab platform.
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Solubility Diagram for the system KHCO3 + KVO3 + H2O at 293–323 K
Fluid Phase Equilibria, 2003Co-Authors: Mieczysław Trypuć, U. KiełkowskaAbstract:Abstract The Solubility of potassium bicarbonate and potassium meta-vanadate in water in the temperature range 293–323 K is reported. The concentration of vanadium(V) was determined using a spectrophotometric method applying hydrogen peroxide. The potassium ion concentration was measured by weight in the form of potassium tetraphenyloborate (K[B(C6H5)4]). The results were used to construct a part of the polythermal Solubility surface for the KHCO3+KVO3+H2O system. In addition, the solution density dependence versus the potassium meta-vanadate concentration expressed in water free mole fractions is presented. These data are essential for the evaluation of a new, non-waste production method of potassium carbonate.