Solubility of chlorine in aqueous hydrochloric acid solutions

The solubility of chlorine in aqueous hydrochloric acid solutions was studied. The effects of HCl concentration and temperature on the solubility were evaluated, and the thermodynamic parameters of the dissolution were calculated. It was found that the solubility isotherms had a minimum at about 0.5M HCl concentration at all the temperatures studied and that solubility decreased with the increase of temperature at all the HCl concentration range investigated.     

Release of Ibuprofen from Polyethylene glycol solid dispersions:-Equilibrium solubility approach

This work is an attempt to enhance the release of Ibuprofen by improving its aqueous solubility. This was done by dispersing the drug in a water soluble carrier such as polyethylene glycol (PEG). The solubility was found to depend on various factors such as method of preparation, carrier weight fraction and molecular weight and the pH of the medium. It was found that dispersions prepared by the fusion method gave higher solubilities than those prepared by the solvent technique. The solubility was found to vary with carrier molecular weight and its weight fraction. Decreasing the PEG molecular weight resulted in increased solubility. A polymer to drug ratio of 1:1 was found to give the highest solubility. The solubility decreased as the polymer weight fraciton was increased beyond this value. The solubility of the solid dispersion was found to be pH dependent. A greater solubility was obtained at higher pHs than at lower ones. This was attributed to the weakly acidic nature of Ibuprofen. Calculation of the heat of solution of the various systems studied showed that the non dispersed drug had a higher heat of solution than the dispersed systems. This was thought to be the cause of the higher solubility of the dispersions as compared to the original drug.     

Solubility of copper in titanium carbide

The solubility of copper in titanium carbide (TiC_x) was studied experimentally. The solubility was assessed in two different ways: (a) titanium carbide was added to a copper—titanium melt, (b) titanium carbides formed in situ, from graphite and titanium, were analysed. The stoichiometries were implicitly assessed. The solubility of copper in titanium carbide was found to decrease with increasing carbon content. This behaviour was compared to the solubility of chromium in titanium carbide, which increases in solubility with increasing carbon content. The role of vacancies in the solution is briefly discussed.

MST/3502     

Release of Ibuprofen from Polyethylene glycol solid dispersions:-Equilibrium solubility approach

Abstract

This work is an attempt to enhance the release of Ibuprofen by improving its aqueous solubility. This was done by dispersing the drug in a water soluble carrier such as polyethylene glycol (PEG). The solubility was found to depend on various factors such as method of preparation, carrier weight fraction and molecular weight and the pH of the medium. It was found that dispersions prepared by the fusion method gave higher solubilities than those prepared by the solvent technique. The solubility was found to vary with carrier molecular weight and its weight fraction. Decreasing the PEG molecular weight resulted in increased solubility. A polymer to drug ratio of 1:1 was found to give the highest solubility. The solubility decreased as the polymer weight fraciton was increased beyond this value. The solubility of the solid dispersion was found to be pH dependent. A greater solubility was obtained at higher pHs than at lower ones. This was attributed to the weakly acidic nature of Ibuprofen. Calculation of the heat of solution of the various systems studied showed that the non dispersed drug had a higher heat of solution than the dispersed systems. This was thought to be the cause of the higher solubility of the dispersions as compared to the original drug.     

A Four-Component Study for Estimating Solubilities of a Poorly Soluble Compound in Multisolvent Systems Using a Scheffé-Type Model

Abstract

The equilibrium solubility of GF1209184, a poorly soluble compound with potential use as a multidrug resistance (MDR) inhibitor of P-glycoprotein, was studied at 25°C in multisolvent systems containing polyethylene glycol 300, polysorbate 80, ethanol, and water. The objective was to determine the feasibility, with respect to solubility, of formulating a concentrated formulation for product presentation in an ampule or vial. Data were fit to a quadratic Scheffé-type model with excellent correlation between the experimentally determined and fitted equilibrium solubilities (R² = 0.9875, slope = 1.043). Solubilities greater than 4 mg base/mL at 25°C were determined for mixtures in this study, making it feasible, with regard to solubility, to formulate a concentrated vial or ampule formulation. Maximum solubility, however, was dependent on the ability to adjust the apparent pH to ≤3.5 in the cosolvent/surfactant systems studied.     

Heterogeneous Equilibria in Aqueous Solutions of Uranovanadates Ak(VUO6)k·nH2O (Ak = H,Na, K,Rb, Cs,Tl, Mg,Ca, Sr,Ba, Co,Ni, Cu,Pb)

The state of mineral-like uranovanadates of mono- and bivalent metals in aqueous solutions was studied. Based on experimental solubility data, the reaction equilibria in the crystal uranovanadate-aqueous solution system were described quantitatively, which, in turn, allowed evaluation of the solubility products of uranovanadates and their standard Gibbs energies of formation and prediction of the solubility of these compounds in aqueous solutions of various compositions under the isobaric-isothermal conditions.     

Amorphous azithromycin with improved aqueous solubility and intestinal membrane permeability

Azithromycin (AZM) is a poorly soluble macrolide antibacterial agent. Its low solubility is considered as the major contributing factor to its relatively low oral bioavailability. The aim of this study was to improve the solubility of this active pharmaceutical ingredient (API) by preparing an amorphous form by quench cooling of the melt and to study the influence of the improved solubility on membrane permeability. The amorphous azithromycin (AZM-A) exhibited a significant increase in water solubility when compared to the crystalline azithromycin dihydrate (AZM-DH). The influence that the improved solubility could have on membrane permeability was also studied. The apparent permeability coefficient (P_app) values of AZM-A were statistically significantly higher (p?相似文献   

A study of the zirconium-oxygen interaction in silicon

The energy levels created by zirconium in silicon (0.65, 0.52, and 0.32 eV) were determined from the photoconductivity data. The oxygen solubility in zirconium-doped silicon was studied. It was established that zirconium affects the solubility of interstitial oxygen.     

Apparent solubility of drugs in partially crystalline systems

Using several griseofulvin samples, representing different solid-state structures, the solubility behavior of drugs in both one-state (totally ordered, semiordered or disordered) and two-state systems was studied. Special attention was directed towards the surface structure of the particles. The partially crystalline samples were obtained by milling the raw material (crystalline standard) or storing the quenched sample (amorphous standard). The solid-state structure of the materials was studied using x-ray diffraction (XRD), differential scanning calorimetry (DSC), isothermal microcalorimetry (IMC), and scanning electron microscopy (SEM). The saturation concentration of the materials was studied in suspensions containing different dispersion concentrations of drug after centrifugation and filtration, using spectrophotometry. In all cases these dispersion concentrations exceeded the solubility of the drug. The solubilities were plotted vs. dispersion concentrations for each sample. Several solubility plateaus were found. The lowest and highest solubility plateaus corresponded to the solubilities of crystalline and amorphous standards. These plateaus were reached at 8 and 44 µg/mL for crystalline and amorphous griseofulvin standards, respectively. An intermediate plateau served as an indication of the existence of a totally semiordered structure. This was reached at 19 µg/mL for griseofulvin. Any deviation from these plateaus was suggested to be indicative of the existence of heterogeneity on the surface structure, which in most cases could be described as a two state system. In such cases, the apparent solubility was a function of dispersion concentration, until at very high dispersion concentrations (4000-20,000 µg/mL) the saturation concentration of the totally disordered (44 µg/mL) or semiordered (19 µg/mL) one-state phase was reached. No reduction in these values was observed during storage for 50 days. It is thus concluded that, in partially crystalline systems, the saturation concentration is an interfacial phenomenon, which depends on the amount, reactivity, and solid-state structure of the exposed solid surfaces in equilibrium with the solution. A simplified solubility model is proposed to qualitatively describe the relationship between established apparent solubilities (saturation concentrations) and different combinations of solid-state structures.     

Apparent Solubility of Drugs in Partially Crystalline Systems

Abstract

Using several griseofulvin samples, representing different solid-state structures, the solubility behavior of drugs in both one-state (totally ordered, semiordered or disordered) and two-state systems was studied. Special attention was directed towards the surface structure of the particles. The partially crystalline samples were obtained by milling the raw material (crystalline standard) or storing the quenched sample (amorphous standard). The solid-state structure of the materials was studied using x-ray diffraction (XRD), differential scanning calorimetry (DSC), isothermal microcalorimetry (IMC), and scanning electron microscopy (SEM). The saturation concentration of the materials was studied in suspensions containing different dispersion concentrations of drug after centrifugation and filtration, using spectrophotometry. In all cases these dispersion concentrations exceeded the solubility of the drug. The solubilities were plotted vs. dispersion concentrations for each sample. Several solubility plateaus were found. The lowest and highest solubility plateaus corresponded to the solubilities of crystalline and amorphous standards. These plateaus were reached at 8 and 44 µg/mL for crystalline and amorphous griseofulvin standards, respectively. An intermediate plateau served as an indication of the existence of a totally semiordered structure. This was reached at 19 µg/mL for griseofulvin. Any deviation from these plateaus was suggested to be indicative of the existence of heterogeneity on the surface structure, which in most cases could be described as a two state system. In such cases, the apparent solubility was a function of dispersion concentration, until at very high dispersion concentrations (4000–20,000 µg/mL) the saturation concentration of the totally disordered (44 µg/mL) or semiordered (19 µg/mL) one-state phase was reached. No reduction in these values was observed during storage for 50 days. It is thus concluded that, in partially crystalline systems, the saturation concentration is an interfacial phenomenon, which depends on the amount, reactivity, and solid-state structure of the exposed solid surfaces in equilibrium with the solution. A simplified solubility model is proposed to qualitatively describe the relationship between established apparent solubilities (saturation concentrations) and different combinations of solid-state structures.     

The effect of 2-hydroxypropyl-beta-cyclodextrin on in vitro drug release of steroids from suppository bases

The effects of 2-hydroxypropyl-β-cyclodextrin (HPCD) on drug solubility and drug release from suppository bases were studied for dexamethasone (DX), dexamethasone acetate (DXA), hydrocortisone (HC), hydrocortisone acetate (HCA), and prednisolone acetate (PNA). It was found that HPCD significantly increased the aqueous solubility of all five steroids, and the increased drug solubility significantly influenced the drug release from the polyethylene glycol (PEG) base but not from the cocoa butter base.     

Heterogeneous Equilibria in the System MHSiUO6·nH2O-Aqueous Solution (M = Li,Na, K)

The aqueous solutions of mineral-like compounds MHSiUO₆·nH₂O (M = Li, Na, K) at 298 K were studied. A quantitative model of a crystalline uranosilicate-aqueous solution system was derived from the solubility data and was used to calculate the solubility products and Gibbs formation functions of these compounds. The Gibbs energies of formation of silicic acid and other ionic and molecular Si(IV) species in solution were also calculated. The solubility of uranosilicates in aqueous solutions outside the experimentally studied range was predicted.     

Effect of hydroxypropyl beta-cyclodextrin on drug solubility in water-propylene glycol mixtures

Combined effects of cosolvency and inclusion complexation on drug solubility were studied using a model hydrophobic compound (carbamazepine) and a model hydrophilic compound (Compound S). Propylene glycol (PG) was used as the nonaqueous solvent, and deionized water was employed for the aqueous systems. Hydroxypropyl β-cyclodextrin (HPβCD) was chosen as the complexing agent and studied at concentrations up to 28% (w/v). Complex formation constants (K_c) and solubility enhancement ratios were determined for the respective compounds in various water/PG vehicles. The data suggested that the inclusion of the compounds was most favorable when water alone was used as the vehicle. However, the combined approach of cosolvency and complexation resulted in a significant increase in the total apparent solubility of carbamazepine (the hydrophobic compound). The same was not observed with Compound S (the hydrophilic model), since PG weakened the interactions between the molecule and HPβCD, and thus, no synergistic or additive effects were observed with the combined approach of complexation and cosolvency.     

Solid carriers for improved solubility of glipizide in osmotically controlled oral drug delivery system

The purpose of this study was to increase the solubility of glipizide (gli) by solid dispersions SDs technique with polyvinylpyrrolidone (PVP) in aqueous media. The gli-PVP solid dispersion systems was prepared by physical mixing or spray drying method, and characterized by differential scanning calorimetry (DSC), X-ray powder diffraction (XRD) analysis, Fourier transformation-infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The elementary osmotic pumps (EOPs) were prepared with gli-PVP complex and the effect of the PVP percentages on the enhancing of gli dissolution rate was studied. The influences of various parameters e.g., drug- PVP ratio, level of solubility modifier, coating weight gain and diameter of drug releasing orifice on drug release profiles were also investigated. The solubility and dissolution rates of gli were significantly increased by solid dispersion using spray dried method as well as their physical mixture. The obtained results indicated that gli-PVP solid dispersion system has suitable solubility behavior in EOP tablets.     

Influence of water on the solubility of two steroid drugs in hydrofluoroalkane (HFA) propellants

The objective of this research work was to investigate the influence of water level, temperature, and propellant composition on the solubility of two hydrophobic steroid drugs, triamcinolone acetonide (TAA) and beclomethasone diapropionate (BDP). pMDIs containing TAA or BDP, spiked water, and propellant blend with different ratios of HFA 134a and HFA 227 were prepared. The contents of the prepared pMDIs were filtered through a 0.22 mm Acrodisc, syringe filter into a receiving canister after the pMDIs were equilibrated at 15°C, 25°C, 30°C, and 40°C. The drug concentration in the receiving canisters was determined by HPLC and the drug solubility in the propellant blend was calculated. Also, the drug crystal collected on the filter from the donor pMDIs were characterized by x-ray diffraction. The solubility of TAA and BDP varied with propellant composition at all experimental temperatures investigated. The solubility of TAA and BDP increased as the temperature was increased at all propellant compositions and water levels studied, but decreased as the water level in the propellant system was increased at all compositions and temperatures. The x-ray diffraction results indicated that the water in the propellant system had no significant influence on the crystal characteristics of TAA in HFA propellant system, but had a significant impact on the crystal characteristics of BDP was higher than TAA at all propellant compositions, experimental temperatures and water levels investigated. The solubility of TAA and BDP was not only influenced by propellant composition and storage temperature, but also depended on the water level in the propellant system. As a consequence, the crystallinity of the drugs formulated in HFA propellant was influenced by the temperature, propellant composition and the water level in the propellant system. The impact of these factors on the crystallinity of formulated drugs.     

Aqueous Solubility of Diclofenac Diethylamine in the Presence of Pharmaceutical Additives: A Comparative Study with Diclofenac Sodium

Aqueous solubility of diclofenac diethylamine (DDEA), a nonsteroidal anti-inflammatory drug currently formulated as a topical emulgel, was studied in the presence of pharmaceutical additives and compared with diclofenac sodium (DS). Electrolytes at low concentrations exhibited a salting-in effect on DDEA with peak solubility that was attributed to the association of DDEA into micelles, followed by a salting-out effect at higher concentrations, by which structure formation by DDEA molecules increased and precipitation occurred. For DS, which is not capable of forming micelles, the salting-out effect was dominant due to the common ion effect. Cosolvents displayed significant enhancement in solubility of both salts except glycerol, which showed a slight increase in solubility of DDEA and a decrease in solubility of DS due to transformation into the less soluble hydrate form. Ethanol and polyethylene glycol (PEG) 400 cosolvent systems at all concentrations showed positive deviations from the log-linear solubility equation. In the case of propylene glycol (PG) cosolvent systems, negative deviations were observed at low volume fractions of cosolvent, while positive deviations were observed at high volume fractions of cosolvent for DS and DDEA. The parent drug, being less ionizable and highly nonpolar, showed negative deviations up to 90% PG content. Thus, the positive deviations for DS and DDEA could be attributed to the more ionizable carboxylic group and its higher ability for hydrogen bonding at higher fractions of cosolvent. Polyvinylpyrrolidone (PVP) and PEG4000 or PEG6000 enhanced the solubility of DS and DDEA, with PVP exerting higher solubilizing efficiency and DS showing better solubility than DDEA. Solubilities of DS in Tween 80 (T80) and Pluronic F-127 (PF127) aqueous solutions were almost similar, while the solubility of DDEA in the presence of T80 was higher than the solubility in the presence of PF127. DS appeared to be located more in the polyoxyethylene mantle of the micelles, while DDEA was located more in the core of the micelles.     

Aqueous solubility of diclofenac diethylamine in the presence of pharmaceutical additives: a comparative study with diclofenac sodium

Aqueous solubility of diclofenac diethylamine (DDEA), a nonsteroidal anti-inflammatory drug currently formulated as a topical emulgel, was studied in the presence of pharmaceutical additives and compared with diclofenac sodium (DS). Electrolytes at low concentrations exhibited a salting-in effect on DDEA with peak solubility that was attributed to the association of DDEA into micelles, followed by a salting-out effect at higher concentrations, by which structure formation by DDEA molecules increased and precipitation occurred. For DS, which is not capable of forming micelles, the salting-out effect was dominant due to the common ion effect. Cosolvents displayed significant enhancement in solubility of both salts except glycerol, which showed a slight increase in solubility of DDEA and a decrease in solubility of DS due to transformation into the less soluble hydrate form. Ethanol and polyethylene glycol (PEG) 400 cosolvent systems at all concentrations showed positive deviations from the log-linear solubility equation. In the case of propylene glycol (PG) cosolvent systems, negative deviations were observed at low volume fractions of cosolvent, while positive deviations were observed at high volume fractions of cosolvent for DS and DDEA. The parent drug, being less ionizable and highly nonpolar, showed negative deviations up to 90% PG content. Thus, the positive deviations for DS and DDEA could be attributed to the more ionizable carboxylic group and its higher ability for hydrogen bonding at higher fractions of cosolvent. Polyvinylpyrrolidone (PVP) and PEG4000 or PEG6000 enhanced the solubility of DS and DDEA, with PVP exerting higher solubilizing efficiency and DS showing better solubility than DDEA. Solubilities of DS in Tween 80 (T80) and Pluronic F-127 (PF127) aqueous solutions were almost similar, while the solubility of DDEA in the presence of T80 was higher than the solubility in the presence of PF127. DS appeared to be located more in the polyoxyethylene mantle of the micelles, while DDEA was located more in the core of the micelles.     

Solubilization of Paracetamol Using Non-Ionic Surfactants and Co-Solubilizers

The influence of certain aqueous non-ionic surfactants, cosolvents and cosolvent - surfactant blends on the enhanced solubility of paracetamol were studied. Dielectric constants of these solvent systems with and without paracetamol were determined. In several instances, paracetamol was increased in solubility by 5-7 fold, depending on the system used. Dielectric constants were affected to varying degrees by these systems.

The cosolvents, propylene glycol and glycerin apparently suppress micelle formation.     

Solubility advantage of sulfanilamide and sulfacetamide in natural deep eutectic systems: experimental and theoretical investigations

Objective: The aim of this study was to explore the possibility of using natural deep eutectic solvents (NADES) as solvation media for enhancement of solubility of sulfonamides, as well as gaining some thermodynamic characteristics of the analyzed systems.

Significance: Low solubility of many active pharmaceutical ingredients is a well-recognized difficulty in pharmaceutical industry, hence the need for different strategies addressing this problem. Among such strategies, those that are environmentally and economically beneficial are of particular interest.

Methods: The solubility of sulfanilamide and sulfacetamide in 21 different NADES compositions comprising choline chloride with sugars or sugar alcohols was measured spectrophotometrically. Thermodynamic parameters describing the studied systems were determined using the COSMO-RS computational protocol.

Results: All of the considered NADES compositions gave an increase in solubility of the studied sulfonamides, with the highest solubilities obtained for the system comprising choline chloride and glycerol in unimolar proportions, which gave a solubility advantage of 83.7 and 73.8 for sulfanilamide and sulfacetamide, respectively. Theoretical studies indicated that the dissolution of both considered sulfonamides has a low endothermic character, with the lowest enthalpy values obtained for the most optimal, i.e. unimolar, proportions. The non-monotonous trend of enthalpy of dissolution was also discussed in terms of intermolecular interactions.

Conclusions: The obtained results show the feasibility of using NADES as solubility enhancers for sulfonamides and encourage for further exploration in this field.     

Wettability,water sorption and water solubility of seven silicone elastomers used for maxillofacial prostheses

The wettability, water sorption and solubility of silicone elastomers used for maxillofacial prostheses were studied. The hypothesis was, that a material that has absorbed water would show an increase in the wettability and thus also the surface free energy of the material. Seven silicone elastomers, both addition- and condensation type polymers, were included. Five specimens of each material were subjected to treatment according to ISO standards 1567:1999 and 10477: 2004 for water sorption and solubility. The volumes of the specimens were measured according to Archimedes principle. The contact angle was measured with a contact angle goniometer at various stages of the sorption/solubility test. Wettability changed over the test period, but not according to theory. The addition type silicones showed little or no sorption and solubility, but two of the condensation type polymers tested had a significant sorption and solubility. This study showed that condensation type polymers may show too large volumetric changes when exposed to fluids, and therefore should no longer be used in prosthetic devices. The results of this study also suggests that it might be of interest to test sorption and solubility of materials that are to be implanted, since most of the materials had some solubility.