Solubility Product Research Articles

Maximizing the Hesperidin Extraction Using Supercritical Carbon Dioxide and Ethanol: Theoretical Prediction and Experimental Results

Agroindustrial waste can be valorized towards the obtaining of several products such as pigments, proteins, fibers, and polyphenolic compounds with antioxidant capacity. Orange peel waste is a promising source of polyphenolic compounds such as hesperidin. However, conventional extraction techniques present some environmental limitations such as high solvent consumption and high wastewater generation. Supercritical fluid extraction (SFE) has emerged as a green extraction technique due to the low use of solvent. The aim of this study was to maximize the hesperidin extraction based on theoretical predictions of the operating conditions from empirical thermodynamic models using SFE with carbon dioxide (CO2) as a solvent. The theoretical conditions were validated experimentally on a semi-pilot scale. The extracts were evaluated in terms of hesperidin content, total polyphenol content, and antioxidant capacity. Thermodynamic prediction of the operating conditions showed that the ethanol used as a co-solvent promotes hesperidin extraction. The optimum operating conditions were 25 °C, 80 bar, and a volumetric co-solvent concentration of 10%. The validation of the operating conditions resulted in a final hesperidin concentration of 11.5 ± 0.03 g/kg of orange peel waste. The experimental results were 30.26-times higher using 10% vol of ethanol than the extraction of hesperidin with pure ethanol as a co-solvent. The total polyphenol content and antioxidant capacity resulted in 831.92 ± 40.01 mg Galic acid/100 g orange peel waste, 15.41± 0.91 EC50/mL, and 5.31 ± 0.67 µMolTrox/100 g orange peel. Finally, the prediction of operating conditions from empirical thermodynamic models such as the Peng–Robinson equation of state with some modifications (Stryjek Vera) for solid–gas equilibrium solubility calculations, allows for maximizing the content of the polyphenolic compounds using SFE.

Diversified competitive sulfuration behaviors of concomitant heavy metal ions on copper recovery from copper smelting waste acid

Currently, sulfuration is widely used for the Cu(II) recovery from copper smelting waste acids (CSWA). However, the abundant concomitant heavy metal ions (HMIs) seriously obstruct Cu(II) recovery. In this paper, we find that the precipitation difficulty of HMI sulfide is determined by solubility product constant (Ksp), H+ concentration and S(−II) concentration, resulting in the diversified competitive sulfuration behaviors of concomitant HMIs on Cu(II) recovery. For concomitant HMIs without S(−II)-consuming ability, the positive-side competitive sulfuration behaviors on Cu(II) recovery are in the order of In(III) > Zn(II) > Ni(II) > Fe(II) > Mn(II). However, with the formation of concomitant HMIs sulfides, the negative-side competitive sulfuration behaviors on Cu(II) recovery are in the order of Fe(III) > As(III) > Bi(III) > Cd(II). According to the results of diffusion-growth-dissolution model, the S(−II)-combining process on HMIs surface is divided into S(−II)-capturing and S(−II)-consuming stages, related to Ksp value and HMIs precipitation, respectively. In actual CSWA, 5000 ∼ 15000 mg/L As(III) seriously inhibits the recovery efficiency of 500 ∼ 2000 mg/L Cu(II), and other concomitant HMIs (e.g., 250 ∼ 1200 mg/L Zn(II), 300 ∼ 450 mg/L Cd(II), 10 ∼ 200 mg/L Bi(III) and 20 ∼ 200 mg/L Fe(II)) will further affect Cu(II) recovery. Besides, ignoring these diversified competitive sulfurations of concomitant HMIs induces unreasonable S(−II) concentration for complete Cu(II) recovery, resulting in Cu(II) recovery issues: As(III) precipitation and Cu(II) residue. Thus, timely information in instantaneous Cu(II) concentration is a feasible strategy to accurately adjust S(−II) concentration via Cu(II) quantitative model. This work is devoted to the efficient and controllable recovery of Cu resources and the reduction of As-containing hazardous wastes in sulfuration treatment of actual CSWA.

Solubility of NaCl in water vapor at 400–700 °C

Water significantly impacts the chemical evolution of the Earth’s crust, affecting environments from volcanic settings to hydrothermal systems. These fluids transport elements essential for geological processes, such as metal ore deposit formation. At high temperatures, as water transitions from liquid to vapor, its molecular structure changes, drastically reducing its capacity to dissolve solids and solvate ions. Here, we report experimental results of halite (NaCl(s)) solubility in water vapor at 400–700 °C and 30–300 bar using a novel U-tube flow-through reactor system. The results show that halite solubility is low (xNaCl,tot = 3.2 × 10−9 to 2.9 × 10−4 mol/mol) and increases with temperature and pressure, attributed to the dissolution of NaCl followed by its hydration according to the reaction:NaCl(s)+nH2O(g)⇋NaCl·H2On(g)Thermodynamic modeling of the experimental results indicates a preference for specific hydrated species, including NaClg, NaCl·H2O4g, NaCl·H2O6g and NaCl·H2O8g. The less hydrated gaseous NaCl species become more prevalent with increasing temperature and decreasing pressure. At temperatures below 600 °C and pressures above 50 bar, halite solubility is close to stoichiometric, whereas at higher temperatures and lower pressures, the hydrolysis of NaCl(s) to form NaOH(lq,s) or a NaClxOH(1-x)(lq,s) (x < 1) solid solution is evident, resulting in the formation of HCl(g). The logarithm of the halite equilibrium solubility constant (logKn) ranges from −10.18 to −4.19 for NaCl(g), and from −13.12 to −11.94, −15.90 to −17.28, and −19.67 to –22.73 for NaCl·H2O4(g), NaCl·H2O6(g) and NaCl·H2O8(g), respectively. Standard thermodynamic properties derived from this data reveal a temperature-independent enthalpy (ΔHn,ro), entropy (ΔSn,ro) and heat capacity (ΔCp,n,ro) of reaction for each NaCl species. While the enthalpy of reaction is nearly constant, the entropy and heat capacity decrease with an increasing degree of hydration, indicating the decreasing stability of these species with increasing temperature. Our thermodynamic model results and gas species stoichiometries are in excellent agreement with previous density functional theory (DFT) calculations (Suleimenov et al., 2006). The halite solubility data obtained here compare well with prior studies and thermodynamic models for the NaCl-H2O system.

Bioavailability Improvement by Atomic Layer Coating: Fenofibrate A Case Study

Biopharmaceutical Classification Systems (BCS) class II drugs show poor solubility and high permeability in the body. Fenofibrate (FF) is a classic example of a BCS class II drug, used to treat high cholesterol and triglyceride (fat-like substances) levels in the blood. Atomic layer coating (ALC) is a surface engineering technology adapted from the semiconductor industry, where metal oxides are coated one atomic layer at a time over the active pharmaceutical ingredients (API) particles. ALC coating was proven to improve the processability, alter the hydrophilicity, improve the stability, and fine-tune the release of drugs. Herein, we report the intervention of ALC coating in enhancing the bioavailability of a poorly water-soluble drug (fenofibrate) in the animal model. The physical properties of uncoated fenofibrate were compared with those of zinc oxide-coated and silicon oxide-coated fenofibrate. Following the application of the coatings, the structural integrity (both chemical stability and solid-state stability) of the active pharmaceutical ingredient (API) remained uncompromised, as corroborated by 1H NMR and powder X-ray diffraction analyses. Notably, zinc oxide-coated fenofibrate exhibited favorable flow characteristics, whereas no discernible enhancement in flow behavior was observed for silicon oxide-coated fenofibrate. The results from contact angle measurements suggest that the silicon oxide-coated fenofibrate exhibits superior wetting behavior, as indicated by a contact angle nearing 0°. The application of ALC demonstrates an enhanced dissolution rate when compared to the uncoated active pharmaceutical ingredient (API) while leaving its equilibrium solubility unaffected. Coating the API with silicon oxide improves particle hydrophilicity and wetting properties, whereas zinc oxide coating aids in particle de-agglomeration, thereby enhancing their interaction with an aqueous medium. In vivo bioavailability studies conducted on rodents and larger animal (dog) models indicate a substantial increase in bioavailability (approximately 2 times) for the silicon oxide-coated API in comparison to the uncoated API, as determined by the area under the curve (AUC). Furthermore, the Cmax values for the silicon oxide-coated API also demonstrate a significant increase (approximately 3 times) over the uncoated API. Notably, an oral subacute toxicity study of ALC silicon-coated fenofibrate revealed no toxic effects attributable to the coating. This study underscores the potential of ALC in augmenting the bioavailability of BCS(II) drugs.

Shortwave-Infrared Silver Chalcogenide Quantum Dots for Optoelectronic Devices.

Silver chalcogenide (Ag2X, X = S, Se, Te) semiconductor quantum dots (QDs) have been extensively studied owing to their short-wave infrared (SWIR, 900-2500 nm) excitation and emission along with lower solubility product constant and environmentally benign nature. However, their unsatisfactory photoluminescence quantum yields (PLQYs) make it difficult to obtain optoelectronic devices with high performances. To tackle this challenge, researchers have made great efforts to develop valid strategies to improve the PLQYs of SWIR Ag2X QDs by suppressing their nonradiative recombination of excitons. In this Perspective, we summarize the significant approaches of heteroatom doping and surface passivation to enhance the PLQYs of SWIR Ag2X QDs, and we conclude their application in high-efficiency optoelectronic devices. Finally, we examine the future trends and promising opportunities of Ag2X QDs with regard to their optical properties and optoelectronics. We believe that this Perspective will serve as a valuable reference for future advancement in the synthesis and application of SWIR Ag2X QDs.

Thermally Stable High-Entropy Layered Double Hydroxides for Advanced Catalysis.

Layered double hydroxides (LDHs), especially high-entropy LDHs (HE-LDHs), have gained increasing attention. However, HE-LDHs often possess poor thermal stability, restricting their applications in thermo-catalysis. Herein, a novel complexing nucleation method is proposed for engineering HE-LDHs with enhanced thermal stability. This approach precisely controls the nucleation of metal ions with different solubility products, achieving homogeneous nucleation and effectively mitigating phase segregation and transformation at elevated temperatures. The prepared HE-LDH sample demonstrated exceptional thermal stability at temperatures up to 300°C, outperforming all previously reported LDHs. Importantly, these HE-LDHs preserve both Lewis and Brønsted acidic sites, enabling the 100% removal of aromatic sulfides and alkaline nitrogen compounds from fuel oils in thermo-catalytic oxidation reactions. Experimental and characterization findings reveal that the metal-hydroxide bonds in the prepared HE-LDHs are strengthened by associated hydroxyl groups, inducing negative thermal expansion and augmenting the presence of acidic sites, thereby ensuring structural stability and enhancing catalytic activity. This study not only proposes a strategy for engineering HE-LDHs with remarkable thermal stability but also highlights potential applications of LDHs in thermo-catalysis.

ВІДНОВЛЕННЯ ПАЛАДІЄВИХ МЕМБРАН ПІСЛЯ КОНТАКТУ З ВОД-НЕМ ДЛЯ ВОДНЕВО-КИСНЕВИХ ПАЛИВНИХ ЕЛЕМЕНТІВ

Annotation. Studying the deformations of palladium membranes under the influence of hydrogen, which is a relevant issue for hydrogen energy and the nuclear industry. The mechanisms of palladium membrane shape change due to hydrogen penetration and the formation of temporary gradient alloys such as α-PdHn are consid-ered. Experiments were conducted using a hydrogen-vacuum installation, where the processes of membrane satu-ration and degassing were studied at temperatures from 100°C to 360°C and hydrogen pressures from 0.01 MPa to 2.5 MPa. It was established that the change in the shape of the membrane occurs in two stages: first, a rapid bending of the membrane is observed, and then a gradual return to the initial state. It was established that the maximum change in the shape of the membrane, which occurs at a constant temperature, depends on the diffu-sion coefficient and the equilibrium solubility of hydrogen in palladium. However, when the temperature chang-es, the diffusion coefficient of hydrogen in palladium and the equilibrium concentration of hydrogen in palladi-um also change, which affects the temperature dependence of the final shape change of the membrane. This fact makes it possible to effectively determine the time of hydrogen penetration into the membrane, control the change in shape and adjust the operating modes of the fuel cell. Special attention is paid to the use of palladium alloys with copper and silver to increase the resistance of membranes to the influence of hydrogen. It is shown that such alloys have better mechanical characteristics and a longer service life at high temperatures. The effect of degassing on the restoration of membranes after contact with hydrogen was studied, the main factors affecting the efficiency of this process were determined. The results of the work confirm the need for further research on increasing the resistance of palladium membranes to deformations, as well as the development of new materials and technologies to improve their operational characteristics

Characterization and solubility measurement of synthetic uranophane and sklodowskite under oxic groundwater conditions

Naturally occurring uranyl silicates can serve as solubility-limiting solid phases (SLSPs) of U(VI) in the oxic environment of granitic groundwater, which is likely to occur in crystalline host rock media in Korea. In this study, two synthetic uranyl silicates, uranophane (Ca[UO2SiO3OH]2·5H2O) and sklodowskite (Mg[UO2SiO3OH]2·6H2O) were prepared and used to measure the U(VI) solubility in simulated groundwater (sGW), mimicking the composition of samples collected from the underground research tunnel at the Korea Atomic Energy Research Institute (KAERI). The solid- and solution-phase species involved were examined in detail using various characterization methods. According to the powder X-ray diffraction pattern and elemental analysis results, the synthetic mineral phases, which were identified as uranophane-α and sklodowskite having layered crystal structures, were retained intact in sGW; however, in 0.1 M NaClO4, emergence of other solid phases was observed. Enhanced FTIR and Raman spectroscopic data, particularly in the regions of 790–860 and 940–1020 cm−1 for the UO22+ and SiO44− ions, respectively, enable monitoring the changes in the solid phases. Ternary Ca–U(VI)-tricarbonato complexes were identified as the dominant dissolved U(VI) species in sGW using time-resolved laser-induced luminescence spectroscopy. Furthermore, the solubility constant of uranophane was calculated (log Ks,0° = 10.3 ± 0.4) and compared with the predicted values based on our geochemical modeling analysis and previously reported ones.

Solubility of Amoxicillin Trihydrate Hydrochloride in Water

Objectives: This study aims to determine the solubility of amoxicillin trihydrate hydrochloride in water at different temperatures, addressing the scarcity of solubility data for this substance in the literature. The research focuses on the solubility behavior of the semi-synthetic antibiotic, part of the β-lactam group, widely used orally. Theoretical Framework: Amoxicillin is a β-lactam antibiotic of great therapeutic importance. Its solubility is relevant to the effectiveness of oral formulations and varies according to temperature. The literature on the solubility equilibrium of this compound is limited, motivating new studies that assist in the development of pharmaceutical solutions and the understanding of its physicochemical properties. Method: The solubility of amoxicillin trihydrate hydrochloride was determined at three temperatures: 298.15 K, 309.15 K, and 318.15 K, using the UV spectrophotometry method. The experiment involved 3 hours of stirring and 2 hours of decantation, with a 1 mL aliquot taken for analysis. The samples were diluted in 100 mL volumetric flasks and analyzed by spectrophotometer. Results and Discussion: The experimental results allowed correlating the solubility of amoxicillin trihydrate hydrochloride with empirical equations from the literature. The solubilities obtained demonstrated precision, with low relative deviation between the experimental values and those calculated by the equations. This indicates that the empirical models are adequate for predicting solubility behavior at different temperatures. Research Implications: The research contributes to enriching the solubility database of antibiotics, essential for drug formulation and the development of new therapeutic applications. The precision of the experimental data supports future studies in the field of pharmacology and chemical engineering, particularly in the context of solid and liquid formulations. Originality/Value: The study is original in addressing the solubility of amoxicillin trihydrate hydrochloride in water at different temperatures, filling a gap in the literature. Additionally, the use of UV spectrophotometry and the correlation of the data with empirical equations reinforce the validity of the results, making it valuable for researchers and professionals in the pharmaceutical sector.

Synthesis of Au/Ce2S3@CeO2/CuS nanocomposites for promoted catalytic performance in propargylamine conversion

A newly developed nanocomposite catalyst, Au/Ce2S3@CeO2/CuS, has been engineered for effective propargylamine synthesis through the A3 coupling reaction. The catalyst’s synthesis involved the targeted addition of 15 wt% CeO2 to the CuS sulfur precursor, leading to the formation of a Ce2S3 layer due to its lower solubility product constant (Ksp). This layer, along with 0.5 wt% Au nanoparticles, significantly increased the Ce3+ concentration (16.9 % to 33 %∼52 %), which can accelerate the Cu+/Cu2+ valence state changes, thereby promoting the activation of the alkynyl hydrogen to enhance propargylamine formation. After 2 h reaction, the Au/Ce2S3@CeO2/CuS catalyst achieved over 99 % conversion, nearly 55 % more than pure CuS (45.5 %). The Au/Ce2S3@CeO2/CuS nanocomposite also showed excellent recyclability (80 % retention after 5 cycles) and a high conversion rate of 222.5 mmol·g−1·h−1.

Silica solubility and molecular speciation in water vapor at 400–800 °C

Silica solubility and molecular speciation in hydrothermal water vapor have been determined through quartz solubility experiments at 400–800 °C and 50–270 bar using a novel U-tube flow-through reactor system and theoretical calculations. The results demonstrate that silica concentrations are low in water vapor (mSi,tot = 0.11–4.56 mmol/kg or xSi,tot = 8.21 × 10−5–1.98 × 10−6 mol/mol) increase with both temperature and pressure, which is attributed to the dissolution of quartz according to the reaction:SiO2(s) + (n + 2)H2O(g) ⇋ Si(OH)4·(H2O)n(g)Thermodynamic modeling and theoretical calculations employing density functional theory (B3LYP-D3), and MP2 ab initio calculations reveal the stable structures to be Si(OH)4(g), Si(OH)4·(H2O)2(g), Si(OH)4·(H2O)4(g) and Si(OH)4·(H2O)7(g) (n = 0, 2, 4, 7) under the temperature and pressure conditions of interest, with higher-order hydrated structures also present at the lowest temperatures and highest pressures. Various isomers of the gaseous silica species were identified, with the number of energetically favorable structures increasing with hydration level and the motifs shifting from silanol-water bonds to complex water-water networks. Over the temperature range of interest, the logarithm of the quartz equilibrium solubility constant (logKn) rises from −7.40 to −6.55 and −12.23 to −11.65 at 400 to 800 °C for the formation of Si(OH)4(g) and Si(OH)4·(H2O)2(g), respectively, and decreases from −16.20 to −19.15 and –22.61 to −28.74 for Si(OH)4·(H2O)4(g) and Si(OH)4·(H2O)7(g) at the same temperature range, respectively. Standard thermodynamic properties were derived based on the experimental results, revealing temperature-independent enthalpy (ΔHn,ro), entropy (ΔSn,ro) and heat capacity (ΔCp,n,ro) of reaction for each gaseous silica species. The enthalpy of the reaction is nearly constant, whereas the entropy and heat capacity decrease with increasing hydration, resulting in higher-level hydrated species becoming less important with increasing temperature. Our quartz solubility results are in good agreement with previous experimental data and thermodynamic equations, as well as the thermodynamic properties of Si(OH)4(g) at 25 °C and 1 bar.

Coprecipitation of Ce(III) oxide with UO2.

The neutralization of acidic solutions containing U (IV) and Ce (III) at room temperature in glove box atmosphere and in the presence of dithionite results in coprecipitation of these elements as amorphous solid solutions CexU1-xO2±y. The solubilities of the precipitates with different mole fractions (x) of Ce(OH)3 (x = 0.01 or 0.1) were determined in 1 M NaClO4 solutions between pH 2.2 and 12.8 under reducing conditions. The solids were investigated by a variety of methods (chemical analysis, SEM-EDX, XRD, XPS, XAS) to determine the nature of the solid solutions formed, their composition and the valence state of Ce and U. X-ray photoelectron spectroscopy confirmed the oxidation states of the solids both before and after the equilibration as Ce (III) and U (IV). The amorphous coprecipitates reached equilibrium relatively fast (∼1 week). The release of Ce from the coprecipitates was totally dominated by the release of uranium over the whole pH range. The Ce concentrations decrease slightly with the decrease of Ce content in the solid, suggesting that CexU1-xO2±y solids behave thermodynamically as solid solutions. The concentrations of U in equilibrium with the coprecipitate were in excellent agreement with the solubility of UO2(s) under reducing conditions reported in the literature. The conditional solubility product of Ce(OH)3 from the coprecipitate was several orders of magnitude (∼4 in the near neutral pH range and ∼18 in the acidic range) lower than that of pure Ce(OH)3(s). The activities and activity coefficients of Ce(OH)3(s) in the coprecipitate were also estimated. Activity coefficients are much less than 1, indicating that the mixing of Ce(OH)3 with UO2 is highly favorable.

Electrospun Amorphous Solid Dispersions with Lopinavir and Ritonavir for Improved Solubility and Dissolution Rate.

Lopinavir (LPV) and ritonavir (RTV) are two of the essential antiretroviral active pharmaceutical ingredients (APIs) characterized by poor solubility. Hence, attempts have been made to improve both their solubility and dissolution rate. One of the most effective approaches used for this purpose is to prepare amorphous solid dispersions (ASDs). To our best knowledge, this is the first attempt aimed at developing ASDs via the electrospinning technique in the form of fibers containing LPV and RTV. In particular, the impact of the various polymeric carriers, i.e., Kollidon K30 (PVP), Kollidon VA64 (KVA), and Eudragit® E100 (E100), as well as the drug content as a result of the LPV and RTV amorphization were investigated. The characterization of the electrospun fibers included microscopic, DSC, and XRD analyses, the assessment of their wettability, and equilibrium solubility and dissolution studies. The application of the electrospinning process led to the full amorphization of both the APIs, regardless of the drug content and the type of polymer matrix used. The utilization of E100 as a polymeric carrier for LPV and KVA for RTV, despite the beads-on-string morphology, had a favorable impact on the equilibrium solubility and dissolution rate. The results showed that the electrospinning method can be successfully used to manufacture ASDs with poorly soluble APIs.

Ultrasonic-assisted electrochemical strategy for ITO scraps recovery through anodic dissolution

The conversion of ITO scraps into oxide powders that can be employed to prepare targets is integral to the closed-loop utilization of scare metal indium. Herein, we present a novel route for electrochemical coupled ultrasonic recovery of ITO scraps, which averts the consumption of strong acids, alkalis and carbon containing reducing agents in traditional hydrometallurgical or pyrometallurgical recovery processes. In an ammonium salt solution, the ITO anode dissolves under the action of electrons: oxygen ions are oxidized, while metal ions are leached out, and then combines with hydroxide ions in the solution to form flocculent precipitates, which is attributed to the extremely low solubility product of indium hydroxide and tin hydroxide. The ultrasonic field can promote the mass transfer between the electrode and electrolyte interface, thereby accelerating the reaction process regulating the morphology and size of the product. After calcination, the precipitates become uniformly mixed nano-scale oxide powders with dimensions that meet the requirements for target preparation. The recycling strategy, with its green, straightforward operation, and feasible for scale-up, suggests potential industrial uses for recovering ITO scraps.

Preformulation Studies of Pitavastatin Calcium– A Primary Step in Further Design of Chronotherapeutic Formulation Synchronized with Circadian Rhythm.

The principal goal and objective of this present research work were to perform a preformulation analysis of Pitavastatin calcium to produce a further stable, efficient chroomodulated drug delivery system. Pitavastatin calcium was analyzed to study its micrometric properties, equilibrium solubility profile in different media, and determination of purity by subjecting to fouriertransform infrared spectroscopy (FTIR) studies, by determining the absorption maxima in the medium along with differential scanning Calorimetry- DSC. Spectral analysis of UV studies and calibration curve plotting was done for further analytical research. The melting point was analyzed, and PXRD studies were conducted to identify the crystallinity. The Pitavastatin calcium micromeritic properties were found to be good with bulk density- 0.408 g/mL, tapped density 0.476 g/mL, Carr’s index 14.2%, Hausner’s ratio 1.16 with 32.0050 angle of repose. The equilibrium solubility study indicates drug has peak solubility in media 0.1 N Hcl and reduced solubility in distilled water. The infrared spectrum indicated peaks corresponding to functional groups conforming to the purity. The UV spectrum exhibited absorption maxima at 250 nm in media 0.1N HCl and 245 in pH phosphate buffer 6.8 and in all other mediums, which is the same as the standard literature indication. The calibration curve exhibited linearity in accordance with Beer Lambert’s law. The PXRD studies produced 2θ values corresponding to pitavastatin calcium as per literature conforming to the crystallinity. The Preformulation analysis concludes that the drug was pure pitavastatin calcium with corresponding absorption maxima, an infrared spectral functional group with crystallinity. It specifies that the drug mandates the improvement of solubility for further formulation development.

Effects of solute alloying elements on solid solubility of TiC in austenite

Solute elements in microalloying steel affect the solid solubility of microalloying elements, and thus affect the second phase precipitation in steels. In this work, the influences of solid solution elements, especially Si and Al, on the solubility product of TiC in austenite were studied using the two-sublattice model. The results show that both Al and Si additions reduced the solubility product of TiC in the austenite region, and the reduction degree of TiC solubility product with Al addition was increased with increasing temperature, while it was decreased with Si addition. In addition, Mn, Mo and Cr additions all increased the solubility product of TiC in the austenite region, and the increment degree of TiC solubility product with Mo addition was decreased with increasing temperature, while it changed slightly with Mn or Cr addition with temperature. The model of solubility product of TiC without alloying additions in austenite was modified, and the calculating result was highly consistent with findings of literatures. Finally, a calculation model of TiC solubility product considering the influence of alloying elements was established.

Predicting CO2 equilibrium solubility in various amine-CO2 systems using an artificial neural network model

Three proposed reaction mechanisms can occur in an amine-CO2 system: either zwitterionic or termolecular mechanisms for primary/secondary amines and base-catalyzed hydration for tertiary amines. The intricacy of this system hinders the construction of a general model for all types of amines. This study attempts to build an artificial neural network model that predicts the equilibrium solubility of any nonblended aqueous amine-CO2 system under given operating conditions, regardless of the reaction mechanism. This is a novel approach that has not yet been reported. The amines were characterized using molecular descriptors derived from COSMO theory through density functional theory calculations to incorporate molecular structures as model features. Our model achieved performance metrics (R2) of 0.9645 and 0.9481 for the training and validation sets, respectively. For unfamiliar amines that were absent in both the training and validation sets, our model achieved an R2 of 0.8601. Model benchmarking was performed using a previously established thermodynamic model. Interpretations of the model are also provided based on the chosen features. This study also offers exploratory insight into how the molecular structure and operating conditions affect the CO2 equilibrium solubility in amines. The model developed in this study has the potential to reduce the solvent screening time in determining appropriate amines for larger-scale applications.

Exploring Co-Amorphous Formulations Of Nevirapine: Insights From Computational, Thermal, And Solubility Analyses.

This study aimed to assess the formation of nevirapine (NVP) co-amorphs systems (CAM) with different co-formers (lamivudine-3TC, citric acid-CAc, and urea) through combined screening techniques as computational and thermal studies, solubility studies; in addition to develop and characterize suitable NVP-CAM. NVP-CAM were obtained using the quench-cooling method, and characterized by differential scanning calorimetry (DSC), X-ray diffractometry (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and polarized light microscopy (PLM), in addition to in vitro dissolution in pH 6.8. The screening results indicated intermolecular interactions occurring between NVP and 3TC; NVP and CAc, where shifts in the melting temperature of NVP were verified. The presence of CAc impacted the NVP equilibrium solubility, due to hydrogen bonds. DSC thermograms evidenced the reduction and shifting of the endothermic peaks of NVP in the presence of its co-formers, suggesting partial miscibility of the compounds. Amorphization was proven by XRD and PLM assays. In vitro dissolution study exhibited a significant increase in solubility and dissolution efficiency of NVP-CAM compared to free NVP. Combined use of screening studies was useful for the development of stable and amorphous NVP-CAM, with increased NVP solubility, making CAM promising systems for combined antiretroviral therapy.

Oral viscous budesonide solution for enhanced localized treatment of eosinophilic esophagitis through improved mucoadhesion and permeation

Eosinophilic esophagitis (EoE) is a chronic inflammatory disease of the esophagus that is immune/antigen-mediated and often requires targeted treatment. In clinical practice, an oral viscous budesonide suspension prepared by adding sucralose to a budesonide suspension for inhalation (Pulmicort®) is used to treat adult EoE and enhance retention in the esophageal mucosa. Inspired by this off-label drug use, oral viscous budesonide solutions (OVBSs) were developed in this study, and their capacities for adhesion, permeation, and stability were explored. Given the insolubility of budesonide as a BCS II drug, we first evaluated its equilibrium solubility and found that Transcutol® HP was an excellent choice for creating an OVBS at a concentration of 0.2 mg/g. The rheological properties of the OVBSs were evaluated with a rheometer, and shear-thinning, which aids in swallowing, was observed. The addition of hydroxyethyl cellulose (HEC) increased the adhesion strength of the preparation, which was associated with the hydration and thickening mechanism. This result was confirmed in a dynamic gelation study and in vitro elution experiment conducted with porcine esophagus tissue. Furthermore, the permeabilities of the OVBSs in the porcine esophagus were evaluated with a Franz diffusion cell device. >80 % of the budesonide was released after 24 h, and the release profile was similar to that of the solution. To explore the storage conditions of OVBSs, critical factors such as pH, content, and impurities were determined. It was found that OVBSs exhibited different behaviors at different pH values and temperatures. Notably, the OVBSs containing 1.7 % HEC could be stored for >6 months at a temperature of 5 °C ± 3 °C and a pH of 4.5 without significant degradation. Overall, this study demonstrated that OVBSs have the potential to adhere to the esophageal mucosa, permeate the tissue, and remain stable during storage. Moreover, OVBSs exhibit a distinct advantage over traditional converted inhalation-to-oral budesonide therapies by enabling flexible dose adjustment in clinical applications, thereby potentially minimizing systemic side effects commonly associated with oral glucocorticoid administration.

A unifying approach to drug-in-polymer solubility prediction: Streamlining experimental workflow and analysis

This method paper describes currently used experimental methods to predict the drug-in-polymer solubility of amorphous solid dispersions and offers a combined approach for applying the Melting-point-depression method, the Recrystallization method, and the Melting-and-mixing method. It aims to describe and expand on the theoretical basis as well as the analytical methodology of the recently published Melting-and-mixing method. This solubility method relies on determining the relationship between drug loads and the enthalpy of melting and mixing of a crystalline drug in the presence of an amorphous polymer. This relationship is used to determine the soluble drug load of an amorphous solid dispersion from the recorded enthalpy of melting and mixing of the crystalline drug portion in a drug-polymer sample at equilibrium solubility. Due to the complex analytical methodology of the Melting-and-mixing method, a software solution called the Glass Solution Companion app was developed. Using this new tool, it is possible to calculate the predicted drug-in-polymer solubility and Flory-Huggins interaction parameter from experimental samples, as well as to generate the resulting solubility-temperature curve. This software can be used for calculations for all three experimental methods, which would be useful for comparing the applicability of the methods on a given drug-polymer system. Since it is difficult to predict the suitability of these drug-in-polymer solubility methods for a specific drug-polymer system in silico, some experimental investigation is necessary. By optimizing the experimental protocol, it is possible to collect data for the three experimental methods simultaneously for a specific drug-polymer system. These results can then be readily analyzed using the Glass Solution Companion app to find the most appropriate method for the drug-polymer system, and therefore, the most reliable drug-in-polymer solubility prediction.