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21 pages, 1693 KiB  
Article
Process Analytical Technology Obtained Metastable Zone Width, Nucleation Rate and Solubility of Paracetamol in Isopropanol—Theoretical Analysis
by Mahmoud Ranjbar, Mayank Vashishtha, Gavin Walker and K. Vasanth Kumar
Pharmaceuticals 2025, 18(3), 314; https://doi.org/10.3390/ph18030314 - 24 Feb 2025
Cited by 2 | Viewed by 941
Abstract
Background: Metastable zone width (MSZW) and solubility are crucial for developing crystallization procedures in the purification of active pharmaceutical ingredients (APIs). Traditionally, determining these properties involves labor-intensive methods that can take weeks or even months. With advancements in process analytical technologies (PAT) and [...] Read more.
Background: Metastable zone width (MSZW) and solubility are crucial for developing crystallization procedures in the purification of active pharmaceutical ingredients (APIs). Traditionally, determining these properties involves labor-intensive methods that can take weeks or even months. With advancements in process analytical technologies (PAT) and the increasing focus on quality by design (QbD) in pharmaceutical manufacturing, more efficient and reliable protocols are needed. In this study, we employ in situ Fourier Transform Infrared (FTIR) spectroscopy and Focused Beam Reflectance Measurement (FBRM) to establish protocols for measuring solubility at different temperatures and MSZW at varying cooling rates. Methods: We experimentally determined MSZW and solubility using FTIR spectroscopy and FBRM. IR spectra were analyzed to obtain solubility concentrations, while FBRM counts were used to extract MSZW and supersolubility concentrations. The collected data were assessed using four theoretical models, including a newly developed model based on classical nucleation theory. By fitting experimental MSZW data to these models, we determined nucleation kinetics and thermodynamic parameters. Results: Our novel model exhibited excellent agreement with experimental MSZW data across different cooling rates, demonstrating its robustness. The nucleation rate constant and nucleation rate ranged between 10²¹ and 10²² molecules/m³·s. The Gibbs free energy of nucleation was calculated as 3.6 kJ/mol, with surface energy values between 2.6 and 8.8 mJ/m². The estimated critical nucleus radius was in the order of 10⁻³ m. Conclusions: The protocols we developed for predicting MSZW and solubility of paracetamol using PAT can serve as a guideline for other APIs. Our theoretical model enhances the predictive accuracy of nucleation kinetics and thermodynamics, contributing to optimized crystallization processes. Full article
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14 pages, 1945 KiB  
Article
Nucleation Kinetics of Rare Earth Scandium Salt: An Experimental Investigation of the Metastable Zone Width
by Josia Tonn, Aishe Grotjohann, Christian Kocks and Andreas Jupke
Crystals 2023, 13(7), 1074; https://doi.org/10.3390/cryst13071074 - 8 Jul 2023
Cited by 1 | Viewed by 1511
Abstract
Scandium is a rare earth element that has been declared a critical raw material by the EU. Its availability is low but the demand for it is increasing. Bauxite residue presents a possible European source. A novel process to extract scandium from the [...] Read more.
Scandium is a rare earth element that has been declared a critical raw material by the EU. Its availability is low but the demand for it is increasing. Bauxite residue presents a possible European source. A novel process to extract scandium from the residue incorporates anti-solvent crystallization, which delivers the scandium salt (NH4)3ScF6 that can be calcined to ScF3 for direct use in an aluminum alloy. However, this crystallization process produces small crystals in the single-digit micrometer scale, hindering solid–liquid separation. In order to facilitate the separation, the crystallization process needs to be better understood and controlled. Therefore, nucleation kinetics are investigated by measuring the metastable zone width (MSZW) with an optical endoscope probe inside a 300 mL stirred fed-batch crystallizer with varying operating parameters. To study the influence of mixing on the MSZW, the stirring rate, the antisolvent addition rate, and the dilution of the antisolvent before injection are varied. The latter is proven to widen the MSZW by a multiple. It could be confirmed that mixing times on different scales greatly influence the MSZW and the growth of the crystals in the process. With these results, the boundaries for operating parameters are studied in order to control the crystallization process and thus crystal growth. Full article
(This article belongs to the Special Issue Aggregation, Nucleation and Crystallization)
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17 pages, 7891 KiB  
Article
Effect of Solvent Composition on Solubility, Thermodynamics, Metastable Zone Width (MSZW) and Crystal Habit of L-Ascorbic Acid
by Jyoti Yadav, Dan G. Dumitrescu, Thomas Kendall, Carmen Guguta and Swati A. Patel
Crystals 2022, 12(12), 1798; https://doi.org/10.3390/cryst12121798 - 9 Dec 2022
Cited by 3 | Viewed by 4151
Abstract
This work investigates the effect of different solvent systems on solubility, thermodynamics, metastable zone width (MSZW), and crystal habit of ascorbic acid, in order to help optimize its crystallization process. The solubility curves and metastable zone (MSZ) limits were determined experimentally using the [...] Read more.
This work investigates the effect of different solvent systems on solubility, thermodynamics, metastable zone width (MSZW), and crystal habit of ascorbic acid, in order to help optimize its crystallization process. The solubility curves and metastable zone (MSZ) limits were determined experimentally using the polythermal method in pure solvents: water and alcohols (methanol/ethanol/isopropanol), as well as water-alcohol binary solvent systems. The solubility decreases with increasing alcohol composition for all solvent systems. The solubility data were well correlated using the Jouyban–Acree model as a function of two variables: temperature and solvent composition. The dissolution enthalpy (ΔHdiss), dissolution entropy (ΔSdiss), and Gibbs free energy (ΔGdiss) were determined using Van’t Hoff and Jouyban–Acree models. The thermodynamic properties increase with increasing alcohol composition. The lowest and highest values of enthalpy were obtained for water (20.52 kJ mol 1) and isopropanol (35.33 kJ mol1), respectively. Pure alcohols as solvents widen the metastable zone width, indicating high supersaturation required for the nucleation. Crystal images captured during cooling crystallization in water confirm the cubic crystal habit formation, whereas increasing alcohol composition in the solvent system promotes preferential growth along one crystallographic axis, leading to elongated prism-shaped crystals in methanol and ethanol and needle-shaped crystals in isopropanol. Full article
(This article belongs to the Section Industrial Crystallization)
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18 pages, 24854 KiB  
Article
Insight into the Nucleation Mechanism of p-Methoxybenzoic Acid in Ethanol-Water System from Metastable Zone Width
by Guangle Wang, Zeren Shang, Mingdi Liu, Weibing Dong, Haichao Li, Haiqing Yin, Junbo Gong and Songgu Wu
Molecules 2022, 27(13), 4085; https://doi.org/10.3390/molecules27134085 - 24 Jun 2022
Cited by 5 | Viewed by 2136
Abstract
The metastable zone width (MSZW) of p-methoxybenzoic acid (PMBA) in an ethanol-water system was measured using the polythermal method. The nucleation order m obtained by the Nývlt’s model indicates the nucleation of PMBA following a progressive nucleation mechanism at low saturation temperature [...] Read more.
The metastable zone width (MSZW) of p-methoxybenzoic acid (PMBA) in an ethanol-water system was measured using the polythermal method. The nucleation order m obtained by the Nývlt’s model indicates the nucleation of PMBA following a progressive nucleation mechanism at low saturation temperature (m = 3.18–7.50) and an instantaneous nucleation mechanism at high saturation temperature (m = 1.46–2.55). Then, combined with the metastable zone experiment and the Sangwal model, we found that the MSZW and the interfacial energy reached the maximum when the mass fraction of ethanol was 0.8, which resulted in the smallest crystal product size. Meanwhile, the maximum rcrit and ΔGcrit obtained based on the modified Sangwal model indicating the PMBA needs to overcome a higher nucleation barrier in the ethanol mass fraction of 0.8. Finally, we proposed a preferential strategy for adjusting MSZW by correlating the interfacial energy with the change in ethanol mass fraction, saturation temperature, and cooling rate, respectively. Full article
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10 pages, 1115 KiB  
Article
Comparison of the Nucleation Kinetics Obtained from the Cumulative Distributions of the Metastable Zone Width and Induction Time Data
by Lie-Ding Shiau
Molecules 2022, 27(9), 3007; https://doi.org/10.3390/molecules27093007 - 7 May 2022
Cited by 3 | Viewed by 2023
Abstract
A linearized integral model based on classical nucleation theory is applied in this work to determine the interfacial energy and pre-exponential factor using a linear plot from the cumulative distributions of the metastable zone width (MSZW) data for some systems reported in the [...] Read more.
A linearized integral model based on classical nucleation theory is applied in this work to determine the interfacial energy and pre-exponential factor using a linear plot from the cumulative distributions of the metastable zone width (MSZW) data for some systems reported in the literature, including isonicotinamide, butyl paraben, dicyandiamide, and salicylic acid. Based on the same criterion for the nucleation point, the interfacial energy and pre-exponential factor are determined using the conventional linear regression method from the cumulative distributions of the induction time data for the same systems. The results indicate that the interfacial energy and pre-exponential factor calculated from the MSZW data are consistent with those calculated from the induction time for the studied systems. Full article
(This article belongs to the Section Physical Chemistry)
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17 pages, 3425 KiB  
Article
Nucleation Behaviors of Adipic Acid in Different Polarity Solvent Based on Metastable Zone Width
by Yanfei Wang, Xiaoyu Chuai, Yifei Li, Jia Guo, Jing Yang, Zhixue Liu and Shijie Xu
Crystals 2022, 12(2), 202; https://doi.org/10.3390/cryst12020202 - 29 Jan 2022
Cited by 4 | Viewed by 3125
Abstract
In this contribution, we experimentally determined the metastable zone width (MSZW) of adipic acid (AA) in different polar solvents to reveal the nucleation behavior. We performed analyses for different cooling rates, saturation temperatures and polar solvents. The findings showed that the MSZW increased [...] Read more.
In this contribution, we experimentally determined the metastable zone width (MSZW) of adipic acid (AA) in different polar solvents to reveal the nucleation behavior. We performed analyses for different cooling rates, saturation temperatures and polar solvents. The findings showed that the MSZW increased as the cooling rate increased, or saturation temperature or polarity decreased. Here, we suggest that the hydrogen bond donor capacity decreases as the polarity of the solvent decreases, which weakens the solute and solvent interaction and makes the desolvation process more difficult during nucleation. Furthermore, we found that the MSZW is mainly determined by the cooling rate, when the cooling rate is large enough. On account of the classical nucleation theory, it was found that the sizes of the critical nucleus and Gibbs nucleation energy do not increase monotonously with increasing driving force. Moreover, this study confirms that solid–liquid interface tension is associated with crystallization driving force. Full article
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12 pages, 3397 KiB  
Article
Comparison of the Nucleation Parameters of Aqueous l-glycine Solutions in the Presence of l-arginine from Induction Time and Metastable-Zone-Width Data
by Lie-Ding Shiau
Crystals 2021, 11(10), 1226; https://doi.org/10.3390/cryst11101226 - 12 Oct 2021
Cited by 4 | Viewed by 2096
Abstract
Induction time and metastable-zone-width (MSZW) data for aqueous l-glycine solutions in the presence of l-arginine impurity were experimentally measured using a turbidity probe in this study. The nucleation parameters, including the interfacial free energy and pre-exponential nucleation factor, obtained from induction [...] Read more.
Induction time and metastable-zone-width (MSZW) data for aqueous l-glycine solutions in the presence of l-arginine impurity were experimentally measured using a turbidity probe in this study. The nucleation parameters, including the interfacial free energy and pre-exponential nucleation factor, obtained from induction time data, were compared with those obtained from MSZW data. The influences of lag time on the nucleation parameters were examined for the induction time data. The effects of l-arginine impurity concentration on the nucleation parameters based on both the induction time and MSZW data were investigated in detail. Full article
(This article belongs to the Special Issue Recent Progress in Industrial Crystallization)
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13 pages, 1587 KiB  
Article
Determination of the Metastable Zone Width and Nucleation Parameters of Succinic Acid for Electrochemically Induced Crystallization
by Christian Kocks, Christina Maria Krekel, Marcel Gausmann and Andreas Jupke
Crystals 2021, 11(9), 1090; https://doi.org/10.3390/cryst11091090 - 7 Sep 2021
Cited by 10 | Viewed by 5679
Abstract
Electrified downstream processes for biotechnologically produced carboxylic acids reduce waste salt generation significantly and make biotechnological production ecologically and economically more attractive. In order to design, optimize, scale-up and control electrochemically induced crystallization processes, knowledge of the metastable zone width (MSZW) is essential. [...] Read more.
Electrified downstream processes for biotechnologically produced carboxylic acids reduce waste salt generation significantly and make biotechnological production ecologically and economically more attractive. In order to design, optimize, scale-up and control electrochemically induced crystallization processes, knowledge of the metastable zone width (MSZW) is essential. An optical observation approach of nucleation processes close to the electrode and determination of the MSZW is presented. This work presents a method for MSZW measurements for electrochemically induced pH-shift crystallization processes by monitoring the nucleation, the saturation pH value and saturation concentration for different current densities. The measured MSZWs for electrochemically induced pH-shift crystallization are narrow due to the foreign surface, gas bubbles and electrode surface, and rising current densities lead to even smaller MSZW. Nucleation parameters are estimated from MSWZ data, adapting the classical approach of Nývlt to electrochemically induced crystallization. Full article
(This article belongs to the Special Issue Crystal Nucleation and Growth Kinetics)
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20 pages, 3797 KiB  
Article
Electric-Potential-Assisted Crystallisation of L-Isoleucine: A Study of Nucleation Kinetics and Its Associated Parameters
by Nik Salwani Md Azmi, Nornizar Anuar, Muhamad Fitri Othman, Noor Fitrah Abu Bakar and Mohd Nazli Naim
Crystals 2021, 11(6), 620; https://doi.org/10.3390/cryst11060620 - 31 May 2021
Cited by 3 | Viewed by 3008
Abstract
The potential of producing L-isoleucine crystals with the aid of electric potential and its effect on the nucleation kinetics of L-isoleucine were probed using polythermal and isothermal crystallisation techniques, assisted with 5 V, 9 V, and 20 V electric potentials. The polythermal experiments [...] Read more.
The potential of producing L-isoleucine crystals with the aid of electric potential and its effect on the nucleation kinetics of L-isoleucine were probed using polythermal and isothermal crystallisation techniques, assisted with 5 V, 9 V, and 20 V electric potentials. The polythermal experiments were conducted with cooling rates of 0.1 °C/min–0.7 °C/min, whilst isothermal crystallisation was conducted with a supersaturation of 1.30–1.70, and both were carried out in a 200 mL temperature-controlled jacketed reactor. Prediction of the nucleation rate and its associated parameters for isothermal crystallisation was carried out using a molecular dynamics simulation. In both crystallisation techniques, electric potentials increased the nucleation rate, but the intensity of the electric potential had less impact on the measured parameters. Nucleation rates for 5 V isothermal crystallisation were in the order of 1010 higher than for polythermal crystallisation. Electric potential doubled the nucleation rates for polythermal crystallisation and increased the nucleation rates 12-fold in isothermal crystallisation. The isothermal technique produced the form B polymorph, but mixtures of forms A and B were produced in polythermal crystallisation. The predicted critical number of molecules, N*, and the critical radius, r*, were in good agreement with the experimental data, with a higher predicted nucleation rate in the order of 102. Full article
(This article belongs to the Special Issue Crystallization Processes: Food and Pharmaceutical Crystals)
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13 pages, 1340 KiB  
Article
Effects of Anion Impurities on the Solubility and Nucleation of Borax Decahydrate Crystals in Carbonate-Type Brine
by Jing Chen, Jiaoyu Peng, Xingpeng Wang, Yaping Dong and Wu Li
Crystals 2019, 9(6), 304; https://doi.org/10.3390/cryst9060304 - 13 Jun 2019
Cited by 10 | Viewed by 4728
Abstract
Measurements of the solubility and metastable zone width (MSZW) of borax decahydrate (disodium tetraborate decahydrate) within chloride, sulfate and carbonate solutions were carried out. The MSZW was measured by the conventional polythermal method with turbidity technology. The results showed that the addition of [...] Read more.
Measurements of the solubility and metastable zone width (MSZW) of borax decahydrate (disodium tetraborate decahydrate) within chloride, sulfate and carbonate solutions were carried out. The MSZW was measured by the conventional polythermal method with turbidity technology. The results showed that the addition of impurities decreased solubility. The main factor reducing solubility is the common ion effect, but the salt effect is also significant in the complex system. The addition of impurities broadened the MSZW. The MSZW was wider at first, then decreased with the addition of NaCl, yet the MSZW widened with the addition of Na2SO4 within the concentration range studied. This can be explained by adsorption and diffusion. The data of solubility and MSZW were analyzed by applying the Van’t Hoff equation and the classical 3D nucleation theory approach, respectively. By calculating the corresponding parameters, the experimental phenomena are further explained from the perspective of thermodynamics and dynamics. Full article
(This article belongs to the Section Crystal Engineering)
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