Process Analytical Technology Obtained Metastable Zone Width, Nucleation Rate and Solubility of Paracetamol in Isopropanol—Theoretical Analysis

<b>Background:</b> 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 m...

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Main Authors: Mahmoud Ranjbar, Mayank Vashishtha, Gavin Walker, K. Vasanth Kumar
Format: Article
Language:English
Published: MDPI AG 2025-02-01
Series:Pharmaceuticals
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Online Access:https://www.mdpi.com/1424-8247/18/3/314
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author Mahmoud Ranjbar
Mayank Vashishtha
Gavin Walker
K. Vasanth Kumar
author_facet Mahmoud Ranjbar
Mayank Vashishtha
Gavin Walker
K. Vasanth Kumar
author_sort Mahmoud Ranjbar
collection DOAJ
description <b>Background:</b> 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. <b>Methods:</b> 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. <b>Results:</b> 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. <b>Conclusions:</b> 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.
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spelling doaj-art-80cc6d4fe34f4034bab299d03e1040f12025-08-20T01:49:05ZengMDPI AGPharmaceuticals1424-82472025-02-0118331410.3390/ph18030314Process Analytical Technology Obtained Metastable Zone Width, Nucleation Rate and Solubility of Paracetamol in Isopropanol—Theoretical AnalysisMahmoud Ranjbar0Mayank Vashishtha1Gavin Walker2K. Vasanth Kumar3Synthesis and Solid-State Pharmaceutical Centre, Department of Chemical Sciences, Bernal Research Institute, University of Limerick, V94 T9PX Limerick, IrelandSynthesis and Solid-State Pharmaceutical Centre, Department of Chemical Sciences, Bernal Research Institute, University of Limerick, V94 T9PX Limerick, IrelandSynthesis and Solid-State Pharmaceutical Centre, Department of Chemical Sciences, Bernal Research Institute, University of Limerick, V94 T9PX Limerick, IrelandSynthesis and Solid-State Pharmaceutical Centre, Department of Chemical Sciences, Bernal Research Institute, University of Limerick, V94 T9PX Limerick, Ireland<b>Background:</b> 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. <b>Methods:</b> 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. <b>Results:</b> 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. <b>Conclusions:</b> 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.https://www.mdpi.com/1424-8247/18/3/314crystallizationkineticsmetastable zone widthPATthermodynamicsnucleation
spellingShingle Mahmoud Ranjbar
Mayank Vashishtha
Gavin Walker
K. Vasanth Kumar
Process Analytical Technology Obtained Metastable Zone Width, Nucleation Rate and Solubility of Paracetamol in Isopropanol—Theoretical Analysis
Pharmaceuticals
crystallization
kinetics
metastable zone width
PAT
thermodynamics
nucleation
title Process Analytical Technology Obtained Metastable Zone Width, Nucleation Rate and Solubility of Paracetamol in Isopropanol—Theoretical Analysis
title_full Process Analytical Technology Obtained Metastable Zone Width, Nucleation Rate and Solubility of Paracetamol in Isopropanol—Theoretical Analysis
title_fullStr Process Analytical Technology Obtained Metastable Zone Width, Nucleation Rate and Solubility of Paracetamol in Isopropanol—Theoretical Analysis
title_full_unstemmed Process Analytical Technology Obtained Metastable Zone Width, Nucleation Rate and Solubility of Paracetamol in Isopropanol—Theoretical Analysis
title_short Process Analytical Technology Obtained Metastable Zone Width, Nucleation Rate and Solubility of Paracetamol in Isopropanol—Theoretical Analysis
title_sort process analytical technology obtained metastable zone width nucleation rate and solubility of paracetamol in isopropanol theoretical analysis
topic crystallization
kinetics
metastable zone width
PAT
thermodynamics
nucleation
url https://www.mdpi.com/1424-8247/18/3/314
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AT gavinwalker processanalyticaltechnologyobtainedmetastablezonewidthnucleationrateandsolubilityofparacetamolinisopropanoltheoreticalanalysis
AT kvasanthkumar processanalyticaltechnologyobtainedmetastablezonewidthnucleationrateandsolubilityofparacetamolinisopropanoltheoreticalanalysis