Crystallization Of Paracetamol Research Articles

Data‐driven identification of crystallization kinetics

AbstractA novel data‐driven methodology is presented for developing mathematical models for crystallization processes. The data‐driven approach is based on the sparse identification of nonlinear dynamics (SINDy) method, which iterates between a partial least‐squares fit and a sparsity‐promoting step leading to the discovery of sparse interpretable models. The performance of the SINDy methodology is characterized for the identification of crystallization kinetics in a mixed tank operated in a continuous mode, the isothermal crystallization of lysozyme in a batch stirred tank and cooling crystallization of paracetamol. The SINDy method is robust against noise. Good agreement is obtained between the data‐driven model and the data obtained from crystallization experiments. The presented data‐driven approach can be attractive for modeling industrial crystallization processes where process analytical technology tools are available for the measurement of process variables but functional forms of kinetic expressions are unknown.

Revealing Kinetics of Paracetamol Crystallization Using Time-Resolved Raman Spectroscopy, Orthogonal Time-Lapse Photography, and Non-Negative Matrix Factorization (OSANO)

Revealing Kinetics of Paracetamol Crystallization Using Time-Resolved Raman Spectroscopy, Orthogonal Time-Lapse Photography, and Non-Negative Matrix Factorization (OSANO)

Prediction of the Effective Work Function of Aspirin and Paracetamol Crystals by Density Functional Theory-A First-Principles Study.

Crystals of active pharmaceutical ingredients (API) are prone to triboelectric charging due to their dielectric nature. This characteristic, coupled with their typically low density and often large aspect ratio, poses significant challenges in the manufacturing process. The pharmaceutical industry frequently encounters issues during the secondary processing of APIs, such as particle adhesion to walls, clump formation, unreliable flow, and the need for careful handling to mitigate the risk of fire and explosions. These challenges are further intensified by the limited availability of powder quantities for testing, particularly in the early stages of drug development. Therefore, it is highly desirable to develop predictive tools that can assess the triboelectric propensity of APIs. In this study, Density Functional Theory calculations are employed to predict the effective work function of different facets of aspirin and paracetamol crystals, both in a vacuum and in the presence of water molecules on their surfaces. The calculations reveal significant variations in the work function across different facets and materials. Moreover, the adsorption of water molecules induces a shift in the work function. These findings underscore the considerable impact of distinct surface terminations and the presence of molecular water on the calculated effective work function of pharmaceuticals. Consequently, this approach offers a valuable predictive tool for determining the triboelectric propensity of APIs.

Cooling Crystallization of Paracetamol in a Slug-Flow Crystallizer with Silicone Oil as Continuous Phase

Continuous tubular crystallizers that can provide high yield and better control of crystal size would be of great interest to the industrial crystallization process. However, most continuous crystallizer designs face challenges either due to surface fouling or crystal breakage. In this paper, we explore the ability of slug-flow cooling crystallizers to continuously generate acetaminophen crystals using silicone oil as the continuous phase. Each slug acts as a crystallizer, and the crystals formed inside the dispersed phase avoid encrustation. Three crystallizer configurations were studied at a wide range of supersaturation and flow rates. It was found that a narrow crystal size distribution can be achieved at high flow rates and high supersaturation. Additionally, the average crystal size and the crystallization yield increased with supersaturation and residence time. The configuration of the tubular crystallizer was found to influence the crystallization yield by affecting the internal mixing in the slugs. With further studies, slug-flow cooling crystallizer can be developed for continuous crystallization of crystals with a narrow size distribution, polymorphic purity, and good yield.

The Role of Solvent Hydroxyl Functional Groups on the Interaction Energy and Growth of Form I Paracetamol Crystal Facets

The morphology of a crystal grown in a solvent can change depending on the solvent used during the crystallization process. Modification of the morphology of a crystal can be engineered based on information conferred by the functional groups of the facets of interest and the functional groups of the solvent. This study aims to predict the effect of the alcoholic functional group of amyl alcohol, benzyl alcohol, and phenol on the {002}, {011}, and {110} facets of Form I paracetamol. Prediction and simulation studies were carried out using an embedded tool available in Material Studio. The interaction between the solvents (phenol, benzyl alcohol, and amyl alcohol) and the surfaces used in this study revealed that the {011} facet had the most negative nonbonded energy, followed by the {110} and {002} facets. Overall, the nonbonded interactions between the solvents and the facets were dominated by Coulombic interactions, accounting for more than 90% of the energies, which is within the range from −2566 to −3613 kcal/mol. The binding energy for amyl and benzyl alcohols on the facets of the crystal, ranked from the strongest to the weakest, was in the order {002} > {110} > {011}, while for phenol, the rank was {002} > {011} > {110}. This result is in line with the observed crystal morphology of Form I paracetamol crystallized in a polar protic solvent, in which the most favorable solvent binding on the {002} facets delayed the growth of the elongated hexagonal morphology along the c-axis and formed prismatic-like morphology. Using benzyl alcohol as a case study, an assessment of synthon formation on facets {002} and {011} showed that synthon B is an important synthon for the growth of units of these facets, while synthon F is an important building block synthon for the {110} facet.

Anti-solvent crystallization: Particle size distribution with different devices

Particle size distribution (PSD) is one of the critical attributes of crystals. PSD not only influences downstream processes but also controls final product performance in crystallization. In this work, we have used the model system of methanol–water-paracetamol for carrying out anti-solvent crystallization to produce paracetamol crystals. With reference to a base case of anti-solvent crystallization in a stirred tank, we have used three devices connected to the stirred tank with an external loop with full recycling. A peristaltic pump was used to circulate the contents of the stirred tank in an external loop comprising a simple tube, a fluidic oscillator (FO), and a vortex diode (VD). Anti-solvent was introduced at a point lying between the pump and these three devices to understand the influence of these devices on mixing and potential particle breakage. The PSD of crystals obtained with these three devices are compared with that of the base case for one supersaturation ratio (SSR = 1.63). The results indicated the potential of manipulating the PSD of crystals with a strategy of using fluidic devices in an external loop. The overall arrangement can be potentially extended to continuous crystallization.

Crystallization of Form II Paracetamol with the Assistance of Carboxylic Acids toward Batch and Continuous Processes.

Form II paracetamol has captured the interest of researchers due to its improved compressibility. However, its low stability has made it difficult to be produced on a large scale with good reproducibility. In the present study, the selective polymorphic formation of paracetamol was carried out by cooling crystallization with four types of additives: adipic acid, fumaric acid, oxalic acid, and succinic acid. It was found that: (1) the more additives that were added, the higher the probability of forming Form II paracetamol; (2) Form II paracetamol could be induced by seeding the paracetamol aqueous solution with Form II paracetamol and fumaric acid crystals, and not the other three carboxylic acids; (3) a new solution complex of paracetamol–oxalic acid, evidenced by the solubility diagram, was responsible for the selective nucleation of Form II paracetamol in the oxalic acid aqueous solution; and (4) the range of the degree of supersaturation for nucleating Form II paracetamol was extended with the assistance of oxalic acid or fumaric acid. In large-scale crystallization, Form II paracetamol was produced by the continuous crystallization of 44 mg of paracetamol/mL in 50 wt% of fumaric acid aqueous solution with a flow rate of 150 mL/min.

IR spectra of paracetamol

Paracetamol is a very popular medication used to treat pain and fever. IR spectra of paracetamol have been measured for powder crystals. Ab initio calculations of its equilibrium geometry and vibrational spectra were carried out for spectrum interpretation. Differences between the experimental IR spectra of crystalline samples have been analyzed. Variations of molecular structure from the isolated state to molecular crystal were estimated based on the difference between the optimized molecular parameters of free molecules and the experimental bond lengths and angles evaluated for the crystal forms of the title compounds. The role of hydrogen bonds in the structure of molecular crystals of paracetamol is investigated.
 Bangladesh J. Sci. Ind. Res.56(4), 255-262, 2021

Secondary Nucleation by Interparticle Energies. I. Thermodynamics

Secondary nucleation, in the absence of attrition, is known to be dependent on external fields, such as contact forces, shear, or interparticle forces. In this contribution, the thermodynamic effect of the presence of the seed crystal surface on secondary nucleation is derived in the context of the classical nucleation theory. The Gibbs free energy for the formation of a cluster close to a seed crystal is calculated with the addition of interparticle energies, namely, van der Waals attractive forces and Born repulsive forces. This results in the stabilization of a subcritical cluster close to the seed surface that can become a secondary nucleus more easily than under homogeneous nucleation conditions. Far from the seed surface, the developed model is reduced to the homogeneous nucleation described by the classical nucleation theory. The crystallization of paracetamol from an ethanol solution is taken as a case study, and the stabilization effect, given by the presence of interparticle energies, can be observed at different values of supersaturation. Three key indicators have been defined and calculated to describe the intensity of the stabilization effect, two of which, namely, the distance from the seed surface where the stabilization is active and the enhancement factor for supersaturation, are used in Part II of this series to describe the kinetics of secondary nucleation by interparticle energies.

Impact of Impurities on Crystallization and Product Quality: A Case Study with Paracetamol

A thorough, systematic study into the effect that structurally related impurities have on both the process and product quality during the crystallization of an active pharmaceutical ingredient is presented. The presence of acetanilide and metacetamol influences the crystallization and product quality of paracetamol. Where high concentrations of either impurity were present in the crystallization feed, product recovery decreased by up to 15%. Acetanilide is included in the final product through adsorption onto the particle surface in concentrations up to 0.79 mol%, which can be reduced to acceptable levels through product reslurrying. The presence of metacetamol results in much higher concentrations—up to 6.78 mol% in the final product, of which approximately 1 mol% is incorporated into the crystal lattice, resulting in the perturbation of the unit-cell dimensions. The incidental crystallization and subsequent isolation of metastable Form II paracetamol increased product purity in the presence of a low metacetamol concentration. This metastable product converts to stable paracetamol Form I through reslurrying, offering an efficient metacetamol impurity rejection route. The morphology of the product is modified consistently by both impurities. An elongation of the normal prismatic shape is observed, which in the extreme case of high metacetamol contamination results in the isolation of fine, fragile needles. This problematic morphology is also improved by a reslurrying of the crystallization product to give a more equilateral shape. This systematic study of the influence of acetanilide and metacetamol on the crystallization of paracetamol builds a well-rounded picture of the concomitant impact of impurities on the principal quality attributes of a crystallization product.

Optimal Operation of an Oscillatory Flow Crystallizer: Coupling Disturbance and Stability.

In the process of industrial crystallization, it is always difficult to balance the secondary nucleation rate and metastable zone width (MSZW). Herein, we report an experimental and numerical study for the cooling crystallization of paracetamol in an oscillatory flow crystallizer (OFC), finding the optimal operating conditions for balancing the secondary nucleation rate and MSZW. The results show that the MSZW decreases with the increase of oscillation Reynolds number (Reo). Compared to the traditional stirring system, the OFC has an MSZW three times larger than that of the stirring system under a similar power density of consumption. With the numerical simulation, the OFC can produce a stable space environment and instantaneous strong disturbance, which is conducive to the crystallization process. Above all, a high Reo is favorable to produce a sufficient nucleation rate, which may inevitably constrict the MSZW to a certain degree. Then, the optimization strategy of the operating parameter (Reo) in the OFC is proposed.

Continuous crystallization of paracetamol exploiting gas–liquid flow in modular nucleation and growth stages

A modular multiphase flow crystallizer set-up for the continuous crystallization of paracetamol with an in-line nuclei generator has been developed. Gas bubbles are introduced in a capillary to provide heterogeneous nucleation sites and enhance the nucleation rate. Taking advantage of the separate nucleation and growth sections, control over crystal size distribution is achieved without compromising its span. Comparison with batch growth showed smaller crystal sizes as well as narrower span for the continuous growth. Different configurations of the setup were investigated with regard to the presence of the gas in nucleation and growth sections. Reproducible results were only obtained when gas is present both in the nucleation section (as microbubbles) and in the growth section (as gas slugs). Yields of up to 71% were obtained. Taking the growth time and temperature as varying parameters, the mean crystal size could be manipulated.

A straw for paediatrics: How to administer highly dosed, bitter tasting paracetamol granules

Paediatric practice requires various dosing forms that are acceptable for children of different ages and abilities. A straw prefilled with a drug formulation might serve as a dosing form, especially for children and patients with swallowing difficulties. Using a two-step procedure, we developed granulated coated particles of bitter tasting paracetamol that are appropriate for use in a newly developed straw with two valves to assure liquid flow towards the oral cavity. The paracetamol crystals were coated with five different polymers (water-soluble, entero-soluble) to assure the duration of the taste-masking properties for several minutes during sipping of the drug. As none of these polymer coats assured small enough liquid volumes needed to empty the straw (20 mL) or low enough vacuum for easy drug consumption (130 mbar), the coated crystals were granulated with trehalose-erythritol powder mixture. Acceptable results were obtained with these granulated coated paracetamol particles when polyvinyl alcohol/polyethylene glycol graft copolymer (Kollicoat IR) or a mixture of this polymer with polyvinyl alcohol (Kollicoat Protect) were used. Dissolution tests in water and acidic media confirmed the taste-masking functionality of these particles during drinking simulation and immediate release of paracetamol in the stomach (85% in <30 min at pH 1.2, 4.5).

Anharmonic Raman spectra simulation of crystals from deep neural networks

Raman spectroscopy is an effective tool to analyze the structures of various materials as it provides chemical and compositional information. However, the computation demands for Raman spectra are typically significant because quantum perturbation calculations need to be performed beyond ground state calculations. This work introduces a novel route based on deep neural networks (DNNs) and density-functional perturbation theory to access anharmonic Raman spectra for extended systems. Both the dielectric susceptibility and the potential energy surface are trained using DNNs. The ab initio anharmonic vibrational Raman spectra can be reproduced well with machine learning and DNNs. Silicon and paracetamol crystals are used as showcases to demonstrate the computational efficiency.

Tailoring crystal size distributions for product performance, compaction of paracetamol

Paracetamol crystals often exhibit poor compressibility properties, which results in capping issues. The Particle Size Distribution (PSD) of paracetamol was engineered to improve the compressibility of paracetamol crystals. This was accomplished by growing paracetamol crystals in the presence of additives. The active pharmaceutical ingredient Phenacetin and impurity 4-chloroacetanalide were used to modify the crystal properties of paracetamol. In solution, the phenacetin or 4-chloroacetanalide molecules adsorb onto the paracetamol crystal faces selectively (110 or 011) and inhibit the further growth of the paracetamol crystal and consequently, the paracetamol crystal growth is reduced substantially. For controlling the PSD of crystal to improve the compressibility of paracetamol crystals, a set of cooling crystallization experiments in the presence of additive was designed. According to a statistical experimental design, the cooling rate was the most effective parameter. The PSD was reduced when paracetamol crystallized from the controlled crystallization in the presence of less than 3 mol% of both additives. These smaller particles increased almost four-fold the compressibility of paracetamol in comparison to the commercial material. Moreover, tablets were prepared for each formulation using a direct compaction method. The results illustrated that a higher tablet hardness of paracetamol was achieved by tailoring the paracetamol crystal size distribution. In addition, the tablet disintegration time was higher for the formulation with increased hardness. Overall, this work presents the potential use of structurally similar compounds as additives to alter the mechanical properties of an API.

Crystallization of paracetamol from aqueous solutions in a planar oscillatory flow crystallizer: effect of the oscillation conditions on the nucleation kinetics

Nucleation kinetic data is reported for a planar oscillatory flow crystallizer.

Crystallization of paracetamol from mixtures of ethanol and water in a planar oscillatory flow crystallizer: effect of the oscillation conditions on the crystal growth kinetics

Crystal growth kinetic data is reported for a planar oscillatory flow crystallizer.

Nucleation kinetics for primary, secondary and ultrasound-induced paracetamol crystallization

Investigation into the effect of different nucleation mechanisms on the nucleation rate for paracetamol crystallization in stirred microvials.

Capturing Crystal Shape Evolution from Molecular Simulations.

A simple and efficient algorithm for tracking shape evolution of small-molecule organic crystals during molecular simulations is described. It is based on the reconstruction of a crystal surface from molecular coordinates using an alpha-shape triangulation algorithm followed by the DBSCAN clustering of neighboring triangles with similar normal vectors to crystal faces. No information except the unit cell parameters is needed beforehand, enabling the user to automatically detect not only existing but also new forming crystal faces and edges, which is valuable for prediction of growth and dissolution kinetics. The results are demonstrated for aspirin and paracetamol crystals.

Effect of trehalose and melibiose on crystallization of amorphous paracetamol.

This paper investigates the solid-state behavior of two-phase solid dispersions involving small molecules. The effect of two sugars, trehalose and melibiose, on the recrystallization of amorphous paracetamol, and vice versa, was investigated. The solid dispersions were prepared via heating and quench-cooling, and then stored at a temperature of 38.5±0.5°C and relative humidities of 3±1% and 75±1%. X-ray powder diffraction (XRPD) confirmed that the solid dispersions were amorphous, while Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) revealed that the solid dispersions were two-phase systems with drug-rich and excipient-rich regions. XRPD was used to qualitatively and quantitatively study the crystallization of the components, and revealed that, despite the existence of two phases, the sugars hindered the crystallization of paracetamol. In contrast, once the paracetamol crystallization started, it accelerated the crystallization of the sugars. Overall, the study demonstrates that small-molecule solid-dispersions need not be single-phase to observe mutual influences between the components in crystallization behavior, and that these effects are likely mediated through interactions at the phase interfaces, as well as alterations in water sorption and mechanical effects.