Quality-by-design (QbD): an integrated approach for evaluation of powder blending process kinetics and determination of powder blending end-point

Evaluation and Analysis of Cement Raw Meal Homogenization Characteristics Based on Simulated Equipment Models

In recent years, the variability in the composition of cement raw materials has increasingly impacted the quality of cement products. However, there has been relatively little research on the homogenization effects of equipment in the cement production process. Existing studies mainly focus on the primary functions of equipment, such as the grinding efficiency of ball mills, the thermal decomposition in cyclone preheaters, and the thermal decomposition in rotary kilns. This study selected four typical pieces of equipment with significant homogenization functions for an in-depth investigation: ball mills, pneumatic homogenizing silos, cyclone preheaters, and rotary kilns. To assess the homogenization efficacy of each apparatus, scaled-down models of these devices were constructed and subjected to simulated experiments. To improve experimental efficiency and realistically simulate actual production conditions in a laboratory setting, this study used the uniformity of the electrical capacitance of mixed powders instead of compositional uniformity to analyze homogenization effects. The test material in the experiment consisted of a mixture of raw meal from a cement factory with a high dielectric constant and Fe3O4 powder. The parallel plate capacitance method was employed to ascertain the capacitance value of the mixed powder prior to and subsequent to treatment by each equipment model. The fluctuation of the input and output curves was analyzed, and the standard deviation (S), coefficient of variation (R), and homogenization multiplier (H) were calculated in order to evaluate the homogenization effect of each equipment model on the raw meal. The findings of the study indicated that the pneumatic homogenizer exhibited an exemplary homogenization effect, followed by the ball mill. For the ball mill, a higher proportion of small balls in the gradation can significantly enhance the homogenization effect without considering the grinding efficiency. The five-stage cyclone preheater also has a better homogenization effect, while the rotary kiln has a less significant homogenization effect on raw meal. Finally, the raw meal processed by each equipment model was used for clinker calcination and the preparation of cement mortar samples. After curing for three days, the compressive and flexural strengths of the samples were tested, thereby indirectly verifying the homogenization effect of each equipment model on the raw meal. This study helps to understand the homogenization process of raw materials by equipment in cement production and provides certain reference and data support for equipment selection, operation optimization, and quality control in the cement production process.

Supply Chain Design for Blending Technologies

When optimizing blending technologies, the main objective is to determine the right mixing ratio of the raw materials, depending on the different qualities and costs of the raw materials available. It can be concluded that research is mainly focused on answering technological questions, and only very few studies take into account the logistics processes related to blending technologies, their design, cost-efficiency, utilization and sustainability including energy efficiency and environmental impact. Based on this fact, within the frame of this research the authors describe a new approach, extending the basic model of blending problems by adding new supply chain efficiency-related components that makes it possible to take logistics parameters related to the raw materials supply (available stocks, batch sizes, transport and storage costs, supply chain structure) into consideration. A mathematical model of this supply chain optimization problem for blending technologies is described including routing and assignment problems in the supply chain, while technological objectives are also taken into consideration as technological objective functions and constraints. The optimization problem described in the model is a problem with non-deterministic polynomial-time hardness (NP-hard), which means that there are no known efficient analytical methods to solve the logistics-related supply chain optimization of blending technologies. As a solution algorithm, the authors have used an evolutive solver and a new metrics, which improved the efficiency of the comparison of distances between solutions of routing problems represented by permutation arrays. The scenario analysis, which focuses on the integrated optimization of technological and logistics problems validates the model and evaluates the solution algorithm and the new metrics. Using the mentioned algorithm, the supply chain processes of the blending technologies can be improved from availability, efficiency, sustainability point of view.

Dry Powder Mixing Is Feasible in Continuous Twin Screw Extruder: Towards Lean Extrusion Process for Oral Solid Dosage Manufacturing

Using discrete element method (DEM) modeling and near-infrared (NIR) spectroscopy, the feasibility of powder mixing in the initial pre-melting zones of a twin screw extruder using two independent feeders was studied. Previous work in the pharmaceutical and food industry has focused on mixing when materials are melted or on material homogeneity at the extruder's output. Depending on the formulation, ensuring a fully blended formulation prior to melting may be desired. Experiments were conducted using a Coperion ZSK-18 extruder to evaluate if blend uniformity can be achieved by exploring screw configuration, screw speed, and powder feed rate. As powder exited the extruder and deposited on a conveyor belt, an in-line NIR spectrophotometer measured spectra of material. Chemometric-based models predicted unknown concentrations to evaluate if blend uniformity was achieved. Using the EDEM software, Hertz-Mindlin contact model, and dimensions of the extruder, DEM simulations complemented the experimental work. The DEM computational models provided understanding of mixing patterns inside the extruder at particle scale and helped select the screw configuration before doing experimentation. The simulations showed good axial mixing for all the screw configurations studied, while good cross (radial) mixing was only observed for the screw configuration with 90-degree kneading elements. Therefore, the screw configuration with two 90-degree kneading elements was chosen for the experimental study. The RTD profiles when using a screw configuration with only conveying screw elements are comparable to a plug flow reactor (PFR), while the profiles when using kneading elements are more comparable to an ideal continuous stirred tank reactor (CSTR). For the screw configuration with 90 degrees kneading elements, the mean residence time (MRT) decreases with an increase in the screw speed. Experimental NIR spectra showed that concentrations can be predicted with an error of 2%. It was demonstrated that the twin screw extruder can provide proper dry powder mixing of two powder feed streams based on a unit dose scale, enabling continuous powder mixing prior to the melting zone in the extruder for the formulation studied with a cohesive API. This setup may also work for other types of formulations. These studies can help in developing lean hot melt as well as wet extrusion/granulation processes using twin screw extruders for the continuous manufacturing of oral solid dosage products.

Critical Tools in Tableting Research: Using Compaction Simulator and Quality by Design (QbD) to Evaluate Lubricants' Effect in Direct Compressible Formulation

As commonly known, the product development stage is quite complex, requires intensive knowledge, and is time-consuming. The selection of the excipients with the proper functionality and their corresponding levels is critical to drug product performance. The objective of this study was to apply quality by design (QbD) principles for formulation development and to define the desired product quality profile (QTPP) and critical quality attributes (CQA) of a product. QbD is a risk- and science-based holistic approach for upgraded pharmaceutical development. In this study, Ibuprofen DC 85W was used as a model drug, Cellactose® 80 along with MicroceLac® 100 as a filler, and magnesium stearate, stearic acid, and sodium stearyl fumarate as lubricants. By applying different formulation parameters to the filler and lubricants, the QbD approach furthers the understanding of the effect of critical formulation and process parameters on CQAs and the contribution to the overall quality of the drug product. An experimental design study was conducted to determine the changes of the obtained outputs of the formulations, which were evaluated using the Modde Pro 12.1 statistical computer program that enables optimization by modeling complex relationships. The results of the optimum formulation revealed that MicroceLac® 100 was the superior filler, while magnesium stearate at 1% was the optimum lubricant. A design space that indicates the safety operation limits for the process and formulation variables was also created. This study enriches the understanding of the effect of excipients in formulation and assists in enhancing formulation design using experimental design and mathematical modeling methods in the frame of the QbD approach.

Near infrared analysis of pharmaceutical powders with empirical target distribution optimization (ETDO)

Near infrared (NIR) spectroscopy is a well-established method for analysis of pharmaceutical products, and especially useful for process monitoring and control of continuous production due to high sample throughput. In this work, a previously established method called empirical target distribution optimization (ETDO) wherein reference sample values using information from model prediction of the calibration data was used as a tool to improve the performance of NIR partial least squares (PLS) models. Model performance was assessed using root mean square error (R²), bias and accuracy in prediction of test samples. A target value selection threshold was tested to assess the ETDO procedure for NIR analysis of powder samples. The amount of specific variation captured by the model was examined and compared for models calibrated with and without ETDO. The results reported in this work suggests that PLS models optimized with ETDO of reference values can provide more specific PLS models for NIR analysis for complex powder mixtures. In addition, the model optimization method could also be applied as a tool to verify the necessary amount of PLS components to produce robust models. The ETDO method presented in this work is an approach that could be applied in the development of continuous blending or tableting processes where robust in-line quantitative analysis of powder samples is needed.

Product Development, Manufacturing, and Packaging of Solid Dosage Forms Under QbD and PAT Paradigm: DOE Case Studies for Industrial Applications

An integrated approach based on QbD and PAT provides a systematic and innovative framework for product development, manufacturing, and quality risk management. In this context, the significance of the outcome of design of experiments (DOEs) to the selection of the product design, robust commercial manufacturing process, design space, and overall control strategy remains vital for the success of a drug product throughout its life cycle. This paper aims at discussing selected recent DOE case studies conducted during QbD-based and integrated QbD/PAT-based development of solid oral formulations and process improvement studies. The main focus of this paper is to highlight the rationales and importance of design selection during development and applications of mathematical models and statistical tools in analyzing DOE and PAT data for developing a design space, control strategy, and improved process monitoring. A total of 25 case studies (includes 9 PAT application studies) have been discussed in this paper which cover 11 manufacturing processes commonly utilized for solid dosage forms. Two case studies relevant to selection of packaging design for solid dosage forms are also briefly discussed to complete the scope. Overall, for a successful modern QbD approach, it is highly important that DOEs are conducted and analyzed in a logical sequence which involves designs that are phase-appropriate and quality-driven and facilitate both statistical and chemometric thinking at each development stage. This approach can result into higher regulatory flexibility along with lower economic burden during life cycle of a product, irrespective of regulatory path used (NDA or ANDA).

Development of immediate release Rupatadine fumarate 10 mg tablets: A Quality by Design (QbD) approach

Objective: The main objective of this research is to develop an immediate release Rupatadine fumarate 10 mg tablets formulation by direct compression, through a Quality by Design approach in Costa Rica. Methods: According to a Quality by Design approach; Target Product Profile, Quality Target Product Profile, and the Critical Quality Attributes were defined. In the preformulation study, compatibility tests were carried out between the raw materials. The Critical Material Attributes were established using Quality Risk Management. Three formulation prototypes were prepared by direct compression and its Critical Process Parameters were defined. The analysis of the prototypes was realized in terms of organoleptic properties, identification, potency, content uniformity, dissolution, disintegration, friability and loss by drying. Results: All the prototypes showed a white or slightly pink surface, potency between 90.0 -110.0 % of the labeling, an acceptance value for the content uniformity lower than the specification (AV < 15), the dissolved amount of active pharmaceutical ingredient was greater than 85.0 % at 30 minutes, friability less than 1.0 %, a disintegration time less than 15 minutes and moisture content less than 2.0 %. Conclusions: The approaching of a Quality by Design model to the current development allowed to obtain satisfactory results in the three formulation prototypes. The excipients to be used can be lactose monohydrate, microcrystalline cellulose, sodium croscarmellose, pregelatinized starch, magnesium stearate, stearic acid, and PVP K-30.

Blend uniformity evaluation during continuous mixing in a twin screw granulator by in-line NIR using a moving F-test

This study focuses on the twin screw granulator of a continuous from-powder-to-tablet production line. Whereas powder dosing into the granulation unit is possible from a container of preblended material, a truly continuous process uses several feeders (each one dosing an individual ingredient) and relies on a continuous blending step prior to granulation. The aim of the current study was to investigate the in-line blending capacity of this twin screw granulator, equipped with conveying elements only. The feasibility of in-line NIR (SentroPAT, Sentronic GmbH, Dresden, Germany) spectroscopy for evaluating the blend uniformity of powders after the granulator was tested. Anhydrous theophylline was used as a tracer molecule and was blended with lactose monohydrate. Theophylline and lactose were both fed from a different feeder into the twin screw granulator barrel. Both homogeneous mixtures and mixing experiments with induced errors were investigated. The in-line spectroscopic analyses showed that the twin screw granulator is a useful tool for in-line blending in different conditions. The blend homogeneity was evaluated by means of a novel statistical method being the moving F-test method in which the variance between two blocks of collected NIR spectra is evaluated. The α- and β-error of the moving F-test are controlled by using the appropriate block size of spectra. The moving F-test method showed to be an appropriate calibration and maintenance free method for blend homogeneity evaluation during continuous mixing.

On-line UV-NIR spectroscopy as a process analytical technology (PAT) tool for on-line and real-time monitoring of the extraction process of Coptis Rhizome

UV-NIR spectroscopy connected method as a tool for on-line and real-time monitoring of Coptis Rhizome extraction process.

Monitoring As and Hg variation in An-Gong-Niu-Huang Wan (AGNH) intermediates in a pilot scale blending process using laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) was used to assess the cinnabar and realgar blending of An-Gong-Niu-Huang Wan (AGNH) in a pilot-scale experiment, including the blending end-point. The blending variability of two mineral medicines, cinnabar and realgar, were measured by signal relative intensity changing rate (RICR) and moving window standard deviation (MWSD) based on LIBS. Meanwhile, relative concentration changing rate (RCCR) was obtained based on the reference method involving inductively coupled plasma optical emission spectrometry (ICP-OES). The LIBS result was consistent with ICP-OES at blending end-point determinations of both mineral medicines. Unlike the ICP-OES method, LIBS does not have an elaborate digestion procedure. LIBS is a promising and rapid technique to understand the blending process of Chinese Materia Medica (CMM) containing cinnabar and realgar. These results demonstrate the potential of LIBS in monitoring CMM pharmaceutical production.

Understanding pharmaceutical quality by design

This review further clarifies the concept of pharmaceutical quality by design (QbD) and describes its objectives. QbD elements include the following: (1) a quality target product profile (QTPP) that identifies the critical quality attributes (CQAs) of the drug product; (2) product design and understanding including identification of critical material attributes (CMAs); (3) process design and understanding including identification of critical process parameters (CPPs), linking CMAs and CPPs to CQAs; (4) a control strategy that includes specifications for the drug substance(s), excipient(s), and drug product as well as controls for each step of the manufacturing process; and (5) process capability and continual improvement. QbD tools and studies include prior knowledge, risk assessment, mechanistic models, design of experiments (DoE) and data analysis, and process analytical technology (PAT). As the pharmaceutical industry moves toward the implementation of pharmaceutical QbD, a common terminology, understanding of concepts and expectations are necessary. This understanding will facilitate better communication between those involved in risk-based drug development and drug application review.

Verification of model development technique for NIR-based real-time monitoring of ingredient concentration during blending

There has been a considerable research on the process analytical technology (PAT) and real-time monitoring based on NIR, but the model development is still an important issue and persons in charge have difficulty in building good models. In this study, to realize efficient NIR-based real-time monitoring of ingredient concentration and establish a model development method, we investigated the effect of a calibration set, spectral preprocessing, wavelengths, and other factors on the prediction error through pilot and commercial scale blending experiments. The results confirmed that the small prediction error was realized by a calibration set, including dynamic measurement spectra acquired with the target blender. In addition, the results demonstrated that locally weighted partial least squares (LW-PLS) achieved the smaller prediction error than conventional PLS. The present study has also clarified that spectral preprocessing methods and wavelengths selected to build a model affect the prediction error of ingredient concentration interactively. A wide wavelength range should be selected when the spectral preprocessing does not lessen the effect of baseline variation, while a narrow wavelength range should be selected when it strongly decreases the effect.

Applying terahertz technology for nondestructive detection of crack initiation in a film-coated layer on a swelling tablet

Here, we describe a nondestructive approach using terahertz wave to detect crack initiation in a film-coated layer on a drug tablet. During scale-up and scale-down of the film coating process, differences in film density and gaps between the film-coated layer and the uncoated tablet were generated due to differences in film coating process parameters, such as the tablet-filling rate in the coating machine, spray pressure, and gas-liquid ratio etc. Tablets using the PEO/PEG formulation were employed as uncoated tablets. We found that heat and humidity caused tablets to swell, thereby breaking the film-coated layer. Using our novel approach with terahertz wave nondestructively detect film surface density (FSD) and interface density differences (IDDs) between the film-coated layer and an uncoated tablet. We also found that a reduced FSD and IDD between the film-coated layer and uncoated tablet increased the risk of crack initiation in the film-coated layer, thereby enabling us to nondestructively predict initiation of cracks in the film-coated layer. Using this method, crack initiation can be nondestructively assessed in swelling tablets after the film coating process without conducting accelerated stability tests, and film coating process parameters during scale-up and scale-down studies can be appropriately established.

An integrated Quality by Design (QbD) approach towards design space definition of a blending unit operation by Discrete Element Method (DEM) simulation

A combined Quality by Design (QbD) and Discrete Element Model (DEM) simulation-approach is presented to characterize a blending unit operation by evaluating the impact of formulation parameters and process variables on the blending quality and blending end point. Understanding the variability of both the API and the excipients, as well as their impact on the blending process are critical elements for blending QbD. In a first step, the QbD-methodology is systematically used to (1) establish the critical quality attribute content uniformity and to link this CQA to its surrogate blend homogeneity, (2) identify potentially critical input factors that may affect blending operation quality and (3) risk-rank these factors to define activities for process characterization. Subsequently, a DEM-simulation-based characterization of the blending process is performed. A statistical evaluation is finally presented, relating blend homogeneity of systems with low particle number to the regulatory requirements. Data are then used to map out a three-dimensional knowledge space, providing parameters to define a design space and set up an appropriate control strategy.

Development of quality-by-design analytical methods

Quality-by-design (QbD) is a systematic approach to drug development, which begins with predefined objectives, and uses science and risk management approaches to gain product and process understanding and ultimately process control. The concept of QbD can be extended to analytical methods. QbD mandates the definition of a goal for the method, and emphasizes thorough evaluation and scouting of alternative methods in a systematic way to obtain optimal method performance. Candidate methods are then carefully assessed in a structured manner for risks, and are challenged to determine if robustness and ruggedness criteria are satisfied. As a result of these studies, the method performance can be understood and improved if necessary, and a control strategy can be defined to manage risk and ensure the method performs as desired when validated and deployed. In this review, the current state of analytical QbD in the industry is detailed with examples of the application of analytical QbD principles to a range of analytical methods, including high-performance liquid chromatography, Karl Fischer titration for moisture content, vibrational spectroscopy for chemical identification, quantitative color measurement, and trace analysis for genotoxic impurities.