Influence of the dispersed phase fraction on experimental and predicted drop size distributions in breakage dominated stirred systems

Application of Population Balance Models in Particle-Stabilized Dispersions

In this study, a first approach to model drop size distributions in agitated nanoparticle-stabilized liquid/liquid systems with population balance equations is presented. Established coalescence efficiency models fail to predict the effect of steric hindrance of nanoparticles at the liquid/liquid interface during the film drainage process. A novel modified coalescence efficiency is developed for the population balance framework based on the film drainage model. The elaborate submodel considers the desorption energy required to detach a particle from the interface, representing an energy barrier against coalescence. With an additional implemented function in the population balance framework, the interface coverage rate by particles is calculated for each time step. The transient change of the coverage degree of the phase interface by particles is thereby considered in the submodel. Validation of the modified submodel was performed with experimental data of agitated water-in-oil (w/o) dispersions, stabilized by well-defined spherical silica nanoparticles. The nanospheres with a size of 28 nm are positively charged and were hydrophobized by silanization with dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammoniumchloride. This modeling approach is a first step toward predicting time-resolved dynamic drop size distributions of nanoparticle-stabilized liquid/liquid systems.

Process Analytical Technology for the Production of Parenteral Lipid Emulsions According to Good Manufacturing Practices

The good manufacturing practices (GMP) and process analytical technology (PAT) initiatives of the US Food and Drug Administration, in conjunction with International Council for Harmonisation (ICH) quality guidelines Q8, Q9, and Q10, ensure that manufacturing processes for parenteral formulations meet the requirements of increasingly strict regulations. This involves the selection of suitable process analytics for process integration and aseptic processing. In this article, we discuss the PAT requirements for the GMP-compliant manufacturing of parenteral lipid emulsions, which can be used for clinical nutrition or for the delivery of lipophilic active ingredients. There are risks associated with the manufacturing processes, including the potential for unstable emulsions and the formation of large droplets that can induce embolisms in the patient. Parenteral emulsions are currently monitored offline using a statistical approach. Inline analytics, supplemented by measurements of zeta potential, could minimize the above risks. Laser scanning technology, ultrasound attenuation spectroscopy, and photo-optical sensors combined with image analysis may prove to be useful PAT methods. In the future, these technologies could lead to better process understanding and control, thus improving production efficiency.

Developing Cream Formulations: Renewed Interest in an Old Problem

This work aimed at establishing a framework to screen and understand the product variability deeming from factors that affect the quality features of cream formulations. As per Quality by Design - based approach, cream quality target profile and critical quality attributes were identified, and a risk assessment analysis was conducted to qualitatively detect the most critical variables for cream design and development. A Plackett-Burman design was used to screen out unimportant factors, avoiding collecting large amounts of data. Accordingly, 2 designs of experiments (DoE-1 and DoE-2) were performed, and the effects of independent variables on the cream formulations responses were estimated. At different factor combinations, significant variability was observed in droplet size, consistency, hardness, compressibility, and adhesiveness with values ranging from 2.6 ± 0.9 to 10 ± 6 μm, 7.93 ± 0.05 to 13.53 ± 0.14 mm, 27.6 ± 0.3 to 58.4 ± 1.1 g, 38 ± 6 to 447 ± 37 g.s, and 25.7 ± 2.1 to 286 ± 33 g.s, respectively. The statistical analysis allowed determining the most influent factors. This study revealed the potential of Quality by Design methodology in understanding product variability, recognizing the most critical independent variables for the final product quality. This systematic approach in the pharmaceutical field will yield more robust products and processes, provisioning time and cost effective developments.

Numerical Investigation of Vertical Plunging Jet Using a Hybrid Multifluid–VOF Multiphase CFD Solver

A novel hybrid multiphase flow solver has been used to conduct simulations of a vertical plunging liquid jet. This solver combines a multifluid methodology with selective interface sharpening to enable simulation of both the initial jet impingement and the long-time entrained bubble plume phenomena. Models are implemented for variable bubble size capturing and dynamic switching of interface sharpened regions to capture transitions between the initially fully segregated flow types into the dispersed bubbly flow regime. It was found that the solver was able to capture the salient features of the flow phenomena under study and areas for quantitative improvement have been explored and identified. In particular, a population balance approach is employed and detailed calibration of the underlying models with experimental data is required to enable quantitative prediction of bubble size and distribution to capture the transition between segregated and dispersed flow types with greater fidelity.