SAMPLING
37
Automated techniques for sample production
Lizzie Guest, Jodie Clark, Caroline Kelly - CPI
With ever-increasing development demands within the personal care industry for new and innovative products, including alternative sustainable materials and vegan formulations to name only a few, as well as larger scale campaigns for stability or cost saving exercises, high throughput and automation techniques are being utilised to alleviate pressures and drive innovation. They can produce a large number of samples,
quicker and on a much smaller scale than a classic bench top method, while also automating the analysis of samples, to help drive products to market quicker. This reduces material wastage, frees up formulators' time and offers larger data sets, which can be used by statistical models to direct the next stages of development. This article presents data from a study that
prepared a basic emulsion using a benchtop homogeniser and compared this to the same formulation prepared using automated rotor- stator mixers within a robotic platform, to instil confidence and showcase value in the modern, automated techniques used. The prepared formulations were then characterised using microscopy and particle size measurements.
Down selection of mixer types The first part of this investigation involved
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identifying mixer types and heads that would produce a stable emulsion while also being comparable to each other. Three automated mixer heads were identified and one benchtop. Rotor stator mixers, which are standard
for homogenisation of emulsions, and cutter blades, as provided as part of the robotic formulation vessels, were chosen. For the robotic platform, the integrated mini reactor vessels, known as formulation vessels, were used to create the samples. The platform has 12 vessels in total, which can all be run independently with their own set of mixing times, mixing speeds, and temperatures. During this work, both formulation vessels and automated overhead mixers were trialled. Both the rotor-stator and cutter blade heads used were 30 mm in diameter. The overhead mixer was fitted with the smallest head, with a diameter of 12 mm. Computational fluid dynamics (CFD) was used alongside this work to give a visual aid of the type of mixing occurring in the formulation vessels: It shows that the rotor-stator mixer has higher stress levels at the head but that the cutter blade radiates stress further out and higher up into the formulation vessel. Because of this, it was decided that the addition of scraper arms, which can be
attached to scrape material from the walls of the vessels, would be used to facilitate mixing by bringing more of the formulation in contact with the higher stress zones. For the benchtop batches, standard stainless-steel beakers were used but the robotic platform used integrated formulation vessels. Batch sizes were 750 mL and 80 mL respectively. For the benchtop mixer, the medium-sized
(30 mm) head with square apertures was used. As the aim of the project was to compare mixing techniques, a very basic emulsion was chosen consisting of water, coconut oil, glycerine, polysorbate 60, and xanthan gum. In order to limit differences in batches due to poor dispersion of xanthan gum, a base formulation of water, xanthan gum, and glycerin was made using the benchtop equipment, with the xanthan gum being premixed into the glycerine to aid wetting and dispersion. The rest of the materials were incorporated into the formulations using the proposed different mixing heads. A preliminary part of the project involved
comparing the robotic formulation vessels mixing capability; results showed that after five minutes the samples produced using the cutter blade formed a visually improved dispersion of the materials, whereas the sample made using
June 2025 PERSONAL CARE
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