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CHEMICALS & PHARMACEUTICALS


HOW HIGH SHEAR MIXING CAN IMPROVE YOUR PHARMACEUTICAL EMULSIONS


Silverson explains how high shear rotor/ stator mixers offer advantages in the creation of stable emulsions


manufacture of pharmaceutical creams and lotions through to more complex applications such as adjuvants to improve the immune response to the antigens used in vaccinations. Whether it is a Water-In-Oil (W/O) emulsion or an Oil-In-Water (O/W) emulsion, getting the emulsion to remain stable in order to deliver the desired results can be a challenging task. Whichever type of emulsion you are


I


manufacturing, and for whichever product, the goal is the same: the globule size needs to be reduced sufficiently enough so that the oil and water phases are finely and uniformly dispersed into one another, ensuring that when the mixer is stopped, the phases remain combined and don't begin to separate. Some types of mixing equipment, such as


stirrers and agitators, simply move the two phases around and don't have any significant effect on the droplet size. So even though it may appear visually that the two phases have been combined, after time they will begin to separate. Separation of the emulsion is to be avoided as this can affect the shelf-stability, product quality and can even make products such as adjuvants unusable due to inconsistencies between batches. So, while conventional mixing equipment like


stirrers and agitators have their uses and are sufficient for simple blending tasks, a high degree of shear energy is required in order to obtain the finest possible droplet size. The more shear energy introduced into the mix, the smaller the droplets will become. As such, high shear rotor/stator mixers are advantageous for creating stable emulsions. Silverson high shear mixers can easily


achieve emulsions with a globule size of 2 to 5 microns. Finer emulsions down to 0.5 microns can be obtained, depending on the formulation. This is achieved as follows: the large globules from both phases are drawn by the high speed rotation of the rotor blades into the centre of the workhead. The globules are driven towards the workhead periphery by centrifugal force where they are subjected to a


n the pharmaceutical industry, emulsions are a key component in many formulations and products. Emulsions are used in the


UHS in-line mixers create a fine, uniform emulsion


milling action in the narrow gap between the rotor blades and the inner wall of the stator. The globules are then subjected to additional high shear energy by being forced at high velocity through the stator perforations – in this case an emulsor screen, an interchangeable workhead which is available for all Silverson mixers. The smaller droplets are expelled radially from the workhead into the bulk of the emulsion, where the mixing cycle continues until the targeted droplet size and stability are achieved.


Batch-to-batch consistency Successfully creating a stable emulsion requires the correct balance of ingredients, processing techniques and equipment to get it right. With a Silverson mixer you can take one of these factors out of the equation. It will rapidly produce a fine, uniform emulsion in no time, and batch-to-batch consistency is guaranteed, time after time. Silverson Machines offer capacities from


laboratory scale volumes of 1ml up to production scale mixers capable of mixing volumes of up to 30,000 litres. The company has been a pioneer in the design and


manufacture of a new generation of “Ultra Hygienic” mixing equipment specifically aimed at the pharmaceutical industry. This range of Ultra Hygienic mixers is 3A tpv Certified and designed to comply with FDA and cGMP requirements; some models are also EHEDG Certified. Two of Silverson’s recently launched


laboratory scale models are available in an Ultra Hygienic specification - the FMX5 UHS and the Verso UHS. The FMX5 UHS, an Ultra Hygienic


laboratory scale version of Silverson's production scale Flashmix mixers, is recommended for hygienic applications and clean industries and offers single or double mechanical sealing arrangements. The Verso UHS is an Ultra-Hygienic


version of the standard Verso laboratory scale In-Line mixer and is suitable for stringent applications. As all Silverson mixers are built to the same fine tolerances, this mixer is able to give an accurate forecast of the performance of the production scale UHS In-Line mixer, making scale up an easy process. For larger scale Ultra Hygienic mixing


requirements, Silverson UHS In-Line mixers are ideal. These mixers offer further versatility with multistage rotor/stator configurations as standard options, resulting in substantially faster mixing times by reducing the number of recirculation passes required and offering greater particle size reduction. These mixers have crevice-free construction, Ultra Hygienic shaft seals and are constructed from materials on the FDA master list.


Silverson Machines E: sales@silverson.co.uk www.silverson.co.uk


JUNE 2022 | PROCESS & CONTROL 31


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