Solid-liquid separation is essential across several industries for compliance, quality control, and efficient production processes. In the pharmaceutical industry, solid-liquid separation is performed in application areas that include active pharmaceutical ingredient (API) purification, biocatalysis, and chromatography, to name a few.
Image Credit: Powder Systems
The separation process can be conducted using various instruments, but the most fitting method depends on the mixture’s properties. This article covers the importance of solid-liquid separation in the pharmaceutical industry, outlining its main principles and applications.
What is solid-liquid separation?
As indicated by the name, solid-liquid separation is a technique used to separate solids and liquids from a mixture so that they can be extracted as individual components, which is key when just one phase is required.
The phase deemed surplus becomes a by-product or waste of the experiment, and both phases remain isolated from one other. This process is common practice in the pharmaceutical industry, as raw materials must remain pure and free from contamination to ensure they are safe for their intended purpose.
The process is split into several stages, including pre-treatment, concentration, separation, and post-treatment, with additional stages optional depending on the mixtures that require separation.
The available systems for solid-liquid separation include centrifuges, filters, and a range of multipurpose equipment if required. Many processes necessitate drying an extra feature, which can be carried out in a separate piece of equipment or, if the assembly allows, combined with existing instruments.
What solid-liquid separation methods are used in pharmaceutical production?
The main solid-liquid separation paradigms deployed in pharmaceutical preparation are centrifugation, filtration, and evaporation. Each presents distinct methods, but often overlaps significantly between the various techniques to yield specific results. For instance, active pharmaceutical ingredients (APIs) are frequently precipitated from a solution before being subjected to a more rigorous method such as depth or membrane filtration or even filtering centrifugation.
Multiple solid-liquid separation methods are typically used to isolate products in a sequence. It is crucial to consider product transfer and ensuing processing steps, such as drying, when exploring product transfer.
Options for solid-liquid separation
As mentioned, several solid-liquid separation methods are used across the pharmaceutical industry. These are determined by the phases required for the desired product, some of which are outlined below.
Centrifuge
Centrifuges are useful in many applications, but users must determine when they are most suitable. A rotor and centrifugal force can be applied to separate liquids and solids of various densities, such as water, oil and sediment.
A variety of centrifuges are available on the market, which are based on size, speed, and the intended application use. These devices are frequently used in biochemistry, cellular, and molecular biology applications.
Depth filter
Where contamination occurs in a liquid phase, depth filters capture and remove particles. It is a cost-efficient method and can store many solids before cleaning or replacement is necessary. Across the pharmaceutical industry, depth filters find use in bioprocessing and cell harvesting applications as they hold back a high quantity of particles without impacting the efficiency of the separation process.
Rotary evaporator
Rotary evaporators are used in solvent removal via evaporation. They are ideal for removing solvents from samples with low boiling points. They are more accurate and efficient as they increase a sample’s surface area for rapid solvent removal.
Single mesh filter
Single mesh filters are used in solid-liquid separation to extract larger particles from a sample. They are frequently deployed in pharmaceutical and biochemical laboratory applications where it is important to eliminate any contaminants and impurities.
The advantages of solid-liquid separation
Solid-liquid separation is a key part of manufacturing in the pharmaceutical industry as active ingredients must be purified, contaminant-free, and safe for use. Any contamination in a mixture poses a potential health hazard to operatives throughout pharmaceutical production and downstream in its intended application.
Solid-liquid separation is also vital as far as quality assurance is concerned, as appearance and composition of a drug product demands consistency. Other major advantages of solid-liquid separation include the following:
- Improved efficiency of washing and isolating solids in complex synthesis processes
- Improved safety measures
- Isolating active ingredients
- Regulatory compliance
Powder Systems Limited and solid-liquid separation
Powder Systems Limited offers an extensive range of solutions for research, development, and large-scale applications owing to its expertise in pharmaceutical and chemical processing production. The company provides solutions suitable for filtration, drying, and other processes, including product sampling and product discharge, and also offers crucial aftercare services to support its clients.
Filtration and drying
Powder Systems Limited designs and manufactures filter dryer systems used in pharmaceuticals, known across the global marketplace for efficiency in solid-liquid processing.
Agitated Nutsche Filter Dryers (ANFD) can scale-up from the laboratory to commercial manufacturing via GFDⓇ, SimpleFilter and production-sized ANFD ranges. These systems effectively wash and isolate solids while overcoming limitations associated with traditional production methods.
ANFD facilitates filtration and drying processes by bringing the two together into a single unit. It is most frequently used in the pharmaceutical industry to yield APIs and other fine chemicals.
In a filter-dryer, the solid and liquid mixture is filtered under pressure through a medium which separates each of the components. The filter cake, which is the solid material, is then dried by the introduction of gas, such as nitrogen or air, through the cake. This gas eliminates any liquid that remains in the solid material and results in a dry, free-flowing powder.
This is a simplified explanation of the process, and there are a range of peripheral benefits and considerations.
ANFD delivers a number of key benefits compared to conventional drying methods, including improved product quality, reduced processing times, and lower production costs. It is especially useful for heat-sensitive products that are hygroscopic or prone to oxidation.
About Powder Systems
Powder Systems Limited (PSL) provides a full range of solid liquid separation solutions for filtration, drying, and processing from research and development activities up to larger commercial production scale. Quality and innovation are central to everything they do. They are proud of their award-winning track record and have been working with industry partners for over 35 years. PSL supports clients by developing solutions to overcome challenging manufacturing processes and provide first-class aftercare services.
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