Aqueous Two-phase Systems: Pros and Cons

Phase systems consisting of polymers or polymers with saltwater can be used to separate cells, membranes, viruses, proteins and other biomolecules. Aqueous two-phase systems, also known as ATPS, use the properties of the polymer surface and conformation of the materials to partition biomolecules.

Skip to:

Antibodies can be separated using an aqueous two-phase system
Design_Cells | Shutterstock

What are aqueous two-phase systems?

The ability of polymer mixtures to separate phases was discovered in the 1950s, and has since then been applied to separate biomolecules. Phase separation occurs because most polymer pairs are not compatible in liquid solutions, therefore causing them to separate into two phases that are in equilibrium. Therefore, each phase contains water and one of the polymer types.

Biophysically, the phase separation of ATPS occurs due to the polymer’s high molecular weight working in tandem with interactions between parts of the polymers. Water forms noncovalent interactions with the polymers. Salt present in the mixture can influence the phase separation, by promoting separation at different salt concentrations.

ATPS has a wide range of uses, including analyzing biomolecules, cell surfaces, and interactions between the two, as well as cell population fractionation, recovery of products in industry, and waste treatments. While it has applications in both the laboratory and industrial setting, large scale applications are not as common as laboratory applications.

Aqueous Two-Phase Systems (ATPS)

Advantages of aqueous two-phase systems

ATPS are simple, fast, and relatively cheap systems, making them applicable to a number of applications. These systems can be used with both streams of smaller particulate matter and large volumes moving continuously with short contact times. Similarly, several types of ATPS exist, such as classic polymeric ATPS and ionic liquid-based ATPS.

In partitioning, ATPS is particularly powerful compared to methods such as centrifugation and electrophoresis. This is due to a large number of factors playing a role in partitioning, which results in ATPS being a highly customizable system. High selectivity is possible with ATPS by altering the properties of the system to give one interaction an advantage and make it predominant.

Some selectivity issues at the laboratory scale are still being resolved. For example, it has historically been more popular to extract protein at high purity from mixtures of polysaccharides and proteins than to extract polysaccharides only.

The development of methods for this purpose has shown high efficiency (as high as 100% for mannan polysaccharide recovery) and significantly higher efficiency than more popular affinity purification methods.

Disadvantages of aqueous two-phase systems

Predicting the partitioning of biomolecules in ATPS can be difficult. This is especially true for larger molecules. The macromolecules’ partitioning is more variable than that of smaller molecules because their distribution is decided based on several parameters of the phase system’s properties and that of the substance’s, as well as the interaction between the two. The number of parameters makes predicting partitioning complex.

ATPS are used in both laboratory and industrial settings. While purification has previously been an issue, developments in the field have increased purification factors for separating proteins from their contaminants. These have been successfully applied to the laboratory scale but not the industrial scale.

This shortcoming has been attributed to misunderstanding or lack of understanding of the systems or engineering involved. ATPS has struggled with large scale applications due to other issues, such as achieving the necessary selectivity during protein extraction, the price of the components forming the phase, and the required wastewater treatment associated with ATPS.


  • Hatti-Kaul R. (2001). Aqueous two-phase system: A general overview. Molecular Biotechnology. 
  • Merchuka J.C., et al. (1998). Aqueous two-phase systems for protein separation: studies on phase inversion. Journal of Chromatography B: Biomedical Sciences and Applications.
  • Čížová A., et al. (2017). Efficient separation of mannan-protein mixtures by ionic liquid aqueous two-phase system, comparison with lectin affinity purification. International Journal of Biological Macromolecules.

Further Reading

Last Updated: Apr 8, 2023

Sara Ryding

Written by

Sara Ryding

Sara is a passionate life sciences writer who specializes in zoology and ornithology. She is currently completing a Ph.D. at Deakin University in Australia which focuses on how the beaks of birds change with global warming.


Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Ryding, Sara. (2023, April 08). Aqueous Two-phase Systems: Pros and Cons. News-Medical. Retrieved on July 17, 2024 from

  • MLA

    Ryding, Sara. "Aqueous Two-phase Systems: Pros and Cons". News-Medical. 17 July 2024. <>.

  • Chicago

    Ryding, Sara. "Aqueous Two-phase Systems: Pros and Cons". News-Medical. (accessed July 17, 2024).

  • Harvard

    Ryding, Sara. 2023. Aqueous Two-phase Systems: Pros and Cons. News-Medical, viewed 17 July 2024,


The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
Post a new comment

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.

You might also like...
Is your body out of sync? Study finds organs age at varying rates