Deep Eutectic Solvents for Highly Efficient Extraction

Deep eutectic solvents (DESs) and natural deep eutectic solvents (NADES) offer advantages as extraction solvents on many levels and are thereby a promising alternative to conventional organic solvents. Deep eutectic solvent work excellent in combination with ultrasonic extraction and give high yields of premium quality extracts. Find out more about ultrasonic extraction using natural deep eutectic solvents.

What are Deep Eutectic Solvents (DES)?

Deep eutectic solvents (DESs) are mixtures of at least one hydrogen bond acceptor (HBA) and one hydrogen bond donor (HBD), including carboxylic acids and other renewable compounds. According to Cai et al. (2019), “the strong hydrogen bonding interaction between HBA and HBD is the most important factor for the formation of DESs.” [Cai et al. 2019] For hydrogen bond donors (HBDs), compounds such as sugars, amino acids, carboxylic acids (e.g., benzoic acid, citric acid, succinic acid) or amines (e.g., urea, benzamide) are often used. The chemical interaction potential of HBDs is the major factors contributing to formation and efficiency of deep eutectic solvents. Halide salts such as choline chloride or zinc chloride can be also used in conjunction with the HBDs. Other choline chloride-based DES are formed with malonic acid, phenol or glycerine. As result of the strong hydrogen-bonding interactions, the melting point of deep eutectic solvents is significantly reduced when compared to its individual components. In contrast to conventional solvents (e.g., ethanol, methanol, hexane, butane etc.) DES are non-volatile, which means they have a very low vapour pressure and are thereby hardly inflammable. The toxicity of deep eutectic solvents is low, their biodegradability is high, and the necessary precursors are inexpensive, easily and plentiful available as well as renewable. Natural deep eutectic solvents (NADESs) are even more eco-friendly as all precursors are sourced from natural sources. DESs also offer a tunable solvency based on the chemistry of the solute and the species used to create the DES. Some NADES exhibit a high viscosity and they are therefore not very suitable for batch extraction. However, NADES with higher viscosities can be successfully applied as solvents in ultrasonic flow-through extraction.

How Does Ultrasonic Extraction with Deep Eutectic Solvents Work?

Ultrasonic extraction is based on the sonomechanical effects of high-intensity, low-frequency ultrasound. To promote and intensify the extraction of botanical compounds (i.e., bioactive substances) via ultrasonication, high-power ultrasound waves are coupled via an ultrasonic probe (also called ultrasonic horn or sonotrode) into the liquid medium, i.e. the slurry consisting in the botanical raw material and the (natural) deep eutectic solvent. The ultrasound waves travel through the liquid and create alternating low-pressure / high-pressure cycles. During low-pressure cycles, minute vacuum bubbles (so-called cavitation bubbles) are created, which grow over several pressure cycles. During those cycles of bubble growth, the dissolved gases in the liquid enter the vacuum bubble, so that the vacuum bubble transform into growing gas bubbles. After growing over several cycles, the vacuum bubbles reach a certain size at which they cannot absorb more energy, so that they implode violently during a high-pressure cycle. The bubble implosion is characterised by intense cavitational forces, including very high temperature and pressure reaching up to 4000K and 1000atm, respectively; as well as corresponding high temperature and pressure differentials. These ultrasonically generated turbulences and shear forces break plant cells up and release the intracellular bioactive compounds into the (natural) deep eutectic solvent. Ultrasonic extraction opens the cell structure of botanicals and intensifies mass transfer between plant material and solvent. Sonication promotes thereby the efficacy of natural deep eutectic solvents. Ultrasonic extraction with (natural) deep eutectic solvents results in exceptionally high yields within a very short processing time.

Power ultrasound waves disrupt the cell structure of botanicals, release the bioactive compounds and promote the mass transfer between the plant material and the solvent (e.g., deep eutectic solvents).

The combination of ultrasonic extraction with (natural) deep eutectic solvents gives you the opportunity combine the process intensifying power of ultrasound with the remarkable solubilizing effects and outstanding designability of deep eutectic solvents. Due to the superior efficiency of ultrasonic extraction, ultrasonicators are also successfully used for water extraction.
Contact us now to learn more about the powerful ultrasonic extraction application using deep eutectic solvents!

High-Performance Ultrasonic Extractors

Ultrasonic extraction is a reliable processing technology, which facilitates and accelerates the production of high-quality extracts from various botanical as well as any solvent. Ultrasonic extraction is highly compatible with (natural) deep eutectic solvents, which are favourable due to their excellent solubilizing power, designability to the extract, sustainability, biodegradability, and eco-friendliness. The combination of the process intensification of power ultrasound with the advantages of (natural) deep eutectic solvents gives this process technology superiority on many levels. Hielscher Ultrasonics portfolio covers the full range from compact lab ultrasonicators to industrial extraction systems. All of them are of course suitable for the extraction with deep eutectic solvents.
Our long-time experienced staff will assist you from feasibility tests and process optimisation to the installation of your ultrasonic system on final production level.

The table below gives you an indication of the approximate processing capacity of our ultrasonicators: