Ultrasonic Homogenizers Versus High Pressure Homogenizers

Trying to figure out if an ultrasonic homogenizer or a high pressure homogenizer is best for your needs? There are several applications for which either would be suitable, but in most cases, one will be more so than the other.

Below, we explain both technologies, including their pros and cons. We also summarize their features and functionality side by side and reveal which applications they are most appropriate for.

Ultrasonic Homogenizers

Ultrasonic homogenizers (also called sonicators) have a vibrating horn (probe) that is inserted into the sample which is held in a vessel, usually a beaker. The probe vibrates extremely rapidly, which transfers a large amount of energy to the particles surrounding the probe. As a result, bubbles form in the solution and subsequently collapse. This process is referred to as cavitation and creates shear and shock waves throughout the liquid sample.

Left to right: A Q500 Sonicator and a Sonifier® SFX150.

Pros of Ultrasonic Homogenizers

• Ultrasonic homogenizers are powerful tools capable of imparting large amounts of energy in a small volume.
• Small particle sizes can be achieved relatively quickly.
• Probes consist of just one piece so are easy to clean.
• Ultrasonic homogenisers are ideal for quickly processing single, liquid samples.

Cons of Ultrasonic Homogenizers

• Ultrasonic homogenizers tend to generate a large amount of heat, making them less suitable for heat-sensitive samples.
• Small amounts of titanium (from the probe) could end up in the sample.
• The process is rarely used for large-scale applications so may not be ideal if you need to scale up in the future.
• With heavy use, horns need to be replaced frequently.
• Ultrasonic homogenizers can create a lot of noise, so their location needs to be considered carefully.
• This process is unsuitable for high-viscosity liquids and solid samples.

High Pressure Homogenizers

In a high pressure homogenizer, liquid samples are subjected to very high shear forces. The process varies slightly depending on the model of homogenizer you’re using, but usually, the sample is forced through a very narrow channel, such as a homogenizing valve or small openings in a membrane. The result is the creation of high shear forces, a drop in pressure, and cavitation, which combine to homogenize the sample. In some high pressure homogenizers, the sample stream collides with a blade, plate, or ring, which aids in homogenization.

Left to right: A ShearJet® HL60 Electric Hydraulic High Shear Homogenizer and a Micro DeBEE High Pressure Homogenizer.

Pros of High Pressure Homogenizers

• This technology is ideal for use with large, liquid samples.
• High pressure homogenization processes are reproducible and can usually be scaled easily.
• Very small particle sizes can be achieved.
• Many models allow for continuous feeding of samples so there are no maximum volumes.
• High pressure homogenizers can offer flexibility, making them suitable for a variety of applications.

Cons of High Pressure Homogenizers

• High pressure homogenizers are unsuitable for applications requiring the processing of multiple samples.
• Cleaning is labor-intensive and time-consuming.
• Units may be large, heavy, and cumbersome, so not very portable.
• High pressure homogenizers can come with high price tags, so tend to be used mainly for the processing of large samples (although some models can handle small volumes).

Summary of Ultrasonic Homogenizers Versus High Pressure Homogenizers

Both ultrasonic homogenizers and high pressure homogenizers are powerful tools. Generally, ultrasonic homogenizers are highly suitable for low-throughput applications and small sample sizes. Some ultrasonic homogenizers can handle volumes up to 20 L, but many high pressure homogenizers allow for continuous feeding of samples, meaning there is no upper limit to volume.

It should be noted that some ultrasonic homogenizers do allow for flow-through configurations using special flow cells (such as this flow cell for the higher-powered Q2000 Sonicator). However, due to practical considerations around the lifespan of the horn, they generally are not used in situations where run times would be extremely long.

While some high pressure homogenizers can handle small samples (down to around 10 mL), the hassle of cleaning the unit is usually not worth it for such a small sample size. In contrast, setup and cleaning of ultrasonic homogenizers is quick and simple, and they can usually process samples as small as 100 µL with direct sonication, or even smaller if using a cup horn.

For high-throughput applications, where many different samples will need to be run in rapid succession, ultrasonic homogenization is probably more suitable. Ultrasonic homogenizers are easy to clean and offer the potential to process multiple samples at once using a cup horn or special multi-pronged horns.

Both technologies are solid choices for particle size reduction applications, although ultrasonic homogenizers can achieve smaller sizes (below 100 nm) than high pressure homogenizers (roughly 100 nm for higher-pressure units). If you’re dealing with high-viscosity samples, high pressure homogenization will be more suitable. Anything thicker than approximately 4,000 cP (about the viscosity of corn syrup) cannot be processed in an ultrasonic homogenizer. High pressure homogenizers can generally process any liquid that can be pumped.

Both processes generate heat, with ultrasonics usually generating more, although there are methods to keep samples cool while using an ultrasonic homogenizer, and some high-pressure homogenizers have heat exchanger options.

The key features of both technologies are shown below:

The homogenizer technology you go for will depend on your specific application. The table below shows some common applications for ultrasonic homogenization and high pressure homogenization.