Ultrasonic probe sonicators are versatile systems that find applications in many areas. Their applications range from emulsion preparation, dispersion, and protein extraction, to cosmetics manufacturing, tissue preparation, and degassing of liquids, amongst others. While different sonication systems are used for different applications, every system consists of three elements: a power generator that supplies input AC supply; a transducer (featuring piezoelectric converter) which converts electrical energy coming from the generator into high-frequency mechanical vibrations; and a probe or a horn which amplifies these vibrations by expanding and contracting longitudinally whilst transmitting them down as ultrasonic waves into the sample. The intensity of vibrations is highest at the tip of the probe thereby causing cavitation and leading to implosion of microscopic bubbles. This releases tremendous energy that can be used to process the sample.

Modern systems allow practitioners to control the tip’s amplitude according to the sample being processed. The ultrasonicator systems also allow the user to set the sample processing in pulse mode or use temperature-monitoring mechanism to maintain the integrity of samples. However, there are applications when ultrasonic probe sonicators are not a suitable choice to process the sample. Some general parameters to assess whether ultrasonic homogenizers are suitable for a particular application or not include:

1. Character of your sample

Ultrasonic probe sonicators produce great results when the sample processed is typically liquid or small solid particles in a liquid in need of uniform homogenization. As a result, ideal applications include cell disruption, nanoparticle dispersion, and DNA extraction, to name a few. On the other hand, if the sample contains more of solids than the liquid, using sonicator systems may produce unsatisfactory results. Ultrasonicator systems may not be the best option for directly processing large tough tissues.

2. Heat sensitivity of your sample

Heat sensitivity of the sample is an important parameter to decide whether or not to go with ultrasonic processing. Since ultrasonic homogenizers generate large amount of heat, processing samples that are highly sensitive to heat may be inappropriate. Even if in some cases where sonicators are used, care should be taken to use a pulse mode or put together a recirculation loop setup comprising a sonicator, ultrasonic reactor, and a cooling jacket. As a result, since assays comprising RNA are heat-sensitive, using ultrasonication to process them is inappropriate.

3. Processing effect desired on your sample

Some applications require a shearing effect on the sample whilst others require a sample to be cut or tore apart. Ultrasonication systems form an ideal choice for the former category of applications, such as DNA shearing. Alternatively, if you need to tear apart your samples, probe sonicators don’t form the ideal choice. Applications that fall into this category include processing tough animal tissues and cells.