Ultrasonic energy, broadly defined as sound above the range of human hearing (approximately 20,000 cycles/s or 20 kHz), can be used in several ways during the production of cannabis to ensure that the product is of the highest quality. In addition to providing a tutorial on how ultrasonic equipment works, this article describes how the equipment is applied in laboratory practices and manufacturing. Examples include extraction procedures, cleaning ion targets in mass spectrometers, preparing oil emulsions for edible or drinkable products, degassing oil (removing trapped air) to maintain stable oil volume during selling, degassing high performance liquid chromatography (HPLC) solvents, bubbling off ethanol before oil distillation, and removing gums and waxes from glassware used in production.
Ultrasonic energy is commonly associated with ultrasonic cleaning. As explained by Edward W. Lamm in his article “The Development of Ultrasonic Cleaning” (1), its history dates to the early 1930s and work done at Radio Corporation of America (RCA) laboratories in New Jersey. The first practical applications, according to Lamm’s article, were introduced in the 1950s, and were operated at 18–40 kHz. “Up until the late 1980s most of the commercially available systems operated at 25–40 kHz,” Lamm stated.
Today, ultrasonic cleaners are available in several frequencies, including 25, 45, 80, and 130 kHz. Units are also available offering dual-frequency options.
Ultrasonic energy is used in research, product development, and manufacturing operations. Typically, these involve homogenizing, emulsifying, dispersing, dissolving or mixing difficult samples, and degassing liquids to remove trapped air.
Ultrasonic energy is a proven technique to achieve fast, safe extraction. For example, it is a method often specified in United States Pharmacopeia (USP) monographs to extract active pharmaceutical ingredients from carriers for content uniformity and potency assay tests.
In cannabis production, most regulated markets require all cannabis products to be tested for efficacy (active ingredients, such as cannabinoids and terpenoids), as well as for contaminants (such as pesticides, mycotoxins, heavy metals, microbes, and residual solvents).
Cannabis products include plant material (mostly flowers and trimmed leaves), concentrated extracted essential oils (concentrates, waxes, and oils), and infused products (edibles such as candies, chocolates, baked goods, transdermal patches, suppositories, and beverages).
Clearly, accurate test results depend on efficient, reproducible extraction from these often complex matrices, and sonication is one way many cannabis laboratories seek to achieve those goals. Sonication is valuable because it deposits energy into the solvent–matrix system, effectively speeding the process of extraction and dissolution.
Mass spectrometers are typically the workhorse instruments in a cannabis laboratory. Many laboratories have inductively coupled plasma–mass spectrometry (ICP-MS), liquid chromatography–tandem mass spectrometry (LC–MS/MS) and gas chromatography (GC)–MS/MS instruments all in the same laboratory.
Since cannabis contains viscous oils and resinous compounds of moderate to high molecular weight, ion sources and associated components can get contaminated with organic residues that are difficult to remove. In particular, contamination of electrodes that steer the ions leads to defocusing and loss of signal.
Sonication is often the most efficient method to clean these parts. Likewise, the chromatography injectors and inlets can also become contaminated and clogged with the resins and residues and sonication in a nonpolar solvent is often the method of choice to clean these components as well.
General Cleaning with Sanitation
For cleaning applications, ultrasonic energy is used to remove contaminants from the surfaces of virtually any product that can be safely immersed in a water-based biodegradable ultrasonic cleaning solution. Cleaning solution formulas, dilution recommendations, and operating procedures are available for specific cleaning tasks.
Components of Ultrasonic Cleaning Equipment
There are multiple manufacturers of ultrasonic cleaning and processing equipment. Regardless of the manufacturer, common components include
A tank, usually stainless steel, to hold the cleaning solution or water that is typically mixed with a surfactant
- A generator to supply power
- Ultrasonic transducers bonded to the bottom of the tank
- A mesh-bottomed basket (standard or optional) to hold products being cleaned or processed without contacting the bottom of the tank
- A lid (standard or optional) to reduce cleaning solution evaporation and noise
Selection criteria then can move to
- Cleaning tank size (length, width, and depth)
- A control panel that can range from a simple on–off switch to highly sophisticated options including timers, thermostats, and features including sweep, normal, pulse, degassing, and adjustable ultrasonic power and frequency.
- E.W. Lamm, Controlled Environments, October 1, 2003. Available at: www.cemag.us/article/2003/10/development-ultrasonic-cleaning.
- National Hemp Association, “Five Major Types of Cannabis Extraction,” Hemp News (October 28, 2015). Available at: http://nationalhempassociation.org/the-five-major-types-of-cannabis-extraction/.
Bob Sandor is a director at Tovatech LLC. Kirsten Blake is Director of Business Development and Global Sales at Emerald Scientific, a distributor of cannabis-related scientific supplies including reference materials, chemicals, reagents, and equipment. Direct correspondence to: [email protected] and [email protected].
How to Cite This Article
B. Sandor and K. Blake, Cannabis Science and Technology 1(2), 49-51 (2018).