Production of Hand Sanitizers with Industrial Ultrasonic Mixers
Hand sanitizer, also known under the alternative terms of hand antiseptic, handrub, or hand rub, is an liquid agent applied to the hands in order to remove or inactivate common pathogens, which can cause diseases (e.g. the SARS-CoV-2 virus causes the COVID-19 disease). Hand sanitizers are typically available as liquid, foam, gel, or spray.
Hand sanitizers can be formulated using different ingredients and compositions. For instance, hand sanitizers can be either alcohol-based or alcohol-free. Alcohol-based hand sanitizing products normally contain between 60 and 95% alcohol. As alcohols, the use of ethanol (ethyl alcohol), isopropanol, or n-propanol is most common. Highly concentrated alcohol (i.e. 60% and higher) destroys proteins. By denaturing proteins, many pathogens (disease-causing microorganisms) are inactivated or killed. Alcohol-free hand sanitizers are an alternative product, in which disinfectants, such as benzalkonium chloride (BAC), or on anti-microbial agents, such as triclosan, are used as active ingredient to inactivate or kill microorganisms. In both, alcohol-based and alcohol-free hand sanitizers, the active ingredients against pathogens can dry out the skin by destroying the natural skin barrier. Therefore, most hand sanitizer formulations contain skin nourishing additives such as emollients (e.g., glycerin, oils) to rehydrate the skin. Other ingredients such as thickening agents, fragrance, colorant etc. may be added to modify the texture, smell and appearance of hand sanitizing products.
Ultrasonic Mixing and Blending of Hand Sanitizers
Ultrasonic agitators are the most effective mixing technology to produce hand sanitisers (also known as hand antiseptic, handrub, or hand rub) in form of liquids, gels, sprays or lotions.
Since ultrasonic mixers create high shear forces, they provide the required agitation to blend the ingredients into a cohesive mixture. Such powerful and reliable mixing is necessary in order to produce potent and reliable disinfecting agents such as hand sanitizers as well as surface disinfection agents.
How Does Ultrasonic Mixing Work?
Ultrasonic mixers and agitators create acoustic cavitation, which results in highly intense shear forces. Therefore, ultrasonic mixing systems are widely used to emulsify two or more otherwise immiscible liquids and to disperse solid particles in liquids and slurries. Ultrasonic mixing and blending is achieved by coupling high-power ultrasound waves into a liquid or slurry. The ultrasonic waves are transmitted via a high-intensity ultrasonic probe into a batch tank or in an in-line flow cell reactor. Only probe-type ultrasonicators can generate the intense cavitational forces, which are required for the formulation of homogenous and long-time stable mixtures. The ultrasonic probe vibrates in the liquid at a very high frequency (e.g. 20kHz) and creates intense acoustic / ultrasonic cavitation in the liquid.
In the ultrasonically generated cavitation field, the collapse of cavitation bubbles creates powerful shear forces, which disrupt droplets, agglomerates and even solid particles. Also, ultrasonic cavitation produces high-speed liquid streams with up to 1000km/h. The cavitational liquid jets impinge particle agglomerates, disrupt droplets, improve material transfer within liquids and slurries and disperse solids throughout the medium. In the ultrasonic cavitation field, pressures alternate quickly and repeatedly between vacuum and up to 1000bar. A rotary mixer with 4 mixer blades would need to operate at a staggering 300,000 RPM to achieve the same frequency of alternating pressure cycles. Conventional rotary mixers and rotor-stator mixers create no significant amount of cavitation because of their limitation in speed.
Hand Sanitizer Formulations with Ultrasonic Blending
The formulation of a hand sanitizing product determines the sanitizer’s effectiveness and spectrum of killing germs (i.e. anti-bacterial, anti-fungal, anti-viral, efficacy against enveloped and naked viruses, encysted parasites etc.)
Since the frequent use of alcohol and alcohol-containing sanitizers on the skin (e.g. hands) dehydrates the skin, which can result in inflammation and irritation, sophisticated hand sanitizers contain skin caring ingredients, e.g. aloe vera, glycerine, jojoba oil, rose hip oil etc.). The ultrasonic emulsification effect blends the different phases of alcohol, additives, oils, and water into a stable and uniform hand sanitizer product.
Common Ingredients for Hand Sanitizers
v65% (or higher %) alcohol (to be effective against a wide variety of viruses and bacteria)
- skin care ingredients such as oils, aloe vera, glycerine, etc.
- water (e.g., distilled or sterile water)
- emulsifier / surfactant
- optionally, thickener (e.g. xanthan gum), foaming agents, fragrance, sporicides (e.g., hydrogen peroxides to eliminate bacterial spores)
Effective Hand Sanitizers Against COVID-19
Hygiene and especially hand hygiene is an important factor to prevent the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes the disease COVID-19. Whilst thorough hand washing with water and soap is recommended when ever possible, hand sanitizers are a reliable alternative, especially when hand washing with water and soap is not available.
The World Health Organization (WHO) recommends two formulations of alcohol-based sanitizers, which have been tested to be effective against the coronavirus SARS-CoV-2. Scientists from Germany and Switzerland have tested and confirmed the sanitizer formulations’ effectiveness against SARS-CoV-2.
Sanitizer Formulation No. 1:
- ethanol — 80% by volume (vol/vol)
- glycerine (also known as glycerol) — 1.45% vol/vol
- hydrogen peroxide — 0.125% vol/vol
Sanitizer Formulation No. 2:
- isopropanol (also known as 2-propanol or isopropyl alcohol) — 75% vol/vol
- glycerine — 1.45% vol/vol
- hydrogen peroxide — 0.125% vol/vol
Both hand sanitizer formulations above inactivate the virus sufficiently after 30 seconds exposure, when applied thoroughly.The blending of the formulations above can be performed using an ultrasonic batch or inline system.
High Performance Ultrasonicators
Hielscher Ultrasonics is long-experienced manufacturer of high-power ultrasonicators for applications that involve the mixing, blending, and agitation of various liquid/liquid or liquid/solid mixtures.
For the food-/pharma-grade processing of hand sanitizers on industrial level, high-performance ultrasonic equipment is required to process large volume in an ultrasonic batch setup or in a continuous flow-through system. Hielscher Ultrasonics is long-experienced and trusted supplier of high-performance ultrasonic mixing equipment, which is worldwide integrated in manufacturing plants across the food, pharma, cosmetic and personal care industries.
Hielscher Ultrasonics’ sophisticated ultrasonicators can be precisely controlled and give the operator full control over the important process parameters such as amplitude, pressure, temperature and sonication time. This allows for the optimisation of the sonication process, making the process most efficient and economical.
The extensive range of accessories such as sonotrodes (probes), booster horns, flow cell reactors and further add-ons enable to configure the ultrasonic mixing system specifically for the processed ingredients and the targeted output.
Ultrasonic Process Monitoring
All Hielscher digital ultrasonicators – from lab to industrial size – are equipped with an intelligent software, which makes it easy to precisely control, monitor and revise the ultrasonic process. Amplitude, energy input limit, pulse cycles and sonication time can be pre-set via the user-friendly software. Via colour touch-display the menu can be easily accessed and is intuitively to handle. The browser remote control enables the operator to operate and monitor the ultrasonic system remotely.
All important ultrasonic process data (such as amplitude, temperature, pressure, net energy, total energy, time and date) are automatically stored on an integrated SD-card. The automatic data protocolling is highly valued in the food and pharma industry, since it allows the food manufacturer to revise the processing condition of any sonicated lot. This enables for process standardisation, continuously high quality output and the implementation of Good Manufacturing Practices (GMP).
Industrial Grade Ultrasonicators
Hielscher Ultrasonics’ industrial ultrasonic processors can deliver very high amplitudes. Amplitudes of up to 200µm can be easily continuously run in 24/7 operation. For even higher amplitudes, customized ultrasonic sonotrodes are available. The robustness of Hielscher’s ultrasonic equipment allows for 24/7 operation at heavy duty and in demanding environments.
The table below gives you an indication of the approximate processing capacity of our ultrasonicators:
|Batch Volume||Flow Rate||Recommended Devices|
|1 to 500mL||10 to 200mL/min||UP100H|
|10 to 2000mL||20 to 400mL/min||UP200Ht, UP400St|
|0.1 to 20L||0.2 to 4L/min||UIP2000hdT|
|10 to 100L||2 to 10L/min||UIP4000hdT|
|n.a.||10 to 100L/min||UIP16000|
|n.a.||larger||cluster of UIP16000|
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Literature / References
- Aparajita Chatterjee, Giulia Bandini, Edwin Motari, John Samuelson (2015): Ethanol and Isopropanol in Concentrations Present in Hand Sanitizers Sharply Reduce Excystation of Giardia and Entamoeba and Eliminate Oral Infectivity of Giardia Cysts in Gerbils. Antimicrobial Agents and Chemotherapy 59(11), Nov. 2015. 6749–6754.
- Kiran A. Ramisetty; R. Shyamsunder (2011): Effect of Ultrasonication on Stability of Oil in Water Emulsions. International Journal of Drug Delivery 3, 2011. 133-142.
- Shabbar Abbas, Khizar Hayat, Eric Karangwa, Mohanad Bashari, Xiaoming Zhang (2013): An Overview of Ultrasound-Assisted Food-Grade Nanoemulsions. Food Engineering Reviews 2013.
- Ng Sook Han, Mahiran Basri, Mohd Basyaruddin Abd Rahman, Raja Noor Zaliha Raja Abd Rahman, Abu Bakar Salleh, Zahariah Ismail (2012): Preparation of emulsions by rotor–stator homogenizer and ultrasonic cavitation for the cosmeceutical industry. Journal of Cosmetic Science 63, September/October 2012. 333–344.