Due to the corona crisis, there is an acute shortage of alcohol-containing gels (alcogel).

It is important that the gel contains at least 70% alcohol. This can be ethanol or isopropanol. There is a slight preference for isopropanol because it is slightly less volatile and therefore remains on the skin longer. However, during the crisis there is a worldwide shortage of isopropanol and it has become considerably more expensive. Optionally, it is possible to switch partially or completely to ethanol.
Concentrations of 70-85% alcohol are common. High concentrations such as 85% are especially interesting when used on damp hands because the alcohol will otherwise dilute too much. Higher concentrations are not recommended because they do not sufficiently moisten the micro-organism and are effective.

From the official channel, preference is given to the "WHO formula": Glycerol 1.45%, hydrogen peroxide 3%, ethanol for 80% or isopropanol for 75% and water up to 100%.

https://www.who.int/gpsc/5may/Guide_to_Local_Production.pdf?fbclid=IwAR11DMm6GCGz8gZQaDcBtBxrHMfaQjX4zmonEkGo6UVac12z5u7hBq9l9gw

Hydrogen peroxide is less important in this formula during the crisis because it is mainly for antibacterial applications and covid-19 is a virus.

Glycerol serves to moisturize the hands and can be replaced by castor oil by default.

In general, this formula is perceived as too current and this formula has mainly been developed to be able to make cheaply in large volumes in developing countries.

To get a higher viscosity and form a gel, there are some possibilities:

- Hypromellose (Hydroxypropylmethylcellulose)
Hypromellose is the most common and cheapest cellulose variant available in pharmacies. Hypromellose has various qualities and viscosities on the market. In the pharmacy, E4M quality is commonly used with viscosity around 4000 mPa.s. The first parameter determines the ratio of hydroxypropyl and methyoxyl groups and thus determines the polarity. The second factor determines the viscosity. This quality shows good results and can be added at 1.5% to a mixture of glycerine, ethanol and / or isopropanol. It manages to mix it cold and still get a viscous mass.
- Ethanol 70-85%
- Hypromellose 1.5%
- Glycerin 1%
- Water ad 100%

Other grades of hypromellose with different proportions of hydroxypropyl and methoxyl or other viscosities may also be used. In that case it is important to always do a test. Not all qualities of hypromellosis give a completely clear solution. A test was also done with K100M: it tolerates ethanol less well (but better as isopropanol). This has a much higher viscosity in water (100,000 instead of 4000), which means that much less hypromellose is required. This formula is useful, although slightly less clear than the carbomer handles:
- Ethanol 70% (v / v)
- Glycerin 1%
- Hypromellose K100M 0.75%
- Water ad 100%
It is important to properly disperse the hypromellose. This is possible with warm water and a good mixer (or program "gelen" from the unguator). It is recommended to keep mixing / turning until the swelling is complete so that the hypromellosis does not settle.

- Klucel (Hydroxypropyl cellulose)
Hydroxypropyl cellulose (HPC) is normally considered the first choice of cellulose varieties when combination with ethanol is required. HPC usually has a lower viscosity than HPMC in water. But because it tolerates ethanol better, this is compensated for a lot. HPC can therefore be replaced 1-1 from the above formula, but higher concentrations are also possible depending on the wishes. For example, a concentration of 5% is also common.

- Methyl cellulose, carboxymethycellulose and Hydroxyethyl cellulose
Other cellulose variants are generally not recommended. Because they tolerate ethanol less well, the gel will be more cloudy.

- Carbomeer
Carbomers are the industry's first choice in the production of alcohols. In the pharmacy, we are faced with the lack of good neutralizers to neutralize the carbomer that leads to swelling. These neutralizers are often not described in a pharmacopoeia, which makes it difficult to include them in the raw material range of licensed suppliers.
Although carbomer powder (usually carbomer 980) does tolerate ethanol; most neutralizers do not dissolve in ethanol. This ensures that the pH does not change sufficiently and a white appearance is obtained. Above 70%, there are only a few options: AMP-95, Neutrol TE, Diisopropanolamine, triisopropanolamine or the phenomenon c-25. The most common raw material, Tromethamol, is therefore not an option at these alcohol concentrations. Triethanolamine, also often used in the past, is also no longer recommended due to potential reaction with the skin.

- Carbomer gel from the TMF
TMF describes two carbomer gels: one with water and one without. Both formulas are not recommended as a basis for making an antiseptic alcogel.
The water-based carbomer gel, the most common, contains a lot of water, so you have to add at least 70% ethanol to work and so it will be too running. In addition, it also contains tromethamol which will precipitate by this ethanol.
The anhydrous carbomer gel is a simpler formula where the carbomer is swollen by the polarity of the ethanol without a neutralizer. Without water, there is no real pH in this formula. If we then add water, the carbomer will behave differently and a neutralizer is required.