Most commonly used disinfectants

PEROXYACETIC ACID

Peroxyacetic acid solutions from 0.2% to 35% can be used as substitutes for glutaraldehyde. Peroxyacetic acid is a corrosive and oxidizing substance, which at concentrations above 10% is assigned R-phrases: 7-10-20/21/22-35 and S-phrases: 3/7-14-36/37/39-45.

HYDROGEN PEROXIDE

It is used in concentrations of approximately 35%. At concentrations above 20% it is corrosive and oxidizing. The assigned phrases are R: 8-34 and S: 3-28-36/39.

ETHYL ALCOHOL

It is indicated for skin disinfection, but is ineffective against certain types of viruses and most spores. It is a flammable substance which is assigned the following R: 11 and S: 7-16.

ISOPROPYL ALCOHOL

It is used as a topical antiseptic in concentrations of 70% in water, with an effectiveness equivalent to that of ethanol. It is a flammable substance which is assigned the following R: 11 and S: 7-16.

ALDEHYDES

The activity of aldehydes, basically formaldehyde and glutaraldehyde, is linked to the denaturation of proteins and nucleic acids by chemical reduction. Aldehydes destroy bacteria and microscopic fungi very well and also have an excellent virucidal action. They are used to disinfecting surfaces, equipment and instruments.

FORMOL – FORMALDEHYDE

Formalin is the solution of formaldehyde in water in a proportion of about 37% in weight, containing between 10 and 15% of methanol to prevent its polymerization. Formaldehyde solutions containing concentrations of formaldehyde equal to or higher than 5% are an effective liquid disinfectant.

Formaldehyde is a particularly dangerous product: irritant at very low concentrations, sensitizing allergen, and probably carcinogenic. Exposure must be kept to a minimum. The assigned phrases are: R: 23/24/25-34-40-43 and S: 26-36/37-45-51.

GLUTARALDEHYDE

The 2% glutaraldehyde solution applied for 30 minutes is effective as a disinfectant, and, in applications of 10 to 12 hours, it can be used as a sterilant. It is a substance classified as noxious, which is assigned the R: 20/22-37/38-41-42/43-50 and S: 26-36/37/39-45-68.

Formaldehyde and glutaraldehyde can be used alone or in combination with a detergent, the latter combination being particularly effective on polyviruses.

CHLORINE. SODIUM HYPOCHLORITE

Chlorine is the universal disinfectant, active against all microorganisms. It is generally served in the form of sodium hypochlorite, with different concentrations of free chlorine. As a general disinfectant for all types of laboratory work, a concentration of 1 g/l (1000 ppm) of free chlorine is used. In cases of blood splashes, or in the presence of organic matter in appreciable quantity, a more concentrated solution of 10 g/l (10000 ppm) of free chlorine is used for disinfection.

These dilutions are prepared from commercial bleach (from 40 to 80 g/l of free chlorine). If 40 g of free chlorine per liter is used, the preparation of the 10 g/l solution will be: 250 ml of bleach (40 g/l of free chlorine) + 750 ml of H2O.

These solutions are unstable, therefore they must be kept covered and daily preparation is recommended.

Sodium hypochlorite solutions containing chloride concentrations higher than 10% are to be considered as corrosive, and are assigned R: 31-34 and S: (1/2)-28-45-50 phrases.

QUATERNARY AMMONIUM COMPOUNDS

This set of compounds is also known as “quats”. They are soluble in water and alcohol and have surfactant properties.

The spectrum of activity is quite high on bacteria and fungi, but low against viruses and spores.
Some microorganisms, such as pseudomonas, find in some quaternary ammoniums, such as benzalkonium chloride, a perfect culture medium.

Quaternary ammonium compounds are inactive in hard water, so they should not be used for the disinfection of the water from the draining siphons, which are rich in salts.

PHENOLIC COMPOUNDS

Both halogenated and non-halogenated aryl phenols have a very good bactericidal activity, but their fungicidal activity is very discreet and their virucidal action is debatable. Phenol and its derivatives are irritants of the skin and respiratory and ocular mucous membranes, have allergenic and photosensitizing effects, and the assigned phrases are R: 24/25-34 and S: 28-45.

IODINE AND IODOPHORES

The action of these disinfectants is similar to that of hypochlorite. The clean surfaces can be treated with solutions containing 75 ppm of free iodine. In the presence of a significant amount of proteic material, its effectiveness is not as good. Iodophores can be diluted in ethyl alcohol for hand washing or as a sporicide.

Iodine is considered a harmful substance and is assigned R-phrases: 20/21 and S-phrases: 23-25.

POVIDONE IODINE (POLYVINYLPYRROLIDONE COMPLEX WITH IODINE)

It contains between 9 and 12% of free iodine. It is used as a topical disinfectant.