Disinfectant Formulations Containing Quaternary Ammonium Compounds and Hydrogen Peroxide

The invention relates to the use of compositions comprising hydrogen peroxide and quaternary ammonium compounds as disinfectants. It further relates to a method for killing or inhibiting the growth of microorganisms by applying a disinfectant composition according to the invention. Another object of the invention is a method for inhibiting the corrosive action of hydrogen peroxide solutions on metals.

The use of quaternary ammonium compounds as biocides is well known (see e.g. Kirk- Othmer's Encyclopedia of Chemical Technology, 3 ^rd Ed., Vol. 7, pp. 793-832, in particular pp. 815—818). Also well known is the use of hydrogen peroxide as an antiseptic (Kirk-Othmer, loc. cit., p. 807). Each of these compounds have their own weaknesses and strengths. For example, quaternary ammonium compounds are less effective in the presence of hard water and surfac- tants, while hydrogen peroxide is less affected by these factors. On the other hand, quaternary ammonium compounds are more stable in solution, and are biologically efficacious at lower concentrations than hydrogen peroxide. A problem with both halogenated quaternary ammonium compounds and hydrogen peroxide is that they are corrosive to metals.

Accordingly, the problem to be solved by the present invention was to provide disinfectant compositions comprising quaternary ammonium compounds and hydrogen peroxide which are chemically stable and non-corrosive to metals.

According to the invention, this problem has been solved by the use of the compositions defined in claim 1 as disinfectants.

It has been found that biocidal quaternary ammonium carbonates and bicarbonates, more specifically, benzylalkyl- or dialkyldimethyl ammonium salts containing either carbonate, bicarbonate, or a combination thereof, as the anion, used in combination with hydrogen peroxide make a highly effective disinfectant which is chemically stable and non-corrosive to metals. The concentrations of quaternary ammonium salts and hydrogen peroxide required to completely kill a given microorganism, such as e.g. P. aeruginosa, are significantly lower than those required when either of the components is taken alone.

Provided is the use of a composition comprising:

(i) at least one biocidal quaternary ammonium compound selected from the group consisting of quaternary ammonium carbonates and quaternary ammonium bicarbonates, and (ii) hydrogen peroxide as disinfectant.

In a preferred embodiment, the quaternary ammonium carbonates and bicarbonates have the formulas

(R ¹ R ² R ³ R ⁴ N^ ₂ CO ² . ^" (I) and R ¹ R ² R ³ R ⁴ N ⁺ HCOJ (II),

wherein R ¹ is benzyl or C ₈ _ ₂₀ alkyl;

R ² is selected from the group consisting of C ₈ _ ₂₀ alkyl and -[(CH ₂ ) ₂ -O] _n -R ⁵ , wherein n is an integer from 1 to 20 and R ⁵ is selected from the group consisting of hydrogen, phenyl and alkyl- substituted phenyl; and R ³ and R ⁴ are independently Ci_ ₂₀ alkyl.

Here and hereinbelow, the expression "Ci_ ₂₀ alkyl" is to be understood to comprise all linear or branched alkyl groups having 1 to 20 carbon atoms, including, but not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, tert-pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl and icosyl. Accordingly, the expression "C ₈ _ ₂₀ alkyl" is to be understood to comprise all linear or branched alkyl groups having 8 to 20 carbon atoms. The expression "alkyl-substituted phenyl" is to be understood to comprise any phenyl group bearing from one to five alkyl groups, in particular Ci_ ₂₀ and preferably Ci_ ₈ alkyl groups as substituents.

More preferably, R ¹ and R ² are C ₈ _ ₂₀ alkyl and R ³ and R ⁴ are methyl.

Still more preferably, R ¹ and R ² are C ₁₀ alkyl, most preferably n-decyl.

Preferably, the weight ratio of quaternary ammonium compound(s) to hydrogen peroxide is from 1 :100 to 2:1, more preferably from 1:20 to 1 :1 and most preferably from 1 :5 to 1 :1.

Another object of the invention is a method for killing or inhibiting the growth of microorganisms, algae and/or fungi, said method comprising applying a disinfectant composition as described above to a substrate in or on which said microorganisms, algae and/or fungi are growing or may grow.

The limitations of the above preferred embodiments of the use as disinfectant likewise apply to preferred embodiments of the method for killing or inhibiting the growth of microorganisms, algae and/or fungi.

Yet another object of the invention is a method for inhibiting the corrosive action of aqueous solutions of hydrogen peroxide on metal surfaces, said method comprising adding at least one quaternary ammonium compound selected from the group consisting of quaternary ammonium carbonates and quaternary ammonium bicarbonates to said aqueous solution of hydrogen peroxide.

Preferably, the quaternary ammonium carbonates and bicarbonates to be employed in the above method for inhibiting the corrosive action of aqueous solutions of hydrogen peroxide on metal surfaces have the formulas

(R ¹ R ² R ³ RV) ₂ CO ² (I) and R ¹ R ² R ³ R ⁴ N ⁺ HCO ₃ (II),

wherein R ¹ is benzyl or C ₈ _ ₂₀ alkyl;

R ² is selected from the group consisting of Ci_ ₂₀ alkyl and -[(CH ₂ ) ₂ -O] _« -R ⁵ , wherein n is an integer from 1 to 20 and R ⁵ is selected from the group consisting of hydrogen, phenyl and alkyl- substituted phenyl; and R ³ and R ⁴ are independently Ci_ ₂₀ alkyl.

The weight ratio of quaternary ammonium compound(s) to hydrogen peroxide in the above method is from 1 : 100 to 2: 1 , preferably from 1 :20 to 1 :1 and most preferably from 1 :5 to 1 :1.

The following non-limiting examples will illustrate the invention. All concentrations in percent or ppm are by weight, unless otherwise noted.

Example 1 Hydrogen Peroxide Stability in the Presence of Didecyldimethylammonium Bicarbonate/- Carbonate

Table 1

Quat = didecyldimethylammonium carbonate/bicarbonate

RT = room temperature

The accuracy of the analytical method used is ±3% on a relative basis

Example 2

Efficacy of Didecyldimethylammonium Bicarbonate/Carbonate with Hydrogen Peroxide against P. aeruginosa

Materials/Results :

All solutions were diluted in water of 400 ppm hardness and all concentrations were expressed in ppm. Each of the solutions was tested in 4 replicates as described below. The numbers in Table 2 below indicate the number of "positive" cells or ineffective disinfection of 4 replicates. Various contact times noted on the tables were evaluated.

Procedure:

Flat bottom microplate wells were inoculated with 15 μL each of a suspension of 10% P. aeruginosa + 5% fetal bovine serum in a saline solution, 4.5 ^χ 10 ⁷ cfu/mL using a Quadra Tower 400 Series High Throughput apparatus (Tomtec Inc., Hamden, CT). The plates were dried with cover open for 40 minutes at 36 °C. Then, 120 μL of each test substance was transferred from the deep-well block to the test wells. The test organisms were exposed to the test substance for different contact times, after which the substances were removed with the Quadra and 150 μL of modified AOAC Letheen neutralizer + 0.5% Na thiosulfate/growth broth was added to each well. The microplates were incubated at 36 °C for 24 hours and scored for growth/no growth.