Synergistic disinfection enhancement

Abstract

An aqueous disinfectant solution comprising peroxyacetic acid and a surfactant such as a polyoxyethylene alkyl ether phosphate, (polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether) or cocoamidopropylamino oxide. The solution is preferably adjusted to provide a pH in the range 5-8 by a pH adjusting agent such as a phosphate buffer; hydroxide; carbonate; bicarbonate; a combination of carbonate and hydroxide; or a combination of carbonate and bi carbonate.

Claims

1. An aqueous disinfectant solution comprising: 0.1 to 0.3 wt % of peroxyacetic acid; hydrogen peroxide; and 0.23 to 0.3 wt % of a surfactant; and wherein the solution has a pH in the range of 6-7.

2. An aqueous disinfectant solution according to claim 1 further comprising acetic acid and wherein the solution has a pH in the range of 6-6.5.

3. An aqueous disinfectant solution according claim 2 wherein the surfactant is selected from the group consisting of polyoxyethylene alkyl ether phosphates, polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether and cocoamidopropylamino oxide.

4. An aqueous disinfectant solution according to claim 1 wherein the solution is adjusted to provide a pH in the range of 6-7 by a pH adjusting agent selected from the group consisting of a phosphate buffer; hydroxide; carbonate; bicarbonate; a combination of carbonate and hydroxide; and a combination of carbonate and bicarbonate.

5. An aqueous disinfectant solution according claim 4 wherein the surfactant is selected from the group consisting of polyoxyethylene alkyl ether phosphates, polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether and cocoamidopropylamino oxide.

6. An aqueous disinfectant solution according to claim 1 wherein the ratio of hydrogen peroxide:peroxyacetic acid is 5:1 or greater.

7. An aqueous disinfectant solution according claim 6 wherein the surfactant is selected from the group consisting of polyoxyethylene alkyl ether phosphates, polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether and cocoamidopropylamino oxide.

8. An aqueous disinfectant solution according to claim 1 wherein the ratio of hydrogen peroxide:peroxyacetic acid is 10:1 or greater.

9. An aqueous disinfectant solution according to claim 1 wherein the ratio of hydrogen peroxide:peroxyacetic acid is 15:1 or greater.

10. An aqueous disinfectant solution according to claim 1 wherein the ratio of hydrogen peroxide:peroxyacetic acid is 30:1 or greater.

11. An aqueous disinfectant solution according claim 10 wherein the surfactant is selected from the group consisting of polyoxyethylene alkyl ether phosphates, polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether and cocoamidopropylamino oxide.

12. An aqueous disinfectant solution according to claim 1 wherein the surfactant is a non-ionic surfactant.

13. An aqueous disinfectant solution according claim 1 wherein the surfactant is selected from the group consisting of polyoxyethylene alkyl ether phosphates, polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether and cocoamidopropylamino oxide.

14. An aqueous disinfectant solution according to claim 1 wherein the surfactant is a polyoxyethylene alkyl ether phosphate.

15. An aqueous disinfectant solution according to claim 1 further including a corrosion inhibitor.

16. An aqueous disinfectant solution according to claim 15 wherein the corrosion inhibitor is a benzotriazole.

17. An aqueous disinfectant solution according claim 15 wherein the surfactant is selected from the group consisting of polyoxyethylene alkyl ether phosphates, polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether and cocoamidopropylamino oxide.

18. An aqueous disinfectant solution according to claim 1 further including an antifoaming agent.

19. An aqueous disinfectant solution according claim 18 wherein the surfactant is selected from the group consisting of polyoxyethylene alkyl ether phosphates, polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether and cocoamidopropylamino oxide.

20. An aqueous disinfectant solution according to claim 1, wherein hydrogen peroxide is present in an amount ranging from 0.05 to 1 wt % of the composition.

21. An aqueous disinfectant solution comprising: 0.1 to 0.3 wt % of peroxyacetic acid; hydrogen peroxide; and 0.23 to 0.3 wt % of a surfactant selected from the group consisting of amine oxide surfactants, quaternary ammonium surfactants, and polyoxyethylene alkyl ether phosphates; and wherein the solution has a pH in the range of 6-7.

22. An aqueous disinfectant solution according to claim 21, wherein hydrogen peroxide is present in an amount ranging from 0.05 to 1 wt % of the composition.

23. A method of disinfection of an article comprising contacting an article with the aqueous disinfectant solution according to claim 1.

24. A method according to claim 23 wherein the method is carried out in a temperature range of 15-40° C.

25. A method according to claim 23 wherein the method is carried out in a temperature range of 20-35° C.

26. A method according to claim 23 wherein the method is carried out at ambient temperature.

Description

DESCRIPTION

(1) Peroxyacetic acid is generated by the addition of acetic acid to a peroxidising agent such as hydrogen peroxide or a peroxy salt. The most common and inexpensive method used to generate peroxyacetic acid is to use a combination of acetic acid and aqueous hydrogen peroxide, in which case the peroxyacetic acid is in equilibrium with a number of other species as shown:
H.sub.2O.sub.2+CH.sub.3CO.sub.2HCH.sub.3CO.sub.3H+H.sub.2O

(2) As mentioned, the native ratios found in such equilibrated mixtures typically provide peroxyacetic acid:acetic acid:hydrogen peroxide in a ratio of 1:1.5:5. That is, the ratio of the active disinfectant species, peroxyacetic acid and hydrogen peroxide, in such systems is typically around 1:5.

(3) Peroxyacetic acid can also be generated from solid peroxide precursors such as sodium perborate, sodium percarbonate, carbamide peroxide (urea peroxide) or potassium fluoride peroxosolvate in combination with acetic acid to generate peroxyacetic acid. Although slightly more expensive than the acetic acid/hydrogen peroxide approach, these sources of peroxyacetic acid are seen as desirable since they do not include large amounts of hydrogen peroxide, which is regarded as a less potent biocide than peroxyacetic acid.

(4) In some cases, solid peroxide precursors can be used in combination with hydrogen peroxide/acetic acid systems.

(5) Regardless of how it is produced, the pH of peroxyacetic acid is very low, around 2.8. Such a low pH means that it is highly corrosive. Such a low pH is also fundamentally incompatible with systems that are to be used in intimate contact with patients. This means that in order to be used in sensitive medical instruments, it is generally desired that pH is controlled by way of a pH adjusting agent such as a basic agent or buffer. An ideal pH range that will result in minimal corrosion with maximum compatibility for human contact is between about pH 5.5 and pH 7, more particularly between about pH 5.5 and pH 6.5.

(6) Phosphate buffers can be used to control the pH of peroxyacetic acid systems. However, other common bases, such as hydroxide or carbonate, have also been used to adjust the pH of peroxyacetic acid.

(7) In buffers comprising hydrogen carbonate anions and hydroxide anions, the molar ratio of hydrogen carbonate:hydroxide is about 0.9:1 to about 1.1:1, more preferably about 1:1. In the preferred sodium salt form, the w:w ratio of hydrogen carbonate:hydroxide is from about 2.5:1 to 2:1, more preferably about 2.3:1, or the ratio of carbonate:hydroxide is from about 2.9:1 to 2.4:1, more preferably about 2.65:1.

(8) In buffers comprising hydrogen carbonate anions and carbonate anions, the molar ratio of hydrogen carbonate:carbonate is about 0.15:1 to about 0.25:1, more preferably about 0.18:1. In the preferred sodium salt form, the w:w ratio of hydrogen carbonate:carbonate is from about 0.1:1 to about 0.2:1, more preferably about 0.14:1.

(9) Although the term “buffer” is used, it is important to understand that the components need not form a true buffer system—The important consideration is the adjustment of the peroxyacetic acid to a pH of between 6.3 and 6.8 in the final working solution. It has been found that the buffer is most advantageously added in an amount to keep the pH between 5.5 and pH 7 and if possible around 6-6.5.

(10) Surprisingly, the present applicant has found that the biocidal activity of peroxyacetic acid, even against spores, is potentiated by the presence of a surfactant. This is the case even at very low concentrations. This effect is also observed to take place in solutions that are adjusted to physiological pH's.

(11) It is surprising that the presence of a surfactant can also increase the biocidal efficacy of such disinfectant solutions.

(12) The effects of adding a wide range of surfactants to buffered peracetic acid were tested against B. subtilis.

(13) Amine oxide surfactants tested included cocamidopropylamine oxide (RCONH(CH.sub.2).sub.3N(CH.sub.2).sub.2.fwdarw.O) where R is a cocoalkyl group; dodecyldimethylamine oxide (C.sub.14H.sub.31N.fwdarw.O); ((CH.sub.2).sub.13(CH.sub.2).sub.2N.fwdarw.O); or ((CH.sub.2).sub.12-18(CH.sub.2).sub.2N.fwdarw.O).

(14) Non-ionic surfactants tested included Triton X-100, (polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether) or Tween-80 (polyethlyene (20) sorbitan monooleate).

(15) Cationic surfactants tested included quaternary ammonium compounds such as benzalkonium chloride or hexadecylpyridinium bromide.

(16) Phosphate ester based anionic surfactants tested included polyoxyethylene alkyl ether phosphates, such as those sold by Croda under the trade name Monafax M1214 or Multitrope 1214; phosphate esters (mono- and/or diester of phosphoric acid with aliphatic alcohols of chain length C.sub.1-C.sub.22 and/or aliphatic diols and/or aliphatic polyols of chain length C.sub.2-C.sub.22) such as Hordaphos 1306 or Hordaphos MDGB from Clariant, which is a diester of phosphoric acid with butanol and ethylene glycol respectively; and Excellene T5 NF which is a blend of ethylhexylphosphate ester and alcohol ethoxylate phosphate ester potassium salts, available from Whewell chemical manufacturers.

(17) The surfactants were mainly, but not in every case, tested in combination with a phosphate buffer. The exact concentrations of peracetic acid, pH, and initial populations of B. subtilis were not standardised across the whole range of surfactants tested, so it is not possible to state quantified relative efficacies. However, each surfactant was tested against an appropriate control system (differing only in the absence of the surfactant) so it is possible to conclusively state that in every case an increased efficacy was noted when a surfactant was added. The results of the study were not optimised.

(18) A particularly preferred class of surfactants which gave improved performance were phosphate based anionic surfactants, particularly polyoxyethylene alkyl ether phosphates, such as those sold by Croda under the trade name Monafax M1214 or Multitrope 1214. The results for this class of compound were investigated further and are shown in the examples below.

EXAMPLES

(19) Test Method

(20) The test method employed and described below is typical of all the test methodology used in the present invention to determine biological loads.

(21) The working solution was tested against spores of the appropriate organism at room temperature. Media was TSB+1% Na-thiosulfate+10% Tween 80+1 ml Catalase.

(22) The test method involved taking a 9 ml sample and adding 1 ml culture (with 5% horse serum) and then incubating at the desired temperature if necessary. 1 ml of the incubated sample was then removed at each time point and neutralized with 9 ml neutralizer. The resultant was diluted with saline, plated out and the plates incubated at 37° C. for 48 hr. The results were then able to be expressed in terms of a log reduction. As is usual in the art, a log reduction is a log.sub.10 reduction. A 4 log reduction means 1 in 10.sup.4 organisms survived, 5 log reduction corresponds to 1 in 10.sup.5 organisms surviving and so on. High level disinfection is widely defined and understood as a reduction of 6 log or greater, than is, no more than 1 in 1,000,000 microorganisms survives the process.

(23) Results

(24) Table 1 shows the biocidal effect against Bacillus subtilis spores achieved by adding a surfactant to a pH controlled aqueous peracetic acid solution (0.2%) that contained also acetic acid and hydrogen peroxide. It can be seen that the addition of the surfactant had only a very minimal effect upon the pH of the solution, only changing it by around 0.0 to 0.5 pH units.

(25) However, the effect upon the biocidal efficacy was quite dramatic. The addition of just 0.25% surfactant led to between an increase in biocidal efficacy of between 1 and 1.6 log.sub.10, that is, the surfactant increased the efficacy of peracetic acid by between 10 and about 40-fold.

(26) Table 2 illustrates similar experiments to those in table 1, with the exception that the wt % of peroxy acetic acid was reduced to 0.1%. The surfactant at 0.30% did not exert any adverse effect upon the pH of the mixture.

(27) However, the effect upon the biocidal efficacy was still quite significant. The addition of 0.30% surfactant led to between an increase in biocidal efficacy of between 0.4 and 0.9 log.sub.10, that is, the surfactant increased the efficacy of peracetic acid by between 3 and about 8-fold.

(28) Table 3 shows the biocidal effect against Candida albicans spores obtained by adding a surfactant to a pH controlled aqueous peracetic acid solution (0.05%) that contained also acetic acid and hydrogen peroxide. It can be seen that the addition of the surfactant had only a very minimal effect upon the pH of the solution, changing it from around 0.0 to 0.5 pH units.

(29) Again, the effect upon the biocidal efficacy was quite dramatic. The addition of just 0.23% surfactant led to between an increase in biocidal efficacy of between 0.7 and 1.6 log.sub.10, that is, the surfactant increased the efficacy of peracetic acid by between 5 and about 40-fold.

(30) Table 4 shows the fungicidal effect against Aspergillus niger of adding a surfactant to a pH controlled aqueous peracetic acid solution (0.2%) that contained also acetic acid and hydrogen peroxide. It can be seen that the addition of the surfactant had only a very minimal effect upon the pH of the solution.

(31) However the effect upon the fungicidal efficacy was quite dramatic. The addition of just 0.30% surfactant led to between an increase in biocidal efficacy of between 0.5 and 0.9 log.sub.10, that is, the surfactant increased the efficacy of peracetic acid by between 3 and about 8-fold.

(32) In summary, a surprising increase in the efficacy of peroxy acetic acid was achieved by the addition of a surfactant. Surfactants are well known not to have any significant biocidal activity in their own right.

(33) TABLE-US-00001 TABLE 1 Sporicidal efficacy of biocides on the base of peroxyacetic acid against Bacillus subtilis spores (ATCC 19659) at room temperature (suspension test) pH of working solution Log.sub.10 Reduction Compo- Wt % of without with 0.25% Exposure without with 0.25% sition Ingredient ingredient Surfactant Surfactant* time (min) Surfactant Surfactant* I peroxyacetic acid 0.2 6.56 6.51 3 4.7 5.7 acetic acid 0.3 H2O2 1 phosphate buffer II peroxyacetic acid 0.2 6.57 6.53 3 5.5 5.6 acetic acid 0.3 H2O2 1 basic buffer (NaOH) III peroxyacetic acid 0.2 6.52 6.52 3 5.0 6.2 acetic acid 0.3 H2O2 1 carbonate buffer I (NaHCO.sub.3 + NaOH) IV peroxyacetic acid 0.2 6.52 6.50 3 4.7 6.2 acetic acid 0.3 H2O2 1 carbonate buffer II (Na.sub.2CO.sub.3 + NaHCO.sub.3) *Surfactant was Monafax M1214 which also contained 0.01% Antifoaming component AF 86/013 (from Basildon Chemical Company Ltd)

(34) TABLE-US-00002 TABLE 2 Sporicidal efficacy of biocides on the base of peroxyacetic acid against Bacillus subtilis spores (ATCC 19659) at room temperature (suspension test) pH of working solution Log.sub.10 Reduction Compo- Wt % of without with 0.30% Exposure without with 0.30% sition Ingredient ingredient Surfactant Surfactant* time (min) Surfactant Surfactant* I peroxyacetic acid 0.1 6.40 6.39 5 1.4 1.8 acetic acid 0.15 H2O2 0.05 phosphate buffer II peroxyacetic acid 0.1 6.45 6.41 5 1.1 1.7 acetic acid 0.15 H2O2 0.05 basic buffer (NaOH) III peroxyacetic acid 0.1 6.41 6.41 5 1.5 2.4 acetic acid 0.15 H2O2 0.05 carbonate buffer I (NaHCO.sub.3 + NaOH) IV peroxyacetic acid 0.1 6.44 6.39 5 1.5 2.4 acetic acid 0.15 H2O2 0.05 carbonate buffer II (Na.sub.2CO.sub.3 + NaHCO.sub.3) *Surfactant was Monafax M1214 which also contained 0.01% Antifoaming component AF 86/013 (from Basildon Chemical Company Ltd)

(35) TABLE-US-00003 TABLE 3 Biocidal efficacy of biocides on the base of peroxyacetic acid against Candida albicans (ATCC 10231) at room temperature (suspension test) pH of working solution Log.sub.10 Reduction Compo- Wt % of without with 0.23% Exposure without with 0.23% sition Ingredient ingredient Surfactant Surfactant* time (min) Surfactant Surfactant* I peroxyacetic acid 0.05 6.60 6.58 0.5 5.3 6.9 acetic acid 0.075 H2O2 0.025 phosphate buffer II peroxyacetic acid 0.05 6.60 6.56 0.5 5.4 6.9 acetic acid 0.075 H2O2 0.025 basic buffer (NaOH) III peroxyacetic acid 0.05 6.53 6.55 0.5 5.8 6.9 acetic acid 0.075 H2O2 0.025 carbonate buffer I (NaHCO.sub.3 + NaOH) IV peroxyacetic acid 0.05 6.52 6.55 0.5 6.2 6.9 acetic acid 0.075 H2O2 0.025 carbonate buffer II (Na.sub.2CO.sub.3 + NaHCO.sub.3) *Surfactant was Monafax M1214 which also contained 0.01% Antifoaming component AF 86/013 (from Basildon Chemical Company Ltd)

(36) TABLE-US-00004 TABLE 4 Fungicidal efficacy of biocides on the base of peroxyacetic acid against Aspergillus niger (ATCC 16404) at room temperature (suspension test) pH of working solution Log.sub.10 Reduction Compo- Wt % of without with 0.30% Exposure without with 0.30% sition Ingredient ingredient Surfactant Surfactant* time (min) Surfactant Surfactant* I peroxyacetic acid 0.1 6.16 6.16 2 1.0 1.9 acetic acid 0.15 H2O2 0.05 phosphate buffer II peroxyacetic acid 0.1 6.25 6.13 2 0.9 1.4 acetic acid 0.15 H2O2 0.05 basic buffer (NaOH) III peroxyacetic acid 0.1 6.13 6.21 2 1.2 2.1 acetic acid 0.15 H2O2 0.05 carbonate buffer I (NaHCO.sub.3 + NaOH) IV peroxyacetic acid 0.1 6.24 6.18 2 1.9 2.6 acetic acid 0.15 H2O2 0.05 carbonate buffer II (Na.sub.2CO.sub.3 + NaHCO.sub.3) *Surfactant was Monafax M1214 which also contained 0.01% Antifoaming component AF 86/013 (from Basildon Chemical Company Ltd)