GB2626063A

GB2626063A - Disinfectant formulation

Info

Publication number: GB2626063A
Application number: GB2315914.8A
Authority: GB
Inventors: Stoker Davy
Original assignee: MICRONCLEAN Ltd
Current assignee: MICRONCLEAN Ltd
Priority date: 2023-01-06
Filing date: 2023-10-18
Publication date: 2024-07-10
Also published as: GB202315914D0; WO2024147000A1

Abstract

An aqueous disinfectant formulation suitable for sterilisation by exposure to ionising radiation comprising 0.05-60 wt.% of at least one biocidal active, 0.1-20% pH modifier or buffer and up to 1% radical scavenger. A sterile aqueous disinfectant formulation comprising the aqueous disinfectant formulation exposed to ionising radiation, a method for preparing the formulation comprising adding at least one biocidal active to water, adding a pH modifier and adding a radical scavenger, a method of preparing a sterile aqueous disinfectant formulation comprising preparing the aqueous disinfectant formulation, placing the formulation in a container, hermetically sealing the container and sterilising the container by exposure to ionising radiation, a method of preparing a sterile cleaning article comprising preparing the aqueous disinfectant formulation, assembling the cleaning article, treating it with the formulation, placing the treated article in packaging, hermetically sealing the packaging and sterilising by exposure to ionising radiation, and a sterile cleaning article comprising the aqueous disinfectant formulation on a storage medium, where the sterile cleaning article is contained within a hermetically sealed packaging which have together been sterilised by exposure to ionising radiation are also included. The formulation may further comprise an alcohol, surfactant, antimicrobial metal active, or complexing agent.

Description

Disinfectant Formulation

Field of invention

The present invention relates to disinfectant formulations, methods for preparing disinfectant formulations, and methods for preparing sterile disinfectant formulations and sterile cleaning articles containing disinfectant formulations. In particular the present invention relates to disinfectant formulations suitable for irradiation sterilisation, and irradiation sterilised disinfectant formulations for cleanroom disinfectants and the preparation of sterile cleaning articles for use in cleanrooms.

Background art

Cleanrooms are widely used in scientific research in life sciences and electronics as well as in the production of electronic components such as semiconductor devices, battery technology, aerospace engineering and other products which are highly sensitive to contamination. A constant airflow of highly filtered, clean and (in some cases) sterile air with a very low concentration of airborne particulate matter is typically provided within the cleanroom to prevent damage or contamination of sensitive work within the room. Depending on the application, exhaust air may also be cleaned, filtered and disinfected to prevent or limit the escape of hazardous material (e.g. radioactive material or harmful microbes) from the cleanroom. Cleanrooms are -dependent on application -typically maintained at either positive pressure (to prevent any leaks causing an ingress of untreated air) or negative pressure (to prevent any leaks causing egress of potentially contaminated air).

Staff working within a cleanroom are often required to wear protective clothing to prevent micro-organisms present on human skin and hair from contaminating the cleanroom environment. Staff, materials and equipment typically enter and leave through airlocks and 10 may be subjected on entry/exit to an air shower to remove any contaminants.

Providing a sterile environment within a cleanroom is particularly important where the cleanroom is utilised in biotechnology or pharmaceutical research or production. UV light can be used to disinfect air within the cleanroom, but chemical disinfectants also play an important role, particularly for maintaining sterile surfaces. A variety of chemical disinfectants are available for use in cleanrooms, with more common disinfectants including alcohol-based disinfectants (e.g. aqueous solutions of ethanol or isopropyl alcohol), diamine-based disinfectants, quaternary ammonium based disinfectants and sporicides. Different disinfectants are often rotated to prevent the build-up of resistant organisms. Different disinfectants have different breadths of biocidal activity and rotation also ensures that all target micro-organisms can be effectively destroyed.

Given the different breadth of different disinfectants and the requirement for a sterility to be maintained at all times within the cleanroom, it is often necessary to ensure that disinfectant products (e.g. solutions or wipes) themselves are sterile so that they do not inadvertently contaminate the cleanroom. Sterile disinfectants are produced either using a completely aseptic production method (which is expensive and challenging to maintain for high-volume production) or more commonly by subjecting disinfectants to ionising radiation (such as gamma, x-ray or electron beam radiation) after production.

However ionising radiation can have a negative impact on the efficacy of biocidal actives within the disinfectant For example, gamma irradiation of aqueous solutions leads to the formation of hydroxyl radicals which can then attack and degrade biocidal actives. Quaternary ammonium based biocidal actives may be susceptible to damage from hydroxyl radicals through hydrogen abstraction from the beta carbon to yield an alkene decomposition product, or hydroxyl radicals may directly attack the alpha carbon in an SN2 mechanism.

Summary of the Invention

The present invention seeks to provide disinfectant formulations which are suitable for or 10 have been sterilised by exposure to ionising radiation without significantly impacting their biocidal activity.

Viewed from a first aspect the present invention provides an aqueous disinfectant formulation suitable for sterilisation by exposure to ionising radiation (e.g. gamma radiation), comprising-005 wt.% to 60 wt % of at least one biocidal active; 0.1 wt % to 20 wt.% of a pH modifier/buffer; and up to 1% wt.% of a radical scavenger.

Reactive oxygen species formed within the solution as a result of exposure to ionising radiation during the sterilisation process may include water radiolysis products such as hydrogen peroxide, hydrogen radicals, hydroxyl radicals and hydrogen superoxide. These reactive oxygen species readily react with organic compounds including many biocidal actives. The radical scavenger advantageously quenches free radicals and other reactive oxygen species formed within the solution as a result of exposure to ionizing radiation. This prevents or limits degradation of the biocidal active(s) by the free radicals, thus preventing (or limiting) loss in the biocidal activity of the formulation as a result of the sterilisation process.

In this context, "aqueous disinfectant formulation" should be interpreted to mean that the formulation contains water as a solvent, although water may not be the only solvent in the 30 formulation. For example, other water miscible solvents may be present with a wt.% less than, equal to or greater than that of water.

Due to the nature of radical quenching mechanisms, the minimum quantity of the radical scavenger required is very low (<0.01 wt.%) to be effective. Thus the formulation may comprise between 0.001 wt.% and 1 wt.% of a radical scavenger. Preferably the formulation comprises between 0.01 wt.% and 0.1 wt.% of a radical scavenger.

Any compound capable of scavenging radicals and other reactive oxygen species (e.g. superoxide) which is stable under ambient conditions and is at least partially soluble in aqueous solutions may be used as a radical scavenger. The radical scavenger may be selected from a group consisting of nitrate salts (e.g. sodium nitrate, potassium nitrate, or silver nitrate), nitrite salts, t-butanol, hydrochloric acid, sodium hydroxide, ascorbic acid, cysteine, thiourea, glutathione, N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES), tris(hydroxymethyl)aminoethane (Tris), ethylene glycol, melatonin, and 2-mercaptoethanol.

The formulation may comprise one biocidal active, two biocidal actives, or three or more biocidal actives. Preferably the formulation comprises one or two biocidal actives.

The one or more biocidal actives may each be a quaternary ammonium compound (QAC/Quat), a quaternary ammonium salt or a triamine. The one or more biocidal actives may be independently selected from a group consisting of benzalkonium chloride (BAC) or other halide salts, didecyldimethylammonium chloride (DDAC) or other halide salts, alkyldimethylbenzylammonium chloride (ADBAC) or other halide salts, alkyl dimethyl ethylbenzyl ammonium chloride (ADEBAC) or other halide salts, dimethyloctadecylp(trimethoxysilyl)propyllammonium chloride or other halide salts, benzyl-C12-18-alkyldimethyl, salts with 1,2-benzisothiazol-3(2H)-one 1,1-dioxide (1:1) (ADBAS), and N(3-ami nopropy1)-N-dodecylpropane-1,3-di amine).

Preferably the formulation comprises between 0.1 wt.% and 50 wt.% of the one or more biocidal actives. Particularly preferably the formulation comprises between 1 wt.% and 25 30 wt.% of the one or more biocidal actives.

The formulation may comprise between 0.1 wt.% and 20 wt.% alcohol. Preferably the formulation comprises between 1 wt.% and 20 wt.% alcohol Particularly preferably the formulation comprises between 2 wt.% arid 10 wt.% alcohol Even more preferably the formulation comprises between 4 wt.% and 6 wt.% alcohol.

The alcohol may be a simple monoalcohol (i.e. have a general formula of Ca-Li-ElOH). The alcohol may be selected from a group consisting of methanol, ethanol, isopropanol and IIbutanol. Preferably the alcohol is ethanol.

The alcohol advantageously enhances solubility of other components within the formulation, which may have low solubility in water alone. The amount and type of alcohol within the formulation can be tailored for optimum solubility of different biocidal actives and/or radical scavengers. The alcohol itself may also provide a small additional biocidal effect.

Certain alcohols (including simple monoalcohols such as methanol and ethanol) can themselves act as weak radical scavengers. The formulation may thus comprise 0.1 wt.% to 20 wt.% of an alcohol in addition to between 0.01 wt.% and 1 wt.% of a radical scavenger (i.e. the radical scavenger is different to the alcohol, although the radical scavenger may also be an alcohol). Thus reference within this specification to "radical scavenger" should be interpreted to exclude any simple monoalcohol (i.e. alcohols having the general formula CnI12"+10H; for example methanol (n=1); ethanol (n=2); isopropanol (n=3) and n-butanol (n=4)) which is present in an amount greater than 1 wt.%, regardless of whether the alcohol has radical scavenging capability.

The formulation may comprise between 1 wt.% and 20 wt.% of a pH modifier/buffer. The pH modifier/buffer advantageously ensures that the pH of the formulation remains within an acceptable range for safe use and to ensure that biocidal actives remain soluble and in a usable (i.e. active) form. Preferably the pH of the formulation is between pH 7 and pH 13.

Even more preferably the pH of the formulation is between pH 8 and pH 10. Preferably the composition comprises between 2 wt.% and 10 wt.% of a pH modifier/buffer. Even more preferably the formulation comprises between 4 wt.% and 6 wt.% pH modifier/buffer.

The pH modifier/buffer may be any pH modifier/buffer which is soluble in aqueous solutions and is capable of adjusting the pH of the formulation to the required range and/or acting as a pH buffer within the required pH range. Preferably the pH modifier/buffer is selected from a group consisting of ethanolamine, diethanolamine, triethanolamine, lecithin and morpholinc.

The formulation may further comprise between 0.1 wt.% and 10 wt.% of a surfactant. Preferably the formulation comprises between 2 wt.% and 8 wt.% (e.g. 5 wt.%) of a 10 surfactant.

The surfactant is preferably a non-ionic surfactant. The surfactant may be selected from a group consisting of alcohol ethoxylates (e.g 2-(04(2-ethylhexyl)poly-oxy)poly-propan-2-yl)oxy)ethanol) and fatty alcohol ethoxylates.

The formulation may further comprise an antimicrobial metal active selected from a group consisting of aluminium, bismuth, cobalt, copper, gold, iron, manganese, molybdenum, nickel, platinum, silver, titanium, zirconium and zinc. Preferably the antimicrobial metal active is selected from the group consisting of copper, silver, and zinc.

The antimicrobial metal active may be present in the formulation either in a colloidal form (i.e. metallic particles) or in an ionic form (i.e. as a soluble metal salt). Where the metal is present in a colloidal form, the particles preferably have a size of between 100 nm and 200 nm. The formulation preferably contains between 0.001 wt.% and 3 wt.% of antimicrobial metal active.

The formulation may further comprise a complexing agent The complexing agent can advantageously improve the solubility of antimicrobial metals (where present). The complexing agent can also act to sequester deactivating ions, such as iron and calcium, which can negatively impact the efficacy of active biocides, such as quaternary ammonium salts. The complexing agent may be a chelating agent such as ethylenediaminetetraacetic acid (EDTA). The formulation may comprise between 0.1% and 5% of the complexing agent. Preferably the complexing agent is selected from a group consisting of ethylenediaminetetraacetic acid, trisodiumnitrilotriacetate, phosphates, citrates, zeolites, diethylenetriamine pentaacetate and egtazic acid Viewed from a second aspect the present invention provides a sterile aqueous disinfectant formulation comprising an aqueous disinfectant formulation as hereinbefore described, wherein the aqueous disinfectant formulation has been sterilised by exposure to ionising radiation.

The ionising radiation may be gamma radiation, electron beam radiation or x-ray radiation Preferably the ionising radiation is gamma radiation. A dosage level of ionising radiation may be up to 75 kGy. Preferably a dosage level of ionising radiation is in the range of 15 to 60 kGy. Even more preferably a dosage level of ionising radiation is in the range of 25 to 50 kGy (e.g. about 35 kGy) Viewed from a third aspect the present invention provides a method for preparing an aqueous disinfectant formulation suitable for sterilisation by exposure to ionising radiation, comprising the steps of: adding one or more biocidal actives to water to form a concentrated aqueous biocidal solution; adding a pH modifier/buffer to the concentrated aqueous biocidal solution; adding a radical scavenger to the concentrated aqueous biocidal solution; and diluting the concentrated aqueous biocidal solution to the required concentration.

The at least one biocidal active, pH modifier/buffer and radical scavenger may be as hereinbefore defined. The method may further comprise the step of adding one or more of an alcohol; a surfactant; an antimicrobial metal active and a complexing agent as hereinbefore defined The concentrated aqueous biocidal solution may be diluted with water, one or more water 30 miscible alcohols, or a mixture of water and one or more water miscible alcohols.

Viewed from a fourth aspect the present invention provides a method for preparing a sterile aqueous disinfectant formulation, comprising the steps of: preparing an aqueous disinfectant formulation as hereinbefore described; then placing the aqueous disinfectant formulation inside a container and hermetically sealing the resultant filled container; then sterilising the filled container by exposure to ionising radiation.

Viewed from a fifth aspect the present invention provides a method for preparing a sterile cleaning article (e.g for use in a cleanroom), comprising the steps of: preparing a disinfectant formulation as hereinbefore described; then assembling a cleaning article and treating it with the disinfectant formulation; then placing the treated cleaning article in a packaging and hermetically sealing the packaging to maintain its integrity; then sterilising the packaged cleaning article by exposure to ionising radiation.

The cleaning article may be any article which may be used to apply or dispense the disinfectant formulation For example the cleaning article may be a bottle, a spray bottle, a wipe or a mop.

The ionising radiation may be gamma radiation, electron beam radiation or x-ray radiation. Preferably the ionising radiation is gamma radiation. A dosage level of ionising radiation may be up to 75 kGy. Preferably a dosage level of ionising radiation is in the range of 15 to 60 kGy. Even more preferably a dosage level of ionising radiation is in the range of 25 to 50 kGy (e.g. about 35 kGy).

Viewed from a sixth aspect the present invention provides a sterile cleaning article comprising: a storage medium; a disinfectant formulation as hereinbefore described provided in or on the storage medium; wherein the sterile cleaning article is contained within a hermetically sealed packaging; wherein the storage medium; the disinfectant formulation and the hermetically sealed packaging have together been sterilised by exposure to ionising radiation. :30

The ionising radiation may be gamma radiation, electron beam radiation or x-ray radiation. Preferably the ionising radiation is gamma radiation. A dosage level of ionising radiation may be up to 75 kGy. Preferably a dosage level of ionising radiation is in the range of 15 to 60 kGy. Even more preferably a dosage level of ionising radiation is in the range of 25 to 50 kGy (e.g. about 35 kGy) The storage medium may be a container (e.g. a bottle) or may be an absorbent material such as a wipe, mop, pad or other fabric, cloth or paper material Viewed from a seventh aspect the present invention provides a method for disinfecting a surface in a cleanroom, comprising the steps of: cleaning the surface, for example using a neutral detergent; treating the surface with a first disinfectant formulation as hereinbefore described one or more times over a first time period; then treating the surface with a second disinfectant formulation as hereinbefore described one or more times over a second time period; wherein the first and second disinfectant formulations each contain a different set of one or more biocidal actives.

The first time period is preferably between 1 week and 2 weeks. The second time period is preferably between 1 week and 2 weeks There may be a gap between the first and second time periods. The gap may be up to 1 20 week, between 1 week and 2 weeks or between 1 week and 3 weeks.

Detailed description of preferred embodiments of the invention Example 1: DDAC and BAC disinfectant formulation Preparation g of a commercially available 50 wt.% solution in water of didecyldimethylammonium chloride (DDAC 50) was added to 50 g of a commercially available 50 wt.% solution in water of benzalkonium chloride (BAC 50). To the resultant mixture was added 10 g 2-((1- ((2-ethylhexyl)poly-oxy)poly-propan-2-yl)oxy)ethanol surfactant, 50 g ethanol and 50 g ethanolamine. The resultant solution was then diluted with 739.8 ml water and 0.2 g sodium nitrate was added to the solution with stirring until dissolved, to give DDAC and BAC disinfectant formulation 1 suitable for sterilisation by exposure to ionising radiation, shown in Table 1. The pH of disinfectant formulation 1 was between pH8 and p119.

Table 1: Composition of Disinfectant Formulation 1 Component Role Content (wt.%) DDAC Biocide 5 BAC Biocide 2.5 2-41-42-ethylhexyl)poly-oxylpoly-propan-2-ylloxylethanol Surfactant 1 Ethanol Solvent 5 Ethanolamine Buffer 5 Sodium nitrate Radical scavenger 0.02 Water Solvent 81.48 TOTAL 100 Example 2: DDAC and triamine disinfectant formulation Preparation 10 g of dodecyl dipropylene triamine was added to 100 g of a commercially available 50 wt.% solution in water of didecyldimethylammonium chloride (DDAC 50). To the resultant mixture was added 10 g 2-(042-ethylhexyl)poly-oxy)poly-propan-2-yl)oxy)ethanol surfactant, 50 g ethanol and 50 g ethanolamine. The resultant solution was then diluted with 779.8 ml water and 0.2 g sodium nitrate was added to the solution with stirring until dissolved, to give DDAC and triamine disinfectant formulation 2 suitable for sterilisation by exposure to ionising radiation, shown in Table 2. The pH of disinfectant formulation 2 was between pH8 and p119.

Table 2: Composition of Disinfectant Formulation 2 Component Role Content (wt.%) DDAC Biocide 5 Dodecyl dipropylene triamine Biocide 1 2-((14(2-ethylhexyl)poly-oxy)poly-propan -2-y1)oxy)eth anol Surfactant 1 Ethanol Solvent 5 Ethanol amine Buffer 5 Sodium nitrate Radical scavenger 0.02 Water Solvent 82.98 TOTAL 100 Example 3: DDAC and ADEBAC disinfectant formulation Preparation g alkyl (C12-14) dimethyl ethylbenzyl ammonium chloride (ADEBAC) was added to 100 g of a commercially available 50 wt.% solution in water of didecyldimethylammonium chloride (DDAC 50). To the resultant mixture was added a total of 10 g of one or more 02-H 2-13 branched or linear alcohol ethoxylates, 508 of isopropyl alcohol and 508 diethanolamine. The resultant solution was then diluted with 739.8 ml water and 0.2 g potassium nitrate was added to the solution with stirring until dissolved, to give DDAC and BAC disinfectant formulation 3 suitable for sterilisation by exposure to ionising radiation, shown in Table 3. The pH of disinfectant formulation 3 was between pH8 and pH9.

Table 3: Composition of Disinfectant Formulation 3 Component Role Content (wt.%) DDAC Biocide 5 ADEBAC Biocide 5 Mixture of Alcohols, C12-13, branched and linear, ethoxylated Surfactant 1 IPA Solvent 5 Di ethanol amine Buffer 5 Potassium nitrate Radical scavenger 0.02 Water Solvent 78.98 TOTAL 100 Example 4: DDAB and triam ne disinfectant formulation Preparation g of dodecyl dipropylene triamine was added to 100 g of a commercially available 50 wt.% solution in water of didecyldimethylammonium bromide (DDAB 50). To the resultant mixture was added 10 g of a linear fatty acid alcohol (C12/C14; CAS No, 900292-0), 50 g methanol and 50 g ethanolamine. The resultant solution was then diluted with 769.8 ml water and 0.2 g silver nitrate was added to the solution with stirring until dissolved, to give DDAB and triamine disinfectant formulation 4 suitable for sterilisation by exposure to ionising radiation, shown in Table 4. The pH of disinfectant formulation 4 IS was between pH8 and pH9.

Table 4: Composition of Disinfectant Formulation 4 Component Role Content (wt.%) DDAB Biocide 5 Dodecyl dipropylene triamine Biocide 2 Linear fatty alcohol (C12/14) CAS:9002-92-0 Surfactant 1 Methanol Solvent 5 Ethanol amine Buffer 5 Silver Nitrate Radical scavenger 0.02 Water Solvent 81.98 TOTAL 100 Efficacy tests Example formulations 1 and 2 were tested both before and after 25-50 kGy gamma irradiation for their fungicidal activity against Aspergil his braSiliellSiS according to the EN13697:2015+A1:2019 test protocol. Comparative formulations 5 and 6 (which are the same as formulations 1 and 2 respectively with the exception that they do not contain any sodium nitrate radical scavenger) were also tested according to the same protocol before and after gamma irradiation.

A. brasiliensis was added to 0.3 WI bovine albumin and the resultant solution was applied onto a stainless steel metal surface. The sample surface was left to air-dry and then the test IS formulation was applied to the sample surface and left for IS minutes. The sample was then submerged in a neutraliser solution of lecithin and Tween 80 (polysorbate 80). A sample of the neutraliser solution was then taken, plated and incubated for 3 days. A temperature of between 18 °C and 25 °C was maintained throughout the test. The number of A. braciliensis microbes recovered from the plate was then measured and compared to a control sample (following the same procedure but with water applied to the sample surface rather than the test formulation). The log reduction (extent to which the formulation is capable of reducing the number of microbes, where >Log 6 kill corresponds to a loss of > 99.9999 %) of each sample was then determined and is shown in Table 5 In addition to measuring efficacy, the concentration of biocidal actives in formulations 1 and 2, and comparative formulations 5 and 6 were measured by HPLC (C18 column (100 x 3.2 mm 3-5 uun), flow rate 1 ml/min, mobile phase (MeCN/Phosphate buffered water 0.2%, 50:50) or (unbuffered methanol:water 50:50)) before irradiation and after irradiation, and the change in biocidal active concentration was determined to show the effect of gamma radiation on the biocidal active.

The percentage loss (decrease) in biocidal active concentration after irradiation for each formulation is shown in Table 5, Table 5: results of efficacy tests (EN13697:2015+A1:2019) and change in active concentration measured by HPLC of formulations 1 and 2 and comparative formulations 5 and 6 before and after gamma irradiation Formulation Efficacy against Aspergillus brasiliensis before Irradiation Efficacy against Aspergillus brasiliensis after Irradiation HPLC of actives drop after irradiation Formulation 1 >Log 6 kill >Loub 6 kill DDAC = 4% loss BAC = 10% loss Formulation 2 > Log 6 kill >Log 6 kill DDAC = 3% loss Triamine = 8% loss Comparative Formulation 5 >Log 6 kill Log 2.1 kill DDAC = 22% loss BAC = 100% loss Comparative Formulation 6 >Log 6 kill Log 1.8 kill DDAC = 24% loss Triamine = 52% loss As shown in Table 5, where there is no radical scavenger present (i.e. for comparative formulations 5 and 6) then there is a significant drop in biocidal activity following irradiation. Before irradiation, comparative formulations 5 and 6 are effective against greater than 99.9999% of A. brasiliensis, with this dropping to around 99% after irradiation. Samples post irradiation also show a loss of 22-24% of DDAC; 52% triamine and 100% of BAC biocidal actives where no radical scavenger is present.

In comparison, formulations 1 and 2 show no significant drop in efficacy following gamma irradiation, with efficacy tests showing >log 6 kill (i.e. > 99.9999% of target microbes are killed) both before and after gamma irradiation. Although the amount of biocidal active present in formulations 1 and 2 is lower following irradiation, the loss is significantly lower than in comparative formulations 5 and 6.

Thus the presence of a radical scavenger within formulations effectively limits degradation of biocidal actives, preventing the loss in antimicrobial efficacy following gamma irradiation. Thus, where disinfectant formulations 1 and 2 are added to a cleaning article such as a wipe, bottle, spray bottle, or mop, the cleaning article can be packaged in hermetically sealed packaging and sterilised using ionising radiation such as gamma radiation without causing significant loss in antimicrobial activity.

Claims

Claims 1. An aqueous disinfectant formulation suitable for sterilisation by exposure to ionising radiation comprising: 0.05 wt.% to 60 wt.% of at least one biocidal active; 0.1 wt.% to 20 wt.% of a pH modifier/buffer; and up to 1% wt.% of a radical scavenger.
2. The aqueous disinfectant formulation of claim 1, wherein the formulation comprises 10 between 0.01 wt.% and 0.1 wt.% of the radical scavenger.
3. The aqueous disinfectant formulation of claim 1 or claim 2, wherein the radical scavenger is selected from a group consisting of nitrate salts, nitrite salts, t-butanol, hydrochloric acid, sodium hydroxide, ascorbic acid, cysteine, thiourea, glutathione, N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES), tris(hydroxymethyl)aminoethane (Iris), ethylene glycol, melatonin, and 2-mercaptoethanol.
4. The aqueous disinfectant formulation of any preceding claim, wherein the at least one biocidal active is/are independently selected from a group consisting of benzalkonium chloride (BAC) or other halide salts, didecyldimethylammonium chloride (DDAC) or other halide salts, alkyldimethylbenzylammonium chloride (ADBAC) or other halide salts, alkyl dimethyl ethylbenzyl ammonium chloride (ADEBAC) or other halide salts, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride or other halide salts, benzyl-C12-18-alkyldimethyl, salts with 1,2-benzisothiazol-3(2H)-one 1,1-dioxide (1:1) (ADBAS), and N-(3-aminopropy1)-N-dodecylpropane-1,3-diamine).
5. The aqueous disinfectant formulation of any preceding claim, wherein the formulation comprises between 5 wt.% and 25 wt.% of the at least one biocidal active.
6. The aqueous disinfectant formulation of any preceding claim, wherein the formulation further comprises between 0.1 wt.% and 20 wt.% of an alcohol.
7. The aqueous disinfectant formulation of claim 6, wherein the alcohol is selected from a group consisting of methanol, ethanol, isopropanol and n-butanol
8. The aqueous disinfectant formulation of any preceding claim, wherein the pH modifier/buffer is selected from a group consisting of ethanolamine, diethanolamine, triethanolamine, lecithin and morpholine.
9. The aqueous disinfectant formulation of any preceding claim, wherein the formulation 10 further comprises between 0.1 wt.% and 10 wt.% of a surfactant.
10. The aqueous disinfectant formulation of claim 9, wherein the surfactant is selected from a group consisting of alcohol ethoxylates and fatty alcohol ethoxylates.
11 The aqueous disinfectant formulation of any preceding claim, wherein the formulation further comprises between 0.001 wt.% and 3 wt.% of antimicrobial metal active.
12. The aqueous disinfectant formulation of claim 11, wherein the antimicrobial metal active is selected from a group consisting of copper, silver, and zinc.
13. The aqueous disinfectant formulation of any preceding claim, wherein the formulation further comprises between 0.1% and 5% of a complexing agent selected from a group consisting of ethylenediaminetetraacetic acid, trisodiumnitrilotriacetate, phosphates, citrates, zeolites, diethylenetriamine pentaacetate and egtazic acid
14. A sterile aqueous disinfectant formulation, comprising an aqueous disinfectant formulation according to any preceding claim, wherein the aqueous disinfectant formulation has been sterilised by exposure to ionising radiation.
15. The sterile aqueous disinfectant formulation of claim 14, wherein the aqueous disinfectant formulation has been exposed to ionising radiation at a dosage level in the range of 15 to 60 kGy.
16. A method for preparing an aqueous disinfectant formulation suitable for sterilisation by exposure to ionising radiation, comprising the steps of adding one or more biocidal actives to water to form an aqueous biocidal solution; adding a pH modifier/buffer to the aqueous biocidal solution; and adding a radical scavenger to the aqueous biocidal solution.
17. The method of claim 16, further comprising the step of diluting the aqueous biocidal 10 solution to a required concentration.
18. The method of claim 16 or 17, further comprising the step of adding an alcohol to the concentrated aqueous biocidal solution.
19 The method of claim 16, 17 or 18, further comprising the step of adding a surfactant to the concentrated aqueous biocidal solution.
20. A method for preparing a sterile aqueous disinfectant formulation, comprising the steps of: preparing an aqueous disinfectant formulation according to the method of any one of claims 16 to 19; placing the prepared aqueous disinfectant formulation inside a container and hermetically sealing the resultant filled container; and sterilising the filled container by exposing the filled container to ionising radiation.
21 The method of claim 20, wherein a dosage level of the ionising radiation is in the range of 15 to 60 kGy.
22. A method for preparing a sterile cleaning article, comprising the steps of: preparing an aqueous disinfectant formulation according to claims 1 to 13; assembl ng a cleaning article and treating it with the aqueous disinfectant formulation; placing the treated cleaning article in a packaging and hermetically sealing the packaging; sterilising the packaged cleaning article by exposure to ionising radiation.
23 A sterile cleaning article comprising: a storage medium; an aqueous disinfectant formulation according to claims 1 to 13 provided in or on the storage medium; wherein the sterile cleaning article is contained within a hermetically sealed packaging; and wherein the storage medium; the disinfectant formulation and the hermetically sealed packaging have together been sterilised by exposure to ionising radiation.