Disinfectant Composition

Abstract

A composition comprising: (a) a hydrogen peroxide source (b) an acetyl source (c) a peracetic acid bleachable dye
wherein, in solution, colour generated by said peracetic acid bleachable dye is substantially discharged when a biocidally effective concentration of peracetic acid is achieved.

Claims

1. A composition comprising: (a) a hydrogen peroxide source (b) an acetyl source (c) a peracetic acid bleachable dye wherein, in solution, colour generated by said peracetic acid bleachable dye is substantially discharged when a biocidally effective concentration of peracetic acid is achieved.

2. A composition according to claim 1 comprising in addition a substantially bleach stable dye.

3. A composition according to claim 1 wherein the biocidally effective concentration is greater than 0.14% w/w of peracetic acid of the solution.

4. A composition according to claim 1 wherein the composition is in powder form.

5. A composition according to claim 1 wherein the solution comprises water as solvent.

6. A composition according to claim 1 wherein the peracetic acid bleachable dye is a 1-arylazo-2-hydroxynaphthyl dye.

7. A composition according to claim 6 wherein the peracetic acid bleachable dye is selected from the group consisting of Amaranth (C.I. 16185), Ponceau 4R (C.I. 16255), FD&C Yellow 6 (C.I. 15985), any other 1-arylazo-2-hydroxynaphthyl dye, and combinations thereof.

8. A composition according to claim 7 wherein the peracetic acid bleachable dye is Amaranth (C.I. 16185).

9. A composition according to claim 2 wherein the substantially bleach stable dye is selected from the group consisting of Acid Blue 182, Acid Blue 80, Direct Blue 86, Acid Green 25 (C.I. 61570) and combinations thereof.

10. A composition according to claim 9 wherein the substantially bleach stable dye is Acid Blue 182 (C.I. 61570)

11. A composition according to claim 1 wherein the hydrogen peroxide source is selected from the group consisting of sodium perborate, sodium percarbonate, urea peroxide, povidone-hydrogen peroxide, calcium peroxide, hydrogen peroxide solution, and combinations thereof.

12. A composition according to claim 11 wherein the hydrogen peroxide source is sodium percarbonate.

13. A composition according to claim 1 wherein the acetyl donor is selected from the group consisting of tetraacetylethylenediamine (TAED), N-acetyl caprolactam, N-acetyl succinimide, N-acetyl phthalimide, N-acetyl maleimide, pentaacetyl glucose, octaacetyl sucrose, acetylsalicylic acid, tetraacetyl glycouril, and combinations thereof.

14. A composition according to claim 13 wherein the acetyl donor is tetraacetylethylenediamine (TAED).

15. A composition according to claim 1 in addition comprising one or more of an acidifying agent, a wetting agent, a pH buffering agent, a sequestering agent, a flow modifier, a perfume, other additives, or combinations thereof.

16. A composition comprising a combination of: (i) a first part comprising a hydrogen peroxide source; and (ii) a second part comprising a mixture of an acetyl source and a peracetic acid bleachable dye; wherein, in solution, colour generated by said peracetic acid bleachable dye is substantially discharged when a biocidally effective concentration of peracetic acid is achieved.

17. The composition of claim 1 wherein a powder blend of the hydrogen peroxide source, acetyl source and peracetic acid bleachable dye is not classifiable as a Dangerous Good.

18. The composition of claim 1 wherein a powder blend of the hydrogen peroxide source, acetyl source and peracetic acid bleachable dye is not classifiable as a self-reactive solid.

19. A process of preparing a solution having biocidal properties, which process comprises dissolving the composition of claim 1 in a solvent and waiting for the colour generated by said peracetic acid bleachable dye to substantially discharge.

20. A biocidal composition comprising a solution of a hydrogen peroxide source, an acetyl source and a peracetic acid bleachable dye, wherein colour generated by said peracetic acid bleachable dye has substantially discharged.

21. The use of a composition of claim 1 for disinfecting an object or surface requiring disinfection.

22. A method of disinfecting an object or surface requiring disinfection, which method comprises preparing a solution of the composition of claim 1 and applying the solution to said object or surface after the colour generated by said peracetic acid bleachable dye has substantially discharged.

23. A method of disinfecting an object or surface requiring disinfection, which method comprises applying to said object or surface the biocidal composition of claim 20.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0044] FIG. 1 shows the structural formulae of the various dyes described.

[0045] FIG. 2 is a graph showing the bleaching kinetics of Amaranth dye in the presence of either hydrogen peroxide, or a mixture of hydrogen peroxide and peracetic acid.

[0046] FIG. 3 is a graph showing the bleaching kinetics of Amaranth dye, Ponceau 4R and Sunset Yellow dye in the presence of a mixture of hydrogen peroxide and peracetic acid.

[0047] FIG. 4 shows a series of photographs taken at 30 second intervals illustrating the colour changes produced by an embodiment of the composition of the invention on dissolution in tap water.

[0048] FIG. 5 is a graph showing the variation in concentrations of hydrogen peroxide and peracetic acid with time following dissolution of an embodiment of the composition of the invention in tap water.

[0049] FIG. 6 is a graph showing the variation in concentrations of peracetic acid with time following dissolution of differing weights of an embodiment of the composition of the invention in tap water.

[0050] FIG. 7 is a graph showing the time taken to discharge the red colour of a solution of the composition of the invention, in tap water.

[0051] FIG. 8 is a graph showing the peracetic acid (PAA) concentration generated for various samples of sachets of the composition of the invention, dissolved in tap water, at 10 minutes, 20 minutes and 30 minutes.

DETAILED DESCRIPTION OF THE INVENTION

[0052] According to the present invention, there is provided a composition which, on dissolution in a solvent, generates a biocidally effective disinfectant solution comprising peracetic acid and hydrogen peroxide. The composition comprises a system to produce a visual indication of the formation of the peracetic acid. The indication is provided by a dye that is rapidly bleached in the presence of peracetic acid, whilst being substantially unaffected by the presence of hydrogen peroxide. An optional second dye may be incorporated, wherein the second dye is not substantially bleached by either peracetic acid or hydrogen peroxide.

[0053] Preferably the composition of the invention is provided in a powder. Preferably the composition of the invention is dissolved in water.

[0054] When the composition of the invention is presented in powdered form, it may also contain a flow modifier to prevent clumping of the powder prior to dispersion and dissolution into the solvent, and a wetting agent to assist in the rapid dispersion and dissolution of the acetyl source into solution, preferably at ambient temperature.

[0055] The composition of the invention may also be packaged into a soluble sachet wherein the entire sachet and contents is placed into a solvent, preferably water, to generate the disinfectant, thus mitigating occupational exposure to the potentially harmful powder precursor.

[0056] In a preferred embodiment of the invention, there is provided a composition comprising a hydrogen peroxide source, an acetyl donor, an acidifying agent, and a first dye that is bleached in the presence of peracetic acid, but not hydrogen peroxide. In another embodiment, a second dye that is substantially bleach stable may also be included in the composition of the invention.

[0057] In a particularly preferred embodiment of the invention, the first dye is a dye that is bleached in the presence of a biocidal concentration of peracetic acid, and the second dye is a dye that is bleached after several hours in the presence of a biocidal concentration of peracetic acid. The presence of the first dye in the solution acts as a visual indication that the solution has not yet achieved the desired biocidal concentration of peracetic acid. Once the colour due to the first dye is discharged, the colour due to the second dye is left to provide an aesthetically pleasing colouration. When the composition of the invention is in powder form, it is dissolved in a solvent, preferably water, to form the peracetic acid-containing solution.

[0058] The composition of the invention may also optionally contain wetting agents, sequestering and chelating agents, and other ingredients, such as bleach stable fragrances, corrosion inhibitors, powder flow modifiers, rheology modifiers etc.

[0059] The composition of the invention is prepared by combining the ingredients together. In a preferred embodiment, the composition of the invention is in powder form.

[0060] In an alternative embodiment, the composition of the invention may be presented in kit form, where the hydrogen peroxide source, part (a), is stored separately to a mixture of the acetyl source and peracetic acid bleachable dye, parts (b) and (c). In use, the hydrogen peroxide source is mixed with the acetyl source/peracetic acid bleachable dye mixture, in solution.

[0061] In use, the composition of the invention is dissolved in a solvent and to produce a broad spectrum disinfectant solution which is efficacious against spores, bacteria fungus, virus, yeasts and moulds. The disinfectant solution is particularly efficacious against spore forming bacteria such as Clostridium difficile. The disinfectant may be used to disinfect surfaces, including hard surfaces, and instruments.

[0062] Typically, the composition of the invention contains the following ingredients:

Hydrogen Peroxide Source

[0063] Examples of a hydrogen peroxide source which may be used in the composition of the invention include, but are not limited to, sodium perborate, sodium percarbonate, urea peroxide, povidone-hydrogen peroxide, calcium peroxide, and combinations thereof.

[0064] A dilute solution of hydrogen peroxide in water may also be used as a hydrogen peroxide source, if a two part product is intended. In this case, the hydrogen peroxide solution should preferably contain less than 8% hydrogen peroxide, thus negating classification as a Class 5.1 Dangerous Good. The dilute solution of hydrogen peroxide may also contain additional stabilising ingredients, such as 1-hydroxyethylidene-1,1,-diphosphonic acid, (sold as Dequest 2010), or other strongly chelating additives, such as ethylenediamine tetraacetic acid (EDTA). The peroxide solution may optionally contain pH buffering agents.

Acetyl Donors

[0065] Examples of acetyl donors which may be used in the composition of the invention include, but are not limited to, tetraacetylethylenediamine (TAED), N-acetyl caprolactam, N-acetyl succinimide, N-acetyl phthalimide, N-acetyl maleimide, penta-acetyl glucose, octaacetyl sucrose, acetylsalicylic acid, tetraacetyl glycouril, and combinations thereof. Preferably the acetyl donor is a solid.

[0066] A preferred acetyl donor is TAED, more particularly, a micronized grade of TAED, such as B675, obtainable from Warwick Chemicals (UK).

Acidifying Agents

[0067] Examples of acidifying agents which may be used in the composition of the invention include, but are not limited to, citric acid, monosodium citrate, disodium citrate, tartaric acid, monosodium tartrate, sulfamic acid, sodium hydrogen sulphate, monosodium phosphate, oxalic acid, benzoic acid, benzenesulfonic acid, toluenesulfonic acid and combinations thereof. Preferably the acidifying agent is a solid.

Peracetic Acid Bleachable Dyes

[0068] The ‘first dye’ is a peracetic acid bleachable dye. Examples of peracetic acid bleachable dyes which may be used in the composition of the invention include Amaranth (C.I. 16185), Ponceau 4R (C.I. 16255), FD&C Yellow 6 (C.I. 15985), any other 1-arylazo-2-hydroxynaphthyl dye, and combinations thereof.

[0069] The peracetic acid bleachable dye is preferably relatively rapidly bleached in the presence of peracetic acid, but not hydrogen peroxide. By “relatively rapidly” is meant that the colour of the dye is bleached within about 10 minutes. When the colour generated by the peracetic acid bleachable dye in solution is substantially discharged, the peracetic acid has reached a biocidally effective concentration in the solution. By “substantially discharged” is meant that the colour in the solution, generated by the peracetic acid bleachable dye, is entirely, or almost entirely, discharged.

[0070] In a particularly preferred embodiment of the composition of the invention, the first dye is Amaranth Red (C.I. 16185) and the second dye is C.I. Acid Blue 182. Surprisingly, it has been found that in this embodiment, Amaranth Red is bleached rapidly by only peracetic acid, whilst being relatively resistant to bleaching by hydrogen peroxide. This is a particularly unexpected finding, as Amaranth Red is used as an indicator in a commercially available powder-based detergent called Virkon, a product produced and marketed by Antec Ltd. In the case of Virkon, as long as the red colouration due to Amaranth is present, the Virkon solution is still actively biocidal. According to the Virkon product brochure, “VIRKON 1% solutions are stable for 7 days but should be discarded when the pink colour fades”.

[0071] Virkon is comprised of a mixture of potassium monoperoxysulfate, sodium chloride, sulfamic acid, plus other ingredients such as surfactants, perfumes, as well as Amaranth. According to a background document produced by Antec, on dissolution in water, the Virkon powder mix undergoes the Haber-Willstatter Reaction, producing a mix of biocidal species including the potassium monoperoxysulfate, chlorine, N-chlorosulfamic acid, hypochlorous acid. The document goes on to state that Virkon contains “a pink dye (amaranth colour, EEC No. 123). In addition to being aesthetically pleasing, this serves a very practical purpose—it indicates whether the VIRKON solution is active. In its oxidised form, it is pink but when the solution starts to lose its activity it reverts to its colourless reduced form. VIRKON solutions must always be replaced if the colour starts to fade”. In other words, the pink-red colouration due to Amaranth is present whilst the active oxidatively biocidal species are also present, with the colour only fading as the oxidative biocides become depleted.

[0072] Conversely, in the present invention, colour depletion of the disinfectant solution indicates that an effective biocidal concentration of peracetic acid has been achieved.

Substantially Bleach Stable Dyes

[0073] The second dye which may optionally be included in the composition of the invention is a substantially bleach stable dye. It is recognised that peracetic acid will be capable of bleaching most dyes, and therefore reference to a “substantially bleach stable” dye is to be taken as meaning that the dye is capable of imparting colour to the peracetic acid/hydrogen peroxide solution for at least 2 hours, preferably about 4 to 6 hours, at room temperature.

[0074] Examples of substantially bleach stable dyes which may be used in the composition of the invention include, but are not limited to, Acid Blue 182, Acid Blue 80, Direct Blue 86, Acid Green 25 (C.I. 61570) and combinations thereof.

[0075] In a particularly preferred embodiment of the composition of the invention, the first dye is Amaranth Red (C.I. 16185) and the second dye is C.I. Acid Blue 182. In this embodiment of the invention, the colour of the solution upon dissolution of the composition of the invention is red, generated by the Amaranth. The red colour discharges at around 5-7 minutes, at which time the peracetic acid is at a biocidally effective concentration, leaving a blue colour, generated by the Acid Blue 182. The blue colour is aesthetically pleasing, and has the added benefit of making the solution more visible when disinfecting a surface or object.

Wetting Agent

[0076] When the composition of the invention is in a powder formulation, a wetting agent may be included in the composition to facilitate dispersion of the acetyl source into solution on initial dilution, thus assisting in its dissolution. The wetting agent is preferably comprised of a solid surfactant capable of lowering the surface tension of the solvent, preferably water, thus allowing the acetyl source to wet and disperse. Preferably, the acetyl source is TAED and, in the absence of a wetting agent, a highly micronized grade of TAED such as B675 will tend to float on the surface of the solvent, and thus be slow to dissolve, resulting in slow production of peracetic acid. Examples of suitable wetting agents which may be used in the composition of the invention include, but are not limited to, sodium dodececyl sulphate, sodium alkylbenzenesulphonate, Pluronic PE6800, Hyamine 1620 etc, and combinations thereof.

pH Buffering Agents

[0077] Optionally, a pH buffer may be included in the composition of the invention to reduce the variation of pH with time. Since the formation of peracetic acid from the acetyl source, preferably TAED, requires the pH to be at, or above, the pKa of peracetic acid (8.2), the pH of the solution should be buffered between 8.00 and 9.00, preferably between 8.00 and 8.40. Suitable pH buffers which may be included in the composition of the invention include, but are not limited to, phosphate, borate, bicarbonate, TAPS (3-{[tris(hydroxymethyl)methyl]amino}propanesulfonic acid), Bicine (N,N-bis(2-hydroxyethyl)glycine), Tris (tris(hydroxymethyl)methylamine), Tricine (N-tris(hydroxymethyl)methylglycine) and combinations thereof.

Sequestering Agents

[0078] Optionally, the composition of the invention may include ingredients capable of complexing metal ions such as calcium and magnesium, thus negating any adverse effect from the use of hard water, as well as metal ions such as iron, manganese, copper etc which are capable of catalysing the decomposition of peroxides, and which also may be present in tap water. Examples of chelating and sequestering agents which may be used in the composition of the invention include, but are not limited to, sodium citrate, citric acid, phosphoric acid, sodium tripolyphosphate, EDTA, NTA, etc and combinations thereof.

Flow Modifiers

[0079] A flow modifier may be added to improve the flow characteristics of the composition of the invention, when in a powder formulation. This is particularly useful if the powder is intended for supply in a unidose package (eg an individual sachet or water soluble pouch), as good powder flow will allow accurate dosing of the blended powder into the individual packs. Examples of powder flow modifiers which may be used in the composition of the invention include, but are not limited to, fumed silica, precipitated silica, micronized polyethylene glycol 6000, micronized lactose, talc, magnesium stearate etc, and combinations thereof.

[0080] In a preferred example, the flow modifier is a hydrophilic fumed silica, for example Aeosil 200 (Evonik Industries).

[0081] It may also possible to achieve good flow improvements using a precipitated silica such as Tixosil 38, although the precipitated silica grades are less preferred as they produce a strong haze in the final disinfectant solution, by virtue of the larger particle size of the precipitated form over the fumed form.

Perfumes

[0082] Optionally, the composition of the invention may also contain perfumes to mask the odour of peracetic acid. The perfume used should preferably be stable to hydrogen peroxide and peracetic acid.

[0083] In a preferred embodiment of the present invention, the acetyl donor is TAED, the hydrogen peroxide source is sodium percarbonate, the first dye is Amaranth Red, and the composition is in a powder formulation, which is dissolved in water. On initial mixing of the powder formulation with tap water, at ambient temperatures, a deep red cloudy solution is formed by the rapid dissolution of the Amaranth Red dye and the suspension of undissolved TAED. Over the course of approximately 5-10 minutes, the TAED dissolves into the water, and the red colouration is discharged as peracetic acid is generated by the reaction of the TAED with hydrogen peroxide produced by dissolution of the sodium percarbonate. After about 7-10 minutes, the solution will be clear, and all of the red colouration discharged.

[0084] In another preferred embodiment, a second dye that is substantially bleach stable may also be included in the composition of the invention. Preferably the substantially bleach stable dye bleaches over the course of 4-6 hours, along with the Amaranth. A preferred second dye, which is slowly bleached, is C.I. Acid Blue 182.

EXAMPLES

[0085] Example 1

Stability of Amaranth

[0086] The relative stability of Amaranth in the presence of hydrogen peroxide, and also a mixture of hydrogen peroxide and peracetic acid at the intended use pH of between 8.00 and 8.50 was demonstrated by preparing two solutions, one without peracetic acid and one with peracetic acid, and following the loss of absorbance of Amaranth at 482nm in a spectrophotometer.

Example 2

Determination of Hydrogen Peroxide and Peracetic Acid Concentrations

[0087] A dual titration procedure was utilised to determine the concentrations of hydrogen peroxide and peracetic acid in a single sample.

[0088] A 10 ml aliquot of the sample was placed in a 250 ml Erlinmeyer flask, along with 25 ml of 0.5 M sulphuric acid. The solution was then titrated against 0.1 M potassium permanganate solution until a very pale pink colouration was evident in the solution for 30 seconds. Approximately 0.2 g of potassium iodide was then added, and the resultant iodine titrated against 0.1 M sodium thiosulphate, using a starch solution as an indicator.

[0089] The concentration of hydrogen peroxide was calculated from the permanganate titration, and the concentration of the peracetic acid was calculated from the thiosulfate titration.

Equations

[0090] 1. Permanganate titration

MnO.sub.4.sup.−+8H.sup.++5e.sup.−.fwdarw.Mn.sup.2++4H.sub.2O

H.sub.2O.sub.2.fwdarw.O.sub.2+2H.sup.++2e.sup.−

Overall

2MnO.sub.4.sup.31+6H.sup.++5H.sub.2O.sub.2.fwdarw.2Mn.sup.2++8H.sub.2O+5O.sub.2 [0091] 2. Iodometric titration

2KI+H.sub.2SO.sub.4.fwdarw.2HI+K.sub.2SO.sub.4

CH.sub.3CO.sub.3H+2HI.fwdarw.I.sub.2+CH.sub.3CO.sub.2H+2H.sub.2O

I.sub.2+2S.sub.2O.sub.3.sup.2−.fwdarw.S.sub.4O.sub.6.sup.2−+2I.sup.31

Example 3

Investigating Flow Characteristics of TAED

[0092] Some micronized TAED B675 (Warwick Chemicals) was taken, and rubbed through a 125 micron sieve to break up or remove any agglomerated lumps of material. Approximately 50 g of the sieved TAED was then placed into a glass funnel with a spout with a diameter of 4.75 mm. The end of the spout was held 10 cm above a white ceramic tile. The TAED was allowed to run out of the funnel to form a conical pile on the ceramic tile. The funnel was tapped with a spatula to encourage material to flow out if necessary.

[0093] Once all of the powder had been discharged from the funnel, the conical pile of material was photographed, and the angle of the apex of the cone of material determined. The apex angle (also referred to as the angle of repose) was found to be 66°.

[0094] A second 50 g lot of TAED B675 was then taken, and 0.50 g of Aerosil 200 (Evonik Industries) added. The material was stirred together for several minutes using a spatula, and then passed through a 125 micron sieve to break up or remove any agglomerated lumps of material. Once sieved, the powder blend was stirred together for a further 5 minutes to produce a homogenous mix.

[0095] The blend was then placed into a glass funnel with a spout with a diameter of 4.75 mm. The end of the spout was held 10 cm above a white ceramic tile. The TAED was allowed to run out of the funnel to form a conical pile on the ceramic tile. The funnel was tapped with a spatula to encourage material to flow out.

[0096] Once all of the powder had been discharged from the funnel, the conical pile of material was photographed, and the angle of the apex of the cone of material determined. The apex angle (also referred to as the angle of repose) was found to be 110°.

[0097] The flatter conical pile of material containing the Aerosil clearly shows that the TAED containing the Aerosil has a significantly improved flow.

Example 4

[0098] A solution of sodium percarbonate (3.68 g), anhydrous citric acid (1.41 g), sodium tripolyphosphate (0.58 g) and anhydrous monosodium phosphate (0.07 g) in 250 ml of deionised water was prepared. The pH of the resultant solution was found to be 8.22. Once all the ingredients were dissolved, 250 ml of a solution of Amaranth Red (0.034/L) was added. The solution was mixed, and an aliquot taken and placed in a glass cuvette, and the change of absorbance at 482 nm followed in a spectrophotometer over a period of 80 minutes (see FIG. 2).

[0099] Three 10 ml aliquots of the solution were then taken and titrated against potassium permanganate as described above in order to determine the hydrogen peroxide concentration. The final composition of the solution is shown in Table 1.

Example 5

[0100] A solution of TAED (2.06 g), sodium percarbonate (3.68 g), anhydrous citric acid (1.04 g), sodium tripolyphosphate (0.58 g) and anhydrous monosodium phosphate (0.07 g) in 250 ml of deionised water was prepared. The pH of the resultant solution was found to be 7.96. Once all the ingredients were dissolved, 250 ml of a solution of Amaranth Red (0.034/L) was added. The solution was mixed, and an aliquot taken and placed in a glass cuvette, and the change in absorbance at the λ.sub.max of Amaranth measured over 40 minutes using a spectrophotometer (see FIG. 2). Three 10 ml aliquots were then taken and titrated as described below to determine the concentrations of hydrogen peroxide and peracetic acid. The final composition of the solution is shown in Table 1.

TABLE-US-00001 TABLE 1 Final solution compositions Example 4 Example 5 Sodium percarbonate 3.68 3.68 TAED 0.00 2.06 Citric acid 1.41 1.04 Sodium tripolyphosphate 0.58 0.58 Monosodium phosphate 0.07 0.07 DI water 500 500 Amaranth 0.0085 0.0085 pH 8.22 7.96 Hydrogen peroxide 0.215% w/v 0.113% w/v content Peracetic acid content 0.000% w/v 0.228% w/v

[0101] As can be seen in FIG. 2, the Amaranth is rapidly bleached in the presence of peracetic acid, but only slowly bleached in the presence of hydrogen peroxide alone.

[0102] Ponceau 4R and FD&C Yellow 6 (dyes with similar chemical structures to Amaranth) were similarly assessed, as described in Examples 6-8. The structures of these dyes are given in FIG. 1 Error! Reference source not found.

Examples 6-8

[0103] A solution of sodium percarbonate (4.97 g), TAED (2.73 g), citric acid (1.38 g), sodium tripolyphosphate (0.77 g) and monosodium phosphate (0.09 g) were dissolved in 250 ml of DI water. Once dissolved, three 40 ml aliquots of the solution were taken. The first aliquot was added to 40 ml of a solution of Amaranth in water (dye concentration=0.034 g/L). The second aliquot was added to 40 ml of a solution of Ponceau 4R in water (dye concentration=0.034 g/L), whilst the third aliquot was added to 40 ml of a solution of FD&C Yellow 6 in water ((dye concentration=0.034 g/L).

[0104] The compositions of these final solutions are shown in Table 2.

TABLE-US-00002 TABLE 2 Example 6 Example 7 Example 8 Sodium percarbonate 0.975% 0.975% 0.975% TAED 0.535% 0.535% 0.535% Citric acid 0.271% 0.271% 0.271% Sodium 0.151% 0.151% 0.151% tripolyphosphate Monosodium 0.018% 0.018% 0.018% phosphate DI water 98.049%  98.049%  98.049%  Amaranth 0.0017%  — — Ponceau 4R — 0.0017%  — FD&C Yellow 6 — 0.0017% 

[0105] As can be seen in FIG. 3, the Amaranth dye is bleached at a significantly faster rate than Ponceau 4R or FD&C Yellow 6, despite their structural similarities.

Example 9

Dye Premix

[0106] A mixture of 78.00 g of TAED B675 (Warwick Chemicals), 17.00 g Amaranth dye and 5.00 g of C.I. Acid Blue 182 dye were mixed and ground together using a pestle and mortar to give a homogenous brownish powder. Once mixed, the dye premix blend was stored in a well-sealed container prior to use.

Example 10

[0107] 54.55 g of TAED B675, 1.00 g of the dye-TAED premix from Example 9, 1.32 g of powdered sodium dodecyl sulphate and 0.60 g Aerosil 200 (a hydrophilic fumed silica available from Evonik) were mixed together, and passed through a 125 micron sieve to remove and break up any aggregated material. After sieving, mixing was continued to produce a homogenous powder.

[0108] To the sieved material was added 0.49 g tetrasodium EDTA, 28.00 g of anhydrous citric acid, 99.32 g of sodium percarbonate, 15.50 g of sodium tripolyphosphate and 1.80 g of anhydrous monosodium phosphate. The powders were then mixed thoroughly to produce a homogenous, free-flowing powder. The full composition of the powder blend is shown in Table 3, along with the function of each ingredient.

[0109] Whilst the loading of the fumed silica in the TAED in Example 3 (1%) was in line with the manufacturer's recommendations for use rate, it was found that it was only necessary to add 1% of the TAED weight of the Aerosil 200 to the powder blend. This equates to 0.3% of the overall blend weight. At this level, the Aerosil will produce only a very slight haze in the final disinfectant solution.

TABLE-US-00003 TABLE 3 Ingredient % w/w Function Sodium percarbonate 49.03 Hydrogen peroxide source TAED B675 27.31 Acetyl donor Citric acid 13.82 Acidifier Sodium tripolyphosphate 7.65 Sequestrant and pH modifier Monosodium phosphate 0.89 pH modifier Sodium dodecyl sulfate 0.65 Surfactant and wetting agent Aerosil 200 0.30 Flow modifier Tetrasodium EDTA 0.24 Chelating agent Amaranth 0.084 PAA bleachable Colourant Acid Blue 182 0.025 PAA stable Colourant

[0110] A solution of the disinfectant was prepared by dissolving 7.50 g of the powder blend into 500 ml of artificial hard water containing 340 ppm CaCO.sub.3 (prepared as described in SOP Number: MB-22-00: Standard Operating Procedure for Disinfectant Sample Preparation, published by the US Environmental Protection Agency Office of Pesticide Programs, and hereafter referred to as AOAC Hard Water). The solution was stirred at room temperature. The red colour due to the Amaranth was observed to be discharged at around 5-7 minutes, leaving a blue solution (see FIG. 4). 10 ml aliquots taken at regular intervals after 10 minutes, and the pH were also recorded. The aliquots were titrated as described earlier to determine hydrogen peroxide and peracetic acid concentration.

[0111] As may be seen in FIG. 5 Error! Reference source not found., the concentration of peracetic acid increases rapidly, reaching its maximum value at around 20 minutes. After this point, a slow decay of the peracetic acid concentration over several hours is seen.

[0112] Interestingly, if the concentration of powder dissolved into the water is increased, whilst the maximum peracetic acid concentration increases as expected, it was also observed that its decomposition rate was also increased (see FIG. 5). It was also observed that the maximum concentration of peracetic acid from each powder concentration was reached at the 20 minute mark.

Example 11

[0113] 4 disinfectant solutions in AOAC Hard Water were prepared using differing concentrations of the powder blend from Example 10, and stirred for 20 minutes. Aliquots were taken and titrated for hydrogen peroxide and peracetic acid concentration, whilst further aliquots were inoculated with suspensions of both vegetative and spore forms of Clostridium sporogenes (ATCC 3584), in the presence of 5% horse serum. The organisms were exposed for 3, 5 and 10 minutes. Each sample was tested in triplicate, and each sample gave greater than a 6 log reduction in viable organisms at each time point.

[0114] Table 4 shows the concentration of the solutions used, the concentrations of both hydrogen peroxide and peracetic acid, along with the log reductions recorded.

TABLE-US-00004 TABLE 4 Concentrations (ppm) Contact Time H2O2 PAA 3 minute 5 minute 10 minute Vegetative cells Sample 1 1382 2964 >6 log >6 log >6 log (20 g/L) Sample 2 1330 2550 >6 log >6 log >6 log (16 g/L) Sample 3 980 1980 >6 log >6 log >6 log (12 g/L) Sample 4 569 1349 >6 log >6 log >6 log (8 g/L) Bacterial spores Sample 1 1382 2964 >6 log >6 log >6 log (20 g/L) Sample 2 1330 2550 >6 log >6 log >6 log (16 g/L) Sample 3 980 1980 >6 log >6 log >6 log (12 g/L) Sample 4 569 1349 >6 log >6 log >6 log (8 g/L)

Example 12

[0115] 7.50 g of the powder blend from Example 10 was taken, and added to 500 ml of tap water, and stirred at room temperature. The time the red colour was discharged was noted, and a 5 ml aliquot taken and titrated. A further 5 ml aliquot was removed and titrated after 20 minutes.

[0116] As can be seen in Table 5, the colour due to Amaranth was being removed between 7 and 8 minutes, with the peracetic acid content at this time being between 0.14 and 0.16%.

TABLE-US-00005 TABLE 5 Dye bleach Time for Amaranth dye time 20 min Sample bleaching HP PAA HP PAA 1 8 min 0.13% 0.14% 0.11% 0.21% 2 7 min 50 sec 0.141 0.155 0.124 0.22% 3 7 min 0.13% 0.16% 0.11% 0.23%

[0117] As can be seen in Table 4, solutions containing at least 1.35% (1349 ppm) peracetic acid exhibit sporicidal activity, thus it may be safely assumed that once the red colouration due to Amaranth has been discharged, the peracetic acid content will be above this sporicidally active concentration.

Example 13

[0118] Differing weights of the powder blend from Example 10 were taken, and added to 500 ml of tap water, and stirred at room temperature. The time the red colour was discharged for each solution is shown in Table 6 and in FIG. 7.

TABLE-US-00006 TABLE 6 Weight Weight of AOAC Time taken for of powder Hard water discharge of red colour (g) (g) (minutes) 6.00 500 7.5 7.02 500.02 7 8.02 500.01 6.5 9.00 500 6 10.03 499.99 5.25

Example 14

[0119] A quantity of the powder blend from Example 10 was taken, and packaged into individual sachets prepared from heat sealed PVA water soluble film. The sachets were prepared by heat sealing two sheets of 50 micron thick PVA film (width 4.65 cm, length 8 cm), together to form an envelope, dispensing approximately 8.2 g powder into each envelope and then sealing the open side to give the finished filled sachet.

[0120] A single sachet was then taken and added to a stirred quantity of tap water (500 ml). The sachet was observe to wrinkle in the water, and then to burst open, releasing the contained powder into the water to give a deep red solution. After approximately 8 minutes, the red colour was discharged, leaving a pale blue solution with a faint odour of peracetic acid. Aliquots of the resultant solution were taken at 10 and 20 minutes and titrated for hydrogen peroxide and peracetic acid content.

[0121] Assessment of an initial production run to produce sachets is shown in Table 7, and Table 8 shows the result of assessing peracetic acid generation from several sample sachets dissolved into 500 ml tap water.

TABLE-US-00007 TABLE 7 mean sachet weight 8.29 Standard deviation 0.514 % RSD 6.2 Maximum weight 9.59 Minimum weight 7.48 sample size 70

TABLE-US-00008 TABLE 8 sachet 10 minutes 20 minutes wt (g) pH H2O2 % PAA % pH H2O2 % PAA % 1 8.3 8.39 0.146 0.145 8.26 0.121 0.223 2 8.48 8.12 0.138 0.171 8.07 0.127 0.215 3 8.74 8.54 0.163 0.175 8.23 0.127 0.229 4 7.78 8.23 0.125 0.175 8.16 0.107 0.208 5 8.16 8.2 0.14 0.109 8.1 0.124 0.2 6 9.1 8.33 0.161 0.214 8.23 0.148 0.198 7 7.67 8.21 0.133 0.192 8.12 0.116 0.16 8 8.11 8.12 0.132 0.078 7.99 0.118 0.205 mean 8.29 8.27 0.14 0.16 8.15 0.12 0.20

Example 15

[0122] A quantity of the powder blend according to Example 10 was taken, and packaged into individual sachets prepared from heat sealed PET-paper-Aluminium-PP laminate. The sachets were prepared by heat sealing a sheet of laminate 6 cm wide to form a cylindrical tube, and then sealing across the tube to form a stick, which was then dosed with the powder blend via an auger doser. The open end of the filled tube was then sealed to give a stick pack.

[0123] The mean gross weight of each stick pack was found to be 8.88 g, with a standard deviation of 0.27 (see table 9). The packaging material was found to weigh 0.88 g, thus giving a mean net weight for the powder of 8.00 g.

TABLE-US-00009 TABLE 9 mean sachet weight 8.88 Standard deviation 0.27 % RSD 3.06 Maximum weight 9.66 Minimum weight 8.13 sample size 500

[0124] To demonstrate homogeneity of blending, sample sachets were taken from various parts of a production run and added to 500 ml of tap water. The hydrogen peroxide and the peracetic acid content at 10, 20 and 30 minutes for each solution were then determined.

[0125] As can be seen in FIG. 8, the hydrogen peroxide and peracetic acid content at 10 minutes was highly variable, and was found to be dependent on stirring speed etc. In some cases, the solutions were observed to still be red at the 10 minute mark (indicated by the letter R in FIG. 8), and these solutions were all associated with a low peracetic acid content. It should be noted that by 20 minutes, the variation in concentrations of hydrogen peroxide and peracetic acid were significantly reduced.

[0126] This example demonstrates the utility of the dye system as an indicator for the presence of an effective biocidal concentration of peracetic acid.

[0127] This was further illustrated by adding 7.50g of the powder blend according to Table 10 to 500 ml of AOAC Hard water and testing its biocidal activity against surface bound micro-organisms in an AOAC Hard Surface Carrier Test 991.47, 48 and 49, conducted in the presence of 5% horse serum against Pseudomonas aeruginosa, Staphylococcus aureus and Salmonella choleraesuis. The test methodology was modified to use a 5 minute contact time rather than the prescribed 10 minute contact time.

TABLE-US-00010 TABLE 10 No. carriers No. Carriers No. Carriers Test organism tested Negative Positive Result Pseudomonas aeruginosa 60 57 3 PASS ATCC 15442 Staphylococcus aureus 60 58 2 PASS ATCC 6538 Salmonella choleraesuis 60 60 0 PASS ATCC 10708

[0128] The powder formulation can also be modified for the production of tablets capable of generating peracetic acid on dissolution into water. Preferably, a means to facilitate the disintegration of the tablet is incorporated into the tablet formulation. This also assists the slower dissolution of the tablet due to the compression required to generate the tablet.

[0129] Poly-NVP based disintegrants such as Disintex 200 (ISP Technologies Inc) were found to be impractical for use, as the cross-linked polymer adsorbed the dyes strongly, and thus gave highly coloured particulate material in the final solution. A preferred means of disintegrating the tablet is to include additional sodium carbonate into the formulation, along with additional acidifying agent. In a more preferred embodiment, sulfamic acid is used as the acidifying agent as this lacks a pKa above 2. If citric acid is used as an acidifying agent in the tablet formulation, then gas formation, hence tablet disintegration, is slowed down once the solution reached a pH of around 6 due to the third pKa of citric acid.

Example 16

[0130] A powder blend according to Table 11 was produced by mixing the ingredients together to produce a homogenous mix. In order to achieve adequate tablet formulation, the mixture was not sieved, and care was taken not to reduce the particle size of the soda ash, sodium percarbonate and the sulfamic acid.

TABLE-US-00011 TABLE 11 TAED 13.54 sodium 37.15 percarbonate sulfamic acid 30.82 Dense soda ash 18.06 Sodium dodecyl 0.23 sulfate Tetrasodium EDTA 0.15 Amaranth 0.038 Cl Acid Blue 182 0.011

[0131] Once blended, the material was tableted using a single punch tablet press, fitted with a 20 mm die set to give tablets with a mean weight of 3.72 g. The mean thickness of the tablets was 9.1 mm, with a thickness to weight ratio of 0.41.

[0132] Two tablets, with a combined weight of 8.34 g were then dissolved in 200 ml of tap water. After stirring for 25 minutes at room temperature, three 10 ml aliquots were removed and titrated. The mean concentrations for hydrogen peroxide and peracetic acid were found to be 0.293% and 0.258% respectively.

[0133] An additional tablet was taken and dissolved into AOAC Hard water, and then tested for antimicrobial activity against Clostridium difficile in the presence of 5% horse serum at 20° C., using the method of BS EN 1276 (1997). The resultant observed log reductions are shown in Table 12.

TABLE-US-00012 TABLE 12 Test organism: Contact time Clostridium difficile (temperature = 20° C. ATCC70992 1 5 10 Log reduction 2.77 >5.86 >5.86 (initial inoculum level 4.8 × 10.sup.6

Example 17

[0134] A solution of hydrogen peroxide was prepared by placing 20 ml of 50% hydrogen peroxide solution into a 1 litre volumetric flask, and then adding DI water to the mark. 1.00 g of Dequest 2010 was added as a stabiliser.

[0135] The diluted hydrogen peroxide solution was titrated against 0.1 M potassium permanganate solution, and the concentration determined to be 0.951% w/v.

[0136] Meanwhile, a powder blend according to Table 13 was prepared

TABLE-US-00013 TABLE 13 Ingredient % w/w TAED B675 31.21 Dye-TAED premix (see .57 example 7) Sodium dodecyl sulphate .76 Aerosil 200 .34 Tetrasodium EDTA .29 Citric acid 16.02 Sodium tripolyphosphate 8.87 Monosodium phosphate 1.03 Soda ash 40.91
500 ml of the diluted hydrogen peroxide solution was then placed in a beaker, and 10.0 g of the powder blend from Table 13 added. The mixture was stirred at room temperature. After approximately 2.5 minutes, the pink colour was discharged, and an aliquot of the solution was taken and titrated. Concentrations of 0.741 and 0.193% were found for hydrogen peroxide and peracetic acid respectively. This embodiment is an example of the kit-form of the composition of the invention—the hydrogen peroxide is stored separately to the powder blend containing the TAED and dye, and the two parts are mixed together at use.

Example 18

[0137] The presence of sodium peroxycarbonate within the formulation has the potential to render the powder blend classifiable as a self-reactive solid (ie a Class 4.1 Dangerous Good, as defined by the United Nations “Recommendations on the Transport of Dangerous Goods, Model Regulations”). In order to assess whether this is a case, the screening procedure as described in the United Nations document “Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria” 5.sup.th Edition was performed on the powder blend from Example 10.

[0138] Two unused firebricks (intended for use in wood combustion stoves) were sourced. As the bricks were narrower than 250 mm, two bricks were abutted together to provide a flame and heat resistant surface of suitable dimensions. A rectangle, 250 mm×20 mm was drawn onto one surface with a marker pen. A contiguous train of the powder blend from Example 10 was then placed onto the firebrick, using the marked lines as a guide. Sufficient powder was used so as to produce a powder train about 250 mm long by 20 mm wide by 10 mm high (approximately 20 g powder).

[0139] The fire brick and powder were placed in a fume hood, and a flame from a hand-held propane burner played onto one end of the powder train. Some local burning, leading to carbonisation and local melting was observed, so the flame was held on the end of the powder train for 2 minutes. No propagation was observed.

[0140] From this test it can be concluded that the formulation of Example 10 is not classifiable as a self-reactive solid, and is not classifiable as a Dangerous Good.