Patent Publication Number: US-2018044615-A1

Title: Stabilized hydrogen peroxide compositions and method of making same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 14/729,802, filed on Jun. 3, 2015, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention is generally directed to stabilization of hydrogen peroxide containing compositions. In particular, the present invention is directed to stabilized hydrogen peroxide compositions and methods of making same. 
     BACKGROUND 
     Hydrogen peroxide solutions have been used for many years for a variety of purposes, including bleaching, disinfecting, and cleaning a variety of surfaces ranging from skin, hair, and mucous membranes to contact lenses to household and industrial surfaces and instruments. Unfortunately, unless stringent conditions are met, hydrogen peroxide solutions begin to decompose into O 2  gas and water within an extremely short time. Typical hydrogen peroxide solutions in use for these purposes are in the range of from about 0.5 to about 10% by weight of hydrogen peroxide in water. The rate at which such dilute hydrogen peroxide solutions decompose will, of course, be dependent upon such factors as pH and the presence of trace amounts of various metal impurities, such as copper or chromium, which may act to catalytically decompose the same. Moreover, at moderately elevated temperatures the rate of decomposition of such dilute aqueous hydrogen peroxide solutions is greatly accelerated. Hence, hydrogen peroxide solutions, which have been stabilized against peroxide breakdown, are in very great demand. 
     Stabilizers, which are usually sequestering agents, are normally added to hydrogen peroxide solutions to combat decomposition due to trace impurities, mainly dissolved metals. Many types of compounds have been used to fill this function, such as diols, quinones, stannate salts, pyrophosphates, various aromatic compounds and amino carboxylic acid salts. However, many of the previously suggested compounds have various issues and challenges associated with them, such as toxicity, environmental impact and poor performance. 
     Examples of specific compounds that have been suggested for use in solutions to protect against hydrogen peroxide decomposition include sodium phenolsulfate; sodium stannate; N,N-lower alkyl aniline, sulfamic acid, sulfolane, and di-straight chain lower alkyl sulfones and sulfoxides; phosphonic acids and their salts; acrylic acid polymers; polyphosphates; polyamino polyphosphonic acids and/or their salts; and specific combinations (or blends) of such compounds. However, in addition to toxicity and environmental impact concerns, many of these suggested compounds or blends have other drawbacks. For example, use of the specific stabilizer(s) either requires specific conditions to provide adequate hydrogen peroxide stability, such as specific pH levels, e.g., acidic conditions, or relatively low hydrogen peroxide concentrations, or has poor stability performance. The poor stability performance can either be poor stability performance generally or poor stability performance in specific formulations that contain other destabilizing components, e.g., surfactants. 
     Despite considerable efforts which have been applied with available stabilizer compounds to solve the problem, there still exists a need to provide hydrogen peroxide solutions which are highly stable without one or more of the aforementioned drawbacks and disadvantages. 
     SUMMARY 
     In accordance with an embodiment of the present invention, a stabilized hydrogen peroxide composition is provided that includes hydrogen peroxide; a disulfonate surfactant; a diester solvent; a sulfonic acid in a sufficient quantity to provide the stabilized hydrogen peroxide with an acidic pH value; and water. 
     In accordance with another embodiment of the present invention, a method of stabilizing a hydrogen peroxide containing composition in provided. The method includes combining an aqueous hydrogen peroxide solution with a stabilizing system comprising a disulfonate surfactant, a diester solvent, and a sulfonic acid in a sufficient quantity to provide the stabilized hydrogen peroxide with an acidic pH value. 
    
    
     DETAILED DESCRIPTION 
     In accordance with embodiments of the present invention, an aqueous solution of hydrogen peroxide is provided that demonstrates stability across a wide temperature range by the inclusion of a stabilizer system comprising a disulfonate surfactant, a diester solvent, and a sulfonic acid in a sufficient quantity to provide an acidic pH to the composition. The stabilized hydrogen peroxide compositions may further comprise additional ingredients, such as those described herein. In accordance with another embodiment, a method of stabilizing aqueous hydrogen peroxide compositions is further provided. 
     Hydrogen Peroxide (H 2 O 2 ): In accordance with embodiments of the present invention, the stabilized hydrogen peroxide-containing compositions may comprise about 0.5 wt % hydrogen peroxide or more, wherein wt % is based on the total weight of the stabilized hydrogen peroxide composition. For example, the stabilized hydrogen peroxide compositions may comprise about 0.5 wt % to about 10 wt %, typically about 1 wt % to about 8 wt %, or about 2 wt % to about 7 wt %, or about 3 wt % to about 5 wt %, or about 4 to about 9 wt %, of hydrogen peroxide. The source of hydrogen peroxide is not particularly limited, and is conveniently commercially available. Typical industrial or food grade hydrogen peroxide solutions are provided as aqueous solutions having about 35 wt % to about 70 wt % hydrogen peroxide, and therefore may be diluted with water and/or other diluents (e.g., an alcohol) to achieve the desired final hydrogen peroxide concentration. The desired stability is imparted to the hydrogen peroxide composition by the stabilizer system that includes a disulfonate surfactant, a diester solvent, and a sulfonic acid, as further described below. 
     Disulfonate Surfactant: In accordance with embodiments of the present invention, the disulfonate surfactant is present in the stabilized hydrogen peroxide composition in an amount sufficient to provide the desired level of stability. For example, the disulfonate surfactant may be present in an amount in a range from about 0.1 wt % to about 10 wt %, wherein wt % is based on the total weight of the stabilized hydrogen peroxide composition. For example, the disulfonate surfactant may be present in the stabilized hydrogen peroxide composition in an amount of about 0.1 wt %, about 0.5 wt %, about 1 wt %, about 1.5 wt %, about 2 wt %, about 3 wt %, about 4 wt %, about 5 wt %, about 7 wt % or about 10 wt %, or in a range between any combination of these values. The disulfonate surfactant may include an alkyldiphenyloxide disulfonate compound or salt thereof. Exemplary salts include alkali metal or alkaline earth metal salts. The alkyldiphenyloxide disulfonate compounds are atypical surfactants and preferably include one or two alkyl chain groups of C6 to C20, linear and/or branched. Accordingly, exemplary alkyldiphenyloxide disulfonate compounds include, but are not limited to, C6 to C20 mono- and/or di-alkyldiphenyloxide disulfonate compounds. For example, the alkyl chains may be hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, propadecyl, butadecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, or didecyl. For example, Dowfax™ 8390, which is available from Dow Chemical Company, is a diphenyloxide disulfonate solution including disodium hexadecyl diphenyloxide disulfonate and dihexadecyl diphenyloxide disulfonate. Another exemplary alkyldiphenyloxide disulfonate compound solution is Dowfax™ 3B2, which is an n-decyl diphenyloxide disulfonate solution. 
     Diester Solvent: In accordance with embodiments of the present invention, the diester solvent is present in the stabilized hydrogen peroxide composition in an amount sufficient to provide the desired level of stability. For example, the diester solvent may be present in an amount in a range from about 0.1 wt % to about 10 wt %, wherein wt % is based on the total weight of the stabilized hydrogen peroxide composition. For example, the diester solvent may be present in the stabilized hydrogen peroxide composition in an amount of about 0.1 wt %, about 0.5 wt %, about 1 wt %, about 1.5 wt %, about 2 wt %, about 3 wt %, about 4 wt %, about 5 wt %, about 7 wt % or about 10 wt %, or in a range between any combination of these values. Exemplary diester solvents include, but are not limited to dialkyl methylglutarate, dialkyl adipate, dialkyl ethylsuccinate, dialkyl succinate, dialkyl glutarate and any combination thereof. The alkyl groups of the diester solvents may be the same or different and independently selected from methyl, ethyl, propyl, isopropyl, n-butyl, pentyl, isoamyl, hexyl, heptyl or octyl. In one embodiment, the diester solvent is dimethyl 2-methylglutarate, which is commercially available from Solvay Chemicals, Inc. as Rhodiasolv® Infinity. 
     Sulfonic Acid: In accordance with embodiments of the present invention, the stabilized hydrogen peroxide compositions contain a sufficient quantity of the sulfonic acid to provide the stabilized hydrogen peroxide with an acidic pH. Non-limiting examples of sulfonic acids include an aliphatic or aromatic hydrocarbon sulfonic acid, a halohydrocarbon sulfonic acid, or combinations thereof. Exemplary hydrocarbon sulfonic acids include C1 to C6 sulfonic acids, such as methane sulfonic acid, ethane sulfonic acid, propane sulfonic acid, butane sulfonic acid, pentane sulfonic acid, hexane sulfonic acid, or benzene sulfonic acid, or C7 to C10 sulfonic acids, such as toluene sulfonic acid, xylene sulfonic acid, or naphthalene sulfonic acid. In one embodiment, the sulfonic acid is methane sulfonic acid, which is commercially available from BASF as Lutropur® MSA. 
     Halohydrocarbon sulfonic acids are hydrocarbon sulfonic acids in which some or all of the hydrogen atoms on the hydrocarbon portion are replaced with a halogen, especially chlorine, bromine or fluorine. Exemplary halohydrocarbon sulfonic acids include fluoromethane sulfonic acid, difluoromethane sulfonic acid, trifluoromethane sulfonic acid, trichloroethane sulfonic acid, trichloromethane sulfonic acid. perchloroethane sulfonic acid, tribromomethane sulfonic acid, 3,3,3-tribromopropane sulfonic acid, tris(trifluoromethyl) methane sulfonic acid, and the like. 
     The sulfonic acid is present in the stabilized hydrogen peroxide composition in a sufficient quantity to provide an acidic pH (i.e., less than 7) at standard temperature and pressure (i.e., 25° C. and 1 atmosphere). For example, the pH of the stabilized hydrogen peroxide composition may be about 6.5 or less, about 6 or less, about 5.5 or less, about 5 or less, about 4.5 or less, about 4 or less, about 3.5 or less, about 3 or less, about 2.5 or less, about 2 or less, or about 1.5 or less, or in a range between any combination of these values. Accordingly, the pH of the stabilized composition may be in a range from about 6.5 to about 1, from about 3.5 to about 1.5, or from about 2.5 to about 1.5, for example. 
     In the event that it becomes necessary to add base (e.g., an excessive amount of sulfonic acid was introduced and the pH is lower than desired), then a base, such as aqueous sodium hydroxide or aqueous potassium hydroxide, may be added to the composition until the desired pH is attained. The base should be free from metal ions that would catalyze decomposition of hydrogen peroxide, such as ferrous ions, ferric ions, cupric ions, cuprous ions, manganous ions, and similar transition metal ions. The base should also be free from both organic and inorganic materials that would react with the hydrogen peroxide. 
     Water: After all the other ingredients have been accounted for, water comprises the balance of the hydrogen peroxide-containing composition. Because hydrogen peroxide is typically commercially available as a 30 wt % to 70 wt % aqueous solution, it is typically necessary to dilute the hydrogen peroxide with water or other diluent to obtain the desired hydrogen peroxide concentration. In accordance with an embodiment, the water or diluent may be free from metal ions that would catalyze decomposition of hydrogen peroxide, such as ferrous ions, ferric ions, cupric ions, cuprous ions, manganous ions, and similar transition metal ions. In accordance with another embodiment, the water or diluent may also be free from organic material that would be oxidized by hydrogen peroxide. In accordance with another embodiment, the water or diluent may also be free of inorganic materials that would react with hydrogen peroxide, such as chlorine (Cl 2 ), hypochlorous acid (HOCl), and sodium hypochlorite (NaOCl). Distilled or deionized water may be used. 
     Optional Ingredients: Additional ingredients may be included in the stabilized hydrogen peroxide composition, so long as the ingredients do not detrimentally affect the stability afforded by the stabilization system of the disulfonate surfactant, the diester solvent, and the sulfonic acid. Exemplary optional ingredients include an alcohol diluent, such as methanol, ethanol, propanol, butanol, pentanol, hexanol, and/or benzyl alcohol; a glycol ether; and/or an aliphatic phosphate ester. 
     The alcohol may be included in the stabilized hydrogen peroxide composition as a diluent or co-solvent. For example, when present, the alcohol may make up about 0.5 wt % to about 70 wt % of the stabilized hydrogen peroxide composition. In an embodiment, the stabilized hydrogen peroxide composition further includes about 30 wt % to about 60 wt % ethanol, for example, about 47 wt % SDA 23A, which is a denatured ethanol including acetone. In another embodiment, the stabilized hydrogen peroxide composition further includes about 5-20 wt % benzyl alcohol, for example, about 11 wt %. In another embodiment, the stabilized hydrogen peroxide composition further includes both ethanol and benzyl alcohol. 
     The glycol ether may be included in the stabilized hydrogen peroxide composition as a coalescent, a solubilizer, or as a viscosity reducer. The glycol ether, when present, may make up about 0.1 wt % to about 10 wt % of the stabilized hydrogen peroxide composition. For example, the glycol ether may be present in the stabilized hydrogen peroxide composition in an amount of about 0.1 wt %, about 0.5 wt %, about 1 wt %, about 1.5 wt %, about 2 wt %, about 3 wt %, about 4 wt %, about 5 wt %, about 7 wt % or about 10 wt %, or in a range between any combination of these values. The glycol ether may be selected from alkyl glycol ethers, such as diethylene glycol butyl ether (DGBE), ethylene glycol monomethyl ether (CH 3 OCH 2 CH 2 OH), ethylene glycol monoethyl ether (CH 3 CH 2 OCH 2 CH 2 OH), ethylene glycol monopropyl ether (CH 3 CH 2 CH 2 OCH 2 CH 2 OH), ethylene glycol monoisopropyl ether ((CH 3 ) 2 CHOCH 2 CH 2 OH), ethylene glycol monobutyl ether (CH 3 CH 2 CH 2 CH 2 OCH 2 CH 2 OH), ethylene glycol monophenyl ether (C 6 H 5 CH 2 OCH 2 CH 2 OH), ethylene glycol monobenzyl ether (C 6 H 5 OCH 2 CH 2 OH), diethylene glycol monomethyl ether (CH 3 OCH 2 CH 2 OCH 2 CH 2 OH), diethylene glycol monoethyl ether (CH 3 CH 2 OCH 2 CH 2 OCH 2 CH 2 OH), diethylene glycol mono-n-butyl ether (CH 3 CH 2 CH 2 CH 2 OCH 2 CH 2 OCH 2 CH 2 OH), propylene glycol phenyl ether (C 6 H 5 CH 2 OCH 2 CH(CH 3 )OH), and/or any combination thereof. In one embodiment, the glycol ether is propylene glycol phenyl ether, which is commercially available from Dow Chemical Company as Dowanol™ PPh Glycol Ether solvent. 
     The aliphatic phosphate ester may be included in the stabilized hydrogen peroxide composition and may function as a hydrotrope or surfactant. When present, the aliphatic phosphate ester may be present in an amount from about 0.01 wt % to about 3 wt %, wherein wt % is based on the total weight of the stabilized hydrogen peroxide composition. For example, the aliphatic phosphate ester may be present in the stabilized hydrogen peroxide composition in an amount of about 0.01 wt %, about 0.02 wt %, about 0.03 wt %, about 0.04 wt %, about 0.05 wt %, about 0.08 wt %, about 0.1 wt %, about 0.5 wt %, about 1 wt %, about 2 wt %, or about 3 wt %, or in a range between any combination of these values. An exemplary aliphatic phosphate ester includes, but is not limited to, Multitrope™ 1214, which is commercially available from Croda, Inc. 
     In accordance with another embodiment, the stabilized hydrogen peroxide compositions may be free of sodium phenolsulfate; sodium stannate; N,N-lower alkyl aniline, sulfamic acid, sulfolane, mono and/or di-straight chain lower alkyl sulfones and sulfoxides; phosphonic acids and their salts; acrylic acid polymers; polyphosphates; polyamino polyphosphonic acids and/or their salts. In accordance with another embodiment, the stabilized hydrogen peroxide compositions may be free of any peroxycarboxylic acids, such as peroxyacetic acid. 
     In accordance with another embodiment, a method of stabilizing a hydrogen peroxide composition is provided. Stabilizing a hydrogen peroxide composition improves and/or maintains the effectiveness of the hydrogen peroxide composition, and is realized by formulating hydrogen peroxide with a disulfonate surfactant; a diester solvent; a sulfonic acid or a salt thereof in a sufficient quantity to provide the stabilized hydrogen peroxide with an acidic pH value; and water. In an embodiment, about 90% or more of the hydrogen peroxide present in the composition is stable for at least 12 months under normal room temperature (RT) storage conditions. In other embodiments, about 80% or more, or 70% or more, or 60% or more of the hydrogen peroxide present in the composition is stable for at least 12 months under normal room temperature storage conditions. Room temperature storage conditions for the hydrogen peroxide compositions are desirable in order to eliminate costly and inconvenient storage problems. While stability testing may be actually performed over a year, shelf stability may also be correlated to an abnormal or exaggerated storage condition for a predetermined amount of time to ensure a product&#39;s stability under normal storage conditions. One acceptable alternative in the hydrogen peroxide solution industry is to test stability at 54° C. for/over 14 days. 
     The stabilized hydrogen peroxide-containing compositions may be used in a variety of disinfectant, cleaning, personal care, pharmaceutical, textile and industrial applications. They disinfect the surfaces into which they are brought into contact and so can be used as disinfectant solutions or disinfectant lotions. When a surfactant is present, they both clean and disinfect the surfaces into which they are brought into contact. They can be applied by any method that insures good contact between the object to be cleaned and/or disinfected and the composition, such as spraying or wiping, and then removed by, for example, rinsing with water and/or wiping. The stabilized hydrogen peroxide-containing compositions may also be used, for example, as liquid detergents and in oral care applications, such as in tooth bleaching compositions. The stabilized hydrogen peroxide-containing compositions may also be applied on woven or nonwoven substrates for use as hydrogen peroxide wipes. 
     The advantageous properties of this invention can be observed by reference to the following examples, which illustrate but do not limit the invention. 
     EXAMPLES 
       
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Ingredients used in examples. 
               
            
           
           
               
               
               
               
            
               
                 Ingredient 
                 Chemical(s) 
                 Source 
                 Comment 
               
               
                   
               
               
                 Hydrogen Peroxide 
                 Hydrogen peroxide 
                 ACROS 
                 35 wt % aq. 
               
               
                   
                   
                 Organics 
                 solution 
               
               
                 Disulfonate Surfactant 
                 Disodium hexadecyl 
                 Dow Chemical 
                 DOWFAX ™ 8930 
               
               
                   
                 diphenyloxide disulfonate; 
                 Co. 
               
               
                   
                 Dihexadecyl diphenyloxide 
               
               
                   
                 disulfonate 
               
               
                 Diester Solvent 
                 Dimethyl 2-Methylglutarate + 
                 Solvay 
                 Rhodiasolv ® 
               
               
                   
                 proprietary surfactants 
                   
                 Infinity 
               
               
                 Sulfonic Acid 
                 Methane sulfonic acid 
                 BASF 
                 Lutropur ® MSA, 
               
               
                   
                   
                   
                 ca. 70% 
               
               
                 Ethanol 
                 Ethanol; acetone 
                 Lyondell 
                 SDA 23A 
               
               
                   
                   
                 Chemical Co. 
               
               
                 Benzyl Alcohol 
                 Benzyl Alcohol 
                 Alfa Aesar 
                 99% 
               
               
                 Alkyl phosphate ester 
                 Polyoxyethylene alkyl ether 
                 Croda 
                 Multitrope ™ 1214 
               
               
                   
                 phosphate 
               
               
                 Glycol ether 
                 Propylene glycol phenyl ether 
                 Dow Chemical 
                 DOWANOL ™ PPh 
               
               
                   
                   
                 Co. 
               
               
                   
               
            
           
         
       
     
     For Examples 1-4 shown in Table 2 (below), the order of addition of the ingredients to the mixing vessel are shown in parenthesis using upper case letters, where A is the first ingredient added to the mixing vessel. 
     Example 1 
     In one example, a stabilized hydrogen peroxide solution was prepared by sequentially adding Dowfax™ 8390, Rhodiasolv® Infinity, Multitrope™ 1214, 35% hydrogen peroxide, and Lutropur® MSA to a quantity of DI water while stirring. Hydrogen peroxide content was 8.23 wt % and solution pH was 1.76. 
     Example 2 
     In another example, a stabilized hydrogen peroxide solution was prepared by sequentially adding Dowfax™ 8390, Rhodiasolv® Infinity, 35% hydrogen peroxide, and Lutropur® MSA to a quantity of DI water while stirring. Hydrogen peroxide content was 8.18 wt % and solution pH was 1.77. 
     Example 3 
     In another example, a stabilized hydrogen peroxide solution was prepared by sequentially adding Dowfax™ 8390, Rhodiasolv® Infinity, 35% hydrogen peroxide, and Lutropur® MSA to a quantity of DI water while stirring. Hydrogen peroxide content was 1.63 wt % and pH was 1.72. 
     Example 4 
     In another example, a stabilized hydrogen peroxide solution was prepared by sequentially adding benzyl alcohol, Dowanol™ PPh, Rhodiasolv® Infinity, DI water, Lutropur® MSA, 35% hydrogen peroxide, and Dowfax™ 8390 to a quantity of SDA 23A ethanol. Hydrogen peroxide content was 1.63 wt % and solution pH was 2.50. 
     Control: A comparative sample was prepared by mixing DI water, citric acid, and hydrogen peroxide together. Hydrogen peroxide content was 1.7 wt % and pH of the solution was 1.87. 
     
       
         
           
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Exemplary stabilized hydrogen peroxide compositions and comparative example. 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Ex-1 
                 Ex-2 
                 Ex-3 
                 Ex-4 
                 Control 
               
               
                 Ingredient 
                 Wt % 
                 Wt % 
                 Wt % 
                 Wt % 
                 Wt % 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 DI water 
                 74.00 
                 (A) 
                 74.00 
                 (A) 
                 93.00 
                 (A) 
                 27.00 
                 (E) 
                 95.32 
               
               
                 Citric Acid 
                   
                   
                   
                   
                   
                   
                   
                   
                 3.48 
               
               
                 SDA23A 
                   
                   
                   
                   
                   
                   
                 47.00 
                 (A) 
               
               
                 Rhodiasolv ® 
                 1.00 
                 (C) 
                 1.00 
                 (C) 
                 1.00 
                 (C) 
                 1.50 
                 (D) 
               
               
                 Infinity 
               
               
                 Dowfax ™ 8390 
                 1.10 
                 (B) 
                 1.10 
                 (B) 
                 1.10 
                 (B) 
                 0.60 
                 (H) 
               
               
                 Multitrope ™ 1214 
                 0.05 
                 (D) 
               
               
                 Benzyl Alcohol 
                   
                   
                   
                   
                   
                   
                 11.00 
                 (B) 
               
               
                 DOWANOL ™ PPh 
                   
                   
                   
                   
                   
                   
                 5.50 
                 (C) 
               
               
                 Hydrogen Peroxide, 
                 23.63 
                 (E) 
                 23.63 
                 (D) 
                 4.53 
                 (D) 
                 4.50 
                 (G) 
                 4.69 
               
               
                 35% 
               
               
                 Lutropur ® MSA 
                 0.17 
                 (F) 
                 0.16 
                 (E) 
                 0.20 
                 (E) 
                 0.10 
                 (F) 
               
               
                 70% 
               
            
           
           
               
               
               
               
               
               
            
               
                 pH 
                 1.76 
                 1.77 
                 1.72 
                 2.50 
                 1.87 
               
               
                 HP content (%) 
                 8.23 
                 8.18 
                 1.63 
                 1.63 
                 1.7 
               
               
                   
               
            
           
           
               
            
               
                 Stability: H 2 O 2  % (pH) 
               
            
           
           
               
               
               
               
               
               
            
               
                 (Batch I) 
                 10 days 
                 10 days 
                 9 days 
                 14 days 
                   
               
               
                   
               
               
                 At RT 
                 8.33 
                 8.30 
                 1.47 
                 1.53 
               
               
                 At 4° C. 
                 7.94 
                 8.10 
                 1.91 
                 n/a 
               
               
                 At 60° C. (*55° C.) 
                 8.02 
                 7.81 
                 1.56 
                  1.45* 
               
               
                   
               
               
                 (Batch II) 
                 17 days 
                 17 days 
                 17 days 
                 17 days 
                 17 days 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 At RT 
                 8.34 
                 (1.60) 
                 8.33 
                 (1.79) 
                 1.68 
                 (1.85) 
                 1.68 
                 (2.26) 
                 1.67 (1.86) 
               
               
                 At 40° C. 
                 8.29 
                 (1.66) 
                 8.14 
                 (1.84) 
                 1.65 
                 (1.86) 
                 1.67 
                 (2.23) 
                 n/a 
               
               
                 At 55° C. 
                 8.28 
                 (1.67) 
                 8.16 
                 (1.83) 
                 1.63 
                 (1.87) 
                 1.57 
                 (2.31) 
                 0.98 (1.93) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 15 months, 
                 15 months, 
                 2 months, 
                 11 months, 
                   
               
               
                 (Batch I) 
                 23 days 
                 23 days 
                 6 days 
                 2 days 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 At RT 
                 7.42 
                 (1.74) 
                 7.76 
                 (1.79) 
                 1.64 
                 1.34 
                 (2.44) 
               
               
                   
               
            
           
         
       
     
     Stability testing: Values of hydrogen peroxide percentages (concentrations) disclosed herein were measured using the following method. The hydrogen peroxide-containing solutions were stored for the stated period of time (e.g., 17 days) and conditions. After the stated storage time period, the hydrogen peroxide concentration was measured using the redox titration method. The redox titration method is a standard method known in the art for measuring peroxide concentration. Specifically, the redox titration method was performed by weighing a 0.3 g sample to be tested into a 100 mL beaker using an analytical balance accurate to 0.001 g, and recording the weight. Then, 15 ml of refrigerated 10% H 2 SO 4  was added, 5 drops of a Ferroin Indicator was added, and the initial volume of titrant was recorded. A 0.1 N Ceric Sulfate volumetric solution was then titrated, adding the titrant drop-wise until the Salmon color changed to yellow. (The yellow endpoint should be similar in color to the finished product solution.) No greater than 3 ml DI water was added as necessary to rinse the sides of the beaker where solution may have splashed. The final volume of titrant added for the solution was recorded, and then the hydrogen peroxide concentration was calculated as follows: 
       % H 2 O 2   =a×N× 1.7/ m    
     where: a=the net volume of ceric sulfate titrant consumed; N=the exact normality of ceric sulfate used; and m=the mass of the sample weighed. Hydrogen peroxide content was measured for samples stored at various temperatures over extended periods of time, as shown in Table 2. 
     When the storage period is long, the concentration of the hydrogen peroxide can alternatively be determined by measuring the concentration as described above after at least one hundred and twenty days and then extrapolating for the remainder of the period using first order kinetics, as is known in the art. The above-described method is performed just after manufacture of a peroxide product and at the end of the specified storage period in order to determine the absolute hydrogen peroxide concentrations as well as the percentage of the original concentration remaining, as is known in the art. 
     As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural reference unless the context clearly dictates otherwise. As well, the terms “a” (or “an”), “one or more” and “at least one” can be used interchangeably herein. It is also to be noted that the terms “comprising”, “including”, “characterized by” and “having” can be used interchangeably. 
     While the present invention has been illustrated by the description of one or more embodiments thereof, and while the embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope of the general inventive concept.