CA2028930A1 - Stable hypochlorous acid sterilizing solution and kit - Google Patents
Stable hypochlorous acid sterilizing solution and kitInfo
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- CA2028930A1 CA2028930A1 CA 2028930 CA2028930A CA2028930A1 CA 2028930 A1 CA2028930 A1 CA 2028930A1 CA 2028930 CA2028930 CA 2028930 CA 2028930 A CA2028930 A CA 2028930A CA 2028930 A1 CA2028930 A1 CA 2028930A1
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- component
- chemical sterilant
- recited
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- hypochlorite
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- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
- A01N59/00—Biocides, pest repellants or attractants, or plant growth regulators containing elements or inorganic compounds
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- Chemical & Material Sciences (AREA)
- Agronomy & Crop Science (AREA)
- Inorganic Chemistry (AREA)
- Pest Control & Pesticides (AREA)
- Plant Pathology (AREA)
- Health & Medical Sciences (AREA)
- Engineering & Computer Science (AREA)
- Dentistry (AREA)
- General Health & Medical Sciences (AREA)
- Wood Science & Technology (AREA)
- Zoology (AREA)
- Environmental Sciences (AREA)
- Apparatus For Disinfection Or Sterilisation (AREA)
- Agricultural Chemicals And Associated Chemicals (AREA)
Abstract
ABSTRACT
A stable hypochlorous acid sterilant solution and method for providing the sterilant solution by combining a first solution containing a salt of hypochlorite with a second component selected from the group of phosphoric acid, salts of dihydrogen phosphate, acetic acid, and formic acid is disclosed.
A stable hypochlorous acid sterilant solution and method for providing the sterilant solution by combining a first solution containing a salt of hypochlorite with a second component selected from the group of phosphoric acid, salts of dihydrogen phosphate, acetic acid, and formic acid is disclosed.
Description
2~8~3~
TITLE OF T~E INVENTION
.
STABLE HYPOCHLOR~US ACID STERILIZING SOLUTION A~D XIT
... ~ . , . .. _ . . . . ...... , .. .. .. .... . . .. . . . _ _ _ _ ..
-------- ---- ------------------FI~LD1DF-~EE 1NVENTION----- --.
This invention relates to a relatively stable, substantially non-corrosive hypochlorous acid solution for the rapid sterilization of medical and non-medical devices and other surfaces, and to a method for producing and using the solution.
BACKGRO~ND OF THE INVENTION
The killing of various microorganisms through the use of sterilizing and disinfecting processes, such as the application of chemicals, heat, or radiation, is well known.
1~ Chemicals which are capable of killing vegetative bacteria are commonly known as "disinfectants," while those which are able to kill every type of microorganism, including highly resistant dormant or spore forms of bacteria, are referred to as "sterilizing agents" or "sterilants."
Glutaraldehyde and formaldehyde solutions have been used for disinfection and sterilization purposes. However, glutaraldehyde and formaldehyde require several hours in order to kill standard spores at room temperature. Further, both glutaraldehyde and formaldehyde are particularly pungent and are suspected carcinogens, thus limiting their usefulness in hospital and clinical settings.
Phenolics have also been used for disinfecting purposes. Phenols and phenolics have been found to be incapable of killing hydrophilic viruses such as poliovirus and bacterial spores. Disposal of phenolics poses a particular problem and has resulted in the banning of phenolics in certain arid portions of the country. The toxicity of phenolics, as well as their associated odor, poses a major obstacle to their effective use as disinfectants.
Other sterilizing techniques, including the use of radiation and the application of ethylene oxide, are limited to use within containment chambers. This limitation makes it impossible to use these techniques for the sterilization of open environmental surfaces. Such techniques are also particularly slow and have potentially toxic consequences.
Super-heated steam under pressure has also been used in sterilization techniques. However, many devices in use today are made of heat-sensitive materials, making the use of super-heated steam impractical. Further, such super-heated steam cannot be used for the effective sterilization of open environmental surfaces.
The disinfecting and sterilizing effects of chlorine and chlorine compounds are well-known and are discussed in detail. For example, solutions of inorganic salts of hypochlorite (OCl) such as sodium (Na+), calcium (Ca++) or lithium (Li+ ) are known to have some ~. .
s~; -2-~V28$3~
antimicrobial activity. It has been shown that hypochlorous acid (HOCl) in these solutions provides significantly more disinfection than the hypochlorite ion. However, hypochlorous ~~~ ~-~ -~-acicl -is-- -a -strong -oxidi~zing---~~agen~~ an~d-----m-ay ~ her-efore~
corrosive to certain materials.
One method for avoiding the corrosive effects of hypochlorous acid is disclosed by Echols, et al. in U.S.
Patent No. 3,717,580, "Method of Disinfecting and Self-Limiting Solution Therefor." Echols, et al. disclosed the mixing of an inorganic hypochlorite salt and an aqueous solution of an inorganic salt of hydroxycarboxylic acid (either citric acid or malic acid) wherein the molar ratio of the hypochlorite salt to the hydroxycarboxylic acid salt is at most 2:1.
As a result of this specific molar ratio, the half-life of the resulting hypochlorous acid solution is relatively short, i.e., less than 10 m-nutes. In this way, Echols, et al. was able to avoid the known corrosive effect of the hypochlorous acid.
The disinfecting solution produced in accordance with the disclosure of Echols, et al., proved to provide desirable characteristics for disinfecting naval ships subjected to microorganisms during the course of germ warfare. However, the strong oxidizing nature of the resulting hypochlorous acid solution caused it to react further with other chemicals, particularly citric acid in the aqueous solution, to form , .. , , - , . . . .... . . . .. .. - -.
2~28~3~
- byproducts ~uch as chloroform, chlorine ions, and carbon ; dioxide. Chloroform is known to be potentially toxic, depending on concentration and duration of exposure.
: ::- = ~urther, the-- ~~relative~ hort-= half~ f~~ =~he = --.. . . .. ...
hypochlorous acid solution disclosed by Echols, et al., prevented the solution for being used for sterilizing purposes over an extended period. The Echols, et al., hypochlorous acid solution was effective for only a single application, making its use economically impractical.
There exists a need for an effective yet environmentally safe solution and method for the sterilization of medical and non-medical instruments and surfaces.
One of the principal objects of the present invention is to overcome deficiencies of prior sterilization methods.
Another object of the invention is to provide an effective and safe sterilization method for disinfecting surfaces, objects and the like, as well as medical instruments.
It is an object of this invention to provide a relatively stable hypochlorous acid sterilant solution and a method for producing and using the sterilant solution.
The sterilant solution includes the combination of a solution which contains a salt of hypochlorite and a solution or solid which is an acidic buffer. Solutions or solids con-taining phosphoric acid, salts of phosphoric acid, acetic acid, and formic acid are the preferred acid buffers. The preferred pH range for the sterilant solution is pH 5.5-7.5. The .... .. ..... , ,.. .. : ~
2~28~3`~
_ steri~ant solution i~ relatively stable and therefore capable of providing a sterilization effect for periods exceeding 24 hours. Further, the sterilant solution does not produce poténtially harmful~~y-pr'oduct~'such''as chloroform.--~~~~--------~
S
S~MMARY OF THæ INVE~TION
The method for producing and using a relatively stable hypochlorous acid solution of the present invention includes the combining of a solution of a salt of hypochlorite with an acidic buffer, thereby forming a buffered hypochlorous acid solution. Solutions or solids containing phosphoric acid',' salts ~ ~f~' phosphoric acid, acetic acid, and formic acid preferably are used as the acidic buffer. The resulting hypochlorous acid solution is relatively stable and therefore capable of providing a sterilization effect for periods exceeding 24 hours. Further, the resulting hypochlorous acid solution does not produce potentially harmful byproducts such as chloroform.
The present invention also provides a kit for the sterilization of medical instruments. The kit contains a solution of a salt of hypochlorite and an acidic buffer as described above. In another respect of the invention, the kit inc'ludes a device for determining the presence of a sterilizing threshold concentration of chlorine in the resulting hypochlorous acid solution, thereby confirming the ability of the solution to provide the desired sterilizing effect.
,, .,,,, .. ~
2~28~3~
In yet another aspect of the invention, the ~it includes a sacrificial metallic tray for use when sterilizing metallic instruments, thereby obviating the potentially c~rrosive -~- ~ëf~ects~~o~-hypo-chloro-us~-~acia-s-teri~l~zation~.
DETAILED DESCRIPTION OF THE INVENTION
The present invention teaches a stable hypochlorous acid solution and its production, which is by combining a hypochlorite solution and an acidic buffer. The hypochlorite solution contains a salt of hypochlorite such as sodium (Na+), calcium ~Ca++), or lithium (Li~ ~ salts of hypochlorite and preferably has a substantially alkaline pH
in order to ensure its stability, e.g., p~ 10-13. It has been shown that hypochlorite salts are particularly stable in a pH range of 11-12.
The acidic buffer contains a moderately weak acid having a buffering capability. The buffçr is preferably from the group comprising phosphoric acid (H3PO4), salts of dehydrogen phosphate, (e.g., NaH2PO4), acetic acid 20 (C2H4O2), and formic acid (CH2O2). Each of these sys~ems produces a characteristic hypochlorous acid solution when combined with the hypochlorite solution. The hypochlorous acid solution produced by the combination of the hypochlorite and buffer is relatively stable, as set forth in greater detail below, and does not produce byproducts such as chloroform and carbon dioxide.
-... ... , .,~ , . , ~ , , .
The concentration of hypochlorous acid at substantially neutral pH levels is significantly less than its concentration at acidic pH levels. For example, at neutral pH, a hypochlorous acid solution will be approximately 75~ HOCl and 25~ OCl-. At pH 6.5, the solution is 85~ HOCl and at pH 6.0, 95~ HOCl. As set forth in detail below, the hypochlorous acid produced by the present method is preferably in the range of pH 5.5-7.2.
Phosphoric acid has been found to provide optimal pH
characteristics in producing the hypochlorous acid sterili-zing solution of the present invention. However, phosphoric acid can be difficult to use in liquid form due to variations in concentration. Acetic acid and formic acid are also appropriate buffers. However, each is odiferous and may prove to be undesirable under certain conditions.
Buffers consisting of a salt of dihydrogen phosphate provide predictable results when used in conjunction with the present invention. Sodium dihydrogen phosphate (NaH2PO4) is the most common and least expensive of the salts of dihydrogen phosphate. For the purposes of this disclosure, sodium dihydrogen phosphate will be used. However, it is to be appreciated that other acidic buffers (e.g., phosphoric acid, acetic acid, and formic acid) may be used in lieu of sodium dihydrogen phosphate.
By mixing the hypochlorite and buffer, the following reaction occurs:
XOCl + HZ HOCl + XZ
For example, where the hypochlorite solution is sodium hypochlorite (NaOCl) and the buffer is sodium dihydrogen phosphate (NaH2PO4) in excess ratios, the following reaction occurs:
NaOCl + NaH2PO4 HOCl + Na2HPO4 The presence of both NaH2PO4 and Na2HPO4 maintains the solution pH in the desired range 5.5-7.2. The reaction set forth above occurs immediately and produces a hypochlorous acid solution which is capable of rapidly killing spores at 20C. The resulting solution is relatively stable and is capable of providing the desired antimicrobial effect for periods of 24 hours or longer, depending upon incidental dilution or neutralization by organic soil such as human tissue.
Very little chlorine is released during the reaction because the pH of the sodium dihydrogen phosphate solution is preferably relatively high, i.e., 4.0-5Ø Furthermore, the reaction does not form chloroform because there is no source of carbon atoms in the reaction mixture. The absence of chloroform, a known toxic material, as a byproduct of the reaction is particularly desirable where the resulting hypochlorous acid solution is to be used in a hospital or clinical setting to sterilize medical devices and surfaces.
Due to the inherent instability and reactivity of hypochlorous acid, it can be expected to break down over time.
It has been shown that the hypochlorous acid solution produced in accordance with the present invention contains chlorine for as long as 5-8 days. Concentrations of buffered OCl-/HOCl as low as 20 ppm and 10 ppm have exhibited long term 2028~3~
stability. Higher initial concentrations of OCl- exhibit slightly greater stability. However, as set forth in the table below, low initial concentrations of OCl- provide the ~es~ire~a~s y ... . . . . . .. . ... ...
The following table showsthe relative stability of the hypochlorous acid (at initial levels of 20-500 ppm OCl- of the present invention:
Percent(%) Remaining Time (Hours) Available Hypochlorite o 100%
0.33 97-99 1.00 94-98 2.00 94-96 3.00 93-95 4.00 gl-94 6.00 90-92 8.00 87-91 12.00 85-88 24.00 78-82 The hypochlorous acid solution of the present invention provides a highly efficacious sterilizing solution for vinyl gloves, tygon tubing, amber latex rubber, the plastic of a blood bag, styrofoam packing material, hard plastic clothespins, glass, and other materials su~ as Lawton stainless steel.
In one example of the present invention, the hypochlorite solution comprises 0.25~ of hypochlorite ions (OCl-) by weight ~ . 9 _ _ _ _ _ 2~28~3~
at pH 11.0 and the buffering solution comprises 0.55 M
. _ _ _ , . . .. , . . . . . .. . . . . _ . _ . . . . ......... _ _ .. _ . _ . _ . , . _ .
~ NaH2PO4 at pH 4.5. The hypochiorous acid solution resulting~
from the mixing of equal volumes of the hypochlorite and buffering solutions is at 1250 ppm HOCl and has a pH of 7.0 + 0.2.
In a second example, the hypochlorite solution comprises 0.32% hypochlorite ions (OC1-) by weight at pH
12.5 and the buffering solution is 2.0M NaH2PO4 at pH 4.5.
When four ounces of each solution is mixed and diluted to 10 one gallon with deionized water, the resulting hypochlorous acid solution is at 100 ppm HOCl and has a pH of 6.0 + 0.2.
In a third example, the hypochlorite solution comprises one gallon of 0.25% hypochlorite ions (OC1-) by weight at pH
ll.S. The acidic buffer component consists of 4 oz. dry, 15 solid NaH2PO4 H2O- When the solid is dissolved in the hypochlorite solution, the mixture consists of 2500 ppm HOC1 and has a pH of 6.0-6.5.
Due to the relative stability of the hypochlorous acid solution of the present invention the amount of salt of 20 hypochlorite necessary to produce the desired hypochlorous - acid solution is relatively low. For Example, solutions having hypochlorite concentrations as low as 10 ppm hav ~28~3~) __ been found to provide effective results when combined with---- -------, , . . . . . ...................... .. . . _ . _ the appropriate buffer used in conjunction with the method~~ ~~~~~ ~~~
of the present invention. Accordingly, the cost of producing the hypochlorous acid solution according to the present invention is reduced in comparison to prior methods which produce unstable hypochlorous acid solutions.
This cost savings is amplified by the stability of the hy~ochlorous acid solution to be reused. Despite the stability of the resulting hypochlorous acid solution, it 10 has been found preferable to avoid prolonged use due to the introduction of biological tissues.
The hypochlorous acid solution of the present invention has also been found to be safe for use on plastic laminated surfaces, lacquered wood surfaces, glass, and laboratory 15 soapstone. There is no noxious odor associated with the use of the resulting hypochlorous acid solution, nor is there any visible salt residue. Thus, the hypochlorous acid can be used as a surface sterilant as well as an immersion sterilant.
In an alternative embodiment, a surfactant or other suitable wetting agent can be included in the system in order to enhance the effectiveness of the hypochlorous acid .. . . . .
~2~3~
__ of_ t'he present invention. The _nclusion of a surfactant or .. . .. .... , . . . ... . _ . .. . .. _ _ _ ... _ _ . .... _ _ . _ .. _ _ . _ _ . _ . _ _ _ wetting agent is of particular value where the hypochlorous~'--'~~'~~~~~
acid is used as a surface sterilant. For example, small amounts of methanol in the buffering solution would provide improved wetting characteristics~
In other alternative embodiments, the system may also contain buffering agents, perfumes, odorants, corrosion inhibitors, and lubricating agents. However, such agents must not interfere with the antimicrobial activity of the resulting hypochlorous acid solution, and preferably do not react with the hypochlorous acid to produce undesirable byproducts.
The hypochlorous acid solution produced in accordance with the present invention is particularly desirable for use in hospital and clinical environments for the reasons set forth above, i.e., long-term stability and low cost.
Medical instruments such as endoscopes must be properly sterilized between uses in order to avoid the transmission of microorganisms from one patient to another.
Accordingly, a hospital or clinical employee desirous of sterilizing a medical device will mix the hypochlorite .
.. ---- -- .. ........ .
~2893~
s,olut,ion,,,,,cont,aining a salt of_~ypochlorite_wi_h the_acidic _ _ _ _ _ _ buffer comprising, for example, sodium~dihydrogen phosphate, -as discussed in detail above. This mixing will immediately produce a sterilizing solution containing hypochlorous acid.
Mixing may be performed in a sterilizing pan or, in the alternative, may be performed in a separate mixing container such that the resulting hypochlorous acid is subsequently placed into the sterilizing pan. The medical devices can then be placed into the sterilizing pan containing the hypochlorous acid solution. Sterilization of surfaces can be effected by spraying the hypochlorous acid solution on the target surface and removing the hypochlorous acid solution at the end of a predetermined period.
The hypochlorous acid solution produced in accordance with the present invention provides a rapid rate of sterilization. The precise rate at which microorganisms will be killed by the hypochlorous acid solution varies in accordance with the concentration of HOCl and the presence of tissue and other foreign matter in the sterilizing solu-tion. However, a period of approximately one (1) minute hasbeen found to provide sterilization of medical instruments.
, _ .. . . _ .......................................... , , ,, . . .. _ _ _ . .. _ _ .
. , ~ . . . - . -~028~3a and surfaces. Sterilization using the hypochlorous acid solution of the present invention has been ~hown to occur in as little as ten (10) seconds.
~ . ... , .. . _._ . =, _ _ . _ _ _, _ _ -- , , _ . , _ . . _ , _ _ - In order to ensure--tha~ the~--hypo~ lorous acla . sDlutlon is sufficiently active to sterilize medical devices, it is desirable to test the solution in order to determine its relative activity. A starch-iodine-thiosulfate test can be used for this purpose. The starch-iodine-thiosulfate test utilizes well-known principles to determine the presence of a threshold amount of hypochlorite in a solution, as set forth in detail in Vogel, Te~tbook of Quantitative Inorqanic Analysis, t4th ed. 1978~ at pp. 382-83. Known methods for testing the solution's ability to kill spores may also be used (e.g., commercial spore strips).
In order to minimize the potential corrosive effects of the resulting hypochlorous acid solution, it may be desirable to provide a sacrific al aluminum tray to be used in conjunction with the sterilizing pan when the hypochlorous acid solution of the present invention is to be used to sterilize metallic devices. In this way, any corrosive effects of the hypochlorous acid are realized with respect to the aluminum tray rather than the medical devices which are placed therein.
A sterilizing kit in accordance with the present invention preferably includes a first solution of an inorganic hypochlorite salt and a second component containing, for ... . ... .. . .
__ _ __ - 14 _ ~_ _ _ _ 21~28~3~
example, a sodium dihydrogen phosphate buffer, as set forth .
in detail above. In addition, the sterilizing kit can include a test kit such ~s a starch-iodine-thiosulfate test to ~, . . ,, . . ~
----- determlne - whether--thre-sh-old~l-evel~ o-f =hyp~c~lc~l~e -are.~
. . , . _ . . .. , . .. . . ^ ^ ^ .. _ . = _, _ . . .. . . _ .. _ = . . . . ~, . _ _, _ . = . .. . . . . .
present. Where the kit is to be used for the sterilization of metailic devices, a sacrificial aluminum tray, as discussed above, can also be provided in the kit.
Although the present invention has been described herein with respect to the specific preferred embodiments, it will be evident that various and further modifications are possible without departing from the spirit and scope of the present invention.
_ ^. 15 - . ; .
TITLE OF T~E INVENTION
.
STABLE HYPOCHLOR~US ACID STERILIZING SOLUTION A~D XIT
... ~ . , . .. _ . . . . ...... , .. .. .. .... . . .. . . . _ _ _ _ ..
-------- ---- ------------------FI~LD1DF-~EE 1NVENTION----- --.
This invention relates to a relatively stable, substantially non-corrosive hypochlorous acid solution for the rapid sterilization of medical and non-medical devices and other surfaces, and to a method for producing and using the solution.
BACKGRO~ND OF THE INVENTION
The killing of various microorganisms through the use of sterilizing and disinfecting processes, such as the application of chemicals, heat, or radiation, is well known.
1~ Chemicals which are capable of killing vegetative bacteria are commonly known as "disinfectants," while those which are able to kill every type of microorganism, including highly resistant dormant or spore forms of bacteria, are referred to as "sterilizing agents" or "sterilants."
Glutaraldehyde and formaldehyde solutions have been used for disinfection and sterilization purposes. However, glutaraldehyde and formaldehyde require several hours in order to kill standard spores at room temperature. Further, both glutaraldehyde and formaldehyde are particularly pungent and are suspected carcinogens, thus limiting their usefulness in hospital and clinical settings.
Phenolics have also been used for disinfecting purposes. Phenols and phenolics have been found to be incapable of killing hydrophilic viruses such as poliovirus and bacterial spores. Disposal of phenolics poses a particular problem and has resulted in the banning of phenolics in certain arid portions of the country. The toxicity of phenolics, as well as their associated odor, poses a major obstacle to their effective use as disinfectants.
Other sterilizing techniques, including the use of radiation and the application of ethylene oxide, are limited to use within containment chambers. This limitation makes it impossible to use these techniques for the sterilization of open environmental surfaces. Such techniques are also particularly slow and have potentially toxic consequences.
Super-heated steam under pressure has also been used in sterilization techniques. However, many devices in use today are made of heat-sensitive materials, making the use of super-heated steam impractical. Further, such super-heated steam cannot be used for the effective sterilization of open environmental surfaces.
The disinfecting and sterilizing effects of chlorine and chlorine compounds are well-known and are discussed in detail. For example, solutions of inorganic salts of hypochlorite (OCl) such as sodium (Na+), calcium (Ca++) or lithium (Li+ ) are known to have some ~. .
s~; -2-~V28$3~
antimicrobial activity. It has been shown that hypochlorous acid (HOCl) in these solutions provides significantly more disinfection than the hypochlorite ion. However, hypochlorous ~~~ ~-~ -~-acicl -is-- -a -strong -oxidi~zing---~~agen~~ an~d-----m-ay ~ her-efore~
corrosive to certain materials.
One method for avoiding the corrosive effects of hypochlorous acid is disclosed by Echols, et al. in U.S.
Patent No. 3,717,580, "Method of Disinfecting and Self-Limiting Solution Therefor." Echols, et al. disclosed the mixing of an inorganic hypochlorite salt and an aqueous solution of an inorganic salt of hydroxycarboxylic acid (either citric acid or malic acid) wherein the molar ratio of the hypochlorite salt to the hydroxycarboxylic acid salt is at most 2:1.
As a result of this specific molar ratio, the half-life of the resulting hypochlorous acid solution is relatively short, i.e., less than 10 m-nutes. In this way, Echols, et al. was able to avoid the known corrosive effect of the hypochlorous acid.
The disinfecting solution produced in accordance with the disclosure of Echols, et al., proved to provide desirable characteristics for disinfecting naval ships subjected to microorganisms during the course of germ warfare. However, the strong oxidizing nature of the resulting hypochlorous acid solution caused it to react further with other chemicals, particularly citric acid in the aqueous solution, to form , .. , , - , . . . .... . . . .. .. - -.
2~28~3~
- byproducts ~uch as chloroform, chlorine ions, and carbon ; dioxide. Chloroform is known to be potentially toxic, depending on concentration and duration of exposure.
: ::- = ~urther, the-- ~~relative~ hort-= half~ f~~ =~he = --.. . . .. ...
hypochlorous acid solution disclosed by Echols, et al., prevented the solution for being used for sterilizing purposes over an extended period. The Echols, et al., hypochlorous acid solution was effective for only a single application, making its use economically impractical.
There exists a need for an effective yet environmentally safe solution and method for the sterilization of medical and non-medical instruments and surfaces.
One of the principal objects of the present invention is to overcome deficiencies of prior sterilization methods.
Another object of the invention is to provide an effective and safe sterilization method for disinfecting surfaces, objects and the like, as well as medical instruments.
It is an object of this invention to provide a relatively stable hypochlorous acid sterilant solution and a method for producing and using the sterilant solution.
The sterilant solution includes the combination of a solution which contains a salt of hypochlorite and a solution or solid which is an acidic buffer. Solutions or solids con-taining phosphoric acid, salts of phosphoric acid, acetic acid, and formic acid are the preferred acid buffers. The preferred pH range for the sterilant solution is pH 5.5-7.5. The .... .. ..... , ,.. .. : ~
2~28~3`~
_ steri~ant solution i~ relatively stable and therefore capable of providing a sterilization effect for periods exceeding 24 hours. Further, the sterilant solution does not produce poténtially harmful~~y-pr'oduct~'such''as chloroform.--~~~~--------~
S
S~MMARY OF THæ INVE~TION
The method for producing and using a relatively stable hypochlorous acid solution of the present invention includes the combining of a solution of a salt of hypochlorite with an acidic buffer, thereby forming a buffered hypochlorous acid solution. Solutions or solids containing phosphoric acid',' salts ~ ~f~' phosphoric acid, acetic acid, and formic acid preferably are used as the acidic buffer. The resulting hypochlorous acid solution is relatively stable and therefore capable of providing a sterilization effect for periods exceeding 24 hours. Further, the resulting hypochlorous acid solution does not produce potentially harmful byproducts such as chloroform.
The present invention also provides a kit for the sterilization of medical instruments. The kit contains a solution of a salt of hypochlorite and an acidic buffer as described above. In another respect of the invention, the kit inc'ludes a device for determining the presence of a sterilizing threshold concentration of chlorine in the resulting hypochlorous acid solution, thereby confirming the ability of the solution to provide the desired sterilizing effect.
,, .,,,, .. ~
2~28~3~
In yet another aspect of the invention, the ~it includes a sacrificial metallic tray for use when sterilizing metallic instruments, thereby obviating the potentially c~rrosive -~- ~ëf~ects~~o~-hypo-chloro-us~-~acia-s-teri~l~zation~.
DETAILED DESCRIPTION OF THE INVENTION
The present invention teaches a stable hypochlorous acid solution and its production, which is by combining a hypochlorite solution and an acidic buffer. The hypochlorite solution contains a salt of hypochlorite such as sodium (Na+), calcium ~Ca++), or lithium (Li~ ~ salts of hypochlorite and preferably has a substantially alkaline pH
in order to ensure its stability, e.g., p~ 10-13. It has been shown that hypochlorite salts are particularly stable in a pH range of 11-12.
The acidic buffer contains a moderately weak acid having a buffering capability. The buffçr is preferably from the group comprising phosphoric acid (H3PO4), salts of dehydrogen phosphate, (e.g., NaH2PO4), acetic acid 20 (C2H4O2), and formic acid (CH2O2). Each of these sys~ems produces a characteristic hypochlorous acid solution when combined with the hypochlorite solution. The hypochlorous acid solution produced by the combination of the hypochlorite and buffer is relatively stable, as set forth in greater detail below, and does not produce byproducts such as chloroform and carbon dioxide.
-... ... , .,~ , . , ~ , , .
The concentration of hypochlorous acid at substantially neutral pH levels is significantly less than its concentration at acidic pH levels. For example, at neutral pH, a hypochlorous acid solution will be approximately 75~ HOCl and 25~ OCl-. At pH 6.5, the solution is 85~ HOCl and at pH 6.0, 95~ HOCl. As set forth in detail below, the hypochlorous acid produced by the present method is preferably in the range of pH 5.5-7.2.
Phosphoric acid has been found to provide optimal pH
characteristics in producing the hypochlorous acid sterili-zing solution of the present invention. However, phosphoric acid can be difficult to use in liquid form due to variations in concentration. Acetic acid and formic acid are also appropriate buffers. However, each is odiferous and may prove to be undesirable under certain conditions.
Buffers consisting of a salt of dihydrogen phosphate provide predictable results when used in conjunction with the present invention. Sodium dihydrogen phosphate (NaH2PO4) is the most common and least expensive of the salts of dihydrogen phosphate. For the purposes of this disclosure, sodium dihydrogen phosphate will be used. However, it is to be appreciated that other acidic buffers (e.g., phosphoric acid, acetic acid, and formic acid) may be used in lieu of sodium dihydrogen phosphate.
By mixing the hypochlorite and buffer, the following reaction occurs:
XOCl + HZ HOCl + XZ
For example, where the hypochlorite solution is sodium hypochlorite (NaOCl) and the buffer is sodium dihydrogen phosphate (NaH2PO4) in excess ratios, the following reaction occurs:
NaOCl + NaH2PO4 HOCl + Na2HPO4 The presence of both NaH2PO4 and Na2HPO4 maintains the solution pH in the desired range 5.5-7.2. The reaction set forth above occurs immediately and produces a hypochlorous acid solution which is capable of rapidly killing spores at 20C. The resulting solution is relatively stable and is capable of providing the desired antimicrobial effect for periods of 24 hours or longer, depending upon incidental dilution or neutralization by organic soil such as human tissue.
Very little chlorine is released during the reaction because the pH of the sodium dihydrogen phosphate solution is preferably relatively high, i.e., 4.0-5Ø Furthermore, the reaction does not form chloroform because there is no source of carbon atoms in the reaction mixture. The absence of chloroform, a known toxic material, as a byproduct of the reaction is particularly desirable where the resulting hypochlorous acid solution is to be used in a hospital or clinical setting to sterilize medical devices and surfaces.
Due to the inherent instability and reactivity of hypochlorous acid, it can be expected to break down over time.
It has been shown that the hypochlorous acid solution produced in accordance with the present invention contains chlorine for as long as 5-8 days. Concentrations of buffered OCl-/HOCl as low as 20 ppm and 10 ppm have exhibited long term 2028~3~
stability. Higher initial concentrations of OCl- exhibit slightly greater stability. However, as set forth in the table below, low initial concentrations of OCl- provide the ~es~ire~a~s y ... . . . . . .. . ... ...
The following table showsthe relative stability of the hypochlorous acid (at initial levels of 20-500 ppm OCl- of the present invention:
Percent(%) Remaining Time (Hours) Available Hypochlorite o 100%
0.33 97-99 1.00 94-98 2.00 94-96 3.00 93-95 4.00 gl-94 6.00 90-92 8.00 87-91 12.00 85-88 24.00 78-82 The hypochlorous acid solution of the present invention provides a highly efficacious sterilizing solution for vinyl gloves, tygon tubing, amber latex rubber, the plastic of a blood bag, styrofoam packing material, hard plastic clothespins, glass, and other materials su~ as Lawton stainless steel.
In one example of the present invention, the hypochlorite solution comprises 0.25~ of hypochlorite ions (OCl-) by weight ~ . 9 _ _ _ _ _ 2~28~3~
at pH 11.0 and the buffering solution comprises 0.55 M
. _ _ _ , . . .. , . . . . . .. . . . . _ . _ . . . . ......... _ _ .. _ . _ . _ . , . _ .
~ NaH2PO4 at pH 4.5. The hypochiorous acid solution resulting~
from the mixing of equal volumes of the hypochlorite and buffering solutions is at 1250 ppm HOCl and has a pH of 7.0 + 0.2.
In a second example, the hypochlorite solution comprises 0.32% hypochlorite ions (OC1-) by weight at pH
12.5 and the buffering solution is 2.0M NaH2PO4 at pH 4.5.
When four ounces of each solution is mixed and diluted to 10 one gallon with deionized water, the resulting hypochlorous acid solution is at 100 ppm HOCl and has a pH of 6.0 + 0.2.
In a third example, the hypochlorite solution comprises one gallon of 0.25% hypochlorite ions (OC1-) by weight at pH
ll.S. The acidic buffer component consists of 4 oz. dry, 15 solid NaH2PO4 H2O- When the solid is dissolved in the hypochlorite solution, the mixture consists of 2500 ppm HOC1 and has a pH of 6.0-6.5.
Due to the relative stability of the hypochlorous acid solution of the present invention the amount of salt of 20 hypochlorite necessary to produce the desired hypochlorous - acid solution is relatively low. For Example, solutions having hypochlorite concentrations as low as 10 ppm hav ~28~3~) __ been found to provide effective results when combined with---- -------, , . . . . . ...................... .. . . _ . _ the appropriate buffer used in conjunction with the method~~ ~~~~~ ~~~
of the present invention. Accordingly, the cost of producing the hypochlorous acid solution according to the present invention is reduced in comparison to prior methods which produce unstable hypochlorous acid solutions.
This cost savings is amplified by the stability of the hy~ochlorous acid solution to be reused. Despite the stability of the resulting hypochlorous acid solution, it 10 has been found preferable to avoid prolonged use due to the introduction of biological tissues.
The hypochlorous acid solution of the present invention has also been found to be safe for use on plastic laminated surfaces, lacquered wood surfaces, glass, and laboratory 15 soapstone. There is no noxious odor associated with the use of the resulting hypochlorous acid solution, nor is there any visible salt residue. Thus, the hypochlorous acid can be used as a surface sterilant as well as an immersion sterilant.
In an alternative embodiment, a surfactant or other suitable wetting agent can be included in the system in order to enhance the effectiveness of the hypochlorous acid .. . . . .
~2~3~
__ of_ t'he present invention. The _nclusion of a surfactant or .. . .. .... , . . . ... . _ . .. . .. _ _ _ ... _ _ . .... _ _ . _ .. _ _ . _ _ . _ . _ _ _ wetting agent is of particular value where the hypochlorous~'--'~~'~~~~~
acid is used as a surface sterilant. For example, small amounts of methanol in the buffering solution would provide improved wetting characteristics~
In other alternative embodiments, the system may also contain buffering agents, perfumes, odorants, corrosion inhibitors, and lubricating agents. However, such agents must not interfere with the antimicrobial activity of the resulting hypochlorous acid solution, and preferably do not react with the hypochlorous acid to produce undesirable byproducts.
The hypochlorous acid solution produced in accordance with the present invention is particularly desirable for use in hospital and clinical environments for the reasons set forth above, i.e., long-term stability and low cost.
Medical instruments such as endoscopes must be properly sterilized between uses in order to avoid the transmission of microorganisms from one patient to another.
Accordingly, a hospital or clinical employee desirous of sterilizing a medical device will mix the hypochlorite .
.. ---- -- .. ........ .
~2893~
s,olut,ion,,,,,cont,aining a salt of_~ypochlorite_wi_h the_acidic _ _ _ _ _ _ buffer comprising, for example, sodium~dihydrogen phosphate, -as discussed in detail above. This mixing will immediately produce a sterilizing solution containing hypochlorous acid.
Mixing may be performed in a sterilizing pan or, in the alternative, may be performed in a separate mixing container such that the resulting hypochlorous acid is subsequently placed into the sterilizing pan. The medical devices can then be placed into the sterilizing pan containing the hypochlorous acid solution. Sterilization of surfaces can be effected by spraying the hypochlorous acid solution on the target surface and removing the hypochlorous acid solution at the end of a predetermined period.
The hypochlorous acid solution produced in accordance with the present invention provides a rapid rate of sterilization. The precise rate at which microorganisms will be killed by the hypochlorous acid solution varies in accordance with the concentration of HOCl and the presence of tissue and other foreign matter in the sterilizing solu-tion. However, a period of approximately one (1) minute hasbeen found to provide sterilization of medical instruments.
, _ .. . . _ .......................................... , , ,, . . .. _ _ _ . .. _ _ .
. , ~ . . . - . -~028~3a and surfaces. Sterilization using the hypochlorous acid solution of the present invention has been ~hown to occur in as little as ten (10) seconds.
~ . ... , .. . _._ . =, _ _ . _ _ _, _ _ -- , , _ . , _ . . _ , _ _ - In order to ensure--tha~ the~--hypo~ lorous acla . sDlutlon is sufficiently active to sterilize medical devices, it is desirable to test the solution in order to determine its relative activity. A starch-iodine-thiosulfate test can be used for this purpose. The starch-iodine-thiosulfate test utilizes well-known principles to determine the presence of a threshold amount of hypochlorite in a solution, as set forth in detail in Vogel, Te~tbook of Quantitative Inorqanic Analysis, t4th ed. 1978~ at pp. 382-83. Known methods for testing the solution's ability to kill spores may also be used (e.g., commercial spore strips).
In order to minimize the potential corrosive effects of the resulting hypochlorous acid solution, it may be desirable to provide a sacrific al aluminum tray to be used in conjunction with the sterilizing pan when the hypochlorous acid solution of the present invention is to be used to sterilize metallic devices. In this way, any corrosive effects of the hypochlorous acid are realized with respect to the aluminum tray rather than the medical devices which are placed therein.
A sterilizing kit in accordance with the present invention preferably includes a first solution of an inorganic hypochlorite salt and a second component containing, for ... . ... .. . .
__ _ __ - 14 _ ~_ _ _ _ 21~28~3~
example, a sodium dihydrogen phosphate buffer, as set forth .
in detail above. In addition, the sterilizing kit can include a test kit such ~s a starch-iodine-thiosulfate test to ~, . . ,, . . ~
----- determlne - whether--thre-sh-old~l-evel~ o-f =hyp~c~lc~l~e -are.~
. . , . _ . . .. , . .. . . ^ ^ ^ .. _ . = _, _ . . .. . . _ .. _ = . . . . ~, . _ _, _ . = . .. . . . . .
present. Where the kit is to be used for the sterilization of metailic devices, a sacrificial aluminum tray, as discussed above, can also be provided in the kit.
Although the present invention has been described herein with respect to the specific preferred embodiments, it will be evident that various and further modifications are possible without departing from the spirit and scope of the present invention.
_ ^. 15 - . ; .
Claims (26)
1. A chemical sterilant, comprising, a stable hypochlorous solution having a pH of 5.5-7.2, said stable hypochlorous solution consisting of the combination of a first component and a second component, said first component comprising a solution of a hypochlorite salt having a hypochlorite concentration of at least 10 parts per million and said second component selected from the group consisting of phosphoric acid, salts of phosphoric acid, acetic acid, and formic acid.
2. A chemical sterilant, as recited in claim 1, wherein said second component is a solution.
3. A chemical sterilant, as recited in claim 1, wherein said second component is a solid.
4. A chemical sterilant, as recited in claim 1, wherein said second component is sodium dihydrogen phosphate.
5. A chemical sterilant, as recited in claim 1, wherein the pH of said first component is 10-13.
6. A chemical sterilant, as recited in claim 2, wherein the pH of said second component is 4.0-5Ø
7. A chemical sterilant, as recited in claim 1, wherein said first component contains a wetting agent.
8. A chemical sterilant, as recited in claim 1, wherein said second component contains a wetting agent.
9. A chemical sterilant, as recited in claim 7, wherein said wetting agent is methanol.
10. A chemical sterilant, as recited in claim 8, wherein said wetting agent is methanol.
11. A chemical sterilant, as recited in claim 1, wherein said first component contains one or more buffering agents which do not interfere with the antimicrobial activity of said chemical sterilant.
12. A chemical sterilant, as recited in claim 1, wherein said second component contains one or more buffering agents which do not interfere with the antimicrobial activity of said chemical sterilant.
13. A chemical sterilant, as recited in claim 1, wherein said first component contains one or more perfumes which do not interfere with the antimicrobial activity of said chemical sterilant.
14. A chemical sterilant, as recited in claim 1, wherein said second component contains one or more perfumes which do not interfere with the antimicrobial activity of said chemical sterilant.
15. A chemical sterilant, as recited in claim 1, wherein said first component contains one or more odorants which do not interfere with the antimicrobial activity of said chemical sterilant.
16. A chemical sterilant, as recited in claim 1, wherein said second component contains one or more odorants which do not interfere with the antimicrobial activity of said chemical sterilant.
17. A chemical sterilant, as recited in claim 1, wherein said first component contains one or more corrosion inhibitors which do not interfere with the antimicrobial activity of said chemical sterilant.
18. A chemical sterilant, as recited in claim 1, wherein said second component contains one or more corrosion inhibitors which do not interfere with the antimicrobial activity of said chemical sterilant.
19. A chemical sterilant, as recited in claim 1, wherein said first component contains one or more lubricating agents which do not interfere with the antimicrobial activity of said chemical sterilant.
20. A chemical sterilant, as recited in claim 1, wherein said second component contains one or more lubricating agents which do not interfere with the antimicrobial activity of said chemical sterilant.
21. A method for producing a stable hypochlorous solution having a pH of 5.5-7.2, comprising, the mixing of a first component and a second component, said first component consisting of a solution of hypochlorite salt having a hypochlorite concentration of at least 10 parts per million, and said second component being selected from the group consisting of phosphoric acid, salts of phosphoric acid, acetic acid, and formic acid.
22. The method as recited in claim 21, wherein said second component is sodium dihydrogen phosphate.
23. The method as recited in claim 21, wherein the pH
of said first component is 10-13.
of said first component is 10-13.
24. The method as recited in claim 21, wherein the pH
of said second component is 4.0-5Ø
of said second component is 4.0-5Ø
25. A chemical sterilant, comprising, a stable hypochlorous solution having a pH of 5.5-7.2, said stable hypochlorous solution consisting of the combination of a first component and a second component, said first component comprising of a solution of a hypochlorite salt having a hypochlorite concentration of at least 10 parts per million and said second component selected from the group consisting of phosphoric acid, salts of phosphoric acid, and formic acid.
26. A method for producing a stable hypochlorous solution having a pH of 5.5-7.2, comprising, the mixing of a first component and a second component, said first component consisting of a solution of hypochlorite salt having a hypochlorite concentration of at least 10 parts per million, and said second component being selected from the group consisting of phosphoric acid, salts of phosphoric acid, and formic acid.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2028930 CA2028930A1 (en) | 1990-10-30 | 1990-10-30 | Stable hypochlorous acid sterilizing solution and kit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2028930 CA2028930A1 (en) | 1990-10-30 | 1990-10-30 | Stable hypochlorous acid sterilizing solution and kit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2028930A1 true CA2028930A1 (en) | 1992-05-01 |
Family
ID=4146298
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2028930 Abandoned CA2028930A1 (en) | 1990-10-30 | 1990-10-30 | Stable hypochlorous acid sterilizing solution and kit |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2028930A1 (en) |
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2835702A1 (en) * | 2002-02-12 | 2003-08-15 | Dominique Mercier | Disinfectant composition useful in the disinfection of water comprises a mixture of sodium hypochlorite and sodium monophosphate |
| FR2869308A1 (en) * | 2004-04-27 | 2005-10-28 | Dominique Mercier | Chlorinated water for cleaning/disinfecting pipes has added monosodium phosphate anhydride for extra anti-scale and anti-corrosion properties |
| WO2007048885A1 (en) * | 2005-10-27 | 2007-05-03 | Dominique Mercier | Additive for javelle water |
| WO2009100870A2 (en) * | 2008-02-12 | 2009-08-20 | Actides Gmbh | Method for producing a disinfectant on the basis of hypochlorous acid and transportable system for producing such a disinfectant |
| GB2477597A (en) * | 2010-02-03 | 2011-08-10 | Mauve Technology Ltd | Disinfectant materials and methods |
| GB2486454A (en) * | 2010-12-15 | 2012-06-20 | Biomimetics Health Ind Ltd | A stable composition of hypochlorous acid (HOCl), its production and uses thereof |
| GB2488838A (en) * | 2011-03-11 | 2012-09-12 | Biomimetics Health Ind Ltd | A stable antimicrobial aqueous hypochlorous acid solution |
| CN104555928A (en) * | 2015-01-09 | 2015-04-29 | 上海日洁环境科技有限公司 | Method for producing stable hypochlorous acid solution |
| CN111937900A (en) * | 2020-08-20 | 2020-11-17 | 开平市美康泉生物科技有限公司 | High-stability molecular hypochlorous acid disinfectant and preparation method thereof |
| US10897905B2 (en) | 2016-01-26 | 2021-01-26 | Metrex Research, LLC | Hypochlorite based hard surface disinfectants |
| US11103840B2 (en) | 2018-03-19 | 2021-08-31 | Process Cleaning Solutions Ltd. | Mixing and dispensing device and method |
| EP3881678A3 (en) * | 2020-02-27 | 2022-01-19 | Wen Chung Shiao | Hypochlorous acid disinfectant and its production method |
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1990
- 1990-10-30 CA CA 2028930 patent/CA2028930A1/en not_active Abandoned
Cited By (20)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2835702A1 (en) * | 2002-02-12 | 2003-08-15 | Dominique Mercier | Disinfectant composition useful in the disinfection of water comprises a mixture of sodium hypochlorite and sodium monophosphate |
| FR2869308A1 (en) * | 2004-04-27 | 2005-10-28 | Dominique Mercier | Chlorinated water for cleaning/disinfecting pipes has added monosodium phosphate anhydride for extra anti-scale and anti-corrosion properties |
| WO2007048885A1 (en) * | 2005-10-27 | 2007-05-03 | Dominique Mercier | Additive for javelle water |
| WO2007048941A2 (en) * | 2005-10-27 | 2007-05-03 | Dominique Mercier | Method of using an additive for water chlorinated with javelle water |
| WO2007048941A3 (en) * | 2005-10-27 | 2007-11-01 | Dominique Mercier | Method of using an additive for water chlorinated with javelle water |
| WO2009100870A2 (en) * | 2008-02-12 | 2009-08-20 | Actides Gmbh | Method for producing a disinfectant on the basis of hypochlorous acid and transportable system for producing such a disinfectant |
| WO2009100870A3 (en) * | 2008-02-12 | 2009-11-26 | Actides Gmbh | Method for producing a disinfectant on the basis of hypochlorous acid and transportable system for producing such a disinfectant |
| GB2477597B (en) * | 2010-02-03 | 2012-01-11 | Mauve Technology Ltd | Disinfectant materials and methods |
| WO2011095809A1 (en) | 2010-02-03 | 2011-08-11 | Mauve Technology Ltd. | Disinfectant materials and methods |
| GB2477717A (en) * | 2010-02-03 | 2011-08-17 | Mauve Technology Ltd | Disinfectant materials and methods |
| GB2477597A (en) * | 2010-02-03 | 2011-08-10 | Mauve Technology Ltd | Disinfectant materials and methods |
| US8883222B2 (en) | 2010-02-03 | 2014-11-11 | Mauve Technology Limited | Disinfectant materials and methods |
| GB2486454A (en) * | 2010-12-15 | 2012-06-20 | Biomimetics Health Ind Ltd | A stable composition of hypochlorous acid (HOCl), its production and uses thereof |
| GB2488838A (en) * | 2011-03-11 | 2012-09-12 | Biomimetics Health Ind Ltd | A stable antimicrobial aqueous hypochlorous acid solution |
| CN104555928A (en) * | 2015-01-09 | 2015-04-29 | 上海日洁环境科技有限公司 | Method for producing stable hypochlorous acid solution |
| US10897905B2 (en) | 2016-01-26 | 2021-01-26 | Metrex Research, LLC | Hypochlorite based hard surface disinfectants |
| US11103840B2 (en) | 2018-03-19 | 2021-08-31 | Process Cleaning Solutions Ltd. | Mixing and dispensing device and method |
| EP3881678A3 (en) * | 2020-02-27 | 2022-01-19 | Wen Chung Shiao | Hypochlorous acid disinfectant and its production method |
| US11638429B2 (en) | 2020-02-27 | 2023-05-02 | Super Aqua International Co., Ltd. | Hypochlorous acid disinfectant and its production method |
| CN111937900A (en) * | 2020-08-20 | 2020-11-17 | 开平市美康泉生物科技有限公司 | High-stability molecular hypochlorous acid disinfectant and preparation method thereof |
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