MXPA00007647A - Electrolytic synthesis of peracetic acid and other oxidants - Google Patents

Abstract

An electrolysis unit (10) has an ion selective barrier (20) for separating an anodic chamber (12) from a cathodic chamber (14). An electrolyte within the unit includes a precursor, such as potassium acetate, or acetic acid. A positive potential is applied to an anode (16) within the anodic chamber, resulting in the generation of a variety of shorter and longer lived oxidizing species, such as peracetic acid, hydrogen peroxide, and ozone. In one preferred embodiment, a solution containing the oxidizing species is transported to a site where articles, such as medical instruments, are to be decontaminated. The oxidizing species are generated as needed, avoiding the need to store hazardous decontaminants.

Description

> ? ELECTROLYTIC SYNTHESIS OF PERACYTIC ACID AND OTHER OXIDANTS BACKGROUND OF THE INVENTION The present invention relates to sterilization and disinfection techniques. It finds particular application in relation to electrochemically produced solutions containing oxidizing agents such as, for example, peracetic acid, hydrogen peroxide, and ozone, for the sterilization or disinfection of medical and pharmaceutical equipment, and will be described with particular reference thereto. It will be noted, however, that the invention can also be applied to other methods of sterilization, disinfection, and hygiene employing such oxidizing agents, including the treatment of water, food, food serving equipment, and the like. Oxidizing agents such as peracetic acid, hydrogen peroxide and ozone are useful disinfectants and sterilizers for various applications. Peracetic acid has several uses, including disinfection of waste and sterilization of medical equipment, containers, food processing equipment, and the like. Peracetic acid poses few waste problems since it decomposes into easily degraded compounds in sewage treatment plants. It has a broad spectrum of activity against microorganisms and is effective even at low temperatures. Hydrogen peroxide is used to sterilize medical equipment. Ozone has been used extensively for disinfection and water treatment, and, more recently, for the treatment of food and equipment to serve food. Conventionally, to form peracetic acid, peracetic acid precursors are mixed with water and other chemicals in a bath. The elements to be decontaminated, either by sterilization or by disinfection, are then immersed in the bath for a sufficient period of time to effect the required degree of decontamination. The decontaminated elements are then typically rinsed before use. To ensure effective sterilization or disinfection within a preselected period of time, the concentration of peracetic acid is maintained above an effective minimum level, typically around 2300 ppm for the sterilization of medical instruments. When the concentration of peracetic acid is at the effective minimum level or above said effective minimum level for sterilization, complete sterilization is expected. Lower levels of peracetic acid are effective as disinfectants. Concentrations from 2-10 ppm, or less, are effective for disinfection purposes, which requires only the destruction of pathogenic microorganisms. In installations in which the elements must be sterilized or disinfected at frequent intervals during the day, the same batch of peracetic acid solution is frequently used repeatedly. However, peracetic acid tends to decompose with the passage of time. For example, a bath which is above the minimum effective concentration of peracetic acid for sterilization of about 2300 ppm at the beginning of a day often falls to about 800 ppm, well below the effective concentration, without additional additions of the precursors of peracetic acid. High ambient temperatures, the number of elements sterilized or disinfected, and the degree of contamination of the elements, all contribute to the reduction of the useful life of the bath. In addition, storage conditions frequently lead to the degradation of peracetic acid precursors before use. In addition, precursors are often hazardous materials that sometimes pose problems in the case of shipping and storage. Due to the storage risks and also due to the fact that they degrade over time, it is preferable to keep a limited supply of the precursors and to order them again at frequent intervals. In the case of hydrogen peroxide and ozone, similar problems arise. Ozone is a species that has an especially short life that decomposes easily. Hydrogen peroxide tends to decompose in water and oxygen. EP 0658 763 A discloses the use of peracetic acid mixed with hydrogen peroxide and acetic acid as a disinfectant. The concentration of peracetic acid is monitored electrochemically. Recently, the cleaning and decontamination properties of solutions formed by the electrolysis of water under special conditions have been explored. Electrolysis devices are known which receive a water supply such as tap water, commonly doped with a salt, and perform water electrolysis. During electrolysis, an anolyte solution is produced from water doped at an anode and a catholyte solution is produced at a cathode. Examples of such water electrolysis units are described in U.S. Patent Nos. 5,635,040; 5,628,888; 5,427,667; 5,334,383; 5,507,932; 5,560,816; and 5,622,848. EP 0 115 893 A of Battelle Memorial Institute discloses a sterilization apparatus that produces a solution of sodium hypochlorite from sodium chloride in an electrochemical cell. To create these anolyte and catholyte solutions, tap water, often with the addition of electrical or ionically conductive agents such as halogen salts including the sodium chloride and potassium chloride salts, passes through an electrolysis unit or module that has at least one anodic chamber and at least one cathodic chamber, generally separated from each other by a partially permeable barrier. An anode makes contact with the water flowing in the anodic chamber, while a cathode makes contact with the water flowing in the cathodic chamber. The anode and the cathode are connected to a source of electric potential to expose the water to an electric field. The barrier can allow the transfer of species that carry electrons between the anode and the cathode but limits the movement defined between the anodic and cathodic chambers. The salt and minerals naturally present in the water and / or added to the water are subjected to oxidation in the anodic chamber and subjected to reduction in the cathodic chamber. A resulting anolyte at the anode and a catholyte resulting at the cathode can be removed from the electrolysis unit. The anolyte and the catholyte can be used individually or as a combination. The anolyte has antimicrobial properties including antiviral properties. The catholyte has cleaning properties. However, electrochemically activated water has limitations. The electrochemically activated water has a high surface energy which does not easily allow the penetration of electrochemically activated water into cracking areas of medical instruments. Thus, complete destruction of germs can not be achieved. Additional problems arose in the case of metal surfaces that come into contact with electrochemically activated water, including surfaces of decontamination equipment and metal medical devices. Electrochemically activated water is corrosive to certain metals. Stainless steel, used to produce many medical devices, is especially susceptible to corrosion caused by electrochemically activated water. Other chemicals can also be used for electrochemical conversion. EP 0 244 565 A discloses the treatment of water with electrolytically generated ozone. Khomutov et al. ("Study of the Kinetics of Anodic Processes in Potassium Acétate," (Study of the Kinetic Characteristics of Anodic Processes in Potassium Acetate), Izv. Vyssh, Uchebn, Sabed., Khim. Teknol, 31 (11) pp. 71-74. (1988)) discloses a study of the conversion of acetate solutions into peracetic acid and acetyl peroxide in the temperature range of -10 ° C to 20 ° C using a three-electrode cell. The anode and cathode regions of the Khomutov et al. Cell were separated by a porous glass barrier. Platinum, gold or carbon anodes, at a potential of 2-3.2 V in relation to a silver / silver chloride reference electrode, were used in the study. Concentrations of potassium acetate were initially 2-10 mol / L. From measurements of conductivity and viscosity, Khomutov et al., Estimated that peracetic acid solutions were generated at the anode with active oxygen concentrations of 0.1 gram equivalent / L. However, they did not perform direct measurements of the concentration of peracetic acid in the overall solution. In addition, the pH range of 8.2-10.4 reported by Khomutov et al., Is undesirable for many practical decontamination solutions. To reduce the corrosion of the metal components of the instruments to be decontaminated, a pH close to the neutral is desired. The present invention offers a novel and improved system for generating peracetic acid and other oxidizing agents, said method overcomes the aforementioned problems as well as other problems. COMPENDIUM OF THE INVENTION In accordance with one aspect of the invention, a method for microbial decontamination is provided. The method includes the electrochemical generation of an antimicrobial solution containing an oxidizing species. The method includes separating an anode chamber and a cathodic chamber from an electrochemical cell with a barrier substantially impermeable to the oxidizing species. The method further includes the application of a positive potential to an anode in the anodic chamber to convert a precursor into an electrolyte adjacent to at least one of the anode and cathode to the oxidizing species. The method is characterized by the electrochemical generation of peracetic acid as at least one significant component of the oxidizing species. The concentration of peracetic acid in the antimicrobial solution is about 10 ppm or more. The method further includes transporting the antimicrobial solution containing peracetic acid along a fluid flow path to a site in which the elements to be microbially decontaminated and contacting the elements with the acid-containing antimicrobial solution. peracetic for the purpose of microbially decontaminating said elements. In accordance with another aspect of the present invention, a system for antimicrobial decontamination of devices is provided. The system includes an electrochemical cell that includes an anode and a cathode separated by a barrier substantially impermeable to an oxidizing species. A source of electrical potential is connected to at least one of the anode and cathode. An electrolyte is adjacent to at least one of the anode and cathode. The system is characterized by a precursor in the electrolyte that can be converted to peracetic acid in a concentration of about 10 ppm or more by applying a potential to at least one of the anode and cathode, the oxidizing species includes peracetic acid. A fluid flow path is provided to transport the generated peracetic acid from the electrochemical cell to a site at which a device must be microbially decontaminated through the peracetic acid. An advantage of the present invention is that it allows the in situ preparation of peracetic acid solutions, as desired. Another advantage of the present invention is that the storage and transport of hazardous sterilants is avoided. Another advantage of the present invention is that it allows maintaining the concentration of peracetic acid in a microbial decontamination bath during repeated use of the bath. Other advantages of the present invention will be apparent to persons with certain knowledge in the art upon reading and understanding the following detailed description of the preferred embodiments. BRIEF DESCRIPTION OF THE DRAWINGS The invention can take the form of several components and arrangements of components, in several steps and arrangements of steps. The drawings are for the sole purpose of illustrating a preferred embodiment and are not to be construed as limiting the invention. Figure 1 is a schematic diagram of a preferred embodiment of an electrolysis unit for the generation of sterilizing and disinfecting solutions of the present invention; Figure 2 is a top view of an electrolysis unit of the present invention; and Figure 3 is a plumbing diagram of a sterilization or disinfection system including the electrolysis unit of Figure 1, a reagent cup reception well and a reagent cup. DETAILED DESCRIPTION OF THE PREFERRED MODALITIES With reference to figures 1 and 2, an electrochemical cell or electrolysis unit 10 generates oxidizing species for use as sterilizers and liquid disinfectants such as for example peracetic acid, hydrogen peroxide, and ozone. The unit 10 includes two electrode chambers, namely an anode chamber 12 and a cathode chamber 14. An electrode is placed in each of the chambers. Specifically, an anode 16 is supported within the anodic chamber and a cathode 18 is supported within the cathode chamber. A barrier or membrane 20 connects the anodic and cathodic chambers 12, 14 and controls the flow of dissolved species therebetween. The barrier is preferably substantially impermeable to at least one of the oxidizing agents. A preferred barrier is a membrane specific for ions, such as for example a proton-permeable membrane, which allows the migration of hydrogen ions between the chambers but limits the mixing of other species within the two chambers. A membrane permeable to protons of this type NAFION® 117, is available from DuPont and Aldrich. Alternatively, filter paper, such as for example P-5 filter paper of the Fisher brand, is used for the barrier 20. A source of electric potential 22 applies a positive potential to the anode. The positive potential is selected to be high enough for the generation of oxidizing species at the anode, without simply causing the dissociation of water into oxygen and hydrogen at the electrodes. A potential of approximately +1.6 to +5 volts, relative to Ag / AgCl in 3M NaCl is preferred for this purpose, with a potential of approximately 3.2V being particularly preferred. For the generation of oxidizing species, at least the anodic chamber 12 receives an electrolyte solution. The electrolyte solution includes a precursor that is oxidized in the oxidizing species in the anodic chamber. Solutions formed from the electrolyte solution in the anodic and cathodic chambers during electrolysis are known as anolyte and catholyte, respectively. In the case of the generation of peracetic acid, for example, the anolyte comprises a solution of peracetic acid. Other oxidizing species may also be present.

Optionally, a precursor tank or containment tank 24 is provided in fluid communication with the anodic chamber to contain a solution of the precursor. The precursor solution is supplied to the anodic chamber from the containment tank by means of a pump, gravity feed, or other suitable means. Alternatively, a solid precursor in solution is brought into the anodic chamber as will be described in detail below. The anode 16 preferably has a large surface area and includes a material that facilitates the formation of oxidizing species at the anode. Suitable materials include, but are not limited to, carbon (including graphite), platinum, iridium, lead dioxide, and ruthenium oxide. In the case of lead dioxide or ruthenium oxide, the oxide is preferably placed on a substrate, such as, for example, titanium wire mesh or another noble metal substrate, which supports the oxide and offers the anode a large area surface for the generation of oxidizing species. Shepelin, et al., (Élektrokhimiva, volume 26, No. 9., pages 1142-1148 (1990)) and Chernik et al., (Elektrokhimiva, Vol. 33, No. 3, pages 289-292 (1997) ) disclose lead dioxide electrodes for the electrosynthesis of ozone. The cathode is formed from any suitable electron acceptor such as platinum, titanium, gold or carbon (including graphite). Carbon, such as graphite, is particularly preferred for the generation of hydrogen peroxide, while platinum is preferred for the generation of peracetic acid. Optionally, the anodic chamber is fluidly connected to a reference electrode 26, such as silver / silver chloride to ensure that the selected applied potential is maintained. Pressure relief valves 28 and 30 are optionally provided to relieve excessive pressure buildup within the anodic and cathodic chambers. In the generation of peracetic acid, for example, the oxidizing species generated in the anodic chamber may include several species, both short-lived and longer-lived, which react directly with the peracetic acid precursor to form peracetic acid or which they participate in reaction schemes that lead to the formation of peracetic acid from the precursor. Such additional species include ozone, a short-lived but highly oxidizing species, and hydrogen peroxide, a species that has a longer life that is an important intermediate in conventional methods of peracetic acid synthesis. Optionally, an amount of hydrogen peroxide is added to the electrolyte in the anodic chamber as an initiator to initiate the reaction or combination of reactions resulting in the formation of peracetic acid. A peroxide chamber 32 in fluid communication with the anodic chamber supplies said hydrogen peroxide to the chamber. Other chemicals can also be added to the anodic chamber as initiators, such as perborate, which raises the concentration of hydrogen peroxide in the anolyte solution. Preferred peracetic acid precursors include acetic acid and other acetyl donors, such as, for example, sodium acetate, potassium acetate, acetic acid and acetaldehyde. A particularly preferred donor of acetyl is potassium acetate. Potassium acetate is also an effective donor, but it tends to be less soluble in the electrolyte. When acetic acid is used as a precursor, it is preferably added to the anodic chamber at an addition rate such that maintenance of the pH is allowed within the range selected for the generation of oxidizing species. The dropwise addition of acetic acid at the same rate at which it is consumed is a suitable form of addition. The preferred concentration of the precursor in the electrolyte depends on the solubility of the precursor and the desired concentration of oxidizing species. In the case of the formation of peracetic acid from potassium acetate, for example, the concentration of potassium acetate in the electrolyte is preferably within the range of about 0.5M to about 5M. A regulation system is optionally added to the electrolyte in the anodic chamber to maintain the electrolyte at an appropriate pH level to generate the desired oxidant species. The particular oxidizing species by intermediates generated and their respective concentrations depend, to some extent, on the selected pH. At an approximately neutral pH, that is, from about pH 6 to about pH 8, the generation of ozone is favored. As the pH rises, the generation of hydrogen peroxide increases. Thus, in the case of hydrogen peroxide, an electrolyte with a slightly alkaline pH, preferably around 7-9, with a pH of 8 or slightly higher than this value being preferred. For the preparation of dilute solutions of oxidizing species suitable for use as sterilizers and disinfectants, an approximately neutral pH is preferred. Alkali metal phosphates are suitable regulators. A preferred regulatory system includes a combination of monosodium phosphate, disodium phosphate and tripolyphosphates. Said regulation system also provides anticorrosion properties. Another preferred regulatory system includes one or more potassium phosphates. Sodium hydroxide can be added to raise the pH. Other regulation systems or pH adjusters useful in the generation of ozone and peracetic acid include sulfuric acid and perchlorate. The electrolyte used in the anodic and cathodic chambers is preferably the same, in terms of the regulators and other additives employed, even when different electrolytes are also contemplated. Preferably, the pressure inside the cell is greater than the atmospheric pressure. By way of example, electrolysis under pressure of 10 p.s.i.g. (0.7 kg / cm2) approximately doubles the production rate of peracetic acid from potassium acetate, compared to electrolysis performed at atmospheric pressure, and it is considered that greater increases can be obtained at even higher pressures. Optionally, an agitator 34, such as a magnetic or mechanical stirrer, agitates the anolyte. The temperature of the anolyte solution is preferably within the range of about the freezing point of the anolyte to about 60 ° C, depending on the composition of the anode and the species to be generated. For the generation of peracetic acid, a temperature of from about 0 ° C to about 60 ° C is preferred. To maintain the temperature within this range, the electrolysis unit is optionally cooled, such as by immersion in an ice bath, or other cooling device, or by circulation of a portion of the anolyte and catholyte through a heat exchanger. Alternatively, the temperature is maintained by removing a portion of the anolyte at intervals, either continuously, and by replenishing it with a fresh solution of precursor, or by recirculating the anolyte through a decontamination system as will be discussed with more details later. Alternatively, electrolysis is carried out at temperatures ranging from ambient temperature and above said temperature, avoiding the need for refrigeration. When heated decontaminant solutions are desired, the sterilants and disinfectants are optionally generated in a heated electrolysis unit. Additives of corrosion inhibition and reduction of surface energy are optionally introduced into a solution of peracetic acid, either by its addition to the anolyte before electrolysis either during said electrolysis or afterwards. Other additives, including, but not limited to, detergents, chelating agents and sequestering agents, they can also be added to the solution, either in combination with the other additives, or separately. The corrosion inhibiting agents are selected in accordance with the nature of the materials in the elements to be cleaned and / or decontaminated with the oxidizing species. Corrosion inhibitors that protect against corrosion of aluminum and steel, including stainless steel, include phosphates, sulfates, chromates, dichromates, borates, molybdates, vanadates, and tungstates. Some additional inhibitors of aluminum corrosion include 8-hydroxyquinoline and ortho-phenylphenol. More specifically, phosphates are preferred for the corrosion inhibition of stainless steel. Preferred phosphates include, but are not limited to, monosodium phosphate (MSP), disodium phosphate (DSP), sodium tripolyphosphate (TSP), sodium hexametaphosphate (HMP), and sodium sulfate, either alone or in combination. Preferred borates include sodium metaborate (NaB02). Copper and bronze corrosion inhibitors include triazoles, azoles, benzoates, tolyltriazoles, dimercaptothiadiazoles, and other 5-membered ring compounds. Especially preferred copper and bronze corrosion inhibitors include sodium salts of benzotriazole and tolyltriazole that are preferred because of their stability in the presence of strong oxidizing compounds. It is also possible to use mercaptobenzothiazole but it has a propensity to be oxidized or destabilized by strong oxidants. Salicylic acid is an example of an acceptable benzoate corrosion inhibitor. In hard water, phosphate regulators and corrosion inhibitors tend to cause the calcium and magnesium salts present in hard water to be classified and coated in the process of decontamination and / or cleaning, and also to leave deposits in parts of the system of electrolysis. In these cases, an appropriate sequestering agent is preferably provided to avoid precipitation such as sodium hexametaphosphate (HMP), or trisodium nitrolotriacetic acid (NTA NA3). Since sodium hexametaphosphate is also a corrosion inhibitor, it serves a dual purpose, both as a corrosion inhibitor and as a sequestering agent. Other sequestering agents include sodium polyacrylates. Obviously, if mild or deionized water is used, the sequestering agent can be eliminated. However, to ensure a universal application capacity with any water that may be employed, the presence of a sequestering agent is preferred. A surface energy reducing agent is optionally added to the peracetic acid solution to increase the crack penetration of the elements to be treated. This is particularly important when cleaning and decontaminating complex medical instruments that may contain microbial contaminants in cracks, joints, and lumens. Surface energy reducing agents that can be employed in accordance with the present invention include various wetting agents. Such wetting agents include anionic, cationic, nonionic, amphoteric and / or zwitterionic surfactants. Specific classes of wetting agents that are useful include anionic and nonionic surfactants or combinations thereof. Examples of nonionic wetting agents that may be employed in the present invention include surfactants such as polyglycol ethers of fatty alcohols, nonylphenoxypoly (ethyleneoxy) ethanol, and ethoxylated polyoxypropylene. Specific examples include Genapol UD-50®, Igepal®, Fluowet®, and Pegal®. The wetting agents presented above can be used alone or in combination with each other. The amounts of corrosion inhibitor and wetting agents to be added to the peracetic acid solution will vary according to the type of agent added and whether or not one or more agents are added. Inorganic corrosion inhibitors are preferred present in amounts that fall within a range of from about 0.1% to about 20.0% by weight per volume (weight / volume). Organic corrosion inhibitors are present preferably in amounts ranging from approximately 0.01% to 5.0% weight / volume. The phosphates are effective in concentrations within a range of about 0.01% to about 11.0% weight / volume. Wetting agents are preferably present in amounts ranging from about 0.0001% to about 5.0% weight / volume. More preferably, the wetting agent is present in amounts that are within a range of about 0.0001% to about 0.5% weight / volume. In a closed system, under pressure, a septum optionally allows the removal of anolyte samples for chemical analysis for the monitoring of concentrations of oxidizing species, precursors, or other additives. The electrolysis unit 10 described in this way has a wide variety of uses. Diluted solutions of the generated oxidant species, such as peracetic acid, are used for sterilization or disinfection, even when the peracetic acid, or other oxidizing species generated, is optionally used for other purposes. In a preferred embodiment, the unit is used to generate batches of peracetic acid solution that can be used immediately, to disinfect or sterilize elements, or can be stored for later use. The acetic acid or other precursor is added to the unit and a corresponding oxidant potential is applied until a desired concentration of peracetic acid is obtained. The applied potential is then suspended and the solution leaves the anodic chamber through an outlet line 36. At relatively low pressures, the unit readily produces suitable peracetic acid concentrations for disinfection purposes. Concentrations of peracetic acid of 10-20 ppm, ozone concentrations up to about 1.6 ppm, and hydrogen peroxide concentrations of up to about 10 ppm are easily obtained. At higher pressures, more concentrated solutions of peracetic acid are optionally generated. In another embodiment, which is shown in Figure 2, the unit is used to produce a stream of peracetic acid solution, which is removed from the anodic chamber as it is generated through an outlet line 36 and brought directly to the cells. elements to decontaminate. An entry line 38 fills the anodic chamber with a solution that includes the peracetic acid precursor. The modality is suitable for various purposes, such as decontaminating equipment, including equipment for processing food and for pharmaceutical purposes, to disinfect packaging such as food containers, and to sterilize waste and water. A third embodiment includes the recirculation of a sterilizing or disinfecting solution from a container comprising elements to be sterilized or disinfected, through the anodic chamber of the electrolysis unit and back to the container. The solution is preferably recirculated in this way until the desired concentration of peracetic acid is achieved. Once the desired concentration is achieved, the recirculation can proceed intermittently to maintain the desired concentration of peracetic acid. Alternatively, the solution is continuously recirculated and the positive potential applied intermittently to maintain the concentration. With reference to Figure 3, a system for recirculating oxidizing species, such as for example peracetic acid, through a decontamination system includes the electrolysis unit 10 and a microbial decontamination apparatus A, configured to settle on the upper part of a counter or another convenient work surface. While the system is described herein with particular reference to peracetic acid, it will be noted that by varying the composition of the precursor, the pH, electrode materials, and the like, as previously described and alternatively employ different oxidizing species or combinations thereof. A door or lid 40 can be manually opened to provide access to a tray 42 that defines a reception region 44 for receiving elements to be decontaminated for microbes. In the illustrated embodiment, the tray 42 is configured to receive devices such as endoscopes or other elongated roller elements. Other trays with regions receiving elements of different configurations to receive the elements themselves or containers containing the elements are also contemplated. A well 46 preferably receives a unit dose of reagents to form a sterilant solution, disinfectant, or another type of microbial decontamination. The dose of reagents includes a precursor of peracetic acid, preferably in solid form, such as for example sodium or potassium acetate. Alternatively, the peracetic acid precursor, which may be in the liquid or solid state, is added to the electrolysis unit from the container 24, or by any other suitable means. A package C containing a reagent, which contains the dose of reagent, is inserted into the well 46. Optionally, the peracetic acid precursor is contained separately from the other reagents within the cup. Once the elements are loaded in the tray and once the package C carrying the reagent is inserted in the well, the lid 40 is closed and blocked. A lower opener projection or member 48 is placed at the bottom of the well 46 to engage a lower surface of the package C as it is inserted into the well. The projection 48 cuts or otherwise creates an opening in the cup, allowing circulating water to dissolve or entrain the dose of reagents. Water and reagents circulate through the electrolysis unit until a selected concentration of peracetic acid is reached. Optionally, a fluid valve 50 passes the water through a microbe removal filter 52 into flow paths of a fluid circulation system. The microbial removal filter 52 blocks the passage of all particles of approximately 0.2 μ or more. The incoming water, which has passed through the filter, is directed through a spray or distribution nozzle 54 and fills the receiving region of element 44 in the tray 42. As additional water is received, it flows into the well 46 by dissolving the solid reagents or dragging the liquid reagents, in the C cup, forming a solution. The filling continues until all the air is pushed through an air system 56 and until a total interior volume is filled with the water. After the closing of the filling valve 50, a pump 58 circulates the fluid through the receiving region of element 44 of the tray, the well 46, the electrolysis unit 10, and, optionally, a heater 60. The The pump also pushes the antimicrobial solution through the filter 52 to a check valve 62 for filter decontamination. In addition, the pump pushes the antimicrobial solution through another microbe filter 64 in the air system 56 to a check valve 66. The circulation continues until sterilization or disinfection is achieved. A peracetic acid concentration sensor 68 optionally detects the concentration of peracetic acid in the decontamination apparatus A. In a preferred embodiment, the concentration sensor controls the application of the potential through the anode 16 and cathode 18. In an alternative embodiment, The concentration sensor controls the valves directing the flow through and around the electrolysis unit 10 to the control concentrations in the decontamination apparatus. When the decontamination is completed, a drain valve 70 is opened, allowing the solution to drain. Optionally, the drain valve is connected fluidly on the electrolysis unit to bring the peracetic acid solution used back to the unit for the destruction of oxidizing species. Air is drawn through the microbe filter 64 in such a way that a sterile air replaces the fluid within the system. Then, the drain valve is closed and the fill valve 50 is opened again to fill the system with a sterile rinsing fluid.

While not intending to limit the invention, the following examples are illustrative of the methods of preparing the antimicrobial solutions containing one or more oxidizing agents. EXAMPLE 1 Generation of hydrogen peroxide and ozone in sodium hydroxide The electrolysis unit of Figure 1 was used to generate hydrogen peroxide and ozone. A pure graphite rod having a surface area of 21 cm 2 was used as the cathode. Before use, the cathode was anodized through the following procedure. The cathode was placed in 0.05 M KH2P04 and the pH was adjusted to 6.88 with NaOH. A + 1.6V potential was applied to the cathode versus an Ag / AgCl reference electrode in 3M NaCl until a total charge of 0.566 C / cm2 was passed. A potential of - 1.5 volts was then applied to the cathode for 1 minute. The anodized cathode was then inserted into the electrolysis unit, together with a platinum anode. 0.1M NaOH was emulated at a pH of 12.54 as a precursor. A NAFION 117 proton exchange membrane 20 separated the cathodic and anodic chambers. Air was sprayed through the catholyte for 30 minutes. A potential of + 1.6V versus the reference electrode was then applied to the platinum anode for 30 minutes while air was still being sprayed. The potential was then raised to '2.5 V and maintained for an additional 18.5 hours. Concentrations of hydrogen peroxide were measured using a CHEMetrics CHEMets analyzer. No hydrogen peroxide or ozone was detected in one hour. After 19.5 hours, measurable amounts of these oxidizing agents were observed. (0.6 ppm of 03 in the catholyte, 2 ppm of H202 in the anolyte). EXAMPLE 2 Generation of peracetic acid from potassium acetate at an alkaline pH The electrolysis unit of Figure 1 was employed in the generation of peracetic acid from a 5M solution of potassium acetate at a pH of 9.15. Two sheets of filter paper P-5 of the Fisher brand were used as a barrier. The anode and the cathode were both platinum, with a surface area of 16.8 cm2. An ice bath cooled the electrolysis unit to a temperature of about 8-12 ° C. The anode was maintained at a potential of + 3.2V. The concentration of peracetic acid was measured spectrophotometrically over a period of 2 hours in terms of absorbency. After 60 minutes, the peracetic acid concentration was raised from an initial absorbance of 0.008 abs to 0.010 abs. After 2 hours, the absorbency was 0.012 abs. EXAMPLE 3 Generation of peracetic acid from potassium acetate at a pH close to neutral The procedures used in example 2 were repeated, except as indicated. Anolyte and catholyte were prepared by the addition of sulfuric acid to 5M potassium acetate, to bring the pH to 7.2. The precipitate of potassium sulfate was removed and the solution was introduced into the electrolysis unit. A + 3.2V potential was applied to the anode versus the reference electrode. (Actual voltage applied 9.6V). Measurements of peracetic acid, hydrogen peroxide and ozone were made. After 60 minutes, the anolyte peracetic acid concentration was 10.34 ppm and the concentration of hydrogen peroxide was 3 ppm. After 2 hours an ozone concentration of 1.6 ppm was detected. The concentration of peracetic acid reached 13.79 ppm after 90 minutes, but subsequently, suggesting a migration of oxidizing agents to the catholyte. EXAMPLE 4 Generation of peracetic acid from potassium acetate at an almost neutral pH in the presence of potassium fluoride and monosodium phosphate The procedure of Example 3 was followed, except as indicated. The electrolyte was prepared using 5M potassium acetate, 0.2 g / L of potassium fluoride, and a 0.5 M monosodium phosphate solution. Sulfuric acid was added to bring the pH to 7.14. Measurements of peracetic acid and ozone were made. After 60 minutes, at a potential of + 2.5V versus the reference electrode (real voltage applied 9.6V), the concentration of peracetic acid in the anolyte was 6.33 ppm (0.010 abs). After 90 minutes, the concentration was 10.13 ppm (0.011 abs.). An ozone concentration greater than 1 ppm was detected after 2 hours. EXAMPLE 5 Generation of peracetic acid and ozone at pressure above atmospheric pressure The procedures of Example 3 were employed, except as indicated. The pressure of the anolyte was maintained at a level between 2 and 6 p.s..g., and a NAFION PEM filter was used for the barrier 20. The 5M potassium acetate electrolyte was adjusted to a pH of 6.98 with sulfuric acid. 0.6 ppm of ozone was detected after 180 minutes. The concentration of peracetic acid was measured every 30 minutes for 180 minutes, and a peak of 19.23 ppm was reached at 120 minutes, falling to 7.69 ppm after 150 minutes. EXAMPLE 6 Generation of peracetic acid, hydrogen peroxide and ozone at pressure above atmospheric pressure from sodium acetate The procedures of Example 5 were employed, except as indicated. A 2.5 M solution of sodium acetate was used, adjusted to a pH of 6.66 with sulfuric acid as the electrolyte (a 5M solution could not be prepared due to solubility problems). A potential of + 4.77V was applied versus the reference electrode (applied real voltage 9.5V). The electrolyte pressure in the electrolysis unit was maintained at a level between 2 and 10 p.s.i.g. by introducing air through the septum with a syringe. The concentrations of peracetic acid and hydrogen peroxide were measured at 30 minute intervals for 2 hours. The anolyte reached a maximum peracetic acid concentration of 4.55 after 90 minutes. The concentration of hydrogen peroxide in the anolyte reached 10 ppm and remained stable at 10 ppm after 60 minutes. One ppm of ozone was detected in the anolyte after 120 minutes. EXAMPLE 7 Generation of peracetic acid, hydrogen peroxide, and ozone at a temperature higher than room temperature, in the presence of surfactants and corrosion inhibitors A commercial anti-corrosion and surfactant composition containing phosphate and corrosion inhibitors, commonly employed in sterilization with peracetic acid, was added to a 5M potassium acetate and the pH was adjusted to 6.96 using sulfuric acid. After decanting the precipitate, the solution was added to an electrolysis unit with a platinum anode and a platinum cathode, separated by a NAFION PEM cell membrane. The electrolysis unit was placed in a hot water bath, which kept the temperature inside the electrolysis unit in a range of 30 to 40 ° C. A potential of + 4.46V was applied versus a reference electrode of Ag / AgCl in 3M NaCl. After 30 minutes, the concentrations of peracetic acid and hydrogen peroxide were 2.7 and 5 ppm, respectively. The concentration of hydrogen peroxide rose slightly in the following 1 and a half hour, while the concentration of peracetic acid remained stable. Less than 1 ppm of ozone was detected after 2 hours. EXAMPLE 8 Generation of peracetic acid, hydrogen peroxide, and ozone at low pH, in the presence of surfactants and corrosion inhibitors The procedures of Example 7 were repeated with the following exceptions. The electrolysis unit was cooled with an ice bath and the pH was adjusted to 5.96 with sulfuric acid. An initial potential of + 4.8V was applied versus the reference anode Ag / AgCl in 3M NaCl. (The actual voltage applied was 9.5V). After 30 minutes, the concentration of peracetic acid was 2 ppm, rising to 4 ppm after 2 hours. The concentration of hydrogen peroxide was raised from about 5 ppm to 30 minutes, about 10 ppm after 2 hours. Less than 1 ppm of ozone was detected after 2 hours. EXAMPLE 9 Generation of peracetic acid, hydrogen peroxide, and ozone from 0.5M potassium acetate, in the presence of surfactants and corrosion inhibitors The procedures of Example 7 were followed, except as indicated. A low electrolyte concentration was used. 0.5M potassium acetate was used instead of 5M potassium acetate. The electrolysis unit was cooled in an ice bath to maintain a temperature of 13.5-15 ° C. The pH of the electrolyte solution was adjusted to 6.93 using sulfuric acid. An initial potential of + 4.28V was applied versus an Ag / AgCl reference electrode in 3M NaCl. (The actual applied potential was 9.5V 9. The concentration of peracetic acid remained stable at 1.84 ppm after 30 minutes.The concentration of hydrogen peroxide was 5ppm after 30 minutes and 10ppm after 2 hours.

EXAMPLE 10 Generation of peracetic acid, hydrogen peroxide, and ozone in a flow cell The generation of oxidizing species in a flow system was studied with a platinum anode and platinum cathode in the electrolysis unit. 5M potassium acetate was used as electrolyte with a NAFION PEM filter. The pH was adjusted to 6.71 with sulfuric acid and the anolyte and catholyte were circulated through separate flow paths and returned to the electrolysis unit. Two peristaltic pumps were used to recirculate the electrolyte solutions. A glass heat exchanger in a cooling bath cooled the solutions in the flow paths. The unit was activated for 150 minutes. The concentration of peracetic acid remained constant at 1.71 ppm after 30 minutes. The concentration of hydrogen peroxide reached one ppm after one hour and remained constant at 2 ppm after one and a half hours. 0.6 ppm of ozone was detected at 3 hours.

Claims (2)

1. \ 35 CLAIMS *. A method for microbially decontaminating elements with an oxidizing species, the method comprises the electrochemical generation of an antimicrobial solution containing the oxidizing species, which includes the separation of an anodic chamber (12) and a cathodic chamber (14) from an electrochemical cell ( 10) with a barrier (20) substantially impermeable to the oxidizing species, and the application of a positive potential to an anode (16) in the anode chamber to convert a precursor into an electrolyte adjacent to at least one of the anode and cathode (18). ) in the oxidizing species, the method is characterized by the following: electrochemically generate peracetic acid as at least a significant component of the oxidizing species, the concentration of peracetic acid in the antimicrobial solution is about 10 ppm or more; transporting the antimicrobial solution containing peracetic acid along a fluid flow path to a site (44) wherein the elements must be decontaminated microbially; and contacting the elements with the antimicrobial solution containing the peracetic acid to decontaminate them microbially. The method according to claim 1, further characterized in that the oxidizing species further includes an oxidizing agent selected from the group consisting of ozone, hydrogen peroxide, and combinations thereof. 3. The method according to claim 2, further characterized in that the precursor includes an acetyl donor. 4. The method according to claim 3, further characterized in that the acetyl donor is selected from the group consisting of potassium acetate, sodium acetate, acetic acid, acetaldehyde, and combinations thereof. . The method according to claim 4, further characterized in that the acetyl donor is potassium acetate, at a concentration of about 0.5 to about 5M. . The method of any of the preceding claims 1-5, further characterized in that the electrolyte further includes an additive selected from the group consisting of corrosion inhibitors, surfactants, sequestering agents, and combinations thereof. . The method of any of the preceding claims 1-6, further characterized in that the electrolyte is subjected to a pressure greater than atmospheric pressure.

   8. The method of any of the preceding claims 1-7, further characterized in that the electrolyte temperature is about room temperature or higher than said room temperature. The method of any of the preceding claims 1-8, further characterized in that: the oxidant species used are recirculated from the site to the electrochemical cell for regeneration. The method according to any of the preceding claims 1-9, further characterized in that: the concentration of the oxidizing species is monitored, and the rate at which the oxidant species is regenerated is adjusted. The method of any of the preceding claims 1-10, further characterized in that: the electrolyte is regulated at an approximately neutral pH.
2. 2. A system (A) for antimicrobial decontamination of the device comprising an electrochemical cell (10) including an anode (16) and a cathode (18) separated by a barrier (20) that is substantially impermeable to an oxidizing species, a source of an electrical power (22) connected to at least one of the anode and the cathode, and an electrolyte adjacent to at least one of the anode and cathode, the system is characterized in that it contains: a precursor in the electrolyte that can be converted into acid peracetic in a concentration of approximately 10 ppm or more by applying a potential to at least one of the anode and cathode, the oxidizing species includes peracetic acid; and a fluid flow path (36) that transports the peracetic acid generated from the electrochemical cell to a site (44) wherein the device must be microbially decontaminated by the peracetic acid. . The system according to claim 12 wherein the site (44) in which a device must be microbially decontaminated comprises a container (42) receiving the device, the container being fluidly connected to the fluid flow path.