WO2000078150A1

WO2000078150A1 - Iodine germicides that continuously generate free molecular iodine

Info

Publication number: WO2000078150A1
Application number: PCT/US1999/013989
Authority: WO
Inventors: Yongjun Duan; Jack Kessler
Original assignee: Symbollon Corporation
Priority date: 1999-06-21
Filing date: 1999-06-21
Publication date: 2000-12-28
Also published as: AU4957199A

Abstract

Compositions that continuously generate free molecular iodine include an iodide salt and a persulfate salt. Methods are provided to prepare such compositions and to use such compositions for disinfection.

Description

IODINE GERMICIDES THAT CONTINUOUSLY GENERATE FREE MOLECULAR IODINE

Field of the Invention

This invention generally relates to iodine disinfectants and sterilants, and in

particular, to iodine germicides that continuously generate free molecular iodine.

Background

Many examples of commercial iodine products containing 0.5 to 20% iodine by

weight are known. There are presently only one or two examples of iodine products that

contain 0.1% iodine or less. One reason for this is that almost all commercial iodine

products are concentrates. These iodine concentrates ordinarily call for dilution with water

prior to use. The dilution is usually in the range of 1 : 100 to 1 : 1000. The diluted product is

discarded after use, since the iodine content of the solution continuously decreases over the

course of several hours and the germicidal activity of the solution quickly decreases below

acceptable levels.

There are also iodine products that are not diluted prior to use, such as hand-washing

compositions, bovine teat dip products, and products for human topical disinfection. The

level of total iodine contained in all of these products is much higher than the minimum

iodine concentration required for biocidal efficacy. Despite the fact that these products do

not require high iodine levels for effectiveness, it is necessary to include elevated iodine

levels in order to achieve adequate product stability. However, one drawback of such compositions is that the inclusion of elevated iodine levels contributes to undesirable

toxicological properties and unwanted interactions with inanimate materials.

The prior art contains examples of instantly generating iodine in order to provide a

germicidal activity. U.S. Patent No. 3,232,869 teaches a method for purifying and

disinfecting aqueous liquids with free molecular iodine, where the iodine is provided by

quantitatively oxidizing iodide ion into free molecular iodine with persulfates in the pH

range between 7 and 8. This patent requires the use of a stoichiometric amount of either

iodide or persulfate to yield a free iodine concentration of 0.1 to 1.0 ppm of free molecular

iodine.

U.S. Patent No. 3,215,627 discloses a method for use in the disinfection of

swimming pools. A pH range of 7 to 8 is taught as critical to both U.S. Pat. Nos. 3,232,869

and 3,215,627. The range of free molecular iodine that is generated according to the

method of the '627 patent is between 0.2 and 0.4 ppm. This patent also teaches that an

iodide bank is of no value because iodine release is erratic and unpredictable and because it

is not possible to achieve or maintain a desired iodine level.

United States Patent Nos. 3,215,627 and No.3,232,869 identify a concentration

range of 0.1 to 1.0 ppm of iodide ion as the practical concentration range. This

concentration of iodide equates to a theoretical maximum free molecular iodine

concentration of 0.85 ppm. Moreover, both the '627 and '869 patents teach that a pH in the

range of 7 to 8 is critical. Summary of the Invention

In one aspect, the invention features a method of preparing an iodine-containing

disinfecting solution. The method comprises the steps of providing a persulfate salt;

providing an iodide salt; and combing the persulfate salt and the iodide salt in an aqueous

medium having a pH less than or equal to about 6.5 to generate free molecular iodine at a

rate of at least 0.2 ppm per hour for an extended period of time.

In another aspect, the invention provides a disinfecting composition for generating

free molecular iodine. The composition comprises a persulfate salt; an iodide salt; and an

aqueous medium having a pH less than or equal to about 6.5; the composition being

effective, upon combining the persulfate salt and the iodide salt, in the aqueous medium, to

generate free molecular iodine for an extended period of time at a rate that is at least 0.2

ppm such that iodine is maintained at a desired concentration. The composition can be

packaged such that the iodide salt and the persulfate salt are isolated from each other within

the same container. The contents of the container can be added together in an aqueous

medium, at a pH less than or equal to about 6.5, to initiate the iodine-generating reaction.

Detailed Description of the Invention

For convenience, certain terms employed in the specification, examples, and

appended claims are defined below.

The term "thiosulfate titrable iodine" or "total iodine" is a term of art, and, as used

herein, refers to iodine species which can be titrated by thiosulfate. Total iodine includes

free molecular iodine and triiodide, since they are both titrated by sodium thiosulfate. The term "rate of iodine generation" as used herein, refers to the rate at which free

molecular iodine formed from the oxidation of iodide anion by the peroxydisulfate anion.

The rate of iodine generation is a critical feature of this invention since different

applications contemplated under this disclosure, e.g., instrument disinfectant, disinfection of

dental water lines, disinfection of hemodiazlyzers, hard surface disinfectant, teat sanitizer,

etc., require different rates of iodine generation.

The term "slow oxidant" or "slow oxidizer," as used herein, refers to an agent that

can oxidize iodide anion to molecular iodine over an extended period of time, in contrast to

"fast" oxidants which rapidly and quantitatively oxidize iodide to iodine. For example, the

oxidation of iodide by a slow oxidant such as persulfate can be made to occur over a period

of hours or days.

The term "source of persulfate anion" or "persulfate salt," as used herein, means any

material alone or in combination which can serve as a precursor for persulfate anion.

Persulfates are also known as "peroxydisulfates." Sources of persulfate anion include

sodium persulfate, ammonium persulfate and potassium persulfate.

The term "iodine species ratio," as used herein, refers to the ratio of free molecular

iodine (I2) to other iodine species such as iodide and triiodide.

The term "iodine generation capacity," as used herein, refers to the quantitative

ability of a composition of matter to generate free molecular iodine over its proscribed use-

life for those compositions which require an initial level of free molecular iodine before

they are useful. For example, the iodine generation capacity for a composition which

initially contains only free molecular iodine, and no other iodine species, is 0; that is, this composition does not have the ability to replace the initial concentration of free molecular

iodine once it is consumed from the system. An iodine generation capacity of 1 indicates

that a composition has the ability to replace up to a maximum of one time all of the initial

free molecular iodine. Similarly, an iodine generation capacity of 10 means that a

composition has the ability to replace up to a maximum of ten time all of the initial free

molecular iodine that is consumed.

The iodine generation capacity referred to in this application does not rely upon a

large reserve of triiodide to serve as a source of potential free molecular iodine. In contrast

to traditional iodophores, compositions based upon the present invention rely upon the

continuous generation of free molecular iodine at a predetermined rate. By avoiding the use

of triiodide the compositions of matter contemplated under this invention expect to obviate

many of negative features e.g., staining, irritation, of traditional iodine compositions.

The term "iodide salt" refers to any salt of the iodide anion which yields the iodide

anion when dissolved in an aqueous medium. Suitable counter-ions for the iodide anion

include sodium, potassium, calcium, and the like, as well as ammonium cations.

A "source of initial free molecular iodine" or "initial iodine source," as used herein,

refers to a source of iodine that rapidly generates a selected concentration of molecular

iodine. For example, molecular iodine, when added to a composition, immediately

generates a selected concentration of free molecular iodine in solution. Other sources of

initial iodine include iodophores and combinations of iodide anion with a fast oxidant.

Below a pH of 7.0, iodine atoms assume three principal forms. These three forms

are triiodide, iodide and free molecular iodine; of these three species, only free molecular iodine is biocidal. At a pH of 7.0 and above hypoiodous acid is formed in substantial

concentrations. Hypoiodous acid is biocidal but its biocidal activity is substantially less

than free molecular iodine on a molar basis.

Free molecular iodine is lost from an aqueous medium in several ways. Free

molecular iodine is hydrated by water and, in an aqueous system, undergoes hydrolysis

through a complicated series of reactions that can be summarized in the following two

equations:

I₂ + H₂O = HOI + I- + H⁺ (1)

3HOI = IO₃ + 21- (2)

The hydrolysis products - iodate (IO3-) and iodide (I") - have no significant antibacterial

activity. Elevated or basic pH values speed up iodine hydrolysis by consuming the protons

formed by hydrolysis of elemental iodine. The relative rates of hydrolysis of free molecular

iodine were measured at different pH values and the data are set forth in Example 1 , infra.

The data indicate that when the pH of a solution is equal to or greater than 7, iodine is

hydrolyzed very rapidly. In contrast, iodine is hydrolyzed slowly when the pH is 6 or

lower.

Free molecular iodine also evaporates considerably more rapidly than either iodide

or triiodide, and, in the absence of organic matter and reducing agents, evaporation

constitutes a major source of overall iodine loss in aqueous systems that freely exchange

with the environment. Finally, free molecular iodine reacts with organic matter and is

consumed as a result of this reaction. Therefore, in order to maintain a defined minimum concentration of free molecular

iodine, it is necessary for an effective iodine-containing germicidal solution to continuously

generate or regenerate the free molecular iodine that is lost through the pathways described

above. The subject invention is based, at least in part, on the observation that persulfates

slowly oxidize iodide anions into free molecular iodine in an aqueous medium under the

appropriate conditions; the rate of this oxidation reaction can be controlled and is

reproducible. The continuous slow oxidation of iodide to iodine provides a source of

biocidal iodine which effectively maintains germicidal activity over an extended period of

time without requiring large reserves of triiodide such as those commonly found in

iodophores.

Accordingly, in one aspect, the invention provides a disinfecting composition for

generating free molecular iodine. The composition comprises a persulfate salt; an iodide

salt; and an aqueous medium having a pH less than or equal to about 6.5. The composition

is effective, upon combining the persulfate salt and the iodide salt, in the aqueous medium,

to generate free molecular iodine for an extended period of time. In certain embodiments,

the composition further includes an initial source of iodine. Preferably, when an initial

concentration of free molecular iodine is required, the concentration of the initial free

molecular iodine is at least about 5 ppm although 10 ppm may be preferred for certain

applications.

The iodine compositions contemplated under this invention have an iodine

generation capacity between 1.5 and 36. The iodine generation capacity and the rate of

iodine generation provide some indication as to the minimum and maximum concentration of iodine that could be generated. It can be readily appreciated that the most suitable rate of

iodine generation and iodine generation capacity will depend upon both the specific

application and the local environment wherein the specific application is performed. For

instance, one liter of a disinfectant that is contained in an unsealed glass jar that has a

surface to volume ratio of 1000 will allow for more evaporation of free molecular iodine

than would be observed with one liter of the identical disinfectant in a sealed glass container

that had a surface to volume ratio of 100. Therefore it is impossible to preselect the most

suitable ratio of iodide/persulfate unless one knows exactly how the composition will be

used and the exact conditions of use.

In one embodiment the iodide salt and the persulfate salt may be provided in the

same package as long as they are isolated from one another and maintained in a non-

reactive condition. Various additives, including buffers, surfactants, detergents, dyes,

perfumes, humectants, emollients, iodine sequestrants, anti-foaming agents, and anti-

corrosive agents, may also be included within the pre-packaged container. Optionally, an

initial source of free molecular iodine can be in the form of either free molecular iodine,

triiodide or another iodine precursor. An initial free molecular iodine source is sometimes

useful where immediate iodine-derived germicidal activity is desired since it normally

requires more than 5 minutes at room temperature for the reaction between the iodide and

persulfate salts to generate germicidal- levels of free molecular iodine.

The formulations contemplated under this invention can be incorporated into a kit to

facilitate use. The iodide and persulfate components of the kit should be packaged so as to

preclude any oxidation of the iodide anion prior to the products intended use. The kit would preferably be configured so that the end-user could easily combine the contents of the kit

into an aqueous medium for activation. The contents of the package should be able to be

conveniently transported and/or stored until ready for use. To initiate the iodine-generating

reaction, the contents of the package are emptied into an aqueous medium having a pH of

less than or equal to 6.5.

The iodine-containing disinfectants of the invention provide several advantages.

The subject disinfectant solutions utilize minimal concentrations of free and/or total iodine

to achieve a desired efficacy, thereby minimizing the potential for unwanted toxicological

reactions and objectionable reactions with inanimate materials. Another advantage is that

the subject solutions can be reused without adding additional components and without the

loss of germicidal activity.

Compositions

The present invention contemplates iodine compositions that: (1) contain between 5

and 10,000 ppm of thiosulfate titrable iodine; (2) have between 5 and 325 ppm free

molecular iodine; (3) increase or substantially maintain the ratio of free molecular iodine to

total iodine over a period of time, even under conditions that cause the loss of iodine atoms;

and (4) have an iodine generation capacity between 1.5 and 36.

In general, germicidal compositions according to the invention will include iodide

anion at concentrations between 50 and 10,000 ppm and most preferably between 100 and

500 ppm. The source of iodide anion can be any iodide salt which yields the iodide anion

when dissolved in an aqueous medium. Examples of such salts include the sodium,

potassium, calcium and ammonium salts, and mixtures thereof. The most preferred iodide

salts include sodium iodide and potassium iodide. The iodide salt can be dissolved all at one time, or it can be dissolved gradually over time, as when a slow-release formulation is

used. Iodide anion can be provided to the system in a liquid form if it is kept stable prior to

use. Specifically, it is preferred that no contact occur between the iodide anion and the

peroxydisulfate anion prior to dissolution in an aqueous environment.

The concentration of iodide that will yield a suitable level of iodine varies with the

pH of the contemplated formulation. However, the useful range is between 0.05 and 10.0

grams per liter in the final reconstituted formulation. The preferred range for iodide anions

is between 0.1 and 4.0 grams per liter in the final reconstituted formulation. Such

concentrations of iodide anion, in combination with an appropriate amount of persulfate salt

and at a suitable pH, are anticipated to yield a concentration of free molecular iodine in the

range of 5 to 325 ppm, and more preferably a free molecular iodine concentration in the

range of 10 to 150 ppm.

Germicidal compositions of the invention also include a slow oxidant, e.g., an

oxidant which is capable of slowly oxidizing iodide anion to molecular iodine in a

controlled and predictable fashion. A preferred slow oxidant is persulfate, e.g., a persulfate

salt. As described in more detail below, the slow oxidant should be capable of oxidizing

iodide to iodine over a period of hours or days. The persulfate salt can be any material

which yields persulfate anion upon dissolution in an aqueous medium. Preferred persulfate

salts include sodium persulfate, ammonium persulfate, potassium persulfate, and mixtures

thereof. A combination of reactants which generate persulfate anion in situ can also be

employed, provided that the reaction conditions are such that iodide is slowly oxidized to

iodine. The preferred concentration range for persulfate anion in the final composition is

between 0.01 and 1% (w/w) in the final composition, more preferably between 0.04 and

0.2% (w/w) in the final composition. As with the iodide salts, persulfate salts can be

dissolved all at one time, or can be dissolved gradually over time, as when a slow-release

formulation is used. In several preferred embodiments, the persulfate salt is present in sub-

stoichiometric quantities compared to the iodide salt, i.e., it is present in sub-molar

quantities.

The stoichiometric ratio of iodide anion to persulfate anion is generally between 2:1

and 0.2: 1. In certain preferred embodiments, the ratio of iodide anion to persulfate anion is

at least 1:1. Thus, in preferred embodiments, an iodide "bank" or reserve can be

maintained, such that excess iodide ion is present. In other preferred embodiments, the ratio

of iodide anion to persulfate anion is less than about 1:1, more preferably about 0.7:1.

Buffering agents may be utilized to maintain pH within the desired range of 1.0 and

6.5, or within the more preferred range of 3.5 and 5.5. Suitable buffering agents for

inclusion in the compositions of the invention include glycine-glycine-HCl, potassium

hydrogen phthalate-phthalic acid, citric acid-Na₂HPO , citric acid-KH₂PO₄-H₃BO₃-

diethy -barbituric acid-NaOH, citric acid-sodium citrate, dimethylglutaric acid-sodium

dimethylglutarate, acetic acid-sodium acetate, succinic acid-sodium succinate, potassium

hydrogen phthalate-dipotassium phthalate, sodium cacodylate-cacodylic acid, sodium

hydrogen maleate-disodium maleate, Na₂HPO₄-NaH₂PO , sodium bicarbonate-5% CO₂,

imidazole-imidazole-HCl, boric acid-sodium borate, and the following buffers known to one

skilled in the art: Tris, MES, BIS-TRIS, ADA, ACES and PIPES. Enough buffer is added to maintain the pH below 6.5 or, if preferred, within a defined pH limit that is less than pH

6.5. In general, a buffer concentration of at least 5 millimolar is utilized.

Aqueous mediums suitable for use in the present invention include water, mixtures

of water and alcohols (such as methanol, ethanol, and isopropanol), or mixtures of water

and other water-miscible solvents. In general, an aqueous medium will be capable of

dissolving iodide salts and persulfate salts, and will not react rapidly with free molecular

iodine. In preferred embodiments, the aqueous medium is substantially non-toxic. In

preferred embodiments, the aqueous medium is at least 50% water by volume.

Compositions contemplated by the invention can also include surfactants and/or

detergents. Suitable detergents and surfactants include anionic, cationic, zwitterionic, non¬

ionic and ampholytic agents. These molecules are frequently used in formulations used for

cleaning inanimate and animate surfaces. Representative compounds include sodium lauryl

sulfate, lithium lauryl sulfate, alkyl benzenesulfonates, alkane sulfonates, alkene sulfonates,

sulfated anionic detergents, sulfated anionic detergents, sulfonated anionic detergents,

phosphated anionic detergents, carboxylated anionic detergents, Tween 20-polyoxyethylene

sorbitan monolaurate, Tween 100, alkyl sulphates, alkyl ether sulphates, fatty acid amides,

myristic acid, lauric acid, capric acid, caprylic acid, coconut and palm kernel fatty acids, N-

acyl-sarcosinates, sodium-N-acyl-N-methyl taurates, sodium cocoylisothioate and

amidopropyl betaines. The selection and concentration of these diverse surface active

agents depends upon the application as one skilled in the art appreciates.

Some of the organic detergents listed above also have the ability to bind iodine and

can thus potentially serve as sequestrants. For example, certain polyoxyethylene ethers that are commonly called Tritons can act as iodine sequestrants. The use of a detergent or

surfactant that can also function as a sequestrant is contemplated in certain embodiments of

the invention.

Other additives which may be employed in the compositions of the invention

include dyes, perfumes, humectants, emollients, iodine sequestrants, anti-foaming agents,

and anti-corrosive agents.

Representative humectants and emollients suitable for inclusion in the compositions

contemplated in this application include sorbitol, dulcitol, glycerol, propylene glycol,

acetamidopropyl trimonium chloride, lactamidopropyl trimonium chloride, acetamide

MEA, lactamide MEA, lanolin, ethoxylated lanolins, polyethylene glycol-lanolin

derivatives that contain lanolin dispersed onto polyethylene glycol, sorbitan isostearate,

cetearyl octanoate, maleated soybean oil, cetyl lactate, lauryl lactate, dioctyl malate,

myristyl lactate, tridecyl neopentanoate, glyceryl dilaurate, condensation products of

primary and secondary alcohols, block polymers of ethylene oxide and propylene oxide and

polyethylene glycol and polyethylene glycol derivatives.

Iodine sequestrants or complexing agents are well known in the art and examples

can be found in various patents, including U.S. Pat. Nos. 2,931,777; 2,759,869; and

3,028,300. Examples of iodine complexing agents include nonionic poly(ethylene oxide)

homopolymers such as POLYOX N-10 and POLYOX N-12K, where POLYOX is a trade

name of Union Carbide; block copolymers of ethylene oxide and propylene oxide such as

PLURONIC F-38, PLURONIC F68, PLURONIC F 87 PRILL, PLURONIC F108 PRILL,

PLURONIC 25 R4, PLURONIC P-105 where PLURONIC is a trade name of BASF Wyandotte; tetra-functional block copolymers derived from the sequential addition of

propylene oxide and ethylene oxide to ethylenediamine such as TETRONIC 304 and

TETRONIC 908 PRILL where TETRONIC is a trade name of BASF Wyandotte; polymers

comprised of N, N-dimethyl-1-hexadeanamine oxide dihydrate such as ADMOX 14-85,

ADMOX SC-1685 and ADMOX 18-85 where ADMOX is a trade name of Ethyl

Corporation; polyvinylpyrrolidone; alkylphenol ethoxylates such as octyl-, nonyl- or

dinonyl- phenoxypolyethoxy ethanol, and polymers comprised of ethoxylated alcohols that

range from 8 to 18 carbon atoms in length such as NEODOL(R) 1-9 and NEODOL (R) 25-9

where NEODOL is a trade name of Shell Chemical Corporation. One skilled in the art will

be able to identify other types of surfactants that can bind iodine.

In another practice of the invention, a slow oxidant (e.g., a persulfate salt) can be

added to a commercially available iodine germicide. The resulting composition can

continuously generate iodine over an extended time. For example, addition of a persulfate

salt to an iodine germicide such as WESCODYNE results in an iodine germicide that

continuously generates free molecular iodine, as described in Example 6, infra. In this

embodiment, the commercially available iodine germicide (e.g., Wescodyne) provides an

initial source of free molecular iodine and can also provide or contribute to an iodide bank.

The compositions of the invention continuously generate free molecular iodine via

the slow oxidation of iodide anion by persulfate anion. The concentration range of free

molecular iodine contemplated in the invention is about 5 to about 325 ppm with a preferred

range of about 10 to about 150 ppm. A minimum concentration of 10 ppm can be preferred

because this level of free molecular iodine can be shown to have a significant and rapid effect on highly concentrated suspensions of bacteria (see Example 7). In some

embodiments, a higher concentration of iodine is desirable. For example, the disinfection of

endoscopes generally requires iodine concentrations of about 30 to 50 ppm to provide a

margin of safety during use. In general, the concentration of free molecular iodine can be

adjusted by adjusting the concentration of persulfate anion or iodide anion. Thus, increased

concentrations of persulfate salt (and/or iodide anion) are expected to result in higher

concentrations of free molecular iodine.

The rate of generation of free molecular iodine is mainly determined by the

concentration of iodide anion and persulfate anion. It is critical to the practice of this

invention to be able to control the rate of iodine generation since different applications will

function optimally at different rates. It is possible to increase the rate of iodine generation

by increasing either the iodide concentration or the persulfate concentration. At a constant

concentration of iodide the rate of iodine generation will be increased by increasing the

concentration of persulfate. At a constant concentration of persulfate the rate of iodine

concentration will be increased by increasing the concentration of iodide.

The duration during which free molecular iodine is generated is determined by the

concentration of iodide anion, the pH, the temperature and the concentration of persulfate

anion. The invention contemplates compositions that continuously generate free molecular

iodine for a minimum of 1 hour and a maximum of 20 days without requiring the addition

of fresh reagents or time released chemicals. It is obvious to one skilled in the art that it

would be possible to increase the time period over for generation of iodine by incorporating

either iodide or persulfate into a time-release format. The compositions of the invention gradually produce free molecular iodine in a

controlled fashion over time, and, in the absence of initial added iodine, have low

concentrations of free molecular iodine when initially constituted. In certain embodiments,

it may be desirable to include additives which provide a suitable initial concentration of free

molecular iodine. For example, iodine can be added to provide free molecular iodine; the

concentration of free molecular iodine will subsequently be maintained by the oxidation of

iodide to iodine. In another illustrative embodiment, a peroxidase and a source of peroxide

can be used to rapidly generate initial iodine, as described in Example 8. In yet another

embodiment, a small amount of persulfate can be activated by a promoter, e.g., a metal. For

example, addition of a small amount (e.g., 5 mole %) of copper can activate a small amount

of persulfate (e.g., 5 mole %). The "activated" persulfate rapidly oxidizes iodide anion to

molecular iodine; the copper and "activated" persulfate are consumed. The slow oxidation

of iodide by persulfate then continuously generates free molecular iodine over an extended

period.

The term "regenerability" is employed in this application to express the rate at which

free molecular iodine is generated and the duration of time over which free molecular iodine

is generated. Different regenerabilities are required in different applications to offset the

iodine loss that occurs during an application. For example, a high regenerability has to be

provided in a case where iodine evaporates very quickly and a long application time is

required. Many factors have an effect on the regenerability of a composition including the

concentration of iodide and persulfate ions, pH value, temperature and additives. Therefore,

routine experimentation may be necessary to find to a suitable regenerability for a specific application. Once a suitable regenerability has been identified for an application the iodide

or persulfate concentrations can be adjusted to meet the requirements, as will be apparent to

the skilled artisan.

For example, disinfection of endoscopes in a 10 minute time period generally

requires a concentration of free molecular iodine of at least 20 and it is preferred to limit the

concentration to less than 75 ppm compared to the disinfection of skin, which can require

up to 150 ppm of free molecular. Thus, the concentrations of iodide anion and persulfate

salt in a composition of the invention are preferably selected to result in a free molecular

iodine concentration suitable for use in a particular application.

One advantage of the germicidal compositions of the invention is that the

compositions retain germicidal activity over an extended period of time, e.g., for as long as

two weeks. Thus, the germicidal compositions of the invention can be used repeatedly,

rather than being discarded after a single use or a short period of use, as is the case with

many prior art germicides. Accordingly, the present invention provides compositions which

are economical and time-saving.

It should be noted that it is not essential to the successful practice of this invention

that the iodine level in a reconstituted formulation remain the same during the time that it is

intended for use. Rather, it is important that any change in iodine concentration be within

the limits of variation that will not affect a desired performance level for the particular type

product. Microbicidal iodine compositions of the present invention preferably have a pH

equal to or less than 6.5. The more preferred pH range is between 3.5 and 5.5. Products contemplated under this application will generally be stored or packaged in

an unreacted state prior to use. An unreacted state is one in which conditions exist which

prevent iodide oxidation by persulfate ion or other oxidants.

The compositions of the invention can be reconstituted in an aqueous environment

some period of time prior to their intended use and an initial reaction then generates a

defined level of free molecular iodine. One method of packaging is to compartmentalize a

salt of persulfate in one chamber of a package and to include iodide anions in another,

separate chamber of the package. Additional components can be placed in separate

compartments if they prove to be incompatible. It is possible to include liquid components

within the package provided that the liquid components are maintained in a state that

precludes the oxidation of iodide anion prior to use. In preferred embodiments, a source of

persulfate anion is stored in a non-aqueous, water-free environment.

Compositions according to the invention are useful as sanitizers, disinfectants, high

level disinfectants or sterilants. In preferred embodiments, the compositions are capable of

passing specific regulatory tests required by both the United States Environmental

Protection Agency (EPA) and the United States Federal Drug Agency (FDA). This is a

very important aspect of this invention since it enables low concentration iodine-based

compositions to successfully traverse the gamut of efficacy tests required by United States

and European regulatory provisions. These key efficacy tests include the hard surface

carrier test for bacteria, mycobactericidal activity and, most surprisingly, the Association of

Official Analytical Chemists (AOAC) sporicidal activity tests against vacuum dried spores.

The AOAC sporicidal assay is described in Example 4. Thus, a "disinfectant" is a chemical agent that eliminates a defined scope of

pathogenic organisms, but not necessarily all microbial forms (e.g., not bacterial

endospores). A "high-level disinfectant" is a germicide that kills all microbial pathogens,

except large numbers of bacterial endospores, when used according to labeling. A

"sterilant" is a chemical germicide that achieves sterilization, i.e., can destroy all microbial

pathogens, including endospores.

The present invention provides compositions which are useful in a broad range of

formulations according to the requirements for a particular application. Germicidal

formulations of the invention can have various ratios of free molecular iodine and other

iodine species such as iodide and triiodide (hereinafter called the "iodine species ratio ").

The iodine species ratio can be made to meet the needs of different applications.

Generally, a specific iodine species ratio is required for a certain application. For

example, a useful ratio for the disinfection of endoscopes is approximately 1/1.

Uses of Compositions of the Invention

In preferred embodiments, the concentrations of the iodide source, the oxidant, and

any additives, are selected such that the resulting composition is substantially non-toxic to

mammals, and preferably are substantially non-toxic to humans. Accordingly, the non-toxic

compositions of the invention can be used either in vitro or in vivo without undesirable

toxicity. Thus, in a preferred embodiment, the germicidal composition of the invention can

be formulated for external or internal usage in a human. Another use of such a non-toxic

composition is as a bowel disinfectant for use prior to surgical procedures. Examples of

external uses for the compositions of the invention include hand dips or swabs for disinfection of skin. Similarly, many veterinary applications are possible, including bovine

teat dips and the like.

Compositions according to the invention can be used to disinfect hospital and

medical equipment, including, for example, endoscopes, scalpels, dental and surgical

equipment, dental water lines, bedpans, hemodialysis equipment, heart-lung machines, and

the like. The compositions of the invention can also be used to disinfect veterinary

equipment and dip poultry eggs. Furthermore, compositions according to the invention can

be employed in industrial applications such as the disinfection of bathrooms, and the like.

Many other uses will be apparent to the skilled artisan.

Kits

In another aspect, the invention provides a disinfecting kit for generating free

molecular iodine. In preferred embodiments, a kit includes a sealable container, a supply of

a slow-acting oxidizer composition disposed within the container in a non-reactive

condition, and a supply of iodide salt disposed within the container but isolated from the

supply of the slow-acting oxidizer. In preferred embodiments, the slow-acting oxidizer is in

a non-aqueous state. The slow-acting oxidizer is the persulfate anion.

Kits of the invention can be used to conveniently supply a germicidal composition

of the invention. For example, a kit can contain premeasured amounts of an iodide salt, a

persulfate salt, and any additives desired. The kit can further include instructions for the

reconstitution of the composition of the invention and directions for use of the composition

for disinfection. Examples:

Example 1

To quantitatively understand the effect of pH on iodine hydrolysis, molecular iodine

was added into buffered solutions at different pH values and the free molecular iodine

concentrations in these solutions were measured at different times. All free molecular

iodine values cited in this example and the other examples contained in this patent were

determined according to the potentiometric method (W. Gottardi,1983, Fresenius Z. Anal.

Chem. 314:582-585). The advantage of the potentiometric method is that the concentration

of free molecular iodine is determined directly in solution without subsequent

manipulations, such as extraction or equilibrium dialysis. This provides a much more

accurate measurement.

Table 1 presents the rate of iodine hydrolysis expressed as per cent of free molecular

iodine lost. The zero time, value of free molecular iodine is considered to equal 100%.

When the pH of a solution was over 7, iodine was hydrolyzed very rapidly. However, iodine

hydro lyzes slowly when the pH is 6 or lower. Under the best of circumstances the effect of

a rapid rate of hydrolysis is to require more iodide and persulfate which adds to cost and

makes the product more bulky. In most cases a rapid rate of hydrolysis eliminates the

possibility for an effective product.

Example 2

The rate of iodine generation that was produced by a combination of sodium

persulfate and iodide anions was measured in solutions of different pH. The concentration

of free molecular iodine was measured at different pH values as function of time using the

potentiometric iodine method of Gottardi. The results of these measurements are presented

in Table 2.

A 1.32 molar ratio of sodium iodide (1.0 g/1) over sodium persulfate (1.2 g/1) was

used in the experimental formula. The results indicate that free molecular iodine generation

is much lower in the solutions at pH values that are greater than 8, while pH has little effect

on free molecular iodine when pH is lower than 7. This experiment, together with the

results shown in Example 1, show that the most practical pH range for compositions of the

invention is pH 3.5 to pH 6.5.

Example 3

A formulation was prepared that started without an initial iodine source. The term

"initial iodine" here, as well as the following examples, includes all titrable iodine which is

not generated by persulfates. Initial iodine is that thiosulfate titratable iodine either added

into system at the beginning or quickly generated by other methods. To a pH 4.5 buffer

solution at room temperature, sodium iodide was added to a concentration of 1000 ppm, and then sodium persulfate was dissolved into the system in an amount to make a concentration

of 0.1 % (w/v). Any buffer with pH at 4.5 can be used, but a buffer system composed of 20

millimolar citric acid and a base such as sodium citrate and sodium carbonate was used for

this example. Loss of iodine from evaporation was prevented by sealing the container. The

free molecular iodine in the system gradually increased from zero at the initial time point to

over 300 ppm over a period of two days.

Example 4

A formulation was developed using the persulfate-iodine generating system that was

suitable for sporocidal assay under AOAC (Association of Official Analytical Chemists)

methods. To make a claim as a sterilant or a sporocide with the Federal Drug

Administration, a germicide product in the United States must pass the Association of

Official Analytical Chemists sporocidal activity test (AOAC sporocidal assay).

To a pH 4.5 solution buffered with sodium citrate and containing 100 ppm initial

titrable iodine with 65 ppm as free molecular iodine, sodium persulfate was added to a

concentration of 0.07%. The initial iodine can be achieved either by an addition of iodine

crystals or by generation with other chemical methods. After addition of sodium persulfate,

the disinfection solution was tested according to the AOAC sporocidal method and the

composition killed all of the vacuum dried Bacillus subtilis spores that were coated on 60

porcelain penicylinders in 18 hours at 30 °C. The identical experiment was repeated using

Bacillus subtilis spores coated onto Dacron sutures at 20 °C. No failures were found when

testing this solution against Bacillus subtilis spores coated on 5 Dacron sutures in 5 days at

20°C. Example 5

A formulation was prepared that was suitable for endoscope disinfection. A volume

of 23 liters of disinfection solution for endoscopes was made with the following

components: 60 g citric acid, 78 g sodium citrate, 7 g sodium iodide, 115 mg horseradish

peroxidase, 500 mg urea hydrogen peroxide and 14 g sodium persulfate. After mixing the

components for 15 minutes, an endoscope was disinfected using a System 83 Plus

endoscope cleaning machine made by Custom Ultrasonics (Buckingham, Pennsylvania) at

room temperature. A disinfection cycle included 40 minutes of disinfection and 5 minutes

of rinse.

The formulation used in this example was reused 8 different times over the course of

8 hours. The concentration of total iodine in this formulation was measured after each

disinfection cycle and it maintained a nearly constant titrable iodine level of 50 ppm. The

free molecular iodine was also measured after each disinfection cycle. The concentration of

free molecular iodine gradually increased from 20 ppm to 30 ppm. The level of evaporation

in the System 83 Plus endoscope cleaning machine is substantial because the instrument is

open to the environment and provides for a significant degree of agitation and movement of

liquids both of which accelerate evaporation.

Example 6

A composition was composed to improve the efficacy of WESCODYNE.

WESCODYNE is a commonly used iodophor distributed by Amsco Corporation (Erie,

Pennsylvania). WESCODYNE was diluted 50 fold with water. To the diluted solution,

sodium persulfate was added in an amount to provide a concentration of 0.1% (w/v). The free molecular iodine increased over a period time of 30 hours. The free molecular iodine

increased by 18% over a period of 8 hours and 45% over 24 hours. Without the addition of

sodium persulfate the level of free molecular iodine decreased at all time points measured.

Example 7

An experiment was performed to determine the lower level of free molecular

iodine that would provide a substantial inactivation of bacteria when the bacteria were

present at an elevated concentration.

Table 7 shows the reduction in the number of Mycoplasma hominis colony forming

units (cfu) after exposure of the organism to various levels of free molecular iodine in a

buffer. The exposed organism was diluted serially (10 fold increments) to enumerate the

number of surviving organisms which retain the ability to form colonies on solid agar.

Table 7 shows a 10 ppm concentration of free molecular iodine imparts a substantial

reduction in the number of viable organisms while lower concentrations are substantially

less effective.

1/tntc = too numerous to count

Example 8

An experiment was conducted to demonstrate that it is possible to oxidize a reserve

or bank of iodide to form iodine in a controlled gradual fashion. This controlled gradual

oxidation of iodide allows one to maintain a constant level of thiosulfate titratable iodine

even in the presence of evaporation. In order to ensure the practical applicability of this

formulation experiments were conducted to demonstrate the suitability of this composition

to disinfect endoscopes in a Custom Ultrasonics System 83 automated endoscope

disinfection instrument. The experiment was conducted at 30°C and an endoscope was

disinfected 15 times during the course of this experiment. At defined time points the

concentration of thiosulfate titratable iodine and iodide was measured. Iodide was

measured using an ion sensitive electrode (Orion Corporation, Cambridge, MA).

Five gallons of the iodine germicide was added to the Custom Ultrasonic 83. Each

liter of the germicide comprised the following materials: 4.85 grams of citric acid; 2.14 grams

of sodium carbonate; 15 milligrams of sodium percarbonate, 500 milligrams of sodium

persulfate; 200 milligrams of sodium iodide; and 5 milligrams of horseradish peroxidase. The

solution was stirred until it was dissolved, then brought to a temperature of 30°C and then

allowed to incubate for 20 minutes. Measurement were made after the 20 minute incubation (i

e., t=0). The measurements of total iodine and iodide are shown below in Table 8.

Those skilled in the art will recognize, or be able to ascertain using no more than

routine experimentation, numerous equivalents to the specific procedures described herein.

Such equivalents are considered to be within the scope of this invention and are covered by

the claims.

Example 9

A composition was dissolved in one liter of water at room temperature and held in

a glass jar that was sealed at its top with a screw-top lid. Buffering agents were added to

control the pH at 4.5; namely 0.79 grams of sodium carbonate and 19.2 grams of citric

acid. A small amount of hydrogen peroxide in the form of sodium percarbonate (0.016

grams) and 1 milligram of peroxidase (Enzyme Commission number 1.11.1.7) were added to provide an initial level of free molecular iodine. Sodium iodide at a concentration of

200 ppm and sodium persulfate at a concentration of 500 ppm were added to provide

generation of free molecular iodine for an extended period of time.

This experiment was conducted to demonstrate that it is possible to oxidize a

reserve or bank of iodide to form iodine over an extended period of time. The experiment

was conducted at room temperature (i.e., 20 to 25°C) and a composition was formulated to

provide continuous oxidation of iodide for at least 13 days. At defined time points the

concentration of thiosulfate titratable iodine was measured. Table 9 above shows the

concentration of total iodine as a function of time. Example 10

or bank of iodide in a controlled gradual fashion and that both (a) the concentration of

iodide and persulfate and (b) the ratio of iodide to persulfate effects the rate of oxidation of

iodide to free molecular iodine. A series of compositions that had differing concentrations and ratios of iodide and sodium persulfate were formulated. The concentration of total

iodine was measured at different time points during the first seven hours of the reactions

and the rate of iodine generation in parts per million (ppm) was determined.

The experiment was conducted at room temperature (i.e., 20 to 25°C) using

distilled water that was buffered with citric acid/carbonate at a concentration of 0.010

molar. Each of the persulfate/iodide compositions were dissolved in one liter of buffered

water and held in a glass jar that was sealed at its top with a screw-top lid. Table 10 below

shows the rate at which iodine is generated as a function of the concentration of iodide and

the ratio of persulfate/iodide.

The data shows that within each of the formulation series that have a constant

iodide to persulfate ratio, the rate of iodine generation increases as the concentration of

sodium iodide is increased. At a fixed concentration of iodide, the rate of iodine

generation increases as the ratio of persulfate/iodide is increased. The principal means to

control the rate of oxidation of iodide anion by the peroxydisulfate anion is the vary the

concentration of either or both of these species. It is clear that it is possible to control the

rate of iodine generation across a broad range by varying either or both of these species. Example 11

A series of compositions that had differing concentrations and ratios of iodide and sodium persulfate were formulated. Each of the persulfate/iodide compositions were dissolved in one liter of water buffered to a pH of 5.0 with 50 mM sodium citrate. The activated formulations were held in a glass jar that was sealed at its top with a screw-top lid at room temperature. The formulations contained various concentrations of persulfate anion and iodide anion such that both (a) the concentration of iodide and persulfate and (b) the ratio of iodide to persulfate were varied to the concentration extremes identified in this application. The concentration of total iodine was measured at different time points during the course of this reaction.

Table 11 below identifies the concentration of iodide and persulfate and the time

required to oxidize 10% of the initial iodine anion which is idnetified as the T_I0 value in

the table. Experiment 3 and 4 identify conditions wherein a high concentration of iodine is

rapidly formed. Experiment 1 identifies conditions wherein it takes more than 24 hours to

achieve a 5 ppm iodine concentration. This type of formulation is useful for situations

where it is necessary to disinfect and preserve sensitive materials over the course of several

days such as disinfecting dialysis instrumentation over a weekend. It is clear from Table

11 that the generation of iodine is a function of both the persulfate anion and iodide anion.

Table 1 la below shows the total iodine concentration versus time for the identical

four compositions used in the experiment described in Table 11. The data in Table 11 a

shows the total iodine concentration as a function of time for a period of seventy hours.

The data is Table 11a demonstrate that a wide range of compositions with diverse

properties can be generated using the conditions described in this application. For

instance, Experiment 1 shows that it is possible to provide a sustained low level of iodine

generation for a prolonged time period. Experiment 4 demonstrates that iodine can be

generated at such a rapid rate that iodine precipitation can occur. This underscores the fact

that a preferred composition of matter can only be formulated once the conditions of use

are fully understood. For instance, if the formulation used in Experiment 4 was placed

under conditions such that 75 ppm per minute of free molecular iodine were evaporating,

then precipitaiton would not occur in the time frame of this experiment.

The contents of all references and patent applications described herein are hereby

incorporated by reference. Other embodiments are within the scope of the following claims.

Claims

What is claimed is:

1) A method of preparing a disinfecting iodine solution in which free molecular

iodine is generated at a controlled average rate of at least 0.2 ppm per hour over a

sustained time period comprising the steps of:

combining a persulfate anion and an iodide anion in sufficient quantity in

an aqueous medium having a resulting pH of less than about 6.5 to provide an iodine

generating capacity of between 1.5 and 36 such that a concentration of at least 5 ppm is

generated and sustained over the course of said time period.

2) The method of claim 1 wherein the minimum concentration of said persulfate anion

is 100 ppm and wherein the minimum concentration of said iodide anion is 50 ppm

and wherein the minimum ratio of said iodide anion to said persulfate anion is 1/2.

3) The method of claim 2 wherein the minimum ratio of said iodide anion to said

persulfate anion is 1/2 such that a concentration of 5 ppm of free molecular iodine is

generated in said solution and sustained in said solution for a defined time period.

4) The method of claim 3 wherein the persulfate anion is generated from a persulfate

salt selected from the group consisting of sodium persulfate, ammonium persulfate and

potassium persulfate. 5) The method of claim 4 wherein the iodide anion if generated from an iodide salt

selected from the group consisting of potassium iodide and sodium iodide or other

simple salts of iodide.

6) The method of claim 5 wherein said sustained time period is equal to at least 1 hour

and up to a maximum of 30 days.

7) The method of claim 1 further comprising the step of adding a source of iodine

independent of said iodide anion to said aqueous medium to establish an initial iodine

concentration of at least 10 ppm.

8) The method of claim 7 wherein said iodine source is selected from the group

consisting of elemental iodine, iodophor and a mixture thereof.

9) A disinfecting iodine composition with a sustained release of free molecular iodine

for an extended time period such that a minimum concentration of 5 ppm of is

achieved when added to an aqueous medium comprising:

a persulfate anion in a minimum concentration of 100 ppm and

an iodide anion in a minimum concentration of 50 ppm with said aqueous

medium having a resulting pH of less than about 6.5.

10) A disinfecting iodine composition as claimed in claim 9 wherein the ratio of said

iodide anion to said persulfate anion is from 1/200 to 100/1 for controlling the iodine

generating capacity and rate of generating free molecular iodine is said aqueous

medium. 11) A disinfecting iodine composition as claimed in claim 10 wherein said persulfate

anion is selected from the group consisting of sodium persulfate, ammonium

persulfate, potassium persulfate and other simples salts of persulfate known to be

converted into peroxydisulfate anion in solution.

12) A disinfecting iodine composition as claimed in claim 11 wherein said iodide salt

is selected from the group consisting of sodium iodide, potassium iodide and other

simple salts of iodide known to be converted into iodide anion in solution.

13) A disinfecting iodine composition as claimed in claim 9 wherein said extended

time period is equal to at least one hour and up to a maximum of 30 days.

14) A disinfecting iodine composition as claimed in claim 13 further comprising a

source of iodine independent of said iodide anion for establishing an initial iodine

concentration in said iodine composition.

15) A disinfecting iodine composition as claimed in claim 14 wherein said iodine

source is selected from the group consisting of elemental iodine, iodophore, a quick

oxidant and a mixture thereof.

16) A kit for converting an aqueous medium into a disinfecting iodine solution in

which free molecular iodine is generated at a minimum rate of 0.2 ppm per hour

comprising:

a container for said aqueous medium;

a persulfate salt; and an iodide salt; with said persulfate salt and said iodide salt being present in

sufficient quantity such that when combined in said aqueous medium the

concentration of free molecular iodine generated reaches a level of at least 5 ppm

over an extended time period and the pH of said resulting disinfecting iodine

solution is below about 6.5.

17) A kit as defined in claim 16 wherein the minimum concentration of said persulfate

anion is 100 ppm and wherein the minimum concentration of said iodide anion is 50

ppm or wherein the minimum ratio of said iodide anion to said persulfate anion is

1/200.

18) A kit as defined in claim 17 wherein the ratio of said iodide anion to said persulfate

anion is from 1/200 to 100/1 for controlling the iodine generating capacity and rate of

generating free molecular iodine in said aqueous medium.

19) A kit as defined in claim 18 wherein said persulfate anion is generated from a

persulfate salt which is selected from the group consisting of sodium persulfate,

ammonium persulfate, potassium persulfate and other simples salts of persulfate

known to be converted into peroxydisulfate anion in solution.

20) A kit as defined in claim 19 wherein said iodide anion is generated from an iodide

salt that is selected from the group consisting of sodium iodide, potassium iodide and

other simple salts of iodide known to be converted into iodide anion in solution 21) A kit as defined in claim 20 wherein said kit comprises buffer means for

controlling the pH of said aqueous medium selected from the group consisting of

glycine-glycine-HCl, potassium hydrogen phthalate-phthalic acid, citric acid-Na₂HPO₄,

citric acid-KH₂PO₄-H₃BO₃-diethylbarbituric acid-NaOH, citric acid-sodium citrate,

dimethylglutaric acid-sodium dimethylglutarate, acetic acid-sodium acetate, succinic

acid-sodium succinate, potassium hydrogen phthalate-dipotassium phthalate, sodium

cacodylate-cacodylic acid, sodium hydrogen maleate-disodium maleate, Na₂HPO₄-

NaH₂PO , sodium bicarbonate-5% CO₂, imidazole-imidazole-HCl, boric acid-sodium

borate, and the following buffers known to one skilled in the art: Tris, MES, BIS-

TRIS, ADA, ACES and PIPES.

22) A method of disinfecting an object comprising the steps of:

contacting said object to be disinfected with a disinfecting iodine solution

comprising a persulfate salt in a minimum concentration of 100 ppm; an iodide salt in

a minimum concentration of 50 ppm and a buffer to cause said solution to have a pH of

less than about 6.5.