U.S. patent number 3,912,450 [Application Number 05/361,148] was granted by the patent office on 1975-10-14 for method for synergistic disinfection or sterilization.
This patent grant is currently assigned to Wave Energy Systems, Inc.. Invention is credited to Raymond Marcel Gut Boucher.
United States Patent |
3,912,450 |
Boucher |
October 14, 1975 |
Method for synergistic disinfection or sterilization
Abstract
A method for disinfecting or sterilizing medical, surgical,
dental instruments or other objects in liquid phase with improved
sporicidal compositions. The method is based upon the synergistic
effects observed when combining nonionic and anionic surfactants
with aqueous or alcoholic glutaraldehyde solutions. The method can
be used also with ultrasonic irradiation over a wide frequency
range (10 to 850 kHz). Two types of particularly effective
synergistic sporicidal compositions are also described.
Inventors: |
Boucher; Raymond Marcel Gut
(New York, NY) |
Assignee: |
Wave Energy Systems, Inc. (New
York, NY)
|
Family
ID: |
27561148 |
Appl.
No.: |
05/361,148 |
Filed: |
May 17, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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155233 |
Jun 21, 1971 |
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Current U.S.
Class: |
422/20; 514/705;
422/36 |
Current CPC
Class: |
C11D
11/007 (20130101); A61L 2/00 (20130101); C11D
1/72 (20130101); C11D 3/2072 (20130101); A01N
35/02 (20130101); A61L 2/025 (20130101); C11D
3/48 (20130101); A01N 35/02 (20130101); A01N
2300/00 (20130101) |
Current International
Class: |
A01N
35/02 (20060101); A01N 35/00 (20060101); A61L
2/02 (20060101); A61L 2/00 (20060101); A61L
2/025 (20060101); C11D 3/48 (20060101); C11D
1/72 (20060101); C11D 11/00 (20060101); C11D
3/20 (20060101); A61l 013/00 (); A61l 001/00 () |
Field of
Search: |
;21/54R,54A,12R,12A,58
;424/333,127 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Sidewell et al.; "Potentially Infectious...Bed Pads"; Applied
Microbiology; Vol. 19; No. 1; Jan. 1970; pp. 53-59. .
Borick et al., "Alkalimized Glutaraldehyde, A New Antimicrobial
Agent," J. of Pharmaceutical Sciences, Vol. 53, No. 10, 10-64, pp.
1273-1275..
|
Primary Examiner: Richman; Barry S.
Attorney, Agent or Firm: Shoemaker and Mattare
Parent Case Text
This is a division of application Ser. No. 155,233 filed June 21,
1971.
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A method for disinfecting or sterilizing medical, dental,
surgical instruments or other objects in liquid phase at a
temperature of at least 15.degree.C comprising contacting said
object with a sporicidal composition comprising from about 0.1
percent by weight to about 5 percent by weight of glutaraldehyde
and from about 0.01 percent by weight to about 1 percent by weight
of a nonionic surface active agent which is a mixture of
ethoxylates of isomeric linear alcohols having the following
formula:
wherein n is 9 to 13 and x is 9 to 13.
2. The method of claim 1 wherein the nonionic surface active agent
is partially replaced by an anionic alkyl aryl sulfonate.
3. A method of disinfecting or sterilizing a contaminated object in
liquid phase at a temperature of at least 15.degree.C, comprising
contacting said object with an aqueous sporicidal solution
comprising from about 0.1 percent by weight to about 5 percent by
weight of glutaraldehyde and from about 0.01 percent by weight to
about 1 percent by weight of a nonionic surface active agent which
is a mixture of ethoxylates of isomeric linear alcohols having the
following formula: ##EQU3## wherein n is 9 to 13 and x is 9 to 13,
while simultaneously subjecting said solution to sonic or
ultrasonic fields having a frequency of from about 10 kHz to about
850 kHz and an acoustic energy density of about 1 watt per liter to
about 5 watts per cubic centimeter inside the irradiated liquid
phase.
4. The method of claim 3 wherein part of the nonionic surface
active agent is replaced by an anionic alkyl aryl sulfonate.
5. The method of claim 3 wherein the pH of the aqueous solution is
from 1 to 7.
6. The method of claim 3 wherein the aqueous solution is buffered
by addition of alkaline salt to a pH of from 7 to 9.
7. The method of claim 3 wherein the object to be sterilized is
contacted with the aqueous solution at a temperature of from
15.degree. to 75.degree.C for from 1 minute to 2 hours.
Description
BACKGROUND OF THE INVENTION
This invention relates to a method for disinfecting or sterilizing
objects in liquid phase with improved chemosterilizer compositions.
The method object of our invention is based upon the synergistic
sporicidal effects observed when using relatively moderate
temperatures combined or not combined with ultrasonic irradiation
in specially formulated sporicidal compositions. The latter are
based upon active combinations of glutaraldehyde with nonionic
surfactants such as ethoxylates or isomeric linear alcohols
(C.sub.11 to C.sub.15) or anionic alkyl aryl sulfonates.
Through a proper choice of temperatures, acoustic energy density
and chemical composition the method object of the present invention
enables reducing from hours to minutes the time requirements for
surface disinfection or sterilization of heat sensitive
materials.
Low temperature surface sterilization in liquid phase has been
limited in the past to the use of two chemosterilizer agents:
formaldehyde and alkaline glutaraldehyde solutions. This limited
choice indeed contrasts with the large number of chemical
bactericides available (Quarternary Ammonium compounds, chlorine
containing compounds, Iodophores, Amphoteric compounds, etc.) when
one does not require sporicidal action.
Formaldehyde is one of the oldest chemosterilizers employed for the
destruction of spores, and, although 1 percent to 2 percent
solutions have been used, a relatively long period of time (up to
20 hours) is required to destroy Bacillus subtilis var. niger
spores. A somewhat shorter time is needed if one uses higher
concentrations of formaldehyde (around 8 percent) in isopropyl
alcohol. This solution, called Formalin has several drawbacks. The
irritating fumes of formaldehyde limit its usefulness, and its
toxicity for tissue requires that disinfected materials be
thoroughly rinsed with sterile water before use.
Alkalanized glutaraldehyde solutions known commercially under the
trade name CIDEX are the only widely used for practical
applications today. They consist of a 2 percent aqueous
glutaraldehyde solution buffered by suitable alkalinating agents
(generally 0.3 percent sodium bicarbonate) to pH of 7.5 to 8.5. In
the acid state at room temperature the glutaraldehyde solution is
stable for long periods of time when stored in a closed container.
However, when rendered alkaline, the glutaraldehyde gradually
undergoes polymerization and loses its activity. Above pH 9 the
polymerization proceeds very rapidly. In the 7.5 to 8.5 pH range
polymerization is slower, but it is acknowledged by the
manufacturer himself that sporicidal activity disappears after 2
weeks. (ARBROOK, Bulletin JR 8016, 1968)
Even when using a fresh solution of 2 percent buffered
glutaraldehyde, the time needed at room temperature to achieve
complete sterilization of Bacillus subtilis with the AOAC
Pennycylinder method is said to be comprised between 3 and 10 hours
according to spore dryness.
The impossibility to store the sporicidal solution over extended
periods of time, the need to buffer each time before use and the
long contact time required (several hours) to achieve sterility
made me develop the method and new sporicidal composition objects
of the present invention.
As hereabove stated, Alkalanized Glutaraldehyde has been widely
used as a chemical sterilizing agent since its antimicrobial
characteristics were first described in the U.S. Pat. No. 3,016,328
(1962). R. E. Pepper and E. R. Lieberman were the first to point
out in the above-mentioned patent that aqueous glutaraldehyde
solutions were mildly acid and in this state they stressed that
they did not exhibit sporicidal characteristics. Only when the
solution was buffered by suitable alkalinating agents to a pH of
7.5 to 8.5, did the solution become antimicrobially active. (see
American Journal of Hospital Pharmacy 20: 458-465, Sept. 1963).
This point was emphasized in the U.S. Pat. No. 3,016,328 (1962)
which stated (page 1, column 2, line 34) that the invention resided
in the discovery that a saturated dialdehyde containing 2 to 6
carbon does, in fact, have sporicidal activity when it is combined
with a lower alkanol and an alkalinating agent.
More recently G. Sierra in Canada (Canadian Pat. No. 865,913, March
1971) showed that the conclusions of R. E. Pepper and E. R.
Lieberman were only valid in the temperature range
(22.degree.-23.degree.C) indicated by these authors in their U.S.
patent. The Sierra's Canadian patent indicates that strong
sporicidal activity is exhibited by acid non-buffered
non-alkalinized glutaraldehyde solutions when operating at
temperatures higher (generally around 45.degree.C) than those
mentioned in R. E. Pepper's patent. This observation was confirmed
in my own experiments. Moreover, I found, and this is one of the
objects of the present invention, that with the proper combination
of acid glutaraldehyde with certain nonionic or anionic surfactants
at temperatures greater than 15.degree.C but specially above
45.degree.C higher sporicidal activities than those mentioned in G.
Sierra's patent can be achieved.
An increase in bactericidal and sporicidal activity through the
combined use of glutaraldehyde (both acid and alkaline) with
surfactants had been previously disclosed by A. A. Stonehill in
U.S. Pat. No. 3,282,775 (November 1966). This inventor, however,
referred only to the use of cationic agents. Several examples were
given in the A. A. Stonehill's patent. They all pertained to
chemical compositions using glutaraldehyde solutions with
quaternary ammonium salts or cetylpyridinum chloride both of which
exhibited sporicidal characteristics at room temperature within the
4 to 9 pH range.
It is an object of the present invention to show that a
glutaraldehyde solution combined with nonionic or anionic agents
such as ethoxylates of isomeric linear alcohols or alkyl aryl
sulfonates is far more active than any other previously known
sporicidal formula based upon the mixing of glutaraldehyde with
cationic agents.
It is a further object of the present invention to show that the
combined use of glutaraldehyde solutions with nonionic or anionic
surfactants is effective over a wider pH range (1 to 9) while also
working at any temperature inside the 15.degree.C to 75.degree.C
range.
It is a further object of this invention to show that one can
considerably reduce the sterilization time through simultaneous
sonic or ultrasonic irradiation of the sporicidal compositions
based upon a mixture of glutaraldehyde with nonionic or anionic
surfactants.
To aid in the understanding of my invention I shall briefly review
the various physical or chemical mechanisms which play a role in
the strong sporicidal effects observed in the method object of the
present invention.
A few bacteria have evolved a highly effective mechanism for
ensuring their survival; they exhibit an elementary form of
differentiation in which, under certain conditions, the relatively
sensitive vegetative form of the organism can give rise to a
resistant dormant form, called a spore. Bacterial spores are much
more resistant to adverse effects of heat, radiation and chemicals
than their corresponding vegetative cells. The resistance of spores
differs within the microbial population and species variation is
common. Among the spores which were used to evaluate the methods
object of the present invention I shall mention Bacillus subtilis,
Bacillus stearothermopilus, Bacillus pumilus, Clostridium
sporogenes and Clostridium tetani.
A bacterial spore is typically about one micro diameter and
consists essentially of a small cell, often called the core or
spore protoplast, surrounded by a number of specialized layers. The
principal layers are the thick cortex and the multilayered coats
and, around spores of certain species, a further loose and thin
layer called exosporium.
At the moment it is believed (C. S. Phillips, Bact. Rev. 1962) that
alkylating agents such as ethylene oxide, .beta. propiolactone,
formaldehyde, glutaraldehyde as well as other aldehydes attack the
sulfhydryl (--SH), hydroxyl (--OH), amino (--NH.sub.2) and carboxy
##EQU1## groups present in spore cell proteins. More recently T. J.
Munton and A. D. Russell (J. Appl. Bact., 1970) stated that the
chemical sites for glutaraldehyde action could involve --NH.sub.2
groups, including cross linking reactions between these groups (D.
Hopwood, Histochemie, 1968). According to these authors, however,
the suggested mechanism does not exclude sites of action with other
chemical groups.
T. J. Munton and A. D. Russell (J. Appl. Bact, 1970) also showed
that the uptake of acid glutaraldehyde and alkaline glutaraldehyde
(sodium bicarbonate buffer) is similar and that both are of the
Langmuirian type. This was demonstrated with E. Coli and Bacillus
megatorium. In other words as more sites of the bacterial cell or
spores are filled, glutaraldehyde molecules find increasing
difficulty in attaching themselves to the cell or spore. In the
methods object of the present invention it is believed that the
nonionic linear alcohol ethoxylates decrease the surface tension
and increase the wettability at the spore/liquid interface in such
a manner that they promote a faster absorbtion rate of
glutaraldehyde molecules. This could also be the result of the
entraping at the spore/liquid interface of a higher concentration
of glutaraldehyde molecules, said phenomenom being increased in a
logarithmic manner with temperatures inside the
15.degree.-75.degree.C range. Although of a lower magnitude the
same increased rate of absorbtion at the spore/liquid interface is
observed with anionic alkyl aryl sulfonates mixed with nonionic
polyoxethylene alcohol ethers.
When speaking of absorbtion rates, one must point out that the
increased wettability observed with the sporicidal molecules could
be due not only to an increase at the external spore interface but
also to a faster penetration inside the internal spore interfaces,
i.e., across cortex layers, cortex or plasma membrane.
If using one of the sporicidal compositions object of the present
invention in combination with ultrasonic irradiation extremely high
killing rates are observed. This indeed could be explained in the
following manner. As well known, the major component of a spore
cortex layer is a polymer called murein (or peptidoglycan). Murein
is present, in lesser amounts, in the walls of all bacteria. It is
a large, cross-linked, net-like molecule exhibiting several unusual
features. This polymer is acidic, and in spores may exist as a
layer tightly contracted by some positively charged molecules. One
recent theory to account for the extreme heat resistance of spores
supposes that contractile pressure exerted by this structure may
squeeze the central core sufficiently to maintain it in a state so
dry as to confer heat resistance. Ultrasonic irradiation is one of
the most efficient techniques (KY Sergeeva, Sov. Phys. Acoust.,
March 1966) to shake up polymer lattices and produce a fast
depolymerization. This technique is said to be quite efficient over
a wide frequency range both at low (G. Schmid, et al., Kolloid L,
1951) and high frequency (M. A. K. Mostafa, J. Polym. Sci. 1958).
It is therefore understandable that murein depolymerization or a
partial destruction of the tight cross-linked lattice would enable
the aldehyde groups to penetrate and combine faster with the active
spore sites. Nonionic and anionic surfactants will indeed
accelerate the penetration through the loosened polymer lattice.
High intensity ultrasonic energy could also play an important role
through other secondary but important mechanisms.
The proteinaceous outer coats of spores contain a disulphide-rich
protein with some properties close to those of keratins. Since
keratin-like proteins are typically strong, inert towards chemical
reagents and resistant to enzymes they constitute an ideal
protective barrier for spores. High intensity ultrasonics, however,
could physically degrade keratin (J. H. Bradbury, Nature, 1960) and
thus promote a faster penetration of active glutaraldehyde
molecules.
Two more components characteristic of spores are high levels of
calcium (often 2 percent of the spore's dry weight) and dipicolinic
acid (DPA) which may account for over 10 percent of a spore's dry
weight. Under acoustic turbulence ion exchange (Ca depletion) can
take place while the heterocyclic DPA molecule could also be broken
(I. E. Elpiner and A. V. Sokolskaya, Sov. Phys. Acoust. March
1963). In short, ultrasonic energy could either accelerate the
physical diffusion of molecules or active radicals to reaction
sites inside the spores, produce chemical bond breakages of
critical spore components (including site modification) or both. It
could also, especially with alkaline glutaraldehyde, depolymerize
some of the glutaraldehyde in solution. This could be of particular
significance when one remembers that alkalinized glutaraldehyde
gradually loses its activity when polymerization progresses. (A. A.
Stonehill et al., Am. Journ. Hosp. Phar. 1963).
Although the synergistic sporicidal effect due to a combination of
moderate heat, glutaraldehyde solution and high intensity
ultrasonics has been described already in G. Sierra's patent
(Canadian patent application No. 98,416, 1971), the present
invention shows that an addition of nonionic or anionic surfactants
to the glutaraldehyde solution leads in all cases to a substantial
increase in bacteria, virus or spore killing rats.
Having described our sterilization method and the sporicidal
compositions to be used with it, I shall now give several examples
to further illustrate the invention. They are given primarily for
the purposes of illustration and should not be construed as
limiting the invention to the details given.
EXAMPLES
A novel aqueous bactericidal, virucidal and sporicidal composition
of the present invention is prepared with 2 percent glutaraldehyde
(Union Carbide grade) and 0.2 percent of a nonionic surface active
agent which is a mixture of ethoxylates of isomeric linear
alcohols. The linear alkyl hydrophobic portion of the surfactant
being a mixture of C.sub.11 to C.sub.15 linear chains. The
hydrophylic portion being a polyoxyethylene chain (9 to 13
oxyethylene groups) randomly attached to the linear aliphatic chain
through an ether linkage as shown in the following formula:
##EQU2##
The nonionic surfactant used in the formulation object of the
present invention had the following characteristics: Molecular
weight 728, Cloud point (1 percent aqueous solution) 90.degree.C,
Pour point 17.degree.C, 100 percent solubility in water at
25.degree.C, Apparent specific gravity 20.degree./20.degree.C;
1.023, density 8.49 lb/gal at 30.degree.C, viscosity 48 CKS at
40.degree.C, flash point 460.degree.F. (ASTM method D 92).
The anionic surfactant blend with nonionic polyoxethylene alcohol
ethers used in the second formulation object of the present
invention had the following characteristics: Specific gravity 1.02,
density 8.5 lb/gal, clear liquid soluble in hot or cold water, pH
comprised between 6 and 8, freezing point -10.degree.C.
The Union Carbide grade of glutaraldehyde concentrate which was
used to prepare the 2 percent solution used in our tests had the
following characteristics: Specific gravity 1.058 to 1.065 at
20.degree.C, glutaraldehyde concentration 24.5 to 25.5 percent by
weight, pH 2.7 to 3.7 at 25.degree.C, Acidity 0.2 percent by
weight, maximum, calculated as acetic acid, Iron content less than
3 ppm, heavy metals content less than 2 ppm, color 125
platinum-cobalt maximum.
The spores against which the solutions have been tested were vacuum
dried strains of Clostridium Sporogenes (ATCC 7955), Bacillus
globigii, Bacillus pumilus, Bacillus stearothermophilus and
Bacillus Subtilis.
The latter showed the greater resistance to the sporicidal
composition and for the sake of clarity I shall restrict myself to
the presentation of data pertaining to this microorganism.
Tests were conducted in specially designed ultrasonic stainless
steel tanks (Wave Energy Systems series CTG 160) with a 2 gallon
capacity. One gallon of spore suspension was used in each test. The
acoustic output in liquid phase could vary from 10 to 30 watts per
liter of spore suspension. The experimental irradiation frequency
was either 10 kHz or 27 kHz (.+-. 1 kHz). At high frequency (850
kHz, 20 watts/liter to 5 watts/cc) the spore solution was contained
in a 2 gal glass beaker which was placed in a water filled
container fitted at the bottom with a submersible transducer
(glazed cobalt lead zirconate titanate). During all experiments the
temperature was thermostatically controlled to .+-. 1.degree.C of
the recited temperature.
As previously stated, spores of Bacillus subtilis (ATCC 6051) were
used in all the reported experiments. The preparation of clean
spores was accomplished with the G. Sierra and A. Bowman technique
(Journ. Appl. Microbiology, 17: 372-378, 1969). The spores were
pasteurized (80.degree.C, 15 min) and stored at 4.degree.C as
concentrated suspensions in deionized water and used within one
week. The standardization of the spore suspensions was carried out
as described by G. Sierra (Can. Journ. Microbiology, 13: 489-501,
1967).
Glutaraldehyde and glutaraldehyde/surfactant solutions were freshly
prepared in deionized water for each experiment. Concentrated stock
solution of the buffers or sodium bicarbonate were added separately
to pasteurized spore suspensions. The pH values reported here are
those of a complete system after all additions and were read with a
Beckman Zeromatic II pH meter, the calibration of which was checked
before each assay was run. Stirring was continuous, and the pH was
read after allowing the electrode potential to stabilize.
To recover spore survivors efficiently (especially in the lower
dilutions) the effects of glutaraldehyde carryover into the viable
count plates was counteracted by quenching the glutaraldehyde with
sodium bisulphite before plating. After the desired treatment,
samples of 0.5 ml were taken to determine the numbers of surviving
spores. Each sample was diluted immediately into 4.5 ml of 1
percent sodium bisulphite + 0.1 percent peptone solution and
allowed to stand for 10 min, after which further serial dilutions
were made in 0.5 percent sodium bisulphite + 0.1 percent peptone
solution. Colony counts from 0.1 ml amounts of appropriate
dilutions were made on 0.1 percent starch-nutrient agar; duplicate
plates were incubated at 30.degree.C for 3 days. The bisulphite
treatment was found neither to potentiate glutaraldehyde induced
spore inactivation nor cause detectable direct inactivation of
intact spores.
In a few instances it could be of interest to use as a diluent not
only filtered deionized water but a lower alkanol such as methanol,
ethanol, isopropanol and the like. A mixture of both could also be
used and in Table IV we give the results of a test conducted with a
composition comprising 60 percent isopropyl alcohol with 37.8
percent water, 2 percent glutaraldehyde and 0.2 percent nonionic
surfactant. Tables I to V show some typical results of our
experiments conducted with suspensions of Bacillus Subtilis (ATCC
6051) under variable conditions (glutaraldehyde concentration,
different surfactants, varying temperature and pH).
TABLE I ______________________________________ Various
concentration of glutaraldehyde
______________________________________ Initial spores count
10.sup.7 /ml. temperature 55.degree.C. Ultrasonic field: Frequency
27 kHz, Intensity 20 watts/liter pH 5.
______________________________________ Glutaraldehyde Minimum time
in minutes Concentration for 100% kill
______________________________________ 0.1% 20 with ultrasound 2 15
with ultrasound 5 15 with ultrasound 0.1 40 no ultrasound 2 30 no
ultrasound 5 30 no ultrasound 2 10 with ultrasound and non- ionic
surfactant (0.2%) 2 20 no ultrasound but with - nonionic surfactant
______________________________________ (0.2%)
TABLE II ______________________________________ Various
concentration of different synergistic surfactants Initial spores
count 10.sup.7 /ml temperature 55.degree.C Ultrasonic field:
Frequency 27 kHz, Intensity 20 watts/liter Glutaraldehyde
concentration: 2% pH 5. ______________________________________ Type
of surfactant Surfactant Minimum time in min. concentration for
100% kill ______________________________________ nonionic * 0.02%
11 nonionic 0.2 10 nonionic 1 10 anionic ** 0.02 12 anionic 0.2 11
anionic 1 11 cationic *** 0.2 15 no surfactant (glutaraldehyde
alone) 15 ______________________________________ * ethoxylates of
isomeric linear alcohols ** alkyl aryl sulfonate mixed with
polyoxethylene alcohol ethers *** cetylpyridinium chloride
TABLE III ______________________________________ Activity at
various temperatures ______________________________________ Initial
spores count 10.sup.7 /ml Ultrasonic field: Frequency 27 kHz.
Intensity 20 watts/liter Glutaraldehyde concentration 2% --
Nonionic surfactant concentrations 0.2% pH 5
______________________________________ Temperature Minimum time in
min. for 100% kill ______________________________________
15.degree.C 120 25.degree.C 100 45.degree.C 60 55.degree.C 10
65.degree.C 5 ______________________________________
TABLE IV ______________________________________ Activity at various
pH 5 ______________________________________ Initial spores count
10.sup.7 /ml Ultrasonic field: Frequency 27 kHz, Intensity 20
watts/liter Glutaraldehyde concentration 2%, Nonionic surfactant
concentration: 0.2% Temperature: 55.degree.C
______________________________________ Diluent pH Minimum time in
min. for 100% kill ______________________________________ Deionized
water 2.5 11 Deionized water 5 10 Deionized water 6 10 Deionized
water 8 (with buffer) 10 Deionized water 10 (with buffer) 12 Water
and isopropyl alcohol (66%) 6.5 10
______________________________________
TABLE V ______________________________________ Activity at various
ultrasonic frequencies and intensities
______________________________________ Initial spores count
10.sup.7 /ml. Glutaraldehyde concentration 2%, nonionic or anionic
surfactant concentration: 0.2% Temperature: 55.degree.C pH 6
______________________________________ Type of Ultrasonic Minimum
time Surfactant Frequency in min. for in kHz Energy density 100%
kill ______________________________________ nonionic 27 20
watts/liter 10 nonionic 27 30 watts/liter 6 nonionic 27 1
watt/liter 18 nonionic 10 20 watts/liter 10 nonionic 10 30
watts/liter 6 nonionic 850 20 watts/liter 12 nonionic 850 5
watts/cc 4 anionic 27 20 watts/liter 12
______________________________________
The data contained in these tables clearly show the synergistic
effects obtained with two types of sporicidal compositions based
upon nonionic and anionic surfactants dissolved in glutaraldehyde.
They also show that the teachings of the invention may be practiced
within the following parameters:
Glutaraldehyde concentration: from about 0.1 percent to about 5
percent
Nonionic, or anionic blend with nonionic surfactant: from about 0.1
percent to about 1 percent.
Acoustic field frequency: from about 10 kHz to about 850 kHz
Acoustic field energy density: from about 1 watt/liter to about 5
watt/cc
Diluent: water or lower alkanol
Temperature: above 15.degree.C
pH range: 2 to 10
Although several specific examples of the inventive concept have
been described for purposes of illustration, the invention should
not be construed as limited thereby nor to the specific features
mentioned therein except as the same may be included in the claims
appended hereto. It is also understood that changes, modifications,
and variations may be made without departing from the spirit and
scope of the present invention.
* * * * *