Odorless aromatic dialdehyde disinfecting and sterilizing composition

An odorless sterilizing and disinfecting solution containing 0.025 to 1.0 weight percent phthalaldehyde.

FIELD OF INVENTION 
This invention relates to stable, odorless sterilizing and high level 
disinfecting compositions which contain a water soluble aromatic 
dialdehyde as the active ingredient. The aromatic dialdehyde employed is 
1,2-benzenedicarboxaldehyde, commonly referred to as phthalaldehyde. 
PRIOR ART 
Saturated dialdehyde sterilizing and disinfecting compositions are well 
known. Pepper et al., U.S. Pat. No. 3,016,328; Stonehill, U.S. Pat. No. 
3,282,775; Boucher, U.S. Pat. Nos. 3,708,263, 3,912,450, 3,968,248 and 
3,968,250; and Buchalter, U.S. Pat. No. 3,983,252 all disclose the use of 
glutaraldehyde in aqueous or alcoholic solutions used to disinfect or 
sterilize medical devices or environmental surfaces. 
Jacobs, U.S. Pat. No. 4,436,754 discloses low odor glutaraldehyde 
sterilizing and disinfection compositions. 
Rehn and Nolte in Zentralblatt fuer Bakteralogie, Parasitenkunde, 
Infektionskrankheitec und Hygiene., 1 Abt. Orig. B 168, pp. 507-516 (1979) 
disclose that a range of aromatic monoaldehydes and one aromatic 
dialdehyde, terephthalaldehyde, have bacteriostatic and fungistatic 
activity. 
Rehn, Nolte, and Zerling in Zentralblatt fuer Bakteralogie, Parasitenkunde, 
Infektionskrankheitec und Hygiene, 1 Abt. Orig. B 172, pp 508-519 (1981) 
disclose that phthalaldehyde, isophthalaldehyde and terephthalaldehyde all 
have bacteriostatic and fungistatic activity. 
Commercially available high level disinfecting glutaraldehyde compositions 
of the type disclosed in the above mentioned U.S. Patents have long been 
considered to be effective against a broad range of microorganisms, 
including Mycobacterium tuberculosis in ten (10) minutes at a temperature 
of 20.degree. C. The test employed to make the determination of 
effectiveness was the AOAC Tuberculocidal Test, as specified in Official 
Methods of Analysis of the Association of Official Analytical Chemists, 
14th Edition, 1984, Sections 4,045-4.050. In this Test, the organism 
employed is Mycobacterium bovis BCG. 
It is now apparent that the standard AOAC test method gives highly erratic 
and variable results. This test method can show that a disinfectant 
composition is effective against Mycobacterium bovis BCG in 10 minutes, 
when in fact it is much less effective than the test indicated. An 
improved test method, which is both reproducible and quantitative, has 
been developed. The new test method uses the same test organism as the 
above mentioned AOAC Tuberculocidal Test. In this new test method, nine 
milliliters (ml) of the germicide to be tested is placed in a tube, put 
into a water bath and allowed to come to the desired temperature. One ml 
of the test organism (M. bovis BCG) is added to the tube containing the 
germicide to be tested. At appropriate time intervals, aliquots of the 
germicide-cell suspension are removed and added directly to an equal 
volume of appropriate neutralizer and mixed thoroughly. Ten-fold dilutions 
of the neutralized sample are prepared with saline dilution blanks. One ml 
of the appropriate dilutions are collected on the surface of membrane 
filters having a pore size of 0.45 micrometers. The filters are then 
washed with at least 50 ml of saline. The filters are placed on agar plate 
and incubated in plastic bags for 15 to 20 days at 37.degree. C. The 
surviving colonies are then counted. Survival curves are constructed to 
determine the tuberculocidal activity of the solution. The data is plotted 
as S/S.sub.o vs. time. S.sub.o is the initial viable count of the test 
organism culture and S is the viable count at each time point. 
When commercial glutaraldehyde solutions are tested using the new 
quantitative test method, these compositions do not kill the required 
1.times.10.sup.5 Mycobacterium bovis BCG in 10 minutes at 20.degree. C. 
The additional exposure time required for complete kill at 2020 may be as 
much as several hours. This exposure time becomes impractical, since the 
desired turn-around time for disinfection of equipment, especially 
heat-sensitive fiberoptic endoscopes, in the hospital is 30 minutes or 
less. In order to achieve this equipment turn-around time, a disinfection 
time of 10 minutes or less is required. In order to obtain a 10 minute 
kill time, a temperature of 30.degree. C. is required. Since the normal 
hospital room temperatures are between 20.degree. C. and 25.degree. C., 
additional costs associated with heating conventional glutaraldehyde 
compositions would be required to kill all the organisms within the 
desired 10 minute time frame. 
High level disinfectants are not only capable of rapid kill against 
Mycobacteria, but are effective against the resistant nonlipid and small 
viruses and with extended exposure times, capable of actual sterilization. 
It is well known by one skilled in the art that the degree of 
effectiveness of high level disinfectants is not only controlled by 
temperature and contact time, but is dependent on active ingredient 
content and the solution pH. The previously cited references about 
aromatic dialdehydes do not recognize that phthalaldehyde is a high level 
disinfectant. It has excellent activity against Mycobacterium tuberculosis 
and Poliovirus Type I. These references also do not recognize that the 
corresponding 1,3- and 1,4-isomers have little if any high level 
disinfecting activity. Compositions which contain low concentrations of 
phthalaldehyde (e.g., 0.25%) as the sole active ingredient are effective 
against the above-mentioned organisms in 10 minutes or less at a 
temperature of 20.degree. C. Phthalaldehyde, at the same low 
concentrations, has sporicidal activity against Bacillus subtilis and 
Clostridium sporogenes spores in 24 hours at a temperature of 20.degree. 
C. At higher concentrations (e.g., 1.0%) of phthalaldehyde, sterilization 
is achieved in 10 hours. The sporicidal and high level disinfecting 
activities of compositions with phthalaldehyde are maintained over the pH 
range 3 to 9. 
Storage stability and ease of product use are two important considerations 
when selecting sterilizing and high level disinfecting solutions. 
Glutaraldehyde-based compositions are more effective as high level 
disinfecting and sterilizing solutions at alkaline pH than at neutral or 
acidic pH values. However, glutaraldehyde and other similar aldehydes with 
alpha hydrogens autopolymerize at an alkaline pH. Compositions containing 
these aldehydes at an alkaline pH experience a reduction in the effective 
concentration of the aldehyde with time and, therefore, have limited 
storage stability. In order to overcome this problem, the aldehyde 
composition must be packaged in two or more components. These aldehydes 
can be formulated in an aqueous solution at an acid pH, and activated with 
an alkalinating agent immediately prior to use, shifting the pH to the 
alkaline range. This procedure is disclosed in the prviously-mentioned 
Pepper et al. patent, U.S. Pat. No. 3,016,328. Unlike the aforementioned 
aldehydes, phthalaldehyde does not have alpha hydrogens and therefore 
cannot undergo autopolymerization at an alkaline pH. Compositions 
containing phthalaldehyde can be formulated as a single component. These 
compositions have excellent stability over a pH range of 3 to 9. They do 
not lose their effectiveness during storage. 
Glutaraldehyde, at normal use concentrations, has been reported by some 
hospital personnel to have a pungent odor and be irritating to the eyes 
and nasal passages. Jacobs, U.S. Pat. No. 4,436,754, discloses the use of 
glycol additives to reduce the odor and irritation properties of 
glutaraldehyde compositions. Compositions containing phthalaldehyde as the 
sole active ingredient are odorless and nonirritating to the eyes and 
nasal passages. 
Since equipment turn-around time is very important when considering methods 
for high level disinfection and sterilization, compositions that do not 
coagulate blood or fix tissue to equipment are very desirable. In 
addition, these properties also aid in the disinfection and sterilization 
process by insuring better surface contact between equipment and the 
compositions. Glutaraldehydebased compositions tend to coagulate blood and 
fix tissue to surfaces. Therefore, careful equipment cleaning is a 
necessary procedure prior to disinfection and sterilization. 
Phthalaldehyde compositions do not coagulate blood or fix tissue to 
surfaces. Because of the aforementioned properties and improved efficacy 
of phthalaldehyde compositions, disinfection and sterilization procedures 
with these compositions should be faster and more thorough. 
SUMMARY OF THE INVENTION 
It has now been discovered that compositions containing low levels of the 
active ingredient phthalaldehyde are high level disinfecting and 
sterilizing solutions at 20.degree. C. These compositions at pH 3 to 9 are 
highly effective against not only gram positive/gram negative bacteria and 
fungi, but also the difficult to kill organisms such as Mycobacterium 
tuberculosis, Poliovirus Type I, and Bacillus subtilis and Clostridium 
sporogenes spores. In addition, phthalaldehyde compositions are odorless 
and are nonirritating to eyes and mucous membranes. The compositions are 
stable over a broad pH range and therefore can be packaged as a single 
component without loss of effectiveness during storage. Phthalaldehyde 
compositions also do not coagulate blood or fix tissue on equipment 
surfaces. 
DESCRIPTION OF THE INVENTION 
Phthalaldehyde has the structure: 
##STR1## 
Phthalaldehyde is present in the composition, at use concentration, in 
amounts of between 0.025% and 1.0% by weight. Higher concentrations, e.g., 
up to 2%, could be used if desired. The preferred concentration of 
phthalaldehyde at use dilution is 0.05% to 0.5% by weight. Higher 
concentrations of phthalaldehyde may be used for shipping the composition 
to the point of use and the composition could then be diluted with water 
to the desired use concentration. The limit on the amount of 
phthalaldehyde used in the concentrate composition is a function of the 
solubility of phthalaldehyde in water, which is 5% w/w. To achieve 
compositions of phthalaldehyde with greater than 5% w/w, a water miscible 
co-solvent can be used. Suitable co-solvents include methanol, ethanol, 
isopropanol, glycols, tetrahydrofuran, dimethylsulfoxide and dioxane. 
An alkalinating or acidifying salt is used in the composition as a buffer 
to maintain a desired composition pH during storage and use. The buffer 
may be of the type disclosed in the Pepper et al. U.S. Pat. No. 3,016,328 
which is an alkali metal carbonate or bicarbonate, e.g., sodium 
bicarbonate or potassium bicarbonate or may be a phosphate. The buffer may 
also be an organic carboxylate such as sodium citrate, sodium acetate, 
potassium hydrogen phthalate, potassium citrate or potassium acetate. The 
particular salt or mixture of salts are present in a sufficient amount, 
0.05% to 2.5% based on the total weight of the solution, to give the 
desired pH. The disinfecting properties of the composition are not pH 
dependent. However, at low phthalaldehyde concentrations (e.g., 0.5% or 
less) the sporicidal activity of the composition is somewhat pH dependent. 
The optimal pH range for sporicidal activity is between 6 and 8. 
The composition may contain other ingredients such as a surfactant, a 
corrosion inhibitor, antioxidant, a sequesterent, a dye or a fragrance. 
The use of these other ingredients is well-known in the art. 
The compositions of the present invention may be formulated in one or more 
components. However, if the composition is formulated in two or more 
parts, the components are combined immediately prior to use.

In the following Examples, all percentages are weight percentages, based on 
the total weight of the solutions unless otherwise indicated. In examples 
showing tuberculocidal test data, the new tuberculocidal test methodology 
previously described was used. 
EXAMPLE I 
In this example, a small amount of phthalaldehyde, and amounts of 
isophthalaldehyde and terephthalaldehyde at their water solubility limit 
were tested in aqueous solutions to determine their effectiveness against 
Mycobacterium bovis at 20 C. Use of 20% alcohol co-solvent did not 
significantly increase the amounts of isophthalaldehyde and 
terephthalaldehyde in the test solution. The solutions were buffered to pH 
8.0 with dipotassium hydrogen phosphate. The results are shown in Table I. 
TABLE I 
______________________________________ 
% 
Aromatic Number of Organisms 
Aromatic Dialdehyde 
Surviving 
Dialdehyde (w/w) 0 min 10 min 20 min 
______________________________________ 
Phthalaldehyde 
0.10 2.4 .times. 10.sup.5 
0 0 
Isophthalaldehyde 
0.25 2.8 .times. 10.sup.5 
2.3 .times. 10.sup.5 
2.3 .times. 10.sup.5 
Terephthalaldehyde 
0.10 2.8 .times. 10.sup.5 
3.3 .times. 10.sup.5 
4.0 .times. 10.sup.5 
______________________________________ 
The results show that phthalaldehyde, has excellent tuberculocidal activity 
at low concentration, while isophthalaldehyde and terephthalaldehyde do 
not have any appreciable tuberculocidal activity. 
EXAMPLE II 
A series of solutions containing from 0.01 to 0.75% phthalaldehyde, 
buffered at pH 8 as in Example I, were tested for their effectiveness in 
killing Mycobacterium bovis BCG at 20.degree. C. The results are shown in 
Table II. 
TABLE II 
______________________________________ 
% Phthal- 
aldehyde Number of Organisms Surviving 
(w/w) 0 min 2 min 5 min 10 min 
______________________________________ 
0.075 1.9 .times. 10.sup.5 
1.2 .times. 10.sup.3 
0 0 
0.05 1.9 .times. 10.sup.5 
5.0 .times. 10.sup.3 
0 0 
0.025 1.9 .times. 10.sup.5 
2.4 .times. 10.sup.4 
3.2 .times. 10.sup.3 
0 
0.01 1.9 .times. 10.sup.5 
8.0 .times. 10.sup.4 
4.0 .times. 10.sup.4 
2.0 .times. 10.sup.4 
______________________________________ 
The results indicate that a concentration of only 0.025% phthalaldehyde is 
tuberculocidal within 10 minutes at 20.degree. C. 
EXAMPLE III 
Portions of a solution containing 0.1% phthalaldehyde and dipotassium 
hydrogen phosphate were adjusted to different pH levels with H.sub.3 
PO.sub.4 and KOH. The solutions were tested against Mycobacterium bovis 
BCG at 20.degree. C. to determine the effect of pH on the effectiveness of 
the solutions. The results are shown in Table III. 
TABLE III 
______________________________________ 
Number of Organisms Surviving 
pH 0 min 2 min 5 min 
______________________________________ 
3 3.8 .times. 10.sup.5 
1.4 .times. 10.sup.3 
0 
5 3.8 .times. 10.sup.5 
5.2 .times. 10.sup.2 
0 
7 3.8 .times. 10.sup.5 
2.0 .times. 10.sup.1 
0 
9 3.8 .times. 10.sup.5 
2.0 .times. 10.sup.2 
0 
______________________________________ 
The results indicate that the tuberculocidal activity of phthalaldehyde is 
not pH dependent. 
EXAMPLE IV 
Solutions containing 0.1, 0.5 and 1.0% phthalaldehyde buffered to pH 8 with 
dipotassium hydrogen phosphate were tested to determine the minimum 
effective concentration required to inactivate a suspension of about 
1.times.10.sup.6 (6 logs) Poliovirus Type I after 5 minutes exposure to 
the solutions at 20.degree. C. The results are shown in Table IV. 
TABLE IV 
______________________________________ 
% Phthalaldehyde 
Reduction in Virus Titer 
(w/w) (log.sub.10) 
______________________________________ 
0.1 3.0 
0.5 5.5* 
1.0 5.5* 
______________________________________ 
*Total inactivation of virus 
The results show that the minimum effective concentration of phthalaldehyde 
required to totally inactivate Poliovirus Type I in 5 minutes at 
20.degree. C. is between 0.1 and 0.5%. 
EXAMPLE V 
Solutions containing 0.1% phthalaldehyde buffered to pH 7.5 with 
dipotassium hydrogen phosphate and pH 6 with potassium acid phthalate were 
tested against a suspension of about 4.7.times.10.sup.6 (6.67 logs) 
Poliovirus Type I to determine the effect of pH on the reduction of virus 
titer after 5 minutes exposure to the solutions at 20.degree. C. The 
results are shown in Table V. 
TABLE V 
______________________________________ 
Reduction in Virus Titer 
pH (log.sub.10) 
______________________________________ 
6 4.2 
7.5 4.7 
______________________________________ 
The results indicate that the activity of phthalaldehyde against Poliovirus 
Type I is not significantly dependent on pH over the range of slightly 
acidic to slightly alkaline. 
EXAMPLE VI 
A solution containing 0.1% phthalaldehyde buffered to pH 8 with dipotassium 
hydrogen phosphate was tested to determine its effectiveness in killing 
Pseudomonas aeruginosa (gram -) and Staphylococcus aureus (gram+) at 
20.degree. C. using the standard AOAC Use-Dilution Method (AOAC Official 
Methods of Analysis, 14th edition, 1984, page 67). The results are shown 
in Table VI. 
TABLE VI 
______________________________________ 
No. of Positives(Failure)/No. of Total Tests 
Organism 5 Min 10 Min 
______________________________________ 
Pseudomonas 
aeruginosa 0/30 0/30 
Staphylococcus 
aureus 1/30 0/30 
______________________________________ 
The results show that phthalaldehyde is cidal against both gram negative 
and gram positive bacteria within 10 minutes contact time at 20.degree. C. 
EXAMPLE VII 
The solution tested in Example VI was tested to determine its effectiveness 
in killing Trichophyton mentagrophytes at 20.degree. C. using the standard 
AOAC Fungicidal Method (AOAC Official Methods of Analysis, 14th edition, 
1984, page 69). The results are shown in Table VII. 
TABLE VII 
______________________________________ 
Growth (+) or No Growth (-) 
Test Solution 5 Min 10 Min 15 Min 
______________________________________ 
Phthalaldehyde (0.1%) 
-- -- -- 
______________________________________ 
The results show that phthalaldehyde is fungicidal in 5 minutes at 
20.degree. C. 
EXAMPLE VIII 
Solutions containing from 0.5% to 2.7% phthalaldehyde were tested to 
determine the minimum effective concentration required to kill spores of 
Bacillus subtilis and Clostridium sporogenes at 20.degree. C. in 10 hours 
over the pH range 4 to 8 using the standard AOAC Method (AOAC Official 
Methods of Analysis, 14th edition, 1984, page 72). Solutions at pH 8 were 
buffered as in Example I and solutions at pH 6 and 4 were buffered with 
potassium acid phthalate. The results are shown in Table VIII. 
TABLE VIII 
______________________________________ 
Total No. of Positives(Failures)/Total No. 
% Phthal- of Tests 
aldehyde B. subtilis C. sporogenes 
(w/w) pH sutures penicylinders 
sutures 
penicylinders 
______________________________________ 
2.7 8 0/30 0/30 0/30 0/30 
1.0 8 0/30 0/30 1/30 0/30 
0.5 8 16/30 0/30 0/30 2/30 
1.0 6 0/30 0/30 0/30 0/30 
0.5 6 30/30 19/30 1/30 0/30 
1.5 4 0/30 0/30 0/30 0/30 
1.0 4 2/30 4/30 0/30 0/30 
______________________________________ 
The results indicate that the minimum effective concentration of 
phthalaldehyde which is sporicidal at 20.degree. C. in 10 hours is about 
1% at pH 8, 6 and 4. 
EXAMPLE IX 
A series of solutions containing from 0.1 to 1.0% phthalaldehyde was tested 
to determine the minimum effective concentration required to kill spores 
of B. subtilis and C. sporogenes at 20.degree. C. in 24 hours over the pH 
range 4 to 8. The results are shown in Table IX. Note: C. sporogenes was 
note tested in all cases, since B. subtilis was shown to be the more 
resistant organism in Example VIII. 
TABLE IX 
______________________________________ 
Total No. of Positives(Failures)/Total No. 
% Phthal- of Tests 
aldehyde B. subtilis C. sporogenes 
(w/w) pH sutures penicylinders 
sutures 
penicylinders 
______________________________________ 
1.0 8 0/30 0/30 0/30 0/30 
0.5 8 0/30 0/30 0/30 0/30 
0.25 8 0/30 0/30 -- -- 
0.1 8 14/30 11/30 -- -- 
1.0 6 0/30 0/30 0/30 0/30 
0.5 6 0/30 0/30 0/30 0/30 
0.25 6 1/30 0/30 -- -- 
0.1 6 30/30 30/30 -- -- 
1.0 4 0/30 0/30 0/30 0/30 
0.5 4 7/30 5/30 0/30 0/30 
0.25 4 28/30 30/30 -- -- 
0.1 4 28/30 29/30 -- -- 
______________________________________ 
The results indicate that the minimum effective concentration of 
phthalaldehyde which is sporicidal at 20.degree. C. in 24 hours is about 
0.25% at both pH 8 and 6 and between 0.5% and 1.0% at pH 4. 
EXAMPLE X 
Solutions containing 0.3% phthalaldehyde buffered to pH 8 and pH 6 as in 
Example V were stored at 40.degree. C. for 6 months to determine the 
effect of pH on the stability of the solutions under accelerated aging 
conditions. The results are shown in Table X. 
TABLE X 
______________________________________ 
Storage % Phthal- 
time aldehyde 
(months) pH (.+-.0.03%) 
______________________________________ 
0 8.00 0.28 
2 7.87 0.28 
6 7.76 0.32 
0 6.00 0.26 
2 5.99 0.26 
6 6.00 0.24 
______________________________________ 
The results show that phthalaldehyde solutions have excellent storage 
stability at both alkaline and acidic pH. 
EXAMPLE XI 
Glass slides that were stained with 0.05 grams of human blood and dried for 
5 minutes at 22.degree. C. to 25.degree. C. were immersed in two solutions 
containing 0.5% phthalaldehyde. The pH of both phthalaldehyde solutions 
was adjusted to pH 7.5. The compositions of the phthalaldehyde solutions 
only differed in the presence or absence of 0.2% nonionic surfactant. 
Observations of the blood removal properties for the phthalaldehyde 
solutions were made after 5 and 14 minutes contact time with the stained 
slides. The blood removal property of the solutions was graded on the 
basis of assigning a number from 1 to 7; where 1 signified no removal and 
7 complete removal. The results were compared to the blood removal 
capabilities of a 2% glutaraldehyde solution (pH 7.5) with 0.2% nonionic 
surfactant. The results are shown in Table XI. 
TABLE XI 
______________________________________ 
Cleaning ratings 
5 min. 15 min. 
Test solutions contact contact 
______________________________________ 
2% Glutaraldehyde/ 1 3 
0.2% Surfactant 
0.3% Phthalaldehyde 
7 7 
0.3% Phthalaldehyde/ 
7 7 
0.2% Surfactant 
______________________________________ 
The results show that phthalaldehyde compositions removed 100% of the blood 
in 5 minutes from the stained slides.