US2979468A - Test composition for determining the concentration of quaternary ammonium compounds in aqueous solution - Google Patents

Description

United States P 6 1 OF TEST COMPOSITION FOR DETERMINING THE CONCENTRATION OF QUATERNARY AMMO- NIUM COMPOUNDS IN AQUEOUS SOLUTION Morris E. Anerbach, Albany, and Robert S. Browning, Schodack, N.Y., assignors to Sterling Drug Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed Apr. 19, 1960, Ser. No. 23,146 a p scram. or. 252-408) This invention relates to a novel chemicalcomposition useful for determination of the concentration of quaternary ammonium compounds in'solution, particularly for distinguishing between aqueous solutions containing different small concentrations of quaternary ammonium compounds.

Manyv surface-active quaternary ammonium compounds have valuable antibacterial properties which adapt them to wide use as sanitizing and disinfecting agents, for instance in washing and rinsing a wide variety of articles which come into contact with food, such as eating and drinking utensils, dairy equipment, counter tops, brewing equipment, and the like. For such purposes, these compounds are ordinarily employed in dilute aqueous solutions, usually in a concentration of about one percent or less by weight. In 'a given use, conventionally a minimum required strength of the particular quaternary ammonium compounds involved is recommended by the manufacturer, and in some instances Federal and State regulations may specify minimum effective concentrations. As is well known, during. use of these aqueous solutions their bactericidal potency may be diminished by dilution, or the quaternary ammonium compounds therein may interact with agents in ,such manner as to reduce or destroy the antibacterial activity. Consequently, in order to ensure against use of, solutions of inadequate strength, especially when repeated' use is involved, it is highly desirable to have available a simple means for determining routinely whether or not the effective quaternary ammonium concentration at any particular stage'of use is below the minimum standard. Various test procedures have been employed for this purpose, but some of these require skilled technicians and are thus unsuited to routine field use, and the avail able simple tests have one or more' undesirable features such as inconvenience,v unreliability, or production of results which are ditficult to interpret.

. fonated amides and amines, for instance sodium lauryl sulfate, sodium lauryl sulfonate, sodium myristyl sulfonate, di-(higher alkyl)alkali metal sulfosuccinates such' as the dioctyl sodium sulfosuccinates, sodium p-dodecylbenzenesulfonate, the sodium salt of N-methyl-N-(Z- sulfoethyD-oleic amide, sulfonated polyethanolamine, and the like. We particularly prefer sodium lauryl sulfate and the dioctyl sodium sulfosuccinates, for example bis- (2-ethylhexyl) sodium sulfosuccinate.

Our new chemical composition is readily prepared using conventional blending and mixing techniques, for example by homogeneously mixing together appropriate amounts of the anionic detergent, methyl orange, and bromophenol blue. The resulting reagent mixture can be used as such'or, if desired, suitable solvents or tabletting excipients are added before, during, or after the mixing operation.

When the new composition of this invention is added to an aqueous quaternary ammonium antibacterial solution, the anionic detergent component of our composition reacts stoichiometrically with the quaternary ammonium compound to form a non-ionized salt, and the mixture of dyes imparts to the solution a distinctive and characteristic color which is indicative of whether there is an excess of the anionic detergent or the quaternary ammonium compound in the reaction mixture. Thus, when there is an excess of the anionic detergent in the reaction mixture, the mixture of dyes colors the solution reddishbrown; and when there is an excess of the quaternary ammonium compound, the dyes interact with this excess to form a combination of complex compounds which colors the solution bluish-green. The distinction between point is sharp and the appearance of in-between shades which might confuse the observer in border-line cases It is therefore a primary object of this invention to provide simple and convenient means, for'determ'ining rapidly and reliably whether dilute aqueous solutions of an antibacterial quaternary ammonium compound contain an adequate effective concentration of the said compound. This obiect has been accomplished by affording in the present invention a novel chemical composition useful for distinguishing visually between solutions containing at least a predetermined level of concentrationoi a quaternary ammonium compound and solutions containing less than the predetermined level.

The new chemical composition of the instant inven tion for testing dilute aqueous solutions of quaternary ammonium compounds comprises a reagent mixture consisting essentially of methyl orange and bromophenol blue, in approximate weight ratio to each other of three is minimized.

It will be appreciated that it is the effective quaternary ammonium concentration in the solution which is measured by use of our composition, and there is no interference with the test procedure by any portion of the quaternary ammonium compound which may have'been removed from solution prior to the test, for instance by precipitation of solution in water-insoluble form by interaction withsoaps or anionic 'wetting agents.

The combined proportion by weight of the methyl orange and bromophenol blue constituents with respect to the total weight of the essential ingredients of the reagent mixture, namely methyl orange, bromophenol blue, and anionic detergent, is in the range from approximately 8 percent up to approximately 35 percent. A weight ratio of at least approximately three parts of methyl orange to one part of bromophenol blue is preferred, since this ,afiords the optimum sharpness of differentiation between the colors produced on each side of the end-point. Slight variations from the three to one ratio-can be made, however, without substantial adverse efiect on the color ditferentiation.

The proportion by weight of the anionic detergent constituent with respect to the total weight of the essential ingredients of the reagent mixture, namely methyl orange, bromophenol blue and anionic detergent, is in the range from approximately 92' percent down to approximately 65 percent. As will be appreciated from/the considerations set forth hereinbelow, the weight of the anionic detergent in any given quantity of our new composition must be accurately known. This object is of course readily attained by using a known weight of the anionic detergent, homogeneously distributing the anionic detergent throughout our composition, and determining the final weight of the homogeneously mixed composition, so that the weight of the anionic detergent per unit weight of the composition can be calculated.

The preferred ranges of proportions of the ingredients in the reagent mixture are 20-30 percent by combined weight of the two dyes and 80-70 percent of the anionic detergent.

When the molecular weight of the quaternary ammonium compound (or the mean molecular weight in the case of a mixture of quaternary ammonium compounds) is known, our new composition can be employed to determine whether more or less than a predetermined quan tity of the quaternary ammonium compound or compounds is present in a given volume of an aqueous solution. Thus, by adding a quantity of our new composition containing a known weight of the. anionic detergent to a test sample of the quaternary ammonium solution, it is rapidly and conveniently ascertained by observation of the resulting color whether the amount of quaternary ammonium compound in the test sample was above or below the amount necessary to interact stoichiometrically with the weight of the anionic detergent employed; and also of course, when a measured volume of the test sample is employed, it is ascertained at the same time by this test whether the concentration of the quaternary ammonium compond is above or below a calculated value. Further, by adding, to each of several samples of the quaternary ammonium solution having the same volume, quantities of our composition containing the anionic detergent in different, known weight for each sample, or alternatively and more conveniently by adding to each of several test samples of the quaternary ammonium solution having different, known volumes a quantity of our composition containing the anionic detergent in the same weight for each sample, a rapid approximation of the effective concentration of the quaternary ammonium compound can be made when appropriate selections of the weights of reagent and volumes of test samples have been made, as illustrated below in the examples. If a more exact determination of the concentration of the quaternary ammonium compound is desired, the quaternary ammonium solution can be titrated against an aqueous solution of our composition containing a known concentration of the anionic detergent.

For use in field tests of quarternary ammonium solutions to determine whether minimum concentration requirements are met, the use of tablets has a number of obvious advantages, and we therefore prefer to employ solid anionic detergents in making and using embodiments of our invention. The composition is advantageously tabletted in such manner that the weight of the anionic detergent component in one tablet is stoichiometrically equivalent to the amount of a given quaternary ammonium compound contained in a convenient selected volume of the solution to be tested when the solution is at the recommended minimum concentration level.

We have found that our invention is particularly adapted to the testing of aqueous solutions containing N-higher alkyl-N,N-di-lower alkyl-N-benzylammonium salts, particularly the higher alkyl-dimethyl-benzyl-ammonium halides, such as benzalkonium chloride, having a mean molecular weight of 357 and represented by the structural formula CHI CH! quaternary ammonium compound at the commonly used concentration of 200 p.p.m. For instance, when benzalkonium chloride solutions at a minimum recommended level of 200 p.p.m. are to be tested and the volume of the test sample is conveniently selected at 8 ml., we prefer that each tablet of our composition contain 1.29 mg. of sodium lauryl sulfate (molecular weight: 288), the amount of the latter required to react with the 1.60 mg. of the quaternary ammonium compound present in 8 ml. of a 200 p.p.m. solution.

Even when tablets of our composition are designed especially ,for use with a particular quarternary ammonium compound or for a given minimum use concentration of the quaternary ammonium compound, the same tablets can also be used conveniently for testing other quaternary ammonium compounds or for other minimum use concentrations by an appropriate selection of the volume of the test solution or by appropriate dilution of a measured volume of the test sample with a, known volume of water before the test is made, as illustrated in Examples 2 and 4 hereinbelow.

Our invention is illustrated by the following examples without, however, being limited thereto. In these examples, in each instance the term parts is employed to indicate parts by weight. 7

Example I A. 129 parts of sodium lauryl sulfate, 30.0 parts of methyl orange, and 10.0 parts of bromophenol blue were mixed and ground together thoroughly to form a uniformly blended homogeneous powder. The suitability of the composition thus obtained as a reagent was tested in the following manner. In wide variety of antibacterial applications, a minimum concentration of benzalkonium chloride in water of 0.02 percent, or 200 p.p.m. (parts per million) is recommended. Accordingly, standardized aqueous solutions containing respectively 100 p.p.m., 150 p.p.m., 200 p.p.m., and 250 p.p.m. of benzalkonium chloride were prepared. An ml. sample of each solution was'placed in respective test tubes, and to each of the four tubes there was added 16.9 mg. of the blended powder prepared as described. The tubes were agitated to facilitate solution, and in each instance all of the powder dissolved within a minute or less. The

color of each solution was then observed, as follows: in the two tubes containing the solutions in which the concentration of benzalkonium chloride was ppm. and p.p.m. respectively, the color was reddish-brown; at 200 ppm. of benzalkonium chloride, the color was brown; and at 250 ppm. of benzalkonium chloride, the color was bluish-green.

B. The reagent composition prepared as described in part A was also found to be fully satisfactory in field tests under actual conditions of use. Thus, an aqueous solution containing slightly more than 200' p.p.m. of benzalkonium chloride was used repeatedly as a sanitizing rinse for glassware... After each such rinsing operation, a sample of the solution was tested with the reagent composition described above in partA. The color of the resulting test solutions was bluish-green in each successive test until a reddish-brown test solution indicated that the benzalkonium chloride concentration had dropped below the recommended safe minimum of 200 p.p.m.

a,979,4es

129 parts of sodium lauryl su1fate, 30 parts of methyl orange, parts of bromophenol blue, 14,945 parts of lactose, 800 parts of starch, and 80 parts of magnesium stearate were mixed and ground together to produce a uniformly blended homogeneous, powder. This powder was then tabletted to produce tablets weighing 160 mg. each which contained, as the essential active ingredients thereof, 1.29 mg. of sodium lauryl sulfate, 0.3 mg. of methyl orange, and 0.1 mg. of bromophenol blue per tablet.

We found that these tablets were especially convenient for use in field tests of aqueous quaternary ammonium solutions. Thus, by placing one of these tablets in an 8 ml. sample of an aqueous solution of benzalkonium chloride, there was obtained a very rapid indication of whether the solution was at the recommended level of 200 p.p.m. or above, as evidenced by a bluish-green color, or was below the level of 200 p.p.m., as evidenced by a reddish-brown color. When desired, the testing of the solutions which had a reddish-brown color was readily extended to obtain an estimate of how much below the recommended minimum the concentration of benzalkonium chloride was. This was done by adding further increments of the solution being tested. Thus, if the color shifted from reddish-brown to bluish-green on addition of 1 ml. more of the solution, this indicated a benzalkonium chloride concentration of at least 178 p.p.m., and of course below 200 p.p.m. If the color did not shift after addition of the 1 ml. portion of solution, but did shift to bluish-green after adding a second 1 ml. portion of solution, this indicated a benzalkonium chloride concentration of at least 160 p.p.m., and of course below 175 p.p.m. The testing of solutions below the 160 p.p.m. level can be extended as desired by addition of further increments of solution until a shift in color from reddish-brown to bluish-green is obtained.

For certain applications, the recommended concentration of benzalkonium chloride is greater than 200 p.p.m. These stronger solutions were tested with the above tablets by diluting the solution with the amount of water calculated to reduce the benzalkonium chloride to 200 p.p.m., then testing an 8 ml. sample of the diluted solution with one reagent table as above described, and finally multiplying the indicated concentration by the dilution factor to obtain the concentration of the original solution. For example, one ounce of a benzalkonium chloride solution which should be used at a minimum concentration of 1600 p.p.m. was diluted with seven ounces of water, the reagent tablet was added to an 8 ml. sample of the resulting solution, and the found concentration value was multiplied by eight to obtain the concentration of the original solution.

Example 3 To prepare a composition like that described in part A of Example 1 but containing an equivalent amount of dioctyl sodium sulfosuccinate (molecular weight 444) as the anionic detergent, the 129 parts of sodium lauryl sul the 8 ml. sample used for benzalkonium chloride, so that otherwise the testing procedure and the reading and interpretation of results could then be carried out exactly as in the case of benzalkonium chloride described above. The calculation is as follows.

Molecular weight of QAC v357 Thus, in testing solutions of lauryl-dimethyl-benzyl-ammonium chloride, having a molecular weight of 339.5, to determine deviations from a recommended use level of 200 p.p.m., the volume of test sample employed was 8=the test volume of QAC 430.5 rgg XS-QJ ml.

Example 5 Following the procedure of Example 2, but using 404 parts of sodium lauryl sulfate instead of 129 parts, there 7 were obtained tablets weighing about 163 mg. each which mg. of methyl orange, and 0.1 mg. of bromophenol blue per tablet.

Example 4 The 160 mg. tablets described in Example 2 were also used conveniently and satisfactorily to test solutions of quaternaryammonium compounds other than benzalkocontained, as the essential active ingredients thereof, 4.04 mg. of sodium lauryl sulfate, 0.3 mg. of methyl orange, and 0.1 mg. of bromophenol blue per tablet. Each of these tablets had the calculated amount of sodium lauryl sulfate to interact stoichiometrically with the amount of benzalkonium chloride contained in 5 m1. of an aqueous solution containing 1000 p.p.m. of the quaternary. These tablets were found to be highly useful for the testing of 5 ml. samples of aqueous benzalkonium chloride solutions for deviation from recommended use concentration of 1000 p.p.m.

We claim:

1. A chemical composition for testing the concentration of dilute aqueous solutions of quaternary ammonium compounds which comprises a reagent mixture homogeneously distributed in said composition and consisting essentially of methyl orange and bromophenol blue, in approximate weight ratio to each other of three to one respectively,and an anionic detergent of the group consisting of water-soluble synthetic organic sulfate and sulfonate anionic detergents, the combined percentage by weight of the methyl orange and the bromophenol blue in said reagent mixture being in the approximate range 8-35 and the percentage by weight of the said anionic detergent in the reagent mixture being in the approximate range 92-65.

2. A chemical composition for testing the concentration of dilute aqueous solutions of quaternary ammonium compounds which comprises a reagent mixture homogeneously distributed in said composition and consisting essentially of methyl orange and bromophenol blue, in approximate weight ratio to each other of three to one respectively, and sodium lauryl sulfate, the combined percentage by weight of the methyl orange and the bromophenol blue in said reagent mixture being in the approximate range 8-35 and the percentage by weight of the sodium lauryl sulfate in the reagent mixture being in the approximate range 92-65.

3. A chemical composition for testing the concentra tion of dilute aqueous solutions of quaternary ammonium compounds which comprises a reagent mixture homogeneously distributed in said composition and consisting essentially of methyl orange and bromophenol blue, in approximate weight ratio to each other of three to one respectively, and sodium lauryl sulfate, the combined percentage by weight of the methyl orange and the bromophenol blue in said reagent mixture being in the approximate range 20-30 and the percentage by weight of the I sodium lauryl sulfate in the reagent mixture being in the approximate range 80-70.

4. A chemical composition for testing the concentraapproximate weight ratio to each other of three to one respectively, and dioctyl sodium sulfosuccinate,- the combined percentage by weight of the methyl orange and the bromophenol blue in said reagent mixture being in the approximate range 8-35 and the percentage by weight of the dioctyl sodium sulfosuccinate in the reagent mixture. being in the approximate range 92-65.

5. A chemical composition for testing the concentration of dilute aqueous solutions of quaternary ammonium compounds which comprises a reagent mixture homogeneously distributed in said composition and consisting essentially of approximately one part by weight of bromophenol blue, approximately three parts by weight of methylorange, and approximately thirteen parts by weight of sodium lauryl sulfate.

6. A chemical composition for testing the concentration of dilute aqueous solutions of quaternary ammonium compounds which comprises a reagent mixture homogeneously distributed in said composition and consisting essentially of approximately one part by weight of bromophenol blue, approximately three parts by weight of methyl orange, and approximately forty parts by weight of sodium lauryl sulfate.

7. A reagent tablet for testing the concentration of dilute aqueous solutions of quaternary ammonium compounds comprising in dry, homogeneous admixture the following ingredients: 1.29 mg. of sodium lauryl sulfate; approximately 0.1 mg. of bromophenol blue; approximately 0.3 mg. of methyl orange; approximately mg. of lactose; approximately 8 mg. of starch; and approximately 0.8 mg. of magnesium stearate.

8. A reagent tablet for testing the concentration of dilute aqueous solutions of quaternary ammonium compounds comprising in dry, homogeneous admixture the following ingredients: 4.04 mg. of sodium lauryl sulfate; approximately 0.1 mg. of bromophenol blue; approxi mately 0.3 mg. of methyl orange; approixmately 150 mg.

of lactose; approximately 8 mg. of starch; and approximately 0.8 mg. of magnesium stearate.

References Cited in the file of this patent UNITED STATES PATENTS Conklin June 10, 1952 OTHER REFERENCES

Claims (1)

1. A CHEMICAL COMPOSITION FOR TESTING THE CONCENTRATION OF DILUTE AQUEOUS SOLUTIONS OF QUATERNARY AMMONIUM COMPOUNDS WHICH COMPRISES A REAGENT MIXTURE HOMOGENEOUSLY DISTRIBUTED IN SAID COMPOSITION AND CONSISTING ESSENTIALLY OF METHYL ORANGE AND BROMOPHENOL BLUE, IN APPROXIMATE WEIGHT RATIO TO EACH OTHER OF THREE TO ONE RESPECTIVELY, AND AN ANIONIC DETERGENT OF THE GROUP CONSISTING OF WATER-SOLUBLE SYNTHETIC ORGANIC SULFATE AND SULFONATE ANIONIC DETERGENTS, THE COMBINED PERCENTAGE BY WEIGHT OF THE METHYL ORANGE AND THE BROMOPHENOL BLUE IN SAID REAGENT MIXTURE BEING IN THE APPROXIMATE RANGE 8-35 AND THE PERCENTAGE BY WEIGHT OF THE SAID ANIONIC DETERGENT IN THE REAGENT MIXTURE BEING IN THE APPROXIMATE RANGE 92-65.