AU616727B2 - Systems for determining cyanuric acid in water - Google Patents

Description

61 6 7 2 7 616727 PI DATE 01/08/89

PCT

APPLN- ID 294i35 89 AOJP DATE 31/08/89 PCT NUMBER PCT/US88/04627 INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATI .OOPERATION TREATY (PCT) (51) International Patent Classification 4 G01N 21/78 (11) International Publication Number: Al (43) International Publication Date: WO 89/ 06355 13 July 1989 (13.07.89)

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(21) International Application Number: PCT/US88/04627 (22) International Filing Date: 22 December 1988 (22.12.88) (81) Designated States: AT (European patent), AU, BE (European patent), CH (European patent), DE (European patent), FR (European patent), GB (European patent), IT (European patent), JP, LU (European patent), NL (European patent), SE (European patent).

Published With international search report.

(31) Priority Application Number: 138,045 (32) Priority Date: (33) Priority Country: 28 December 1987 (28.12.87) (71)Applicant: ENVIRONMENTAL TEST SYSTEMS, INC. [US/US]; 23575 County Road 106, Elkhart, IN 46514 (US).

(72) Inventor: RUPE, Chauncey, Orvis 27077 Oakland Hill Drive, Elkhart, IN 46517 (US).

(74) Agent: STEPHENSON, Harry, Environmental Test Systems, Inc., P.O. Box 4659, Elkhart, IN 46514 (US).

(54) Title: SYSTEMS FOR DETERMINING CYANURIC ACID IN WATER (57) Abstract A colorimetric test reagent composition is presented for determining the amount of cyanuric acid in water. Cyanuric acid is added to outdoor swimming pool water to stabilize the chlorine added as a sanitizer. Basically the test composition utilizes melamine and an indicator material which responds to a change in pH of the test environment caused by the action of cyanuric acid on the reagent composition. Preferably the test composition is incorporated in a porous matrix which results in a convenient solid state test device.

i II WO 89/06355 PCT/US88/04627 SYSTEMS FOR DETERMINING CYANURIC ACID IN WATER FIELD OF THE INVENTION The present invention relates to a test reagent composition for colorimetrically determining the quantity of cyanuric acid in water. More particularly, the invention relates to a test composition which can be incorporated into a matrix such as paper which when contacted with an aqueous fluid containing cyanuric acid will result in the formation of a color which is proportional to the quantity of cyanuric acid present.

BACKGROUND OF THE INVENTION As the number of swimming pools and spas increases, the need for effective tools to monitor and control pool water chemistry and especially sanitizer levels becomes more and more important. This is especially true in pools used by the public where the bather concentration is high and the threat of contagious diseases is always present.

In order to control the harmful microorganism population of pools, it has been found over the years that chlorine is the most effective and economical sanitizer. However, as popular as chlorine is, it nevertheless has certain drawbacks which must be considered. A particularly serious problem associated with the use of chlcrine ir,

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WO 89/06355 PCT/US88/0462" S2 i outdoor pools is that it tends to be destroyed by sunlight.

In this regard it has been found that the addition of cyanuric acid (2,4,6-trihydroxy-l,3,5-triazine) to the outdoor pool water can be effective as an extender or stabilizer for chlorine. However, the concentration must i be rather carefully adjusted since too little obviously i is ineffective as a stabilizer for the chlorine while too i much can dramatically slow down the rate at which i microorganisms are destroyed by the chlorine. It has been found that the effective concentration of cyanuric acid lies between 40 and 120 parts per million (ppm).

In order to maintain the effectiveness of the I cyanuric acid in the swimming pool, it is necessary to Smeasure the concentration thereof using a test device or !j concentration measuring system. The current test most V commonly used in the swimming pool industry involves the Smelamine turbidimetric methodology. In this scheme, melamine is added to a sample of the pool water which in the presence of cyanuric acid causes the formation of a finely dispersed precipitate. The turbidity created by this precipitate formation is proportional to the amount of cyanuric acid present. By measuring this turbidity using visual or instrumental schemes, an estimation of the concentration of cyanuric acid can be obtained. This test however is not completely acceptable since turbidimetric methods tend in general to be unreliable in that other factors can cause turbidity and precipitates are obviously less homogenous that solutions.

For this reason, attempts have been made over the years to replace the turbidimetric analytical procedures with colorimetric methodologies. To date, an acceptable, commercially available colorimetric method fcr determining cyanuric acid does not exist.

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WO 89/06355 PCT/US88/04627 DESCRIPTION OF THE PRIOR ART U.S. Patent No. 4,039,284 discloses and claims a formulation for the colorimetric determination of cyanuric acid comprising a thymolsulfonphthalein compound, monoethanolamine and a stilbene compound.

Regardless of its suggested efficacy, it appears that there are no commercially available products based on this technology.

Aside from the above patent, very little literature exists relative to the interaction of cyanuric acid with other compounds to form colored compounds. Veneable, C.

and Moore, J. Am. Chem. Soc. 39, 1750, 1917 discloses that cyanuric acid will react with certain metals such as copper to produce colored compounds. However, the reaction must take place under severe alkaline conditions and heat which obviously is not amenable to a field test system.

All other prior art literature relates to colorless turbidimetric reactions between cyanuric acid and other compounds which art has no relevance here.

SUMMARY OF THE INVENTION It has now been unexpectedly found that by using melamine, an appropriate pH indicator material and adjusting the pH of the test composition to within a designated range, a simple to use and effective colorimetric cyanuric acid test system can be devised.

Basically, this invention involves the utilization of melamine and a pH indicator, which composition, when contacted with cyanuric acid, causes a shift in the pH of the test system and in effect creates a color chance which is proportional to the amount of cyanuric acid in the fluid being tested. Although the melamine'cvanuric acid precipitate can be removed to more easily an:.

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WO 89/06355 PCT/US88/04627 accurately determine the color produced when the composition is used as a liquid format, or other means can be employed to read the color formed, it is preferable to incorporate the composition in a solid state matrix such as paper. In this format the interference due to the melamine/cyanuric acid precipitate is eliminated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the basic reagent composition of the present invention comprises melamine and a pH indicator, two slightly different approaches can be utilized to achieve a useful product. Both approaches involve the adjustment of the pH of the test composition prior to contacting the composition with the fluid being tested.

~i In the first approach, the pH of the composition is SIadjusted to within a range of from about pH 5 to a pH of less than about 7, whereby contact of the composition Iwith cyanuric acid in the fluid being tested results in I: neutralization and a corresponding drop in the pH of the test fluid, the pH indicator being responsive to such pH drop to give a visual color change proportional to the amount of cyanuric acid present. In the second approach, the pH of the composition is adjusted to within a range of from about 7 to about 8. In such an approach, the i1 melamine in the reagent composition reacts with cyanuric acid present to cause a change in the equalibrium between _f the enol and the keto forms of cyanuric acid, resulting in a higher or more basic pH in the test environment, which in the presence of an appropriate pH indicator likewise causes a perceptible color change indicative of the amount of cyanuric acid present in the fluid being tested.

In preparing the compositions of the present invention, consideration must be given to the seleczict p S WO 89/06355 PCT/US88/04627 of indicator materials and the concentration of melamine in the test composition. As previously indicated, the test compositions should be adjusted to a pH of either from about 5 to about 7 or from about 7 to about 8. In view of this, the indicator must accordingly be selected to change color when the pH of the test environment either increases or decreases. Indicators such as methyl red, phenol red, thymol blue, bromthymol blue, cresol red, metacresol purple and mixtures thereof may be selected as color forming agents.

The concentration of melamine (cyanurotriamide) in the reagent mixture should be set at from about 0.02 g/100 ml to about 0.5 g/100 ml. The melamine concentrationi set to be in excess of the anticipated concentration of cyanuric acid being detected Sbut such that the pH change caused by contact of the reagent composition with the cyanuric acid is hindered.

It has also unexpectedly been found that the utilization of a thickening agent such polystyrene sulfonic acid or Gantrex is advantageous in that the color response of the test composition to cyanuric is enhanced. It is believed that these materials localize the color, making the color response more easily detected.

SAs previously noted, it is preferable to incorporate the reagent composition into a solid state matrix sc that the formation of precipitate does not hinder in the estimation of the color change. Examples of matrix materials which can be utilized are filter paper, glass fibers, cellulosic materials, synthetic fibers, polymers, particulate inorganic materials, and so forth. The matrix must however be impervious to and not react with the fluid being tested and must be reasonably hydrophili: and porous so that the fluid being tested wets the matrix and the analyce contained therein, i. e. cvanuric ©Z

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L r T_ I imi*c-~-1^--xr WO 89/06355 PCT/US88/0462- 6 reacts with the incorporated reagent composition.

A particularly advantageous use of the solid state test devices described next above is in conjunction with an instrumental read out means. This can be accomplished by using a reflectance color measuring device wherein the color of the reagent matrix is measured and interpreted to give a readout in concontration of cyanuric acid in the fluid being tested.

EXAMPLES

The following Examples are illustrative of the present invention.

i Example 1.

Deionized Water 95.0 ml.

Polystyrene Sulfonic Acid (Na Salt) 0.5 g.

SMelamine 0.1 g.

j Methyl Red 0.1% in dilute NaOH 0.5 ml.

K The polystyrene sulfonic acid salt was dissolved in the deionized water with stirring. The melamine was added and the stirring continued until the melamine dissolved. The methyl red was added and the pH of the solution adjusted to 5.25 with HC1. E D 205 filter paper was dipped into the reagent solution and dried in a hot air tunnel. The resulting dried paper was light pink in color.

Standard solutions of cyanuric acid in swimming pool water were prepared and the following colors obtained by immersing the reagent paper into such standard sclutions and immediately removing the paper from the water: WO 89/06355 PCT/US88/04627 Cvanuric Acid Conc. (ppm) 0 100 200 Color Orange Pink Red Dark Red Example 2 Deionized wacer Methyl Red 0.1% in dilute NaOH Gantrez AN119 Melamine 95 ml.

3 ml.

0.1 g.

0.2 g.

The above ingredients were combined as in Example 1, except that the solution was heated to solubilize the Gantrez. The solution was cooled and the pH adjusted to 5.75 with HC1. Reagent papers were prepared as in Example 1 and when contacted with tap water having various concentrations of cyanuric added thereto gave the following results: 'ii

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Cvanuric Acid Conc. (ppm) 0 100 250 500 Color Orange Pink Light Red Red Dark Red Example 3 Deionized water Polyvinyl alcohol Surfactant (Igepal CO-660) 0.1% Phenol red 0.1% (Na salt) Thymol blue 0.1% (Na salt) Melamine 88 ml.

1.5 g.

10 ml.

5 ml.

7 ml 0.1 g.

The above composition was prepared essentil- as i:.

L_ I- I -9C -~ra lil-rrl 7 WO 89/06355 PCT/US88/046r' Example 2. The pH of the composition was adjusted to and the composition impregnated into filter paper and dried. The dried paper was yellow in appearance.

Test strips made from this paper gave the following results when dipped into and immediately removed from tap water containing the indicated amounts of cyanuric acid: Cyanuric Acid Conc. (ppm) 0 100 150 200 Color Orange Tangerine Red Violet Purple Example 4 Deionized water Polystyrene sulfonic acid (Na salt) Phenol red 0.1% (Na salt) Thymol blue 0.1% (Na salt) Melamine 88 ml.

0.3 g.

5 ml.

7 ml.

0.1 g.

The reagent composition was prepared and incorporated into filter paper essentially as described in Example 3. The following results were obtained when test strips were contacted with tap water containing the indicated amounts of cyanuric acid.

Cyanuric Acid Conc. (ppm) 160 320 Color Orange Pink Red Violet Purple

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Claims (12)

1. A reagent composition for the determination of cyanuric acid in water comprising melamine and an indicator which changes colour in response to a change in the pH of the water due to the presence of cyanuric acid, the proportion of melamine being sufficient to effect a pH change in the water containing the cyanuric acid, with said pH change being of a value and magnitude sufficient to be visually indicated by said indicator.

2. A composition as claimed in Claim 1 wherein the pH of the composition is adjusted to a range of from about 5 to about 7.

3. A composition as claimed in Claim 1 wherein the pH of the composition is adjusted to a range of from about 7 to about 8.

4. A composition as claimed in any one of the preceding claims wherein the indicator is selected from the group consisting of methyl red, phenol red, thymol blue, cresol red, metacresol purple, and mixtures thereof.

5. A composition as claimed in any one of the preceding S claims wherein the concentration of melamine is greater than the anticipated concentration of cyanuric acid expected in the water containing the cyanuric acid but is insufficient to hinder the pH change caused by contact of the reagent composition with the cyanuric acid.

6. A solid state test device for estimating the amount of cyanuric acid in water comprising a matrix and the dried residue of a reagent composition consisting essentially of melamine and an indicator which changes colour in response to a change in the pH of the environment in the matrix when the matrix is contacted with an aqueous solution of cyanuric acid, the proportion of melamine being sufficient to effect a pH change in the water I- I a~--------armaraura~ containing the cyanuric acid, with said pH change being of a value and magnitude sufficient to be visually indicated by said indicator.

7. A test device as claimed in Claim 6 wherein the reagent composition additionally comprises a thickening agent selected from the group consisting of polystyrene sulphonic acid and gantrez.

8. A test device as claimed in Claim 6 or 7 wherein the pH of the composition is adjusted to a range of from about 5 to about 7 prior to being incorporated into the matrix.

9. A test device claimed in Claim 6 or 7 wherein the pH of the composition is adjusted to a range of from about 7 to about 8 prior to being incorporated into the matrix.

A test device as claimed in any one of Claims 6 to 9 k5 wherein the concentration of melamine in the reagent composition S: is between 0.02 g/100ml and 0.5 g/100ml.

11. A solid state test device as claimed in any one of Claims 6 to 10 wherein the indicator is selected from the group consisting of methyl red, phenol red, thymol blue, cresol red, J 2'"20 metacresol purple, and mixtures thereof. i

12. A reagent composition substantially as herein before described in the Examples. jDated this 8th day of August, 1991 PATENT ATTORNEY SERVICES Attorneys for ENVIRONMENTAL TEST SYSTMES, INC. ,RON INTERNATIONAL SEARCH REPORT In ternaliona I An~ D Ir 1' 1, P T1 t 1. CLASSIFICATION OF SUBJECT MATTER se,crri ciasstr'c'sn, Stmr"orS ap OL 1 Accoiorro Ic International Paler.! Cfasstrcarrn IIPCr or !o bolt ,t ;orns Ciass,rcat~o-' ao IPC TPC(4) 21/78 U.S. CL.: 436/106 11 FIELDS SEARCHED Minimumr Dccrarrentalro' Searcr,ed Classification Systemr Ciassircalion Symoo~s U.S. 436/106,56 Documentation Searched other than Minimumn Documentation to the Extenut that such Documents are Included in tihe Fields SearchedE Ill. DOCUMENTS CONSIDERED TO BE RELEVANT 9 Category Citalc, of Docun-e.nt. -rt rncdcat~c,'. vwr,cri: adrorretrl. c& tr- reii'~a" rassaq. R, C a Y US, A, 4,039,284 (MANCINI) 1-8 02 August 1977 See columns 3 and Y US, A, 4,670,218 (GANTZER et al) 6-8 02 June 1987 See column 7. Y US, A, 4,673,513 (POWELL) 16 June 1987 See column 3. A JP, B, 7-005595 (SIT) 23 February 1970 A US, A, 4,162,897 (CAPUANO) 31 July 1979. Zi US, A, 4,613,575 (WESTRUP, et al,) 23 September 1986 A. THE MERK INDEX, TENTH EDITION 1933, pages 5632, 5010, 2691, 2692. Special catesories of cited documents "T later document out) sired: cfie' ti-e ,'rte'ratora r, c 00ue! 00 -Et ge~c' slar- cl at, s r- C'r''r a I'" consioerea to 'eof part cuiafr elevance c in -Cnertor c earl e' doc.'tL,-et o~ ui-sr a on cite' lre inte'nat 0a 'i OC'CU-t c' Da'! ir w Z filing oate canrc- oe co's op-aZ; 'rC~f or cc -z'o cc's z' document vvrcl- ma. i'ro,. oubiS On or't, clam-s c, inaoie c- er'r .C ate shct is c tao to estatt 5' t'a daco'ote c' c-'r occ o o I C)5. t-r c;i -r a citation or otnrie special reason las soecifrec ccnrrot oe consoea'eo tOC in,0 a' nlrel' .E sIar document ref erin to a' oral o'sclos,'e, use e,iro to- c' oo~*rn !s co- c -rza. c'ra ,'0 othe' means rrE-'s CGc-'-ac' C' O- a ca"B'S' ooumne,'.r~r safl-r' c re 'te-s''i C cc z v' E" later Ira' l's- oat ca -E 00 r" nneca' c' I' Sa tVl IV. CERTIFICATION Date of Ire Acl~a Co-set-. o' o' tr; l':ern! ,n2: S DptE o' tMa, ia s'er March 1989' 20 APR I9 lnternatc~a Sea'i.'A"z' S "A -I 4 Fo~m p1_7 S47 1 lswcc L