Detecting organic contaminants

Abstract

A composition including at least one strong oxidant, a color indicating system, and one or more thickening agents is provided. A method of using the composition on an aqueous basis includes detecting any contaminants on a surface with organic substances by visual control after superficially applying the composition to the surface. The composition is not flowable for a predefined period after the superficial application due to the effect of the thickening agent. The one or more thickening agents are stable in the composition during the predefined period, and are selected from synthetic sheet silicates, pyrogenic silicic acid, fatty alkyl (benzene) sulfates, sulfonates, carboxylates, phosphates and aminoxides and mixtures thereof. A color change in the composition applied to the surface during the predefined period indicates that organic contaminants are present on a portion of the surface.

Claims

1. A method of using a composition on an aqueous basis comprising a) at least one strong oxidant, b) a color indicating system, and c) one or more thickening agents, the method comprising: superficially applying the composition to a surface with organic substances; and detecting any contaminants on the surface by visual control after the superficial application, wherein the composition is not flowable for a predefined period after the superficial application due to an effect of the one or more thickening agents, wherein the one or more thickening agents are stable in the composition during the predefined period, wherein the one or more thickening agents are selected from the group consisting of synthetic sheet silicates, pyrogenic silicic acid, fatty alkyl (benzene) sulfates, sulfonates, carboxylates, phosphates and aminoxides and mixtures thereof, and wherein a color change in the composition superficially applied to the surface during the predefined period indicates organic contaminants being present on a portion of the surface, and wherein the one or more thickening agents have a stabilizing effect on the at least one strong oxidant, and wherein said one or more thickening agents produces a stabilizing effect on the color change when said composition reacts with any contaminants in the composition, such that the occurrence of false-positive detection results is reduced.

2. The method of claim 1, wherein the composition is applied to a vertical or downwards facing surface.

3. The method of claim 1, wherein the predefined period is at least 10 seconds.

4. The method of claim 1, wherein the at least one strong oxidant is selected from the group consisting of permanganates, peroxydisulfates, salts of halogen oxoacids and mixtures thereof.

5. The method of claim 1, wherein the at least one strong oxidant comprises permanganate.

6. The method of claim 5, wherein the at least one strong oxidant further comprises at least one additional oxidant whose oxidation potential exceeds that of permanganate.

7. The method of claim 6, wherein the at least one additional oxidant is selected from the group consisting of peroxydisulfate and hypochlorite.

8. The method of claim 5, wherein the permanganate at the same time serves as a color indicator.

9. The method of claim 8, wherein the permanganate is contained in the composition in an amount of 0.1 to 0.6 g/L or 0.01 to 0.06% by weight.

10. The method of claim 9, wherein the permanganate is contained in the composition in an amount of 0.15 to 0.4 g/L or 0.015 to 0.04% by weight.

11. The method of claim 6, wherein the at least one additional oxidant is contained in the composition in an amount that is at least 10 times, 20 times, or 30 times the amount of permanganate, or at a concentration of at least 0.3 g/L.

12. The method of claim 1, wherein the one or more organic thickening agents are contained in the composition in a total amount of not more than 3% by weight.

13. The method of claim 1, wherein the composition further contains one or more adjuvants selected from the group consisting of pH regulators, hardness stabilizers and biocides.

14. The method of claim 1, wherein the surface is at the same time cleaned by superficially applying the composition.

15. The method of claim 1, wherein the visual control is performed computer-assisted by conducting digital color comparisons.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawing. For the purpose of illustrating the invention, there is shown in the drawing, an embodiment which is presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.

(2) In the drawing:

(3) The FIGURE is a photograph showing the results of a detection test of Example 40, according to an embodiment of the present invention, on a deliberately contaminated, vertical stainless-steel surface.

DETAILED DESCRIPTION OF THE INVENTION

(4) In the following, the present invention will now be described in more detail based on specific, non-limiting exemplary embodiments and comparative examples.

EXAMPLES

(5) Compositions for use in a method according to the present invention were prepared by dissolving potassium permanganate and a second strong oxidant selected from sodium hypochlorite (HC) and sodium peroxydisulfate (PS) together with one commercially available, inorganic or organic thickening agent (TA) each in the following proportions in water by stirring:

(6) TABLE-US-00001 KMnO.sub.4 0.01 g HC or PS 0.12 g NaOH 0.04 g TA 0.5 to 7 g water to 100 ml

Examples 1 Through 38 and Comparative Examples 1 Through 82Stability Tests

(7) Solutions prepared as described above were measured in a photoreader while examining whether the ratio between Mn(VII) and Mn(VI) was above 75% over a period of 20 min. Afterwards, 0.5 ml of a 0.1% glucose solution were added, and the color gradient was observed over a period of 10 min. A composition was regarded as stable when the Mn(VII)/Mn(VI) ratio was above 75% and a clear color change from purple to green occurred.

(8) The exact amounts of the respective thickening agents are given in Tables 1 and 2 below, together with the evaluation + for stable or for not stable, where organic thickening agents were tested in Examples 1 through 34 and Comparative Examples 1 through 72 (i.e., CE 1-72) (Table 1) and inorganic thickening agents were tested in Examples 35 through 38 and Comparative Examples 73 through 82 (i.e., CE 73-82) (Table 2). In the tables, the commercial names, the manufacturer and, if known, the active substance or at least its substance class are given in the tables. However, the other adjuvant materials of the commercial products were completely unknown in a vast majority of cases, because such manufacturer information was mostly missing.

(9) This is also why no generally applicable statements can be made with regard to the suitability of commercially available products in the present invention. Nevertheless, a detailed interpretation of the achieved results can be found below the tables.

(10) Most commercial names of thickening agents are branded. Nevertheless, marking every single one of them with or in the tables was omitted for convenience purposes.

(11) TABLE-US-00002 TABLE 1 Organic Thickening Agents Thickener Example # Thickening Agent Manufacturer Active Substance Ox. 2 (wt. %) Rating Example 1 Dowfax 2A1 Dow branched C12 alkyl cliphenyloxide disulfonate PS 2 + CE 1 -- -- -- -- 7 Example 2 -- -- -- HC 2 + CE 2 -- -- -- -- 7 Example 3 Dowfax 3B2 -- linear C10 alkyl diphenyl sulfonate PS 2 + Example 4 -- -- -- -- 7 + Example 5 -- -- -- HC 2 + Example 6 -- -- -- -- 7 + CE 3 Methocel 267 -- cellulose ether PS 1 CE 4 -- -- -- HC 1 CE 5 Rhodopol 23 Rhodia xanthane gum PS 1 CE 6 -- -- -- HC 1 Example 7 Genarninox LA Clariant lauryl dimethyl aminoxide HC 2 + CE 7 -- -- -- -- 7 Example 8 Genaminox CSL -- coconut alkyl dimethyl aminoxide PS 2 + CE 8 -- -- -- -- 7 CE 9 -- -- -- HC 2 CE 10 -- -- -- -- 7 CE 11 Genamin CC 302D -- coconut alkyl dimethyl amine HC 0.5 CE 12 -- -- -- -- 3 CE 13 Sandoperm CAN -- amino-modified silicone elastomer -- 0.5 CE 14 -- -- -- -- 3 Example 9 Akyposoft 100 BCEC KAO polyoxyethylene-(11) lauryl ether carboxylate-Na PS 2 + Example 10 -- -- -- -- 7 + CE 15 -- -- -- HC 2 CE 16 -- -- -- -- 7 Example 11 Oxidet DM-20 -- dimethyl lauraminoxide PS 2 + Example 12 -- -- -- -- 7 + Example 13 -- -- -- HC 2 + Example 14 -- -- -- -- 7 + Example 15 Oxidet L-75 C -- coconut alkyl amidopropylaminoxide PS 2 + CE 17 -- -- -- -- 7 CE 18 -- -- -- HC 2 CE 19 -- -- -- -- 7 CE 20 Amidet A-15 -- polyoxyethylene-(2) tridecyl ether carboxylic acid HC 0.5 ethanolamide CE 21 -- -- -- -- 3 CE 22 Betadet HR-50K -- coconut alkyl amido propyl betaine HC 2 CE 23 -- -- -- -- 7 CE 24 Betadet S-20 -- lauryl hydroxysulfobetaine PS 2 CE 25 -- -- -- -- 7 CE 26 -- -- -- HC 2 CE 27 -- -- -- -- 7 CE 28 Betadet SHR -- coconut alkyl amidopropyl hydroxysulfobetaine PS 2 CE 29 -- -- -- -- 7 CE 30 -- -- -- HC 2 CE 31 -- -- -- -- 7 Example 16 Quartamin AB -- behenyl trimethyl ammonium chloride HC 2 + Example 17 -- -- -- -- 7 + Example 18 Emal 30E -- sodium lauryl sulfate PS 0.5 + Example 19 -- -- -- -- 2 + CE 32 -- -- -- -- 3 CE 33 -- -- -- -- 7 CE 34 -- -- -- HC 2 CE 35 -- -- -- -- 7 CE 36 Emal 10N -- sodium lauryl sulfate HC 0.5 CE 37 -- -- -- -- 3 CE 38 SerCEo AM 1010 Elementis coconut alkyl aminopropionate HC 0.5 CE 39 -- -- -- -- 3 CE 40 Serdox NBS 6.6/90 -- polyoxyethylene-(6,6)-C.sub.9-11-alkylether PS 2 CE 41 -- -- -- -- 7 CE 42 -- -- -- HC 2 CE 43 -- -- -- -- 7 CE 44 Serdox NBSQ 5/5 -- polyoxyethylene-(5)-polyoxypropylene-(5)-C.sub.9-11- PS 2 alkylether CE 45 -- -- -- -- 7 CE 46 Sermul EA 266 -- polyoxyethylene-(15)-tridecylethersulfate-Na PS 2 CE 47 -- -- -- -- 7 CE 48 -- -- -- HC 2 CE 49 -- -- -- -- 7 CE 50 SerCEo X13 90 -- mixture of (quat. ammonium-) kationic and anionic PS 2 surfactants CE 51 -- -- -- -- 7 CE 52 SerCEo XB 90 - mixture of (quat. ammonium-) kationic and anionic HC 2 surfactants CE 53 -- -- -- -- 7 CE 54 SerCEo Q 8010 -- Lauryl amidopropyl trimethylammonium PS 2 methylsulfate CE 55 -- -- -- -- 7 CE 56 -- -- -- HC 2 CE 57 -- -- -- -- 7 Example 20 Crodasinic LS30 NP Croda sodium fatty acyl sarcosinate PS 2 + CE 58 -- -- -- -- 7 Example 21 -- -- -- HC 2 + CE 59 -- -- -- -- 7 Example 22 Multitrope 1214 -- fatty alkyl phosphate ester HC 0.5 + Example 23 -- -- -- -- 3 + Example 24 Poro TS 430X Poro PS 2 + Example 25 -- -- -- -- 7 + CE 60 -- -- -- HC 2 CE 61 -- -- -- -- 7 Example 26 Hoesch L29 J. Hoesch polyoxyethylene-(3)-laurylethersulfosuccinate-2Na HC 0.5 + CE62 -- -- -- -- 3 Example 27 Plurafac LF 221 BASF polyalkylenoxide fatty alkylether PS 2 + CE 63 -- -- -- -- 7 CE 64 -- -- -- HC 2 CE 65 -- -- -- -- 7 CE 66 Lutensol GD 70 -- fatty alkylpolyglucosicle HC 2 CE 67 -- -- -- -- 7 Example 28 Lutensol TO 89 -- polyoxyethylene-C.sub.13-isoalkylether PS 2 + Example 29 -- -- -- -- 7 + CE 68 -- -- -- HC 2 CE 69 -- -- -- -- 7 Example 30 Glanapon DA 363 Bussetti modified silicone PS 0.5 + CE 70 -- -- -- -- 3 CE 71 Acticide PHB 20 Thor polyhexamethylene biguanide HC 0.5 CE 72 -- -- -- -- 3 Example 31 Ammonyx LO Stepan dodecane aminoxide PS 0.5 + Example 32 -- -- -- -- 3 + Example 33 -- -- -- HC 0.5 + Example 34 -- -- -- -- 3 +

(12) TABLE-US-00003 TABLE 2 Inorganic Thickening Agents Manu- Thickener Example # Thickening Agent facturer Active Substance Ox. 2 (wt. %) Rating CE 73 Laponite EP Rockwood organically modified natural sheet silicate PS 1 CE 74 -- -- -- HC 1 Example 35 Laponite RD -- synthetic sheet silicate PS 1 + Example 36 -- -- -- HC 1 + CE 75 Optigel CK -- natural bentonite PS 1 CE 76 -- -- -- HC 1 CE 77 Optigel WX -- organically modified natural sheet silicate PS 1 CE 78 -- -- -- HC 1 CE 79 Optigel W724 -- organically modified smectite PS 1 CE 80 -- -- -- HC 1 CE 81 Optigel WA -- activated smectite PS 1 CE 82 -- -- -- HC 1 Example 37 HDK D1515B Wacker pyrogenic silicic acid PS 1 + Example 38 -- -- -- HC 1 +

(13) Without wishing to be bound by theory and with the limitation mentioned above that the adjuvant materials of the active substance formulated into the above commercial products were unknown, the following can be derived from the above Table 1:

(14) Peroxydisulfate (PS) is preferable to hypochlorite (HC) as the second strong oxidant when organic surfactants are to be used as thickening agents. Further, the amount of organic surfactants to be used is to be minimized to guarantee the stability of the composition for a sufficient amount of time. Although some surfactants remain stable in a proportion of 7% by weight, others will cause a reaction even at above 2% by weight. The concentration of the organic surfactant in the composition should therefore preferably not exceed 3% by weight, more preferably not exceed 2% by weight. If this amount is not sufficient for the desired limitation of flowability, one or more inorganic thickening agents can additionally be added, which also entails advantages for removing inorganic residues, as mentioned above.

(15) Regarding the material classes of the organic surfactants, anionic surfactants such as fatty alkyl (benzene) sulfates, sulfonates, carboxylates, and phosphates, tend to be more stable than cationic surfactants such as fatty alkyl ammonium salts or (in highly alkaline milieus) neutral molecules such as fatty alkyl amines, amphoteric surfactants (betaines) or non-ionogenic surfactants. While the latter, such as polyalkylene oxide fatty alkyl ether, were occasionally stable, it would be better to modify them with anionic groups. An exception are fatty alkyl aminoxides that provided very goos results. Polysaccharides such as cellulose and xanthane derivatives were not stable as expected, which should be due to the easy oxidability of the numerous OH groups. Among the two silicone derivatives tested, one was suitable at a low amount, but its exact modification was not known. The other one, an amino-modified silicone elastomer, was not even stable at an amount of 0.5% by weight.

(16) Table 2 including the results achieved with inorganic thickening agents shows that both synthetic phyllosilicate and pyrogenic silicic acid (also referred to as amorphous silicic acid) are suitable for use as thickening agents in the composition. Again, it depends on the modification whether a sufficiently stable composition can be maintained or not. Without wishing to be bound by theory, it is assumed that natural products contain too large amounts of organic contaminants that are targeted by the oxidants, resulting in false detection results. The same is true to an even greater extent for organically modified, inorganic thickening agents.

(17) A person of average skill in the art is able to determine a suitable synthetic, inorganic thickening agent and/or an organic thickening agent as falling within the selection according to the present invention for an otherwise predetermined composition conveniently and without undue experimentation, but by means of simple serial experiments based on their general knowledge in the art and using the instructions herein.

Examples 39 to 42 and Comparative Example 83Vertical Surface

(18) Compositions of the thickening agents, Dowfax 2A1 (analogous to Example 1 but using 0.5% by weight of thickening agent), Ammonyx LO (analogous to Example 33), Laponite RD (analogous to Example 35, but using 1.5% by weight of thickening agent), and HDK D1515B (analogous to Example 37, but using 1.5% by weight of thickening agent), i.e. two organic (fatty alkyl diphenyl oxide disulfonate; dodecane aminoxide) and two inorganic thickening agents (sheet silicate; pyrogenic silicic acid), were prepared as compositions of Examples 39 to 42. A corresponding composition without using thickening agent but peroxydisulfate as a second oxidant served as Comparative Example (CE) 83.

(19) All four compositions were sprayed onto a vertical stainless steel surface to which one stroke of a 0.1%, or 0.01%, glucose solution, was previously applied and dried to obtain a glucose amount of about 1 mg/100 cm.sup.2, or 0.1 g/100 cm.sup.2, respectively, as the organic contaminant of the surface.

(20) The compositions of Example 39 (Dowfax 2A1) and Example 50 (Ammonyx LO) were each present as a stable foam, that of Example 41 (Laponite RD) as a thixotropic gel and that of Example 42 (HDK D1515B) as a thixotropic liquid.

(21) The compositions of Example 39 through 42 that first had a purple color changed their color to green at the contaminated spots on the surface within 30-120 seconds, indicating the presence of the organic contaminant. The green color was then maintained for 1-2 minutes each without observing a visible shift of the composition by flowing off.

(22) In the composition of Comparative Example (CE) 83 that did not have thickening agent hardly any visible discoloration was observed as it immediately ran off the surface. Also, based on the therefore low sheet thickness, no color recognition was possible.

(23) Contrary to that, the composition of Examples 39 through 42 turned out to be highly sensitive. The FIGURE shows a black and white photograph of the test of Example 40 about 10 minutes after application of the composition onto the surface (when the foam had already begun running off the surface). Reference numeral 1 indicates the non-discolored, darker portion of the foam (which was in fact stained purple), while reference numeral 2 indicates the lighter portion (actually stained green) in the left half that was more heavily contaminated (1 mg glucose/100 cm.sup.2) and reference numeral 3 indicates the lighter portion (stained green) in the less contaminated right half (0.1 mg glucose/100 cm.sup.2).

(24) It can be discerned that the discoloration on the right is slightly less intense but still very clearly visible to the naked eye. The contamination is clearly detectable in both cases.

(25) The present invention is thus able to quickly and reliably detect even organic contaminants at an amount of only 0.1 mg/100 cm.sup.2 so that they are clearly discernible, even though an organic surfactant was also used as a thickening agent in Example 40 shown in the FIGURE. The latter obviously did not display a false-positive result over 10 min (because otherwise the entire foam would have had to change color).

(26) Smaller amounts of contaminants can, of course, also be detected, either still with the naked eye or by conducting a computer-assisted digital color comparison. Such comparison can, for example, be made by taking a photograph of the surface covered with the composition using a digital camera and comparing the photograph with a given color scale using color comparison software, e.g. by converting the colors on the photo, or at least a relevant section thereof, to RGB values.

(27) As a result, residual contaminants can be even detected on surfaces already subjected to cleaning using the present invention. The present invention is therefore perfectly suitable for the quality control of cleaning processes in industrial plants.

Example 43Surface Facing Downwards

(28) A gelatinous, thixotropic composition formed with the sheet silicate Laponite RD at an amount of 1.5% by weight as a thickening agent (analogous to Example 41) was sprayed onto the bottom side of a stainless steel plate that had been prepared with glucose as an organic contaminant in a manner analogous to Examples 39 through 42 above. Again, green coloration appeared within 30 seconds and remained visible during the following 5 minutes. The composition did not exhibit any tendency to drip off during this period.

Examples 44 Through 58 and Comparative Examples 84 and 85Manganese Dioxide Formation

(29) Compositions were prepared as indicated aboveeach with peroxydisulfate as the second oxidantusing the types and amounts of thickening agents listed in Table 3 below and examined for manganese dioxide formation.

(30) For this purpose, 100 ml of each compositionoptionally together with 1 ml of a 0.01% glucose solution as the contaminantwere filled into a transparent glass bottle, a small stainless steel metal plate was immersed into the liquid, the bottle was sealed and allowed to stand for 20 minutes. Subsequently, the metal plate was removed and visually inspected for adherent manganese dioxide residues, as was the bottle wall. The observed amounts of adhering manganese dioxide were evaluated as follows:

(31) no manganese dioxide sediments visible

(32) + minimum amounts of manganese dioxide sediments

(33) ++ visible amounts of manganese dioxide sediments

(34) +++ high amounts of manganese dioxide sediments

(35) ++++ very high amounts manganese dioxide sediments.

(36) It is clearly discernible from Table 3 on the following page that the amount of manganese dioxide sediments at the bottle wall and/or the metal plate could bepartly significantlyreduced in all Examples of the present invention as compared to the Comparative Examples.

(37) TABLE-US-00004 TABLE 3 Manganese dioxide formation + Contam- Thickener Wall Plate Example # Thickening Agent Active Substance inant (wt. %) Rating Rating CE 84 No ++ +++ Example 44 Dowfax 2A1 branched C12-alkyl diphenyl oxide No 0.3 ++ clisulfonate Example 45 -- -- No 0.6 + + Example 46 -- -- No 0.9 ++ + Example 47 Laponite RD synthetic sheet silicate No 5 ++ ++ Example 48 -- -- No 10 ++ + Example 49 -- -- No 15 + + Example 50 HDK D1515B pyrogenic silicic acid No 5 +++ +++ Example 51 -- -- No 10 ++ ++ Example 52 -- -- No 15 + CE 85 Yes +++ ++++ Example 53 Dowfax 2A1 branched C12-alkyl diphenyl oxide Yes 0.3 +++ +++ disulfonate Example 54 -- -- Yes 0.6 ++ ++ Example 55 -- -- Yes 0.9 + ++ Example 56 LaponiteRD synthetic sheet silicate Yes 5 +++ +++ Example 57 -- -- Yes 10 ++ ++ Examp e 58 -- -- Yes 15 +

Examples 59 Through 64 and Comparative Examples 86 and 87Indicating Effect

(38) In order to examine the amount at which permanganate provides for a well detectable color change in the compositions when reacted with organic contaminants, the following experiments were conducted.

(39) Compositions each containing the following were prepared:

(40) TABLE-US-00005 KMnO.sub.4 0.01 g HC 1.3 g NaOH 0.35 g thickener 0.9 g water to 1000 ml

(41) The thickener used in all cases of this series of experiments was Laponite RD. To these solutions, which therefore contained a permanganate concentration of 0.01 g/L, different amounts of additional KMnO.sub.4 were added to give the concentrations listed in Table 4 below. These solutions were then sprayed onto a vertical ceramic tile wall to which a 0.01% glucose solution had been previously applied and dried in a manner analogous to Examples 30 through 42 to obtain a glucose amount of about 1 mg/100 cm.sup.2 as the organic contaminant of the surface.

(42) The color change of the indicator from purple to green due to the reduction of the permanganate was visually inspected on the surfaces sprayed with the compositions and evaluated as follows:

(43) Color change not at all or hardly visible

(44) + Color change visible with difficulties

(45) ++ Color change conveniently visible

(46) TABLE-US-00006 TABLE 4 Color Change KMnO.sub.4 Conc. added KMnO.sub.4 Example # (mg) (g/L) Color change CE 86 0 0.01 Example 59 100 0.11 + Example 60 150 0.16 ++ Example 61 200 0.21 ++ Example 62 300 0.31 ++ Example 63 500 0.51 ++ Example 64 600 0.61 + CE 87 750 0.76

(47) It can be seen that a color change generally suitable to detect non-contamination was visible starting from a permanganate concentration of 0.11 g/L and up to a concentration of 0.61 g/L. It was conveniently visible within a concentration range of from 0.16 to 0.51 g/L. With 0.01 g/L of permanganate the coloration of the composition was too pale, while that at 0.76 g/L was too intense to be clearly able to discern the color changes.

(48) From this, one can derive a preferred concentration range for permanganate as an indicator of from about 0.1 to 0.6 g/L and an even more preferable range of from about 0.15 to 0.5 g/L.

(49) In addition to the permanganate concentration ranges to be preferred, the examples above also clearly show that in such preferred embodiments of the present invention, permanganate is used not so much as an oxidant but rather as an indicating system, as the absence of color change shows that the oxidant contained next to permanganate has already eliminated all contaminants eligible for oxidation. Therefore, in these embodiments of the invention, the additional oxidant is in fact the main oxidant.

Example 65Cleaning Effect

(50) Considering the results of the Examples above, the ratio of the amounts of permanganate and additional oxidants as well as that amount of oxidants in the compositions which is at least required to effect thorough cleaning of surfaces from tenacious contaminants in addition to a detection effect within a relatively short exposure time were examined. To do that, the following mixtures were prepared, with the amount of hypochlorite being varied as indicated in Table 5 below:

(51) TABLE-US-00007 KMnO.sub.4 0.01 g HC between 0.03 and 1.3 g NaOH 0.35 g thickener 0.9 g water to 1000 ml

(52) 15 ml of a mixture of 40 g of malt extract and 8 g of diatomaceous earth (in 38 g of town water) were applied as an artificial contaminant difficult to remove on 1515 cm steel plates with known weights and dried. Then, the above mixtures were sprayed on, each allowed to take effect for 2 minutes, then rinsed with 50 ml of water and dried

(53) The dried plates were then weighed to detect whether there were still organic residues on them.

(54) In Table 5 below, the cleaning effect with respect to the artificial contaminant (48 g in total) was evaluated based on how much of it had remained on the respective plate:

(55) >30 g

(56) <30 g, but >20 g

(57) + <20, but >10 g

(58) ++ <10 g

(59) TABLE-US-00008 TABLE 5 Cleaning effect HC added Ratio Cleaning (g) HC:KMnO4 effect 0.0 0.03 3:1 0.05 5:1 0.10 10:1 + 0.20 20:1 ++ 0.30 30:1 ++ 0.50 50:1 ++ 1.30 130:1 ++

(60) This shows that the amount of additional, or main, oxidant next to the permanganate indicator should be at least 10 times, more preferably at least 20 times the permanganate amount, and with regard to particularly fast cleaning, in particular at least 30 times the permanganate amount as well as that a concentration of at least 0.3 g/L of oxidant is required to be able to release surfaces from organic contaminants difficult to remove within a short period of time without leaving residues.

(61) The above Examples thus show that not only did the use of a suitably selected thickening the compositions restrict flowability for a period of several minutes such that the compositions even adhered to vertical and downward facing surfaces, but also the stability of the oxidant could be increased and the formation of manganese dioxide effectively suppressed, thus improving the detectability of organic contaminants through simple color change and significantly reducing the formation of inorganic residues on the surfaces to be tested. Moreover, it was demonstrated that, when choosing suitable parameters, even organic surfactants can surprisingly be used as thickening agents in the compositions. When inorganic thickening agents are used, however, synthetic materials are preferable to natural ones as the latterprobably due to the presence of natural organic contaminants thereinmay lead to false detection results.

(62) It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.