METHOD AND KIT FOR THE FAST AND COST-EFFECTIVE DETECTION OF IODIDIONS IN AQUEOUS SOLUTIONS

Description

BACKGROUND OF THE INVENTION 1. Technical Field of the invention

[0001] Iodine is an essential building block of two thyroid hormones (thyroxine and triiodothyronine). Lack of iodine causes the enlargement of the thyroid tissue (endemic goiter), a decrease in physical / mental performance during puberty, irreversible brain damage in the fetal stage, decrease in learning abilities and IQ. At the same time, excessive intake of iodine may result in thyroid dysfunction.

[0002] The importance and topicality of the topic are demonstrated by the fact that in the autumn of 1990, 151 Heads of State (or its representatives) signed the UN's agreement which declare in its action plan that iodine deficiency should be eliminated worldwide. The international picture is strongly negative because 97 million people with struma and about 900,000 people with mentally disabilities (cretenism) suffer from the consequences of iodine deficient nutrition in Europe (WHO / UNICEF / ICCIDD 1993). Iodine deficiency is one of the most common causes of the preventable mental retardation. Iodine deficiency affects the reproductive function (Glinoer, D. (1997): Clinical Obstetrics and Ginecology, 40: pp. 102-116) and children's learning abilities, as well as the severe iodine deficiency can reduce IQ levels by up to 13.5 points. (Dunn, JT, Delange, F. (2001) Journal of Clinical Endocrinology and Metabolism, 86: pp. 2360-2363).

[0003] Iodine enters into our body with food and drinking water. The iodide ion is rapidly absorbed and then accumulated in the thyroid gland. Excess amounts are secreted into the urine, but also appeared in saliva and breast milk.

[0004] The iodide ion level is determined by 24-hour urine collection as the body excretes the excess of the iodine.

[0005] The invention relates to a method and use of a kit for quick and low-cost determination of the iodide ion content, which can be used not only to detect the possible iodine deficiency conditions but also to estimate the iodide ion concentration of liquids. The scope of protection is defined by the appended claims.2. Description of the Prior Art

[0006] Several methods are known for determining iodide ion. A number of solutions existed for determining iodide ions from classical titration procedures to more complex ion chromatography methods. However, these procedures assume well-equipped laboratory conditions and include time-consuming procedures. The cost of such detection procedures is significant. Methods are known in which iodide ions are measured from urine by ion pair chromatography with electrochemical detection systems (Below H. et al., Fresenius J. Anal Chem. 2001 Oct; 371 (4): 431-6). The most frequently used clinical method for the detection of iodide ion is inductively coupled plasma mass spectrometry. Although the corresponding process provides rapid and accurate quantified data, the sample preparation and the measurement require a great expertise and substantial financial effort. The process can only be performed under laboratory conditions.

[0007] RU 2325658 discloses an ionometric method of analysis wherein the determination of the iodide ion concentration is based on an iodide ion selective electrode potential. Implementing the procedure by doing at home is extremely complicated and time consuming. Purchasing the necessary tools involves significant costs.

[0008] CN 103018238 discloses a rapid and effective method for determining the concentration of iodide ions. Metal (gold and silver) nanocomposite materials with good water solubility and high molar absorptivity are produced and the oxidative aggregation of which are inhibited by iodide ions. Thus, the iodide ion content in the admixed solution can be determined by colorimetric assay. Kiener C. et al "High-Throughput screening under demanding conditions: Cu / ZnO catalysts in high pressure methanol synthesis as an example" (Journal of Catalysts, Academic Press, Duluth, MN, US, vol. 216, no. 1, 6 March 2003 (2003-03-06), pages 110-119, XP085067303, ISSN: 0021-9517, DOI: 10.1016 / S0021-9517(02)00134-3 discloses, in combination a 0,7 mol / L Cu(NO 3 ) 2 solution and a polypropylene vessel having a volume of at least 20 ml.SUMMARY OF THE INVENTION

[0009] We have found that the above-mentioned methods allow accurate iodide concentration determination, however, their need for instruments and expertise are significant, so they are not suitable for doing at home iodide determination. In addition, the cost of the above procedures is significant, so their wide availability is limited. The above procedures are not applicable as a quick test, and are therefore inaccessible in poor countries of the world. Given that iodine deficiency affects a significant portion of the Earth's population, there is a strong need to develop a rapid test that will allow to determine the daily iodine needs of the body of their own and their families for a significant number of people in a simple procedure to avoid the aforementioned diseases.

[0010] In our research, it has been discovered that the iodide ion and an aqueous solution of water-soluble metal salts with a suitably chosen concentration in normal condition for detecting iodide ion [I -< ] in aqueous solutions, solution samples, especially in human and animal urine selectively form a precipitate. By adding a solution, which comprising metal ion, preferably a gold ion or a copper ion and selectively precipitates iodide ion to the sample, the amount of the iodide ion in the aqueous solution or such samples, especially in human and animal urine can be measured based on the colour and consistency of the water-insoluble iodide salt precipitate formed during the precipitation in the aqueous solution or such samples, especially in human and animal urine, as well as, the metal concentration needed for the precipitation and the time needed for the starting of the precipitation.

[0011] The present invention is based on the forming of copper(I) iodide in two steps by adding an aqueous solution of copper salts to the iodide ions exist in the urine in dissolved form, which is a water-insoluble precipitate (0.00042 g / L at 25 ° C) and easily detectable by eye. Unexpectedly, it has been found that the copper salts selectively form precipitates with iodide ions dissolved in the urine, which provides the option of selective detection of iodide ions. The metal salt concentrations required for the detection of iodide ions can be calculated from the solubility product constant typical for the resulting precipitates.

[0012] The metal-ion containing solutions produced from water-soluble metal salts and by selecting a suitable metal concentration selectively precipitate iodide ion under normal condition are readily available, directly non-toxic to human body and thus these can be used extensively and safely for the rapid test to be claimed. Such metal ions may include, in particular, copper (II) ions and gold (III) ions.

[0013] In the aqueous solution used in the process of the invention, the metal ion content is provided in the form of water-soluble metal salts. Examples of such metal salts include CuSO 4 , Cu(NO 3 ) 2 , Cu(CH 3 COO) 2 , and crystalline hydrated forms thereof, e.g. CuSO 4 .5H 2 O, Cu(NO 3 ) 2 .2.5H 2 O, Cu(NO 3 ) 2 .3H 2 O or Cu(NO 3 ).2.5H 2 O . According to the invention Cu(NO3)2 is used.

[0014] Determination of iodide ion concentration by gold ion is a classical titration process, but it can be stated in the case of gold ions that selective precipitation occurs in the urine under suitably selected conditions, thus iodide ion concentration can be easily determined by this process. An aqueous metal salt solution of the gold (III) ions is prepared from AuCl 3 and crystalline hydrated forms from AuCl 3 .H2O and AuCl 3 .3H 2 O.DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention relates to a method for the determination of iodide ions as claimed. In general the method can be described as a method for the determination of iodide ions in an aqueous solution, comprising the steps of: a) providing a liquid sample for which iodide ion concentration has to be determined, b) adding at least one drop of aqueous solution of a metal ion to the liquid sample of step a) wherein the metal ions selectively precipitate with iodide ion under normal conditions; c) shaking the liquid sample of step b) and waiting for 1 to 5 minutes, preferably 3 minutes; d) repeating steps b) and c) until the precipitation is clearly visible to the naked eye in the test solution; e) recording and summing up the number of drops; and f) determining the amount of iodide ions based on the number of drops.

[0016] The present invention relates to a method for the determination of iodide ions in an aqueous solution, wherein said method further comprises step a1) after step a), wherein the liquid sample is allowed to settle for 10 to 15 minutes and the supernatant liquid is separated from the settled portion.

[0017] The present invention also relates to a method for the determination of iodide ions in an aqueous solution, wherein said method further comprises step a2) after step a), wherein the liquid sample is filtered to filter out the floating impurities or protein aggregates prior to the assay.

[0018] The present disclosure also relates to a method for the determination of iodide ions in an aqueous solution, wherein the concentration of the metal-salt solution is ranging from 10 -7< to 10 4< mol / l, preferably from 10 -2< to 10 2< mol / l, more preferably from 0.1 to 1 mol / l.

[0019] The present invention further relates to the use of a kit for determination of iodide ions in an aqueous solution. The kit comprises a sample vessel, a vessel equipped with a dropper wherein the said vessel contains a metal salt solution which selectively precipitates with at least one iodide ion under normal conditions and an instruction for describing the method of determining the iodide ions in aqueous solution.

[0020] The aqueous solution to be tested may be any aqueous solution such as drinking water, milk, urine, preferably human or animal urine.

[0021] The method according to the invention should be used with caution, because if a person has high levels of iodide in the urine, it can even give a brownish, cloudy precipitate after the first drop. In relation to drop numbers the precipitation is expected within the range of 1 to 15 drops. It is necessary to observe the waiting time between the droplets, because the brownish precipitation develops over time and not immediately. The waiting time can be 1 to 5 minutes, preferably 3 minutes.

[0022] After carrying out the method according to the invention, the said sample can be treated with potassium ferrocyanide (K 4 Fe(CN) 6 ), thus contents of the sample can be disposed of in the sewer system.

[0023] The urine sample to be tested in the method according to the invention may be a 24-hour collection or the first or second urine sample of the morning. If the aqueous solution to be tested is urine and the objective is to determine the iodine deficient condition, iodine deficient condition is determined by the following correlation: 1 to 2 drops of metal ion solution mean the optimal iodide concentration (100 µg / l), 3 to 5 drops of metal ion solution mean mild iodine deficiency (50 to 99 µg / l), 6 to 7 drops of metal ion solution mean moderate iodine deficiency (20 to 49 µg / l), while 8 or more drops mean severe iodine deficiency (<20 µg / l).

[0024] The quick test for iodine secreted with urine determines values for different ranges. The daily iodine level fluctuation is related to the nutrition, therefore to be able to get the most accurate picture of the iodine supply of the subject who provided the sample, it is recommended to repeat the test once a week at the same time for a month and to evaluate the average of the resulting number of drops.

[0025] The kit used in the method according to the present invention also comprises an electronic application available on an electronic network, preferably via the Internet, which can be used to continuously monitor the subject's iodide ion level based on the values entered. This allows the individual to control the amount of iodine being delivered to the body.EXAMPLES Example 1. Determination of iodide ion content from urine by solution of Cu(NO 3 ) 2 .

[0026] At least 20 ml of urine sample was collected from the first or second urine in the morning, which was filled into a container with a transparent, quantitative mark and screw cap up to the indicated amount (20 ml). In the plastic reservoir sample holder, the urine, which can be observed in the various shades of yellow is a clear, translucent liquid by default.

[0027] The collected sample was cloudy, not completely transparent, so it was allowed to settle at low temperatures. After settling, the top of the urine was filled into the sample holder up to the mark. Then, a solution containing 0.5 mol / l Cu(NO 3 ) 2 provided in the kit separately in a dropper vial was added dropwise until the otherwise pure urine began to cloud and a brownish-brown precipitate was observed. After each drop, the urine sample was shaken and waited 1 minute before adding the following drop. After the first drop was added, a colour change occurred and the yellow urine began to green. The change in colour does not affect the measurement, only the formation of the brownish precipitate was observed. After the urine began to get opalescent, but the precipitate had not yet precipitated, one drop was needed until the observation of the precipitation by naked eye, which meant the end of the measurement.

[0028] The concentration of iodide ion in the urine is determined by the number of drops added before the development of the brownish precipitate. The more drops are needed, the less iodine is secreted by the body.

[0029] The analysis of the precipitate showed that the sample solution contained only CuI precipitate as a precipitate. Thus, the copper nitrate solution is suitable for the selective detection of iodide ion from urine.

[0030] Table 1. shows the correlation between the number of drops and the iodide ion concentration. Table 1. Ranges of iodide ion concentrationConcentration of iodide ionStages of iodine deficiencyThe amount of the test solution which needed to precipitation of the cloudy, brownish precipitatemore than 99 microgram / litreoptimal1 to 2 drops50 to 99 microgram / litremild iodine deficiency3 to 5 drops49,8 to 20 microgram / litremoderate iodine deficiency6 to 7 dropsless than 20 microgram / litresevere iodine deficiencymore than 8 drops Example 2. Determination of iodide ion content from urine by solution of CuSO 4 .

[0031] At least 20 ml of urine sample was collected from the first or second urine in the morning, which was filled into a container with a transparent, quantitative mark and screw cap up to the indicated amount (20 ml). In the plastic reservoir sample holder, the urine, which can be observed in the various shades of yellow is a clear, translucent liquid by default.

[0032] The collected sample was cloudy, not completely transparent, so it was allowed to settle at low temperatures. After settling, the top of the urine was filled into the sample holder up to the mark. Then, a solution containing 0.7 mol / l CuSO 4 provided in the kit separately in a dropper vial was added dropwise until the otherwise pure urine began to cloud and a brownish-brown precipitate was observed. After each drop, the urine sample were shaken and waited 1 minute before adding the following drop. After the first drop was added, a colour change occurred and the yellow urine began to green. The change in colour does not affect the measurement, only the formation of the brownish precipitate was observed. After the urine began to get opalescent, but the precipitate had not yet precipitated, one drop was needed until the observation of the precipitation by naked eye, which meant the end of the measurement.

[0033] The concentration of iodide ion in the urine is determined by the number of drops added before the development of the brownish precipitate. The more drops are needed, the less iodine is secreted by the body.

[0034] The analysis of the precipitate showed that the sample solution contained only CuI precipitate as a precipitate. Thus, the copper sulphate solution is suitable for the selective detection of iodide ion from urine.Example 3. Determination of iodide ion content from urine by solution of AuCl 3 .

[0035] At least 20 ml of urine sample was collected from the first or second urine in the morning, which was filled into a container with a transparent, quantitative mark and screw cap up to the indicated amount (20 ml). In the plastic reservoir sample holder, the urine, which can be observed in the various shades of yellow is a clear, translucent liquid by default.

[0036] The collected sample was cloudy, not completely transparent, so it was allowed to settle at low temperatures. After settling, the top of the urine was filled into the sample holder up to the mark. Then, a solution containing 0.2 mol / l AuCl 3 provided in the kit separately in a dropper vial was added dropwise until the otherwise pure urine began to cloud and a brownish-brown precipitate was observed. After each drop, the urine sample was shaken and waited 1 minute before adding the following drop. After the first drop was added, a colour change occurred and the yellow urine began to green. The change in colour does not affect the measurement, only the formation of the brownish precipitate was observed. After the urine began to get opalescent, but the precipitate had not yet precipitated, one drop was needed until the observation of the precipitation by naked eye, which meant the end of the measurement.

[0037] The concentration of iodide ion in the urine is determined by the number of drops added before the development of the brownish precipitate. The more drops are needed, the less iodine is secreted by the body.

[0038] The analysis of the precipitate showed that the sample solution contained only CuI precipitate as a precipitate. Thus, the gold chloride solution is suitable for the selective detection of iodide ion from urine.Comparative Example 1.

[0039] During the calibration of the number of droplets, the iodide ion concentration was determined in mg / L units for 5 parallel measurements of the same urine by ICP-MS technique, which was used to calculate the theoretical concentration of the copper solution based on the solubility product constant to determine the required concentration. In addition to the copper concentration used, the reagent consumption was inversely proportional to the concentration of iodide ions. The fact that the precipitate was copper (I) iodide was detected by ICP-MS.

Claims

1. A method for quick and low-cost determination of iodide ions in urine, comprising the steps of: a) providing an urine sample of 20 ml for which iodide ion concentration has to be determined, b) adding at least one drop of aqueous solution of Cu(NO3)2 or their hydrated forms to the liquid sample of step a) wherein Cu-ion selectively precipitates with iodide ion under normal conditions and has a concentration of 0.2 to 0.7 mol / l; c) shaking the liquid sample of step b) and waiting for 1 to 10 minutes; d) repeating steps b) and c) until the precipitation is clearly visible to the naked eye in the test solution; e) recording and summing up the number of droplets; and f) determining the amount of iodide ions based on the number of drops, wherein 1 to 2 drops of metal ion solution mean the optimal iodide concentration (>99 µg / l), 3 to 5 drops of metal ion solution mean mild iodine deficiency (50 to 99 µg / l), 6 to 7 drops of metal ion solution mean moderate iodine deficiency (20 to 49 µg / l), while 8 or more drops mean severe iodine deficiency (<20 µg / l).

2. The method according to claim 1, characterized in that said method comprises a further step of a1) after step a), wherein the liquid sample is allowed to settle for 10 to 15 minutes and the supernatant liquid is separated from the settled portion.

3. The method according to claim 2, characterized in that said method comprises a further step of a2) after step a1), wherein the liquid sample is cooled and filtered to filter out the floating impurities or protein aggregates prior to the assay.

4. The method according to anyone of claims 1 to 3, characterized in that the said liquid sample is a human or animal urine.

5. The method according to anyone of claims 1 to 4, characterized in that 2 to 5 minutes wait is required between the drops.

6. The method according to claim 1 to 5, characterized in that the method comprises a further step for treating the sample with potassium ferrocyanide (K4Fe(CN)6) after finishing the determination, thus contents of the sample can be disposed of in the sewer system.

7. The use of a kit for accomplishing the method according to any of claims 1 to 6, wherein the kit comprises a sample vessel of 20 ml, a vessel equipped with a dropper wherein the said vessel contains a 0.2 to 0.7 mol / l Cu(NO3)2 or their hydrated form solution and an instruction for describing the method of determining the iodide ions in urine sample.

8. The use according to claim 7, wherein the kit further comprises a solution of potassium ferrocyanide (K4Fe(CN)6) for treating the determined sample to be able to dispose of it into the sewer system.

9. The use according to claims 7 or 8 for quick and low-cost determination of iodide ion concentration in urine samples.

10. The use according to claims 7 or 8 for continuous monitoring of the iodide deficient condition in a subject.

11. The use according to claim 10, wherein the monitoring is carried out manually.

12. The use according to claim 10, wherein the monitoring is carried out electronically by computer program.

13. The use according to claim 10, wherein the monitoring is carried out by mobile application.