METHOD TO DETERMINING METAL CATIONS IN WATER

1 . A method for determining concentration of metal ions having an absolute oxidation state+III or higher in a sample comprising metal ions having absolute oxidation state+III or higher, the method comprising:

optionally diluting and/or purifying the sample;

admixing the sample with a reagent comprising lanthanide(lll) ion and chelating agent or chelating agents;

allowing the metal ion in the sample to interact with the reagent comprising the lanthanide(lll) ion and the chelating agent or chelating agents; and

exciting the sample at a excitation wavelength and detecting a sample signal deriving from the lanthanide(lll) ion at a signal wavelength by using time-resolved fluorescence determining the concentration of the metal ions in the sample by using the detected sample signal.

2 . The method according to claim 1 , wherein the reagent comprising lanthanide(lll) ion and the chelating agent are or chelating agents admixed together prior admixing with the sample; or the sample and the chelating agent or chelating agents are admixed together prior admixing with the reagent comprising lanthanide(lll) ion; or the reagent comprising lanthanide(lll) ion and the sample are admixed together prior admixing with the chelating agent or chelating agents.

3 . The method according to claim 1 , wherein the metal ion is selected from the group consisting of titanium, chromium, manganese, iron, cobalt, nickel, gold and aluminum, preferably a trivalent metal ion selected from aluminum, iron and chromium.

4 . The method according to claim 1 , wherein the sample is pretreated by oxidizing metal ions having absolute oxidation state+II to absolute oxidation state+III or reducing metal ions having absolute oxidation state higher than +III to absolute oxidation state+III prior admixing the sample with the reagent comprising lanthanide(lll) ion and the chelating agent.

5 . The method according to claim 1 , wherein concentration of the lanthanide(lll) ion in the measurement mixture is in a range 0.1-100 μM, preferably 0.1-50 μM, and more preferably 1-20 μM.

6 . The method according to claim 1 , wherein concentration of the metal ion in the measurement mixture is in a range of 0.005-50 ppm, preferably 0.1-15 ppm, and more preferably 0.5-5 ppm.

7 . The method according to claim 1 , wherein concentration of the chelating agent in the measurement mixture is in a range of 0.01-500 ppm, preferably 0.1-500 ppm, and more preferably 1-200 ppm.

8 . The method according to claim 1 , wherein the chelating agent comprises at least one or more functional groups capable of chelating the lanthanide(III) and the metal ions, preferably one or more groups selected from esters, ethers, thiols, hydroxyls, carboxylates, sulfonates, amides, phosphates, phosphonates, amines or any combinations thereof; preferably the chelating agent contains additionally aromatic group or groups.

9 . The method according to claim 1 , wherein the lanthanide(lll) ion is selected from europium, terbium, samarium or dysprosium ions, preferably europium or terbium ions.

10 . The method according to claim 1 , wherein the reagent comprises a lanthanide(lll) salt, preferably halogenide or oxyanion, more preferably hydrated halogenides or nitrates, most preferably chloride.

11 . The method according to claim 1 , wherein the sample is purified by using a purification method selected from the group consisting of centrifugation, size exclusion chromatography, cleaning with solid-phase extraction (SPE) cartridges, dialysis techniques, extraction methods for removing hydrocarbons, filtration, microfiltration, ultrafiltration, nanofiltration, membrane centrifugation and any combinations thereof.

12 . The method according to claim 1 , wherein a pH value of the sample is adjusted to a level in a range between pH 3 and pH 8, preferably in a range from pH 5 to pH 7.5.

13 . Use of the method according to claim 1 for determining concentration of metal ions having an absolute oxidation state+III or higher in a sample.

14 . The use according to claim 13 , wherein the sample originates from geothermal processes, cooling towers, desalination plants, water treatment processes, mining or agricultural industry, pulp/paper mill effluent, waste streams of food industry and oil and gas production.

15 . A device comprising means for performing the method according claim 1 for determining concentration of metal ions having an absolute oxidation state+III or higher in a sample.