METHOD FOR MEASURING CONCENTRATION OF POLYELECTROLYTE AND PHOSPHONATE BLENDS

1 . A method for determining total concentration of polyelectrolyte or phosphonate in a sample comprising two or more polyelectrolytes and/or phosphonates, the method comprising:

optionally diluting and/or purifying the sample;

acidifying the sample to pH less than 7;

admixing the acidified sample with a reagent comprising lanthanide(lll);

allowing the polyelectrolyte or phosphonate in the sample to interact with the reagent comprising the lanthanide(lll) ion;

exciting the sample at an excitation wavelength and detecting a sample signal deriving from the lanthanide(lll) ion at a signal wavelength by using time-resolved fluorescence; and

determining the total concentration of the polyelectrolyte or phosphonate in the sample by using the detected sample signal.

2 . The method according to claim 1 , wherein additionally a buffer is admixed with the sample, preferably non-chelating buffer, more preferably zwitterionic Good's buffer, even more preferably HEPES or tris-bis propane.

3 . The method according to claim 1 , wherein the pH of the sample is adjusted to less than 6, preferably to range 4-6.

4 . The method according to claim 1 , wherein the sample is acidified with an acid selected from the group consisting of HCl, HNO 3 , H 2 SO 4 and H 3 PO 4 .

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

6 . The method according to claim 1 , wherein concentration of the polyelectrolyte or phosphonate in the measurement mixture is in a range of 0.5-50 ppm, preferably 5-20 ppm.

7 . 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.

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

9 . 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.

10 . The method according to claim 1 , wherein the polyelectrolyte contains one or more groups selected from, carboxylic acid/carboxylate, amide, phosphonate, amine, or any combination thereof.

11 . The method according to claim 1 , wherein at least one of the polyelectrolytes or phosphonates is tagged, preferably with fluorescent tag with different excitation and emission wavelengths as compared to the used lanthanide(III).

12 . The method according to claim 11 , wherein after the determination of the total concentration of the polyelectrolyte or phosphonate in the sample, the sample is

excited at excitation wavelength specific for the tag and detecting a sample signal deriving from the lanthanide(lll) ion at a signal wavelength specific for the tag by using time-resolved fluorescence; and

determining the concentration of the at least one tagged polyelectrolyte or phosphonate in the sample by using the detected sample signal.

13 . Use of the method according to claim 1 for determining total concentration of polyelectrolyte or phosphonate in a sample.

14 . The use according to claim 13 , wherein the sample originates from water treatment, paper making processes, pharmaceutical industry, well drilling, mineral processing, enhanced oil recovery, an oilfield or an oil well or from an oil production process.

15 . A device comprising means for performing the method according to claim 1 for determining total concentration of polyelectrolyte or phosphonate in a sample.

16 . The method according to claim 4 , wherein the acid is HCl.