Karl fischer reagent
View Patent ↗A reagent for the determination of water content of a sample according to the Karl Fischer method is disclosed. The reagent comprises a base component comprised of a mixture of imidazole and a substituted imidazole. Preferably, the Karl Fischer reagent is a one component reagent comprising imidazole and 2-methylimidazole.
1. A one component Karl Fischer reagent having increased stability and homogeneity comprising iodine and a base comprising imidazole and a substituted imidazole, wherein the substituted imidazole is selected from the group consisting of 2-methylimidazole, 2-ethylimidazole, 2-propylimidazole, 2-butylimidazole, 1,2-dimethylimidazole, 1,2,4-trimethylimidazole, and 2-phenylimidazole;
wherein the molar ratio of imidazole to substituted imidazole is from about 0.5:1.5 to about 1.5:0.5; and
wherein the reagent is suitable for use as a one component reagent in volumetric Karl Fischer titrations.
2. The reagent as set forth in claim 1 wherein the substituted imidazole is selected from the group consisting of 2-methylimidazole, 2-ethylimidazole and a combination thereof.
3. The reagent as set forth in claim 1 wherein the molar ratio of imidazole to substituted imidazole is from about 1:1.3 to about 1.3:1.
4. The reagent as set forth in claim 1 further comprising a substantially water free alcohol solvent.
5. The reagent as set forth in claim 4 wherein the alcohol solvent is an ethylene glycol monoalkylether.
6. The reagent as set forth in claim 5 wherein the ethylene glycol monoalkylether comprises an alkyl group having from 1 to about 5 carbon atoms.
7. The reagent as set forth in claim 4 wherein the alcohol solvent is a diethylene glycol monoalkylether.
8. The reagent as set forth in claim 7 wherein the diethylene glycol monoalkylether comprises an alkyl group having from 1 to about 5 carbon atoms.
9. The reagent as set forth in claim 4 wherein the alcohol solvent is a propylene glycol monoalkylether.
10. The reagent as set forth in claim 9 wherein the propylene glycol monoalkylether comprises an alkyl group having from 1 to about 5 carbon atoms.
11. The reagent as set forth in claim 4 wherein the alcohol solvent is selected from the group consisting of ethylene glycol monoalkylethers, diethylene glycol monoethylether, propylene glycol monoalkylethers, methanol, propanol, 2-methoxyethanol, tetrahydrofurfuryl alcohol, and mixtures thereof.
12. The reagent as set forth in claim 4 wherein the alcohol solvent is diethylene glycol monoethylether.
13. The reagent as set forth in claim 4 wherein the alcohol solvent is present in a proportion from about 30% by weight to about 80% by weight based on the weight of the reagent.
14. The reagent as set forth in claim 13 wherein the alcohol solvent is present in a proportion from about 50% by weight to about 70% by weight based on the weight of the reagent.
15. The reagent as set forth in claim 4 further comprising sulfur dioxide.
16. The reagent as set forth in claim 15 further comprising a halic acid.
17. The reagent as set forth in claim 16 wherein the concentration of the halic acid is from about 0.1 moles/Liter to about 0.5 moles/Liter.
18. The reagent as set forth in claim 16 wherein the halic acid is hydroiodic acid.
19. The reagent as set forth in claim 16 further comprising a base selected from the group consisting of pyridine, diethanol amine, dipyridyl propane, imidazolium benzoate, methylimidazolium benzoate, and combinations thereof.
20. The reagent as set forth in claim 19 wherein the molar ratio of imidazole to additional base is from about 0.3:2 to about 2:0.3.
21. The reagent as set forth in claim 19 wherein the molar ratio of imidazole to additional base is from about 0.5:1.5 to about 1.5:0.5.
22. The reagent as set forth in claim 19 wherein the molar ratio of imidazole to additional base is from about 1:1.3 to about 1.3:1.
23. The reagent as set forth in claim 19 wherein the total amount of base in the reagent is no more than about 10 moles/Liter.
24. The reagent as set forth in claim 19 wherein the total amount of base in the reagent is no more than about 3 moles/Liter.
25. The reagent as set forth in claim 19 wherein the pH of the reagent is from about 5.5 to about 8.
26. The reagent as set forth in claim 19 wherein the reagent comprises from about 0.1 moles/Liter to about 10 moles/Liter total base, from about 0.1 moles/Liter to about 10 moles/Liter sulfur dioxide, and from about 0.01 moles/Liter to about 3 moles/Liter iodine.
27. The reagent as set forth in claim 19 wherein the reagent comprises from about 0.5 moles/Liter to about 5 moles/Liter total base, from about 0.5 moles/Liter to about 3 moles/Liter sulfur dioxide, and from about 0.1 moles/Liter to about 1 mole/Liter iodine.
28. The reagent as set forth in claim 19 wherein the molar ratio of the base to the sulfur dioxide is from about 10:1 to about 0.3:1.
29. The reagent as set forth in claim 19 wherein the molar ratio of the base to the sulfur dioxide is from about 2:1 to about 0.5:1.
30. The reagent as set forth in claim 15 wherein the pH of the reagent is from about 5.5 to about 8.
31. A one component Karl Fischer reagent comprising iodine and from about 0.8 moles/Liter to about 1.3 moles/Liters imidazole, from about 0.6 moles/Liter to about 1 mole/Liter 2-methylimidazole, from about 0.1 moles/Liter to about 0.5 moles/Liter imidazole hydroiodide, from about 0.75 moles/Liter to about 1.6 moles/Liter sulfur dioxide, and from about 780 grams/Liter to about 820 grams/Liter diethylene glycol monoethylether and wherein the reagent is suitable for use as a one component reagent in volumetric Karl Fischer titrations.
32. The one component Karl Fischer reagent as set forth in claim 31 wherein the pH of the reagent is from about 5.5 to about 8.