Reagent compositions and method for Karl Fischer titration
A reagent composition for a Karl Fischer titration includes (1) sulfur dioxide or a derivative thereof, (2) a derivative of imidazole, (3) an alcohol, and (4) at least one amino acid that is present in an amount that is greater than zero and up to about 10 weight percent based on a total weight of the reagent composition. Moreover, a molar ratio of the derivative of imidazole to the sulfur dioxide or derivative thereof is greater than 1:1. Iodine is optionally included in a one-component reagent and excluded in a two-component reagent. This disclosure further provides a method for determining an amount of water in a sample via Karl Fischer titration. The method includes the step of providing the sample, providing the reagent composition, which optionally includes the iodine (I 2 ), and titrating the sample with the reagent composition.
1. A reagent composition for a two-component Karl Fischer titration, said reagent composition comprising:
(1) sulfur dioxide;
(2) a derivative of imidazole having the following structure:
wherein each of R, R 1 , and R 2 is independently a hydrogen atom or a hydrocarbyl group having from 1 to 6 carbon atoms, provided that R, R 1 , and R 2 are not all hydrogen atoms;
(3) an alcohol; and
(4) at least one amino acid present in an amount from about 0.0001 to about 15 weight percent based on a total weight of said reagent composition;
wherein a molar ratio of the derivative of imidazole to the sulfur dioxide is greater than 1:1.
2. The reagent composition of claim 1 wherein said at least one amino acid is proline.
3. The reagent composition of claim 2 wherein said proline is present in an amount from about 0.0001 to about 15 weight percent based on a total weight of said reagent composition.
4. The reagent composition of claim 2 wherein said proline is present in an amount of from about 0.1 to about 2 weight percent based on a total weight of said reagent composition.
5. The reagent composition of claim 2 wherein said proline is present in an amount of from about 0.2 to about 0.5 weight percent based on a total weight of said reagent composition.
6. The reagent composition of claim 1 wherein said sulfur dioxide is present in an amount of from about 0.05 to about 1, mols/liter of said reagent composition,
said derivative of imidazole is 2-ethylimidazole and is present is present in an amount of from about 0.5 to about 5, mols/liter of said reagent composition,
said at least one amino acid is present in an amount of from about 0.2 to about 0.5 weight percent based on a total weight of said reagent composition, and said alcohol is methanol and/or ethanol.
7. The reagent composition of claim 6 wherein said at least one amino acid is proline.
8. The reagent composition of claim 1 wherein said sulfur dioxide is present in an amount of from about 0.05 to about 1, mols/liter of said reagent composition,
said derivative of imidazole is 2-ethylimidazole and is present is present in an amount of from about 0.5 to about 5, mols/liter of said reagent composition,
said at least one amino acid is present in an amount of from about 0.1 to about 2 weight percent based on a total weight of said reagent composition, and
said alcohol is methanol and/or ethanol.
9. The reagent composition of claim 8 wherein said at least one amino acid is proline.
10. The reagent composition of claim 1 consisting of:
said sulfur dioxide present in an amount of from about 0.05 to about 1, mols/liter of said reagent composition,
said derivative of imidazole that is 2-ethylimidazole and that is present is present in an amount of from about 0.5 to about 5, mols/liter of said reagent composition,
said at least one amino acid that is proline and that is present in an amount of from about 0.2 to about 0.5 weight percent based on a total weight of said reagent composition, and said alcohol that is methanol and/or ethanol.
11. The reagent composition of claim 1 consisting of:
said sulfur dioxide present in an amount of from about 6 to about 10, weight percent based on a total weight of said reagent composition;
said derivative of imidazole that is 2-ethylimidazole and that is present is present in an amount of from about 17 to about 18 weight percent based on a total weight of said reagent composition,
said at least one amino acid that is proline and that is present in an amount of from about 0.2 to about 0.5 weight percent based on a total weight of said reagent composition, and
said alcohol that is ethanol and that is present in an amount of from about 70 to about 75 weight percent based on a total weight of said reagent composition.
12. A method for determining an amount of water in a sample via Karl Fischer titration, said method comprising the steps of:
A. providing the sample;
B. providing a reagent composition comprising:
(1) sulfur dioxide;
(2) a derivative of imidazole having the following structure:
wherein each of R, R 1 , and R 2 is independently a hydrogen atom or a hydrocarbyl group having from 1 to 6 carbon atoms, provided that R, R 1 , and R 2 are not all hydrogen atoms;
(3) an alcohol;
(4) at least one amino acid present in an amount from about 0.0001 to about 15 weight percent based on a total weight of the reagent composition; and
(5) optionally iodine (I 2 );
wherein a molar ratio of the derivative of imidazole to the sulfur dioxide is greater than 1:1; and
C. titrating the sample with the reagent composition.
13. The method of claim 12 wherein the at least one amino acid is proline.
14. The method of claim 13 wherein the proline is present in an amount of greater than zero and up to about 15 weight percent based on a total weight of the reagent composition.
15. The method of claim 13 wherein the proline is present in an amount of from about 0.2 to about 0.5 weight percent based on a total weight of the reagent composition.
16. The method of claim 12 wherein the sulfur dioxide or derivative thereof is present in an amount of from about 0.05 to about 1, mols/liter of the reagent composition,
the derivative of imidazole is 2-ethylimidazole and is present is present in an amount of from about 0.5 to about 5, mols/liter of the reagent composition, the at least one amino acid is proline and is present in an amount of from about 0.2 to about 0.5 weight percent based on a total weight of the reagent composition, and the alcohol is methanol and/or ethanol.
17. The method of claim 12 wherein the sulfur dioxide or derivative thereof is present in an amount of from about 0.05 to about 1, mols/liter of the reagent composition, the derivative of imidazole is 2-ethylimidazole and is present is present in an amount of from about 0.5 to about 5, mols/liter of the reagent composition,
the at least one amino acid is proline and is present in an amount of from about 0.1 to about 2 weight percent based on a total weight of the reagent composition, and the alcohol is methanol and/or ethanol.
18. (Withdrawn/Currently amended) A reagent composition for a one-component Karl Fischer titration, said reagent composition comprising:
(1) sulfur dioxide;
(2) a derivative of imidazole having the following structure:
wherein each of R, R 1 , and R 2 is independently a hydrogen atom or a hydrocarbyl group having from 1 to 6 carbon atoms, provided that R, R 1 , and R 2 are not all hydrogen atoms;
(3) an alcohol;
(4) at least one amino acid present in an amount that is greater than zero and up to about 10 weight percent based on a total weight of said reagent composition; and; and
(5) iodine (I 2 );
wherein a molar ratio of the derivative of imidazole to the sulfur dioxide or is greater than 1:1.
19. The reagent composition of claim 18 wherein said at least one amino acid is proline and is present in an amount of from about 0.2 to about 0.5 weight percent based on a total weight of said reagent composition.
20. The reagent composition of claim 18 wherein said sulfur dioxide is present in an amount of from about 0.05 to about 1, mols/liter of said reagent composition,
said derivative of imidazole is 2-ethylimidazole and is present is present in an amount of from about 0.5 to about 5, mols/liter of said reagent composition,
said at least one amino acid is proline and is present in an amount of from about 0.2 to about 0.5 weight percent based on a total weight of said reagent composition, and
said alcohol is methanol and/or ethanol.