Vitamin D assays

1. A dissociation buffer comprising:

1-ethyl-3-methylpyridinium ethyl sulfate at a concentration of 1% to 15%;

1-butyl-4-methylpyridinium chloride at a concentration of 2.5% to 20%;

methyl β-cyclodextrin at a concentration of 0.0005% to 0.01%; and

sodium salicylate at a concentration of 0.05% to 4%, wherein the dissociation buffer is a 25-hydroxy vitamin D dissociation buffer.

2. The aqueous 25OHD dissociation buffer of claim 1 , consisting essentially of:

1-ethyl-3-methylpyridinium ethyl sulfate at a concentration of 1% to 15%;

1-butyl-4-methylpyridinium chloride at a concentration of 2.5% to 20%;

methyl β-cyclodextrin at a concentration of 0.0005% to 0.01%; and

sodium salicylate at a concentration of 0.05% to 4%.

3. The dissociation buffer of claim 1 , wherein

the concentration of 1-ethyl-3-methylpyridinium ethyl sulfate is 15%, and

the concentration of 1-butyl-4-methylpyridinium chloride is 10%.

4. The dissociation buffer of claim 1 , comprising one or both of

methyl β-cyclodextrin at a concentration of 0.001%, and

sodium salicylate at a concentration of 0.05% to 1%.

5. The dissociation buffer of claim 4 , further comprising:

2-(N-morpholino)ethanesulfonic acid;

zinc sulfate; and

magnesium chloride.

6. The dissociation buffer of claim 1 , wherein

the concentration of methyl β-cyclodextrin is 0.001%, and

the concentration of sodium salicylate is 0.05% to 1%.

7. The dissociation buffer of claim 6 , wherein the concentration of sodium salicylate is 0.5%.

8. The dissociation buffer of claim 2 , consisting essentially of:

1-ethyl-3-methylpyridinium ethyl sulfate at a concentration of 15%;

1-butyl-4-methylpyridinium chloride at a concentration of 10%;

methyl β-cyclodextrin at a concentration of 0.0005% to 0.01%; and

sodium salicylate at a concentration of 0.05% to 4%.

9. The dissociation buffer of claim 8 , wherein

the concentration of sodium salicylate is less than 1.0%.

10. The dissociation buffer of claim 9 , wherein

the concentration of sodium salicylate is 0.5%.

11. A method for measuring 25-hydroxy vitamin D (25OHD) in a mammalian fluid sample comprising: a) contacting the mammalian fluid sample containing 25OHD with an antibody that specifically binds to 25OHD in the presence of a release reagent; and b) measuring the amount of 25OHD bound to the antibody, wherein the release reagent comprises 1-ethyl-3-methylpyridinium ethyl sulfate at a concentration of 1% to 15%;

1-butyl-4-methylpyridinium chloride at a concentration of 2.5% to 20%;

methyl β-cyclodextrin at a concentration of 0.0005% to 0.01%; and

sodium salicylate at a concentration of 0.05% to 4%, wherein the release reagent is a 25-hydroxy vitamin D dissociation buffer.

12. The method of claim 11 , wherein the release reagent consists essentially of: 1-ethyl-3-methylpyridinium ethyl sulfate; 1-butyl-4-methylpyridinium chloride; methyl β-cyclodextrin; and sodium salicylate.

13. The method of claim 11 , wherein the antibody is in solution.

14. The method of claim 11 , in which the 25OHD is a conjugate, and which comprises before step (a) a step of binding said 25OHD conjugate to a surface.

15. The method of claim 11 , which comprises after step (a) a step of binding 25OHD to a surface, wherein the 25OHD is bound to said surface by the antibody that specifically binds to 25OHD.

16. The method of claim 11 , which comprises before step (a) a step of binding 25OHD to a surface, wherein the 25OHD is bound to said surface indirectly by an antibody that specifically recognizes the antibody that specifically binds to 25OHD.

17. The method of claim 11 , wherein in step (a) said contacting is performed in the presence of add-in 25OHD bound to an enzyme.

18. The method of claim 11 , which comprises after step (a) a step of adding add-in 25OHD bound to an enzyme to the mixture of step (a), wherein the action of the enzyme on a substrate bound to the antibody produces a signal that is measured in step (b), and wherein the signal measured in step (b) is inversely proportional to the amount of 25OHD in the sample.

19. The method of claim 11 , which comprises after step (a) a step of adding add-in 25OHD bound to a substrate of an enzyme to the mixture of step (a), wherein the action of the enzyme bound to the antibody on the substrate produces a signal that is measured in step (b), and wherein the signal measured in step (b) is inversely proportional to the amount of 25OHD in the sample.

20. The method of claim 11 , wherein the 25OHD is bound to an enzyme.

21. The method of claim 20 , which comprises before step (b) a step of adding a substrate of said enzyme to the mixture of step (a), wherein the action of said enzyme on the substrate produces a signal that is measured in step (b).

22. The method of claim 11 , wherein the 25OHD is bound to a substrate of an enzyme.

23. The method of claim 22 , which comprises before step (b) a step of adding an enzyme to the mixture of step (a), wherein said enzyme recognizes the substrate bound to the 25OHD, and wherein the action of said enzyme on the substrate produces a signal that is measured in step (b).

24. The method of claim 11 , wherein the antibody is bound to a surface.

25. The method of claim 24 , wherein the antibody is bound to said surface directly.

26. The method of claim 24 , wherein the antibody is bound to said surface indirectly.

27. The method of claim 26 , wherein the antibody is bound to said surface by a secondary antibody that specifically binds to said antibody.