I'm developing an HPLC assay for quantifying vitamins. I'm having a difficult time getting the fat soluble vitamins into solution. My job purchases the raw materials as spray dried powders, and I have a feeling that's part of the problem. I have tried 75/25 ACN/MEOH, Chloroform, Methylene Chloride, and absolute ethanol, 50/50 MEOH/Chloroform. I sonicate each solution for 10 minutes. The powders are just flocculated throughout the solvent. That, and the lack on peaks on my chromatograms, tells me nothing is going into solution. I have read to try ether, but instinct is telling me that if I'm having trouble with a lll of the solvents I've already tried, ether will be no different.
Any ideas or help would be greatly appreciated.