can you describe your method and the problems associated with it in more detail? So your question is very general and you will probably only get a very general answer.
Markus Christ the problem that I'm facing is that the peak isn't pure, probably because I'm working with a wavelength that detect kinda of everything. The process is very easy I dissolve the product in water, see that the choline is soluble in water, filter it and inject in the HPLC.
I'm using
colum: C18 Sunfire water
mobile phase: water/methanol/ Heptafluorobutyric acid
I tried to search other methods in literature but without luck.
You know what you are supposed to detect. Therefore, you could just do a UV-Vis and see the absoranbce. Also, you might do a scan and see whether there are multiple peaks.
That will let you know whether your peak has multiple compounds.
have you ever thought about ion chromatography? So, as you write here, you have a problem with co-elution. LC in combination with MS in SIM mode would also be an alternative. Maybe HILIC would be also an alternative instead of RP. RP and charged molecules are often an ungrateful pairing. Ion pair reagents do not always make things better. However, you have to solve the problem with co-eluting. Other phases usually have different selectivities.
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