Suitable Internal Standard for Folic Acid?

[shemesh199]

Hello all , we are assaying folic acid by lc-ms-ms, are there any suitable internal standards to use. Ideally we are looking for something cheap, maybe a vitamin analog, methylparaben, folic acid 13c5? Anybody have any recommendations , and please list the vendor?

Thanks so much!

[Alp]

Stable isotope is always the best, but costs more.

If you are extracting the analyte then you want a similar compound as the IS so that it extracts the same way as the analyte and behaves the same in the ion source. I doubt methylparaben would be the best choice.