We obtained an Ergosterol standard at 98% pure and made a standard with it. We dissolved the ergosterol in chloroform to obtain a concentration of around 0.5 mg/mL. However, we noticed that when we made this standard up it appeared as if not all of the ergosterol dissolved in the chloroform due to we saw residue float to the surface and stick to the walls of the flask. When we took an aliquot of the standard, dried it down under Nitrogen and then added Hexane to get injected onto a Restek Rxi-5ms column on a GC-MS we obtain a peak that was being identified as 3,5-Cyclo-6,8(14),22-ergostatriene. The Mass fragmentation matches up fairly well with the library of this compound also. I attached a photo of this.

Why would we be getting this peak and not one for Ergosterol?

What would cause this conversion?

Why wouldn't all of the ergosterol dissolve in chloroform?

Thanks for any help that is offered