Anisole as a mobile phase additive

[VMC]

I am trying to use 1% anisole in water/methanol as mobile phase to detect some steroids by LC-APPI-MS. My column is a Gemini C18 and I have noticed an increase in the backpressure (3x) even injecting just pure standards. Could someone tell me if anisole could damage a RP column if used in a such high concentration?
Thanks,
Valdemir

[Mark Tracy]

As far as I know, anisole is compatible with silica, stainless steel and PEEK. Anisole is more viscous than either water or methanol, but at 1% the effect ought to be small. How great an increase have you observed? Is it continuing to build? It is possible that there are poorly soluble contaminants in your anisole that precipitated in the mobile phase. Is your nebulizer still operating with normal backpressure?

[james little]

why not just add the anisole in methanol post column with a tee.

We routinely use a Waters 510 pump to add a variety of things for electrospray and APCI analyses.

The addition of the anisole post column/post detector would not interfere with a UV detector in series with the MS.

[VMC]

James and Mark,
Thank you for your comments.
I have observed an increase of 3x in backpressure after using this mobile phase for 1 week. Nothing changed in APCI probe backpressure. My anisole seemed to be ok but I will try to distillate it and try again.
I use post column mixing only when it is unavoidable. It is another detail to check in each analysis. It would make the method much simpler if I could add the dopant directly to the mobile phase.
Thanks.

[ym3142]

Hi, Everyone,
Could you explain:
why anisole is needed here?
Thanks