Initially, I would use SPE cartridges that have been shown to have a high recovery in mammalian cells.  All molecules have their own unique selectivity for the stationary and mobile phases. Then I would try to use the same SPE cartridge for your lettuce plant using a spike.  Check that the sample matrix does not interfere.

But, I suspect you're the1st person on this island (and no-one has experience you can use).  C18 is good for colour removal (dyes).

I am going to think that you will need a combination of cartridges.

1.  A cartridge to concentrate the estrogen.

2.  A cartridge to clean-up (decolourize) the sample prior to chromatography (HPLC or GC).

Thanks sir , Butt I am afraid, if i use combination of cartridges it may be effect the estrogen recovery. I should try C18 alone. 

Do a 'Google Scholar' search 1st.  Why reinvent the wheel!  I am more a 'dilute and shoot' man myself.  What sort of %Recovery do you want?

This may help in your SPE selection.  I won't give up.  There is something out there you can use.

https://www.google.ca/#q=Waters+SPE+application+guide

BTW all C18 cartridges are not the same!  Their manufacturing process is proprietary and thus a Phenomenex cartridge will work while a Waters or Agilent cartridge will not (or vice versa).

Better ask these people.  I am sure they have done it before.

http://www.breastcancerfund.org/clear-science/radiation-chemicals-and-breast-cancer/phytoestrogens.html