minimum real number from a list of complex numbers

[Robert Patterson]

Hi,

I have a list of numbers (the roots of a list of quadratic equations)
that represent the times at which two particles collide.  Some
collisions are impossible so that times have imaginary components.  I
want to find the lowest purely real number from the list without writing
explicit loops.

For example from
v=[1, 2, 2+1i, 0 + 1i]
I want to find 1.

Does anyone have a good idea?  I cannot see how to use isreal() for this
purpose.

Thanks

Robert