detergent removal help!

[scott_basehore at stratagene.com]

          I have purified an enzyme in a buffer with 0.1% NP-40 and
          0.1% Twn-20.  In order to grow crystals of my enzyme,
          suitable for X-ray crystallography, I need to remove these
          two detergents. Dialysis won't work as the detergents are
          above the critical conc. for the formation of micelles. I
          have tried an Extracti-gel D (Pierce) column, but the
          solution still foams when agitated (low-tech assay).  I am
          fairly sure that my enzyme alone will not foam at its
          present concentration.  Does anyone know a method for
          removing these detergents?  How might one assay for the
          presence of detergents?
                       "I am approaching the hypotenuse of my angst"