get some fresh picked lettuce or whatever other kind of greens and do the following:
1.) pick and rinse well...
do you think they're as clean as you can get them? guess again!
2.) in another bowl add cold water and some salt - mix well
3.) add the greens and soak for a few seconds and then rinse well again
when done, look at the bottom of the salt water bowl... now you see what you can't with the naked eye.
for me this also helps keeps the greens crisper and a little more vibrant.
post your results