delete one feed article

Hi,
I don’t understand how to delete on my feed an article I had created to with a “lorem ipsum” text to test my website. I deleted it from my wordpress admin, but it is always in my feed. All my feeds are redirect to feedburner, I have looked inside phpadmin and the wordpress BDD, but I can see this article to delete it.
I don’t understand how the feed is working and how to modify it ? Where is the wordpress XML file, because in feedburner I can see a XML file but can not modify it ?
Is there anyone who could help me ?
Thanks a lot ;