from Kashrut.com:
Rabbi Blech in Know thy Beans Kitniyos in the Modern World quotes the following characteristics of kitniot that are listed by authorities: cooked grains which may be confused with chometz, grown in fields adjacent to chometz, and ground into flour and confused with chometz. Rabbi Moshe Feinstein (in Igros Moshe O”Ch III:63) said that there is no Halachic basis to extend this to new foods. The Chicago Rabbinical Council accepts the use of quinoa that has not come in contact with chometz on the basis of this ruling. (See also http://www.kashrut.com/Passover/Quinoa/.)