There is a difference of opinion among Rabbinic decisors (machloket ha-poskim) as to whether quinoa is considered kitniyot. Ask your Rabbi for his guidance.
Additionally, while quinoa is not one of the five grains that can create chametz (wheat, oat, barley, spelt and rye), and quinoa is not grown in the same vicinity as the grains mentioned above, the processing of quinoa is sometimes done at the same location where they process wheat and wheat flour. It is highly doubtful that the mills are effectively cleaned between grains. The concern of wheat flour or particles finding their way into the quinoa flour would be a serious one.