the contamination is too insignificant to worry about. just don't draw too much of whatever you draw second so that you don't have to squirt a "blend" back in. just draw your prop to the exact amount, then pull the plunger back about 1/2 to 1 ml. squirt that air in the eq just until the oil reaches the bottom of the needle being carefull not to go so far that you inject prop into the eq. then draw out the eq. say you draw a little too much and get 255mg's instead of 250. not a big deal. take care bro.