I am trying to measure Iron in the agilent 8800 using collision/reaction cell with He gas mode. In my tuning parameters I am using the Tuning solution and in my tuning parameters I am tuning for mu 59, 89 and 140. Its also asking for a deflect tune mass (by default its set as 89 mu). I dont exactly know what this value means and i cant find literature explaining this and what to put in it. Can somebody help?