ICP-MS 7500a calibration and PA factor not works

Hi. I have some question regarding my instrument. I had run linear calibration 1.0ppb, 2.0, 5.0, 10, 25 and 100ppb. However, 100pbb always falls on analog so the point are really far away and not touching the line. Is it normal to have pulse and analog point in one graph? Sometimes got mixed as well. When i run 100ppb standard, the concentration value was out more than 15 to 20%. I will get 80ppb above or sometimes less than that for 100ppb check standard. Did my PA factor not works? I had run multiple time PA factor for every calibration, and the results are vary. Some element ok, some are not. Like example, today i run Calibration A with PA factor A, elements such as Fe, Mn will out (conc less than 90ppb). Then tomorrow i run Calibration B with PA factor B, elements such as V, Cr will out and Fe and Mn was achieved. I wonder if my PA factor not works or is this problem from detector or what..Pls help me on this. Thanks

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