[ekugrad10]

I need to test ion suppression on my LC/MS.
1. Straight calibrators (unextracted)
2. extracted blank then add straight calibrators

Run both 1 and 2 to determine ion suppression.  The issue I am having is I know they both need to have the same final volume (200ul), but I need to add internal standard to the first step.
When running straight calibrators how do I add the internal standard.  Do I make a 50/50 mixture with 100 ul of straight calibrator and 100 ul internal standard to give a final volume of 200 ul?  Second question, how much straight calibrator do I add to the extracted blank in the final step?  Do I take 180 ul of blank and add 20 ul of straight calibrator?

Thank you for the help.