Best way to optimize peripump flow using ICP-MS 7900

I am using a Agilent 7900.  It has the ISIS hooked up and am using a internal standard of three elements, Sc, Tb, and In.  I was wondering what the best way to optimize the flow while adjusting the peri pump clamps.  The way i understand it, is that you turn the clamp until you have no flow in the channel your testing.  Once you have no flow, you then turn it till you get the solution flowing smoothly through the pump tubing.  Should i do this process with the instrument off?  Or on?  Bypass ISIS and go with a straight hook up to the nebulizer? Does it matter either way?  I have noticed once you start the mass spec, the solution can be sucked up (through the carrier line at least), so should i complete it in offline mode? 
Sometimes after taking vacations or doing some maintenance on pump tubing/PFA tubing, i notice the internal standard recovery on the stability graph isn't as 'tight' as it usually is.  The elements are seperated a little, stable and not drifting.  Cones conditioned well.  Any all and all help and insight would be appreciated.
Thank you for your time,

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  • Thanks for linking these!

    I'm on a 7900, which has two tubes. One for carrier solution and one for internal standards. What's the procedure for when you've got two? The pressures in one effect the other.

    I am thinking: 

    1) unscrew both

    2) tighten carrier tubing until flow is smooth

    3) tighten IS tubing after smooth flow of carrier has been achieved

    Does this seem right?

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