Having carryover issues with selenium and molybdenum (7900)

Bump. Added some more info and context. 

You can split your system.  try the self-aspiration with the nebulizer.  Splitting your system.  Check if you see with the blank in self -aspiration the Mo and Se in tune monitor screen. If it's there focus on the torch box and everything else related to between the gate valve and nebulizer.   If it's gone. Focus on the sample intro.  You may want to try to rinse for at least 20min with 10% HNO3 and 1%HCl max (2%). Then go back to normal operation. Try to monitor Mo and Se during the rinse to see if you have an active site that will be cleaning with the rinse solution. Lastly, check the sample probe for any trace of dirt or restriction since you run 6020 these can stress part.  Make sure the sample probe you use is 1mm (double band blue).  Could be the blank that is contaminated.  (Same tube reused, same volumetric flask... etc) 

I'll give this a shot tomorrow and see what happens.

ulrichntaniel said:

Could be the blank that is contaminated.  (Same tube reused, same volumetric flask... etc) 

One thing to note: The contamination washes out with a second injection from the same blank. It isn't the bottles or solution that's contaminated

Update:

the issue is the switching valve. When it switches over to "inject" the Mo comes through. I've replaced both the stator and rotor and cleaned the heck out of the valve. It's still carrying over

You may want to check your solution (carrier, ISTD) one by one and monitor them in tune screen.   If you look at the inject graphic: carrier, sample loop, ISTD are going in.  You may want to replace part of the valve, or the loop has active site or is contaminated.  

You may want to check your solution (carrier, ISTD) one by one and monitor them in tune screen.   If you look at the inject graphic: carrier, sample loop, ISTD are going in.  You may want to replace part of the valve, or the loop has active site or is contaminated.