high silver 7500

Hello,

 

We have been seeing a very high background for silver during analysis. Instrument is a Agilent 7500 ICP-MS with chemstation. The instrument has has a lot of troubleshooting/maintenance and some of the things done include general cleaning ( nebulizer, spray chamber, torch, cones), also put in service new cones, new torch , new o-ring, torch box was replaced, RF generator swapped out a month or so ago (separate issue), thoroughly cleaned the lenses, spent countless hours tuning trying to maximize sensitivity and keep the background low. All the other elements are fine. evening attempted calibrating and analyzing in cool plasma (~ 600 W) versus HOT (1600W). We also have a 7900 series we are planning to swap over to soon and not seeing the same issues. Where could the silver be coming from.

Parents
  •   When troubleshooting a high background issue on a particular element the first step is to isolate the sample introduction area from the torch. To do this unclamp the ball joint on the spray chamber and re-clamp it with a square of parafilm. Loosen the spray chamber cap to prevent it from becoming pressurized. Re-light the plasma and then observe the background level of the element in question. At this point the problem either remains or is effectively gone. If it remains it is a Cone/Lens issue. If it is gone it is a sample uptake problem.

       In my experience the uptake side of the system is nearly always the source of the problem. In many cases the ISTD supply has been the cause. Why does this happen? ISTD tubing is often forgotten during the routine replacement of peripump tubing. As long as the ISTD values are stable it is easy to forget that the tubing stretches and ages just like the sample tubing. When the peripump program does a fast uptake, there is a possibility that the CALs STDs can overwhelm the ISTD line and backwards aspirate down the line tainting both the ISTD tubing as well as the ISTD STD itself. Game over!

      The lesson here is to replace ISTD peripump tubing and check its tension frequently to avoid the problem altogether

Reply
  •   When troubleshooting a high background issue on a particular element the first step is to isolate the sample introduction area from the torch. To do this unclamp the ball joint on the spray chamber and re-clamp it with a square of parafilm. Loosen the spray chamber cap to prevent it from becoming pressurized. Re-light the plasma and then observe the background level of the element in question. At this point the problem either remains or is effectively gone. If it remains it is a Cone/Lens issue. If it is gone it is a sample uptake problem.

       In my experience the uptake side of the system is nearly always the source of the problem. In many cases the ISTD supply has been the cause. Why does this happen? ISTD tubing is often forgotten during the routine replacement of peripump tubing. As long as the ISTD values are stable it is easy to forget that the tubing stretches and ages just like the sample tubing. When the peripump program does a fast uptake, there is a possibility that the CALs STDs can overwhelm the ISTD line and backwards aspirate down the line tainting both the ISTD tubing as well as the ISTD STD itself. Game over!

      The lesson here is to replace ISTD peripump tubing and check its tension frequently to avoid the problem altogether

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