ICP-MS 7700 Tune not passing in Helium gas mode (%RSD is little bit high)

There are a lot of things that could cause RSD to run high.  Condition of the peristaltic pump tubing for both the sample and internal standard lines.  Proper tensioning of those lines to ensure smooth, even flow of sample and Internal standard.  These are the top 2 causes of high RSD.

Are the RSD for internal standard masses high as well?  If you select "none" for internal standard on one of the analyte masses and process batch, does the RSD improve?  This could point to an issue with the mixing of ISTD with sample.  The ISTD pump tubing is not properly tensioned to push into the sample stream.  

Are you only running He mode?  How do the RSD's look on the other gas modes.  How are the RSD's on the Performance report when you turn on the plasma? 

Remember, RSD is SD/mean intensity, so if the counts are low, the RSD will be higher.  How do the counts in performance report compare to when it gave lower RSD's?

Sorry for all the questions.  Let me know what you find.

Hi SSaiyad,

1. In helium mode. If He mass count improved with Zero helium flow. then please check following.

• Leak in Helium gas line. Leak check procedure: Close He cylinder valve and set flow to 10ml/min. after overnight evacuation flow should come down to 1ml/min. 
• Replace purifiers. moisture and hydrocarbon in Helium impact sensitivity. 
• Helium purity is low. replace cylinder. 

2. If above mentioned points are good i suggest octupole replacement.