Why did we get so high darbly charged ratio (305.13% and 68.337%) for ICP-MS 7800?

Question

Hi Team, 
 1. We run the performance check before I set my tune mode, everything including the doubly charged 70/140 ratio (1.269%) is fine 1.269%.. 
 2. however, my tune report showed me a 305.13% of doubly charged ratio in no He mode, and 68.337% in He mode. (see below the pictures) 
 previously we ran the same method and did not find anything wrong. 
 3. we are testing Li, Al, V, Co, Ni, Cu, As, cd, Sb, Hg and Pb. 
 4. Could anybody please tell me what happened?

Thank you 
 best regards, 
 Di Xu

Efstathios.Sianos · Answer

Hi dear Di Xu, 
 As you understand you have elevated counts for mass 70, so the whole faction of double charged 70/140 is eleveted to the values reported. For this are two possible expanations: 
 1. When printing out the tune report you are adding an ISTD that contains Ge (germanium). Ge has an isotope of 70 and increasing the counts of this mass. 
 2. You are using ISIS3 and your Carrier/Rinse solution contains also HCl. When reaching the plasma this forms Cl2, which results to 35 x 2 = 70 elevated counts. 
 Hope I helped, 
 BR 
 Efstathios