Boron Sensitivity on ICP-MS 7700

Hi Envchem welcome to the Community!

I moved your question to the Atomic Spectroscopy Forum for better visibility.

Cheers,

Kristen

Hi Evchem, does that happen whet every m/z or just with boron?

For example, our 8900 gives less CPS with every meassure through time. For example the first measure gives 2.10^6 cps of m/z 232 and it goes down progressively to 1,5.10^6 cps of the same mass after 5/6 hours. Fortunately it happens with every m/z and in similar proportions.

Do you also run a blank with the QC check sample?  Is it going negative?  If so, that would indicate their was B contamination when you started your run somewhere that washed out as you ran samples.  If not running this check, add it to your runs to see if the blank cps is also going down over time. 

Compare the counts in the CalBlk (level1) from a good run to the runs that drift down like this.  Do they start out around the same or are the bad runs starting with higher counts for the blank?

Compare the counts of the blank with the counts of your 200ug/L standard.  How much higher are they?  If you are running as a check solution, it should be at least 10 times your blank.  

Remember, quartz is Borosilicate.  Are you using an inert sample introduction system?  Many standards contain trace HF to keep things in solution.  The higher the concentration of your standard, the less you are diluting that HF.  This can cause some Boron to be dissolved out of the quartz sample introduction system (nebulizer, spray chamber, transfer tube, torch).  Your samples are in plastic containers on the autosampler?  Do you use glassware in any sample/standard prep?  Volumetric flasks, pipettes, acid bottles... these would be sources of Boron contamination.  I had a customer using a glass weight to hold down the capillary line in their Internal standard solution.  They would see B and Si increase overtime from this.  Values would go up, though, not down like you are seeing, but something to look out for.