Low but stable Internal standard recovery on ICPMS 7900

 Hi
The internal standard recovery on ICPMS 7900 recently falls down right after calibration blank. All the controls and references are OK but the recovery percentage is too low, 20-30%, does anybody had the similar problem? The concentration is as before.
Thank

  • Is it possible that you do not have the same matrix in your rinse and the standards? It seems to me a matrix issue. Otherwise you would have a random pattern or a continuous up/down drift, if there was an issue in your sample introduction. ISTD% recovery will be calculated against the calibration blank, so you might measure the calibration blank multiple times at the beginning, to see if there is an issue in your uptake time settings. Afterwards you can switch between different versions of the calibration blank in the data analysis to see the difference. Keep in mind that you will need to configure only one calibration blank at the end. So, you can define the other cal. blank measurements as rinse or sample.    

  • I didn't have any changes recently, will try the multiple blanks and will see how it goes. Thank you

  • I checked every single point you mentioned above and finally found out the blank I was using was contaminated in the preparation lab somehow. So we prepared a new batch and everything is back now. Thanks again

  • Thanks for knowing us the solution. Have fun with the ICP-MS. Cheers. 

  • I am having a similar issue, but with my run this only happens after a more concentrated sample is added.  I can run a 1:10 dilution of that sample without a drop in recovery but more concentrated samples have issues.  My sample is 0.5g in 50 mL.  So the 1:10 is essentially 0.5g in 500 mL.  Everything else is the same as far as diluent goes.  I thought matrix issues at first until I noticed my QC's and blanks also had a low recovery.  Any idea's here?    

  • Hi Gavin, your sample is way too concentrated for ICP-MS. It is difficult to say before we see the replicates but I would recommend finding a way to measure it with 1:1000 dilution or you can go with UHMI (Ultra High Matrix Introduction) method, if you have it in your software available. 0.5 g in 50 mL = 10000 ppm. It is even for OES way too concentrated. 

  • So, am I seeing a result of saturation on the detector or have I contaminated my cones to the point they need to be cleaned?  I had a hunch the concentration was too high, but I wasn't sure why the QC's and blanks that ran after also registered with low ISTD recovery.  I did notice lower counts during the batch tune the next day so I thought maybe the cones were the issue. 

  • Hi Gavin 

    You can clean/replace nebulizer,sampling tubes,cones and torch then run to see.

    I hope, expected contamination will remove to get optimise result...

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