I run an Elan DRC II and a Nexion 1000 ICPMS. On both instruments, my calibration and all QC (including a second source standard) pass within 5% of 100 for Se82. However, when I run a sample with a known concentration, I am only able to achieve 60-80% recoveries for Se82. I have a Kr correction programmed in to account for Argon gas impurities, and I have played around with other common interferences, but they do not cause significant changes to my results.

I have ruled out interference from the digestion process, because I ran multiple known samples pre-digestion and obtained very similar results as to when it's digested. I thought it might be something wrong with the instrument, but considering I am obtaining the same results on two separate instruments, I do not think that is the problem. I believe I am experiencing some sort of interference, but haven't a clue as to what it could be. This problem started about 6 months ago, and none of our methods or laboratory conditions have changed.

I looked back at historical data, and it seems Se82 has always recovered on the low side for known samples (~90, 95% recovery), but never low enough to fail, as it has been lately.

Can anyone think of a reason why my quality control samples recover near perfect, yet my samples recover low? Does anyone have a suggestion to increase Se82 recoveries? Is there a way to cause Se82 to ionize better in the samples? Any suggestions or advice are welcome.

Thank you in advance,

Sheila Hutchinson