Hello,
I use an 8900, and I am trying to analyze digested soil samples for uranium and arsenic. The samples do have high TMS, so I usually do a 20x dilution of samples and analyze with HMI 25x. During sample prep, I use a diluent with internal standards (rhodium and iridium) to make the dilutions of the samples and the calibration standards. I make sure to add the same amount of diluent to all the samples and cal stds, so all of them should have the same concentration of the internal standards. However, during analysis the ISTD % recovery always hangs around 100% until it gets to a sample, then it immediately spikes to ~140%. This is pretty confusing to me, as all the literature I've read say that ISTD recovery should tank in samples with high TMS. I still see this trend even right after cleaning the cones, nebulizer, and changing out the sample tubing. Does anyone have any literature or solutions that I could try out to fix this?
