7900: What's causing my standards to split?

Are you running the full Start Up (Torch Axis, EM, Plasma Correction, Resolution/Axis, Standard Lens Tune, and Performance report)? You mentioned running an autotune, but it's also important to run the Start Up which optimizes hardware settings that the batch autotune does not. The batch autotune only optimizes the lenses for each tune mode. 

Also, typically we run the HMI-4 preset for most EPA sample matrices, this will have preset parameters for the RF Power, Sample Depth, Nebulizer and Dilution Gas Flows. The preset conditions are well vetted to provide the most robust conditions, so I recommend reverting back then reevaluating the drift issue. I would uncheck the box for all parameters and go back to the preset mode for HMI since right now you are running an odd mix of low matrix and HMI which will not yield the best stability. 

Also, how old are your cones?

What concentration internal standard are you using?

Can you confirm that your grounding T (also called the mixing T) is clamped in the peri pump?

Are you running the mineral elements as well (Ca, Na, Fe, K, etc)?

Chelsea Tajc said:

Also, typically we run the HMI-4 preset for most EPA sample matrices, this will have preset parameters for the RF Power, Sample Depth, Nebulizer and Dilution Gas Flows. The preset conditions are well vetted to provide the most robust conditions, so I recommend reverting back then reevaluating the drift issue. I would uncheck the box for all parameters and go back to the preset mode for HMI since right now you are running an odd mix of low matrix and HMI which will not yield the best stability. 

Update on this: My tune counts have dramatically decreased. I'm getting 1/4 of what I used to. It's making it very difficult to pass a He tune due to poor RSD

"I always like to condition cones with the ICSA or 0.3% NaCl for at least 30 min"

I only do 15 mins, I wonder if it's just not long enough. All the literature said 10. 

Chelsea Tajc said:

ow are the RSDs for H2 mode esp the ISTDs? Are they going up on samples or for QC?

The RSDs look pretty solid. Between 0 and 5%, there's a few outliers but it looks random. A CCB at 10% and a sample at 8%

Feel free to send me your batch or method. I’m happy to look it over and offer more advice. Often these issues are hard to troubleshoot in the forum and in email I will be able to share larger files. I left my email above on one of the replies. 

What is  ICSA?

ICSA is an interference check solution used for EPA methods. It’s a mix of elements (primarily minerals) at high levels which is why we use it for cone conditioning. 

Thank you for explaining!

I grounded my cables and it's looking a lot better. I switched almost all my tune settings to the HMI settings, but I had to manually increase the neb flow rate to get enough counts on mass 9 to pass a tune. Any ideas how I can increase the sensitivity during a tune? The performance reports every morning look solid, but the sensitivity at the low end during tuning is trash

I grounded my cables and it's looking a lot better. I switched almost all my tune settings to the HMI settings, but I had to manually increase the neb flow rate to get enough counts on mass 9 to pass a tune. Any ideas how I can increase the sensitivity during a tune? The performance reports every morning look solid, but the sensitivity at the low end during tuning is trash

I’m glad the grounding T helped! When you added the slider for the HMI, did you drag the slider bar to the low end (HMI-4) setting? By default it sets to HMI-25 which is much too high for your method. Normally when I run an EPA tune check in HMI it’s as simple as increasing the concentration of the tuning solution. The method allows you some flexibility on this.  The EPA method was written with drinking water in mind where everything is run in nogas so naturally just going to He will result in less sensitivity and it will be even more present for the low masses like Be.

HMI-4 will also result in a decrease of sensitivity, but you will have significantly better stability and a more robust plasma and we can often sacrifice some counts for better stability. I do like to remind people that the the tune uses a 0.1 sec integration time so the report is in counts not counts per second so it will always make it seem like the instrument is not as sensitive since the numbers will be 10x lower than what you see in data analysis. 

Chelsea Tajc said:

When you added the slider for the HMI, did you drag the slider bar to the low end (HMI-4) setting?

I had it at 8. I'll turn it down and try again

Chelsea Tajc said:

Normally when I run an EPA tune check in HMI it’s as simple as increasing the concentration of the tuning solution. The method allows you some flexibility on this.

Interesting, I'm looking at our SOP and it doesn't specify a concentration. 

Our standard is 10 ug/L. We could easily go up from here, then. Hmm

Edit: I found it, the SOP does specify 10 ug/L. Do you have a link to that EPA documentation?

Evaluate at HMI-4, that should definitely help with counts since it uses a higher neb flow and less dilution gas. If needed you do have flexibility with the concentration. The tune check is only required in one mode and that’s typically no gas, but if you do not run no gas for your method  you will need to account for the count difference between helium/hydrogen.

www.epa.gov/.../epa-200.8.pdf