7900: What's causing my standards to split?

I've been having problems with my internal standards (running methods 200.8 and 6020B). The H2 standards tend to split off from the He standards. Every morning I just do an auto tune, do you think it has to do with the fact that the tune settings are different between gas modes?

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  • 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)?

  • 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

  • Here's the tune reports. The tuning solution is 0.5, 5, 25, 100, 250, and 500 ppb for most analytes, 100, 250, 1250, 5000, 12500, 25000, 50000 ppb for minerals (Na, K, Ca, etc). We don't use a mixing T as we have an ISIS system

  • What concentration is the EPA Tune solution you use for the tune report? I think you listed your calibration not the tune mix conc since it’s just one solution. Are you running it through the Tune/ISTD valve or through the carrier line when you run the tune check? You should still have a grounding T with the ISIS for the carrier line. 

  • Also, do you see a slider bar for HMI for the preset? If you are missing the slider to set the amount of HMI you may need to turn it on in settings. It’s called aerosol dilution mode for HMI and is in options. 

  • What concentration is the EPA Tune solution you use for the tune report?

    EPA tune is 10 ppb.

    Are you running it through the Tune/ISTD valve or through the carrier line when you run the tune check?

    Through the carrier line. We've had issues with the Tune line. 

    You should still have a grounding T with the ISIS for the carrier line. 

    Do you have a picture of where that would be?

    Also, do you see a slider bar for HMI for the preset? If you are missing the slider to set the amount of HMI you may need to turn it on in settings. It’s called aerosol dilution mode for HMI and is in options. 

    Alright, I turned that on.

    Looks like it's helping, but not eliminating the issue. I will be cleaning my cones next. They're not that old but some of the samples I've run were pretty bad

    Edit:

    What on earth? It sat for a few minutes while I had a small meeting and the H2 standards shot through the roof

  • If your cones are only a week old I would not clean them, cones run best when they are a little dirty or “conditioned” and I only clean them if my performance report indicates the orifice might be clogged. I always like to condition cones with the ICSA or 0.3% NaCl for at least 30 min 

    Often upward drift is indicative the cones are not the issue. I would have to see more of the data to know exactly what’s occurring since this is tricky to troubleshoot without seeing in person, how are the RSDs for H2 mode esp the ISTDs? Are they going up on samples or for QC?

  • Feel free to compress any of your data batches (entire .b file) and send to me. My email: chelsea.tajc@agilent.com. Please add in the subject line “Agilent Community” 

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