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Thermo Fisher Scientific

Sensitivity Verification Failure in Performance Report in Qtegra

Issue

The Sensitivity verification test has failed in a performance report within Qtegra due to the intensities of one of the isotopes being less than the specification defined in the performance report 

Environment

iCAP Q

iCAP Qnova Series

Resolution

The attached flow chart describes the order of actions necessary to troubleshoot a sensitivity verification failure

Sensitivity Verification Failure on iCAP Qnova Series ICP-MS - Flow Chart.pdf

 

The highlighted areas of the flow chart in yellow are described in more details as follows:

Run Performance Report in STD(S,R) mode

Even if you normally run performance checks in KED (S,R) mode for your daily analysis, it is important to take a step back and run a performance report in STD (S,R) mode in order to more thoroughly troubleshoot a sensitivity issue and for example see if it only occurs in KED (S,R) mode and therefore a problem that is only affecting one mode and not a sensitivity issue which is present in all modes of operation.

Free Aspirate the Nebulizer

Most nebulizers used on the ICP-MS will self-aspirate a solution without the assistance of the peristaltic pump delivering solution to it. This would apply to the glass micromist and PFA nebulizers commonly used on the ICP-MS. The exception would be the Miramist nebulizer.

To free aspirate the nebulizer, please do the following:

  1. Remove the end of the capillary tubing connected to the nebulizer from either the peristaltic pump tubing, mixing Y if using internal standard dilution or discrete sampling valve if using a PrepFAST II, FAST, or ASXpress.
  2. Place the end of the capillary disconnected in step 1 into a vial of Tuning solution
  3. Assess the performance either using the Data Display or by running a performance report
    1. If the sensitivity is restored, then the loss of sensitivity is the result of a flow issue somewhere previous to the nebulizer such as a partially clogged autosampler probe, block discrete sampling valve if using PrepFAST, ASXpress, etc. or inadequate tension on the pump tubing, etc.
    2. If the sensitivity is not restored, proceed to replace the nebulizer

 

Replace the Nebulizer

It is impossible to assess the performance of a nebulizer which is performing subpar using the naked eye. Of course, if the nebulizer is clogged or almost completely clogged then you would visibly be able to see the spray pattern effected and consequently a drastic loss of sensitivity.

On the other hand, if the nebulizer is performing subpar, the sensitivity may not necessarily be drastically affected but enough so that the sensitivity verification in the performance report will fail. The only true way to determine if the nebulizer is the source of the issue is to install a brand new one and test either using the Data Display or by running a performance report

Inspect the Injector Tube

The injector tube can be visibly inspected for damage or wear and tear with the naked eye. The internal bore of the tube should be free of any build up and the tip should be free of any sign of devitrification, chipping or cracking. If build up is observed, the injector tube should be cleaned.

If the build up is not removed after cleaning or signs of devitrification, chipping or cracking were observed, replace the injector tube. A SourceTune will need to be performed after replacing the Injector tube.

Replace the cones

Like the nebulizer, it is impossible to assess the condition of the orifice on the sample and skimmer cone unless you have a trained eye similar to how a jeweler would inspect a precious stone for clarity, etc. Of course, if the orifice is severely damaged for example by the cone having been dropped then the orifice will be visibly partially closed and the instrument will have suffered a drastic loss of sensitivity.

On the other hand, if the orifice has been marginally compromised due to buildup or erosion then the sensitivity may not necessarily be drastically affected but enough so that the sensitivity verification in the performance report will fail. The only true way to determine if the cones are the source of the issue is to install a brand-new sample and skimmer cone. After installing a new sample and skimmer cone, run a SourceTune in order to align the torch horizontally and vertically with the new cones. Then either using the Data Display or running another performance report, see if the sensitivity has been restored.

Run Full Factory Calibration Tune

Normally in the day-to-day operation of the instrument, it is only necessary to run the SourceTune to tune the plasma dependent parameters including Nebulizer Gas Flow, Extraction and CCT Focus Lens, and Torch Horizontal and Vertical position. However, if a sensitivity issue is still observed after meticulously troubleshooting the sample introduction system and interface then it is a good idea to run the Full Factory Calibration tune which will tune all of the lens’ in the Ion Optics.

Caution: It is very important to note that again this should only be performed after the sample introduction and interface have been ruled out as the cause of the sensitivity issue. The reason being that if there is a deficiency in one of these areas and the Full Factory Calibration Tune is performed then one of the lens may try to compensate for this deficiency and therefore tune itself to a wrong value which will make things worse off than when you started.

Perform a Full Factory Calibration Tune as follows:

  1. Run the autotune sequence !CaliTune STDS while in STD, STDS or STDR using the Tune B solution
  2. If you use STD, CCT, and/or KED mode(s) for normal operation, follow up step 1 by running the autotune sequence !CaliTune STD-100V while in STD mode using the Tune B solution
  3. If you use STDR, CCTR, and/or KEDR mode(s) for normal operation, follow up step 1 by running the autotune sequence !CaliTune STDR-100V while in STD mode using the Tune B solution

 

 

Analysis

Cause

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