7900 ICP-MS P/A Tune

Hi everybody,

 

When you are running the P/A tuning solution on the 7900 ICP-MS do you select all the masses in the P/A tune solution or do you just use the masses form the method that you are using.

 

Thanks.

  • Hi,

     

    The p/a tuning applies for the elements in the method that could be run above the pulse measurement. So if only the elements in the method are selected in the p/a tuning it should be enough. Running more elements, beside the elements of intrest, in the p/a adjustment makes the quality in general not beter. The p/a factor adjustment in the batch, that run automatically the p/a factor, is also a very good, automated and fast tool to adjust the p/a factor for the elements of intrest.

     

    cheers

    edgar

  • This question has been marked as assumed answered.

  • Hi Edgar,

    I was wondering if you could tell me how the software performs the P/A factor calibration if a P/A factor for a given element is not set. For example, after a P/A factor tune the P/A factor for Mg25 was given as "signal too low". In this case, how does the calibration occur?

    Also, is it at all possible for the software to output the uncorrected analogue signal so that we can perform our own P/A factor correction offline?

    Many thanks,

    Matt.

  • Hello

    Please see the below, taken from page 3 of the attached:

    Pulse/Analog (P/A) factor tuning should be performed regularly in order to achieve optimum linear response across the 9 orders of detector dynamic range. This is especially important after any Electron Multiplier (EM) adjustments, such as EM autotune, and when large numbers of samples are being analyzed over a wide range of concentrations. P/A tuning is an automated process whereby the instrument measures a solution containing elements covering the mass range being used and determines both the pulse and analog signal for each. In order to achieve accurate measurements in both modes, each isotope should generate a response between 100,000 and 1,000,000 cps. Since the relative isotopic abundance and degree of ionization vary from element to element, different concentrations of elements are necessary in order to fall within the required cps range. Previously, this was achieved by analyzing several different solutions at different dilutions, or by repeatedly adjusting the tune to vary the instrument sensitivity. Now, a new P/A tune solution (part # 5188-6524) has been developed, which includes elements across the mass range, at concentrations that will almost always result in a complete P/A tune with a single analysis of a single sample.

  • Thanks for the response, but I don't think this quite answers my question, which is how are the elements that don't get assigned a P/A factor treated by the software? Is there some sort of interpolation between P/A factors assigned to each mass? The P/A factor tuning solution does not contain all elements, so some sort of interpolation must but done to assign P/A factors to missing isotopes/elements (like B and K for example). 

  • Hi Matt,

    if there is no p/a factor found for the mass selected in the p/a factor adjustment list due to low sensitivity then a interpolation is preformed.

    The best approach to adjust for analog measurement (if applicable) is use the unique p/a function in the batch. Then all the masses measured in the method are calculated for the p/a (when the sensitivity is enough). it's not possible to do an offline adjustment or recalculation for the p/a factor. The p/a factor is stored onto the icpms hardware and is read out into the batch when needed. in the report function in the offline DataAnalysis could the for the batch applicable p/a factor be found.

  • Hi Edgar,

    Thank you for your response. That's very helpful.

    Am I correct in thinking that the in-batch P/A adjustment is only performed on samples marked as calibration standard (CalStd)? If so, if samples are run prior to that standard then is the P/A adjustment performed retroactively or do those early samples use the P/A factor that was initially stored onto the icpms hardware?

    Thanks again!

    Matt.

  • Hi Matt,

    the in-batch p/a factor is calculated with the use of all the CalStd's.

    the p/a factor in batch is used for all the measurements in the batch. if an external p/a is performed then the last external p/a factor is used (and stored in the batch) if no internal p/a factor is checked in the batch. 

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