Author Topic: Offset (Interpolated) MAN backgrounds  (Read 7564 times)

Rom

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Re: Offset (Interpolated) MAN backgrounds
« Reply #30 on: June 22, 2022, 04:35:31 PM »
1. could you explain, "Attention should be given to the "Z fraction" Zbar averaging method when analyzing moderate to high Z materials" means we have to be very careful when try to use MAN backgrounds for high Zbar materials? We shouldn't use some extra tricks - only think and remember about possible physical mistakes.
2. Thank you.

John Donovan

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Re: Offset (Interpolated) MAN backgrounds
« Reply #31 on: June 22, 2022, 06:02:43 PM »
I simply mean that at higher Zbars (average atomic number materials), the continuum production is higher (Kramer's Law), and therefore the P/B ratios are lower. That means the background correction is more critical for higher Z materials. 

https://probesoftware.com/smf/index.php?topic=571.0

For common silicate and oxide materials the accuracy of the MAN method is around 200 to 300 PPM. For higher Z materials the accuracy will be lower (larger variance), but can be improved in all cases by utilizing the blank correction with high purity blank standards run as unknowns in Probe for EPMA:

https://probesoftware.com/smf/index.php?topic=307.0

Therefore one should make additional effort to be sure that ones MAN standards properly cover the Zbar range of the standard and unknown materials being investigated.

I also suggest the use of the Z fraction averaging (using Z^0.7 or Z^0.666) method in the MAN curve fits, as the mass bias from using mass fraction Zbar averaging in compounds with elements of different A/Z ratios, will become more visible at higher atomic number.

https://probesoftware.com/smf/index.php?topic=4.msg10036#msg10036

I suggest you read this paper carefully:

https://epmalab.uoregon.edu/publ/A%20new%20EPMA%20method%20for%20fast%20trace%20element%20analysis%20in%20simple%20matrices.pdf
« Last Edit: June 22, 2022, 06:04:16 PM by John Donovan »
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