Probeman here.
While at M&M last week I was asked a question about analyzing standards in Probe for EPMA. That is one acquires data on a standard and then from the Analyze! window one clicks the Analyze button to get a quantitative analysis of that standard *as though it were an unknown*.
Of course if the standard is the primary (assigned) standard for that element, the element in question will iterate to the correct concentration, because the standard is analyzing itself as the standard. That is why the %VAR (percent variance) value for that element is displayed in parentheses- because it isn't really a test of the analytical quality.
More interesting is when one analyzes a standard (as an unknown from the Analyze! window), and that standard contains a non-zero concentration of an element (or a zero concentration to check for spectral interferences!), and that standard is *not* the primary standard for the element in question. Then we have the so-called secondary standard situation which is the best way to check for accuracy in EPMA.
And of course because the program knows that this sample is a standard, it can also print out the published analysis of the standard from the standard database for comparison.
But it is important to remember that for the quantification of unknowns, the only elements utilized in the primary standard are the elements that are actually assigned as the primary standard for that element. All the other elements in that standard are only useful for accuracy evaluation of major elements, or zero concentrations for interference corrections, or of course as standards for the MAN background correction.
So, when you have the situation where the standards are coated with, for example carbon, and the unknowns are not coated, say for carbon analysis of a steel, you will be analyzing the coating. So, the standard for iron might be pure Fe, and one would get an analysis (from the Analyze! window) like this:
St 526 Set 3 Iron metal
St 526 Set 3 Iron metal
TakeOff = 40.0 KiloVolt = 15.0 Beam Current = 50.0 Beam Size = 0
(Magnification (analytical) = 40000), Beam Mode = Analog Spot
(Magnification (default) = 400, Magnification (imaging) = 1572)
Image Shift (X,Y): .00, .00
From Johnson-Matthey, Vacuum remelted, Batch BM1664
Optical emission: Al < 1ppm, Ca < 1 ppm,
Cr 2 ppm, Co 20 ppm, Cu 3 ppm, Ni 3 ppm
Si 60 ppm, Sn 10 ppm, Ag < 1 ppm
Oxygen 310 ppm, Nitrogen 10 ppm
Number of Data Lines: 3 Number of 'Good' Data Lines: 3
First/Last Date-Time: 08/13/2019 01:58:46 PM to 08/13/2019 02:07:32 PM
WARNING- Using Exponential Off-Peak correction for n ka
WARNING- Using Exponential Off-Peak correction for c ka
WARNING- Using Exponential Off-Peak correction for si ka
WARNING- Using Exponential Off-Peak correction for cu ka
WARNING- Using Exponential Off-Peak correction for o ka
Average Total Oxygen: .000 Average Total Weight%: 113.447
Average Calculated Oxygen: .000 Average Atomic Number: 24.060
Average Excess Oxygen: .000 Average Atomic Weight: 41.316
Average ZAF Iteration: 5.00 Average Quant Iterate: 2.00
Using Conductive Coating Correction For Electron Absorption and X-Ray Transmission:
Sample Coating=C, Density=2.1 gm/cm3, Thickness=200 angstroms, Sin(Thickness)=311.145 angstroms
St 526 Set 3 Iron metal, Results in Elemental Weight Percents
ELEM: N C Mo Si Ni V Cu O Fe Cr Mn
BGDS: EXP EXP LIN EXP LIN LIN EXP EXP LIN LIN LIN
TIME: 40.00 40.00 40.00 40.00 20.00 20.00 20.00 40.00 20.00 20.00 20.00
BEAM: 49.56 49.56 49.56 49.56 49.56 49.56 49.56 49.56 49.56 49.56 49.56
ELEM: N C Mo Si Ni V Cu O Fe Cr Mn SUM
156 -.160 10.904 -.002 .011 -.006 .002 -.016 .357 102.982 .011 .008 114.091
157 -.085 10.732 -.020 .007 -.019 -.013 -.003 .372 101.793 -.003 -.007 112.755
158 -.285 10.792 -.025 .006 .011 -.002 .033 .432 102.560 -.019 -.009 113.495
AVER: -.177 10.809 -.016 .008 -.004 -.004 .005 .387 102.445 -.003 -.003 113.447
SDEV: .101 .087 .012 .002 .015 .007 .025 .040 .603 .015 .009 .669
SERR: .058 .050 .007 .001 .008 .004 .015 .023 .348 .009 .005
%RSD: -57.10 .81 -78.83 30.67 -328.34 -169.36 544.36 10.29 .59 -433.32 -346.16
PUBL: n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. 100.000 n.a. n.a. 100.000
%VAR: --- --- --- --- --- --- --- --- (2.45) --- ---
DIFF: --- --- --- --- --- --- --- --- (2.45) --- ---
STDS: 604 506 542 514 528 523 529 913 526 524 525
STKF: .1637 .9635 .9910 1.0000 1.0000 1.0000 .9974 .2509 1.0000 .9988 1.0000
STCT: 28.99 853.49 258.45 1148.84 609.87 416.77 562.01 195.43 210.20 154.13 188.74
UNKF: -.0006 .0285 -.0001 .0001 .0000 -.0001 .0000 .0021 1.0000 .0000 .0000
UNCT: -.11 25.22 -.03 .06 -.03 -.02 .02 1.64 210.20 -.01 .00
UNBG: 1.31 .99 .39 .22 2.37 .64 2.90 2.40 .68 .28 .39
ZCOR: 2.8933 3.7968 1.1943 1.4322 1.0712 .8660 1.1135 1.8413 1.0245 .7501 1.0443
KRAW: -.0037 .0295 -.0001 .0001 .0000 -.0001 .0000 .0084 1.0000 .0000 .0000
PKBG: .92 26.40 .91 1.29 .99 .97 1.01 1.68 310.00 .98 .99
INT%: ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- -.04
Note that the total is quite high because the standard is carbon coated, and we are analyzing for carbon. And note also that the Fe concentration is wrong because we are adding 10 percent or so of carbon from the carbon coating.
But this extra carbon seen when a carbon coated standard is analyzed as an unknown, has zero effect on the standardization of unknowns because only the Fe intensities (in this standard) are being utilized for the unknown analysis. And of course we have specified in Probe for EPMA that the standards are carbon coated and the unknowns are not.
When we do this, we can analyze a uncoated sample using a standard that is carbon coated and the differences in the coating are compensated for in the matrix correction:
Un 6 H13 trav
TakeOff = 40.0 KiloVolt = 15.0 Beam Current = 50.0 Beam Size = 0
(Magnification (analytical) = 40000), Beam Mode = Analog Spot
(Magnification (default) = 400, Magnification (imaging) = 1572)
Image Shift (X,Y): .00, .00
Number of Data Lines: 5 Number of 'Good' Data Lines: 1
First/Last Date-Time: 08/13/2019 04:01:21 PM to 08/13/2019 04:27:59 PM
WARNING- Using Exponential Off-Peak correction for n ka
WARNING- Using Exponential Off-Peak correction for c ka
WARNING- Using Exponential Off-Peak correction for si ka
WARNING- Using Exponential Off-Peak correction for cu ka
WARNING- Using Exponential Off-Peak correction for o ka
WARNING- Using Time Dependent Intensity (TDI) Element Correction
Average Total Oxygen: .000 Average Total Weight%: 100.766
Average Calculated Oxygen: .000 Average Atomic Number: 24.805
Average Excess Oxygen: .000 Average Atomic Weight: 46.435
Average ZAF Iteration: 4.00 Average Quant Iterate: 3.00
No Sample Coating and/or No Sample Coating Correction
Un 6 H13 trav, Results in Elemental Weight Percents
ELEM: N C Mo Si Ni V Cu O Fe Cr Mn
BGDS: EXP EXP LIN EXP LIN LIN EXP EXP LIN LIN LIN
TIME: 60.00 60.00 60.00 60.00 36.00 40.00 36.00 90.00 20.00 40.00 40.00
BEAM: 48.49 48.49 48.49 48.49 48.49 48.49 48.49 48.49 48.49 48.49 48.49
ELEM: N C Mo Si Ni V Cu O Fe Cr Mn SUM
165 3.406 2.406 1.224 .872 .194 .953 .092 .284 86.449 4.550 .334 100.766
AVER: 3.406 2.406 1.224 .872 .194 .953 .092 .284 86.449 4.550 .334 100.766
SDEV: .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
SERR: .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
%RSD: .00 .00 .00 .00 .00 .00 .00 .00 .00 .00 .00
STDS: 604 506 542 514 528 523 529 913 526 524 525
STKF: .1637 .9635 .9910 1.0000 1.0000 1.0000 .9974 .2509 1.0000 .9988 1.0000
STCT: 29.07 853.49 258.45 1148.84 609.87 416.77 562.01 195.43 210.20 154.13 188.74
UNKF: .0142 .0061 .0103 .0061 .0018 .0107 .0008 .0015 .8480 .0573 .0032
UNCT: 3.02 5.58 2.72 7.15 1.14 4.53 .48 1.28 181.90 9.01 .62
UNBG: 1.25 .74 .32 .28 2.39 .68 2.82 2.54 .64 .29 .39
ZCOR: 2.4014 3.9407 1.1922 1.4274 1.0606 .8939 1.1019 1.8968 1.0194 .7941 1.0359
KRAW: .1040 .0065 .0105 .0062 .0019 .0109 .0009 .0066 .8654 .0585 .0033
PKBG: 3.41 8.50 9.52 26.38 1.48 7.63 1.17 1.51 283.94 32.20 2.60
INT%: ---- ---- ---- ---- ---- ---- ---- ---- .00 ---- -1.01
TDI%: .000 3.192 -.735 .000 .851 .000 .000 -4.725 2.630 .000 .000
DEV%: .0 4.6 6.6 .0 4.9 .0 .0 3.8 .4 .0 .0
TDIF: ---- LOG-LIN LOG-LIN ---- LOG-LIN ---- ---- LOG-LIN LOG-LIN ---- ----
TDIT: .00 111.00 112.00 .00 103.00 .00 .00 151.00 74.00 .00 .00
TDII: ---- 6.32 3.03 ---- 3.55 ---- ---- 3.69 183. ---- ----
TDIL: ---- 1.84 1.11 ---- 1.27 ---- ---- 1.31 5.21 ---- ----