I've attached a couple of plots that show graphically how useful the blank correction can be. I have a rutile standard (NMNH 120812) that I know contains vanadium, but I've had a great deal of difficulty verifying the amount precisely due to interference from Ti Kβ1,3, Ti Kβ5, associated satellites, and also the Ti K absorption edge. Of course, this is a worst-case scenario in which the Ti concentration is very high and the V concentration is very low. Recently, I acquired a high-purity synthetic TiO2 standard, and I've overlaid its spectrum (using LiFL) on that of the natural rutile in the first plot below. In the second plot, I've essentially done a manual blank correction by subtracting the high purity TiO2 spectrum from that of the natural rutile (difference illustrated in green). There is absolutely no way to perform an overlap correction with confidence in this case, and the blank correction provides the only useful result (variable between ~0.2 and ~0.3 wt% V2O3 in this case), especially since natural rutile is generally close to end-member composition. In this particular case, the rutile contains ~98.9 wt% TiO2. I hope that someone will find this useful for both the general case and for this specific case. I often find that people minimize the importance of interference from Ti at the V Kα peak position when using LiF.
(https://smf.probesoftware.com/gallery/381_16_09_21_12_41_09.png)
(https://smf.probesoftware.com/gallery/381_16_09_21_12_41_39.png)
Quote from: Brian Joy on September 16, 2021, 01:50:14 PM
I often find that people minimize the importance of interference from Ti at the V Kα peak position when using LiF.
Absolutely. The interference on V Ka from Ti Kb is observable even on LiF.
But I am surprised that you are doing this manually for two reasons. One, you posted this in the Probe for EPMA board, and two, don't you own the Probe for EPMA software? Why don't you utilize the quant iterated interference correction in PFE? I think you will find it works excellently.
Interestingly it was seeing reports of vanadium in rutile, from when I started out in EPMA in the early 1990s, that was the impetus for developing the quantitative (iterated) interference correction:
http://www.geology.wisc.edu/~johnf/g777/777MicrobeamAnalysis/1993-JJD-InterferenceTrace.pdf
The problem back then was the use of a simple intensity ratio (e.g, Gilfrich) for the interference (overlap) correction procedure (that is, if an interference correction was utilized at all!). The point being that only by including the matrix effects between the unknown, standard *and* the standard used for the interference correction, is the interference correction truly quantitative.
Without an interference correction, the apparent concentration of V in TiO2 is around 0.1 to 0.2 wt% using LiF crystals, and of course larger for PET crystals. So I agree, it certainly cannot be ignored.
But I am also curious why you found the need for a blank correction as I have found the PFE interference interference correction method to be more than sufficient for this rather small interference correction. Even using a PET crystal, in my experience, the iterated quant interference correction seems to work well for the interference of Ti Kb on V Ka.
Of course if the issue is interpolating the background intensity across an absorption edge, then the solution is the MAN background correction.
Quote from: Probeman on September 16, 2021, 04:45:38 PM
Quote from: Brian Joy on September 16, 2021, 01:50:14 PM
I often find that people minimize the importance of interference from Ti at the V Kα peak position when using LiF.
Absolutely. The interference on V Ka from Ti Kb is observable even on LiF.
But I am surprised that you are doing this manually for two reasons. One, you posted this in the Probe for EPMA board, and two, don't you own the Probe for EPMA software? Why don't you utilize the quant iterated interference correction in PFE? I think you will find it works excellently.
Interestingly it was seeing reports of vanadium in rutile, from when I started out in EPMA in the early 1990s, that was the impetus for developing the quantitative (iterated) interference correction:
http://www.geology.wisc.edu/~johnf/g777/777MicrobeamAnalysis/1993-JJD-InterferenceTrace.pdf
The problem back then was the use of a simple intensity ratio (e.g, Gilfrich) for the interference (overlap) correction procedure (that is, if an interference correction was utilized at all!). The point being that only by including the matrix effects between the unknown, standard *and* the standard used for the interference correction, is the interference correction truly quantitative.
Without an interference correction, the apparent concentration of V in TiO2 is around 0.1 to 0.2 wt% using LiF crystals, and of course larger for PET crystals. So I agree, it certainly cannot be ignored.
But I am also curious why you found the need for a blank correction as I have found the PFE interference interference correction method to be more than sufficient for this rather small interference correction. Even using a PET crystal, in my experience, the iterated quant interference correction seems to work well for the interference of Ti Kb on V Ka.
Of course if the issue is interpolating the background intensity across an absorption edge, then the solution is the MAN background correction.
Hi John,
I never measure background on opposing sides of a K absorption edge when the interfering element is present in high concentration; it's bad practice to do so. Also, I've tried modeling background radiation (for a purpose different than this), and I've not yet come up with a satisfactory approach, especially when absorption edges are included; this makes me reluctant to use the MAN background correction, especially when I'm interested in quantification in the 2000-3000 ppm range.
I have in fact used PFE with the blank correction to address the problem of analysis of V in rutile, and I find that it works very nicely. Despite this, I like to have a visual aid to show myself (and others) the exact nature and magnitude of the problem. Considering that, in this case, Ti contributes more net radiation at the V Ka peak position than V itself indicates the interference is not "small." This term is too subjective. The reason I posted these plots is that I found myself referring to them today while analyzing chromite, as I needed to remind myself of the exact nature of the interference. I can delete the plots if you'd like.
I'm still not able to use PFE routinely, as a communication error occurs between the JEOL computer and the operator electronics. (I thought we were upgrading the JEOL software to Windows 10 two years ago, but it turns out I was mistaken.)
Brian
Yes, I agree that extrapolating (or interpolating) across absorption edges is a bad idea.
That's the cool thing about the MAN background correction as it doesn't use off-peak measurements at all. Also it does include a correction for continuum absorption, so in silicates and oxides the accuracy is good to around 200 to 300 PPM. Of course if one utilizes the blank correction in addition to the MAN correction, the accuracy will be equal to the precision of the measurement. So easily down to 50 to 100 PPM with a reasonable integration times. I personally feel this is the best combination: MAN and blank correction (if a suitable blank is available) or MAN and interference correction (if a matrix matched blank is not available).
Nothing wrong with "visual aids" as I use them myself often. I was just trying to understand why you posted this in the PFE board...
As for communication issues between PFE and JEOL, we have dozens of labs running PFE on JEOL 8230 and 8530 instruments with no issues whatsoever on Windows 7 and Windows 10. I would be happy to work with you off-line to get this working on your instrument/computer systems.
We still have the Windows XP version of the JEOL software. Owen has been trying to help me troubleshoot, but I hardly have any time to do anything but analyze stuff these days.
Yes, I realize that MAN doesn't require any off-peak measurements. It was my experience trying to model background radiation at the As Lα peak position that turned me off to the idea of accurate modeling of background radiation.
EDIT: I did the above-mentioned work in 2014 while collecting k-ratio data on GaAs and InAs (relative to elemental As). I used an approach based on Kramer's Law as modified by Small et al. (1987), Smith (1975), and Smith and Reed (1981), which I've attached. I simply couldn't get a calculated background that matched wavelength scans to my satisfaction. In using the approach of Smith and Reed, I normalized to the Si spectrum on TAP, as it contains no characteristic peaks near As Lα and Lβ1. Maybe I need to revisit the problem.
Quote from: Brian Joy on September 16, 2021, 06:33:55 PM
EDIT: I did the above-mentioned work in 2014 while collecting k-ratio data on GaAs and InAs (relative to elemental As). I used an approach based on Kramer's Law as modified by Small et al. (1987), Smith (1975), and Smith and Reed (1981), which I've attached. I simply couldn't get a calculated background that matched wavelength scans to my satisfaction. In using the approach of Smith and Reed, I normalized to the Si spectrum on TAP, as it contains no characteristic peaks near As Lα and Lβ1. Maybe I need to revisit the problem.
I completely agree that modeling the continuum over a range of photon energies is a "tough nut to crack". Especially across absorption edges. Best of luck in your efforts on this.
The cool thing about the MAN background correction method is that we only need to apply the continuum absorption correction at a *single* photon energy. In fact, the continuum photon energy one is working with, is *exactly* the same photon energy as the characteristic photon energy one is trying to correct for background! How lucky is that!
That means we might be able to utilize an absorption correction intended for characteristic photon energies to correct for continuum absorption (because they are measured at that same energy, and a photon is a photon!). Of course continuum photon emissions are spatially slightly non-isotropic compared to characteristic photon emissions, but I thought it's worth a try. And what we have found is that the characteristic photon absorption corrections give better results for the MAN curve fits, than the continuum (specific) absorption corrections of Small, Myklebust and Heinrich.
One can experiment with these different continuum absorption corrections options as shown in the MAN fit dialog in Probe for EPMA:
https://smf.probesoftware.com/index.php?topic=1221.msg8459#msg8459
In fact, PFE utilizes the same characteristic absorption correction as the currently selected matrix correction (ZAF, phi-rho-z, etc.), so one has many absorption models to play with.
But, interestingly, the largest effect we found is in utilizing a Z-fraction (rather than mass fraction) based calculation for average atomic number (Kramer's Law):
https://smf.probesoftware.com/index.php?topic=1221.msg8475#msg8475
https://smf.probesoftware.com/index.php?topic=4.msg10036#msg10036
Because of course neutrons (atomic mass) don't factor into continuum production as it's all electro-dynamics. 8)
Quote from: John Donovan on September 16, 2021, 09:24:54 PM
Quote from: Brian Joy on September 16, 2021, 06:33:55 PM
EDIT: I did the above-mentioned work in 2014 while collecting k-ratio data on GaAs and InAs (relative to elemental As). I used an approach based on Kramer's Law as modified by Small et al. (1987), Smith (1975), and Smith and Reed (1981), which I've attached. I simply couldn't get a calculated background that matched wavelength scans to my satisfaction. In using the approach of Smith and Reed, I normalized to the Si spectrum on TAP, as it contains no characteristic peaks near As Lα and Lβ1. Maybe I need to revisit the problem.
I completely agree that modeling the continuum over a range of photon energies is a "tough nut to crack". Especially across absorption edges. Best of luck in your efforts on this.
The cool thing about the MAN background correction method is that we only need to apply the continuum absorption correction at a *single* photon energy. In fact, the continuum photon energy one is working with, is *exactly* the same photon energy as the characteristic photon energy one is trying to correct for background! How lucky is that!
That means we might be able to utilize an absorption correction intended for characteristic photon energies to correct for continuum absorption (because they are measured at that same energy, and a photon is a photon!). Of course continuum photon emissions are spatially slightly non-isotropic compared to characteristic photon emissions, but I thought it's worth a try. And what we have found is that the characteristic photon absorption corrections give better results for the MAN curve fits, than the continuum (specific) absorption corrections of Small, Myklebust and Heinrich.
One can experiment with these different continuum absorption corrections options as shown in the MAN fit dialog in Probe for EPMA:
https://smf.probesoftware.com/index.php?topic=1221.msg8459#msg8459
In fact, PFE utilizes the same characteristic absorption correction as the currently selected matrix correction (ZAF, phi-rho-z, etc.), so one has many absorption models to play with.
But, interestingly, the largest effect we found is in utilizing a Z-fraction (rather than mass fraction) based calculation for average atomic number (Kramer's Law):
https://smf.probesoftware.com/index.php?topic=1221.msg8475#msg8475
https://smf.probesoftware.com/index.php?topic=4.msg10036#msg10036
Because of course neutrons (atomic mass) don't factor into continuum production as it's all electro-dynamics. 8)
OK, I need to play around with MAN once PFE and JEOL are cooperating better, and I need to read through some of your papers. The modeling that I did should have worked at a given arbitrary energy, but yes, I was indeed more concerned (and frustrated) with the "bigger picture." Also, I was using simplified atomic number and absorption corrections and found that the chosen reference spectrum (I used at least Si, Fe, and Nb, maybe others) made a significant difference in the results. I couldn't characterize the As L1, L2, and L3 absorption edges even remotely accurately.
Edit: Or maybe it's better to say that I was trying to evaluate how good the result was at the As La peak position by evaluating how well I was able to model adjacent parts of the spectrum. It's really hard to judge where the background "should" be at As La due to the fact that it and As Lb1 are incompletely resolved and also due to the presence of absorption edges on the short-wavelength side of As Lb1.
I can see how nicely the MAN background would pair with the blank correction for the case of Ti interference at V Ka (since I do have single-crystal, high purity TiO2), especially since background counting error would be eliminated.
Thought I might chip in with some user experience of a similar situation (page 7 here: https://smf.probesoftware.com/index.php?topic=4.90).
I was measuring Co in Fe-Ni meteorites, for which there is a very well known Ni:Co solar ratio.
I acquired my data with off peak backgrounds (green lines below), but had "messed up" the background measurement by putting the low side off peak measurement on the Fe Kb and trying to subtract the background using an exponential fit:
(https://smf.probesoftware.com/gallery/796_07_05_21_8_49_04.jpeg)
But there was method in my madness as, like you, I was trying to avoid a large absorption edge (Fe K [yellow line] in my case):
(https://smf.probesoftware.com/gallery/796_07_05_21_8_48_48.jpeg)
Turns out, there is no good position to put the low side background for Co Ka in a major Fe phase.
The problem came to light several months after the user's session, when they were sifting through their data and plotting everything up.
Because I'd acquired everything with off peaks, I could construct a MAN curve and use those backgrounds instead (rather than repeat the session). After a lightning speed bug fix (thanks again, John!), I could assign an Fe on Co interference with the MAN backgrounds and the results went from plotting ~250ppm below the solar Ni:Co line to sitting exactly on it (with better accuracy and precision than some of the other published measurements they had plotted, too!).
I should mention that this was using the interference correction rather than a blank correction, as I hadn't measured a pure Fe metal as an unknown, and I don't have any Fe-Ni reference materials (anyone have any recommendations for any?). The interference correction could be applied having measured Co in Fe metal for the standards (i.e. I didn't use quick standards).
Quote from: JonF on September 17, 2021, 01:34:56 AM
Thought I might chip in with some user experience of a similar situation (page 7 here: https://smf.probesoftware.com/index.php?topic=4.90).
I was measuring Co in Fe-Ni meteorites, for which there is a very well known Ni:Co solar ratio.
I acquired my data with off peak backgrounds (green lines below), but had "messed up" the background measurement by putting the low side off peak measurement on the Fe Kb and trying to subtract the background using an exponential fit:
Hi Jon,
I have to deal with that interference quite a lot, as I frequently analyze for small amounts of Co in pyrrhotite. Thankfully, on the LiFL crystal here, the "background"/tail on the high-Bragg-angle-side of Fe Kβ is almost perfectly linear, and so I'm able to place background offsets at -0.6 mm and +1.0 mm and interpolate linearly.
Brian
Quote from: Brian Joy on September 16, 2021, 01:50:14 PM
I've attached a couple of plots that show graphically how useful the blank correction can be. I have a rutile standard (NMNH 120812) that I know contains vanadium, but I've had a great deal of difficulty verifying the amount precisely due to interference from Ti Kβ1,3, Ti Kβ5, associated satellites, and also the Ti K absorption edge. Of course, this is a worst-case scenario in which the Ti concentration is very high and the V concentration is very low. Recently, I acquired a high-purity synthetic TiO2 standard, and I've overlaid its spectrum (using LiFL) on that of the natural rutile in the first plot below. In the second plot, I've essentially done a manual blank correction by subtracting the high purity TiO2 spectrum from that of the natural rutile (difference illustrated in green). There is absolutely no way to perform an overlap correction with confidence in this case, and the blank correction provides the only useful result (variable between ~0.2 and ~0.3 wt% V2O3 in this case), especially since natural rutile is generally close to end-member composition. In this particular case, the rutile contains ~98.9 wt% TiO2. I hope that someone will find this useful for both the general case and for this specific case. I often find that people minimize the importance of interference from Ti at the V Kα peak position when using LiF.
Hi Brian,
Looking through my old data I realized I've never really looked closely at this specific interference. So yesterday I acquired a test run analyzing a bunch of Ti standards for vanadium and today I took a look at the data. It's more interesting than I thought it might be... there is something going on that I don't understand. Interestingly I get very similar results using both off-peak and MAN background corrections, so I don't think the issue is extrapolation across an absorption edge.
Conditions were 15 keV, 30 nA and 60 seconds on-peak and 60 seconds off-peak. The background positions for V Ka on LiF are here:
(https://smf.probesoftware.com/gallery/395_19_09_21_10_17_09.png)
And for V ka on PET here:
(https://smf.probesoftware.com/gallery/395_19_09_21_10_17_27.png)
Where the red line is the on-peak position for V Ka, the purple lines are the old off-peak positions and the green lines are the off-peak position utilized for the acquisitions.
I acquired both Ti Ka and V Ka on both LiF and PET crystals just for fun and acquired 5 points on each standard. That way we can look at LiF data only, PET data only, or aggregate the intensities from both the LiF and PET crystals. For example, looking at the off-peak data on LIF crystals first I get this for TiO2 when no interference correction is applied:
ELEM: Ti Ti-D V V-D Sr Fe Cr Mn O SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
AVER: 59.956 --- .551 --- .000 .000 .000 .000 40.000 100.506
SDEV: .073 --- .010 --- .000 .000 .000 .000 .000 .083
SERR: .033 --- .005 --- .000 .000 .000 .000 .000
%RSD: .12 --- 1.84 --- .00 .00 .00 .00 .00
As you can see I get about 0.5% wt% apparent V in TiO2. Turning on the interference correction and using TiO2 as the interference standard, we of course get a perfect correction because it's analyzing itself:
ELEM: Ti Ti-D V V-D Sr Fe Cr Mn O SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
AVER: 59.988 --- .000 --- .000 .000 .000 .000 40.000 99.988
SDEV: .073 --- .009 --- .000 .000 .000 .000 .000 .082
SERR: .033 --- .004 --- .000 .000 .000 .000 .000
%RSD: .12 --- 9536.47 --- .00 .00 .00 .00 .00
Now if we look at another Ti standard, say SrTiO3 we obtain this with the interference correction on:
ELEM: Ti Ti-D V V-D Sr Fe Cr Mn O SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
AVER: 26.329 --- .010 --- 47.740 .000 .000 .000 26.150 100.228
SDEV: .223 --- .005 --- .000 .000 .000 .000 .000 .222
SERR: .100 --- .002 --- .000 .000 .000 .000 .000
%RSD: .85 --- 50.80 --- .00 .00 .00 .00 .00
Not terrible, but still 2 standard deviations from zero. And next we can do an extrapolation to a material containing a larger concentration of Ti such as TiC as seen here:
ELEM: Ti Ti V V Sr Fe Cr Mn C
TYPE: ANAL ANAL ANAL ANAL SPEC SPEC SPEC SPEC SPEC
BGDS: LIN EXP LIN EXP
TIME: 60.00 --- 60.00 --- --- --- --- --- ---
BEAM: 30.03 --- 30.03 --- --- --- --- --- ---
ELEM: Ti Ti-D V V-D Sr Fe Cr Mn C SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
AVER: 78.622 --- .012 --- .000 .000 .000 .000 20.000 98.634
SDEV: .259 --- .011 --- .000 .000 .000 .000 .000 .250
SERR: .116 --- .005 --- .000 .000 .000 .000 .000
%RSD: .33 --- 92.30 --- .00 .00 .00 .00 .00
Actually not too bad, just over a standard deviation from zero. Next we'll look at the results from the PET crystals and that's where the wheels really come off...
Quote from: Probeman on September 19, 2021, 10:22:29 AM
Quote from: Brian Joy on September 16, 2021, 01:50:14 PM
I've attached a couple of plots that show graphically how useful the blank correction can be. I have a rutile standard (NMNH 120812) that I know contains vanadium, but I've had a great deal of difficulty verifying the amount precisely due to interference from Ti Kβ1,3, Ti Kβ5, associated satellites, and also the Ti K absorption edge. Of course, this is a worst-case scenario in which the Ti concentration is very high and the V concentration is very low. Recently, I acquired a high-purity synthetic TiO2 standard, and I've overlaid its spectrum (using LiFL) on that of the natural rutile in the first plot below. In the second plot, I've essentially done a manual blank correction by subtracting the high purity TiO2 spectrum from that of the natural rutile (difference illustrated in green). There is absolutely no way to perform an overlap correction with confidence in this case, and the blank correction provides the only useful result (variable between ~0.2 and ~0.3 wt% V2O3 in this case), especially since natural rutile is generally close to end-member composition. In this particular case, the rutile contains ~98.9 wt% TiO2. I hope that someone will find this useful for both the general case and for this specific case. I often find that people minimize the importance of interference from Ti at the V Kα peak position when using LiF.
Hi Brian,
Looking through my old data I realized I've never really looked closely at this specific interference. So yesterday I acquired a test run analyzing a bunch of Ti standards for vanadium and today I took a look at the data. It's more interesting than I thought it might be... there is something going on that I don't understand. Interestingly I get very similar results using both off-peak and MAN background corrections, so I don't think the issue is extrapolation across an absorption edge.
Conditions were 15 keV, 30 nA and 60 seconds on-peak and 60 seconds off-peak. The background positions for V Ka on LiF are here:
The Ti K absorption edge produces a discontinuity in the continuum, especially when the compound is ~99 wt% TiO
2. It
must create problems for off-peak background measurement.
OK, so here the wheels really come off. I have to say I don't understand what the problem is. I'm doing something wrong but can't see what it might be...
Here is TiO2 analyzed for V *without* the interference correction on an LPET crystal:
ELEM: Ti-D Ti V-D V Sr Fe Cr Mn O SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
AVER: --- 59.804 --- 3.271 .000 .000 .000 .000 40.000 103.075
SDEV: --- .060 --- .015 .000 .000 .000 .000 .000 .066
SERR: --- .027 --- .007 .000 .000 .000 .000 .000
%RSD: --- .10 --- .46 .00 .00 .00 .00 .00
So that is a big spectral interference for sure. Now we turn on the interference correction again and get this result which is of course zero because it's analyzing itself (showing all data from the 5 points):
ELEM: Ti-D Ti V-D V Sr Fe Cr Mn O SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
204 --- 60.027 --- -.016 .000 .000 .000 .000 40.000 100.010
205 --- 59.999 --- .012 .000 .000 .000 .000 40.000 100.011
206 --- 59.886 --- -.009 .000 .000 .000 .000 40.000 99.878
207 --- 60.000 --- .017 .000 .000 .000 .000 40.000 100.018
208 --- 60.035 --- -.003 .000 .000 .000 .000 40.000 100.032
AVER: --- 59.989 --- .000 .000 .000 .000 .000 40.000 99.990
SDEV: --- .060 --- .014 .000 .000 .000 .000 .000 .063
SERR: --- .027 --- .006 .000 .000 .000 .000 .000
%RSD: --- .10 --- 3781.96 .00 .00 .00 .00 .00
OK, now let's look at the SrTiO3 again on the LPET crystals:
ELEM: Ti-D Ti V-D V Sr Fe Cr Mn O SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
179 --- 26.199 --- -.035 47.740 .000 .000 .000 26.150 100.054
180 --- 26.268 --- -.049 47.740 .000 .000 .000 26.150 100.109
181 --- 26.261 --- -.058 47.740 .000 .000 .000 26.150 100.093
182 --- 26.190 --- -.037 47.740 .000 .000 .000 26.150 100.043
183 --- 26.219 --- -.043 47.740 .000 .000 .000 26.150 100.066
AVER: --- 26.227 --- -.045 47.740 .000 .000 .000 26.150 100.073
SDEV: --- .035 --- .009 .000 .000 .000 .000 .000 .027
SERR: --- .016 --- .004 .000 .000 .000 .000 .000
%RSD: --- .14 --- -21.07 .00 .00 .00 .00 .00
Well that's pretty bad I have to say. But even worse is the TiC as shown here:
ELEM: Ti Ti V V Sr Fe Cr Mn C
TYPE: ANAL ANAL ANAL ANAL SPEC SPEC SPEC SPEC SPEC
BGDS: LIN EXP LIN EXP
TIME: --- 60.00 --- 60.00 --- --- --- --- ---
BEAM: --- 30.03 --- 30.03 --- --- --- --- ---
ELEM: Ti-D Ti V-D V Sr Fe Cr Mn C SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
174 --- 80.170 --- -.354 .000 .000 .000 .000 20.000 99.816
175 --- 80.007 --- -.351 .000 .000 .000 .000 20.000 99.656
176 --- 80.083 --- -.366 .000 .000 .000 .000 20.000 99.717
177 --- 80.442 --- -.372 .000 .000 .000 .000 20.000 100.070
178 --- 80.261 --- -.356 .000 .000 .000 .000 20.000 99.905
AVER: --- 80.193 --- -.360 .000 .000 .000 .000 20.000 99.833
SDEV: --- .169 --- .009 .000 .000 .000 .000 .000 .163
SERR: --- .075 --- .004 .000 .000 .000 .000 .000
%RSD: --- .21 --- -2.41 .00 .00 .00 .00 .00
Clearly a blank correction is required to fix this, but why is it so bloody horrible? I even tried the original Gilfrich interference correction method and it's only different by 30 PPM (0.003) which is less than the variance so it's not a matrix effect.
Help!
Quote from: Brian Joy on September 19, 2021, 10:34:19 AM
The Ti K absorption edge produces a discontinuity in the continuum, especially when the compound is ~99 wt% TiO2. It must create problems for off-peak background measurement.
I know, that's what I thought too. But I get almost exactly the same results (only 10 PPM different!) using the MAN method as shown here looking at V Ka in TiC using LPET again:
St 674 Set 2 TiC (titanium carbide), Results in Elemental Weight Percents
ELEM: Ti Ti V V Sr Fe Cr Mn C
TYPE: ANAL ANAL ANAL ANAL SPEC SPEC SPEC SPEC SPEC
BGDS: MAN MAN MAN MAN
TIME: --- 60.00 --- 60.00 --- --- --- --- ---
BEAM: --- 30.03 --- 30.03 --- --- --- --- ---
ELEM: Ti-D Ti V-D V Sr Fe Cr Mn C SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
174 --- 80.171 --- -.350 .000 .000 .000 .000 20.000 99.820
175 --- 80.024 --- -.352 .000 .000 .000 .000 20.000 99.672
176 --- 80.081 --- -.371 .000 .000 .000 .000 20.000 99.710
177 --- 80.443 --- -.372 .000 .000 .000 .000 20.000 100.071
178 --- 80.268 --- -.352 .000 .000 .000 .000 20.000 99.916
AVER: --- 80.197 --- -.359 .000 .000 .000 .000 20.000 99.838
SDEV: --- .165 --- .011 .000 .000 .000 .000 .000 .161
SERR: --- .074 --- .005 .000 .000 .000 .000 .000
%RSD: --- .21 --- -3.05 .00 .00 .00 .00 .00
I'm really perplexed I have to say... all I can say for now is don't use the LPET crystals for trace V in Ti compounds without a suitable blank correction!
Sort of not surprising, but if I aggregate the data from the LiF and PET crystals we get this somewhat better results without a blank correction (but with an interference correction):
ELEM: Ti Ti V V Sr Fe Cr Mn C SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
174 79.950 .000 -.266 .000 .000 .000 .000 .000 20.000 99.684
175 79.868 .000 -.269 .000 .000 .000 .000 .000 20.000 99.600
176 79.903 .000 -.276 .000 .000 .000 .000 .000 20.000 99.627
177 80.240 .000 -.281 .000 .000 .000 .000 .000 20.000 99.959
178 80.106 .000 -.274 .000 .000 .000 .000 .000 20.000 99.832
AVER: 80.013 .000 -.273 .000 .000 .000 .000 .000 20.000 99.740
SDEV: .156 .000 .006 .000 .000 .000 .000 .000 .000 .152
SERR: .070 .000 .003 .000 .000 .000 .000 .000 .000
%RSD: .19 .0000 -2.16 .0000 .00 .00 .00 .00 .00
Then using the TiC standard acquired as an unknown (matrix matched ) blank but without the interference correction we get this:
ELEM: Ti Ti V V Sr Fe Cr Mn C SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
174 79.904 .000 .618 .000 .000 .000 .000 .000 20.000 100.522
175 79.823 .000 .612 .000 .000 .000 .000 .000 20.000 100.435
176 79.857 .000 .607 .000 .000 .000 .000 .000 20.000 100.464
177 80.193 .000 .618 .000 .000 .000 .000 .000 20.000 100.811
178 80.059 .000 .619 .000 .000 .000 .000 .000 20.000 100.678
AVER: 79.967 .000 .615 .000 .000 .000 .000 .000 20.000 100.582
SDEV: .155 .000 .005 .000 .000 .000 .000 .000 .000 .159
SERR: .069 .000 .002 .000 .000 .000 .000 .000 .000
%RSD: .19 .0000 .83 .0000 .00 .00 .00 .00 .00
So even worse.
But using the TiC standard acquired as an unknown (matrix matched) blank and also with the interference correction we get an almost reasonable result:
ELEM: Ti Ti V V Sr Fe Cr Mn C SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
174 79.935 .000 .023 .000 .000 .000 .000 .000 20.000 99.958
175 79.853 .000 .020 .000 .000 .000 .000 .000 20.000 99.873
176 79.888 .000 .013 .000 .000 .000 .000 .000 20.000 99.901
177 80.224 .000 .008 .000 .000 .000 .000 .000 20.000 100.233
178 80.091 .000 .015 .000 .000 .000 .000 .000 20.000 100.105
AVER: 79.998 .000 .016 .000 .000 .000 .000 .000 20.000 100.014
SDEV: .156 .000 .006 .000 .000 .000 .000 .000 .000 .152
SERR: .070 .000 .003 .000 .000 .000 .000 .000 .000
%RSD: .19 .0000 37.27 .0000 .00 .00 .00 .00 .00
I have to say I don't really understand these results...
Quote from: Probeman on September 19, 2021, 11:05:31 AM
I have to say I don't really understand these results...
Using LiF, the continuum intensity is very low near Ti Kβ (compared to PET) and varies
relatively linearly and with very small slope with respect to Bragg angle, even across the Ti K absorption edge. Although I haven't actually checked to verify this, peak:background at V Kα should be greater on LiF than PET. Further, the Ti K absorption edge will be more difficult to see using PET due to its poorer resolution than LiF. I never, ever use PET to analyze for vanadium in the presence of easily measurable titanium.
Looking at the spectra from the first post of this thread, aren't the interfering Ti Kb'' and Ti Kb5 emission lines coming from bonding shells?
I'd guess that would raise the question of suitability of e.g. TiC as an interference correction for TiO2 etc, as well as any issues from the proximity to the absorption edge.
Quote from: Brian Joy on September 19, 2021, 12:36:46 PM
Further, the Ti K absorption edge will be more difficult to see using PET due to its poorer resolution than LiF. I never, ever use PET to analyze for vanadium in the presence of easily measurable titanium.
Of course I realize everything you are saying. I'm *not* saying one should use a PET crystal for this interference. I'm simply performing a "failure mode" analysis using the PET. As they (don't) say: "Failure is an (analysis) option"! ;D
It's a worst case scenario for the interference and blank corrections. I'm just trying to understand why we're still off by 160 PPM (+/- 60 PPM) even with both corrections turned on...
Quote from: JonF on September 19, 2021, 12:55:12 PM
Looking at the spectra from the first post of this thread, aren't the interfering Ti Kb'' and Ti Kb5 emission lines coming from bonding shells?
I'd guess that would raise the question of suitability of e.g. TiC as an interference correction for TiO2 etc, as well as any issues from the proximity to the absorption edge.
Oh, good point!
OK, changing the interference standard to TiC, we now get this (without the blank correction) for the unknown blank TiC (because otherwise we'd be analyzing the interference standard assigned to itself):
ELEM: Ti Ti V V Sr Fe Cr Mn C SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
162 80.067 .000 -.018 .000 .000 .000 .000 .000 20.000 100.050
163 80.025 .000 -.005 .000 .000 .000 .000 .000 20.000 100.019
164 79.850 .000 -.002 .000 .000 .000 .000 .000 20.000 99.849
165 79.906 .000 -.001 .000 .000 .000 .000 .000 20.000 99.905
166 79.749 .000 -.016 .000 .000 .000 .000 .000 20.000 99.734
167 80.031 .000 .012 .000 .000 .000 .000 .000 20.000 100.043
AVER: 79.938 .000 -.005 .000 .000 .000 .000 .000 20.000 99.933
SDEV: .124 .000 .011 .000 .000 .000 .000 .000 .000 .127
SERR: .051 .000 .004 .000 .000 .000 .000 .000 .000
%RSD: .16 .0000 -220.33 .0000 .00 .00 .00 .00 .00
STDS: 922 0 923 0 --- --- --- --- ---
And with both the interference and blank corrections turned on we now get this for the standard TiC (again similarly so we're not analyzing the blank unknown assigned to itself):
ELEM: Ti Ti V V Sr Fe Cr Mn C SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
162 80.067 .000 -.013 .000 .000 .000 .000 .000 20.000 100.054
163 80.024 .000 .000 .000 .000 .000 .000 .000 20.000 100.024
164 79.850 .000 .003 .000 .000 .000 .000 .000 20.000 99.853
165 79.906 .000 .004 .000 .000 .000 .000 .000 20.000 99.909
166 79.749 .000 -.011 .000 .000 .000 .000 .000 20.000 99.738
167 80.031 .000 .017 .000 .000 .000 .000 .000 20.000 100.048
AVER: 79.938 .000 .000 .000 .000 .000 .000 .000 20.000 99.938
SDEV: .124 .000 .011 .000 .000 .000 .000 .000 .000 .127
SERR: .051 .000 .004 .000 .000 .000 .000 .000 .000
%RSD: .16 .0000 ---- .0000 .00 .00 .00 .00 .00
STDS: 922 0 923 0 --- --- --- --- ---
Both still using the TiO2 as the primary standard for Ti and V2O3 as the primary standard for V, because you know, standards don't really have much of an effect for trace elements! It's all in the background measurement and corrections...
Thanks, Jon!
So it would appear that the differences in intensities due to the bonding between these Ti satellite lines in TiO2 and TiC are on the order of 160 PPM or so. I can buy that.
Here are the V Ka scans on SrTiO3 for LiF and next PET:
(https://smf.probesoftware.com/gallery/395_19_09_21_3_14_47.png)
(https://smf.probesoftware.com/gallery/395_19_09_21_3_15_00.png)
Does it make any sense to say that the interference correction deals with the Ti Kb overlaps and the blank correction deals with the interpolation across the Ti K absorption edge?
Quote from: Probeman on September 19, 2021, 03:21:25 PM
Does it make any sense to say that the interference correction deals with the Ti Kb overlaps and the blank correction deals with the interpolation across the Ti K absorption edge?
But an absorption edge is always present on the low-Bragg-angle side of any Kβ peak.
Also, how likely is the bonding environment to affect positions of TiKβ
1,3 (IUPAC: K-M
3,2), TiKβ
5, or any satellites? Positions/shapes of K peaks and satellites certainly vary with bonding environment for elements of lower atomic number (at least up through sulfur), but transitions involving the Ti K shell are relatively isolated from those effects. Can you show that the Ti Kβ satellites are in noticeably different positions for TiC than for TiO
2? I haven't checked this (but I don't have TiC on hand).
Quote from: Brian Joy on September 19, 2021, 03:59:15 PM
Quote from: Probeman on September 19, 2021, 03:21:25 PM
Does it make any sense to say that the interference correction deals with the Ti Kb overlaps and the blank correction deals with the interpolation across the Ti K absorption edge?
But an absorption edge is always present on the low-Bragg-angle side of any Kβ peak.
Of course, but the example we're using in this case is V Ka across the Ti K edge.
Quote from: Brian Joy on September 19, 2021, 03:59:15 PM
Also, how likely is the bonding environment to affect positions of TiKβ1,3 (IUPAC: K-M3,2), TiKβ5, or any satellites? Positions/shapes of K peaks and satellites certainly vary with bonding environment for elements of lower atomic number (at least up through sulfur), but the Ti K shell is relatively isolated from those effects. Can you show that the Ti Kβ satellites are in noticeably different positions for TiC than for TiO2? I haven't checked this (but I don't have TiC on hand).
It's a good question and I don't know the answer.
But that fact that between using TiO2 and TiC as the interference standard, the intensity difference was only 160 PPM seems "relatively isolated" to me.
Quote from: Probeman on September 19, 2021, 04:45:19 PM
It's a good question and I don't know the answer.
But that fact that between using TiO2 and TiC as the interference standard, the intensity difference was only 160 PPM seems "relatively isolated" to me.
Now I'm really curious about this. I might have time tomorrow to do detailed wavelength scans around Ti Kβ for both Ti metal and synthetic TiO
2 and then overlay the plots after normalizing to the height of Ti Kβ
1,3.
I've done this sort of test before with elemental Si versus SiO
2 (and silicates in general) using PET. The positions and intensities of the Si Kβ satellites are affected strongly by the electronic environment. Unfortunately, one of those satellites causes problems in locating a suitable low-angle background offset position for Sr Lα (on PET). The database positions for the satellites are certainly those for elemental Si.
Quote from: Brian Joy on September 19, 2021, 08:38:28 PM
Quote from: Probeman on September 19, 2021, 04:45:19 PM
It's a good question and I don't know the answer.
But that fact that between using TiO2 and TiC as the interference standard, the intensity difference was only 160 PPM seems "relatively isolated" to me.
Now I'm really curious about this. I might have time tomorrow to do detailed wavelength scans around Ti Kβ for both Ti metal and synthetic TiO2 and then overlay the plots after normalizing to the height of Ti Kβ1,3.
I think those detailed wavelength scans around the Ti Kb satellites in the V Ka position should be quite revealing, one way or another!
Doing some quick googling around, I've overlaid some (open access) Ti K XANES spectra over the Ti Kb emission scan from the first post:
(https://smf.probesoftware.com/gallery/796_20_09_21_2_54_51.jpeg)
The main thing that occurs to me is that although there are a lot of post/pre edge structures (including a dip in the TiC XANES profile at ~ John's low background position at ~61320/171.7 mm/5.02 keV, TiC spectra not shown), there doesn't appear to be anything significant over the V Ka peak position (although that is extrapolating to the low energy side of the XANES profiles).
Quote from: Brian Joy on September 19, 2021, 03:59:15 PM
Also, how likely is the bonding environment to affect positions of TiKβ1,3 (IUPAC: K-M3,2), TiKβ5, or any satellites? Positions/shapes of K peaks and satellites certainly vary with bonding environment for elements of lower atomic number (at least up through sulfur), but transitions involving the Ti K shell are relatively isolated from those effects. Can you show that the Ti Kβ satellites are in noticeably different positions for TiC than for TiO2? I haven't checked this (but I don't have TiC on hand).
The K shell of the 3d TMs is certainly isolated, but the Ti Kb'' and Ti Kb
2,5 are valence to core transitions coming in from the 3d (M) shell as described by Castillo et al (2020) (https://doi.org/10.1002/anie.202003621 (https://doi.org/10.1002/anie.202003621), also open access). These are likely to wander all over the show, both in terms of position (e.g. quantized energy difference) and intensity (e.g. emission probability). How much of all this we can see using our probes is anyone's guess, but it is otherwise a bit coincidental that the Ti interference on V Ka is seemingly on top of these valence-to-core emissions.
(https://onlinelibrary.wiley.com/cms/asset/7568b4be-5ed9-4f14-afd8-300197b98588/anie202003621-fig-0002-m.jpg)
To try and explain more what I'm thinking, I think that the background (whether off peak or MAN) and blank corrections are essentially giving us the green line from the second plot:
(https://smf.probesoftware.com/gallery/381_16_09_21_12_41_39.png)
Then from that V Ka1 we're subtracting the Ti Kb2,5 and Ti Kb'' contributions plus the Ti Kb1,3 shoulder.
My concern is that the Kb2,5 and Kb'' intensities that are being subtracted are only applicable to similar (same?) chemical species due to them originating from bonding shell environments, resulting in either an under- or over-correction (depending on what we're measuring e.g. TiO2 and what we're using as an interference standard e.g. TiC, and therefore contribution of the Ti to the V Ka emission).
Moving then on to other Ti species, is the TiO2- or TiC-determined TiKb2,5 and Ti Kb'' interference measurement going to correct by the right amount?
Quote from: JonF on September 20, 2021, 03:26:16 AM
I think those detailed wavelength scans around the Ti Kb satellites in the V Ka position should be quite revealing, one way or another!
Hi Jon,
Don't forget that it's federal election day in Canada! See how your favourite candidate has done: https://www.cbc.ca/news
Below are some near-edge scans of Ti metal and synthetic TiO
2. In each case, I've normalized the scan to the respective height of Ti Kβ
1,3. The relative intensities of Ti Kβ
5 and those of the satellites appear to be variable depending on the electronic environment. In particular, Ti SKβ'' is obvious in the TiO
2 scan, but not in the Ti metal scan. Note that the Ti Kβ
5 peak appears in essentially the same position in both materials (or at least the difference is undetectable).
(https://smf.probesoftware.com/gallery/381_20_09_21_12_40_34.png)
Also, here is an old set of scans of elemental Si and SiO
2 (not normalized). Note the prominence of a satellite -- Si SKβ'? -- in SiO
2 at ~218.3 mm, only about 1.5 mm below the position of Sr Lα
1,2.
(https://smf.probesoftware.com/gallery/381_20_09_21_12_41_18.png)
I ran some additional high precision (15 keV, 50 nA, 10 um, 100 seconds per point, 400 points) scans on both LLIF and LPET crystals. Here are the LLIF scans for Va Ka on both TiO2 and TiC normalized to the Ti Kb:
(https://smf.probesoftware.com/gallery/395_24_09_21_10_11_29.png)
and here for LPET:
(https://smf.probesoftware.com/gallery/395_24_09_21_10_11_45.png)
So I don't understand completely what is going on but here's a few observations regrading these interferences/blank corrections when analyzing TiC using TiO2 for both the primary standard and for the interference standard for the quantitative interference correction... it's amazing it works as well as it does! ;D
First here we have no interference or blank corrections using only LIF crystals on TiC:
ELEM: Ti Ti-D V V-D Sr Fe Cr Mn C SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
162 78.759 --- .725 --- .000 .000 .000 .000 20.000 99.484
163 78.540 --- .720 --- .000 .000 .000 .000 20.000 99.260
164 78.196 --- .723 --- .000 .000 .000 .000 20.000 98.919
165 78.437 --- .737 --- .000 .000 .000 .000 20.000 99.174
166 78.628 --- .720 --- .000 .000 .000 .000 20.000 99.348
167 78.765 --- .701 --- .000 .000 .000 .000 20.000 99.466
AVER: 78.554 --- .721 --- .000 .000 .000 .000 20.000 99.275
SDEV: .216 --- .012 --- .000 .000 .000 .000 .000 .211
SERR: .088 --- .005 --- .000 .000 .000 .000 .000
%RSD: .28 --- 1.63 --- .00 .00 .00 .00 .00
STDS: 922 --- 923 --- --- --- --- --- ---
If we turn on the interference correction using TiO2 as our interference standard only we get this:
ELEM: Ti Ti V V Sr Fe Cr Mn C
TYPE: ANAL ANAL ANAL ANAL SPEC SPEC SPEC SPEC SPEC
BGDS: LIN EXP LIN EXP
TIME: 60.00 --- 60.00 --- --- --- --- --- ---
BEAM: 30.03 --- 30.03 --- --- --- --- --- ---
ELEM: Ti Ti-D V V-D Sr Fe Cr Mn C SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
162 78.797 --- .008 --- .000 .000 .000 .000 20.000 98.805
163 78.577 --- .005 --- .000 .000 .000 .000 20.000 98.583
164 78.233 --- .011 --- .000 .000 .000 .000 20.000 98.245
165 78.474 --- .024 --- .000 .000 .000 .000 20.000 98.498
166 78.665 --- .004 --- .000 .000 .000 .000 20.000 98.670
167 78.803 --- -.016 --- .000 .000 .000 .000 20.000 98.787
AVER: 78.592 --- .006 --- .000 .000 .000 .000 20.000 98.598
SDEV: .216 --- .013 --- .000 .000 .000 .000 .000 .209
SERR: .088 --- .005 --- .000 .000 .000 .000 .000
%RSD: .28 --- 211.68 --- .00 .00 .00 .00 .00
STDS: 922 --- 923 --- --- --- --- --- ---
The vanadium is within a standard deviation. One could also simply apply the TiC standard (acquired as an unknown) as a blank without an interference correction as seen here:
ELEM: Ti Ti-D V V-D Sr Fe Cr Mn C SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
174 78.239 --- .012 --- .000 .000 .000 .000 20.000 98.252
175 78.794 --- .003 --- .000 .000 .000 .000 20.000 98.796
176 78.508 --- .017 --- .000 .000 .000 .000 20.000 98.525
177 78.669 --- .013 --- .000 .000 .000 .000 20.000 98.682
178 78.899 --- -.005 --- .000 .000 .000 .000 20.000 98.895
AVER: 78.622 --- .008 --- .000 .000 .000 .000 20.000 98.630
SDEV: .259 --- .009 --- .000 .000 .000 .000 .000 .252
SERR: .116 --- .004 --- .000 .000 .000 .000 .000
%RSD: .33 --- 109.73 --- .00 .00 .00 .00 .00
PUBL: 80.000 n.a. n.a. n.a. n.a. n.a. n.a. n.a. 20.000 100.000
%VAR: -1.72 --- --- --- --- --- --- --- .00
DIFF: -1.378 --- --- --- --- --- --- --- .000
STDS: 922 --- 923 --- --- --- --- --- ---
Also within a standard deviation. In this case either the interference correction or the blank correction appear to work equally well.
Now let's do a "failure mode" analysis on PET crystals! Again, not recommended, but an interesting failure mode test. Here is the TiC without an interference correction or a blank correction:
ELEM: Ti-D Ti V-D V Sr Fe Cr Mn C SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
162 --- 80.029 --- 3.952 .000 .000 .000 .000 20.000 103.980
163 --- 80.008 --- 3.968 .000 .000 .000 .000 20.000 103.977
164 --- 79.856 --- 3.965 .000 .000 .000 .000 20.000 103.821
165 --- 79.888 --- 3.966 .000 .000 .000 .000 20.000 103.854
166 --- 79.687 --- 3.947 .000 .000 .000 .000 20.000 103.634
167 --- 79.986 --- 4.003 .000 .000 .000 .000 20.000 103.989
AVER: --- 79.909 --- 3.967 .000 .000 .000 .000 20.000 103.876
SDEV: --- .129 --- .020 .000 .000 .000 .000 .000 .139
SERR: --- .053 --- .008 .000 .000 .000 .000 .000
%RSD: --- .16 --- .50 .00 .00 .00 .00 .00
STDS: --- 922 --- 923 --- --- --- --- ---
That's a big interference! Now let's turn on the interference correction using TiO2 as the interference standard:
ELEM: Ti-D Ti V-D V Sr Fe Cr Mn C SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
162 --- 80.229 --- -.030 .000 .000 .000 .000 20.000 100.199
163 --- 80.209 --- -.014 .000 .000 .000 .000 20.000 100.195
164 --- 80.056 --- -.012 .000 .000 .000 .000 20.000 100.044
165 --- 80.088 --- -.014 .000 .000 .000 .000 20.000 100.075
166 --- 79.887 --- -.025 .000 .000 .000 .000 20.000 99.862
167 --- 80.187 --- .014 .000 .000 .000 .000 20.000 100.202
AVER: --- 80.110 --- -.014 .000 .000 .000 .000 20.000 100.096
SDEV: --- .129 --- .015 .000 .000 .000 .000 .000 .134
SERR: --- .053 --- .006 .000 .000 .000 .000 .000
%RSD: --- .16 --- -114.32 .00 .00 .00 .00 .00
STDS: --- 922 --- 923 --- --- --- --- ---
A bit of an over correction, but still within a standard deviation! Now just the blank correction using TiC as the blank:
ELEM: Ti-D Ti V-D V Sr Fe Cr Mn C SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
174 --- 80.149 --- .041 .000 .000 .000 .000 20.000 100.191
175 --- 79.987 --- .036 .000 .000 .000 .000 20.000 100.023
176 --- 80.062 --- .026 .000 .000 .000 .000 20.000 100.088
177 --- 80.420 --- .040 .000 .000 .000 .000 20.000 100.461
178 --- 80.240 --- .047 .000 .000 .000 .000 20.000 100.287
AVER: --- 80.172 --- .038 .000 .000 .000 .000 20.000 100.210
SDEV: --- .168 --- .008 .000 .000 .000 .000 .000 .172
SERR: --- .075 --- .003 .000 .000 .000 .000 .000
%RSD: --- .21 --- 20.47 .00 .00 .00 .00 .00
PUBL: n.a. 80.000 n.a. n.a. n.a. n.a. n.a. n.a. 20.000 100.000
%VAR: --- .21 --- --- --- --- --- --- .00
DIFF: --- .172 --- --- --- --- --- --- .000
STDS: --- 922 --- 923 --- --- --- --- ---
Not as good as the interference correction. Let's try turning both on! First the software warns us with this message:
(https://smf.probesoftware.com/gallery/395_24_09_21_10_27_34.png)
and here are the results with both corrections turned on:
ELEM: Ti-D Ti V-D V Sr Fe Cr Mn C SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
174 --- 80.169 --- -.341 .000 .000 .000 .000 20.000 99.829
175 --- 80.007 --- -.338 .000 .000 .000 .000 20.000 99.669
176 --- 80.082 --- -.353 .000 .000 .000 .000 20.000 99.729
177 --- 80.441 --- -.358 .000 .000 .000 .000 20.000 100.083
178 --- 80.261 --- -.343 .000 .000 .000 .000 20.000 99.918
AVER: --- 80.192 --- -.346 .000 .000 .000 .000 20.000 99.846
SDEV: --- .169 --- .009 .000 .000 .000 .000 .000 .163
SERR: --- .075 --- .004 .000 .000 .000 .000 .000
%RSD: --- .21 --- -2.51 .00 .00 .00 .00 .00
PUBL: n.a. 80.000 n.a. n.a. n.a. n.a. n.a. n.a. 20.000 100.000
%VAR: --- .24 --- --- --- --- --- --- .00
DIFF: --- .192 --- --- --- --- --- --- .000
STDS: --- 922 --- 923 --- --- --- --- ---
Indeed an over correction!
I'm still trying to understand all of these implications, but it seems to me that the interference correction, because it is multiplicative, is best applied to artifacts that scale with concentration, while the blank correction, because it is subtractive, is best applied to artifacts that are more constant, for example continuum artifacts.
Just to finish up here is the LiF analysis with both the interference and blank corrections turned on:
ELEM: Ti Ti V V Sr Fe Cr Mn C
TYPE: ANAL ANAL ANAL ANAL SPEC SPEC SPEC SPEC SPEC
BGDS: LIN EXP LIN EXP
TIME: 60.00 --- 60.00 --- --- --- --- --- ---
BEAM: 30.03 --- 30.03 --- --- --- --- --- ---
ELEM: Ti Ti-D V V-D Sr Fe Cr Mn C SUM
XRAY: (ka) (ka) (ka) (ka) () () () () ()
174 78.239 --- .014 --- .000 .000 .000 .000 20.000 98.253
175 78.794 --- -.001 --- .000 .000 .000 .000 20.000 98.793
176 78.508 --- .016 --- .000 .000 .000 .000 20.000 98.524
177 78.669 --- .010 --- .000 .000 .000 .000 20.000 98.679
178 78.900 --- -.010 --- .000 .000 .000 .000 20.000 98.890
AVER: 78.622 --- .006 --- .000 .000 .000 .000 20.000 98.628
SDEV: .259 --- .011 --- .000 .000 .000 .000 .000 .250
SERR: .116 --- .005 --- .000 .000 .000 .000 .000
%RSD: .33 --- 190.48 --- .00 .00 .00 .00 .00
PUBL: 80.000 n.a. n.a. n.a. n.a. n.a. n.a. n.a. 20.000 100.000
%VAR: -1.72 --- --- --- --- --- --- --- .00
DIFF: -1.378 --- --- --- --- --- --- --- .000
STDS: 922 --- 923 --- --- --- --- --- ---
STKF: .5552 --- .6328 --- --- --- --- --- ---
STCT: 45.56 --- 262.26 --- --- --- --- --- ---
UNKF: .7527 --- .0001 --- --- --- --- --- ---
UNCT: 61.78 --- .02 --- --- --- --- --- ---
UNBG: .20 --- .63 --- --- --- --- --- ---
ZCOR: 1.0445 --- 1.0666 --- --- --- --- --- ---
KRAW: 1.3558 --- .0001 --- --- --- --- --- ---
PKBG: 309.56 --- 1.04 --- --- --- --- --- ---
INT%: ---- --- -98.39 --- --- --- --- --- ---
BLNK#: ---- --- 3 --- --- --- --- --- ---
BLNKL: ---- --- .000000 --- --- --- --- --- ---
BLNKV: ---- --- .006107 --- --- --- --- --- ---
This does not appear to result in an over correction, I suspect because the blank correction level is only 60 PPM.
Just to follow up, here's high precision scans for Ti metal, TiO2, TiC and SrTiO3:
(https://smf.probesoftware.com/gallery/395_25_09_21_8_54_29.png)
all normalized to the Ti Kb peak. And here a bit more zoomed in:
(https://smf.probesoftware.com/gallery/395_25_09_21_8_54_45.png)
Before I ramble on, I'll add the caveat that this is probably only applicable in extreme circumstances of measuring trace V in Ti-rich or Cr-rich samples (otherwise, just measure the V Kb er... the Kb
1,3!), and is mostly playing around in the noise, but I reckon its interesting theoretically at least.
I think the problem is with this bit:
Quote from: Probeman on September 24, 2021, 10:47:25 AM
analyzing TiC [for V Ka] using TiO2 for both the primary standard and for the interference standard
The Ti Ka in TiC should be fine to use TiO2 (other than matrix mismatch), because the Ka results from a core to core transition (2p to 1s), but the Ti interference on the V Ka position is from the Ti Kb
2,5 and Ti Kb'' (with a little bit of Ti Kb
1,3 tail), both of which arise from relaxation to a fixed (ish) core level from the
molecular (note: not atomic) orbitals, the exact energy of which (and therefore the subsequent emission energy) is dependent on the counterion (e.g. C, O in this case) as well as the probability that the electron is even there at any given moment (e.g. the intensity). The Ti Kb'' results from relaxation from the O (or C) 2s and the Ti Kb
2,5 from the mixing of the Ti 3d and O 2p levels.
This is highlighted in Brian's high resolution scans between TiO2 and Ti metal with the absence of the Ti Kb'' in the Ti metal (there is no O or C 2s there!) as well as the change in relative intensity of the Ti Kb
2,5, and also in John's scans between TiC and TiO2 where the peak profile around the V Ka position is different (but the Ti Kb'' is present, just at a different energy and intensity corresponding to O and C 2s energies relative to Ti 1s).
These scans are telling us that we can't "cross-standardise" for the blank or interference correction, as the interference is species specific e.g. we can't use the Ti metal as an interference for V Ka in TiO2 as one of the major Ti interference peaks (the Kb'') isn't even present in Ti metal!
Looking at the data, it's apparent than an interference correction is needed (~7200 ppm V measured). Using TiO2 as the interference standard for TiC gives us pretty close to the right answer, but the variance in the data set (between 240 ppm to -160 ppm) is pretty large - I can guess this isn't a trace element setup - and the TiC and TiO2 emission profiles fortuitously cross over close to the V Ka1 to minimise the issue (I did say we were mostly playing in the noise!). I imagine that the wheels would fall off if you try assigning the Ti interference on V Ka to Ti metal.
I guess there's a rule of thumb that (at least for emission concerning valence shell transitions), the interference and/or blank standard also needs to be the same material as the unknown.