Questions about MAN background use

[Probeman]

Thanks. I get you where the average atomic number is constant (as in a single phase) so we don't have to correct for changing atomic number within the map we can use a single MAN standard. With best MAN data given where atomic number of MAN standard is same as unknown.

By using even a single MAN standard with similar atomic number (as is the case for most silicates/carbonate standards) we improve the quantification compared to no background. The error due to difference in atomic number of MAN standard and unknown is much smaller than the error with no background.

A good compromise for major elements where p/b ratio is large and background is small % (<1%) of total counts?

Hi Ben,
Yes that is correct if you are just measuring trace elements and none of the matrix elements. Of course you can't use a silicate to measure the background for Si ka!

But, if you are measuring just traces in silicates or carbonates, you've already measured a bunch of "on-peak" or MAN backgrounds on the standards you are using for your trace elements, e.g., Fe in TiO2.

So, even if you used off-peak backgrounds for your standard calibration, and you plan on using MAN backgrounds for your unknown quant x-ray mapping runs, you can still use those off-peak measured standards as backgrounds for the MAN calibration.  This involves using the Analytical | Use Off-Peak Elements For MAN Fit menu as described here:

http://probesoftware.com/smf/index.php?topic=4.msg189#msg189

[John Donovan]

In case anyone is interested, I've attached a pdf of the trace MAN presentation I gave at the EPMA 2016 topical conference this week in Madison (remember, you have to be logged in to see attachments).

The full paper will be out in the Aug issue of the Amer. Min. this year.

[Probeman]

Here's a couple of MAN plots from my trace zircon run posted here:

http://probesoftware.com/smf/index.php?topic=73.msg5130#msg5130

In these MAN plots of the P ka line, here is the plot with the defaults assigned by the program:



Note that P plots well above the trend.  Quantifying this amount shows an apparent 220 PPM of P in zircon, but is it real?

That is there is either a trace amount of phosphorus in this synthetic zircon or there is a spectral interference from Si or Zr. Since this is a synthetic zircon from Oak Ridge and we know it is very pure, we can check for nominal interferences using the Standard Assignments dialog as seen here:



And in fact there is a very small interference from the Zr La line, but it's a big emission line so it doesn't take much of a tail to create an apparent 220 PPM of P.

Once we remove the zircon standard from the MAN fit we obtain this plot:



And we are good. Remember, an artifact like this can be corrected for using the normal interference correction in PFE, or we can assign a blank correction (assuming we have a spectroscopically pure zircon standard- or at least one that is well characterized for trace phosphorus using a technique other than EPMA) to deal with it.  Remember, you should not assign both a spectral interference and a blank correction as you will get a "double correction". Fortunately, PFE will remind us that this is a no-no!
john

[John Donovan]

1) Is it possible to easily extract the raw data behind MAN (i.e. the standard intensities and Z-bar values)? The new graphics are very nice, but being able to extract the raw data to plot up off-line would be very useful for figures/papers/posters/etc. I realize I can export the count rates for the standards from the "Output" menu, and then look up the Z-bar values in the standard database, but... well, I'm lazy.

Hi Owen,
I'm lazy too. That is why the Output | Save Custom Output Format #8 (MAN) already outputs the standard intensities and zbars.

2) This is most likely operator error on my part, but is there a reason the last element in the MAN list reverts to a curved fit, even when you've told it to force the straight-line fit?

To explain further, I open the "Assign MAN Fits" window, click the last element, and click "Force Straight Line Fit", which does its job nicely. Then I hit OK, and the dialog closes.

Well you do realize that one needs to check this "Force Straight Line Fit" checkbox and click the Update Fit button for each element that you want to force a straight line fit for, if you want it to stick...
john

[John Donovan]

I realize this may seem like a nitpick, but I caught this while I was reducing some data, and couldn't figure out why the numbers for one element would sometimes change without me (seemingly) doing anything. It's easy to do unwittingly.

Yes, very helpful. 

It's clearly a small bug.  I will squash it tomorrow!
john

[John Donovan]

Hi Owen,
OK.  The fix for that last MAN fit assignment glitch is fixed and ready to download the latest PFE.

It was subtle...  had to do with the order things are loaded!  But it *only* affected the last element for this reason!
john

[John Donovan]

Hi Owen,
OK.  The fix for that last MAN fit assignment glitch is fixed and ready to download the latest PFE.

It was subtle...  had to do with the order things are loaded!  But it *only* affected the last element for this reason!
john

Awesome! Thanks much!

No worries, thanks for the excellent beta testing report!  It's a lot easier to reproduce issues when I get a detailed description!   

[Julien]

I really enjoy using the MAN, really! However, there is a series of error message that really starts to annoy me. The problem occurs when a lot of different standards are loaded in the run and the MAN has not been acquired in all of them. Whereas I do acknowledge and appreciate that the error appears (it can be legit in some case), it get really really really annoying when the same error repeat itself over 50 times for 12 elements (and ~20 standards). Please, please, please... can we find a better way to list this, e.g., buffer in a memory all the problematic standards / element that have missing data, and then maybe simply report it in the log window?

Second, I run into a big problem that actually resulted in a totally screwed up MDB file where I cannot use the MAN anymore (so as all my unknown are acquired with MAN I basically cannot reprocess my data anymore...). The issue started happening when I decided to acquire a new set of MAN acquisition just for the element mapping I was performing for the same user. The difference with my previous MAN acquisition was that I moved the Si Ka from a TAP (used for quant) to a PET (to enable mapping along with Al, Mg [TAP], K [PET] and Fe [LiF]). Ever since I do have this new calibration, calling the assign MAN routine returns me absolutely... nothing (i.e., PfE cannot find any MAN acquisition for any standard, and I know this is not true). To further complicate that story, my latest standardization and MAN acquisition on standard included two column conditions (15 and 10 keV). Clearing the MAN assignment and re-doing everything does not solve the problem. Disabling a set of standard and keeping only the one I need does not help neither. Exporting the results into a new file (and importing the std associate to the mapping setting only) does not solve the problem neither. My ultimate solution: use my backup before the file was screwed up and re-acquire again my standards in, this time, a NEW file. I guess, this is my fault, as I should have prepared a new sample right away for this new setting, but I was hoping to continue using the other MAN assignment for Al, Mg, K and Fe, which had not changed.

Is there a solution to fix this problem? I cannot open the MDB file and manually delete the "faulty" standard acquisitions as I only have access to the newest Microsoft Access software (which cannot read anymore the MDB file format). The file is too big to be attached on this forum, but I can send you (JD) a copy by email.

Best,

Julien

[John Donovan]

I really enjoy using the MAN, really! However, there is a series of error message that really starts to annoy me. The problem occurs when a lot of different standards are loaded in the run and the MAN has not been acquired in all of them. Whereas I do acknowledge and appreciate that the error appears (it can be legit in some case), it get really really really annoying when the same error repeat itself over 50 times for 12 elements (and ~20 standards). Please, please, please... can we find a better way to list this, e.g., buffer in a memory all the problematic standards / element that have missing data, and then maybe simply report it in the log window?

Sorry you are so frustrated. Adding another button to cancel out should be feasible. Note that if you load different standards into a new run you should probably first clear the MAN assignments and then you shouldn't get all these errors.

Is there a solution to fix this problem? I cannot open the MDB file and manually delete the "faulty" standard acquisitions as I only have access to the newest Microsoft Access software (which cannot read anymore the MDB file format). The file is too big to be attached on this forum, but I can send you (JD) a copy by email.

It's difficult to understand what you might have done here. Better send me the MDB file to look at.
john

[Julien]

Hi John,

Thanks for the quick response. This is not so urgent (and this is now the week-end and we probably all need a lot of rest after that week). I learnt from my mistakes. However, I was thinking the MAN code could handle the following situation (sorry for the vagueness of my previous post):

(1) The researcher wanted chlorite analysis. Easy. The day before their venue, I acquired all required elements that we agreed on the week before (Si, Al, Fe, Mn, Mg, Ca, Na, K, F and Cl) in several standards, all with MAN (no element with 2-pts bkg). The automated run I had to get the MAN on all my standards (maybe a little too many, but I’m still testing…) took 2-3 hours.

(2) Once they arrived, they also requested additional elements: Ba, V, Co, Ni and Zn. I didn't want to worry about setting right my background for these element that are expected to be minor (or maybe trace), and I also wanted to ease potential interference correction, two great reasons to opt for the MAN background correction. To avoid re-running all my standards with this now 2 to 3 minute long setup, I opt to just run it in 5 (new!) standards, for Ba (barite), Ni (pentlandite), Zn (sphalerite) and, V and Co (metals - I know, not ideal, but I’m doing with what I have right now...).

(3) So after that, I ended up with many standards that had no data for Ba, V, Co… and 5 other standards that had no data for Si, Al, Fe…

(4) At this point, I managed to get into the MAN assignment tool and set the assignment (after 50+ clicks on these error message). I guess an easy fix for this would be to generate ONE error for ALL elements / standards missing and have that reported at the end in the main log window of PfE (e.g., a red message).

(5) After this, the MAN was properly assigned and the treatment of the unknown analysis worked fine, we got all the data we needed for the day.

(6) Things got complicated during the evening. We opt to perform some quantitative mapping on these chlorite (for Si, Al, Mg, Fe and K). Based on my spectrometer setting, I was in need of putting Si on a PET crystal (the only two TAP reserved for Al and Mg). To enable the MAN correction, I had thus to reacquire MAN data that would include also Si on PET; I did this in a sub-set of my Si, Al, Fe, Mg and K standards. Stupidly enough I did that in the same MDB file...

(7) This is were the files started getting “bogus”. After this acquisition, I started having a bunch of errors than the MAN was not available for Al, or Si, or another element… To solve this error, I opt to clean all MAN assignment, and start from scratch. However, when I returned to the MAN assignment window (after many clicks), the MAN assignment constantly returned me an error that no MAN data were available, and this for every single element in the MAN assignment window. Also, Si is only listed once, whereas it should be listed twice (once for Si on TAP and one for Si on PET - actually there should even be a third entry, as I had also acquired MAN data in my standards for Si on PET at 10 keV (all other data were acquired at 15 keV).

I have sent you the good (early backup) and the bad file (after the latest std acquisition).

Again, no rush on this, I am just wondering why this has screwed up the file (so I won’t reproduce this), and if it is possible to fix this easily.

Best,

Julien

[John Donovan]

Hi Julien,
I will look at your file and see if I can handle this type of situation better.

I will only mention at this time that if I have a run with lot of MAN elements and I want to add some additional trace elements, I generally just add them as off-peak elements- though note that you need to make sure they are specified as off-peak both for both standards and unknowns, as seen in the Acquisition Options dialog.

I think something like the above will avoid the problems you are seeing. That said the software should be able to handle the situation you describe, so I will look into that this weekend. With the current software I think it's just a question of unselecting standards which do not have the MAN data acquired for those elements.
john

[John Donovan]

Hi Julien,
Well I wasn't sure I was going to be able to figure out what the issues were with this probe run file, because I have to hand it to you: you get the EPMA Grand Prize for most complicated probe run ever!



I mean, you have duplicate elements, at multiple keVs, using MAN backgrounds, aggregate intensities, with different element setups, etc.... I hardly knew where to start! Anyway, I managed to isolate the culprits and here is the summary of the bug fixes (from the version.txt file):

11/13/16   Fix several bugs in MAN fit code when duplicate elements at different operating voltages are
      present in the same run (Allaz).

Here is a screenshot of the new (and improved!) MAN Fit display dialog (note both 15 and 10 keV elements):



Below are two of your standards. First one at 15 keV:

St  340 Set   2 Pyrope, Results in Elemental Weight Percents
 
ELEM:       Al      Mg      Si       K      Fe      Ti      Cr      Mn      Ca       O
TYPE:     ANAL    ANAL    ANAL    ANAL    ANAL    SPEC    SPEC    SPEC    SPEC    CALC
BGDS:      MAN     MAN     MAN     MAN     MAN
MAN1:  1.28970 -.12378 .018498 -.38521 -.03082
MAN2:  .035652 .261638 .012660 .142803 .080721
MAN3:  .003343 -.00301 -.00016 -.00163 -.00074
ABS%:   -28.69  -30.48  -25.48   -5.67    -.14
TIME:    30.00   30.00   30.00   30.00   30.00     ---     ---     ---     ---     ---
BEAM:    19.86   19.86   19.86   19.86   19.86     ---     ---     ---     ---     ---
AGGR:                                              ---     ---     ---     ---     ---

ELEM:       Al      Mg      Si       K      Fe      Ti      Cr      Mn      Ca       O   SUM 
   251 11.5262 12.7897 19.4222  .00188 6.33455  .29975 1.40944  .24008 3.10892 44.7774 99.9101
   252 11.5370 12.7413 19.7032 -.00008 6.37568  .29975 1.40944  .24008 3.10892 45.0867 100.502
   253 11.5198 12.7502 19.4433 -.00427 6.40858  .29975 1.40944  .24008 3.10892 44.7897 99.9655
   254 11.5865 12.7641 19.6021  .00188 6.30480  .29975 1.40944  .24008 3.10892 45.0107 100.328
   255 11.5434 12.7980 19.3988  .00321 6.33253  .29975 1.40944  .24008 3.10892 44.7711 99.9051
   256 11.4746 12.7441 19.4013 -.00203 6.40277  .29975 1.40944  .24008 3.10892 44.6964 99.7753

AVER:  11.5312 12.7646 19.4952  .00010 6.35982    .300   1.409    .240   3.109  44.855 100.064
SDEV:   .03634  .02414  .12715  .00282  .04215    .000    .000    .000    .000    .155  .28413
SERR:   .01484  .00986  .05191  .00115  .01721  .00000  .00000  .00000  .00000  .06335
%RSD:   .31516  .18915  .65223 2853.97  .66281  .00000  .00000  .00000  .00001  .34593

PUBL:  11.4211 12.2716 19.3656    n.a. 6.80919  .29975 1.40944  .24008 3.10892 44.4140 99.3397
%VAR:      .96    4.02     .67     ---   -6.60     .00     .00     .00     .00     .99
DIFF:   .11012  .49296  .12953     --- -.44937  .00000  .00000  .00000  .00000  .44131
STDS:      325     336     301     334     326     ---     ---     ---     ---     ---

STKF:    .4390   .4784   .2543   .1130   .6544     ---     ---     ---     ---     ---
STCT:  1010.49 2735.00  119.94  243.57  431.67     ---     ---     ---     ---     ---

UNKF:    .0800   .0890   .1435   .0000   .0537     ---     ---     ---     ---     ---
UNCT:   184.05  508.70   67.71     .00   35.42     ---     ---     ---     ---     ---
UNBG:     1.57    1.81     .11    1.04     .84     ---     ---     ---     ---     ---

ZCOR:   1.4421  1.4344  1.3582  1.1253  1.1845     ---     ---     ---     ---     ---
KRAW:   .18214  .18600  .56454  .00001  .08204     ---     ---     ---     ---     ---
PKBG:  117.885 282.635 616.119 1.00184 43.3686     ---     ---     ---     ---     ---

And another at 10 keV:

St  336 Set   3 Periclase, Results in Elemental Weight Percents
 
ELEM:       Al      Mg      Si       K      Fe       O
TYPE:     ANAL    ANAL    ANAL    ANAL    ANAL    CALC
BGDS:      MAN     MAN     MAN     MAN     MAN
MAN1:  1.10474 .003876 .012899 -.10651 -.11700
MAN2:  .024212 .167921 .009920 .067070 .045766
MAN3:  .001162 -.00215 -.00012 -.00060 -.00051
ABS%:   -30.62  -10.37  -20.36   -2.37     .12
TIME:    30.00   30.00   30.00   30.00   30.00     ---
BEAM:    20.23   20.23   20.23   20.23   20.23     ---
AGGR:                                              ---

ELEM:       Al      Mg      Si       K      Fe       O   SUM 
   329 -.00400 60.2003  .00175  .00322  .04239 39.6411 99.8848
   330 -.01423 60.2350  .00515  .00404  .06666 39.6659 99.9625
   331 -.01595 60.3602 -.00681  .00431  .00401 39.7152 100.061
   332 -.01114 60.3954 -.00088  .00203  .14669 39.7898 100.322
   333 -.00462 60.3592 -.00599  .00016  .10331 39.7532 100.205
   334 -.01185 60.3800 -.01198  .00276  .07546 39.7462 100.181

AVER:  -.01030 60.3217 -.00313  .00275  .07309  39.719 100.103
SDEV:   .00495  .08242  .00628  .00152  .04918    .056  .16341
SERR:   .00202  .03365  .00257  .00062  .02008  .02297
%RSD:  -48.062  .13663 -200.83 55.1365 67.2864  .14164

PUBL:     n.a. 60.3027    n.a.    n.a.    n.a. 39.6973 100.000
%VAR:      ---   (.03)     ---     ---     ---     .05
DIFF:      ---   (.02)     ---     ---     ---  .02127
STDS:      325     336     301     334     326     ---

STKF:    .4702   .5285   .2806   .1146   .6410     ---
STCT:   602.80 1765.08   69.94  100.27   75.88     ---

UNKF:   -.0001   .5285   .0000   .0000   .0006     ---
UNCT:     -.09 1765.08    -.01     .02     .07     ---
UNBG:     1.03    1.36     .08     .51     .30     ---

ZCOR:   1.5250  1.1414  1.2958  1.1365  1.2571     ---
KRAW:  -.00014 1.00000 -.00009  .00021  .00091     ---
PKBG:   .91587 1296.33  .92694 1.04123 1.22577     ---

A couple of notes. First the code now displays and re-checks the fit of each MAN element when you click the OK button. Also, if you are in aggregate intensity mode, the MAN window only displays the first instance of the duplicate element. If you want to see the MAN fit for any subsequent duplicate elements, just unselect the Use Aggregate Intensity mode under the Analytical | Analysis Options menu dialog.

Whew!  In any event, the bottom line is that now Probe for EPMA shouold be able to handle any combination of element setups, with duplicate elements, at multiple keVs, for MAN background processing now.
john

PS For those that are interested, I've attached Julien's MDB file below (with his permission).

PPS This new software will allow one to handle multiple keVs in their MAN background fits for probe runs going back to v. 11.4.0, which is when I added the additional keV arrays for the MAN fit.

[John Donovan]

In going through the MAN fits in Julien's probe run, I noticed that some standards might have certain elements that are not reported in the standard.mdb compositional database.  Remember, the MAN background fit is a fast and easy way to check that your standards are as clean and complete as one would hope.  The outliers will tend to fall above the general trend line of the MAN fit, making them easy to spot.

Now some of these are definitely on-peak interferences, but some may be "contamination" in the sense that they are present- but not accounted for!  For example in the MAN fit for Cl Ka we see this plot:



And in fact when we analyze the standard (from the same MDB file as above):

St  328 Set   1 Kaersutite, Results in Elemental Weight Percents
 
ELEM:       Si      Al      Na      Mg       F      Ca      Ti      Cr       K      Cl      Fe      Mn       H       O
TYPE:     ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    ANAL    SPEC    CALC
BGDS:      MAN     MAN     MAN     MAN     MAN     MAN     MAN     MAN     MAN     MAN     MAN     MAN
MAN1:  .433228 -.69047 -.22037 -3.8524 -.53121 .458636 -.33698 -.45214 -.33213 -.05578 -.04689 -.11476
MAN2:  .260354 .402656 .195662 .737859 .126105 .092872 .287473 .475453 .137779 .046313 .083034 .060886
MAN3:  .000071 -.00552 -.00238 -.01295 -.00247 .000815 -.00163 -.00079 -.00152 -.00042 -.00079 -.00041
ABS%:   -22.83  -28.84  -49.17  -35.61  -74.17   -3.34   -2.50   -1.34   -4.96  -11.57    -.46    -.83
TIME:    30.00   30.00   20.00   20.00   20.00   30.00   30.00   20.00   20.00   20.00   30.00   30.00     ---     ---
BEAM:    20.01   20.01   20.01   20.01   20.01   20.01   20.01   20.01   20.01   20.01   20.01   20.01     ---     ---
AGGR:                                                                                                      ---     ---

ELEM:       Si      Al      Na      Mg       F      Ca      Ti      Cr       K      Cl      Fe      Mn       H       O   SUM 
    51 18.7167 6.47933 1.83938 7.97634  .33305 7.98541 3.10663 -.00252  .84801  .02933 8.83063  .12070  .23000 42.5990 99.0920
    52 18.7057 6.47333 1.86776 7.85883  .24068 7.91836 3.12160  .01332  .87714  .02290 9.10796  .11198  .23000 42.6275 99.1770
    53 18.4669 6.41391 1.85091 7.78733  .20441 7.86146 3.10923  .00973  .84554  .03115 9.73464  .12887  .23000 42.4083 99.0823
    54 18.7365 6.57265 1.90582 7.86262  .30850 7.89659 3.07578  .01559  .87882  .02731 9.06527  .11481  .23000 42.6877 99.3779
    55 18.8403 6.57865 1.85397 7.99179  .31942 7.90964 3.10957  .01488  .83560  .02806 8.94850  .12863  .23000 42.8628 99.6518

AVER:  18.6932 6.50357 1.86357 7.89538  .28121 7.91429 3.10456  .01020  .85702  .02775 9.13740  .12100    .230  42.637 99.2762
SDEV:   .13735  .07062  .02569  .08651  .05575  .04528  .01710  .00746  .01970  .00308  .35091  .00774    .000    .164  .24125
SERR:   .06143  .03158  .01149  .03869  .02493  .02025  .00765  .00334  .00881  .00138  .15693  .00346  .00000  .07328
%RSD:   .73478 1.08590 1.37868 1.09564 19.8258  .57212  .55081 73.1317 2.29834 11.0899 3.84039 6.40067  .00001  .38431

PUBL:  19.4000 6.30000 1.95000 7.64000  .14000 8.15000 3.01000    n.a.  .84000    n.a. 8.77000  .13000  .23000 43.1680 99.7280
%VAR:    -3.64    3.23   -4.43    3.34  100.86   -2.89    3.14     ---    2.03     ---    4.19   -6.92     .00   -1.23
DIFF:  -.70679  .20357 -.08643  .25538  .14121 -.23571  .09456     ---  .01702     ---  .36740 -.00900  .00000 -.53094
STDS:      301     325     301     336     349     322     344     319     334     350     326     342     ---     ---

STKF:    .2543   .4390   .0509   .4784   .0611   .1623   .5545   .2862   .1130   .0620   .6544   .2861     ---     ---
STCT:   588.46 1014.03  194.06 2765.22   18.32  402.37 1438.72  777.01  242.84   84.89  431.68  164.84     ---     ---

UNKF:    .1433   .0452   .0093   .0511   .0007   .0738   .0265   .0001   .0078   .0002   .0774   .0010     ---     ---
UNCT:   331.56  104.46   35.42  295.25     .22  182.89   68.80     .24   16.84     .32   51.04     .58     ---     ---
UNBG:     2.95    2.57     .98    2.28     .18    1.74    3.04    5.52    1.14     .42     .89     .60     ---     ---

ZCOR:   1.3048  1.4381  2.0061  1.5456  3.9095  1.0729  1.1709  1.1484  1.0941  1.1992  1.1808  1.1990     ---     ---
KRAW:   .56344  .10302  .18252  .10677  .01177  .45452  .04782  .00031  .06934  .00373  .11825  .00353     ---     ---
PKBG:  113.266 41.6888 37.2975 130.257 2.21103 105.973 23.5975 1.04375 15.7533 1.75341 58.0413 1.96671     ---     ---

we obtain about 270 PPM of Cl.
john

[Julien]

Many thanks, John! For the price - of course - that I gladly accept. However, this is not yet my most complicated run, you got to wait my new idea for fast, precise and accurate monazite analysis (and other REE minerals 30+ elements, expecting to use MAN, TDI, n-th point, multipoint bkg... Potentially also multiple analytical conditions (trace vs major) and use of EDS... This got to be causing other troubles, so get ready

And thanks A LOT for these fixes! Effectively it works great now!

About the Kaersutite standard, the MAN is here used on this secondary standards (and many many more) to indeed check for the presence of an unlisted element. My periclase for instance contains some Fe (not so much a surprise), but also Al (and maybe Si), around 130-180 ppm Al, and is clearly visible on the MAN plot (data from a "regular" TAP crystal)!



I might also remind other readers that peak interference will obviously also be a problem. I am here thinking of the analysis of REE minerals, for which multiple interferences exists and the MAN will pick it! And here is again another Wonderful MAN power: once you identified the peak interference, you can just use the data acquired on your standards for the MAN. No data are lost!

Let's recap:
- Identification of impurities or unrecognized element in standard at the ~100 ppm level maybe lower ( to check )
- Cut your analysis time in half
- Allow identification of peak interference, and unusable MAN bkg data due to this interference can then be use for the interference correction itself!
- No worry about potential interferences on background.

I still wonder what (a) the long term stability is, (b) what is the variability, and (c) what is the error on the calibration curve (it should be possible to calculate an error envelope on the MAN fitting line / curve, using the repeated background measurement on the standards). I am getting some nice data on the long term reproducibility as I type, I might one day share this... Just need time to compile a huge set of data covering 3 month of testing and many standards. There are still some behavior on the MAN fits I cannot explain with impurity in std or peak interference, notably on the REE business... Got some idea, though (problem of absorption edges in the standard?)... More to come soon - hopefully!

Cheers to the PfE Master!

Julien

[Probeman]

And thanks A LOT for these fixes! Effectively it works great now!

You are most welcome.  It is a pleasure to work with so many experts such as yourself.  As someone once said: it takes a village!   

I still wonder what (a) the long term stability is, (b) what is the variability, and (c) what is the error on the calibration curve (it should be possible to calculate an error envelope on the MAN fitting line / curve, using the repeated background measurement on the standards). I am getting some nice data on the long term reproducibility as I type, I might one day share this... Just need time to compile a huge set of data covering 3 month of testing and many standards. There are still some behavior on the MAN fits I cannot explain with impurity in std or peak interference, notably on the REE business... Got some idea, though (problem of absorption edges in the standard?)... More to come soon - hopefully!

The error on the MAN calibration curve regression is discussed in detail in my recent Amer. Min. paper here:

http://epmalab.uoregon.edu/publ/A%20new%20EPMA%20method%20for%20fast%20trace%20element%20analysis%20in%20simple%20matrices.pdf

However, I can summarize:

1. Because we generally only measure the standards for the MAN calibration curve once per analytical session or mapping run, the regression error on the MAN fit *must* be treated as an accuracy error, as opposed to a precision error.   Yes, if we remeasured the MAN regression curve for each point analysis or each mapping pixel, then we would need to include the MAN regression error as a precision issue.  But no one would ever re-run the MAN calibration for every analysis or pixel!  We need to think carefully about this as it is not an intuitive conclusion, but it is (surprisingly) correct.  If you don't agree, please read the above paper (see tables 3a, 3b and 3c in particular), and maybe also read this post here:

http://probesoftware.com/smf/index.php?topic=307.msg3190#msg3190

2. The stability of the measured continuum intensities over time are exceptionally good so far as I have seen, mostly because we are measuring the intensities at the on-peak positions when the element is *not* present. Therefore there is no peak, only a smooth x-ray continuum.

3. In fact, if one re-measures the MAN curve within a single probe run, any changes in the continuum intensities over time are automatically applied to the unknown samples using the built-in drift correction in PfE, just as the primary and interference standards are drift corrected with multiple standard sets! But since the MAN intensities are not actually on a peak (though they are *at* the peak position!), the stability is much better than the primary standards or the interference standards. Especially better than the interference standard intensities, where the interfering intensities are often measured on the *side* of a peak (causing the the spectral overlap!) 

4. That said, a difference in detector bias voltage or PHA window, could change the absolute intensity of the continuum for the MAN curves, so I generally re-measure both the primary standards and the MAN standards for each new run or re-run.  It only takes a few minutes as the primary standards and the MAN standards are often the same standard (though not for the same element!).

5. However, if you are only utilizing MAN standards for major and even minor elements, you can probably skip re-measuring the MAN standards, but as I said above, it won't hurt to re-measure them and it only takes a few minutes for typical run of 5 or 10 elements.

6. Finally, absorption edges in the MAN standards are automatically taken care of by performing an absorption correction on the continuum intensities. This is because each MAN standard absorbs a particular continuum energy depending on the composition of that MAN standard. This was John Armstrong's contrbution to the paper. If you want to see the effect of absorption edges in the MAN curve, just turn off the continuum absorption correction in the Assign MAN Fits dialog.  There are also examples in the above Amer. Min. paper for Na Ka and K Ka with and without the continuum absorption correction.  The absorption correction is generally only noticable at low energies.

john