June 2012


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JEOL-Focused Probe Users List <[log in to unmask]>
Wed, 20 Jun 2012 16:00:44 -0600
Julien Allaz <[log in to unmask]>
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Julien Allaz <[log in to unmask]>
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Electron Microprobe Lab, University of Minnesota

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Hi Ritchie,

Following the great comment from Gerald & Warren, I would propose to 
insist about minor and trace element analysis, as also peak interference 
correction. WDS analysis can easily (if optimized, and for an 
experienced user) analyze a couple 10th of ppm of some element. I was a 
couple month ago finishing my post-doc and using an SX-100 called 
"Ultrachron" (UMass Amherst, Massachusetts), which is optimized for 
trace element analyses. Our lab was specialized in monazite and xenotime 
U-Th-total Pb dating, although we did also measure Y in garnet, Sr, Ba 
and Ti in glass and feldspar, P in olivine... just to mention a few. We 
are rather proud of our detection limits, which is, believe it or not, 
ca. 30 ppm of Pb (or ca. 10 ppm on an average of 5-6 points), and I was 
even going down to 4-5 ppm of Y in garnet, using four WDS spectrometers! 
Some EMP user would still argue that we may be precise but not accurate, 
but still, it remains valid that the detection limits can be 2 or 3 
orders of magnitude better than EMP. For accuracy, we always check our 
U-Th-Pb dating results using one or more monazite or xenotime of known 
age, and for the other trace element, we checked from time to time with 
NIST glasses doped with some 100th ppm of some element...

WDS can also resolved or, better, avoid peak interferences (peak 
overlap), while EDS suffer seriously of these... And when it comes to 
minor or trace element analyses being affected by a peak interference, 
the correction must be accurately and precisely done; I would never even 
just think about trying such a foolish thing on EDS, unless you don't 
really care about accuracy.

Unfortunately now I have "regressed" and went from a 8-year-old probe to 
a "vintage" 26-year-old probe (JEOL-8600). Still even with such an old 
machine and a not so optimum design for trace element analysis, we can 
easily have a detection limit of 50 to 100 ppm. If you find some people 
interested in trace element analysis, that will help you building your 
case. We are intending to replace our old probe soon, and indeed we are 
making our case using the "trace element" argument (as also the high 
spatial resolution). If you add to this a bright electron source such as 
LaB6 or CeB6, this would even lower the beam size to 0.5 - 0.7 nm and 
increase your spatial resolution. FE on EMP is also an option, but right 
now there are very few lab who successfully performed nice quanti 
analyses, due to the very small interaction volume, and hence the high 
energy per unit of volume (there are huge risk of destroying / melting 
your sample and/or strong diffusion issues).

Regarding non-geological application of EMP, my former supervisor was 
performing analyses for some fibers company (looking at REE), and he 
also had contract for company producing filters (wanted to know about 
impurities catch by these filters if I'm right). The steel industry is 
also a possibility. Right now in my lab, I am doing some N- and 
C-in-steel measurement for another department (physics), and they are 
working together with the industry. My predecessor, now retired, did and 
still does from time to time analyses for the environment industry 
(EPA), for instance looking at some particle in soil, locating where 
some specific element are sitting, especially As and Pb (particle search 
analysis + quantification).

Finally, I would also comment that with the newest software for EMPA, 
you can combine EDS and WDS analyses. This can be a serious advantage if 
you would like a quick analysis, pretty useful in beam sensitive 
material (glass, carbonate, hydrous material...): the major elements are 
analyzed by EDS (WITH a standardization!) and the minor to trace element 
are analyzed by WDS.

Good luck with your application! Send us back some (good) news once you 
get further, especially how it went with the SEMs at the engineering 
dept... It would be better for you to work with them, not against them 
(e.g. proposing them some analysis they cannot perform accurately with 
SEM, convincing them about the usefulness of WDS...)



Dr. Julien Allaz
Research Associate
Electron microprobe manager
University of Colorado Boulder
Geological Sciences
UCB 399
2200 Colorado Ave.
Boulder, CO 80309-0399

Have a look at my Home Page!
=> <=

On 6/20/12 1:06 AM, Gerald Schmidt wrote:
> JEOL Probe Users Listserver
> Moderator: Ellery Frahm, [log in to unmask],
> Electron Microprobe Lab, University of Minnesota
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> On-line help and FAQ:
> *
> Ritchie,
> what an exciting prospect! I hope your case will be successful.
> I work at an institute that's mainly focused on materials research. We
> are using a medium-old SEM (W cathode) and a medium-new EPMA (JXA-8100).
> Our researchers as well as our industrial partners appreciate both
> methods for their respective strengths.
> Would your department cooperate with the the School of Engineering, i.e.
> would your new microprobe be available to them? If so, I think they
> should be quite supportive!
> According to the website of the Research Centre for Surface and
> Materials Science (RCSMS), their SEM equipment is new and provides
> high-performance electron imaging thanks to their Field Emission (FE)
> sources. A microprobe could and should not compete with that. However,
> even high-performance FE SEMs can not provide better spectral EDS
> resolution than the WDS of a microprobe. For example, how do they
> resolve the problem of line overlaps, such as Mo and S?
> Especially in our research field of high temperature materials, we often
> look at alloys containing Mo, and aggressive environments containing S,
> and we want to be able to tell what happens on and below the metal
> surface when those alloys are exposed to high temperatures in aggressive
> environments. You could think of other examples too, and I'm sure the
> RCSMS would love to have a WDS solution at hand!
> Another strength of the EPMA clearly is element mapping. Even the
> coolest FE SEM will produce rather sad looking maps (some examples
> provided on the RCSMS website). I bet if you show a comparison of EDS /
> WDS maps this will convince some people! Especially industrial
> researchers love our colourful WDS maps.
> Finally, when it comes to precise quantification of alloying elements in
> special steels or Nickel-base alloys, we know we cannot rely on EDS.
> Even just the word "standardless" should ring some alarm bells!
> Of course it will be challenging to make this point without sounding too
> critical about the work that's been done at the RCSMS so far ;-)
> Good luck!
> Gerald
> ------------------------
> Dr. Gerald Schmidt
> DECHEMA-Forschungsinstitut
> High Temperature Materials
> Theodor-Heuss-Allee 25
> 60486 Frankfurt am Main
> Germany
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> Fax:    +49-69-7564-388
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> Schrader
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> Steuer-Nr.: 45 255 00182
> -----Ursprüngliche Nachricht-----
> Von: JEOL-Focused Probe Users List [mailto:[log in to unmask]] Im
> Auftrag von Ritchie Sims
> Gesendet: Donnerstag, 14. Juni 2012 09:12
> An: [log in to unmask]
> Betreff: [PROBEUSERS] Case for a new EPMA
> Hi
> For the past ten years we have been using a JXA-840A with EDS for
> quantitative geological
> work, it's been OK, for analytes > about 0.2%, but there is a chance now
> to make a case for
> a brand-new 'proper' EPMA.
> The complication is that we have to find as many potential users, from
> within and without the
> University, to support us.
> In the School of Engineering there are a couple of SemS, with close ties
> to local industry, and
> because their standardless analytical packages give element
> concentrations to two decimal
> places, they and their users accept that their results are quantitative
> (!).
> They are likely to oppose our getting a new EPMA as it would probably
> reduce their revenue
> stream.
> I know virtually nothing of probe applications outside Geology.
> I would really appreciate hearing of EPMA projects and applications in
> non-geological fields
> to help me prepare a case. It would be great to list those for which an
> EPMA beats an SEM
> hands-down.
> cheers
> Ritchie
> --
> Ritchie Sims Ph D				Phone : 64 9 3737599 ext
> 87713
> Microanalyst                 				Fax   : 64 9
> 3737435
> Department of Geology        			email :
> [log in to unmask]
> The University of Auckland
> Private Bag 92019
> Auckland
> New Zealand