Detection Limits from Bruker EDS spectra

[AndrewLocock]

Hello,
It would be useful if the Probe for EPMA software could calculate detection limits for elements measured using the Bruker EDS.
At present, the software does not report detection limits for such elements.
Instead, I use our measured standards, and taking the relationship between net cps/nA and tabulated concentration, estimate a functional detection limit.

However, it would be preferable to have Probe for EPMA provide a calculated limit of detection as it does for elements measured by WDS.
Thanks!
Andrew

[John Donovan]

It would be useful if the Probe for EPMA software could calculate detection limits for elements measured using the Bruker EDS.
At present, the software does not report detection limits for such elements.
Instead, I use our measured standards, and taking the relationship between net cps/nA and tabulated concentration, estimate a functional detection limit.

However, it would be preferable to have Probe for EPMA provide a calculated limit of detection as it does for elements measured by WDS.

Hi Andrew,
I agree 100%.

I have previously asked both Thermo and Bruker to also return the background intensities just as they already return the net intensities (for quantification).  I never heard back from Bruker on this request, but I did talk to Greg Fritz at Thermo about this and he said the problem is that the peak deconvolution method that the EDS vendors use, does not produce background intensities.

I suggested that maybe they could simply take the net intensities and subtract them from the raw spectrum using same ROIs.  He said that was an interesting idea but they haven't done anything yet on this that I know of.

But I agree it's important that they do this.  I will ping both vendors about this again and let's see what happens.
john

[John Donovan]

Hi Andrew,
I heard back from Bruker and there is apparently a way to obtain the background intensities for the elements quantified by EDS, but I haven't received any details as yet.  Will keep you posted.
john

[John Donovan]

It would be useful if the Probe for EPMA software could calculate detection limits for elements measured using the Bruker EDS.
At present, the software does not report detection limits for such elements.
Instead, I use our measured standards, and taking the relationship between net cps/nA and tabulated concentration, estimate a functional detection limit.

However, it would be preferable to have Probe for EPMA provide a calculated limit of detection as it does for elements measured by WDS.

Hi Andrew,
I was able to figure out how to obtain the EDS background intensities, in addition to the net intensities, through the Bruker API with a little help from Uwe Rossek at Bruker. This should allow all the statistical calculations to occur for EDS elements that already occur for WDS elements.

Here are some results for their "demo" spectrum:

Code: [Select]

St   31 Set   1 Bruker demo composition, Results in Elemental Weight Percents
 
ELEM:       Si      Fe      Mg      Al      Na      Ca      Ti       O
TYPE:     ANAL    ANAL    SPEC    SPEC    SPEC    SPEC    SPEC    SPEC
BGDS:      EDS     EDS
TIME:    19.55   19.55     ---     ---     ---     ---     ---     ---
BEAM:    30.01   30.01     ---     ---     ---     ---     ---     ---

ELEM:       Si      Fe      Mg      Al      Na      Ca      Ti       O   SUM 
    12  18.880  16.138  10.200   7.800   2.400    .950    .800  42.500  99.668
    13  18.843  16.334  10.200   7.800   2.400    .950    .800  42.500  99.826
    14  18.980  16.428  10.200   7.800   2.400    .950    .800  42.500 100.058

AVER:   18.901  16.300  10.200   7.800   2.400    .950    .800  42.500  99.851
SDEV:     .071    .148    .000    .000    .000    .000    .000    .000    .196
SERR:     .041    .086    .000    .000    .000    .000    .000    .000
%RSD:      .37     .91     .00     .00     .00     .00     .00     .00

PUBL:   18.900  16.300  10.200   7.800   2.400    .950    .800  42.500  99.850
%VAR:    (.00)   (.00)     .00     .00     .00     .00     .00     .00
DIFF:    (.00)   (.00)    .000    .000    .000    .000    .000    .000
STDS:       31      31     ---     ---     ---     ---     ---     ---

STKF:    .1390   .1398     ---     ---     ---     ---     ---     ---
STCT:  2606.95  435.57     ---     ---     ---     ---     ---     ---

UNKF:    .1390   .1398     ---     ---     ---     ---     ---     ---
UNCT:  2606.95  435.57     ---     ---     ---     ---     ---     ---
UNBG:   571.37  117.47     ---     ---     ---     ---     ---     ---

ZCOR:   1.3594  1.1662     ---     ---     ---     ---     ---     ---
KRAW:   1.0000  1.0000     ---     ---     ---     ---     ---     ---
PKBG:     5.56    4.71     ---     ---     ---     ---     ---     ---

Detection limit at 99 % Confidence in Elemental Weight Percent (Single Line):

ELEM:       Si      Fe
    12    .021    .050
    13    .021    .050
    14    .022    .050

AVER:     .021    .050
SDEV:     .000    .000
SERR:     .000    .000

Percent Analytical Relative Error (One Sigma, Single Line):

ELEM:       Si      Fe
    12      .1      .2
    13      .1      .2
    14      .1      .2

AVER:       .1      .2
SDEV:       .0      .0
SERR:       .0      .0

Detection Limit (t-test) in Elemental Weight Percent (Average of Sample):

ELEM:       Si      Fe
  60ci     ---     ---
  80ci     ---     ---
  90ci     ---     ---
  95ci     ---     ---
  99ci     ---     ---

Analytical Sensitivity (t-test) in Elemental Weight Percent (Average of Sample):

ELEM:       Si      Fe
  60ci    .093    .109
  80ci    .165    .195
  90ci    .255    .301
  95ci    .375    .444
  99ci    .866   1.024

So, please go ahead and update PFE using the Help menu and give it a whirl and let us know what you think!
john