Use Blank Calibration Sample Trace Element Accuracy Corrections

EPMA Probe

Use Blank Calibration Sample Trace Element Accuracy Corrections

This option will globally turn on or off the assigned blank correction parameters (see Standard Assignments dialog under the Analyze! window) to quickly evaluate the effect of the quantitative iterated blank correction.

 

The blank correction is a powerful method to improve the accuracy of trace elements (and because it is fully matrix corrected can even be applied in the case of oxygen analyses for water by excess oxygen). The following example demonstrates the application of the blank correction to a Ti in quartz analysis.

 

 

For example, spectrometer analyzing crystals have secondary lattice reflection planes which will produce small artifacts (“holes”) in the spectrum, some directly underneath the analytical peak (depending on the mounting orientation). This produces a systematic accuracy error in trace element analyses that can easily exceed the precision of the measurement even with moderate beam current and count times.

 

ELEM:       Ti      Ti      Ti      Ti      Ti      Si       O   SUM 

XRAY:     (ka)    (ka)    (ka)    (ka)    (ka)      ()      ()

   428 -.00023  .00029  .00005  .00076 -.00061 46.7430 53.2572 100.000

   429 -.00023 -.00003 -.00001 -.00009  .00022 46.7430 53.2569 99.9998

   430 -.00010  .00002 -.00011 -.00003  .00045 46.7430 53.2572 100.000

   431  .00016 -.00007 -.00009 -.00035  .00037 46.7430 53.2570 100.000

   432  .00019 -.00029  .00002 -.00016 -.00037 46.7430 53.2566 99.9990

 

AVER:  -.00004 -.00002 -.00003  .00003  .00001 46.7430 53.2570 99.9999

SDEV:   .00020  .00021  .00007  .00043  .00047  .00000  .00024

UNCT:      -.1      .0     -.1      .0      .0      .0      .0

KRAW:   .00000  .00000  .00000  .00000  .00000  .00000  .00000

PKBG:   .99857  .99949  .99907 1.00219 1.00050  .00000  .00000

BLNKL: .000000 .000000 .000000 .000000 .000000    ----    ----

BLNKV: -.00043 -.00009 -.00053 .000039 .000704    ----    ----

 

By measuring the systematic offset (blank value line “BLNKV”) on a “blank” standard which contains a zero, or known non-zero level (“BLNKL”) for the element of interest in a similar matrix one can subtract the corresponding intensity from the sample during the matrix iteration for a rigorous treatment of all data including the k-ratio and P/B calculations.