Assaying, Microscopy, Mineralogy & XRF/XRD

Assaying, Microscopy, Mineralogy & XRF/XRD 2017-03-23T09:37:54+00:00
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XRF Interelement Interferences and Corrections (2 replies)

Bill Fraser
1 year ago
Bill Fraser 1 year ago

About XRF Interferences: Anyone can give me some tips about interelement corrections in XRF technique? What is the best situation to use fundamental parameters and what is the best one to use alpha corrections? I am currently work with fused beads and pressed powder pellets.

Helena Russell
1 year ago
Helena Russell 1 year ago

Alpha corrections is best if you have calibration standards closely resembling your sample. For fused beads the major elements are quantified as oxides so fundamental parameters should be good enough. For Pressed pellets since minor elements and interelement corrections come into play so alpha corrections would be ideal with enough number of CRMs for calibration.

Victor Bergman
1 year ago
Victor Bergman 1 year ago

Alphas and fundamental parameters work well with fused beads - not so well with pressed pellets - the reason - in fused beads the elements are oxidized, dissolved and distributed evenly in the glass matrix. In a uniform glass the inter-element effects are represented in a statistically predictable manner in proportion to the amount of element present. Also uniform oxidation state can eliminate chemical shift of light element lines due to variable oxidation state. This means that theoretical calculations will be more or less well obeyed.

However in pressed pellets the chemical association of elements in mineral grains or compounds will mean that inter-element effects are affected by the elements that are most closely chemically bound. This departure from the ideal is difficult to quantify without intimate knowledge of the matrix. This and a host of other effects in pressed pellets do not make them so amenable to use with alphas or fundamental parameters as a general analytical solution.

In pressed pellets your calibration material should ideally be matrix matched to the sample being analysed.

In my experience the software in the modern Panalytical or Bruker instruments will give good results for a single wide range major oxide calibration using a 1:10 dilution in borate fusion (I cannot comment for other manufacturers software as with the exception of ARL I have no experience with them).

The best accuracy is obtained using fused beads with fixed alphas restricted to their range of effective linearity followed by variable alphas or fundamental parameters.

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