Internal standard analysis

The "internal standard" analysis is a quantitative phase analysis method that can be used to determine the amounts of crystalline and amorphous/unidentified compounds in a sample. One of the advantages of this method is that it is not necessary to separate the background from the contribution of the amorphous phases, like e.g. in the degree-of-crystallinity (DOC) analysis.

It requires though that you can add a known amount of a suitable compound ("internal standard") to your sample before recording the diffraction pattern. In the following, this information can be compared to the result of a Rietveld (or RIR) quantitative analysis. The corresponding correction factor (obtained from the relation "known amount of phase A added to sample" / "amount of phase A resulting from RIR- or Rietveld analysis") can then be used to correct the amounts of the remaining phases, rather than normalizing the sum to 100%. As a result, absolute phase quantities are obtained. The difference to 100 weight-% gives the amount of amorphous (and unidentified crystalline) phases in the sample.

A disadvantage of this quantitative analysis method is that only the sum of all amorphous and unidentified phases can be determined.

There are a few conditions that the internal standard compound must fulfill though:

When these requirements are met, a quantitative "internal standard" analysis is performed as follows:

  1. First of all, add a known amount of a suitable "internal standard" compound to your sample and record its powder diffraction pattern. Import the corresponding diffraction pattern into Match! and perform the raw data processing and qualitative analysis as described above.
  2. Afterwards, we recommend performing a "quantitative analysis", by running a Rietveld refinement of the scale factors, unit cell parameters, peak shape parameters and background, in order to get reasonable starting values for the amounts of the crystalline phases. If you cannot run a Rietveld analysis, you can use the results of the semi-quantitative "RIR" analysis that is performed automatically by Match! (see above).
  3. Verify that the amount of the internal standard compound is over-estimated (larger) in the Rietveld (or RIR) analysis compared to the amount added to your original sample. If the latter is larger than the amount resulting from the Rietveld refinement, this would cause the amounts of the remaining phases to be increased in the calculation. As a result, the sum of all phase amounts would be larger than 100%.
  4. Mark the phase you would like to use as internal standard in the match list, then run the command "Internal quant. standard" from the "Quantify" menu (or from the match listís context menu).
  5. In the dialog that opens, please enter the amount (weight %) of the standard phase in the sample, then press "OK".
  6. The result of the "internal standard analysis" will now be displayed both in the match list as well as in the report.
If you would like to return to the "normal" quantitative analysis with the identified crystalline phases adding up to 100%, you can do so by running the menu command "Quantify / Reset internal standard".

The "Internal standard analysis" dialog is operated as follows:

The analysis is run by marking the "internal standard" phase in the match list and then either running the "Quantify/Internal quant. standard" command, or the corresponding command from the context menu of the match list (which can be opened by clicking the right mouse button there).

In the dialog, the phase you have added to your sample (and marked in the match list) is given as "internal standard compound". Please enter the amount (weight %) of this phase as "in the sample".

If you are always using the same amount of internal standard phase, you can mark the checkbox "Don't show this dialog again" at the bottom before pressing "OK". Once you have done so, the "Internal standard" dialog won't be opened again when you run the "Quantify/Internal quant. standard" command again; instead, the "sample amount" value you have entered will be used automatically.

If you would like to re-display the dialog again after having marked "Don't show again", you can do so by running the menu command "Tools/Release 'Don't show again' windows". This will also re-display all other dialogs in which you have previously marked "Don't show again".