Comparison of elemental analysis techniques - advantages of XRF in comparison with ICP and AAS

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For quality and process control many elemental analysis techniques are available. ICP, AAS, ICP-MS, ICP-OES and X-ray fluorescence spectroscopy (XRF) are traditional techniques used in many industries. Each of these techniques has a number of advantages and disadvantages giving the analyst the flexibility to choose which technology suits best. When the required limits of quantifications are above 1 ppm (µg/g), or when non-destructive analysis is required, XRF is a very attractive technique that should be considered, especially when analyzing solids, powders, slurries, filters and oils.

Opposed to ICP and AAS, XRF spectroscopy does not require sample dissolution or digestion, therefore allowing for essentially non-destructive analysis. By avoiding the potential for inaccuracies caused by incomplete dissolution and large dilutions, the complete analysis by XRF helps to ensure the accuracy and reliability of results.

Five of the many advantages of XRF are discussed:
1. Simple, fast and safe sample preparation without chemical waste
2. Non-destructive analytical technique
3. Low cost of ownership
4. Analysis at the production site (at-line)
5. No need for daily re-calibration

1. Simple, fast and safe sample preparation

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Measurements by XRF are carried out directly on the solid material (or liquid) with little to no sample preparation. XRF analyzers can work with any type of sample without the need for dilution or digestion and therefore no disposal of chemical waste is necessary. Transferring liquids in wet-chemical methods from one vessel to another can introduce contamination and/or loss of material.
Measuring relatively large sample volumes (100 mg up to 10 grams) results in a more representative characterization of the sample. Also, errors due to sample inhomogeneity are easily minimized by using larger sample volumes. XRF can measure gram quantities without any risk of cross contamination and therefore the error in an XRF result is much smaller.

2. Non-destructive technique

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In benchtop XRF spectrometers the sample is excited using an X-ray tube and the characteristic X-rays from the sample are detected and automatically processed by the software. These low-power X-ray tubes don’t produce an extensive amount of X-ray photons or heat and therefore don’t damage the sample or alter its crystal structure.Irregularly shaped samples that fit into the spectrometer can be analyzed without the need of destructive sample preparation, like crushing and grinding.
The same sample that was analyzed by XRF can later be analyzed using other techniques for further investigation, if necessary.

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