UPSC Combined Geo-Scientist, Mains · 2020 · Mains Paper III
Q1(e). Matrix effects in XRF
Question
What are matrix effects in X-ray fluorescence analysis?
Answer in brief
Other constituents alter excitation, absorption and measured fluorescence intensity.
Key points
- Primary absorption: the matrix absorbs incident X-rays before they excite the analyte.
- Secondary absorption: the matrix absorbs the characteristic analyte radiation on its way to the detector.
- Enhancement: characteristic radiation from another element can further excite the analyte, increasing its signal.
- Spectral overlaps and physical effects such as particle size, mineralogy and surface roughness can add bias.
The full model answer
As written for the answer booklet: the diagram carries the working, the lines stay short. Read here only; it is not offered as a download.
CoversMatrix effects in XRFX-ray fluorescence
All parts of Question 1
- 1(a) Significant figures5 marks
- 1(b) Particle diameter in chromatography5 marks
- 1(c) NDIR determination of carbon monoxide5 marks
- 1(d) Thermobalance5 marks
- 1(e) Matrix effects in XRF5 marks
- 1(f) Sample introduction into ICP5 marks
- 1(g) Formation of excited calcium atoms5 marks
- 1(h) Spectrophotometric chromium in a mineral5 marks