Introduction
Total reflection X-rays fluorescence (TXRF) is a surface elemental analysis technique often used for the ultra-trace analysis of particles, residues, and impurities on smooth surfaces.
TXRF is essentially an energy dispersive XRF technique arranged in a special geometry. An incident beam impinges upon a polished flat sample carrier at angles below the critical angle of external Total reflection for X-rays, resulting in the reflection of most of the excitation beam photons at this surface. The sample, which is a small residue deposited in the sample carrier, is seen as a very thin sample under a very small angle. Due to this configuration, the measured spectral background in TXRF is less than in conventional XRF. This reduction results in increased signal to noise ratio.
TXRF can be classified according to its application scope:
- Bulk chemical analysis: Samples are subjected to more or less intense processes of chemical treatment for suspension, dissolution, mineralization, pre-concentration and separation.
- Micro analysis: Minute amounts of sample (usually few grains) are analyzed. In this aspect TXRF is a valuable tool in archaeometry and forensics.
- Surface analysis: The chemical quality of flat surfaces is ready analyzed by TXRF.
One of the causes limiting the signal to noise ratio in EDXRF techniques based in the use of direct X-ray tube excitation is the presence of a significant background contribution in the measured spectra. This background is due to the scatter of the x-ray tube Bremstrahlung. Scattered high energy photons not only increase the background in the high energy region of the measured spectra, but also can undertake multiple scatter acts and appear as background in the low energy region.
