TXRF spectrometers

Plankton, periphyton (plants) Ti Mn Fe Ni Cu Zn Se Rb Sr Pb Digest with HNO3/H2O2 in a PEP centrifuge tube with loosely fitted closure [WDC] Measure with TXRF spectrometer [WDC-TXRF] Pettersson and Olsson 1998... 

Fig. 11.10 Typical absolute detection limit values for TXRF spectrometers. The labels a, b and c refer to different instrument settings (adapted from [15]).

In Tab. 11.3, as an example, relative LD values for trace elements obtained by means of WDXRF in different matrices are listed. In Fig. 11.10, a plot of typical absolute LD values for TXRF spectrometers is shown. 

Fig. 11.15 Energy-dispersive XRF spectrum of a multi-element standard, obtained in a TXRF spectrometer.

Figure 8.17 (a) Schematic drawing of a TXRF system. From left to right is the X-ray source, the synthetic multilayer monochromator (Section 8.2.3.2), the thin sample on a support, the silicon drift detector (SDD) above the sample, and finally a beam stop, (b) A commercial TXRF spectrometer, the Bruker S2 PICOFOX with its laptop computer. The displayed spectrum shows the high S/N ratio. ( 2013 Bruker, Inc. www.bruker.com. Used with permission.)... 

Total reflection (or reflectance) XRF (TXRF) is a technique that looks at thin film samples or thin-layer samples with the ability to detect elements from Na to U. A schematic TXRF spectrometer and a commercial system can be seen in Figure 8.17a and b. The Bruker S2 PICOFOX consists of an air-cooled Mo anode metal-ceramic X-ray tube, a multilayer monochromator, and an XFlash SDD and can be equipped with a 25 position autosampler. 

Figure 1.8 Minimum detection limits of TXRF spectrometer (Mo-tube 13 mA/60 kV counting time 1000) Source Phillips Electronic Instruments, Mahwah, NJ, USA)...

TXRF spectrometers equipped with a combination of a Mo-W alloy anode and a double multilayer monochromator to date show the best compromise with respect to detection limits and multielement capability and are state of the art (TXRF 8030 C, Multielement Tracea-nalyzer Atomika Instruments, OberschleiBheim, Germany). 

Relative detection limits are useful figures-of-merit for bulk XRF equipment, where it is usually relevant to know the lowest concentration level at which the spectrometer can be used for qualitative or quantitative determinations. In instalments where very small sample masses are being irradiated (e. g., in the pg range for microscopic XRF (p-XRF) and total-reflection XRF (TXRF)), the absolute detection limit is another useful figure-ofmerit since that provides information on the minimal sample mass than can be analysed in a given set-up. 

Fig. 12-19, Basic design of current TXRF instruments. Besides the total reflection conditions at the sample carrier, as shown in Fig. 12-18, the X-ray optical device in the form of a tunable band pass filter is the most important component of the new spectrometers.

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