EDXRF-Microscope

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EDXRF microscope scanning method

based on the physical interaction of primary x-rays with atoms in the sample and acquisition of secondary fluorescent x-rays by an energy dispersive detector.

Instrumentation

• long fine focus Philips XRD Mo tube Type PW 2275/2, 3 kW, 60kV
• HV-Generator (R. Seifert & Co. ISO-DEBEYEFLEX 3003
• glass mono-capillary of 100 µm Ø
• energy dispersive liquid N2-cooled RÖNTEC XFlash Si(Li) detector of 139 eV resolution at Mn (Ka) mounted at 45°.
• evacuated nozzle mounted between detector and sample
• optical camera for image acquisition
• xyz-stage with sample holder
• computer control

Advantages

• in-situ method for chemical analyses of liquid, powder, solid or biogenic matter
• minimum sample preparation
• fast non-destructive data acquisition from points and 1D-profiles (full spectrum evaluation) and as 2D-maps (selected element channels)
• high spatial resolution; focus <100 µm Ø
• variable step size and acquisition time
• all elements from Mg to U can be analyzed
• detection limits range from 0.x to 0.000x %

Disadvantages

• light elements cannot be detected
• absorption by air of light elements (Na, Mg, Al, Si)
• no matrix correction due to changing matrix
• for maps no background correction
• inhomogeneities and geometry of the sample
• quantification is not yet possible
• crystallographic interference

Standard measurement conditions

• 45 kV, 30 mA, 100µm step size, 0.5 sec

Data evaluation

Data are stored as full spectra for point and profile analyses.

The full spectra can be corrected by fundamental parameters, quantified and compared with standards, stored in spreadsheets and plotted as element distribution profiles.

2D element distribution maps can be plotted individually at full scale or with selected thresh holds. Three selected elements can be combined to RGB plots.

Application

Ore deposits, climate, environment, cultural heritage, microtectonics, metasomatism, petrology, sedimentology

For details see poster (PDF files):

• Stratigraphic control in salt successions due to EDXRF-scanning techniques (PDF, 290 KB)
• Application of a new XRF-scanning techniques to monitor column experiments (PDF, 347 KB)
• The ITRAX EDXRF-Microscope (PDF, 447 KB)