FlexiSpot: Quantify Non-Homogeneous Samples with Micro-XRF
Elemental Analysis of Non-Homogenous Samples with Micro-XRF
A recent update to the Bruker M4 TORNADO micro-XRF spectrometer now enables more precise quantification of non-homogenous samples, such as powders, soils and granular materials. The new feature is called FlexiSpot, and adds the option of a larger spot size up to 200 µm, in addition to the regular spot size down to 20 μm. This larger spot enables information to be collected from a wider area, for improved quantification of irregular shapes and uneven surfaces.
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More about the M4 TORNADO
Analysing Non-Homogenous Samples
Usually, composition can only be quantified accurately for homogenous samples. This is a problem, because most non-manufactured samples, such as geological specimens, are heterogeneous and elements are not evenly distributed as in manufactured samples such as steel or glass.
With conventional XRF analysis, lengthy sample preparation routines are employed to make the sample more homogenous and achieve accurate results. In contrast, with spatially resolved micro-XRF, very little or even no sample preparation is required.
Quantitative micro-XRF analysis collects data from the whole sample area. However, when performing analysis with spatial resolution at the micrometer scale, it can sometimes be difficult to locate positions where the quantitative results are representative of the whole sample or sample area.
Powders and milled specimens are typical examples that are homogeneous at the millimeter scale, but can show large point-to-point deviations when measured with a resolution of tens of micrometers.
Larger Spot – More Data
The new FlexiSpot feature enables larger areas to be analysed with micrometer resolution. As well as measuring samples with the usual spot size of <20 μm, the M4 TORNADO can now employ an additional spot size of a few 100 μm. This larger spot collects information from a larger area, still at high resolution, for more precise results. This feature was developed specifically for analysing:
- Non-homogeneous samples
- Irregular shaped samples
- Samples with uneven surfaces eg powders
Shorter Measurement Time
When sample measurements with different spot sizes and areas are compared, the relative standard deviations over large areas is significantly improved when using FlexiSpot. Compared to full area maps, the measurement process also takes a significantly shorter time when taking point measurements with spot sizes of 200 μm.
Full details, including the results, are available in a lab report from Bruker.
How it Works
The M4 TORNADO’s polycapillary lens creates a convergent X-ray beam and focuses radiation from the X-ray tube. The plane in which the beam waist lies is called the focal plane. At this point, the beam width is <20 μm for Mo Kα radiation.
The new FlexiSpot feature makes use of the fact that an X-ray beam is wider above and below its focal plane. By moving the sample “out-of-focus”, the irradiated area becomes larger. With the common beam divergence of polycapillary lenses, spot sizes of 100–200 μm can be achieved by moving the sample approximately 2–3 mm out of the focal plane
New XMethod Software
There have also been improvements to Bruker’s micro-XRF analysis software. The new XMethod module makes it easier to manage calibrations and standards. Analytical methods can be developed for complex applications, such as quantitative analysis of the composition and coating thickness of metallic multi-layer stacks.