THE FUTURE OF XRF IN GEOCHEMICAL ANALYSIS LIES IN THE FIELD, NOT THE LABORATORY: THOUGHTS ON THE CAPABILITIES AND LIMITATIONS OF HAND-HELD INSTRUMENTATION.
Philip J. Potts Faculty of Science, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK phil.j.potts@gmail.com
Over the last 50 years, X-ray fluorescence has been refined into a highly precise and accurate technique for the characterisation of geological samples and is now widely used by many laboratories for the routine characterisation of major and trace elements in support of geochemical research. However, the introduction of hand-held XRF instrumentation and its application to measurements in the field places a new perspective on the strengths and limitations of XRF.
Some of the bluestones at Stonehenge comprise a distinctive spotted dolerite that originates from the Preseli Mountains in Wales. In a previous contribution designed to see if it was possible to identify individual outcrops on Preseli from which the bluestones originated, hand-held XRF was applied in an attempt to characterise individual outcrops on the Preseli Mountains, Wales. As essentially a surface characterisation technique, a number of factors must be taken into account when assessing the reliability of these field data obtained by hand-held XRF, especially when compared to a conventional approach in which samples collected from the field would be returned to the laboratory for analysis. The factors affecting hand-held XRF include surface weathering effects, and issues associated with surface irregularities, mineralogical effects and sensitivity. However, hand-held XRF instrumentation does allow multiple measurements to be made over a short period of time across the surface of an outcrop. These data can be used to obtain an assessment of outcrop homogeneity may provide a better overall estimate of the average bulk composition of the outcrop than the conventional approach based on a high precision laboratory XRF analysis of a single sample hammered off the edge of the outcrop.
These issues will be examined in more detail in this presentation with a particular focus on whether the principal vulnerability of conventional laboratory XRF is not the laboratory component of the process, but the interface between the sampler and the sampling target.
XRF FUSION: DEVELOPMENT AND APPLICATION OF INTERNAL STANDARD METHODS FOR HIGH ACCURACY ANALYSIS
Frédéric DAVIDTS, SOCACHIM, Brussels / Belgium
We present new techniques using Internal Standard doped fluxes developed by X-Ray Flux and tested and confirmed by industrial users. This technique has shown excellent results, with precision significantly better than either conventional XRF or other techniques and applicable down to sub % levels. Whilst the analysis is an X-ray technique, it is independent of conventional α-correction X-ray procedures, relying only on the ratio of the peaks and has significant advantages over conventional fused glass disc XRF analysis including insensitivity to problems associated with glass disc curvature and variation in XRF cup quality.
THE USE OF XRF IN THE EARTH SCIENCES: UNDERSTANDING VOLCANIC SUPER-ERUPTIONS.
M.K. Reichow, A.D. Saunders Department of Geology, University of Leicester, Leicester, LE1 7RH, UK
The largest volcanic eruptions, so-called ‘super-eruptions’, are amongst the most catastrophic events that affect the Earth’s surface. They can be explosive, as typified by the Yellowstone system in NW USA, or effusive, like the Siberian Traps in Russia. Both of these events have been linked to major changes in Earth’s climate, with the Siberian Traps possibly causing the end-Permian mass extinction, 251 million years ago. Correlation of the eruptive units (lavas or ashes) is essential for estimating the volume and output rates of individual eruptions and hence quantifying their impact on the surface environment. Whole rock XRF data, determined on rock powder or fused glass disks, allow us to characterise (or fingerprint) individual eruptions and provide insights into the magma evolution over time. XRF also provide key element data (such as Zr and Nb) that can be used to identify the sources from which magmas originate. Other analytical methods often rely on dissolving the rock prior to analysis, and this can lead to problems because of incomplete dissolution of refractory minerals. XRF thus complements techniques such as solution ICP-MS and -OES.
PRACTICAL USE OF NEW VERSION OF ISO 12677:2011 - CHEMICAL ANALYSIS OF REFRACTORY PRODUCTS BY XRF
Dr. Rainer Schramm, FLUXANA GmbH & Co.KG, Borschelstrasse 3, 47551 Bedburg-Hau, Germany
At the end of 2011 a new version of ISO 12677 - Chemical analysis of refractory products by X-ray fluorescence (XRF) - Fused cast-bead method was published.
The method gives a deep description of the analysis of different refractory materials using the fused bead method. In the authors laboratory the new method was performed for two typical refractory materials: high alumina and Magnesia/chromic oxide. The calibrations were built from primary oxides and verified by certified reference materials. The measurement program of a WDXRF instrument was optimized to meet the performance data of the method.
Finally control samples were produced to check the fusion precision and the accuracy.
The presentation gives a summary of all important aspects in the method and their practical implementation in the daily laboratory work.
SO WE’VE GOT SOME NUMBERS FROM THE XRF – WHAT CAN WE DO WITH THEM TO UNDERSTAND ROCKS?
Dr Mike Norry, Department of Geology, University of Leicester, Leicester, LE1 7RH, UK
Or from numbers, via diagrams, to processes.
How to get numbers to ‘speak’ to you!
Only the most ‘number-centric’ person can make very much of a raw table of analyses. You really would have to be is possession of an extraordinary amount of insight to decide what was important and what was not.
The use of diagrams helps portray the behaviour of as many elements as practical, and co-opts the human brain’s undoubted ability for pattern recognition in-order to distil the ‘meaning’ of a data set.
Using chemical data from volcanic rocks, I will show how the diagrammatic approach can lead not just to classification and naming of the various types of lavas but also to unravelling the processes that lead to the formation of magmas via partial melting of the mantle and fractional crystallization.
DEVELOPMENT OF LABORATORY REFERENCE MATERIALS AT THE HEALTH AND SAFETY LABORATORY
Owen Butler, Health and Safety Laboratory, Harpur Hill, Buxton, Derbyshire, United Kingdom SK179JN owen.butler@hsl.gov.uk ©UK Crown Copyright 2012
The health of workers in many industries is at risk through exposure to chemicals, dusts and fibres and occupational hygienists need to determine the effectiveness of measures taken to control such exposure. This is generally achieved by making personal exposure measurements, the accuracy of which relies heavily upon either the use of calibrated real-time instrumentation for in-situ measurements or the use of validated measurement methods when samples are returned to the laboratory for analysis. Hence, in the laboratory, the use of reference materials is required to ensure that such measurements remain within analytical control.
Reference materials for use in this occupational hygiene measurement arena are not always commercially available thus laboratories may need to resort to producing such materials in-house. This presentation will give an overview of three approaches used at HSL namely:
preparation of reference materials using experienced external laboratories via a certification trial in accordance with protocols set out in ISO guide 35
preparation of reference materials using experienced external laboratories via a cross certification trial involving the use of a matrix matched certified reference material
preparation of reference materials using experienced external laboratories via data obtained from a routine laboratory proficiency testing trial.
X-RAY COMPUTER AIDED TOMOGRAPHIC SCANNING – THE NEWEST X-RAY TOY ON THE BLOCK
Dr. Simon Lawes. University of Leicester.
X-ray computed tomography (CT) is a commercially available technique for visualising both external and internal features of an object in a 3 dimensional digital environment. X-ray CT has enormous range of application across the fields of medicine, material science, manufacturing, mineralogy, archaeology and anthropology, along with many more. Computed tomography describes any process by which 2 dimensional or 1 dimensional imaging of an object is reconstructed into a 3D model of that object. Many types of CT system exist, with the most well known being magnetic resonance imaging (MRI) systems and clinical X-ray CT systems, commonly referred to as CAT scanners. The subject of this talk, X-ray micro CT, stands out from these techniques because of its superior resolution and flexibility. This showcase will give some insight into the process by which X-ray micro CT works and the areas of research that it is supporting at the University of Leicester.
VALIDATION OF PORTABLE X-RAY FLUORESCENCE SPECTROMETRY FOR THE QUANTIFICATION OF LEAD DUST ON WORKPLACE SURFACES
Jean-Philippe Gorce1, Martin Roff1 and James Wheeler2
1. Health and Safety Laboratory, Buxton SK17 9JN, UK
2. Health and Safety Executive, Redgrave Court, Bootle L20 7HS UK © UK Crown copyright 2012
The aim was to validate the use of Portable XRF (PXRF) spectrometry for the assessment of surface lead dust contamination in the workplace. A sampling protocol was specifically designed to carry out wipe sampling combined with direct reading by PXRF. Wipe sampling is currently the standard method used by Occupational Hygienist Specialist HSE inspectors for surface contamination investigations.
The degree of correlation between the PXRF and wipe results is high with a correlation coefficient of 0.94. The limit of agreement between the two methods, based on ratios of paired PXRF and wipe results, lies between 0.264 and 3.695.