Spring Meeting Reports - April 2007, Canterbury.

Index of Reports from the sessions.

1. Introduction & Exhibitors Forum.
2. Workshop - XRF: where are we now?.
3. Semi-quantitative.
4. Calibration Samples.
5. Joint session on thin films.
6. XRF Applications - including cultural heritage.
7. Environmental Issues.

The meeting programme is on another page.
View the Meeting abstracts.

Introduction.

The 25th Annual BCA Spring Meeting was held at the University of Kent, Canterbury from the 17th to the 19 April 2007. Delegates were drawn mainly from UK Universities, commercial and industrial institutions. As in previous meetings, the programme was packed with plenary lectures, workshops and themed, parallel, sessions organised by the Industrial Group, Chemical Crystallography Group, Biological Structures Group and the Physical Crystallography Group. For the second time at a BCA spring meeting, sessions were also provided for the XRF community - organised by the Industrial Group. The breadth and depth of the meeting was such that everyone had to be selective in the choice of presentations etc that they attended. Reports on the IG XRD content are reported elsewhere.

The Sessions were officially opened by Dave Taylor prior to the morning workshop.

1. Exhibitors Forum.

All exhibitors at the meeting were given the opportunity to give a 10 minute commercial presentation on their products in this session. Dave Taylor made sure that everyone kept to time. The session was well received and gave delegates an insight into the products available and a chance to get to know the company representatives. It did make prioritising time spent that evening touring the exhibition much easier and exhibitors were pleased with the opportunity given to interface directly with delegates.

2. Workshop - XRF: where are we now?.

Speakers - Left to Right: Bruno Vrebos, Margaret West, Mark Ingham(Chair), Mike Dobby.

Bruno Vrebos from PANalytical began with XRF: what instruments have we got or are likely to get soon? An organogram of X-ray fluorescence showed the multitude of techniques available within this area of analysis. The two main stems of this were wavelength dispersive (WDS) and energy dispersive (EDS). Bruno highlighted the main differences between the two methodologies these being principles of operation, photon efficiency and resolution. He then focused down in more detail on those that would have the greatest impact on a measurement. For WDS the resolution is primarily determined by a combination of the crystal and collimator chosen whilst the detector itself will have little impact. The dispersion is inversely proportional to the d-spacing of the crystal chosen. This was illustrated by the Cu Kβ peak appearing on the shoulder of the Zn Kα peak with a PET crystal whilst clearly separated when a LIF220 crystal is used. With EDS there are no analysing crystals or collimators. Conversely, with EDS the detector makes a major contribution. With EDS the photon efficiency is far superior to WDS. A lot of effort is put in to getting photons at the detector in WDS systems. This is then mitigated by such factors as photo-electric absorption, fluorescent yield, collimator losses, reflectivity, window losses to name but a few. For light elements one of the biggest problems is absorption of their energy specific X-rays by the sample matrix itself.

Bruno then moved on to consider the use of XRF analysis for trace elements. Geological samples, one of the areas this technique can greatly help, have a complex matrix with many analytes at low concentrations further complicated by often sloping backgrounds and multiple line overlaps. The focus of this section of the presentation was the lower limit of detection (LLD) and how this has and possibly can in the future be reduced. Tricks of the trade to be considered are reducing the background by optimising tube voltage and current along with appropriate use of beam filters. The use of an Al 0.75mm beam filter has the potential to reduce the counting time from 195 seconds down to 132 seconds to achieve a LLD of 1ppm for As Kß. Alternatively, the LLD is reduced from 1.4ppm down to 1.1ppm with a 100 second fixed counting time. The main principles to improving the LLD are to reduce the background, enhance the sensitivity and to increase the counting time. I had my first lesson in 3D optics and what a powerful technique it appears to be. There is a dramatic reduction in the background as the 3D optics are set up in such a way that the background is “polarized” out.

Unfortunately time beat Bruno and it was easy to understand why that had happened. Bruno has a relaxed style of presentation which enabled those of us who are less knowledgeable in the field, myself included, to easily follow and digest the information that was being shared with us.

Next we were in the capable hands of Margaret West who presented XRF: what can we do with them? Margaret lead a workshop style talk on what can XRF do these days? So how do you find out what can be done with XRF? Apart from conferences, such as the one we were all attending, with plenty of experts with knowledge to be shared there are also user groups in this category. There is also a plethora of literature in the form of journals, standards, books and reference materials. In particular the literature based resources Margaret pointed us to were:

• IngentaConnect which is an internet search engine with more then 21 million article, chapters and reports!
• X-ray spectrometry Journal. Margaret suggested subscribing to this at a personal rate of £80 per year c.f. £1000 as a company subscription.
• JAAS (Journal of Analytical Spectroscopy) www.rsc.org/jaas.
• Atomic spectroscopy updates www.asureviews.org. This is written by a community of established workers in their field. Topics includes environmental analysis (all techniques), atomic emission and annually in October XRF special focus. This reviews developments in XRF from published work. Recently there has seen an increase in publications around archaeological science and cultural heritage. There is a new UKAS scheme for the accreditation for the preparation of certified reference materials. Other areas these relevant publications cover include instrumentation, portable systems, spectrum analysis, X-ray optics, synchrotron radiation, geological and industrial applications. The total list is exhaustive. The timetable for the review is a cut-off in mid-April. Abstracts are then downloaded and circulated to the writing team. The current members are Andy Ellis, Peter Kregsamer, Phil Potts, Christina Streli, Christine Vanhoof, Margaret West and Peter Wobrauschek. There is then a group meeting in June and a referee meeting in July all to coincide with the October review.

As a non-academic XRF user it can sometimes be difficult to know where to turn to get help in the literature. Following this workshop I will not have such a problem in the future. It has provided me with a wealth of reference information that I’m sure I will be referring to over the coming years.

The final presentation of the morning session was delivered by Mike Dobby from Bruker AXS on XRF outside of the box. Mike firstly considered laboratory based XRF instrumentation that are great if the samples are of the right size, will not “harm” the XRF and the desired level of detection can be achieved. So when the above isn‘t possible how do you take the XRF to the sample? There were three approaches that Mike outlined and gave examples for – online XRF, Total Reflection XRF (TXRF) and hand-held XRF.

I‘d not heard of TXRF before. Apparently it is a form of EDXRF method with geometric conditions for both the excitation of the sample and the detection of the fluorescence radiation that minimize scatter effects. Mike discussed the use of the portable bench-top S2 Picofox in the analysis of wine. K, Ca, Fe and Cu for quality control purposes along with multi element analysis for origin control. On two wine CRMs purchased from the Centre Oenologique de Bourgogne good agreement with the certified values was achieved using the TXRF. As Mike pointed out the remainder of the CRM could then be sampled by the analyst – I‘ll volunteer!

The final part of the presentation was on the Star Trek-esque hand-held Tracer III-V XRF. Mike covered a range of unusual samples that this XRF had been used to analyse. These included several swords, a Wootz ingot, pistol, bronze canon and Zn plated armour from India purported to be the oldest in the world. The spectrum obtained by the hand-held XRF clearly showed the presence of Zn as well as Cu and As. This was overlaid against a spectrum from a modern Fe based standard which highlighted the differences in elements detected. I was starting to get concerned about the “arms” theme but Mike covered elemental analysis of other samples ranging from the handle of a mirror, a wooden block, Victorian Fox fur, alleged gold leave on a book, finishing with a picture in a museum.

Next time I‘m given an unusual shaped object to analyse my first thought may no longer be how can I chop it up to get it in to my lab based XRF but what portable instrumentation is there out there that may better suit my needs.

Thanks are due to both Bruno, Margaret and Mike for a thoroughly enjoyable and informative session presented by both speakers.

Alison Burke
Huntsman Pigments

3. Semi-quantitative.

Speakers - Left to Right: Ros Schwarz(chair) Heather Harrison, Belen Morales (absent).

What on Earth is this? Semi-quantitative ED-XRF
Heather Harrison, British Geological Survey

This talk considered why you would use semi-quantitative analysis, what you may be looking for from the application and what sorts of results are obtained.

The system used was a PANalytical Epsilon 5 system which consisted of two polarised ED-XRFs with 3-D Cartesian optics. Semi-quantitative analysis has advantages for a wide range of sample types. These include pressed powder pellets and loose powders the use of which reduces the time required for sample preparation.

Examples of analysis were then provided from a wide range of substrates comparing analysed value to certified value. For both major and minor component analysis this approach proved to be only partially successful with some elements being over or underrepresented depending on the sample matrix. Comparison was also drawn between loose powder and pressed pellet. The results proved to be comparable.

When to Use XRF Semi-Quantitative Analysis
Belen Morales, London & Scandinavian Metallurgical Ltd.

Belen reported on the problem on the problem of carrying out analysis on materials when no suitable standards are available. In order to carry out determinations of composition of these samples she proposed the use of semi-quantitative analysis protocols in this case Uniquant 4.

This approach has a number of advantages, which include minimum sample preparation, low detection limits and wide elemental range. The major features of Uniquant 4 were explained, namely model based determinations of instrument sensitivities based on a single sample calibration, extension of fundamental parameters to solve spectral line overlaps and graphical support for intensities and calculated backgrounds.

Four case studies were then presented one comparing sample preparation methods, one looking at different matrixes, a further study into the analysis of odd samples and finally refining semi-quantitative analysis. Results proved both consistent and for the large part accurate.

John Woods
Scientifics

4. Calibration Samples.

Speakers - Left to Right: Phil Russell(inset), Ros Schwarz(chair), David Beveridge, Neil Eatherington.

Wide Range Oxide Fused Bead Standards
Neil Eatherington, British Geological Survey

This talk discussed methods of calibration using single and multielement standards prepared as fused beads.

Standards were conditioned at temperatures ranging from 220°C - 1200°C depending on the nature of the material and then prepared as fused beads by fusing 0.9g of standard with 9g flux at 1200°C for 12 mins. The standards were fused in duplicate and a blank flux was also prepared. The standards were then analysed on a PANalytical Axios Advanced using SuperQ software and FP used as the matrix correction model. The total measuring time was 9 minutes at 2.4kW. Standards consisted of 20 synthetic materials and 21 oxides.

From the results it would appear that this approach offers relatively simple preparation, simple calibration and reliable batch to batch analysis giving accurate results.

No standards? No blank? No standardless analysis software? No problem!
David Beveridge, Harman technology Ltd - ILFORD Photo

This talk discussed the determination of iron and arsenic contents in the fluorinated surfactant Lodyne S103A. Suitable lines were selected and the mass absorption coefficients were determined. Attempts were then made to match the mass coefficient values in a number of different matrixes. A number of different organic and mixed organic inorganic solvent systems were selected. However after issues over solubility and matrix effects were ascertained from the predicted response it was determined that a dilute sulphuric acid solvent system gave the most acceptable results for this compound.

Normative Committees.
Phil Russell, PANalytical

This talk discussed what normative committees are, there relationship to XRF analysis and the importance of involvement.

These committees are groups that are either trade or regulatory body related. Tasks of the committee are to promote standardised methods and/or provide a measurement strategy for quality or regulatory control. There are a range of norms that can be developed which include standards that measure a parameter using a specific technique, guides that provide information about using a technique or process and protocols for a procedure.

There are ranges of normative committees some of, which are government lead, some of which are industry lead. They hold regular meetings about common requirements including specific industrial processes, health and environment and quality systems. XRF analysis is a rapidly developing field of analysis and it is very important that all members of the XRF community play an active role in these committees to develop XRF analysis as the procedure of choice.

John Woods
Scientifics.

5. Joint session on thin films.

This report is stored elsewhere >>> link to report.

6. XRF Applications - including cultural heritage.

Speakers - Left to Right: Jean-Philippe Gagnon (inset), Margaret West, David Beveridge(chair), Luisa Carvalho,Rene Van Grieken. Claire Collins, Charles Gowing. Malcolm Haigh (inset).

As might be expected from its content, this session produced lots of nice pictures of fine buildings and other works of art. We got off to a good start, with Luisa Carvalho from Lisbon, who spoke on the use of XRF for characterising documents. XRF permits the characterisation of different papers and, by use of cluster analysis, the grouping of different samples into their types. This work is also of use in detecting forgeries. She was followed by Clair Collins (Oxford Instruments), who described the use of a hand-held XRF analyser for examining a range of objects which may broadly be grouped as "cultural heritage". Hand-held XRF analysers are becoming popular, with several different types on the market, and the sort of things they can do are impressive.

Malcolm Haigh (Spectro) moved over to more general applications in his talk, which centred on the use of a polarised-beam EDXRF unit. This has sundry advantages over the more traditional types, in giving more intensity and lower backgrounds. This was applied to geological samples. Charles Gowing (British Geological Survey) continued the geological theme, with his talk on a compact benchtop EDXRF which can be taken on site in the BGS Mobile Environmental Laboratory. They hope to accredit the method under UKAS and for soils under the MCERTS scheme. Many geological samples are analysed as fused beads, and Jean-Philippe Gagnon (Claisse) showed in his talk how to get fast analytical results by fusion without knowing the Loss On Ignition. In fact, by using net intensities, it is now possible to calculate the concentration of the volatile compounds lost during the fusion.

The last two talks contained most of the pretty pictures. Margaret West (West X-Ray Solutions) described some work that had been done for English Heritage. Conservation and restoration can be controversial, and much modern conservation work involves putting right the mistakes of the past. To take one example, the C11th carving at Kilpeck church, in Herefordshire - among the best of its era in England - is being attacked by sulphate-rich encrustation. Understanding what is happening requires XRF and XRD. In the final talk, René van Grieken (Antwerp) followed on with the theme from Kilpeck - damage to buildings caused by atmospheric aerosols. Examples came from all over Europe (not to mention New York) and showed what can happen, not just to stonework, but also to stained glass and paintings within a building. A range of techniques, not just XRF, were used to analyse the pollutants and their reaction products.

David Beveridge
Harman Technology.

7. Environmental Issues.

Speakers - Left to Right: Margaret West(chair), Stan Piorek, Ros Schwarz, Nick Marsh, Chris Vanhoof, Rene Van Grieken.

Climate records - lurking in the small print? What's at the bottom of your lake?
Nick Marsh, University of Leicester, Geology

Nick started the lecture with a reminder that it was much warmer during the Jurassic, a time when there was no ice and not much land and many animals, such as plankton lived fast and died young thereby preserving the oxygen isotope signature of the atmosphere at that time. Much research into oxygen isotopes has benefited from the easy release of oxygen from carbonate phases by dilute mineral acids followed by analysis by ICP-MS. However, conditions in naturally acidic lakes do not allow for the preservation of carbonate fossil remains and processes such as dolomitisation can change the delta-oxygen ratios.

Fortunately several planktonic and other aquatic creatures utilise silica to produce their skeletal matter. A series of fascinating SEM pictures showed the array of skeletal remains that have been collected from lake sediments as well as some contaminant materials that can be found in the samples. It is difficult to remove completely silica contaminants from samples so XRFS was identified as a reliable technique capable of determining a wide range of chemical data to enable mass balance calculations on the various contaminants in the sample. A fused bead method using very small < 0.1 g sample sizes with 3 g of high purity flux had been developed for this purpose. An inverse correlation was observed between δ¹⁸O and Al₂O₃ due to the presence of silt in the samples.

Development and validation results of a new European Standard prEN 15309 for the determination of the elemental composition of waste and soil by XRF.
Chris Vanhoof, VITO, Belgium.

The growing interest of government and industry to implement XRFS as an analytical tool for the characterisation of waste and soil has led to the development and validation of a new European Standard. This method was working to EU and landfill directives; the EU directive had previously been based upon aqua regia or HF digestion methods. Work instructions were developed in 2000-2001 and the Standard went through a series of improvements between 2003 and 2006 and was approved in 2007. This was achieved against the background of a wide range of matrix compositions and lack of suitable reference materials for inhomogeneous materials like waste.

Chris explained that on-site verification of the method would follow the basic characterisation and control analysis. A range of methods were considered comparing qualitative or quantitative, field- or lab-based etc. The Standard incorporates two procedures, a screening / qualitative phase followed by energy or wavelength XRF in the laboratory. The method validation was based upon two soils, one fly ash and ink and an electronic sludge sample. The characterisation was carried out by an interlaboratory exercise, participated in by labs from seven countries. The relative reproducibility of the soils and fly ash materials was 10-20 % (pellet analysis) or 2-10% (fused bead analysis) with trace elements < 20 ppm being 8-15% and < 20 ppm 25-30%. The waste material data had a relative reproducibility up to 50% and the ink sample data had high standard deviation and a large loss on ignition. All that now just remains is for the on-site verification to be carried out.

Screening of electronic products with a "small-spot" hand-held XRF analyser for compliance with RoHS Directive.
Stan Piorek, Niton

Industry now has to fully comply with EU RoHS, WEEE and ELV directives. Complying with these directives for testing all components and raw materials could prove very costly, e.g. €1300 per sample for a simple component such as a printer cable. Manufacturers have responded by producing compact pectrometers with robust calibrations that can perform non-destructive analysis in a shop floor situation. This spectrometer utilises a collimated beam to reduce the beam size to 1 mm2 spot size that can be targeted using an integrated CCD camera. A number of images illustrated that analysis of individual solder points is possible and its use for screening for the presence of brominated flame retardants was also described. Stan concluded his presentation by coining a new term, HH-XRF, hand held XRF as distinct from field portable XRF.

Micro-spot XRF in RoHS compliance testing : performance and pitfalls.
Ros Schwarz, Oxford Instruments.

This presentation also covered the analysis of electrical components to meet EU RoHS directives. Ros described a micro-spot XRF that could use a video camera to target analysis with spot sizes of 0.15, 0.3 or 1 mm2 for screening analysis. Difficulties encountered with analysis of materials such as Sn63Pb37 solder were discussed and illustrated, particularly spectral line overlap caused by elements in the matrix substrate. Another persistent difficulty is the scarcity of Reference Materials (RMs) and Ros urged caution against using inappropriate RMs if no suitable ones were available.

Charles Gowing
British Geological Survey.