April 2011

Spring Meeting Reports - April 2011, Keele.

The meeting programme is on another page.

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Introduction.

The 29th Annual BCA Spring Meeting was held at the University of Keele from the 12th to the 14 April 2011. 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 forth 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 XRF Sessions were officially opened by the XRF programme coordinator - Dave Taylor.

Sample Preparation Workshop.

Laboratory session.

Frederic Davidts weighs a sample for fusion.

The workshop started in a laboratory a short walk from the main meeting venue and allowed live demonstrations of various sample preparation techniques. These started with the preparation of fused beads by Frederic Davidts and this theme was continued by Rainer Schramm. Both demonstrators were able to answer lots of delegate questions as they gave their live demonstrations. Rainer then moved on to a demonstration of the preparation of pressed pellets. All in all this was a very useful session with lots of delegate interaction.

Laboratory Session.

Rainer Schramm describes fusion of samples.

Workshop Delegates.

Speakers - Left to Right on front row: Ros Schwarz and Margaret West.

Fortified by lunch, the afternoon session continued the sample preparation theme as Margaret West considered the expanding range of techniques for the preparation of samples in the laboratory and in the field. Requirements for solids, powders, liquids & gels and environmental samples were discussed. Information on possible contamination from grinding media was presented as well as the consequences of particle size effects, surface finish of solids and liquid volume on the critical depth of analyte lines. Practical hints and tips were offered on the care of platinum ware and selection of sample support films. Delegates not wishing to discuss commercially sensitive information during the workshop found ample time for discussion during the evening exhibition buffet and breaks between sessions during the rest of the conference.

After tea break, Ros Schwarz discussed some of the practicalities of setting up an XRF calibration. The features found in typical XRF spectra were outlined, for both WD - and ED – instruments, including tube lines and contaminants; and for ED-XRF sum and escape peaks. Line selection was linked to a consideration of excitation conditions and the instrumental parameters that are under the analyst’s control, such as tube settings and beam filters; and for WD-XRF crystals and collimators. Line overlaps were illustrated and some of the ways to minimise the effects mentioned briefly. Some of the issues associated with WD-XRF, particularly second order diffraction from crystals and the role of pulse height discrimination in ameliorating the difficulties, were pointed out.

As Mark Ingham was unfortunately unable to join the session, Ros also presented “Fun with background correction in WD-XRF”. Several different strategies for background correction were introduced, using one or two background positions. A discussion of the determination of trace molybdenum at the single figure ppm level in a range of matrices showed that the Willis method of calculating a curved background from two positions gave the best results.

A delegate comment “A long day, but full of practical ideas to take back to the lab"

New Developments.

Speakers - Left to Right: Ros Schwarz (chair) Stefan Kneip and David Lane.

Using low cost CMOS sensors for X-ray imaging and spectroscopy.

David Lane, Cranfield University.

David began by saying commercially available X-ray sensors are available for scientific and medical applications. Whilst these can be large, sensitive and can provide energy dispersive information, they can also be expensive. Thus, the motivation for this study was to provide a low cost sensor with a USB interface for forensic applications in teaching, for scene of crime work and to screen suspect materials. The study examined the use of low cost CMOS sensors for X-ray imaging and spectroscopy.

Examples of imaging using modified webcams were presented as well as those for a simple energy dispersive X-ray detector based on an Omnivision OV7221 sensor, a device used in cellular telephones, PC multimedia and children's toys. X-ray sensitivity is enabled by replacing its front glass window with a 5 µm thick aluminium foil. X-rays are then detected as an increase in a pixel's dark current due to the generation of additional electron-hole pairs within its active region. Images of several minutes were achieved by recording the image as an AVI file, in which the energy information is retained through the brightness of each pixel in each individual frame. Frame stacking using image-processing software was used to simulate long exposure times. Black and white imaging was found to be the best so as to avoid the use of Bayer filters which are required for colour imaging.

Bright spatially coherent synchrotron X-rays from a table-top source.

Stefan Kneip, Imperial College London.

Stefan said that despite the demand, only a few dedicated synchrotron facilities exist worldwide, in part because of the size and cost of conventional (accelerator) technology. He described the use of a new generation of laser-driven plasma accelerators, which accelerate high charge electron beams to high energy in short distances to produce directional, spatially coherent, intrinsically ultrafast beams of hard X-rays. A focused high power laser beam is pulsed (30fs pulse width) into a plume of gas which becomes completely ionised. The source size is 1 to 2 µm. Hundreds of MeV electrons are generated which then produce tens of KeV X-rays with a spot size of 1 to 5 µm.

The size of the synchrotron source reduces from tens of metres to centimetres, simultaneously accelerating and wiggling the electron beam. Stefan said that the resulting X-ray source is 1,000 times brighter than previously reported plasma wigglers and thus has the potential to facilitate a myriad of uses. We were shown how the table-top device can be used to image biological specimens.

Enhancing the light element performance of EDXRF by using a new Silicon Drift Detector with high transmission window.

Colin Slater, Bruker.

Colin described the S2 Ranger, 30 sample holder, benchtop EDXRF instrument. It has a palladium X-ray source with various primary beam filters and a silicon drift detector. The instrument has improved energy resolution and the stability of the detector over time is very good. To illustrate this, Colin said that a cement sample had been run everyday for 77 days and there was no significant change in the data produced. Colin went on to say that the instrument is best in class for light element detection. The CEMENT quantification software package was described. It is pre-calibrated using a set of 15 reference materials.

Mark Farnworth

Pilkington-NSG.

XRF/XRD Applications.

Speakers - Left to Right: Nick Marsh, David Beveridge (chair) and Leah Cliff.

Characterisation of the phosphate surfactant in a latex using XRF and other techniques.

David Beveridge, HARMAN technology Ltd.

The applications session began with a talk by David Beveridge, from Harman Technology, who described his work on the monitoring of the level of surfactant in latex by measuring its phosphorus content with XRF. He was able to use neat latex for the measurement, and calibrated using standards matched for matrix absorption coefficient made from disodium hydrogen phosphate, isopropanol and water. The results, expected to be 433 ppm, came lower at 300 ppm; so David turned to the venerable pH titration technique to investigate the puzzle. He found the two end points he expected from titration of the mono phosphate ester, which has two free -OH groups, but also that the titre for the second (at pH 8.8) was much higher than the first (at pH 4.7). This showed that the surfactant was actually a mixture of the mono and di phosphate ester bringing the problem to a satisfactory conclusion.

Environmental Applications for a new Benchtop XRD/XRF Instrument.

Leah Cliff, Southampton University.

As an interesting contrast, our next speaker, Leah Cliff from the University of Southampton, told us about the CheMin instrument from InXitu which will be on the Mars Science Lab's "Curiosity" Rover to be launched in November this year. She mentioned Inxitu's three (terrestrial) combined XRD/XRF instruments, the Terra, Benchtop BTX and Duetto. The Benchtop BTX features transmission geometry and contains a 2D position and energy sensitive CCD detector to collect synchronous XRD and qualitative XRF data. The sample is presented in a vibration holder to improve particle statistics. She then discussed XRD data from 15 samples of hemipelagic sediments (a mixture of terrigenous and oceanic clays/sand/silt) taken from a Mediterranean seabed core spanning the last 1.1 million years. The mineral analysis was set up by reference to patterns from a laboratory XRD. The diffraction patterns obtained were comparable in resolution to those from a conventional instrument, but were limited to angles below 55o 2? . The XRD results from the BTX were compared to bulk XRD analysis and showed that the climatic modulation of the mineralogy is retained in BTX analysis, particularly in major mineral quantification.

Ros Schwarz

University of Sheffield.

Applications (Two sessions).

Speakers - Left to Right: Phil Russell, Dirk Wissmann, David Beveridge (chair) and Christopher Shaffer.

Applications of High Power XRF in Geochemical and Environmental Laboratories.

Christopher Shaffer, Thermo Fisher Scientific.

Christopher began the second XRF applications session by highlighting the capabilities of WDXRF for routine trace elemental analysis in cases where ICP-MS, ICP-OES and other techniques are not suitable, often the case in environmental and geochemical laboratories where samples represent a wide elemental coverage, wide concentration range and varied sample matrices and sizes. Chris discussed continuous analytical advancements in WDXRF instrumentation making the method well suited to semi-quantitative analysis of low elemental concentrations (mg/kg) in liquids, rock/minerals and pastes. He introduced a new instrument, the Thermo ARL PERFORM'X Advanced WDXRF Spectrometer, capable of carrying out semi-quantitative, small spot analysis (5mm-35mm) and mapping of non-homogeneous samples with minimal sample preparation. Chris also introduced the "UNIQUANT" analysis package for rapid analysis of totally unknown samples, requiring no preparation of standards. Multiple applications were presented, demonstrating the versatility of WDXRF alongside ICP methods, with applications ranging from oils and waste solvents, geological sediments, to cosmetics and food. Chris concluded by re-iterating that WDXRF cannot replace ICP methods but could instead work in collaboration with them, providing semi-quantitative identification and screening to facilitate full quantitative analyses using ICP methods.

New Test Methods for WDXF: Trace elements in Burner Fuels.

Phil Russell, PANalytical.

Phil discussed a landmark ruling in UK courts which redefined the description of petroleum products used for burner fuels, derived from waste lubricants, as a marketable product converted from lubricant waste oils. The ruling prompted new research into methods to develop and test burner fuels for conformance with Environment Agency quality controls. The performance of existing techniques (ICP-MS, ICP-OES, AAS) were compared alongside a high power, 3kW WDXRF, despite scepticism of WDXRF capabilities. Phil briefly discussed the preliminary round robin study, which demonstrated WDXRF suitability to the challenge over all other methods, using a 5ppm regulatory threshold and 0.5ppm detection limit for a range of elements. Subsequently, a full-blown round robin study (AAS, WDXRF & ICP-MS), involving 9 labs and 10 duplicate samples, was undertaken. WDXRF precision was close to the detection limit, revealing levels of performance not previously seen at such low levels (<5mg/kg) and demonstrating the stability in the WDXRF instrument and technique. WDXRF demonstrated better suitability than ICP-MS, which introduced errors by dilutions involved in sample preparation. In February 2011, methods for Burner fuels protocols also accepted test methods using WDXRF (except Hg) as a viable method for trace element analysis in burner fuels.

The Balancing Act Between Versatility and Analytical Performance when Using ED XRF Instrumentation.

Dirk Wissmann, SPECTRO Analytical Instruments GmbH.

Dirk's talk discussed the historical uses of EDXRF spectrometers, predominantly in qualitative screening and quality-control applications. Dirk defined an idealistic ED instrument, comparing and contrasting portable and lab EDXRF instruments to this 'perfect' instrument. He discussed universal calibrations and quantification of unknown samples by looking at Compton scattering, compared to mass absorption co-efficients for 1o excitation radiation, allowing calibration lines for silicate matrix correction and improved ED versatility. In the past 15-20 years, developments in detector technology (resolution, faster electronics) and optimised direct excitation have led to versatile spectrometers with greatly improved sensitivity for use in a broad range of applications; overcoming heavy-metal particulates in ship fuels for Al/Si analysis, trace metals in geological samples and elemental analysis (As, Cd, Sb) in PFO at 5ppm concentrations. Improved analytical performance in specific applications may be required more than great versatility. Dirk concluded that careful selection of components and hardware optimization can help fulfil typical requirements previously limited or impossible for ED XRF spectrometers. Consideration of Compton scattering in matrix corrections has allowed completely unknown samples to be analysed in minutes using EDXRF.

Leah Cliff

University of Southampton.

Applications Session Two.

Speakers - Left to Right: David Bellis, David Beveridge (chair) Nick Marsh and Paul Vanden Brandon.

Novel applications of XRF for mapping metals in industry, health, and the environment.

David Bellis, currently unaffiliated.

David Bellis spoke first describing collaborative work between the Wadsworth Center (New York State Dept. Of Health) coordinated by Dr Patrick Parsons and XOS inc, Anbany, NY in developing new applications of XRF in health sciences. He described the use of a protype XRF mapping system to image lead and strontium distribution at the m-scale in a bone slice, and how the instrumentation was subsequently developed for mapping of sectioned brain tissue. Other collaborations between NYSDOH and XOS in the development of instrumentation for measuring toxic metals in toys and jewellery, and toxic metals in blood in a clinical setting were also highlighted.

X-ray fluorescence analysis of rocks by fusion method using a benchtop WD-XRF. Paul Vanden Brandon, Scientific and Medical for Rigaku.

Paul Vanden Brandon presented work by Kansei et al. of Rigaku on the analysis of rocks via benchtop WD-XRF. The method targeted application in the mining/exploration industries, using small mobile instrumentation that can be installed in remote satellite locations. Fusion sample preparation was preferred over pressed pellets as it provided better calibration curves usign 10 certified reference materials from the Geological Society of Japan.

Substituted talk. Nick Marsh, University of Leicester.

Nick Marsh from the University of Leicester spoke about his experiences in preparing very small samples, often < 100 mg material, for major and minor element analysis by XRF. The samples in question were residual sediment core samples previously analysed for C and O isotope ratio climate record, where diatom contamination by volcanic ash required correction by determining the completely elemental composition and performing mass balance correction of the measured ratio. Fusion preparation at high dilution levels was employed for sample preparation. Small quantities of certified reference materials were used to construct calibration curves, following additional grinding and calibration procedures.

David Bellis

curently unaffiliated.

XRF Keynote - Margaret West.

It began with a helping hand.

Speaker - Left to Right: Margaret West and David Taylor (chair) chat after the conference dinner.

Margaret began her talk by saying that the novel techniques available today stem from Röntgen's work in 1895. Since that time successive workers have developed ideas, built prototype devices and systems that have encouraged others to further explore the capabilities offered by the family of X-ray techniques. The word 'X-rays' has its origin in the German word 'X-strahlen' coined by the German scientist Wilhelm Conrad. Röntgen was working with sealed glass tubes and his 'helping hand' was that of his wife, Anna, who placed it in front of an X-ray beam (!) which then produced an 'X-ray' of her hand on photographic film. In the UK between 1913 and 1914, Sir William Henry Bragg and Sir William Laurence Bragg were working with X-rays to look at crystal structures. They jointly received the Nobel Prize for Physics in 1915. During the early part of the 20th Century the X-ray Card Index system was being developed, originally under the JCPDS name and then subsequently under the jurisdiction of the International Centre for Diffraction Data (ICDD). H.G.J Moseley was a leading light in the field and he confirmed Bohr's theory of electron transitions.

During the 1960's automated wavelength dispersive X-ray Fluorescence (XRF) systems came on the scene followed in the 1970's by various mathematical models - Willy de Jongh (1973) and the Rasberry and Heinrich equations. During the 1980's microprocessor technology became more widespread and Energy Dispersive (ED) Systems became available. On the 2nd February 1990 there was an evening discourse at the Royal Institution when Max Perutz discussed 'blindfold automation' for problem solving!

In the modern era X-ray systems are available to suit all budgets, from sophisticated multi-technique systems to bench top to handheld. Total Reflection XRF is incredibly sensitive and has been a boon to the semi-conductor industry. Micro XRF is also available in which images of wafer contamination can be produced with 2D and 3D mapping of various elements easily carried out.

In tandem with recent developments in laboratory X-ray sources, synchrotron radiation has developed over the years. Combined techniques are seen more and more on beam lines. Among the many emerging techniques are Time Resolved TXRF, X-ray Absorption Near Edge Structure (XANES) and X-ray Absorption Fine Structure (XAFS). 3D elemental mapping is becoming common place.

The Royal Society of Chemistry (RSC) support XRF through Atomic Spectrometry Updates (www.asureviews.org).

There has been staggering developments in computing power. There are now on-line data systems and fundamental parameter analysis is available to all. Detectors have improved tremendously. In the early days the detectors for EDXRF were bulky. They had an energy resolution in the range 170 to 200 eV. We now have Peltier cooled Silicon PIN or SDD detectors with an energy resolution of 130eV at ten times the count rate. Bench top instruments have 50W beam power and a low background signal. They are good for delicate samples. X-ray optics have also improved. We now have polycapillary systems and X-ray wave guides. The X-ray beams are smaller with higher special resolution.

Margaret concluded by saying that today we delight in sensitive systems that tempt researchers to explore new horizons. Where will it end?

Mark Farnworth

Pilkington-NSG.

Novel Techniques and Applications.

Speakers - Left to Right: Joanna Collingwood, Rainer Schramm, Adrian Wright and Dave Taylor (chair).

XRF analysis of neurodegenerative brain tissue using synchrotron radiation.

Joanna Collingwood, Warwick University.

Joanna set the scene of her talk by listing the range of degenerative neurological disorders with possible links to metal ions which included Alzheimer's, Parkinson's, CJD and MS. She then made some comparisons of staining with light microscopy, microprobe analysis and synchrotron microfocus XRF (at APS and Diamond). For microfocus mapping 10-12Kev is used for the transition metal elements of interest, including Mn, Fe, Cu, and Zn, and a multichannel detector is required to collect the full spectra with high sensitivity to the elements. This technique was able to locate the distribution of nanoscale particles and dilute elements across large areas of tissue, and allowed site-specific collection of XANES spectra to enable chemical and mineral characterization of the nanoparticles. Sample preparation methods include fresh-frozen sections, substrates of Permanox or quartz and Kapton coverslips. Joanna then went on to show the results from x-ray maps and outlined the advantages of the technique over conventional staining and the major challenges of the technique.

ISO 17025 accreditation for fused bead methods.

Rainer Schramm, FLUXANA GmbH.

Rainer followed on from his workshop demonstration of fused bead and pressed pellet preparation with a tour practical tour through the ISO 17025 standard for a fused calibration. His step by step approach from sample preparation, choice of calibration lines and backgrounds, calibration standards, measurement times and statistics, reproducibility and repeatability through to method validation with certified reference materials gave a logical understanding of the process to generate a good standardised analytical method. He went on to the explain the methods used to ensure that the calibration accuracy was maintained over time and left the audience with a good understanding of how to go about setting up a method to the standard required for accreditation.

Challenges in the Characterisation of Amorphous Metal Phosphates and Fluorophosphates.

Adrian J Wright, Birmingham University.

Adrian's talk focussed on the use of amorphous metal phosphates and fluorophosphates as bioceramic materials for bone replacement taking advantage of the properties of more stable amorphous materials providing a resorbable structure for new bone replacement and a stronger long term repair. The work centred on the formation of calcium, magnesium and strontium pyrophosphate as the target metals. XRPD, XRF and NMR were used to evaluate the reaction products as being amorphous (XRPD) with NMR confirming connectivity between phosphorous nuclei and WDXRF giving the elemental composition and proving the metal substitution. Comparison of fused beads to pressed pellets showed that fused beads gave more reliable results. Adrian then went on to discuss the poorly studied fluorophosphates, a common addition to toothpastes and scope to generate new materials and the challenges of determining fluorine by XRF.

Dave Taylor

Session chair.

XRF/PCG Cultural Heritage.

Speakers - Left to Right: Liana Vella-Zarb, Andy Smith, Margaret West and Dave Taylor (Chair)

The PCG/XRF session on Cultural Heritage at the 2011 BCA spring meeting was an absolute gem and if you missed it, you missed out! It nearly didn't happen as, less than 24 hours beforehand we found out that two of the speakers and one of the chairs were unable to make it. But, after some hurried arm twisting two replacement speakers graciously agreed to step into the breech. And I have to say, they did us proud. The scene had already been set by a fantastic plenary lecture on cultural heritage by Gilberto Artioli that morning and I was intrigued enough to forsake my usual biological structure group talks and stick around for the rest of the session.

Conservation and Restoration - Science brings the past into our future.

Margaret West, West X-ray Solutions Ltd

The session opened with a interesting talk by one of our press ganged speakers, Margaret West who, as well as giving the XRF plenary and running a workshop at the meeting, had kindly agreed to step in. She discussed her involvement in several conservation and restoration efforts around the UK. I was most intrigued by the idea of using XRF to identify components in paint in order to be able to formulate an exact match to a pot of paint that had been mixed back in the Victorian era.

The art of investigation: using combined diagnostic techniques for the conservation of cultural heritage.

Liana Vella-Zarb, Heritage Malta.

Margaret was followed by our second "surprise" speaker, Liana Vella-Zarb from Heritage Malta. Liana had managed to whip up a talk based on the poster she presented at the meeting that described the work on Heritage Malta in preserving the amazing array of historical sites on the island for future generations. I was fascinated by the story of her work on the ochre ceiling paintings in the Oracle room of the Hypogeum. This fascinating underground temple was rediscovered in the last century but the beautiful ochre paintings had appeared to fade over time. Liana explained how her group had used X-ray studies to determine that the ochre paintings were not in fact fading, but rather were being covered by a white deposit. This has enabled the group to establish a new approach to the care of the monument that should keep the paintings clear. It is on my list of places to visit!

A host of golden angels - Coin making in Tudor times explored by XRF and neutron diffraction.

Andy Smith, Daresbury Laboratory.

The final talk in the session was from Andy Smith who presented his work on Tudor coin making. He was working on the astonishing array of gold coins that were found on the Mary Rose using X-ray and neutron studies to determine their composition. It was interesting to note that as Henry VIII fortunes waned, the gold coins become progressively less pure! However, Andy explained that there was a limit to how far the Tudor treasury could adulterate the coins. If the gold content was too low the coins became too hard to stamp with the face of the King. I very much enjoyed this session and am looking forward to sneaking into more non-bio sessions at future BCA meetings, I hope they will all be as interesting as this one.

Arwen Pearson

University of Leeds.

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