feb2017
XRF E-Newsletter
Volume 24.
February 2017 - detailing XRF events and news.
Dear XRF subscriber,
Welcome to the Twenty-fourth issue of the British Crystallographic Association (BCA) Industrial Group dedicated XRF Newsletter. There is a copy of this Newsletter on the web to share with your colleagues.
NEXT XRF Meeting 14th June 2017 and XRD Meeting the following day at the same venue.
The meeting and exhibition will be held at the University of Leicester and will be followed on the 15th by an XRD meeting. Put these dates in your diary now! We are looking to attract user and academic talks at this meeting, so now is the time to get your thinking cap on and figure out how you can put together an interesting talk on your work. Please offer your talk at this meeting by contacting any committee member or reply to this mailing.
The well received Exhibitor Forum will be repeated at this meeting. Keep an eye on the meeting page for regular updates.
XRF Proficiency Testing.
We now have a dedicated web page listing web sites offering XRF proficiency testing services. If you know of any we are missing please let us know.
DOT-3 Participant Sample Report.
Report on DOT-3 Gypsum-based cement rock
Introduction.
The aim of this "participant sample" was intended to act as an aid to methods development and training, and was not a proficiency test or Round Robin. Participants were asked to determine as many elements as possible by any suitable X-ray Fluorescence (XRF) method or other technique. The results were analysed "blind", identified only by a laboratory number. The sample DOT-3 is a gypsum-based cement rock, containing significant amounts of quartz, dolomite and clays (kaolinite and illite).
Calcium sulfate exists as two hydrates (gypsum and stucco or Plaster of Paris) and two anhydrate forms (anhydrite). Gypsum, stucco and (soluble) anhydrite are interconvertible by heating. Further heating of the anhydrite converts it to an insoluble form.
Because natural gypsum may contain significant calcite (CaCO3) or dolomite (CaMgCO3) which contribute to the XRF result for CaO, SO3 content is most important commercially as it determines purity. Other components of interest in natural material are Al, Si, Fe, Na and Mg, indicating the presence of dolomite and clay. Silica is particularly problematic as it wears down milling equipment in the plant and has health implications as respirable quartz.
Mineral samples are presented to the XRF instrument in two ways, either as a pressed powder pellet or a fused bead. Each preparation has disadvantages in relation to gypsum and this report explores and explains the results.
Conclusions.
The XRF results for the DOT-3 participant sample, a gypsum-based cement rock, indicated that XRF analysis is capable of giving a reliable SO3 result when either fused beads or pressed powder pellets are used, provided the preliminary ignition, fusion and calibration are carried out carefully. Fused beads gave more consistent results for elements at minor levels, but some data from pressed powders also agreed well. Outlying results could arise from calibration issues or from contamination.
Trace element performance down to around 5 ppm was good, although some outliers were noted.
The overall analysis was in very good agreement with the supplier's accepted values.
Ros Schwarz (retired) and Heather Harrison (British Gypsum)
The full report is available as a PDF document on the BCA Industrial Group XRF website at: LINK TO REPORT 722kb PDF file
Samples of DOT -3 are still available providing you agree to send your results to Ros Schwarz, who is listed on our contacts page.
DOT-5 Next Participant Sample.
Do you have a potential sample for distribution at our 2017 meeting? If so please contact Ros Schwarz with some details.