Invited speakers 2010

 

Maggi Loubser.  Group Chief Chemist, PPC Cement, South Africa Maggi.Loubser@ppc.co.za

Her career in X-Ray fluorescence Spectroscopy started as a laboratory technician at the Atomic Energy Corporation of South Africa in 1988.  There she learned XRF in a process control laboratory.  During this time she studied part-time towards a BSc in Chemistry, which she obtained in 1996 from the University of South Africa (UNISA), and a BSc(hons) in 2003 from University of Pretoria.  She has just completed a MSc in Chemistry (University of Pretoria) with a dissertation entitled:  Chemical and physical aspects of Lithium borate fusion.

In 1994 she joined the Geology department of the University of Pretoria (UP) where for the next fourteen years the X-Ray laboratory was build up to a state of the art facility presenting annual short courses in XRF and Representative Sampling and Sample preparation.  Since 2005 Maggi has been presenter at the annual XRF Short Course at University of Western Ontario in Canada.

She joined PPC Cement in November, 2008, where her duties involve the development of training material, training, mentoring and capacity building of the chemists in the group.  She has the responsibility to ensure world-class analytical laboratory practices at PPC’s laboratories manage compliance to laboratory minimum standards and identify and implement best practices in the analytical laboratories.  She has presented numerous papers at international conferences and national symposia and served on the executive of the South African Spectroscopic Society and organising committee for CSIXXXIII and Geoanalysis 2009.

 

She will present the following paper:

 

Representative sampling and the errors introduced in sampling and sample preparation 

 

Maggi Loubser.  PPC Cement, Group Quality Services, PO Box 40073, 2022

Cleveland, South Africa.  Email: maggi.loubser@ppc.co.za

Most of the analytical techniques currently used in process control environments are mature, stable techniques.  In the past many manufacturing concerns typically focussed only on major elements. With the improved sensitivities and precision of analytical equipment along with the analytical demands related to the use of alternative raw materials and to environmental monitoring, the range of elements analysed has expanded from major elements to include minor and trace elements.

 As analytical chemists we are prone to being arrogant regarding our analytical abilities being supported by standard quality control practises routinely implemented in the laboratory.  In addition accreditation of a laboratory is often used as first line of defence when results are challenged by clients.

 In reality it is often forgotten is that unless the sample is truly representative of the bulk it represents, the data are of little value. Typically the total sampling error is often hundred times larger than the analytical error.

Sampling theory originated with Pierre Gy in the nineteen fifties, the principles of which are still applicable even though analytical techniques have improved greatly.  Most natural materials are compositionally and texturally heterogeneous and for a sample to be representative of the bulk, the correct size sample has to be taken, taking particle size and the concentration of minor and trace elements of interest into consideration.  The problems do not end once the primary sample was taken, as only unbiased statistically reproducible mass reduction will ensure representative analytical specimens.

In this paper an overview of the theory of sampling will be presented elucidating the different approaches used.  The objectives of sampling in a process control environment will be discussed and will be related to the theory of sampling.  Some of the practical problems associated with implementing theoretical sampling principles in an industrial environment will be described and some examples given on how appropriate compromises are made.

Different methods of sampling will be discussed with real life examples from different manufacturing industries including cement, metallurgical and mining environments.

These concepts will be carried through to basic sample preparation and the errors introduced at each subsequent step in the process.

 

 

Elke Schwöbel

Bruker AXS GmbH, Karlsruhe, Germany

 

CV:

Master degree in Geology at the Rupprecht-Karls-University Heidelberg

Main research interest: Clay Mineral Stratigraphy in Triassic sediments investigated with X-ray diffraction techniques

 

Application scientist for X-ray diffraction at Bruker AXS GmbH since 1997

Responsibilities:

- all applications relevant for industrial customers

- sample analysis, method development, and demonstration of XRD instruments

- XRD instrumentation and software instructor also giving numerous workshops with international attendance

 

 

 

Quantitative XRD-Analysis of Phases with known, partial or No Known Crystal Structures

 

 

In recent years the Rietveld method emerged as a routine tool for quantitative phase analysis of X-ray diffraction data. The basics of the method were published in the late 1960´s, when the Dutch crystallographer Hugo Rietveld presented computer based analytical procedures making use of a complete powder diffraction pattern. Fast and reliable results became possible by combining modern computer technology and the optimised mathematical algorithms with the fundamental parameters approach.

 

Quantitative phase analysis via the conventional Rietveld method is generally restricted to crystalline phases with well known crystal structure, where peak intensities are calculated from the crystal structural data. Nonetheless, unidentified, structurally uncharacterised, and amorphous materials may be quantified altogether by spiking the mixture with an internal standard. However, this can only give the total abundance of all compounds with unknown crystal structure - a quantification of individual phases is not possible.

 

In contrast, the method of quantitative analysis of phases with Partial Or No Known Crystal Structures, PONKCS [1], allows the accurate quantification of individual compounds. Using PONKCS, crystal structure information is replaced by measured intensities from a reference sample, simply requiring a one-time calibration using an internal standard. As a result, extremely accurate results can even be obtained in cases where the classic Rietveld method cannot be applied at all.

 

The methodology and practical examples will be presented.

 

[1] Scarlett, N.V.Y. & Madsen, I.C. (2006): Quantification of phases with partial or no known crystal structures. - Powder Diffraction, 21(4), 278-284

 

 

Kevin Young

Kevin has more than 20 years experience analysing and characterising alumino silicate minerals by X-ray techniques (and other instrumental and chemical methods) and has for the last ten years been responsible for the calibration of X-Ray instruments in Sibelco UK and more recently some of the European instruments conducting "low iron" (less than 100 ppm Fe2O3) analyses on Silivca based minerals for Sibelco Operating Units.

 

He will present the following paper:

Practical Aspects of the X-ray Characterisation of Silicate and Alumino-silicate Industrial Minerals

Chemical analysis by X-ray fluorescence of silicate and alumino-silicate minerals is challenging because of either the low levels of detection and high precision required for silica glass sands (quartz) or the complex matrix effects observed for ceramic-grade alumino-silicates (clays and feldspars). This presentation will focus mainly on the effects of instrument type, sample preparation and calibration (standards, CRMs, corrections).

A more detailed characterisation of alumino-silicates can be achieved by combining XRF and XRD analysis; some of the methods available for combining the information will be discussed through 'real-life' examples. For variety, some X-ray diffraction characterisation of quartz reference materials for RCS dust filter analysis calibration will be included