A Comparison of Software Packages for X-Ray Fluorescence Analysis of Silicates on Fusion Disks

Transcription

1 743 A Comparison of Software Packages for X-Ray Fuorescence Anaysis of Siicates on Fusion Disks HCC Coete Counci for Geoscience, Private Bag X 12, Pretoria, 0001, South Africa Abstract A fixed set of corrected counts were processed by various software packages to compare the produced resuts with the associated concentrations. The correction coefficients were aso compared with each other. The evauated software packages were grouped according to the use of fux components. For the caibration of a wide range of geoogica sampes ony minor differences between the two groups were observed. Introduction In the past at the Counci for Geoscience of South Africa (CGS) the cassic Norrish and Hutton (1969) technique was used to anayse for major eements on fusion disks. Athough producing satisfying resuts for norma geoogica sampes, it was found to be restricting as ony a fixed set of major eements coud be anaysed To aid in the search for a fexibe major eement anaytica technique the CGS purchased various software packages to cacuate inter-eement correction coefficients correcting for matrix effects in fusion disks and pressed peets. In this process resuts from various software packages were compared to each other and evauated. The aim of this study is to compare (i) the resuts of the major eements produced by the host software package as isted in Tabe 1, and (ii) the intereement correction coefficients produced by each software package. Tabe 1: List of evauated software packages SOFTWARE PACKAGE ORIGIN NBSGSC CiLT CiROU CiLAC ALPHAS ALPHA Nationa Bureau of Standards and the Geoogica Survey of Canada Les Logicies R. Rousseau, Inc., Canada Phiips CSIRO, Austraia

2 This document was presented at the Denver X-ray Conference (DXC) on Appications of X-ray Anaysis. Sponsored by the Internationa Centre for Diffraction Data (ICDD). This document is provided by ICDD in cooperation with the authors and presenters of the DXC for the express purpose of educating the scientific community. A copyrights for the document are retained by ICDD. Usage is restricted for the purposes of education and scientific research. DXC Website ICDD Website -

3 744 Each software package uses fundamenta parameters to cacuate the inter-eement correction coefficients, i.e. the correction coefficients are cacuated using an equation defining the reationship between the primary waveength distribution, mass absorption coefficients, absorption jump ratios, fuorescent yieds and the geometry of the spectrometer. This physica reationship has been described by Sherman (1955) and Shiraiwa and Fujino (1966), quantified by Criss and Birks (1968) and modified by Rousseau (1984). Method of evauation Dupicate fusion disks of each reference materia were prepared. (See Tabe 2 for preparation of fusion disks.) Anayte and background peaks were determined by waveength sequentia X-ray fuorescence spectrometer. (Phiips PW1480 XRF spectrometer with Rh-tube operating at 50 kv and 55 ma.) After background and ine overap corrections, the average nett oxide peak (in kcps) was cacuated for each reference materia and processed by the software packages. The tube spectra distribution is cacuated by the host software package. For the caibration simpe inear regression (Y = mx + C ) was used. The resuts of each software package were compared with the corresponding certified oxide vaue of the reference materia. Tabe 2: Preparation of the fusion disks I Roasting of sampe at 1000 C for 3 hours to oxidize Fe + and S and to measure oss of ignition (LOI) gravimetricay. Weighing of 2 grams sampe with 8 grams fux from Sigma Chemicas Pty Ltd, Western Austraia. (35.29% ithiutntetraborate and 64.71% ithiumtnetaborate) One to two drops HBr as wetting agent was added. Fusing with the aid of an automatic fuxer. A short description of the evauated software packages NBSGSC - For cacuation of the intereement correction coefficients Sherman s equation as modified by Rousseau (1984) is used. These coeficients are then paced into the Comprehensive LaChance Agorithm (COLA) to convert the measured intensity to concentration. - Coefficients for three different types of sampes are cacuated: aoys (eement system), pressed peet oxides (oxide system) and fused disk oxides (fusion system). (Martin, 1988)

4 745 In the next three software packages Rousseau s equation (1984) is aso used to cacuate the correction coefficients. CiLT - The cacuated theoretica binary infuence coefficients are paced into the Lachance-Trai1 agorithm for the determination of the sampe s composition. - The assumption is that the coefficients are constant for a imited concentration range (0-10%). - It is optima for use with fused gass disks. (Rousseau, 1992a) CiROU - The cacuated theoretica muti-eement infuence coefficients are paced into the Caisse-Quintin agorithm to estimate the sampe s composition. - This estimated compostion is then used to cacuate inter-eement correction coefficient in the Fundamenta Agorithm, i.e. the coefficients are dependent on the composition of the sampe. - It is appicabe to any type of sampe with a broad concentration range (0-100%). (Rousseau, 1992b) CiLAC - The cacuated theoretica binary infuence coefficients are paced into the Lachance agorithm for the determination of the sampe s composition. - The assumption is that the coefficients are constant for a broad concentration range (0-100%). - It is usabe for any type of sampes. (Rousseau, 1992~) ALPHAS (Phiips) - Intereement correction coefficients are cacuated by Sherman s equation as modified by de Jongh (1973). - These coefficients were paced into the De Jongh mode provided by Phiips spectrometer software package (X44) for conversion of measured intensity to concentration. ALPHA (CSIRO) - Intereement correction coefficients are cacuated by a modification of the Nava Research Laboratory program (NRLXRF ). - The coefficients were used in the De Jongh mode provided by Phiips spectrometer software package (X44) for conversion of measured intensity to concentration.

5 746 The fux components and grouping of the software packages The fux contains 35.29% ithiumtetraborate and 64.71% ithiummetaborate, i.e % Li,B,O, % LiBO, = % L&O % B,O, Therefore in the fusion disk there are 20% roasted sampe, % L&O, and % %03 totaing to 100%. In Appendix 1 a reference standard is used to iustrate the steps of adjusting the major eement vaues with and without the fux components. Tabe 3 : Organisation of evauated software packages. GROUP 1 GROUP 2 Mass of both the fux and sampe are required. Compostion of the fux is required. Correction coefficients for fux components are not cacuated. For each oxide matrix eement coefficients ai is cacuated. NBSGSC - fusion system CiLT Phiips ALPHAS CSIRO s ALPHA Mass of both the fux and sampe are not required. Composition of fux is not required, but the operator regards the fux components fixed as % Li,O and % B,O, as part of the tota major eement composition. Correction coefficients for fux components are cacuated. Fina major eement concentrations are normaised without the fux components. For each oxide hypothetica coefficients a,, a,,a 3 and matrix eement coefficients a+ are cacuated. NBSGSC - oxide system CiLAC CiROU The resuts The ranges of the major eement oxides are depicted in Tabe 4: Tabe 4: Ranges of major eement oxides (wt %) SiO, CaO 0-35 TiO, 0-4 NM 0-10 ALO, 0-90 W 0-15 Fe,O,(t) 0-30 PA 0-2 MnO 0-9 WA 0-4 MgO 0-45 Two reference materias NBS-688 and GSR-6 were used to compare the certified vaues with the cacuated

6 747 vaues produced by the software package. (Tabes 5 and 6) Tabe 5 (a): Cacuated vaues (wt %) of reference materia, NBS-688 (basat) Group 1 Group 2 Certified vaues SiO, 48.4 TiO, , bw) MnO w@ 8.4 CaO Na,O 2.15 W p Cr LO Tota CiLT Phiips CSIRO fiyef CiLAC CQ FA CQ = FA = CiROU, Caisse Quintin Agorithm CiROU, Fundamenta Agorithm Tabe 5(b): Reative error, NBS-688 Oxide Group 1 Group 2 SiO, TiO, 403 WWt) MO ME9 CaO Na,O GO PA CrP3 CiLT Phiips CSIRO NBSGSC oxides CiLAC CQ FA

7 748 Tabe 6(,a): Cacuated vaues (wt %) of reference materia, GSR-6 (imestone) Certified vaues Group 1 Group 2 CiLT Phiips CSIRO fiyef CiLAC CQ FA Si TiO, A@, bo&) MnO MgO CaO Na,O W p WA LO Tota CQ = FA = CiROU, Caisse Quintin Agorithm CiROU, Fundamenta Agorithm Tabe 6(b): % Reative error, GSR-6 Oxide Group 1 Group 2 SiO, TiO, A1203 Wb(t) MnO MgO CaO Na,O W PA WA CiLT Phiips CSIRO NBSGSC oxides CiLAC CQ FA

8 749 The inter-eement correction coefficients Group I The inter-eement correction coefficients a, for SiO, are compared in Tabe 7. Tabe 7: Inter-eement correction coefficients for anayte SiO, Component NBSGSC fusion svstem _I CiLT Phiips ALPHAS CSIRO s ALPHA Na,O mo , SiO, PA W CaO TiO, Cr, MnO Fe@, Group 2 Apha coefficients a,, CI,, a3 and atik for SiO, are compared in Tabe 8. First row Second row Third row NBSGSC - oxide system CiLAC CiROU for use in Caisse-Quintin Agorithm Coefficients for Fundamenta Agorithm in CiROU are not incuded in the comparison as they are dependent on the composition of the sampe, i.e. for each sampe new correction coefficients are cacuated.

9 750 Tabe 8: Inter-eement correction coefficients for anayte SiO, Li,O B,O, Na,O MgO A,O, SiO, a % a3 n.d. n.d. n.d. n.d. n.d. n.d n.d. n.d. n.d. n.d. n.d. n.d. L&O W Na,O MgO A&O, SiOz p GO CaO TiO, GO MnO b n.d. =notdeterminedby software package. PA K,O CaO TiO, Cr,O, MnO Fe,O, n.d. n.d. n.d. n.d. n.d. nd. n.d n.d. n.d. n.d. n.d. n.d. nd. n.d

10 751 Discussion and concusion - Ony minor differences for the resuts for the major eement oxides over the whoe concentration range were observed. However, when banks and reference materias with ow oxide vaues, especiay Na,O, Cr,O, and Fe203(t) were anaysed as unknowns, the produced vaues from Group 2 software packages were significanty higher than Group 1. - In CiROU the Fundamenta Parameter Agorithm produced ower SiO, and Ah Q -vaues than the Caisse-Quintin Agorithm which is used to cacuate a first estimate of the sampe composition, eading to ow totas. In this version of CiROU which was deveoped when powerfu PC s were not avaiabe, the number of iterations is probaby insufficient. - For SiO, at high vaues Group 2 software packages performed more favouraby than Group 1 whie at ow vaues Group 1 performed better. - In Group 1 the correction coefficients of NBSGSC and CiLT are basicay the same, because of the use of Rousseau s modified agorithm (1984). They are aso much ower than the high vaues produced by Phiips ALPHAS and CSIRO s ALPHA. Such high coefficients shoud be used with care, because cacuated intensity potted against measured intensity coud be exaggerated eading to incorrect concentrations. - For the type of anayses at the CGS, NBSGSC s oxide system is being used as it proved to be sufficienty fexibe and accurate. References Criss, J.W. and Birks, L.S. (1968) Ana. Chem., 40, Easte, J. (1988) A Low Diution Fusion Technique for the Determination of Major, Minor and Trace eements in Lamproite and Kimberite sampes byx-ray Fuorescence Spectrometry. Unpub. MSc Thesis, Dept. Geochemistry, University of Cape Town, South Africa. De Jongh, W.K. (1973) X-Ray Spectrometry, 2, 151. Martin, R.L. (1988) NBSGSC Version 4. OManua Rainier Software, 115~~. Norrish, K. and Hutton, J.T. (1969) Geochim. Cosmochim. Acta, 33,43 1. Sherman, J. (1955) Spectrochim. Acta, 7,283. Shiraiwa, T. and Fujino,N. (1966) Jpn. J. App. Phys., 5, 886. Rousseau, R.M. (1984) X-Ray Spectrometry, 13, 155. Rousseau, R.M. (1992a) CiLT Version 4. I Manua, Les ogicies R. Rousseau inc. Rousseau, R.M. (1992b) CiLAC Version 4. I Manua, Les ogicies R. Rousseau inc. Rousseau, R.M. (1992~) CiROU Version 4. I Manua, Les ogicies R. Rousseau inc.

11 752 Acknowedgments The author wishes to thank the foowing: the CGS and D de Bruin for their support in undertaking this project, her coeagues at the Laboratory of the CGS and JP Wiis of the University of Cape Town for their vaued suggestions. Specia thanks to H L Szczesniak for her inguistic input and my husband, M Coete, for his support. Appendix 1 Adjusted major eement vaues with and without the fux components in reference materia GSR- 1, a granite. The idea of breaking up the fux components into oxides was borrowed from Easte(988). Oxide SiO, TiO, 40, Fe@,(t) MnO mo CaO Na,O W PA C@3 L&O W, L.O.I. Tota Certified vaues for use in caibration Origina vaues Without LO1 coorers After anaysis as an unknown With fux Without fux with LoI :omponents components