The Analytical X-ray Company

WROXI – synthetic wide-rangeoxide standards for fused beadmajor and minor elementanalysis

IntroductionX-ray fluorescence spectrometry (XRF) is used extensively for the analysis of a very wide range of oxide materials and over a range of concentrations from 0 - 100 wt% oxide. Simple sample preparation, high accuracy and precision, and when required, good to excellent detection limits across large parts of the periodic table are the principal reasons for this choice. Accurate analysis is becoming increasingly important for many reasons: for superior production, process and grade control with associated cost savings; minimizing and controlling contamination and environmental pollution during manufacture; quality control of products; and pure research.

Accurate quantification requires accurate, spectrally clean net peak intensities, accurate corrections for inter-element matrix effects and good standards with a wide range of concentrations.

WROXI is a set of synthetic standards, together with an application setup for the AxiosmAX-Minerals sequential WDXRF spectrometer, which enables calibrations for twenty-one major elements in the analysis of oxide materials based on fused beads. WROXI can be used either as a primary fused bead calibration or to verify customer in-house standards for pressed powder applications. WROXI is not a pre-calibration.

The AxiosmAX-Minerals WDXRF sequential spectrometer with WROXI standards and the SuperQ software FP algorithm makes up a unique system that consistently produces very high-quality major and minor element analyses, e.g. Mg, Al, Si, Ti, Fe, Mn, V, Cr, Ni, Cu, Zn, Sr, Zr, Ba and Pb, in a wide variety of oxides, silicates, carbonates, sulphates, phosphates, rocks and soils and similar raw materials used in many different industries, such as cement, gypsum, iron and manganese ores, ceramics, bricks, glass, and some heavy mineral ores.

AxiosmAX-MineralsAxiosmAX-Minerals is a fully integrated wavelengthdispersive XRF spectrometer, complete with X-Y sample handler and state-of-the-art software. Engineered for excellence in terms of both analytical and operational performance, it has been configured specifically to meet the needs of users in the mining and minerals industries.

Easily integrated into automated laboratory systems and with a small footprint, AxiosmAX-Minerals provides consistent high-quality data across the full elemental range, from fluorine to uranium, in concentrations ranging from ppm to 100 wt%. It is ideal for medium-to-high-throughput applications in both production control and R & D environments.

AxiosmAX-Minerals comes complete with a set of 20 synthetic multi-element wide-range oxides (WROXI) standards and an application setup for the handling of fused bead major element analyses. Using PANalytical’s unique SuperQ software FP algorithm, the WROXI application can determine concentrations of up to 21 common oxides in a wide range of rocks, ores and minerals.

AXIOSmAX-MINERALS

WROXI – synthetic wide-rangeoxide standards for fused bead

sequential spectrometer with WROXI standards and the SuperQ software FP

WROXI Specifications:

Measurement conditions40 mm fused beads were measured in 37 mm sample holders using a 37 mm collimator mask. Single unshared backgrounds were used for all channels except Zn, Cu, Ni, Mg and Na for which two background positions were used. One of the Na background positions was shared with Mg. Kα lines were measured for all elements except Pb (L β1), Ba, Zr and Sr (L α1). The SuperQ software for AxiosmAX-Minerals contains an application template for the WROXI application and setup only requires the measurement of the standards. The measurement program takes approximately nine minutes. Measurement times for the individual elements used to obtain the data presented are given in Table 1.

AcknowledgementThe WROXI application and standards were conceived and developed in collaboration with M.N. Ingham and the XRFS Section of the British Geological Survey Analytical Geochemistry Laboratories.

1. Elements and their concentration ranges (wt %):

Na2O 0 − 58 MgO 0 – 78 Al2O3 0 – 78 SiO2 0 – 80 P2O3 0 – 40 SO3 0 – 59 K2O 0 – 40 CaO 0 – 80 TiO2 0 – 40 V2O5 0 – 10 Cr2O3 0 – 10 Mn3O4 0 – 80 Fe2O3 0 – 81 NiO 0 – 12 CuO 0 – 8 ZnO 0 – 10 SrO 0 – 20 ZrO2 0 – 43 BaO 0 – 43 HfO2 0 – 10 PbO 0 – 10

2. Presentation: • Robustaluminiumcarryingcase containing standards plus user information and concentrations on CD-ROM • 19standards - Supplied as powders; 5 g each - Supplied in air-tight plastic bottles, packed under nitrogen - Drift monitors (x2) - Fusion bead containers

Table 1. Total measurement time (peak + backgrounds)

Preparation of standards and samplesFor the AxiosmAX-Minerals - WROXI configuration to operate correctly, high-purity blanks (the customer’s flux), and single- or multi-element concentration standards are essential. The WROXI standards set is comprised of 20 synthetic multiple-oxide standards. One advantage of using synthetic standards made from traceable compounds, is that the method is brought significantly closer to being a primary rather than a comparative method. The standards are delivered as powders to be prepared as fused beads by the customer, using the customer’s flux, dilution ratios and methodology. They are therefore suited and applicable to every ‘oxide’ laboratory.

The standards are made from pure chemicals, pre-conditioned, weighed, ground and packaged under nitrogen. Detailed instructions on the use and handling of the WROXI standards are included with the application package.

The WROXI standards and certified reference materials illustrated in the figures and tables below were prepared

using 1.0 g of sample fused in 10.0 g flux (66 % lithium tetraborate, 34 % lithium metaborate) and cast into 40 mm diameter fused beads. Pure lithium tetraborate can be used for routine samples, depending on the sample type, although the mixed flux is preferred for preparing the WROXI standards. Also, depending on the type of sample, 0.5 or 1.0 g NH4NO3 can be added as an oxidizer. The excess NH4NO3 disappears completely during the fusion process and so has no effect on the sample dilution. 15-200 mg of LiBr or LiI can be used as a releasing agent. The fusion temperature was 1150 °C using the LiT/LiM flux mixture.For the accurate analysis of sulfur, for example in cements and gypsum, it is advisable to lower the fusion temperature to 1050 °C to avoid the loss of sulfur during the fusion process.

Many of the oxide samples contain H2O, carbonates and other volatile compounds, which are lost during the fusion process as loss on ignition (L.O.I.). L.O.I. was used as a balance compound in this application.

Compound Total time (s)

Na2O 72

MgO 42

Al2O3 36

SiO2 36

P2O5 12

SO3 24

K2O 16

CaO 20

TiO2 16

V2O5 16

Cr2O3 16

Mn3O4 16

Fe2O2 16

NiO 12

CuO 12

ZnO 12

SrO 56

ZrO2 28

BaO 48

HfO2 26

PbO 8

Total Application 540

AccuracyThe accuracy of the AxiosmAX-Minerals spectrometer using WROXI standards and SuperQ (FP) calibration model for major and minor element analyses in oxides and related materials is excellent. This is illustrated in an accuracy overview plot for a number of oxides (Figure 1), in plots for individual oxides; Al2O3, P2O5, K2O, TiO2, Mn3O4, and Fe2O3, (Figures 2 - 7), and in a comparison of certified and measured values for 14 Certified Reference Materials (CRMs) of widely varying composition (Table 2). The absolute and relative accuracy of the WROXI method is also shown for a range of oxides in Table 3. For all comparisons between certified and measured values, the CRMs were measured as routine samples against the WROXI calibration. The combination of WROXI standards and the PANalytical FP calibration model enables accurate extrapolation of calibrations outside the range in the standards. For example, high Al2O3 and high Fe2O3 CRMs have been analysed successfully with WROXI (Figures 2 and 7).

100

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00 10 20 30 40 50 60 70 80 90 100

WR

OX

I (w

t%)

Certified (wt%)

Theory

y = 1.004x0.006R2 = 0.9999

Na2O

MgO

Al2O3

SiO2

CaO

TiO2

Mn3O4

Fe2O3

Figure 1. Accuracy overview: comparison of certified and measured values for 8 oxides in the wide variety of CRMs listed in Table 2

CRM Type Na2O (wt %) MgO (wt %) Al2O3 (wt %) SiO2 (wt %) P2O5 (wt %) SO3 (wt %)

Cert. Meas. Cert. Meas. Cert. Meas. Cert. Meas. Cert. Meas. Cert. Meas.

BCR32 Phosphate 0.77 0.4 0.39 0.55 0.52 2.09 2.09 32.98 32.71 1.84 1.85

BCS174/1 Slag 0.17 7.13 7.04 1.72 1.73 14.69 14.37 12.30 12.40 0.40 0.40

BCS176/2 Manganese ore 0.11 0.13 0.04 0.03 5.20 5.29 2.53 2.59 0.20 0.20 0.04 0.14

BCS276 Silica brick 0.06 0.06 0.06 0.04 0.85 0.89 95.90 96.08 0.03 0.01 0.14

BCS348 Ball clay 0.34 0.34 0.31 0.29 31.59 31.44 51.13 50.91 0.07 0.08 0.13

BCS370 Magnesite 0.06 0.02 61.8 62.48 12.3 12.38 3.01 2.96

BCS393 Limestone 0.05 0.00 0.15 0.15 0.12 0.16 0.70 0.68 0.01 0.01 0.02 0.10

BCS394 Bauxite 0.02 0.04 0.12 0.13 88.80 88.74 4.98 4.94 0.22 0.23 0.13

FER-1 Iron ore 0.01 0.01 0.28 0.25 0.50 0.54 16.92 16.84 2.44 2.45 0.62 0.51

GBW03109 Gypsum 0.018 0.011 1.02 1.04 0.016 0.071 0.27 0.24 0.036 55.63 55.17

GSS-7 Soil 0.07 0.07 0.26 0.20 29.26 29.40 32.69 32.56 0.26 0.27 0.06 0.14

MRG-1 Gabbro 0.74 0.73 13.55 13.84 8.47 8.41 39.12 39.14 0.08 0.07 0.15 0.21

NBS89 Lead-barium glass 5.70 5.85 0.03 0.04 0.18 0.17 65.15 65.12 0.23 0.23 0.03 0.03

NIST1880a Cement 0.19 0.19 1.72 1.69 5.18 5.12 20.31 20.38 0.22 0.22 3.25 3.18

CRM Type K2O (wt %) CaO (wt %) TiO2 (wt %) Cr2O3 (wt %) Mn3O4 (wt %) Fe2O3 (wt %)

Cert. Meas. Cert. Meas. Cert. Meas. Cert. Meas. Cert. Meas. Cert. Meas.

BCR32 Phosphate 0.08 51.76 51.46 0.03 0.03 0.04 0.04 0.00 0.01 0.23 0.24

BCS174/1 Slag 0.03 44.83 44.52 0.70 0.69 0.26 0.24 5.49 5.31 12.10 12.04

BCS176/2 Manganese ore 1.30 1.26 0.09 0.13 0.30 0.28 0.01 0.01 65.91 65.84 9.81 10.06

BCS276 Silica brick 0.14 0.12 1.75 1.70 0.17 0.16 0.02 0.02 0.16 0.16 0.79 0.78

BCS348 Ball clay 2.33 2.23 0.17 0.18 1.08 1.08 0.16 0.01 0.00 1.04 1.05

BCS370 Magnesite 0.03 0.02 1.54 1.59 0.13 0.11 13.40 13.53 0.12 0.12 7.23 7.18

BCS393 Limestone 0.02 0.01 55.40 56.13 0.01 0.01 0.00 0.00 0.01 0.01 0.05 0.06

BCS394 Bauxite 0.02 0.02 0.08 0.10 3.11 3.09 0.08 0.08 0.00 1.90 1.92

FER-1 Iron 0re 0.01 0.01 3.31 3.27 0.03 0.02 0.00 0.00 0.23 0.23 75.72 75.65

GBW03109 Gypsum 0.02 0.01 40.70 41.95 0.00 0.00 0.00 0.00 0.02 0.03

GSS-7 Soil 0.20 0.19 0.16 0.14 3.37 3.36 0.06 0.06 0.25 0.26 18.76 19.02

MRG-1 Gabbro 0.18 0.18 14.70 14.83 3.77 3.77 0.06 0.07 0.18 0.19 17.94 18.14

NBS89 Lead-barium glass 8.40 8.49 0.21 0.23 0.01 0.01 0.01 0.10 0.09 0.05 0.06

NIST1880a Cement 0.92 0.92 63.83 64.23 0.25 0.26 0.01 0.00 0.12 0.12 2.81 2.80

Table 2. Analytical accuracy: comparison of certified and measured values for twelve major and minor oxides in fourteen CRMs of various types

0

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Al 2

O3

(mea

sure

d w

t %

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Al2O3 (certified wt %)

y = 1.001x-0.009R2 = 1.000n = 113

0

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0 10 20 30 40

P 2O

5 (m

easu

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P2O5 (certified wt %)

y = 1.003x-0.004R2 = 1.000n = 106

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K2O

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easu

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K2O (certified wt %)

y = 1.002x-0.001R2 = 1.000n = 102

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TiO

2 (m

easu

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TiO2 (certified wt %)

y = 0.998x-0.010R2 = 0.999n = 112

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100

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Mn

3O4

(mea

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d w

t %

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Mn3O4 (certified wt %)

y = 0.994x-0.001R2 = 1.000n = 110

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Fe2O

3 (m

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Fe2O3 (certified wt %)

y = 1.011x-0.052R2 = 1.000n = 114

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TiO

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TiO2 (certified wt %)

Av abs diff (wt %)

Av rel diff (%)

No of samples (n)

Av abs diff (wt %)

Av rel diff (%)

No. of samples (n)

Na2O MgO Al2O3 SiO2 P2O5 *SO3 K2O CaO TiO2 Cr2O3 Mn3O4 Fe2O3

0.069 0.222 0.147 0.473 0.063 0.107 0.051 0.284 0.022 0.136 0.107 0.210

2.49 3.85 1.49 1.50 1.25 1.10 1.54 1.95 1.43 2.51 2.15 1.76

39 71 90 109 17 38 46 85 17 2 19 94

0.024 0.043 0.042 0.044 0.012 0.013 0.017 0.055 0.016 0.013 0.006 0.022

10.3 10.2 18.2 9.30 5.60 12.5 4.84 6.55 4.44 4.04 3.01 3.69

32 29 22 7 50 10 19 22 70 15 46 12

Table 3. Absolute and relative errors for a selection of oxides calculated from a large number (n) of CRMs. Data are presented for two concentration ranges, > 1 wt% and 0.1 – 1.0 wt%. *Data for SO3 are from a series of cement and gypsum samples specially prepared at a lower (1050 °C) fusion temperature to prevent the loss of sulfur.

Concentration

range

>1 wt%

0.1-1.0 wt%

2

4

6

3

5

7

Figures 2 - 7. Accuracy verification: comparison of certified and measured values for the WROXI standards ( ) and a large number (n) of CRMs ( ). The regression values y, x and R2 are for the CRMs only.

Precision and instrument stabilityThe precision, repeatability and reproducibility of the AxiosmAX-Minerals system are excellent, not only for short-term measurements (15 consecutive measurements, Table 4), but also for longer-term measurements (measurements carried out over a period of fourteen days).

For comparison, the counting statistical error (CSE) expressed in concentration units is also shown in Table 4.

Fifteen consecutive measurements of a single sample (fusion disk of a basalt rock GBW07105) demonstrate relative standard deviations better than 0.1-0.7 % at typical concentration levels greater than 0.2 wt% for many of the elements commonly analysed in wide-range oxide samples, e.g. Na2O, MgO, Al2O3, SiO2, P2O5, TiO2, K2O, CaO and Fe2O3.

More importantly, this level of precision is maintained for measurements carried out over a period of 14 days, illustrating the long-term stability of the system.

Compound Na2O MgO Al2O3 SiO2 P2O5 SO3

wt % wt % wt % wt % wt % wt %

Certified conc. 3.38 7.77 13.83 44.64 0.946 0.02

REPEATABILITY (15 consecutive measurements)

Mean conc. 3.36 7.69 13.96 44.47 0.991 0.019

Min. conc. 3.33 7.66 13.92 44.4 0.979 0.017

Max. conc. 3.39 7.71 13.99 44.54 0.999 0.02

RMS conc. 0.01 0.01 0.02 0.04 0.005 0.001

RMS relative (%) 0.42 0.17 0.12 0.09 0.51 4.69

REPRODUCIBILITY (14 days)

Mean conc. 3.36 7.69 13.95 44.44 0.998 0.02

Min. conc. 3.34 7.65 13.92 44.34 0.973 0.017

Max. conc. 3.39 7.72 13.97 44.54 0.999 0.024

RMS conc. 0.02 0.02 0.02 0.06 0.007 0.002

RMS relative (%) 0.44 0.23 0.11 0.13 0.72 10.18

COUNTING STATISTICAL ERROR

CSE in wt % conc. 0.01 0.015 0.019 0.035 0.005 0.001

CSE rel (%) 0.3 0.19 0.14 0.08 0.53 5

Compound K2O CaO TiO2 Cr2O3 Mn3O4 Fe2O3

wt % wt % wt % wt % wt % wt %

Certified conc. 2.32 8.81 2.37 0.02 0.182 13.4

REPEATABILITY (15 consecutive measurements)

Mean conc. 2.34 9.02 2.37 0.022 0.185 13.35

Min. conc. 2.33 9 2.35 0.02 0.182 13.32

Max. conc. 2.36 9.03 2.38 0.026 0.189 13.39

RMS conc. 0.01 0.01 0.01 0.002 0.002 0.02

RMS relative (%) 0.35 0.1 0.34 7.83 1.18 0.14

REPRODUCIBILITY (14 days)

Mean conc. 2.34 9.02 2.37 0.023 0.184 13.35

Min. conc. 2.33 9 2.35 0.02 0.181 13.31

Max. conc. 2.36 9.03 2.38 0.026 0.188 13.39

RMS conc. 0.01 0.01 0.01 0.002 0.002 0.03

RMS relative (%) 0.37 0.14 0.31 7.59 1.22 0.19

COUNTING STATISTICAL ERROR

CSE in wt % conc. 0.008 0.014 0.008 0.002 0.003 0.017

CSE rel (%) 0.34 0.16 0.34 10 1.65 0.13

Table 4. Analytical precision for WROXI fusions of GBW07105 (basalt)

Pro-Trace software and standards

The AxiosmAX-Minerals can be supplied with the unique Pro-Trace software and standards. Pro-Trace provides the highest quality trace element analysis (Sc to U) and targets a wide range of materials of geological and environmental significance, including rocks, soils, sediments, ores, minerals, mineral soils and fly ash.

What is the FP algorithm?The intensity of X-rays measured for a given concentration of an element depends on the bulk composition or matrix of the sample being analysed. For accurate quantification we need to make so-called matrix corrections to account for the differences in bulk composition that occur from sample to sample.

PANalytical’s FP or Fundamental Parameters algorithm used in the SuperQ software calculates matrix corrections from the theoretical laws governing the physics of X-rays. As such, FP models have a significant advantage over more traditional influence coefficient-based matrix corrections (e.g. theoretical alphas).

Unlike theoretical alphas calculations, the FP model calculates matrix corrections that are specific to each sample. This enables accurate analyses over very wide ranges in concentration and in very different types of sample. In addition, accurate analysis can be made outside the range of concentrations bracketed by the standards.

Conclusions Elemental analysis with XRF is already the key to the control of quality and production processes in the many industries analysing a wide range of oxide materials.The AxiosmAX-Minerals – WROXI – SuperQ (FP) system further extends the advantages of XRF as the best analytical method for oxides analysis, and is capable of measuring all elements required to control the production and manufacture of materials such as cement, gypsum, iron and manganese ores, ceramics, bricks, glass and some heavy mineral ores. It has been demonstrated that analyses are accurate and precise and the method benefits from a simple fusion sample preparation. Furthermore, the stability of the system is such that individual calibrations can be used for months. Time-consuming re-standardizations are unnecessary and the resulting data are highly consistent over time. Although the AxiosmAX-Minerals has been configured to meet industry requirements (see below), it can be upgraded easily with features such as increased power, continuous loading for extra speed of analysis, Omnian for complete standardless analysis and Pro-Trace for high-quality trace element analysis. The use of synthetic WROXI standards made from traceable compounds brings this method close to being a primary analytical method, rather than the strictly comparative method using CRMs as standards, which is commonly used in the XRF analysis of wide-range oxides.

Dust removal deviceThe AxiosmAX-Minerals is equipped with a dust collection device, to protect the instrument from dusty samples and reducing cross contamination and wear on critical components. This is particularly useful and important when pressed powder samples are used for routine analysis.

PANalytical B.V.Lelyweg 1, 7602 EA AlmeloP.O. Box 13, 7600 AA AlmeloThe NetherlandsT +31 (0) 546 534 444F +31 (0) 546 534 598 info@panalytical.comwww.panalytical.com

Regional sales officesAmericasT +1 508 647 1100 F +1 508 647 1115

Europe, Middle East, AfricaT +31 (0) 546 834 444 F +31 (0) 546 834 499

Asia PacificT +65 6741 2868 F +65 6741 2166

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AxiosmAX-Minerals

Standard configuration Optionally configured itemsStandard configuration Optionally configured items

X-ray tube Rh-anode SST-mAX with ZETA Technology

Cr-anode, other anodes on request

Generator 2.4 kW 3.0 kW, 4.0 kW

Tube filters Brass 400 µm, Al 750 µm, Al 200 µm + 1 free choice

Beam stop, brass 100, 300 µm, Be tube protection filter

Fixed collimator mask

27, 30, 35 or 37 mm Programmable mask: 3 position (27, 30, 37 mm) or 6 position (6, 10, 20, 27, 30, 37 mm)

Primary collimators 150 µm, 300 µmPrimary collimators 150 µm, 300 µm 100, 550, 700, 4000 µm (max. 3 in total)

Crystals LiF200, LiF220, Ge111, PE002, PX1

LiF420, Ge111 curved, PE002 curved, InSb (flat/curved), TLAP coated, PX4, PX5, PX6, PX7, PX8, PX10 (max. 8)

Detectors Flow, scintillation Sealed Xe (duplex with flow), Hi-Per Scint

Fixed channels Hi-Per channels, max. 2, for B to Mg

Loading Single Continuous: 30 s/sample less instrument overheadDirect: up to 10 s/sample less instrument overhead

Analysis medium VacuumAnalysis medium Vacuum He (N2) path

Dust removal device IncludedDust removal device Included

Spinner Included

Sample changer IncludedSample changer Included High-capacity changer up to 209 samples (32 mm) or 140 samples (40 mm)

Standards WROXI for 21 oxides (Na, Mg, Al, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Sr, Zr, Ba, Hf, Pb) (5 g/standard)

Software SuperQ Omnian, Pro-Trace, FP Multi, SPC, UAI, Enhanced Data Security, Type Standardization

Industry-specific modules

WROXI minerals module CEMOXI cement moduleWROXI minerals module CEMOXI cement moduleOil-Trace setup standardsADPOL and TOXEL polymer modules