As it has been previously demonstrated, borate fusion using an M4TM gas instrument, coupled with Wavelength Dispersive XRF, has the qualities needed to comply with the analytical targets described in both the ASTM C 114 and the ISO/DIS 29581-2. As the demand for electric fusion devices increases in the cement industry, it is of interest to evaluate the performance of the LeNeoTM electric fusion instrument to assess its capacity to comply with these analytical standard test methods using the same calibration strategy.
The performance evaluation of the LeNeoTM instrument and its compliance to the two international standard methods will be made by reproducing the same analytical methodology used for the evaluation of the M4 gas instrument. In parallel to this evaluation, this paper will also present the results of a new calibration strategy that allows the analysis of Chlorine (Cl) in cement materials using a borate fusion and WDXRF method.
Apparatus and instrumental conditions
A Claisse® LeNeo automatic electric instrument was used to generate all the fusion disks. Its resistance-base electric heating system, excellent insulation properties and pre-set fusion programs allowed for uniform heating conditions providing repeatable and reproducible fusion conditions and perfect retention of the volatile elements.
A Fisher Scientific Isotemp® programmable muffle furnace was used for the LOI determinations and preparation of ignited samples. The LOI method used for all the cement types and clinkers included ignition at 950°C in a clean Platinum crucible for 60 minutes.
A sequencial WDXRF spectrometer was used to collect all data. Its features and analytical conditions were as per the previous publication, except for the Chlorine calibration settings as shown in Table 1.
Table 1: Chlorine Kα calibration analytical line parameters
|kV: 40||40 Crystal: Ge||Peak Position: 92.782 °2θ|
|mA: 25||Collimator: 0.46°||Counting Time: 30 s|
|Vaccum: Yes||Detector: FPC||Background: 93.603 °2θ|
|Filter: None||Mask: 28 mm||Background Time: 30 s|
Global sample preparation method
The preparation method used for the sample before the fusion was identical to the one used for the M4 gas instrument. First, 0.6000 g ± 0.0001 g of ignited sample was weighed in a Pt/Au crucible. Then 6.0000 g ± 0.0003 g of Claisse LiT/LiM/LiBr: 49.75%/49.75%/0.5%, Pure Grade Flux was added on top of the sample. The sample and flux were mixed together in a VortexMixerTM.
The fusion temperature of LeNeo instrument was set at 1065°C for 19 minutes, and then the molten material was poured in a 32 mm diameter, 1 mm thick mold. The automatic cooling of the glass disk took 5 minutes with forced air.
Calibration strategy, selection of control sample and preparation for validation
Comparable to the evaluation of the M4 gas instrument, two sets of CRMs, one from the NIST and the other from the JCA, were used for the calibration of the cement application. Table 2 demonstrates the element concentration range as an oxide equivalent for the combination of the two sets of LOI free base. This table also illustrates the element concentration of the control sample selected to evaluate the global borate fusion/XRF method with ISO standard method.
Table 2: CRMs element concentration as an oxide equivalent and control sample
|Compound||Concentration Range||ISO Control sample|
|NIST – JCA
(LOI Free Base)
(LOI Free Base)
|SiO2 (%)||18.907 - 29.29||21.8|
|Al2O3 (%)||3.40 - 10.70||4.85|
|Fe2O3 (%)||0.154 - 4.18||0.30|
|CaO (%)||49.28 - 68.94||70.00|
|MgO (%)||0.78 - 5.12
|SO3 (%)||1.91 - 4.689
|Na2O (%)||0.021 - 1.086
|K2O (%)||0.094 - 1.248||0.11|
|Cl (%)||0.0019 - 0.0183||0.005|
Qualification for the ASTM Standard Test Method and validation of the analytical method with ISO were carried out as described in the previous paper.
Because very few commercially available cement CRMs contain a high level of Chlorine, the calibration for Chlorine had to be performed with synthetic standards. To existing cement CRMs, known concentrations of Chlorine salts were added in view to build a calibration range from 0% up to 0.567%.
Results and discussion
Robustness of the fusion method
The LeNeo instrument has proven to successfully fuse samples of cement and cement related materials (including raw materials) into glass disks, within the same range as the M4 gas instrument. In order to be successful with all raw materials, ignition of the sample prior to fusion was necessary.
Figure 1 presents the calibration curve of the corrected concentrations vs the expected concentrations that resulted from the calibration strategy that was based on the use of commercially available cement CRMs, doped with Chlorine salts. The linearity of the curve indicates an excellent retention of the Chlorine in the cement glass disks.
Figure 1. Chlorine (Cl) calibration curve made from cement CRMs with added chlorine salts.
ASTM Precision and accuracy
The ASTM precision and accuracy tests were applied as described in the method.
The precision results shown in Table 3 are the largest absolute difference of the duplicates over all the CRMs used, for all analyzed elements. The accuracy result is the maximum values of difference between the average duplicate results and the certified value over all CRMs tested.
Table 3. ASTM C 114: Results of the precision and accuracy tests
|Compound||Precision Test||Accuracy Test|
|ASTM Limit||LeNeo Fluxer||ASTM Limit||LeNeo Fluxer|
|SiO2 (%)||0.16||0.087||± 0.2||0.104|
|Al2O3 (%)||0.20||0.060||± 0.2||0.078|
|CaO (%)||0.20||0.019||± 0.3||0.150|
|MgO (%)||0.16||0.029||± 0.2||0.063|
|SO3 (%)||0.10||0.028||± 0.1||0.061|
|Na2O (%)||0.03||0.012||± 0.05
|K2O (%)||0.03||0.011||± 0.05||0.026|
ISO Precision and accuracy
The ISO precision and accuracy tests were applied as described in the method. The precision results shown in Table 4 are the largest absolute difference of the successive results of the control sample BCS-CRM 354, for all analyzed elements. The accuracy results are the maximum difference between a single replicate and the certified value.
Table 4. ISO/DIS 29581-2: Results of the precision and accuracy tests
|Compound||Precision Test (BCS-RM 354)||Accuracy Test (BCS-RM 354)|
|ISO Expert Limit||LeNeo Fluxer||ISO Expert Limit||LeNeo Fluxer|
The use of the LeNeo electric fusion instrument has proven to allow for the same fusion capabilities and analytical performance as the M4 gas instrument, which is a reference in the cement industry. The LeNeo instrument allowed to qualify for the ASTM C 114 and complied with the ISO/DIS 29581-2 standard test methods for all the elements of interest in the cement industry. Its perfect control of the fusion conditions proved to enable the retention of all the volatile elements including the chlorine for which a revolutionary calibration strategy allowed its precise and accurate analysis.
1. BOUCHARD, M., ANZELMO, J.A., RIVARD, S., SEYFARTH, A., ARIAS, L., BEHRENS, K., DURALI-MÜLLER, S., “Cement XRF application using a universal borate fusion methodology for ASTM C 114 & ISO/DIS 29581-2 qualification”.
2. ASTM, Standard C114 - 08, “Standard Test Methods for Chemical Analysis of Hydraulic Cement”, Annual Book of ASTM Standards, Volume 04.01, ASTM International, West Conshohocken, PA, 2008, pp. 150–157.
3. DIN EN ISO 29581-2 (Draft standard, 2007-07), Methods of testing cement - Chemical analysis of cement - Part 2: Analysis by X-ray fluorescence (ISO/DIS 29581-2:2007), 30 pp.
4. BOUCHARD, M., ANZELMO, J.A., RIVARD, S., SEYFARTH, A., ARIAS, L., BEHRENS, K., DURALI-MÜLLER, S., “Global cement and raw materials fusion/XRF analytical solution”, Advances in X-ray analysis, Vol. 53, Proceedings of the 58th annual conference on applications of X-ray analysis (Denver X-ray conference), International Centre for Diffraction Data, ISSN 1097-0002, 2010, pp. 263-279.