X-ray fluorescence (XRF) spectrometry has replaced the traditional wet-chemical techniques in analyzing cement and related materials. Simple sample preparation, high accuracy and precision are the main reasons for this choice. Routine measurements of raw materials, raw feed, clinker and the final cement products reinforce the importance of XRF in almost all stages of cement production. CEMOXI is a set of standards, together with an application setup for Zetium spectrometers that can be used to create fused bead reference calibrations. CEMOXI calibrations can be used directly in production control when routine samples are fused but they can also be used to certify in-house standards to be used to create pressed powder calibrations, decreasing the average cost and time of analysis.
The Zetium spectrometer with CEMOXI standards and the SuperQ software with Fundamental Parameters algorithm provide the ultimate solution in the analysis of cement related materials. This report illustrates the accuracy, precision and long-term stability of the Zetium spectrometer for this type of analysis.
A Zetium spectrometer, configured with 1 kW power, an X-Y sample handler and advanced analytical software was used to generate the data presented in this data sheet. The system is engineered for excellence in terms of analytical accuracy, precision and operational performance. The CEMOXI set comprises 9, multi-element, synthetic ‘cement’ standards. Made from traceable compounds, CEMOXI is a primary analytical solution. The standards are delivered as powders to be prepared as fused beads on-site, using the customer’s flux, dilution ratios and methodology. They are therefore suited and applicable to every cement laboratory.
Sample preparation and measurement details
The CEMOXI standards and certified reference material used in this study were prepared by fusing 0.9 g of sample with 9.0 g of flux (66 % lithium tetraborate, 34 % lithium metaborate), which were cast into 40 mm diameter fused beads. The measurement program used to obtain the data presented is depicted in Table 1. The total measurement time was just over ten minutes, however, the time can be adjusted according to the required precision.
Table 1. Total measurement time (peak + background)
|Compound||Total time (s)||Compound||Total time (s)|
Accuracy of the CEMOXI calibration was verified by measuring a suite of NIST and JCA certified reference materials as routine samples. This is illustrated in the regression plots shown in Figure 1.
Figure 1 (cont.). Comparison of certified and measured values for NIST and JCA-601 standards
Precision and instrument stability
The precision, repeatability and reproducibility of the Zetium spectrometer are excellent, not only for short-term measurements (20 consecutive measurements, Table 2), but also for longer-term measurements carried out over a period of twelve days. Results in Table 2 show that no significant difference can be observed in the short-term and long-term reproducibility performance of the system. For comparison, the counting statistical error (CSE) expressed in concentration units is also shown in Table 2. The CSE is theoretically the minimum possible error and the data demonstrates the inherent stability of the Zetium spectrometer. Furthermore, concentration values obtained in the analysis are in close agreement with the certified values of the CRM sample. Overall results illustrate the excellent precision of the Zetium spectrometer over time.
Table 2. Short- and long-term analytical precision for NIST 1889a
|REPEATABILITY (20 consecutive measurements)|
|Mean (wt %)||65.57||20.39||3.81||0.18||0.15||2.77|
|RMS (wt %)||0.03||0.03||0.01||0.004||0.001||0.01|
|RMS rel. (%)||0.05||0.16||0.3||2.29||0.72||0.32|
|REPRODUCIBILITY (measurements over 12 days)|
|Mean (wt %)||65.58||20.37||3.81||0.19||0.16||2.77|
|RMS (wt %)||0.02||0.02||0.01||0.01||0.002||0.01|
|RMS rel. (%)||0.03||0.12||0.36||3.64||1.09||0.24|
|COUNTING STATISTICAL ERROR|
|CSE mean (kcps)||0.07||0.03||0.01||0.002||0.004||0.02|
|CSE rel. (%)||0.06||0.15||0.33||0.92||0.88||0.24|
Elemental analysis with XRF is already the key to production and quality control in the cement industry. The Zetium spectrometer, configured with 1 kW power, together with CEMOXI and SuperQ further demonstrate the advantages of XRF in the cement industry. It has been demonstrated that the analyses are accurate and precise, and the long-term reproducibility is such that the analytical requirements of ASTM C114 -13 are easily met. Furthermore, the stability of the system is such that individual calibrations can be used for many months, limiting the need for time-consuming re-calibrations.