Zetium Ultimate edition
The worldwide production of glass today can be divided into three main types of product: borosilicate glass, soda-lime glass and lead glass. These different types of glasses have different chemical and physical properties and are produced by accurately adjusting the chemical composition by the fine balance of the different raw materials.
The composition of borosilicate glass consists mainly of silica (70 - 80 %) and boron oxide (7 - 13 %) with smaller amounts of alkalis (sodium and potassium oxides) and aluminium oxide. Relatively low alkali content results in a high chemical durability, high thermal shock resistance and a high mechanical strength. Because of these properties, borosilicate glass is widely used in the chemical industry, for laboratory apparatus, for ampoules and other pharmaceutical containers. It is also used for various high-intensity discharge lamps and as glass fibers for textiles and plastic reinforcement.
For quality control, the manufacturer is required to precisely determine the concentration of B2O3 in borosilicate glasses. Routine boron determinations in glass are commonly done by classic methods, for example, volumetric and wet-chemical procedures. These analytical techniques can be time- consuming and labor-intensive, which also make them expensive types of analysis.
By comparison, X-ray fluorescence spectrometry is a relatively simple, non-destructive and cost-effective method of analysis with simple or no sample preparation.
This application note demonstrates the capability of the Ultimate edition of the Zetium XRF spectrometer for the analysis of B2O3 in glass. The system has the precision, accuracy and repeatability required for the fast and reliable analysis of B2O3 in glass samples.
For the analysis of boron in glass, the Ultimate edition of the Zetium XRF spectrometer was used. The instrument was configured with a 4 kW generator and a Rh-anode Super Sharp Tube (SST R-mAX50) presenting a very thin beryllium window (50 μm). The tube was operated at 25 kV/160 mA in order to provide optimal excitation conditions for boron. A fixed Hi-Per channel designed with the PX7 synthetic multi-layer crystal was used to detect the boron characteristic radiation.
In addition, boron was also measured with the traditional goniometer channel, equipped with a combination of a 4000 μm primary collimator and a PX7 multi-layer crystal.
The calibration was set up using four borosilicate glass standards supplied by the Zentrum für Glas- und Umweltanalytik, Ilmenau, Germany. The certified concentrations of the standards are presented in Table 1.
Table 1. Certified concentrations of the borosilicate glass standards
Calibration and accuracy
The accuracy of B2O3 calibrations obtained with both Hi-Per and goniometer channels is presented in Table 2 and illustrated graphically in Figure 1.
The calibration RMS value is a statistical comparison (1 sigma) of the given chemical concentrations of the standards with the concentrations calculated by regression in the calibration procedure.
Table 2. Calibration quality
Figure 1. Calibration graph of B2O3 in four glass standards measured on Hi-Per and goniometer channels Note: The sensitivity obtained with a 50 μm Be window X-ray tube is ~ 15% higher than the one obtained with a 75 μm window.
The detection limit for boron in glass using the calibration parameters presented previously are given in Table 3.
The lower limit of detection (LLD) is calculated from:
The LLD values quoted are typical for the analyzed glass samples. LLD values for individual samples vary according to sample matrix and the glass composition.
Table 3. Detection limits of boron in glass, analyzed with Hi-per and goniometer channels
Precision and instrument stability
The analytical precision, repeatability and reproducibility of the Ultimate edition of the Zetium XRF spectrometer are outstanding, not only for short- term measurements (20 consecutive measurements, Table 4), but also for longer-term measurements (measurements carried out over a period of five days). For comparison, the counting statistical errors (CSE, the theoretical minimum possible error) are also shown in Table 4. Twenty consecutive measurements on a glass sample demonstrate a standard
deviation of 0.073 % relative at 16 wt%, e.g. 16.50 ± 0.01 wt % (with loading and unloading of the sample and no drift correction applied). Comparison of these precision measurements with the CSE emphasizes the inherent stability of the instrument. This stability for B2O3 is illustrated graphically in Figure 2. Measurement time used in the analysis program for the B Hi-Per channel was 300 seconds.
Table 4. Analytical precision
Figure 2. Short and longer term stability measurements of B2O3 in a glass sample on Hi-Per channel
Components typeset in bold were present in the spectrometer used to obtain the data in this note.
The results clearly demonstrate that the Ultimate edition of the Zetium XRF spectrometer is capable of analyzing boron in glass samples, even at low % levels. Measurements are accurate and precise and the method benefits from simple, essentially hazard-free, sample preparation. The stability of the Ultimate edition of the Zetium XRF spectrometer 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.
The outstanding performance of the PX7 multi-layer crystal in combination with the 4 kW SST R-mAX50 X-ray tube makes the Ultimate edition of the Zetium XRF spectrometer a unique system with an outstanding performance for boron analysis in glass.
A specific boron Hi-Per channel equipped with a PX7 synthetic multi-layer crystal will improve the sensitivity and speed of the analysis further.
The Ultimate edition of the Zetium XRF spectrometer can perform analysis of ultra-light elements (Be - O) with precision and reliability, extending the use of XRF spectroscopy to almost all samples and matrices needed.