This data sheet demonstrates that the Zetium spectrometer calibrated with ADPOL and TOXEL Certified Reference Materials (CRMs), is an effective solution for the elemental analysis of thermoplastics (EAT) according to ASTM D6247. Results obtained using this solution for ASTM EAT Proficiency Testing Program (PTP) of PP and LLDPE samples are discussed.
ADPOL and TOXEL CRMs
ADPOL and TOXEL CRMs are designed especially for the calibration of catalysts, additive and filler elements in thermoplastics like polyethylene and polypropylene. Malvern Panalytical developed these CRMs in collaboration with DSM Resolve; a polymer R&D laboratory with considerable experience in the development of polymer CRMs and the quantitative analysis of trace elements in plastic products.
This study was performed using the wavelength dispersive optics of the Zetium XRF spectrometer. It was configured with a 1 kW Rh anode SST R tube and is a fully integrated system with a X-Y sample handler and state-of-the-art SuperQ software, featuring an advanced Fundamental Parameters algorithm. The Zetium spectrometer is engineered for excellence in terms of both analytical accuracy, precision and operational performance.
Table 1. Measurement times
Sample preparation and measurement details
Before the measurement, all ADPOL and TOXEL discs were cleaned by rinsing with de-ionized water and dried with soft laboratory paper. An 8 minute measuring method was used. Specific element measuring times are presented in Table 1.
The accuracies of the calibrations are presented in Table 2. The calibration RMS value is a statistical comparison (1 sigma) of the certified chemical concentration of the CRMs with the concentrations calculated by regression in the calibration procedure.
Table 2. Concentration range and accuracy
The calibration plot for Ti (Figure 1), is a graphic illustration of the accuracy of the method.
Figure 1. Calibration graph for titanium
Proficiency testing results
The ASTM Proficiency Testing Programs (PTPs) are statistical quality assurance programs that enable laboratories to assess their performance in conducting test methods within their own laboratories. Their data can be compared against other laboratories that participate worldwide in the same program. In this EAT PTP, 32 laboratories participated, including laboratories from global top ten polyolefin producers.
The PTP results are presented as Z scores per element, both for the LLDPE and PP samples, Table 3. The Z score:
x - µ
is a measure of the distance in standard deviations (σ) of a measurement (x) from the mean (µ). For example, the Z score for Si in LLDPE is 0.3, which means that the result is 0.3 standard deviation higher than the mean (µ).
Table 3. Z scores of the elemental analysis results
The results clearly demonstrate that the Zetium spectrometer calibrated with ADPOL and TOXEL, is perfectly in-line with the participants of the ASTM Proficiency Test, representing important players in the polymer industry.
Typical lower limits of detection (LLDs) for elements of interest in this study are listed in Table 4. The application LLD values are those obtained for measurement times given in Table 1.
Table 4. Detection limits
The Zetium spectrometer, combined with ADPOL and TOXEL, enables the accurate analysis of important functional additive, filler and catalyst elements in thermoplastics like PE and PP. This combination performed well in the ASTM Proficiency Testing Program for Elemental Analysis in Thermoplastics according ASTM D6247.