Zetium Polymers edition
Polyvinyl chloride or PVC is a very widely used polymer. It is found in vehicles, toys, electronics, packaging and is also used in building and construction. The versatility of PVC depends largely on a wide variety of special additives used to influence its properties, such as heat and UV resistance, color, and its mechanical characteristics for molding. Cadmium and lead compounds have been used extensively as heat stabilizers in PVC, although the use of cadmium is decreasing as industry establishes more environmentally friendly alternatives.
In Europe, environmental concern about the use of cadmium, lead and other heavy elements has resulted in a directive on the Restriction of Hazardous Substances (RoHS). This regulation limits the permissible levels of these elements in a wide range of goods, many comprising plastics and polymers.
This data sheet demonstrates the performance of Zetium Polymers edition for the analysis of cadmium and lead in PVC.
The Zetium Polymers edition is a fully integrated wavelength dispersive XRF analyzer, consisting of a spectrometer, X-Y sample handler and software.
The Zetium Polymers edition has been especially configured to meet the needs of the plastics and polymers industry. Designed to provide accuracy, precision and sub-ppm detection limits for many elements, the Zetium Polymers edition with the unique SuperQ software provides high-quality data in both production control and R&D environments.
Standards and sample preparation
The standards used to calibrate this application were obtained from Fluxana. The composition of these standards is shown in Table 1.
Table 1. Composition of the standards used for calibration
These standards were prepared as hot-pressed discs with a diameter of 40 mm and a thickness of ~2 mm.
The SuperQ software for Zetium Polymers edition contains an application template for this PVC application and setup only requires the measurement of appropriate standards. The measurement times used to obtain the data presented in this data sheet are given in Table 2.
Table 2. Total measurement time (peak + backgrounds)
Precision and instrument stability
The precision, repeatability and reproducibility of the Zetium Polymers edition system are excellent, not only for short-term measurements (15 consecutive measurements, Table 3), but also for longer periods (8 measurements carried out over a period of 10 days). For comparison the counting statistical error (CSE in ppm) is also shown in Table 3.
Table 3. Analytical precision
The accuracy of the calibrations is presented in Table 4. The calibration RMS values are a statistical comparison (1 sigma) of the certified chemical concentrations of the standards with the concentration calculated by regression in the calibration procedure.
Table 4. Calibration quality and accuracy
Detection limits typical for the elements of interest in polymer matrices are given in Table 5.
The lower limit of detection (LLD) is calculated from:
Table 5. Detection limits
The results clearly demonstrate that the Zetium Polymers edition spectrometer can analyze heavy elements in PVC samples down to sub-ppm levels.
The stability of the Zetium Polymers edition is such that individual calibrations can be used for many months. Time-consuming re-standardizations are unnecessary and the resulting data are highly consistent over time.