This data sheet demonstrates that the Polymers edition of the Zetium spectrometer equipped with a ZETA technology chromium anode SST mAX X-ray tube operated at 4 kW, is an effective solution for the analysis of titanium in polyolefins.
Titanium is an important constituent of the relatively expensive Ziegler-Natta catalyst system. Accurate determination of titanium is important for quality control and catalyst recovery.
Titanium is an important constituent of the relatively expensive Ziegler-Natta catalyst system. Accurate determination of titanium is important for quality control and catalyst recovery. This data sheet demonstrates that the Polymers edition of the Zetium spectrometer equipped with a ZETA technology chromium anode SST mAX X-ray tube operated at 4 kW, is an effective solution for the analysis of titanium in polyolefins. The ZETA technology contributes to excellent reproducibility because it eliminates the single largest source of drift in the spectrometer. The ZETA technology is unique for Malvern Panalytical and demonstrates the company’s cutting-edge technologies.
For the analysis of titanium, the wavelength dispersive optics of the Polymers edition of the Zetium XRF spectrometer were used.
The Zetium Polymers edition has been especially configured to meet the needs of the plastics and polymers industry. The spectrometer was equipped with a 75 μm Be window ZETA technology Cr-anode SST mAX tube. The X-ray tube was operated at 40 kV/100 mA in order to have optimum excitation conditions. Titanium was measured using a LiF200 crystal, 300 μm collimator and a flow detector. Due to the high sensitivity of the system the measurement time was just 10 seconds.
The Malvern Panalytical ADPOL set of standards was used to calibrate the spectrometer, Table 1. Although this set includes the elements: F, Na, Mg, Al, Si, P, S, Ca, Ti and Zn, only titanium concentrations were used to set up the calibration. The polyolefin granulate samples were hot-pressed into discs.
Table 1. Titanium concentrations in different ADPOL standards
| ADPOL standard | Ti concentration (mg/kg) |
|---|---|
| 1 | 198 |
| 2 | 107 |
| 4 | 59 |
| 3 | 11.4 |
| Blank | < 0.5 |
The accuracy of the titanium calibration is presented in Table 2. A good correlation between the certified concentrations and measured intensities is demonstrated by the low calibration RMS.
Table 2. Titanium calibration accuracy
| Element | Calibration RMS* (mg/kg) | Concentration range (mg/kg) |
|---|---|---|
| Titanium | 1.55 | 0 - 198 |
*RMS (root mean square) is an indication of the quality of the regression. More accurate calibrations have smaller RMS values.
The precision, repeatability and reproducibility of the Polymers edition of the Zetium spectrometer are outstanding, not only for short-term measurements (10 consecutive measurements) but also for long-term measurements (14 measurements carried out over 14 days, Figure 1). The SST mAX X-ray tube incorporating ZETA technology contributed largely to this performance. For comparison the counting statistical error (CSE in mg/kg) is also shown in Table 3.
Table 3. Analytical precision for titanium in polyolefins
| Precision parameters | Ti in PP (mg/kg) | Ti in HDPE (mg/kg) |
|---|---|---|
| Repeatability 10 consecutive measurements | ||
| Mean | 2.1 | 3.2 |
| RMS | 0.06 | 0.08 |
| RMS (rel. %) | 3.0 | 2.6 |
| Reproducibility (14 measurements carried out over 14 days) | ||
| Mean | 2.1 | 3.3 |
| RMS | 0.10 | 0.11 |
| RMS (rel. %) | 4.6 | 3.2 |
| Error due to counting statistics | ||
| CSE | 0.07 | 0.07 |
| CSE (rel. %) | 3.3 | 2.2 |
Figure 1. Repeatability results for titanium measurements in polyolefins
The detection limit for titanium in both PP and HDPE is given in Table 4.
Table 4. Detection limits of titanium in polyolefins
| Detection limit | Ti (mg//kg) |
|---|---|
| LLD (100 s) | 0.02 |
| LLD (10 s) | 0.15 |
The sub-mg/kg detection limits allow for fast, accurate and stable results in the analyses of titanium in polyolefins. The short measurement time prevents deterioration (heat deformation) of the relatively sensitive polyolefin material.
The results clearly demonstrate that the Polymers edition of the Zetium XRF spectrometer, operated at 4 kW and equipped with a chromium anode tube, is perfectly capable of analyzing titanium in polyolefin materials, at sub-ppm levels. Measurements are accurate and precise and the method benefits from simple, essentially hazard- free, sample preparation. The stability of the Zetium spectrometer is excellent, so that individual calibrations can be used for months. Time-consuming re-standardizations are unnecessary and the resulting data are highly consistent over time. The SST mAX X-ray tube incorporating ZETA technology contributed largely to this performance.
