In previous Blog posts I have discussed the importance of high quality sample preparation for XRF analysis. In this post I would like to highlight a specific example of the benefit of automated high quality sample preparation for the XRF analysis of potash.
In this application example we used the Centaurus automated mill and press to prepare 10 individual samples of commercially available potash. The samples were then analyzed for their major element composition using a 600W WDXRF. The XRF was calibrated using a single point calibration with the potash sample as the calibration standard. This approach was taken to isolate the variation of the sample preparation from that of the calibration or the spectrometer. A single sample was then analyzed 10 consecutive times to establish the variation caused by the analysis and act as a baseline for comparison for the 10 individually prepared samples. The results of this we also presented at the Canadian Mineral Analysts conference in 2015.
The potash samples were prepared by milling at 500rpm for 80 seconds with a cellulose wax grinding-binding aid and then pressed at press at 15T for 30 seconds with 20 seconds of ramp and release time. The samples were pressed into steel rings and all samples had a flat and defect free surface. The mill and press were cleaned using automatic cleaning cycle between each sample.
Click on the Link to see the Centaurus Video
The 10 individually prepared samples were analyzed for K, Cl and Na. The results showed excellent reproducibility for all three elements with standard deviations that were indistinguishable from the standard deviation of the single sample analyzed 10 consecutive times. The data indicate that the automatic sample preparation did not contribute any additional error to the analysis of potash.
Automated sample preparation substantially decreases the largest source of error in XRF analysis and eliminates the need for skilled laboratory staff to spend precious time performing tedious and repetitive tasks. Automated sample preparation is now far more accessible for laboratories than in the past because it can now be offered as individual standalone cost effective components.