Nitrogen purged TXRF for the quantification of silver and palladium

Abstract

Total reflection X-ray fluorescence (TXRF) analysis is a powerful technique for simultaneous multi-element analysis. Benefits include limits of detection in the microgram per litre range, limited sample preparation for liquid samples and low operating costs. However, the determination of elements such as silver and palladium suffers from interferences, e.g. if an X-ray tube with a molybdenum anode is used, which normally offers the lowest detection limits for most of the elements of the periodic table. Argon emits its X-ray fluorescence radiation in the same energy range as these metals and therefore hinders their detection and subsequent quantification. Since argon is abundant in the atmosphere with approx. 0.93% and is easily activated by X-rays in a TXRF instrument, this interference is always present under routine measurement conditions. We have developed a new method for the analysis of silver and palladium by TXRF. A commercially available TXRF system was modified for being operated under a nitrogen purged atmosphere by surrounding it with an airtight and water-cooled box, which still allows accessing the main hardware components, changing the sample discs or performing long term measurements without temperature drift effects. An easy removal of the box is possible for a rapid change between the nitrogen purged and the common mode under ambient atmosphere. After flushing the system with nitrogen, the signal of argon decreased significantly, allowing the determination of silver and palladium with limits of detection for silver and palladium of 6.6 μg L⁻¹ and 16.6 μg L⁻¹ respectively.