Improving detection capabilities of biogenic selenium nanoparticles in spICP-MS using an anionic ion-exchange resin†

Single particle inductively coupled plasma mass spectrometry (spICP-MS) is widely used for characterizing Se nanoparticles (SeNPs) biosynthesized by several microorganisms when exposed to Se oxyanions. However, characterization is challenging due to the high levels of dissolved ionic Se in cell culture media, particularly at short incubation times. This study demonstrates that employing an anionic ion-exchange resin (Amberlyst A-26) to remove dissolved Se species (SeO₃²⁻ and SeO₄²⁻) enhances the spICP-MS characterization of biogenic SeNPs. Extraction conditions were initially investigated (i.e., resin amount, dissolved ionic Se concentration, extraction time and matrix effects), achieving quantitative removal of ionic Se without affecting nanoparticle concentration or size distribution. The resin treatment reduced the background signal by approximately eightfold and lowered the particle size detection limit (LoD_size) from >40 nm to 20 nm. This methodology was successfully used to characterize biogenic SeNPs produced by H. mediterranei at 24 and 60 h of incubation.