A new peak recognition algorithm for detection of ultra-small nano-particles by single particle ICP-MS using rapid time resolved data acquisition on a sector-field mass spectrometer

The applicability of single particle inductively coupled plasma mass spectrometry (spICPMS) is currently limited to particles larger than similar to 10 nm in diameter. In this work, the size detection limit (DLs) was improved by resolving the ion bursts originating from silver or gold nanoparticles (AgNPs or AuNPs) using real time data acquisition with 0.1 ms time resolution. Such acquisition is here called the Fast Acquisition Speed Technique (FAST). The analytical capabilities of the FAST were evaluated on a sector field instrument with high ion transmission efficiency (ITE). An algorithm for distinguishing particle events from dissolved and/or background signals was developed, and it was possible to detect 6.4 nm AuNPs that delivered only 2 ions to the detector. The influence of dwell time was investigated and it was concluded that the minimum DLs is achieved for dwell times close to the duration of particle events similar to 0.2 ms. Attempts to further improve the DLs should therefore be focused on increasing the ITE of the mass spectrometer.