The detection of a single entity (molecule, cell, particle,
etc.)
was always a challenging subject. Here we demonstrate the detection
of single Ag nanoparticles (NPs) using subatmospheric pressure laser
desorption/ionization mass spectrometry (LDI MS). The sample preparation,
measurement conditions, generated ions, and limiting experimental
factors are discussed here. We detected from 84 to 95% of the deposited
80 nm Ag NPs. The presented LDI MS platform is an alternative to laser
ablation inductively coupled plasma mass spectrometry for imaging
distribution of individual NPs across the sample surface and has a
great potential for multiplexed mapping of low-abundance biomarkers
in tissues.