Nanoparticles for Selective Laser Desorption/Ionization in Mass Spectrometry

The selective desorption/ionization of analytes using nanomaterials is investigated using metallic nanoparticles. By replacing the sodium citrate capping of gold nanoparticles with self-assembled monolayers, we are able to both enhance analyte ionization and selectively capture analytes. Capping gold nanoparticles with a monolayer of 4-mercaptobenzoic acid enhances analyte ionization while greatly decreasing chemical noise resulting from alkali adducted species. Selective capture and sequential desorption/ionization of the peptide bradykinin (1-7) from a two peptide mixture is achieved using b-cyclodextrin capped gold nanoparticles. Finally, by switching from gold to silver nanoparticles, we are able to ionize both folic acid and amphotericin B. These results demonstrate that through careful control of nanoparticle surface chemistry and composition one can achieve selective analyte ionization for MS applications. ( JALA 2008;13:330–4)