Fabrication of Nanoelectrospray Emitters for LC-MS
Ionization efficiency and consequently the sensitivity of mass spectrometric analyses strongly depend on the geometry of nanoelectrospray emitter used, particularly on the terminal inner diameter (ID) of the tip. Here, we provide an optimized protocol for fabrication of nanoelectrospray emitters with a tip opening of 2-3 μm in diameter, from 50 μm ID fused silica capillaries. These emitters feature a porous silicate frit to alleviate the risk of microparticulate clogging of the narrow bore tip. As a result, they maintain stable spray performance while achieving ionization efficiencies as high as 20% without the need for specialized metal or polymer coatings. The protocol document can be downloaded here as PDF, and is also available at Nature Protocol Exchange.