Study of Ionization Efficiency on Silicon-Based, Micro-Fabricated Electrospray Nozzles For Micro Flow LC-ESI-MS Applications
The coupling of reduced liquid chromatography (LC) flow rates with electrospray ionization (ESI) provides enhanced sensitivity and ionization efficiency, and reduced ion suppression in mass spectrometry analysis. As the LC flow increases, the ionization efficiency drops owing to the larger sized droplets that lowers the number of available charges per analyze molecule. In order to accommodate micro-flow rates (defined as 1-10μL/min), we have developed a silicon-based ESI chip with various I.D. sizes (4.1, 5.5, 9.5, and 13.5μm).