Sample Introduction to the ESI Chip

Formation of a stable nanoelectrospray is dependent on many variables including the fluid surface tension, solvent composition, conductivity of the fluid and the applied voltage and pressure. Flow rate flowing through a nozzle is dependent on these variables as well as the inner diameter of the nozzle. As an example, a nozzle with a 5.5 pm inner diameter and 28 pm outer diameter will spray a solution of 50% methanol with 0.1% acetic acid at a flow rate of lOOnLmin 1 with an applied voltage of 1.4kV and pressure and 0.2 psi. A nozzle with a 2.5 pm inner diameter and 28 pm outer diameter will spray this same solution at a flow rate of 20nLmin 1 with an applied voltage of 1.2 kV and pressure of 0.3 psi. 

Lipids analysis has benefited from nanoESI with the ESI Chip.24 27 Lipids isolated from cells using liquid-liquid extraction can be quantified and separated using MS-MS scans such as multiple precursor and neutral loss scanning to identify head groups and side chain information.26 

Small-molecule quantification by automated infusion using the ESI Chip has been demonstrated to be able to provide comparable precision, accuracy and linear dynamic range compared to traditional LC-MS-MS.28 32 A linear dynamic range greater than five orders of magnitude was demonstrated which enabled validation of bioanalytical assays without the carryover limitations of LC-MS.32 

The benefits of nanoESI using the ESI Chip were recently extended to micro and analytical HPLC with the release of the TriVersa NanoMate system (Advion BioSystems) incorporating a post-column splitter that delivers 50 to 400 nL 

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