CPSA Digest 2003

Day 1

Vendor Session - Proteomics Technologies & Applications

Variable Flow Gradient LC-MS: Spray Mode Signal Affects and Control

Variable- and switched-flow LC-MS/MS have proven to be useful tools for proteomics analysis of complex systems. Such experiments are normally conducted under "pure" electrospray conditions at micro- and nanospray flow rates. It has been established in aerosol science, that there are many possible and distinct spray modes under such conditions. Preliminary results suggest such modes can affect the quality and character of the ion generation and subsequent MS and MS/MS spectra. An unexplored area is the impact of such modes in a variable flow gradient LC-MS system. Here we present both a continuous infusion experiment to investigate this behavior and an automated machine system for spray mode control. Some modes, particularly those known to generate larger droplets, appear to exaggerate the correlation of MS signal with mobile phase flow rate. Such undesirable mass-flow dependant sensitivity can be minimized by observation of spray mode geometry and maintaining favorable (i.e. concentration dependant) spray modes. A machine vision system has been developed to maintain desirable spray modes, and avoid those that decrease ion current, baseline stability, or both.

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