DEVELOPMENT OF ROBUST AND SENSITIVE NANO-ELECTROSPRAY IONIZATION SOURCE WITH NOVEL MULTI-CHANNEL EMITTER COUPLED WITH MASS SPECTROMETRY

Abstract

Nanoelectrospray ionization (nanoESI) provides high sensitivity due to increased desolvation efficiencies developed through the production of nanometer sized droplets. Unfortunately, this sensitivity is often traded for poor robustness and reproducibility, where conventional nanospray emitters/sources are prone to both clogging and spray irreproducibility. In conventional nanoESI the use of a multi-channel emitter is of interest for generating nanoelectrospray due to its lower chance of clogging, high sample throughput and improved sensitivity. In comparison to a single-tip emitter forming a single Taylor cone, a multiple emitter forms a plume of mist. This plume is attributed to multiple Taylor cones formed from multiple channels. Sensitivity gain is related to the square root of the number of emitters. The multi-channel emitter is expected to spray a larger volume in an efficient manner and reduce the tendency to clog. However, to eliminate the dependency of sprayer plume or the Taylor cone effect, we have developed a nanoESI ion source (GenieTM). Thus, lower chances of clogging and improved sensitivity are expected to provide improvements over conventional nanoESI emitter. Genie is a novel ion source vessel that makes use of a carrier gas flow to transport ions generated in the channel of the vessel to the sampling orifice of the MS, decoupling the outlet of the sprayer from the inlet of the MS. Thus, the signal stability and reproducibility do not depend on the sprayer plume or the Taylor cone effect. Also, improvements in the desolvation process results in better ionization efficiency and reduction in background noise. Genie’s physical geometry provides the flow conditions for minimum ion neutralization. It also eliminates the need for curtain gas (reducing complexity). Overall, GenieTM is an interface that utilizes a novel laminar-flow based heated source for induced desolvation and a pneumatic flow focusing module to enhance nanoESI stability and robustness.