Nanoelectrospray emitters: Trends and perspective

Abstract

The benefits of electrospray ionization are many, including sensitivity, robustness, simplicity and the ability to couple continuous flow methods with mass spectrometry. The technique has seen further improvement by lowering flow rates to the nanoelectrospray regime (<1,000 nL/min), where sample consumption is minimized and sensitivity increases. The move to nanoelectrospray has required a shift in the design of the electrospray source which has mostly involved the emitter itself. The emitter has seen an evolution in architecture as the shape and geometry of the device have proved pivotal in the formation of sufficiently small droplets for sensitive MS detection at these flow rates. There is a clear movement toward the development of emitters that produce multiple Taylor cones. Such multielectrospray emitters have been shown to provide enhanced sensitivity and sample utilization. This article reviews the development of nanoelectrospray emitters, including factors such as geometry and the manner of applying voltage. Designs for emitters that take advantage of multielectrospray are emphasized.

Analytical Properties of Solid-substrate Electrospray Ionization Mass Spectrometry

“…Conventionally, emitters coated with or made of conductive materials or with a wire inserted have been widely used [30]. The high voltage can also be conducted via sample solutions.…”

“…The high voltage can also be conducted via sample solutions. In this way, the emitters are not necessary to be conductive [30]. For example, spray ionization has been induced from materials such as glass [31], PMMA [32], carbon fiber [33], and silica fiber [34], with high voltages applied through solution channels.…”

Top-down proteomic analysis of protein pharmaceuticals, mixtures of protein complexes, and ribosomal protein extracts by capillary zone electrophoresis-mass spectrometry

“…While the development and commercialization of ESI paved way for the analysis of biomolecules by mass spectrometry, operation of ESI at nL/min flow rates (nanoESI) greatly expanded applicability of the ESI-MS to samples of even greater complexity [39]. Initially, several experiments performed in the early 1990's demonstrated that increased sensitivity could be attained by operation of ESI at flow rates of several hundreds of nL/min [40,41].…”

“…These emitters could be used in direct infusion experiments and could also be coupled to front-end separation techniques operated at ultra-low flow rates of tens of nL/min. As a result, sensitivity was improved dramatically and extended the applicability of ESI-MS towards proteomic analyses of increasing complexity [39].…”

Nano-slit electrospray emitters fabricated by a micro- to nanofluidic via technology

“…A clear trend in on-chip integrated electrospray emitters was observed. In electrospray ionisation (ESI), reducing emitter aperture size is actively being pursued (Arscott and Troadec 2005;Mery et al 2008;Gibson et al 2009;Sikanen et al 2010), because of smaller droplets being generated. The enhanced ionisation efficiency obtained is of use to proteomics (Valaskovic et al 1995) and metabolomics.…”