Since its introduction,
electrospray ionization (ESI) has become the preferred method for coupling
liquid separation techniques to mass spectrometry for the analysis of
biomolecules. Over the last fifteen
years, the thrust in proteomics (with its needs for increased sensitivity,
enhanced resolution and high throughput) has generated a tremendous amount of
interest in ESI-MS. The development
of low flow ESI (flow rates < 100 nL/min), also known as nano-ESI further
increased the utility of ESI by significantly improving sensitivity. The continuous drive to reduce flow
rates has largely been due to the characteristic advantages consistent with the
formation of smaller droplets. When
compared to ESI, the smaller droplet sizes associated with nano-ESI possess
higher surface area to volume ratios.
This in turn results in improved desolvation, enhanced ion production and
minimal ion suppression and matrix effects.
Essential to the performance of nano-ESI is
a small emitter orifice through which the fluidic sample is electrosprayed into
the MS. The emitter plays a pivotal
role in the nano-ESI process as the sensitivity, stability and reproducibility
of nano-ESI are all highly dependent on emitter characteristics. Currently, pulled-glass capillaries are
widely employed to improve electrospray performance at nL/min flow rates. While effective for stabilizing low flow
rates, pulled-tip emitters possess several technical limitations which include
susceptibility to clogging, limited range of possible flow rates, and poor tip
to tip reproducibility.
To address the limitations associated with
single aperture tapered tips, several researchers have directed efforts to the
development of multi-channel emitters. The use of multi-channel emitters has
been found to significantly improve sensitivity while extending the lifespan
(i.e. reduced clogging) of the emitter tips. In spite of this, the complex
manufacturing methods employed in the preparation of multi-channel emitters have
limited there adoption within the nano-ESI community.
Researchers at Queen’s University have
recently developed a novel multi-channel
nanoelectrospray (MCN) emitter which uses a microstructured silica fiber
as a “shower head” to split the fluidic flow thereby enhancing sensitivity and
increasing emitter robustness.
These novel emitters which are easily fabricated from commercially
available microstructured optical fibers (MSFs) possess numerous advantages when
compared to state-of-the-art tapered emitters. Importantly, accessing these advantages
does not require modification to existing mass spectrometry (MS) interfaces and
Potential Areas of
fabricated from commercially available MSFs
Increased emitter lifetimes
Status of Development:
Research samples are available for purchase.
Status of Commercialization:
PARTEQ Innovations, the technology transfer
arm of Queen’s University, has sought broad patent protection on the MCN
emitters and their methods of use.
Currently, PARTEQ Innovations is seeking industrial partners willing to
support on-going development of the process and/or are interested in licensing
the intellectual property.