A microbore electrospray (ESI) injection system has been adapted to our 9.4-tesla ESI FT-ICR mass spectrometer, greatly enhancing the stability and sensitivity of the system. Spray was generated from micro-ESI needles made from sharply tapered, polished fused silica capillaries of 25 to 50 μm inner diameter. Micro-ESI permits low-level sample analysis by constant infusion at sub-μL/min flow rate over a wide range of solvent conditions in both positive- and negative-ion mode. The system is flexible and allows rapid conversion to allow routine LC/MS analysis on low-level mixtures presented in biological media. LC/MS analyses were accomplished by replacing micro-ESI needles with capillaries packed with reverse phase retention media to permit analyte concentration and purification prior to analysis (micro-ESI/LC). A unique nano-flow LC pumping system was developed, capable of producing a true unsplit solvent gradient at flow rates below 1 μL/min. The micro-ESI/LC FT-ICR system produces mass spectra from a mixture of three neuroactive peptides at a concentration of 500 amol/μL (5 fmol each total loaded) in biological salts with baseline separation, signal-to-noise ratio of >10:1 and mass resolving power >5000. These results represent a reduction in detection limit by a factor of ∼2 × 106 over the best previously published LC/FT-ICR MS data.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of the American Society for Mass Spectrometry|
|State||Published - Dec 1 1998|
ASJC Scopus subject areas
- Structural Biology