Application of micro-electrospray liquid chromatography techniques to FT-ICR MS to enable high-sensitivity biological analysis.
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 microns inner diameter. Micro-ESI permits low-level sample analysis by constant infusion at sub-microL/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 microL/min. The micro-ESI/LC FT-ICR system produces mass spectra from a mixture of three neuroactive peptides at a concentration of 500 amol/microL (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 approximately 2 x 10(6) over the best previously published LC/FT-ICR MS data.
Emmett
M R
MR
Center for Interdisciplinary Magnetic Resonance, Florida State University, Tallahassee 32310, USA.
White
F M
FM
Hendrickson
C L
CL
Shi
S D
SD
Marshall
A G
AG
D004723:Endorphins / Q000032:analysis; D004744:Enkephalin, Methionine / Q000032:analysis; D005583:Fourier Analysis; D006801:Humans; D013058:Mass Spectrometry / Q000295:instrumentation*; D016211:Transforming Growth Factor alpha / Q000134:cerebrospinal fluid; D014668:Vasotocin / Q000032:analysis
D004723:Endorphins; D016211:Transforming Growth Factor alpha; D004744:Enkephalin, Methionine; C021968:beta-casomorphins; D014668:Vasotocin