Electrospray sample deposition for matrix-assisted laser desorption/ionization (MALDI) and atmospheric pressure MALDI mass spectrometry with attomole detection limits

Hui Wei, Kerstin Nolkrants, David H. Powell, James H. Woods, Mei Chuan Ko, Robert T. Kennedy

Research output: Contribution to journalArticlepeer-review

53 Scopus citations

Abstract

Electrospray sample deposition was explored for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). In this method, nanoliter volumes of matrix/analyte mixture were electrosprayed from a high voltage biased (1-2 kV) fused-silica capillary onto a grounded MALDI plate mounted 100-500 μm from the capillary outlet. Electrospray deposition with these conditions produced sample spots 200-300 μm in diameter thus matching the laser spot size. Varying spray voltage and distance resulted in different crystal sizes and volatilization rates for α-cyano-4-hydroxycinnamic acid matrix. Best results were obtained when the sample was deposited as wet droplets as opposed to deposition as dried solid. Under 'wet-spray' conditions, 2-4 μm diameter crystals were formed and detection limits for several neuropeptides were 0.7-25 amol. Samples could be pre-concentrated on the plate by spraying continuously and allowing sample to evaporate in a small spot. Sample volumes as large as 580 nL were deposited yielding a detection limit of 35 pM for neurotensin 1-11. Electrospray sample deposition yielded similar results when using atmospheric pressure-MALDI coupled with a quadrupole ion trap mass spectrometer, except that the sensitivity was ∼seven-fold worse.

Original languageEnglish (US)
Pages (from-to)1193-1200
Number of pages8
JournalRapid Communications in Mass Spectrometry
Volume18
Issue number11
DOIs
StatePublished - 2004
Externally publishedYes

ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy
  • Organic Chemistry

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