On-chip solid-phase extraction pre-concentration/focusing substrates coupled to atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry for high sensitivity biomolecule analysis

Rapid Commun Mass Spectrom. 2009 Feb;23(4):477-86. doi: 10.1002/rcm.3890.


Atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) has proven a convenient and rapid method for ion production in the mass spectrometric (MS) analysis of biomolecules. AP-MALDI and electrospray ionization (ESI) sources are easily interchangeable in most mass spectrometers. However, AP-MALDI suffers from less-than-optimal sensitivity due to ion losses during transport from the atmosphere into the vacuum of the mass spectrometer. Here, we study the signal-to-noise ratio (S/N) gains observed when an on-chip dynamic pre-concentration/focusing approach is coupled to AP-MALDI for the MS analysis of neuropeptides and protein digests. It was found that, in comparison with conventional AP-MALDI targets, focusing targets showed (1) a sensitivity enhancement of approximately two orders of magnitude with S/N gains of 200-900 for hydrophobic substrates, and 150-400 for weak cation-exchange (WCX) substrates; (2) improved detection limits as low as 5 fmol/microL for standard peptides; (3) significantly reduced matrix background; and (4) higher inter-day reproducibility. The improved sensitivity allowed successful tandem mass spectrometric (MS/MS) sequencing of dilute solutions of a derivatized tryptic digest of a protein standard, and enabled the first reported AP-MALDI MS detection of neuropeptides from Aedes aegypti mosquito heads.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Atmospheric Pressure
  • Biopolymers / analysis*
  • Microchemistry / methods*
  • Microfluidic Analytical Techniques / methods*
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Solid Phase Extraction / methods*
  • Specimen Handling / methods
  • Spectrometry, Mass, Electrospray Ionization / methods*
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / methods*


  • Biopolymers