title: 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.
abstract: 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.
authors.affiliation: School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA.
authors.forename: Arti
authors.initials: A
authors.lastname: Navare
authors.forename: Marcela
authors.initials: M
authors.lastname: Nouzova
authors.forename: Fernando G
authors.initials: FG
authors.lastname: Noriega
authors.forename: Salvador
authors.initials: S
authors.lastname: Hernández-Martínez
authors.forename: Christoph
authors.initials: C
authors.lastname: Menzel
authors.forename: Facundo M
authors.initials: FM
authors.lastname: Fernández
mesh_terms: D001274:Atmospheric Pressure; D001704:Biopolymers / Q000032:analysis*; D008832:Microchemistry / Q000379:methods*; D046210:Microfluidic Analytical Techniques / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D052616:Solid Phase Extraction / Q000379:methods*; D013048:Specimen Handling / Q000379:methods; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D001704:Biopolymers