title: Infrared laser ablation atmospheric pressure photoionization mass spectrometry.
abstract: In this paper we introduce laser ablation atmospheric pressure photoionization (LAAPPI), a novel atmospheric pressure ion source for mass spectrometry. In LAAPPI the analytes are ablated from water-rich solid samples or from aqueous solutions with an infrared (IR) laser running at 2.94 μm wavelength. Approximately 12 mm above the sample surface, the ablation plume is intercepted with an orthogonal hot solvent (e.g., toluene or anisole) jet, which is generated by a heated nebulizer microchip and directed toward the mass spectrometer inlet. The ablated analytes are desolvated and ionized in the gas-phase by atmospheric pressure photoionization using a 10 eV vacuum ultraviolet krypton discharge lamp. The effect of operational parameters and spray solvent on the performance of LAAPPI is studied. LAAPPI offers ~300 μm lateral resolution comparable to, e.g., matrix-assisted laser desorption ionization. In addition to polar compounds, LAAPPI efficiently ionizes neutral and nonpolar compounds. The bioanalytical application of the method is demonstrated by the direct LAAPPI analysis of rat brain tissue sections and sour orange (Citrus aurantium) leaves.
authors.affiliation: Division of Pharmaceutical Chemistry, Faculty of Pharmacy, P.O. Box 56, 00014 University of Helsinki, Finland.
authors.forename: Anu
authors.initials: A
authors.lastname: Vaikkinen
authors.forename: Bindesh
authors.initials: B
authors.lastname: Shrestha
authors.forename: Tiina J
authors.initials: TJ
authors.lastname: Kauppila
authors.forename: Akos
authors.initials: A
authors.lastname: Vertes
authors.forename: Risto
authors.initials: R
authors.lastname: Kostiainen
mesh_terms: D000818:Animals; D000840:Anisoles / Q000737:chemistry; D001274:Atmospheric Pressure; D001921:Brain / Q000378:metabolism; D002762:Cholecalciferol / Q000032:analysis; D002957:Citrus / Q000737:chemistry; D003687:Dehydroepiandrosterone / Q000032:analysis; D007834:Lasers; D013058:Mass Spectrometry / Q000295:instrumentation*; D018515:Plant Leaves / Q000737:chemistry; D051381:Rats; D014050:Toluene / Q000737:chemistry; D014700:Verapamil / Q000032:analysis; D014867:Water / Q000737:chemistry
chemical_list: D000840:Anisoles; D014867:Water; D002762:Cholecalciferol; D014050:Toluene; D003687:Dehydroepiandrosterone; C060998:anisole; D014700:Verapamil