title: Integrated liquid chromatography-heated nebulizer microchip for mass spectrometry.
abstract: A new integrated microchip for liquid chromatography-mass spectrometry (LC-MS) is presented. The chip is made from bonded silicon and glass wafers with structures for a packed LC column channel, a micropillar frit, a channel for optional optical detection, and a heated vaporizer section etched in silicon and platinum heater elements on the glass cover. LC eluent is vaporized and mixed with nebulizer gas in the vaporizer section and the vapor is sprayed out from the chip. Nonpolar and polar analytes can be efficiently ionized in the gas phase by atmospheric pressure photoionization (APPI) as demonstrated with polycyclic aromatic hydrocarbons (PAHs) and selective androgen receptor modulators (SARMs). This is not achievable with present LC-MS chips, since they are based on electrospray ionization, which is not able to ionize nonpolar compounds efficiently. The preliminary quantitative performance of the new chip was evaluated in terms of limit of detection (down to 5 ng mL(-1)), linearity (r>0.999), and repeatability of signal response (RSD=2.6-4.0%) and retention time (RSD=0.3-0.5%) using APPI for ionization and PAHs as standard compounds. Determination of fluorescent compounds is demonstrated by using laser-induced fluorescence (LIF) for detection in the optical detection channel before the vaporizer section.
authors.affiliation: Division of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, FI-00014 University of Helsinki, Finland.
authors.forename: Markus
authors.initials: M
authors.lastname: Haapala
authors.forename: Ville
authors.initials: V
authors.lastname: Saarela
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Pól
authors.forename: Kai
authors.initials: K
authors.lastname: Kolari
authors.forename: Tapio
authors.initials: T
authors.lastname: Kotiaho
authors.forename: Sami
authors.initials: S
authors.lastname: Franssila
authors.forename: Risto
authors.initials: R
authors.lastname: Kostiainen
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods*; D006358:Hot Temperature; D013058:Mass Spectrometry / Q000379:methods; D046228:Microarray Analysis / Q000379:methods; D046208:Microchip Analytical Procedures / Q000379:methods*; D009330:Nebulizers and Vaporizers; D018511:Systems Integration; D053719:Tandem Mass Spectrometry / Q000379:methods*