title: Shape-anchored porous polymer monoliths for integrated online solid-phase extraction-microchip electrophoresis-electrospray ionization mass spectrometry.
abstract: We report a simple protocol for fabrication of shape-anchored porous polymer monoliths (PPMs) for on-chip SPE prior to online microchip electrophoresis (ME) separation and on-chip (ESI/MS). The chip design comprises a standard ME separation channel with simple cross injector and a fully integrated ESI emitter featuring coaxial sheath liquid channel. The monolith zone was prepared in situ at the injection cross by laser-initiated photopolymerization through the microchip cover layer. The use of high-power laser allowed not only maskless patterning of a precisely defined monolith zone, but also faster exposure time (here, 7 min) compared with flood exposure UV lamps. The size of the monolith pattern was defined by the diameter of the laser output (∅500 μm) and the porosity was geared toward high through-flow to allow electrokinetic actuation and thus avoid coupling to external pumps. Placing the monolith at the injection cross enabled firm anchoring based on its cross-shape so that no surface premodification with anchoring linkers was needed. In addition, sample loading and subsequent injection (elution) to the separation channel could be performed similar to standard ME setup. As a result, 15- to 23-fold enrichment factors were obtained already at loading (preconcentration) times as short as 25 s without sacrificing the throughput of ME analysis. The performance of the SPE-ME-ESI/MS chip was repeatable within 3.1% and 11.5% RSD (n = 3) in terms of migration time and peak height, respectively, and linear correlation was observed between the loading time and peak area.
authors.affiliation: Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, Finland.
authors.forename: Nina
authors.initials: N
authors.lastname: Nordman
authors.forename: Brianda
authors.initials: B
authors.lastname: Barrios-Lopez
authors.forename: Susanna
authors.initials: S
authors.lastname: Laurén
authors.forename: Pia
authors.initials: P
authors.lastname: Suvanto
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
authors.forename: Tiina
authors.initials: T
authors.lastname: Sikanen
mesh_terms: D046209:Electrophoresis, Microchip / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D057927:Hydrophobic and Hydrophilic Interactions; D004364:Pharmaceutical Preparations / Q000032:analysis / Q000302:isolation & purification; D011108:Polymers / Q000737:chemistry*; D016062:Porosity; D015203:Reproducibility of Results; D052616:Solid Phase Extraction / Q000295:instrumentation* / Q000379:methods; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation* / Q000379:methods
chemical_list: D004364:Pharmaceutical Preparations; D011108:Polymers
keywords: Electrospray ionization; Mass spectrometry; Microchip electrophoresis; Porous polymer monoliths; Solid-phase extraction