title: Sample pretreatment on a microchip with an integrated electrospray emitter.
abstract: This study presents a microbead-packed PDMS microchip with an integrated electrospray emitter for sample pretreatment prior to sheathless ESI-MS. We prove the concept of analytical functions integrated onto a cm-sized area of a single bulk material. The microchip consists of two PDMS substrates replicated from SU-8 fabricated silicon wafer masters, bonded together after oxidation by corona discharge treatment. The channel within the microchip contains a grid structure that was used to trap 5 microm hypercross-linked polystyrene beads. The beads acted as a medium for sample desalting and enrichment. Electrical contact for the sheathless ESI process was achieved by coating the integrated emitter with conductive graphite powder after applying a thin layer of PDMS as glue. The coating as well as the bond of the PDMS structures showed excellent durability. A continuous spray was obtained from the microchip for over 800 h in a long-term electrospray stability experiment. Desalting and enrichment of neuropeptides from a physiological salt solution was successful by loading the sample onto the packed beads, followed by a washing and an eluting step. The results were obtained and evaluated using a TOF MS. An LOD of approximately 20 fmol (loaded onto the beads) for angiotensin II was obtained from a sample of neuropeptides dissolved in physiological salt solution.
authors.affiliation: Department of Analytical Chemistry, Uppsala University, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Lindberg
authors.forename: Andreas P
authors.initials: AP
authors.lastname: Dahlin
authors.forename: Sara K
authors.initials: SK
authors.lastname: Bergström
authors.forename: Sara
authors.initials: S
authors.lastname: Thorslund
authors.forename: Per E
authors.initials: PE
authors.lastname: Andrén
authors.forename: Fredrik
authors.initials: F
authors.lastname: Nikolajeff
authors.forename: Jonas
authors.initials: J
authors.lastname: Bergquist
mesh_terms: D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D046209:Electrophoresis, Microchip / Q000295:instrumentation*; D008863:Microspheres; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation*
chemical_list: D004129:Dimethylpolysiloxanes