Sample pretreatment on a microchip with an integrated electrospray emitter.
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.
Lindberg
Peter
P
Department of Analytical Chemistry, Uppsala University, Sweden.
Dahlin
Andreas P
AP
Bergström
Sara K
SK
Thorslund
Sara
S
Andrén
Per E
PE
Nikolajeff
Fredrik
F
Bergquist
Jonas
J
D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D046209:Electrophoresis, Microchip / Q000295:instrumentation*; D008863:Microspheres; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation*
D004129:Dimethylpolysiloxanes