title: Sample preconcentration in open microchannels combined with MALDI-MS.
abstract: In this work, a method for preconcentrating samples in 1 cm long, 50-150 μm wide open microchannels is presented. Platinum electrodes were positioned at the channel ends, voltage was applied, and charged analyte was preconcentrated at the oppositely charged side during continuous supply of sample. The preconcentration was initially studied in a closed system, where an influence on the analyte position from a pH gradient, generated by water electrolysis, was observed. In the open channel, the analyte distribution after preconcentration was evaluated using MALDI-MS with the channel as MALDI target. MALDI matrix was applied with an airbrush or by electrospray matrix deposition and by using the latter technique higher degrees of crystallization in the channels were obtained. After preconcentrating a 1 nM cytochrome c solution for 5 min, corresponding to a supplied amount of 1.25 fmol, a signal on the cathodic channel end could be detected. When a solution of cytochrome c trypsin digest was supplied, the peptides were preconcentrated at different positions along the channel depending on their charge.
authors.affiliation: Analytical Chemistry, Division of Applied Physical Chemistry, Department of Chemistry, School of Chemical Science and Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
authors.forename: Saara
authors.initials: S
authors.lastname: Mikkonen
authors.forename: Maria Khihon
authors.initials: MK
authors.lastname: Rokhas
authors.forename: Johan
authors.initials: J
authors.lastname: Jacksén
authors.forename: Asa
authors.initials: A
authors.lastname: Emmer
mesh_terms: D045304:Cytochromes c / Q000737:chemistry / Q000302:isolation & purification; D004566:Electrodes; D046209:Electrophoresis, Microchip / Q000295:instrumentation* / Q000379:methods; D005456:Fluorescent Dyes / Q000737:chemistry / Q000302:isolation & purification; D006863:Hydrogen-Ion Concentration; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D010984:Platinum / Q000737:chemistry; D012235:Rhodamines / Q000737:chemistry / Q000302:isolation & purification; D012825:Silicon / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D005456:Fluorescent Dyes; D010446:Peptide Fragments; D012235:Rhodamines; C009434:tetramethylrhodamine isothiocyanate; D010984:Platinum; D045304:Cytochromes c; D012825:Silicon