title: Chip with twin anchors for reduced ion suppression and improved mass accuracy in MALDI-TOF mass spectrometry.
abstract: A new sample target for matrix-assisted laser desorption/ionization mass spectrometry is described. The target consists of pairs of elevated hydrophilic anchor surfaces, positioned in proximity onto a microchip. The anchors are used to obtain separate preparations of sample and external standard, while both anchor surfaces are irradiated simultaneously by the laser pulse. Using a standard, based on six peptides, a 2-fold improvement in mass accuracy is observed. Also, ion suppression is significantly reduced. With a one peptide calibration standard, 22 tryptic fragments from a BSA digest are detected using the twin-anchor concept, whereas only 14 fragments are detected when the sample and standard are laser-ablated as a mixture from a conventional anchor target. A volume of approximately 30 pL of sample solution of angiotensin I is transferred to the anchor surface, under a thin layer of a perfluorocarbon, to prevent a concentration bias due to evaporation. With this arrangement, a detection limit of 1.5 amol was achieved with a signal-to-noise ratio of 22:1.
authors.affiliation: Department of Analytical Chemistry, Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Sjödahl
authors.forename: Martin
authors.initials: M
authors.lastname: Kempka
authors.forename: Karin
authors.initials: K
authors.lastname: Hermansson
authors.forename: Anders
authors.initials: A
authors.lastname: Thorsén
authors.forename: Johan
authors.initials: J
authors.lastname: Roeraade
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000032:analysis / Q000378:metabolism; D000803:Angiotensin I / Q000032:analysis; D002138:Calibration; D005466:Fluorocarbons / Q000737:chemistry; D007834:Lasers; D009622:Noise; D010446:Peptide Fragments / Q000032:analysis; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012710:Serum Albumin, Bovine / Q000032:analysis / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000295:instrumentation / Q000379:methods*; D013499:Surface Properties; D014357:Trypsin / Q000032:analysis
chemical_list: D005466:Fluorocarbons; D010446:Peptide Fragments; D012710:Serum Albumin, Bovine; D000324:Adrenocorticotropic Hormone; D000803:Angiotensin I; D014357:Trypsin