Showing papers by "Michael J. Bogan published in 2004"

Preliminary investigation of electrodynamic charged droplet processing to couple capillary liquid chromatography with matrix-assisted laser desorption/ionization mass spectrometry.

Abstract: Charged droplet processing methodology, that utilizes electrodynamic levitation technology to control the trajectories of picoliter volume charged droplets and deliver them to a target plate at atmospheric pressure, has been developed. Termed wall-less sample preparation (WaSP), this methodology offers several features that could prove beneficial to the preparation of sample spots from separation column effluents for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis. These features include solute pre-concentration factors of 101 to 103 due to volatile solvent evaporation prior to droplet deposition onto the target plate, high spatial accuracy of the deposition position of each processed droplet (±5 μm), and the ability to prepare sample spots as small as 20 μm in diameter from a single droplet. Here a new mode of operation of this methodology is described and used as an offline post-column pre-concentrating interface between capillary liquid chromatography (capLC) and a target plate for offline MALDI-MS. Using a fraction from the capLC separation of peptides produced by the proteolytic digestion of the protein cytidine 5′-triphosphate:phosphocholine cytidylyltransferase, MALDI sample spots were prepared using the dried-droplet method, direct piezoelectric droplet dispensing, and the processing of piezo-dispensed droplets by WaSP. The sample spot morphology was investigated using light microscopy, and peptide ion abundances produced by MALDI were measured using time-of-flight (TOF) MS. The advantages of developing an online capLC/WaSP interface with MALDI-MS in the future are discussed along with some of the challenges that may be encountered in such an endeavor. Copyright © 2004 John Wiley & Sons, Ltd.

Formation of closely packed microspots and irradiation of same

Abstract: This application relates to a process for controllably placing two or more microspots on a target substrate in close proximity to one another. The microspots may then be simultaneously irradiated and the resulting ions detected by mass spectrometry, such as time of flight mass spectrometry. In one embodiment the size and spacing of the microspots on the substrate may be controlled by using an electrodynamic balance during the deposition step. The deposition procedure ensures that at least some of the microspots are spaced-apart on the substrate a distance less than the focused output of a single laser. Simultaneous irradiation of the adjacent microspots may cause desorption plumes of the microspots to interact in a gas phase, such as by ion-molecule reactions. The microspots may be configured to improve the ionization yield of the sample material in the gas phase and/or to increase the frequency of ion-molecule collisions in the gas phase. This allows for desorption of particular classes of compounds to be optimized independently of ionization. Different microspots could include different amounts or types of matrix compounds to enable simultaneously detection of compounds of varied physical and chemical properties within the same sample. One or more of the microspots may include calibrants or other additives for improving detecting accuracy or quantitation. Organized array of closely packed microspots may be created for use as standard reference materials or analyte detectors.

Method of mass spectrometric analysis from closely packed microspots by their simultaneous laser irradiation

Abstract: This application relates to a process for controllably placing two or more microspots on a target substrate in close proximity to one another. The microspots may then be simultaneously irradiated and the resulting ions detected by mass spectrometry, such as time of flight mass spectrometry. In one embodiment the size and spacing of the microspots on the substrate may be controlled by using an electrodynamic balance during the deposition step. The deposition procedure ensures that at least some of the microspots are spaced-apart on the substrate a distance less than the focused output of a single laser. Simultaneous irradiation of the adjacent microspots may cause desorption plumes of the microspots to interact in a gas phase, such as by ion-molecule reactions. The microspots may be configured to improve the ionization yield of the sample material in the gas phase and/or to increase the frequency of ion-molecule collisions in the gas phase. This allows for desorption of particular classes of compounds to be optimized independently of ionization. Different microspots could include different amounts or types of matrix compounds to enable simultaneously detection of compounds of varied physical and chemical properties within the same sample. One or more of the microspots may include calibrants or other additives for improving detecting accuracy or quantitation. Organized array of closely packed microspots may be created for use as standard reference materials or analyte detectors.