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Electrospray ionization mass spectrometry from discrete nanoliter-sized sample volumes

Authors

  • Patrik Ek,

    1. Division of Analytical Chemistry, Royal Institute of Technology, SE-100 44 Stockholm, Sweden
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  • Mårten Stjernström,

    1. Division of Analytical Chemistry, Royal Institute of Technology, SE-100 44 Stockholm, Sweden
    2. Division of Laserphysics, Royal Institute of Technology, SE-106 91 Stockholm, Sweden
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  • Åsa Emmer,

    1. Division of Analytical Chemistry, Royal Institute of Technology, SE-100 44 Stockholm, Sweden
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  • Johan Roeraade

    Corresponding author
    1. Division of Analytical Chemistry, Royal Institute of Technology, SE-100 44 Stockholm, Sweden
    • Division of Analytical Chemistry, Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
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Abstract

We describe a method for nanoelectrospray ionization mass spectrometry (nESI-MS) of very small sample volumes. Nanoliter-sized sample droplets were taken up by suction into a nanoelectrospray needle from a silicon microchip prior to ESI. To avoid a rapid evaporation of the small sample volumes, all manipulation steps were performed under a cover of fluorocarbon liquid. Sample volumes down to 1.5 nL were successfully analyzed, and an absolute limit of detection of 105 attomole of insulin (chain B, oxidized) was obtained. The open access to the sample droplets on the silicon chip provides the possibility to add reagents to the sample droplets and perform chemical reactions under an extended period of time. This was demonstrated in an example where we performed a tryptic digestion of cytochrome C in a nanoliter-sized sample volume for 2.5 h, followed by monitoring the outcome of the reaction with nESI-MS. The technology was also utilized for tandem mass spectrometry (MS/MS) sequencing analysis of a 2 nL solution of angiotensin I. Copyright © 2010 John Wiley & Sons, Ltd.

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