Development and Applications of a Microchip Capillary Electrophoresis-High Pressure Mass Spectrometry Platform Public Deposited

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  • March 20, 2019
  • Gilliland, William
    • Affiliation: College of Arts and Sciences, Department of Chemistry
  • This work describes the pairing of electrospray ionization (ESI) with high pressure mass spectrometry (HPMS) with the goal of developing a miniature analytical platform as an alternative to traditional liquid chromatography-MS (LC-MS) systems. LC-MS systems are the standard for many chemical analyses and are used for a wide range of applications, but their size and complexity limits them to centralized labs. Microchip capillary electrophoresis (CE) coupled with HPMS presents an opportunity to provide an inexpensive, simple, and targeted separations-MS system. The work here demonstrates the initial steps for coupling ESI and HPMS, improvements for the analysis of small molecules, and strategies and applications for ESI-HPMS of intact proteins. The first step for ESI-HPMS was designing an interface to conduct ions from atmospheric pressure into the ion trap at ~1 Torr. The initial interface consisted of a capillary inlet and a simple DC “gate” lens. With this interface, the twenty common amino acids were detected when infused. Small peptides were detected with much greater sensitivity than amino acids for this interface, and microchip CE-HPMS of peptide standards was demonstrated. In addition, tandem mass spectrometry under HPMS conditions was performed with clusters of small molecules as well as with a small peptide (RGES). After initial development and proof-of-concept demonstration, several improvements were made with ESI-HPMS. An aperture was used in place of a capillary, and a tube lens was found to be more effective for small molecules than the “gate” lens. The RF drive frequency was increased to 30 MHz to improve resolution, and the trap size was decreased to critical dimensions of about 100 μm to maintain mass range. A SLIT trap was used to increase ion storage capacity. With these improvements, the twenty common amino acids were infused and detected with a 28-fold improvement in S/N and a 2.6-fold improvement in peak width over the previous HPMS analysis. Microchip CE-HPMS was then used for two applications: the analysis of amino acids in cell growth medium and the detection of opiates in urine. Finally, CE-HPMS was used for the analysis of intact proteins. A printed circuit board ion funnel was designed and implemented. The small proteins cytochrome c (12.3 kDa) and myoglobin (17 kDa) were detected. The mass range was adjusted to detect large proteins BSA (66 kDa) and an IgG2 (~150 kDa). CE-HPMS was then used for the detection of glycated hemoglobin in whole blood lysate. HPMS calculations of hemoglobin glycation in clinical samples were then correlated (R2 = 0.75) with HbA1c detection by immunoassay.
Date of publication
Resource type
Rights statement
  • In Copyright
  • Hicks, Leslie
  • Ramsey, J. Michael
  • Atkin, Joanna
  • Jorgenson, James
  • Rosen, Elias
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2017

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