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Nonpolar Matrices for Matrix Assisted Laser Desportion Ionization – Time of Flight – Mass Spectrometry

Robins, Chad LaJuan
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1115293526

Abstract Details

2005, PhD, University of Cincinnati, Arts and Sciences : Chemistry.
Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been used extensively for the characterization of large biomolecules, synthetic polymers and small molecules. Typically, low molecular weight acidic matrices have been used in MALDI-MS for such analyses. Here, the use of low molecular weight nonpolar matrices for MALDI-MS is investigated. In particular, the analytical and physical properties of this class of matrices are studied. The effect of instrumental factors on nonpolar matrix behavior was investigated. Two different MALDI target substrates, stainless steel and poly(methylmethacrylate) (PMMA), were used. The radical molecular ion abundance of nonpolar analyte ions analyzed in the presence of various nonpolar matrices, such as anthracene and 9-cyanoanthracene, were determined as a function of the MALDI target substrate. It was found that PMMA MALDI target substrates yielded higher radical molecular ion abundances for nonpolar analyte ions than stainless steel MALDI target substrates. This difference is attributed to the absence of photoelectrons which reduce charged species in the plume. To determine whether the desorption process for nonpolar matrices is different than the desorption process for polar, acidic matrices, matrix initial ion velocities were measured in MALDI-MS. The relative initial ion velocities of the nonpolar matrices, anthracene, 9-cyanoanthracene, pyrene, and acenapthene and were investigated and compared to the relative initial ion velocities for 2,5-dihydroxybenzoic acid (DHB), sinapinic acid (SA), and all-trans retinoic acid (RTA), polar matrices. It was found that DHB has a greater relative initial ion velocity than the nonpolar matrices. It does not appear that the desorption process is different between nonpolar and polar matrices based upon these results. In addition, when using any matrix, polar or nonpolar, to analyze nonpolar polymers, the addition of a metal salt increased the relative initial ion velocity of the matrix, suggesting a different desorption mechanism in these cases. To illustrate an application of nonpolar matrices for analytical MALDI-MS, an atmospheric resid crude oil fraction was characterized. The MALDI mass spectral data for this sample was difficult to interpret when a polar matrix, 3-indole acrylic acid, was used, due to fragmentation and matrix clustering in the analyte molecular weight distribution range. The nonpolar matrices anthracene and 9-cyanoanthracene were found to be very suitable for the analysis of this sample in either linear or reflectron mode time-of-flight mass spectrometry. These matrices did not lead to fragmentation or clustering, and identification and characterization of the analyte peaks were straightforward.
Dr. Patrick Limbach (Advisor)
105 p.
Chemistry, Analytical
Matrix Assisted Laser Desorption/Ionization Mass Spectrometry; MALDI; Nonpolar Matrices; Charge-Transfer Ionization; Crude Oil; Mass Spectrometry

Recommended Citations

Citations

  • Robins, C. L. (2005). Nonpolar Matrices for Matrix Assisted Laser Desportion Ionization – Time of Flight – Mass Spectrometry [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1115293526

    APA Style (7th edition)

  • Robins, Chad. Nonpolar Matrices for Matrix Assisted Laser Desportion Ionization – Time of Flight – Mass Spectrometry. 2005. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1115293526.

    MLA Style (8th edition)

  • Robins, Chad. "Nonpolar Matrices for Matrix Assisted Laser Desportion Ionization – Time of Flight – Mass Spectrometry." Doctoral dissertation, University of Cincinnati, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1115293526

    Chicago Manual of Style (17th edition)

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© 2005, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.