<p>Mass
spectrometry (MS) is a versatile analytical tool that is especially useful for
identification of unknown compounds in mixtures when coupled with
chromatography. In MS experiments, the
analytes are ionized, separated based on their mass-to-charge (<i>m/z</i>)
ratios, and detected. The molecular weight of the analyte can often be derived
from the mass spectrum if stable molecular ions (M<sup>•+</sup>) or stable
protonated/deprotonated analyte molecules ([M+H]<sup>+</sup> or [M-H]<sup>–</sup>)
are generated. Further, MS can also be used to obtain structural information
for the ionized analytes via their fragmentation reactions. Tandem mass
spectrometry (MS<sup>n</sup>) experiments are powerful for the characterization
of unknown compounds in mixtures without the need for coupling them with
chromatography. In MS<sup>n</sup> experiments, the analytes are ionized, the
ions of interest are isolated and subjected to reactions, such as
collision-activated dissociation (CAD) or ion-molecule reactions with neutral
reagent molecules. The fragmentation pattern or the diagnostic ion-molecule
reaction product ions can be utilized to elucidate the structures of the
analytes. The fragment ions or diagnostic product ions can further be subjected
to CAD to obtain more structural information. Besides analytical purposes, MS<sup>n</sup> also provides a powerful tool for exploring
the reactivities of reaction intermediates that are elusive, such as
phenylcarbyne anions and phenylcarbene anions.</p>
<p>The
research described in this dissertation mainly focuses on the development of MS<sup>n</sup>
methods based on diagnostic gas-phase ion-molecule reactions followed by CAD
for (1) the characterization of differently substituted ureas and (2) the
differentiation of sulfonate esters from their isomeric analogs, such as
sulfite esters and sulfones. HPLC was coupled with the MS<sup>n</sup> methods
discussed above to demonstrate its usefulness in the identification of
compounds in mixtures. Additionally, a gas-phase reactivity study on
phenylcarbyne anions is discussed in this dissertation. The phenylcarbyne
anions were generated by CAD of two nitrogen molecules from negatively charged
phenyl tetrazole precursors. Their reactivities towards various reagents were
explored and rationalized with the help of quantum chemical calculations.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/19111388 |
| Date | 18 April 2022 |
| Creators | Erlu Feng (12035771) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/MASS_SPECTROMETRIC_METHODS_DEVELOPMENT_FOR_IDENTIFICATION_OF_DRUG_HERBICIDE_SUBSTANCES_AND_MUTAGENIC_IMPURITIES_AND_GAS-PHASE_REACTIVITY_STUDY_OF_PHENYLCARBYNE_ANIONS/19111388 |
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