DEVELOPMENT OF METHODS FO THE ANALYSIS OF COMPLEX MIXTURES BY USING TANDEM AMASS SPECTROMETRY TECHNIQUES - ION MOLECULE REACTIONS AND QUANTITATIVE LC/MS

Mass spectrometry (MS) is a powerful and versatile analytical method for the molecular-level characterization of complex mixtures. The accurate determination of ionized analytes' mass-to-charge ratios (m/z) by accurate MS measurements enables the determination of the elemental composition of each ion. Additionally, MS can be used to manipulate and separate ions according to their m/z ratios and examine their structures by using collision-activated dissociation (CAD) or ion-molecule reaction experiments. Furthermore, coupling of MS to gas chromatography (GC) or high-performance liquid chromatography (HPLC) adds another, invaluable dimension to the analysis of very complex mixtures. 

The studies discussed in this dissertation sought to improve or develop methods for the characterization of compounds in complex mixtures by using a variety of tandem mass spectrometry techniques. The ionization techniques, the mass spectrometry equipment, and certain modifications to the equipment used to conduct the studies covered in this dissertation are described in Chapter 2. Experiments used to determine the proton affinities of several saturated hydrocarbons by using gas-phase ion-molecule reactions are discussed in Chapter 3. The modification of commercial mass spectrometers for ion-molecule reaction studies is covered in Chapters 4 and 5. A new neutral reagent-introduction setup is discussed in Chapter 4. This setup was developed in order to avoid the drawback of the traditional setup to produce too many water and air adducts for ions in ion-molecule reaction experiments. To obtain high-resolution mass spectrometric information on gas-phase ion-molecule reactions, this innovative system was then combined with a quadrupole/linear quadrupole ion trap/orbitrap tribrid mass spectrometer as described in Chapter 5. Diagnostic gas-phase ion-molecule reactions between protonated vicinal diols and trimethyl orthoformate were identified using this modified tribrid mass spectrometer, as discussed in Chapter 6. Finally, Chapter 7 discusses methods developed for the detection and identification of trace amounts of chlorinated free fatty acids in waste cooking oil samples by using HPLC/high-resolution tandem mass spectrometry along with other separation techniques, such as solid-phase extraction.