Mass spectrometry techniques for studying the reactivity of organic and biological molecules in particles

Utilizing the fundamental principles of analytical chemistry such as controlling measurement variables and developing instrumentation is essential to understanding the complexity of the atmosphere. The work in this thesis will focus on conducting controlled laboratory experiments with ozone and particulate matter as well as the development of a new mass spectrometer for organic aerosol analysis.;Angiotensin II (DRVYIHP F) and two analogs (DRVYIAP A, and DRVAIHP A) were used as model systems to study the ozonolysis of peptides containing tyrosine and histidine residues. New oxidation products, Tyr + 3O and Tyr + 34 Da, were observed as well as previously proposed products, Tyr + O, His + 3O, and Phe + O. Second order rate constants were calculated, and the relative reactivity of the isolated His residue was slightly greater than an isolated Tyr residue. Lifetimes of the peptides in the atmosphere were estimated to be on the order of 20-30 days assuming no other decomposition pathways.;A novel IT-TOF mass spectrometer with the ability to perform multiple ionization techniques such as LDI, LD-EI, and MALDI was designed and applied to the online analysis of organic aerosol. Airborne particles are first focused through an aerodynamic lens assembly and deposited onto a stainless steel collection probe inserted through a hole in the ring electrode of an ion trap. The collected sample is desorbed and ionized with a pulsed 355 or 1064 nm Nd:YAG laser beam within the ion trap cavity. Ions are collisionally cooled to the center of the trap prior to extraction into a reflectron time-of-flight mass analyzer. Parameters such as RF amplitude, laser energies, timing delays, and probe materials were investigated.;The IT-TOF mass spectrometer was applied to study the reaction of ammonium nitrate particles with trimethylamine (TMA) vapor. When exposed to a large excess of TMA, complete exchange of ammonia by TMA was observed. Lower TMA concentrations resulted in partial exchange. The reactive uptake coefficient was estimated to be 2 x 10-6, but this is likely to be a lower limit due to losses of TMA prior to introduction into the reaction system.