Semester

Spring

Date of Graduation

2012

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Chemistry

Committee Chair

Fred L. King.

Abstract

Mass spectrometry is a widely used analytical technique for both qualitative and quantitative analysis of physical, chemical, and biological compounds by measuring mass to charge ratio (m/z) of particles. It can supply elemental composition, molecular weight, and structure information of chemical compounds. The high sensitivity and analysis speed enable it to be an outstanding tool for chemical analysis. A Quadrupole Ion Trap Mass Spectrometry (QITMS) and a pulsed Glow Discharge Time-of-Flight Mass Spectrometry (GD-TOFMS) are employed in this study.;Internal energy distribution, P(E), of collision induced dissociation in QITMS is studied by using "thermometer molecules", whose fragmentation pathway consists of several consecutive reactions with known activation energies. A plot of P(E) versus internal energy indicates the amount of internal energy deposited to precursor ions and proportion of ions with different energy. The experiment shows that there is a limit of deposited energy to the precursor ions and multiple collision induced dissociation contributes minimally.;Although Glow Discharge Mass Spectrometry (GDMS) is best known for its utility in trace element analysis, recent work demonstrates that the technique can also provide chemical speciation information. By carefully tuning parameters such as sampling distance, temporal regime, discharge gas pressure, pulse frequency, and duty cycle, a specific desired plasma environment can be produced to generate ions used for speciation. For the iron oxides, species specific variations in ratios between Fe+ and FeOH+ signal intensities provide the ability to discriminate between FeO, Fe2O 3, and Fe3O4. Iron-oxygen cluster generation correlates with oxygen abundance in the original sample as seen in these comparisons. Three groups of metal oxides including Cobalt oxides (CoO and CO3O 4), niobium oxides (NbO, NbO2, and Nb2O5 ), and copper oxides (Cu2O, and CuO) are tested with GDMS following iron oxides experiment.;The direct analysis of bio-samples, such as amino acids and peptide, by GDMS is also explored. Three different sample preparation methods are employed to explore the role of solvents or additives. Glycerol is explored to mimic Fast Atom Bombardment (FAB) and Liquid Secondary Ion Mass Spectrometry (LSIMS) experimental condition in the first method, but no molecular ion or characteristic ions are detected. In the second method, samples are dissolved in deionized water and a sample solution droplet was deposited on the sample disk. A characteristic ion, m/z 76, from cysteine detected arising from carboxylic acid loss. In the last method, III bio-samples were dissolved in 10 mM cesium chloride solution instead of deionized water, but the expected cesium related cluster ion was not detected in the spectra. Except for the 76 peak from cysteine, there are no molecular or characteristic ions detected.

Download

Share

COinS