| dc.contributor.author | Cubero Herrera, Lisandra. | en_US |
| dc.date.accessioned | 2014-10-21T12:34:04Z | |
| dc.date.available | 2007 | |
| dc.date.issued | 2007 | en_US |
| dc.identifier.other | AAINR31482 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/54943 | |
| dc.description | The presence of polycyclic aromatic sulfur heterocycles (PASHs) in transportation fuels is being increasingly regulated because of their impact on the environment and refining processes. Methods for the analysis of PASHs are constantly being improved to meet the new environmental regulations requiring a reduction in the amount of sulfur. However, the successful analysis of PASHs is hindered by complex matrices, many similar compounds and low level concentrations. | en_US |
| dc.description | This thesis is an investigation of atmospheric pressure ionization (API) methods and tandem mass spectrometry (MS/MS) for improving the detection of PASHs in the presence of similar compounds that may cause interference. Several adsorbents based on reduced metals supported on different materials were also examined for the enrichment of PASHs in selected fractions to aid their future identification. | en_US |
| dc.description | For API methods conventional wisdom holds that nonlinear response and interferences are more serious with electrospray ionization than with atmospheric pressure chemical ionization (APCI). However, during the APCI analysis of PASHs from petroleum we observed serious, unexpected nonlinearity and matrix effects. To understand better the parameters that influence APCI, especially ionization mechanisms, representative polycyclic aromatic compounds (PACs) from petroleum---dibenzothiophene, pyrene, carbazole, and fluorenone---were observed under various conditions. Linear ranges and limits of detection were determined in acetonitrile and methanol using flow injection. Model compounds displayed linear regions for calibration curves at low concentrations with negative deviations from linearity at high concentrations. In the linear response region, the presence of a second analyte did not affect the response of dibenzothiophene, whereas in the nonlinear region interactions between PACs were observed. The relative ionization efficiency of the model analytes differed markedly among solvents and followed the order: toluene > acetonitrile > methanol. These results were explained considering solvation effects and limiting reagent ion concentrations. | en_US |
| dc.description | MS/MS in a triple quadrupole instrument was used to study fragmentation processes of model PASHs. Neutral losses of S, HS• and CS were found to occur from these compounds and the precise losses were structure dependent. Selected reaction monitoring experiments were also performed to confirm fragmentation patterns through the use of natural abundance ratios in MS/MS spectra. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 2007. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Chemistry, Analytical. | en_US |
| dc.title | Studies on atmospheric pressure chemical ionization and tandem mass spectrometry of sulfur-containing compounds from petroleum. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
