The development and application of GC-ESI/MS
| Autor: | Hsin-Wen Tien, 田馨文 |
|---|---|
| Rok vydání: | 2012 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 100 One disadvantage of gas chromatography connected to electrospray ionization mass spectrometry（GC-ESI/MS）is peak tailing. This phenomenon greatly affects resolution and sensitivity of the method. On the other hand, organic acid is predominantly analyzed by gas chromatography/mass spectrometry（GC/MS）. The silylation derivatives of organic acid may lead to a very low intensity molecular ion and to a large fragmentation of the derivatives followed by electron impact ionization（EI）. Furthermore, when analyzing silylation derivatives of β-agonists by using GC-EI/MS, the signal intensity of molecular ion of β-agonists is also low. Besides, the mass-to-charge ratio（m/z）of diagnostic fragment ions of some β-agonist is in the range of low mass region, resulting in interference from background noise. With the technique of LC/MS, it’s hard to separate β-agonists completely. Moreover, the main analytical problems encountered in LC/MS arise from matrix effects, and the coeluting interferences would affect the ionization efficiency of the target analyte. The first part of the present work was to modify the interface design of GC-ESI/MS. By connecting empty capillary column to the end of gas chromatography column, it reduces the tailing of fatty acid methyl esters. And the signal intensity could be enhanced by one order of magnitude. The second part of this research was analyzing organic acid with the interface of GC-ESI/MS. Because silylation derivatives of organic acid hydrolyzed easily, electrospray droplets would chemically transform them into underivatized state in the ESI condition. Then, they would be carried to mass spectrometry and detected in the form of molecular ions to achieve the goal of sensitivity enhancement, because carboxyl group is a more suitable functional group for ESI in negative ion mode. Experimental results indicated that silylation derivatives of organic acid would be hydrolyzed indeed and the molecular ions were detected. However, the efficiency of hydrolysis was not satisfied. Thus, the MH+ of the silylation derivatives in ESI was used for the following analyses. The third part of this work was analyzing β-agonists by using the developed GC-ESI/MS. The ionization efficiency of these analytes, separation performance, the detection limit and repeatability of the method were studied. The results showed that β-agonists were also detected in the form of molecular ion. When the temperature of heat capillary was set at 225 ℃, the signal intensity of these compounds would be the best. Besides, better resolution was achieved with GC-ESI/MS than that of LC/MS. The limit of detection（LOD）of this method was in the range of 1-0.1 ppb with selected reaction monitoring（SRM）. The RSDs of the peak area were ranged from 10 % to 20 %, indicating an acceptable repeatability. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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