In micellar liquid chromatography, interactions of the surfactants with the surface of chemically derivatized stationary phases are important. To fully understand the chemical environment of surfactant-modified stationary phases, solid state $\sp{13}$C NMR techniques, including Cross Polarization (CP), Magic Angle Spinning (MAS), and high power proton decoupling, have been used to study the interactions of three surfactants with octadecyl (C$\sb{18}),$ octyl (C$\sb8)$ and cyanopropyl (cyano) chemically derivatized silica gels. The three surfactants studied, cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB) and sodium dodecylsulfate (SDS), are commonly used in micellar reversed phase liquid chromatography (RPLC). The selectivity, retention and efficiency of these three surfactants were evaluated through the chromatographic behavior of a set of vanillin test compounds. / The motional behavior of surfactant-modified stationary phases were characterized by $\sp{13}$C NMR polarization transfer rates and relaxation mechanisms. The efficiency of polarization transfer is represented by the T$\sb{\rm CH}$ time constant, and relaxation mechanisms by the $\sp{13}$C T$\sb{1\rho}$ relaxation parameter. The T$\sb{\rm CH}$ time constant and the $\sp{13}$C T$\sb{1\rho}$ relaxation parameter were obtained for both pure and adsorbed surfactants, and for the pure cyano stationary phase. / Both the chromatographic results and the $\sp{13}$C NMR data suggest that differences in selectivity, retention and efficiency among SDS, CTAB and DTAB-modified stationary phases are due to the differing nature of each surfactant-bonded phase association. Models of SDS, CTAB and DTAB adsorbed on C$\sb{18}$ and C$\sb8$ have been proposed based on two sets of data: chromatographic selectivity, retention and efficiency; and rigidity of surfactant-modified stationary phases indicated by the T$\sb{\rm CH}$ time constants and $\sp{13}$C T$\sb{1\rho}$ relaxation parameters. The adsorption behavior of SDS, CTAB and DTAB onto the cyano phase was also analyzed by direct observation of the T$\sb{\rm CH}$ time constant and $\sp{13}$C T$\sb{1\rho}$ relaxation parameter of cyano functional group. / Source: Dissertation Abstracts International, Volume: 54-03, Section: B, page: 1371. / Major Professor: William T. Cooper. / Thesis (Ph.D.)--The Florida State University, 1993.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_76893 |
| Contributors | He, Yifang., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 135 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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