[Zurück]

S. Laschober, E. Rosenberg:
"Development and Chromatographic Characterisation of Monolithic Capillary LC Columns Based on MTMS as Precursor";
Vortrag: 3. ASAC Junganalytikerforum, Linz, Österreich; 01.06.2007 - 02.06.2007.

Monolithic capillary columns exhibiting reversed-phase characteristics were synthesised using MTMS as single precursor using the sol-gel technology. First columns based on this type of precursors have recently been reported [1].
Experimental conditions such as precursor and solvent ratios, catalyst strength and gelation temperature were investigated and optimised in previous work [2]. Pore diameters could be controlled from 0.8 to 15 µm, xerogel network diameters from 0.4 to 12 µm, respectively. Specific surface areas up to 334 m2/g were observed, however many materials possessed areas only in the low m2/g range.
Chromatographic tests based on the protocols developed by Engelhardt, Tanaka and Galushko were performed with the synthesised capillary columns. A HP 1090 system with UV-DAD was used for these tests, employing isocratic conditions for separation. The results show a uniform selectivity between hydrophobic test analytes throughout all investigated columns. Methylene selectivity values obtained from different alkylated benzene derivates are comparable to values observed for various commercial C18 modified HPLC columns. Absolute retention factors for hydrophobic compounds vary by a factor of 2 between different columns, indicating a difference in the phase ratio, usually a sign of different specific surface areas accessible for interaction with the analytes. Nitrogen adsorption measurements indicated the prevalent existence of micropores which is reflected by the elution of larger compounds such as triphenylene and o-terphenyl in the deadvolume. The inclusion of polymeric porogens into the synthesis could improve this situation, however diffusion kinetics are still limited causing poor separation efficiency. Currently the use of different porogens is under investigation. Values obtained for silanol activity were already low to moderate in comparison to commercial columns without performing any kind of deactivation reaction indicating the potential to obtain very inert stationary phases after optimisation.
[1] K. Kanamori, H. Yonezawa, K. Nakanishi, K. Hirao, H.J. Jinnai, J. Sep. Sci 27 (2004), 874.
[2] S. Laschober, E. Rosenberg, M. Sulyok, J. Chromatogr. A 1144 (2007), 55.