ABSTRACT
New HPLC phases with supramolecular selectors on the basis of calixarenes and resorcinarenes were investigated for the first time by means of empirically based test mixtures. The tests, originally developed for common reversed phases, were chosen to evaluate fundamental chromatographic properties of the new materials. In the first part of these studies three descriptors (hydrophobic retention capacity--k'(hyd), hydrophobic selectivity--alpha(hyd), steric selectivity--alpha(ster)) were determined. Except of higher alpha(ster) values and alpha(hyd) values with some methods for the resorcinarene phase the phases with supramolecular selectors were classified as less hydrophobic possessing lower hydrophobic and steric selectivities compared to three RP-C18 phases and a p-tert-butyl phenyl ether phase. The results were confirmed by means of a separation of geometric isomers of thioxanthenes. In contrast, in spite of lower k'(hyd) and alpha(hyd) values calixarene phases were more selective than the Kromasil-C18 phase in the separation of gestagenic and androgenic steroids due to specific interactions with the steroids of similar lipophilicity.
Subject(s)
Chromatography, High Pressure Liquid/methods , Phenylalanine/analogs & derivatives , Phenylalanine/chemistry , Polycyclic Compounds/chemistry , CalixarenesABSTRACT
We present the results obtained from three different setups of stable, diode-laser-pumped Nd:YLF lasers that operate in the TEM00 mode at 1053 nm and are passively mode locked by a saturable Bragg reflector. We obtained pulse widths tailored between approximately 70 ps and approximately 4 ns by using intracavity etalons of various thicknesses. With a maximum output power of 680 mW, we achieved an optical efficiency of 23%.
ABSTRACT
We report on the results of proton and gamma irradiation tests performed on nonlinear crystals for second- (SHG) and third-harmonic generation. Beta-barium borate (BBO), lithium triborate (LBO), and KTP crystals were exposed to three different energies of proton radiation (8, 70, and 300 MeV) and incremental doses of gamma radiation (up to 139 krad) in order to investigate the change in SHG performance and transmission spectra. BBO and LBO crystals turned out to be a suitable choice for SHG under radiative conditions.
ABSTRACT
The chromatographic behavior of six calix[n]arene phases (n=4, 6, 8) and one calix[4]resorcinarene phase is described for the separation of cis- and trans-isomers of three thioxanthene (flupentixol, clopenthixol, chlorprothixene) and one benz[b,e]oxepin derivative (doxepin). The influences of two different organic modifiers (MeOH, MeCN) for the separation of the isomers on every column are described. Different selectivities of the stationary phases exist as a function of the ring size of the calixarenes and their substitution at the "upper rim" with p-tert.-butyl groups. Furthermore, the influence of free phenol groups on the resorcinarene phase is discussed. Relations between structural elements of the analytes and the retention behavior on the stationary phases are found. The selectivity of the calixarene and resorcinarene stationary phases is compared with a RP-C18 phase containing the same base silica. Advantages of the resorcinarene as well as of the calixarene columns exist for the separation of cis- and trans-isomers of three compounds dependent from the substitution in position 2 of the thioxanthenes, respectively the kind of the basic side chain of all substances.
