Ultrasensitive Photothermal Deflection Spectrometry Using an Analyzer Etalon

The theory and experlmentat scheme for uslng an analyzer etalon to detect photothermal deflection slgnals is developed. First, a theory for photothermal deflection spectrometry Is developed, which describes the observed signal decay In terms of the characteristic thermal decay tlme constant and which accounts for a flnlte probe laser beam walst radius. Second, a theory for the angular response for an analyzer etalon Is described. The analyzer etalon Is found to be extremely sensltlve to beam angle varlatlons and dramatlcally Increases the sensltlvlty of photothermal beam deflection measurements. A theoretical enhancement over conventional deflectlon angle detectlon schemes of 100 Is calculated. Although the experlmental enhancement Is calculated to be only 0.4 of theoretlcal, a slngte laser pulse detectlon llmlt of 0.7 ppm (v/v) of CFC-12 In argon Is obtained by uslng a carbon dloxide laser operatlng at 933 cm-1 wlth a pulse energy of 1 mJ. This constitutes a slgnificant Improvement over previously determlned detection Ilmlts. Ensemble averaglng can be used to decrease this llmlt In systems where analysls tlme Is not critical. The problems encountered In uslng this detectlon scheme are also due to the extreme angle sensltlvlty. The apparatus Is very susceptible to environmental factors such as air currents, laboratory temperature varlatlons, and vlbratlons

Cyclodextrin-modified solvent extraction for polynuclear aromatic hydrocarbons

The extraction efficiencies of several polynuclear aromatic hydrocarbons (PAHs) between Isopropyl ether/water and between Isopropyl ether: 1-butanol (1:4)/water are measured in the presence of an aqueous γ-cyclodextrin (CDx) modifier at room temperature. The distribution of certain PAHs Into the aqueous phase is Increased by the presence of 10-2M γ -cdx. For compounds such as perylene and coronene, which show the most marked effects, the extraction efficiencies Into the aqueous phase from pure Isopropyl ether are 95.1% and 93.7%, respectively, when the CDx modifier Is used. In the mixed solvent system with 1-butanol, these values are 63.4% and 98.1 %, respectively. In both systems, the Increased distribution into water is based in part on the size relationship between the PAH and the CDx cavity. In the case of relatively small molecules like anthracene, little or no extraction Is observed in the presence of the CDx modifier. This type of extraction system may be useful for selective extraction of large PAHs from mixtures. Extraction results for a variety of PAHs are presented and discussed. © 1988, American Chemical Society. All rights reserved

Enantiomeric resolution and chiral recognition of racemic nicotine and nicotine analogs by .beta.-cyclodextrin complexation. Structure-enantiomeric resolution relationships in host-guest interactions

High-performance liquid chromatography using β-cyclodextrin bonded phases was examined for the enantiomeric separation of racemic nicotine and 19 racemic nicotine analogues. Ten pairs of enantiomers were separated by this technique. This represents the first reported facile and direct separation of these racemates. Effects of pH, mobile phase composition, and structural features of the substrates (i.e., position and size of substituents, presence of pyrrolidine ring or hydrogen bonding functionalities, basicity) on the enantioselectivity are examined. Various structural aspects of the compounds were related to retention to the cyclodextrln-modlfied support and to the enantiomeric separations observed. Implications of this work to host-guest complexation are discussed. © 1988, American Chemical Society. All rights reserved