No abstract

In an alkaline rebreathing circuit, the inhalation anesthetic sevoflurane degrades into at least two products, one of them being the chiral halodiether 1,1,1,3,3-pentafluoro-2-(fluoromethoxy)-3-methoxypropane (halodiether B). Using octakis(3-O-butanoyl-2,6-di-O-n-pentyl)-y-cyclodextrin (Lipodex E) as chiral host diluted in the polysiloxane PS255, an exceptional large chiral separation factor alpha of 9.7 at 30 degrees C was found for halodiether B by capillary gas chromatography (cGC). Hence, the interaction of the single enantiomers and the racemic mixture of the halodiether B with Lipodex E was selected as a model system to study the enantioselective recognition by thickness shear mode resonators (TSMR), surface acoustic wave sensors, surface plasmon resonance (SPR), and reflectometric interference spectroscopy. Further investigations of the recognition process by using chemical sensors confirmed the preferential enrichment of the S-enantiomer resulting in 9-fold higher signals. Based on the distinction between enantioselective and nonenantioselective sorption, thermodynamic complexation constants of the single enantiomers with Lipodex E could be determined. The difference in Gibbs free energy -deltaE2,E1(deltaG) of the complexation of the enantiomers of halodiether B with pure Lipodex E was determined at 30 degrees C by TSMR and SPR to be 5.7 or 5.9 kJ/mol, respectively, agreeing well with that determined by cGC, i.e., 5.7 kJ/mol at 30 degrees C.

Hyperbranched polyesters (HBP) with different end groups (P-OH, P-COOH, P-OAc) were prepared as thin films. Their surface properties were investigated using zeta potential and contact angle measurements. The differences in surface properties between P-OH and P-COOH, on the one hand, and P-OAc, on the other hand, predicted different behavior in sensoric applications. Therefore, the vapor of the homologous series of alcohols from methanol to pentanol was exposed to the thin films. Changes in thickness were observed with reflectometric interference spectroscopy (RIfS). First investigations in a current analytical problem for the detection and discrimination of refrigerants (freons) using P-OH as sensitive layer have been shown. Polydimethylsiloxane (PDMS) and poly(ether urethane) (PUT) were used as reference sensor materials for the RIfS measurements.

In this paper the quantification of quaternary mixtures of the homologous series of the alcohols methanol to n-butanol in the gaseous phase is presented. Time-resolved reflectometric interference spectroscopy (RIfS) and surface plasmon resonance spectroscopy (SPR) are used. An array consisting of two layers of a size-selective microporous polymer (Makrolon ® ) plus the polar polymer polyetherurethan (PUT) is used for RIfS measurements. The time-dependent kinetics of sorption and desorption of the analytes is evaluated by the use of neural networks. As the time-dependent sensor signals differ significantly for each analyte, quantifications with only a single microporous layer are possible. Thus, measurements using a thinner microporous layer for the SPR set-up are also performed, showing faster sorption and desorption. Therefore, measurements can be performed much faster by using the SPR set-up.It can be shown that the quantification of the quaternary mixtures can be successfully performed using a single-sensor set-up for both methods.

The intention for using microporous polymer is the enhancement of the selectivity and the sensitivity. Microporous polymers show the possibility through the control for analyte´s mobility into the matrix to extend the sensitivity spectrum for chemo sensors. A sensitive layer with molecular sieving properties is introduced in a sensor array, enhancing the discrimination capabilities of the sensing method tremendously. The volume and the size of the analytes were correlated with the sorption of the analytes in the glassy polymer UE2010. It was found that the size selective sensitive layers of the glassy polymer can discriminate effectively analytes, which are bigger or smaller than the mean pore size. The kinetic diameter σ kin of an adsorbate molecule is the molecular scale to correlate the sorption behaviour of a molecule with the aperture dimension of molecular sieves as zeolites or e.g. microporous polymers. σ kin is widely employed to describe kinetics, permeability and the permselectivity of adsorbate molecules.