Infrared (4000È50 cm~1) spectra of the vapor, the amorphous and crystalline solid phase, and Raman spectra (4000È50 cm~1) of the vapor, liquid and crystalline solid phases of dimethyl carbonate have been recorded, and assignments are proposed. MP2 and DFT ab initio calculations were carried out using a 6-31G** basis set. The calculations show that the compound can occur as the cisÈcis, cisÈtrans and near-transÈnear-trans conformers, with the cisÈcis being the global minimum. Vibrational frequencies and solvation free enthalpies were predicted on the DFT level of theory. Both cisÈcis and cisÈtrans conformers were identiÐed in the vibrational spectra of all Ñuid phases. The enthalpy di †erence between them was determined to be 8.0(4) kJ mol~1 in the pure liquid phase and 13.6(9) kJ mol~1 in the vapor phase.

Capillary electrophoresis was coupled successfully and reliably to potentiometric sensors, which are based on an ionically conductive rubber phase coating, applied on a 250 microm diameter metal substrate. The membrane components included potassium tetrakis(p-chlorophenyl)borate (TCPB), bis(2-ethylhexyl)sebacate (DOS), and high molecular mass poly(vinyl chloride) (PVC). Potentiometry reveals a very sensitive CE detection mode, with sub-micromolar detection limits for amines and the randomly chosen drugs quinine, clozapine, cocaine, heroine, noscapine, papaverine, and ritodrine. The lowest detection limit, 1 x 10(-8) M injected concentration, was obtained for the quaternary ammonium compound tetrahexylammonium chloride. The more polar lower aliphatic amines and the biogenic amines dopamine, adrenaline, and cadaverine have much higher detection limits. The detection limits are log P dependent. Addition of a commercially available calixarene molecule or a synthetic macrocyclic amphiphilic receptor molecule to the electrode coatings enhanced the sensitivity respectively for the lower aliphatic amines and for the biogenic amines. A transpose of the Nikolskii-Eisenman-type function was suggested and used to convert the signal of the detector to a concentration-dependent signal.

ABSTRACT:We report here on a new potentiometric biosensing principle for the detection of antibody−antigen interactions at the sensing membrane surface without the need to add a label or a reporter ion to the sample solution. This is accomplished by establishing a steady-state outward flux of a marker ion from the membrane into the contacting solution. The immunobinding event at the sensing surface retards the marker ion, which results in its accumulation at the membrane surface and hence in a potential response. The ion-selective membranes were surface-modified with an antibody against respiratory syncytial virus using click chemistry between biotin molecules functionalized with a triple bond and an azide group on the modified poly (vinyl chloride) group of the membrane. The bioassay sensor was then built up with streptavidin and subsequent biotinylated antibody. A quaternary ammonium ion served as the marker ion. The observed potential was found to be modulated by the presence of respiratory syncytial virus bound on the membrane surface. The sensing architecture was confirmed with quartz crystal microbalance studies, and stir effects confirmed the kinetic nature of the marker release from the membrane. The sensitivity of the model sensor was compared to that of a commercially available point-of-care test, with promising results.O

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