Glass transducers

Cyclohexapeptide monolayers on quartz microbalances are able to discriminate between different analytes in the liquid phase (see Section 10.5.1). On the basis of these results, we also have immobilized cyclopeptides (Fig. 10.14) on glass transducers. In this case, the interaction between cyclopeptides and analytes was monitored by reflectometric interference spectroscopy (RIfS) [98], RIfS is an optical detection method in which the phenomenon of reflection and interference of light at phase boundaries is used to measure changes in optical thickness (refractive index x layer thickness) of transparent films... 

Fig. 27. Abrupt contraction cell for flow visualization, birefringence and degradation measurements A inlet (from a peristaltic pump of a pressurized reservoir B outlet (atmospheric pressure or partial vacuum) C interchangeable metallic nozzle with a sapphire tip D capillary flow meter E glass window for flow visualization AP pressure drop (from pressure transducers)...

The oil-water dynamic interfacial tensions are measured by the pulsed drop (4) technique. The experimental equipment consists of a syringe pump to pump oil, with the demulsifier dissolved in it, through a capillary tip in a thermostated glass cell containing brine or water. The interfacial tension is calculated by measuring the pressure inside a small oil drop formed at the tip of the capillary. In this technique, the syringe pump is stopped at the maximum bubble pressure and the oil-water interface is allowed to expand rapidly till the oil comes out to form a small drop at the capillary tip. Because of the sudden expansion, the interface is initially at a nonequilibrium state. As it approaches equilibrium, the pressure, AP(t), inside the drop decays. The excess pressure is continuously measured by a sensitive pressure transducer. The dynamic tension at time t, is calculated from the Young-Laplace equation... 

D.J. Harrison, K. Fluri, N. Chiem, T. Tang, and Z. Fan, Micromachinng chemical and biochemical analysis and reaction systems on glass substrates. Proceedings Transducers (Stockholm, Sweden) 752— 755 (1995). 

An optical-fiber CL sensor is reported for trichlorethylene assay [87], The sensor consists of a glass fiber bundle and a transducer consisting of three components (i) a gas-permeable membrane to separate trichlorethylene from water, (ii) H2S04-NaN03 mixture as oxidizing agent, and (iii) a luminol solution. The assay of trichloroethylene can be done in the 0.05-0.6- J,g/mL concentration range with a detection limit of 0.03 J.g/mL. 

For the pure eduminum tests (99.0% minimum purity), two tests were run in initial experiments using a glass-sided water tank. Each spill was only 0.15 kg. Motion pictures indicated that most of the aluminum entered as an irregular blob. Steam bubbles formed about the metal and collapsed. No explosions were obtained. In other tests, with the steel-pipe water vessel. No. 6 blasting caps were detonated after the aluminum entered the water. (The caps were located in the center of the pipe at the same level as the pressure transducer.) The cap detonation fragmented the metal, but no explosions were obtained. 

The displacement of the center part of the cover glass is continuously monitored by a displacement transducer. The actual measurements were performed using a modified thermo-mechanical system (TMS), a Perkin Elmer TMS-2 apparatus. 

Apparatus. A conventional static vacuum apparatus was used. Reactants were introduced into cylindrical borosilicate glass reaction vessels (250-ml. capacity) suspended in a furnace maintained at a temperature within 0.1°C. Pressure measurements were made by a transducer (Consolidated Electrodynamics) linked to a recorder (RE 511 Servo-scribe). 

The design of sensitive elements (transducers) is based on the conductive principle of response registration the output signal appears to depend on the conductive properties of the TCNQ compound as a result of its interaction with gas components. The gas-sensitive substance of the transducer has been manufactured from complex TCNQ salts with N-alkylisoquinoUnium cations ([N-C H -iso-Qn] (TCNQ)Q [26]. The substance of the gas sensitive layer is put in contact with copper or silver current feeding electrodes, put on the dielectric substrate manufactured from glass-cloth laminate. 

Initially, the possibility to use the preparations of the viral Ag s commercially produced by the Leiconad company (Ukraine) and by the Kursk Pharmaceutical Plant (Russian Federation) for the RID test were tested. It was stated by the manufacturers that these preparations require additional purification to increase the concentration of the Ag markers which should be immobilized on the transducer surface. We used the antigen after the extra purification by chromatography on porous glass for our following experiments. 

New polymer membrane-based ISEs for nitrate and carbonate exhibit detection limits and selectivities that may be applicable for ocean measurements. In addition, a number of these ISEs can be used as internal transducers for the design of useful potentiometric gas sensors. For example, dissolved C02 can be detected potentiometrically by using either a glass membrane electrode or a polymer-based carbonate ISE, in conjunction with an appropriate reference electrode, behind an outer gas permeable membrane. Novel differential pC02 sensors based on two polymer membrane-type pH sensors have also been developed recently. 

Kinetic Experiments. The hydrogenation of alkene was followed by measuring the pressure as a function of time in a constant volume apparatus. The reactor was a 250 ml flask surrounded by a jacket through which thermostated water was pumped. The flask was connected to a vacuum pump, a pressure transducer, a Hg-manometer, a N2-source, and a H2 -source via a condenser. Limitation of the reaction rate because of transport restrictions from the gas phase to the liquid phase was avoided by magnetic stirring. Immediately above the reaction flask a small glass... 

When no observable changes of pressure were observed (equilibrium), the catalyst was added by rotating the glass jar. The catalyst dissolved in 10-30 sec, depending on olefin and catalyst concentrations. The pressure drop was recorded as a function of time by the pressure transducer and a recorder. The reaction rate was determined by measuring the slope of the tangent to the curve of the pressure drop at the point corresponding to the desired H2-partial pressure and the vapor pressure of the reaction mixture. The variation between two independent rate determinations at the same conditions was always less than 10% of the absolute value. 

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