Sensor calorimetric

The piezo-electric effect of deformations of quartz under alternating current (at a frequency in the order of 10 MHz) is used by coating the crystal with a selectively binding substance, e. g. an antibody. When exposed to the antigen, an antibody-antigen complex will be formed on the surface and shift the resonance frequency of the crystal proportionally to the mass increment which is, in turn, proportional to the antigen concentration. A similar approach is used with surface acoustic wave detectors [142] or with the surface plasmon resonance technology (BIAcore, Pharmacia). 

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Thermistor basedflow-through calorimetric sensors. Enzyme thermistors make the most widely developed type of heat measurement-based sensors. The thermistors are normally used as temperature transducers in these devices. Thermistors are resistors with a very high negative temperature coefficient of resistance. They are ceramic semiconductors made by sintering mixtures of metal (manganese, nickel, cobalt, copper, iron) oxides. Like the two previous groups, thermistor sensors do not comply strictly with the definition of "sensor" as they do not consist of transducers surrounded by an immobilized enzyme rather, they use a thermistor at the end of a small... 

Danielsson B, Mosbach K(1987) Theory and application of calorimetric sensors. In Turner A, Karube PF, Wilson IG (eds) Biosensors, Fundamentals and Applications. Oxford University Press, pp 575-595... 

Table 1. Linear concentration ranges of substances measured with calorimetric sensors using immobilized enzymes...

In this entry, we focus on the discussion of the platform technology for electrochemical sensors, metal oxide semiconductive (MOS) sensors, and piezoelectric based quartz crystal microbalance (QCM) sensors. There are other types of chemical sensors, such as optical sensors, Schottky diode based sensors, calorimetric sensors, field-effect transistor (FET) based sensors, surface acoustic wave sensors, etc. Information of these specific sensors can be found elsewhere and in current journals on sensor technologies. Because of the increasing importance of microfabricated sensors, a brief discussion of microsensors is also given. 

A practical demonstration of the usefulness of calorimetric sensors for work in different media was made in a study on immobilized a-chymotrypsin which was used for hjdrolysis of peptide bonds in 0.05 M Tris-HCl, pH 7.8, containing 10% DMF and for syntheses of pepude bonds in 50% DMF + 50% 0.1 M Na borate, pH 10.0. With the a-chymotrypsin immobilized in the enzyme thermistor column both reactions could be followed, the hydrolysis giving an exothermic response while the synthetic route was endothermic [32]. 

The major part of the volumes consists of a careful description of basic sensors in Chapters 7-13. They include liquid electrolyte sensors, solid electrolyte sensors, electronic conductivity and capacitance sensors, field effect sensors, calorimetric sensors, optochemical sensors, and mass sensitive sensors. 

Semiochemicals Sensor, calorimetric Sensor, gas Sensor, optical Separation, cafeine Separation, CO2... 

Functional polymers may be used for dihierent types of chemical sensors, including acoustic wave sensors (bulk acoustic wave, surface acoustic wave, and flexural plate wave sensors), electronic conductance sensors (semiconducting and capacitance sensors), and calorimetric sensors. ... 

Calorimetric sensors measure the asymmetry of a temperature profile round the heater, which is modulated by the fluid flow. 

In terms of the calorimetric principle, a widely used microthermoresistive flow sensor is the thermal anemometer, which typically ccmsists of a middle heater with upstream and downstream temperature sensors, relative to the flow direction [2]. Such a calorimetric sensor is based on measuring the asymmetry temperature profile around the heater, modulated by the fluid flow [1,8]. The schematic representation of a calorimetric device and the temperature distribution in the flow direction are shown in Fig. 3. The MEMS flow sensor... 

The calorimetric type of gas flow sensors analyze the temperature distribution built up in the environment around a central heater element [2]. A photograph of a novel calorimetric sensor design is shown in Fig. 1, while Fig. 2 depicts the general idea behind the concept of calorimetiic-type gas flow sensors. Figure 2 shows a single chaimel with two sensing elements, the temperature resistors, attached upstream and downstream of the direction of flow. These elements cOTifirm the direction of flow that can be in two possible directions. 

The most attractive feature of calorimetric sensors is the fact that they are based on an almost universal detection principle that is insensitive to the optical or electrochemical properties of the sample. The usefulness of calorimetry as an analytical tool in biology... 

Other metabolites that have been measured with calorimetric sensors include ascorbic acid, ATP/ADP (adenosine 5 -diphosphate), cephalosporins, galactose, hydrogen peroxide, lactose, malate, phospholipids, uric acid, xanthine, and hypoxanthine. 

The outstanding versatility of calorimetric sensors makes them useful in many other modes of operation than those described above. Some of these are briefly discussed below. 

Figure 16.23 A 2D plate detector versus 3D Calvet detector designs, (a) A 2D plate detector with thermocouples under the two pans. Only the heat flow from the bottom of the pans Is measured, (b) and (c) 3D Calvet calorimetric sensors with arrays of thermocouples totally surrounding both the sample and reference chamber. Approximately 94% of the heat flow Is captured and measured using these sensors, (d) A Calvet detector with 10 thermocouples for the sample and 10 for the reference. (Courtesy of Setaram Instrumentation, SA, Caluire, France, www.setaram.com. Used with permission.)...

For gas sensor classification, various approaches can be used. For example, taking into accoimt transduction mechanisms, we can distinguish six general categories of sensors (1) optical sensors, (2) electrochemical sensors, (3) electrical sensors, (4) mass-sensitive sensors, (5) calorimetric sensors, and (6) magnetic sensors (see Table 1.11). 

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