Potentiometric sensors properties

The design of bioeompatible (blood compatible) potentiometric ion sensors was described in this chapter. Sensing membranes fabricated by crosslinked poly(dimethylsiloxane) (silicone rubber) and sol gel-derived materials are excellent for potentiometric ion sensors. Their sensor membrane properties are comparable to conventional plasticized-PVC membranes, and their thrombogenic properties are superior to the PVC-based membranes. Specifically, membranes modified chemically by neutral carriers and anion excluders are very promising, because the toxicity is alleviated drastically. The sensor properties are still excellent in spite of the chemical bonding of neutral carriers on membranes. 

G.B. Sigal, D.G. Hafeman, J.W. Parce and H.M. Mcconnell, Electrical-properties of phospholipid-bilayer membranes measured with a light addressable potentiometric sensor, ACS Symp. Ser., 403 (1989) 46-64. J.D. Olson, P.R. Panfili, R. Armenta, M.B. Femmel, H. Merrick, J. Gumperz, M. Goltz and R.F. Zuk, A silicon sensor-based filtration immunoassay using biotin-mediated capture, J. Immunol. Methods, 134(1) (1990) 71-79. 

Chemical sensors may be classified according to the operating principle of the transducer. Based on this classification, electrochemical sensors are such chemical sensors where the chemical information is transduced into an electrical signal. Electrochemical sensors can be divided further into -> amperometric sensors, -> conduc-timetric sensors, and -> potentiometric sensors, depending on which electrical property is actually recorded. 

Reports of new materials and formulations and resin properties are prolific. Articles of a topical or applied interest include probes for in-situ hardness measurements on adhesives, photobase generators for image recording devices, oxygen inhibition in packaging applications, resins for sign boards, potentiometric sensors, new photodefinable polyimides, visible curable resists, " clay composites, putties, silica fillers, curable paints, soluble photocurable systems, fluorinated coatings and in-... 

If more than a single type of ion contributes to the measured potential in Equation 5.4, the potential can no longer be used to quantify the ions of interest. This is the interference in a potentiometric sensor. Thus, in many cases, the surface of the active electrode often incorporates a specific functional membrane which maybe ion-selective, ion-permeable, or have ion-exchange properties. These membranes tend to selectivity permit the ions of interest to diffuse or migrate through. This minimizes the ionic interference. 

Using the catalytic properties of these electrodes, it is then possible to select, for potentiometric sensors, the metal couple that most enhances the selectivity of the sensors towards certain gases. 

In view of the above features, oscillometric (conductometric) and potentiometric sensors seem to be best suited for use in industrial and environmental monitors among the electro-analytical techniques. Oscillometric and conductometric sensors fulfil the first and third requirement, the technical problems in connectin with calibration axe not too difficult. There are, however, problems with the fourth requirement, because impedance and the complex dielectric constant both depend on all constituents present, and because these properties do not only depend on one single factor but on several factors. The electrical equivalent circuit for the oscillometric capacities is given in Fig.l. The expression of the h.f. conductance, G, is as follows ... 

Polymers (and plasticizers) Lack Props for Conductivity. Furthermore, the properties of these materials (their low polarity and the resulting low dielectric constant) seem to preclude high conductivity. This may not be important for potentiometric sensors but it is crucial for voltammetric sensors. 

Electrical Properties of Phospholipid Bilayer Membranes Measured with a Light Addressable Potentiometric Sensor... 

Techniques for using a silicon-based light addressable potentiometric sensor (LAPS) to measure the electrical properties of phospholipid bilayer membranes were developed. Membrane conductance, capacitance, and potential could all be measured when the membrane was painted on an aperture between the silicon surface and a controlling electrode. The sensor was tested by observing changes in membrane properties on the addition of simple ion carriers and channels. 

He et al. [58] reported that a potentiometric sensor array in combination with principal component analysis (PCA) can classify tea samples from different geographical origins and quality types based upon the study of different sensory attributes in tea taste. A good correlation among instrumental results and tea tasters assessments was also found, which signifies that the instrument can be used to study the taste properties of teas [57]. 

PVC Application and Properties in Construction of Potentiometric Sensors for Drug Detection... 

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