Anti-interference layer

In biospecific electrodes the eliminating enzymes are directly integrated in the sensor in membrane-immobilized form and separated from the indicator enzyme layer by a semipermeable membrane. The first enzymatic anti-interference layer was developed to enable the electrochemical determination of catecholamines in brain tissue at a graphite... 

Fig. 95. Enzyme sequence electrode for maltose determination containing a hexokinase anti-interference layer for glucose.

Fig. 96. Function of a lactate monooxygenase membrane as anti-interference layer for lactate. The current is a measure of the permeation of lactate through the membrane.

Enzymatic anti-interference layers containing oxidases can also be used to eliminate oxygen or prevent its diffusion into the electrode-near space. This enables the polarographic determination of organic com-... 

In this paper the deposition of proteins, principally for a glucose biosensor, in two spatially well controlled ways, one photolilhog and the other electrochemical will be described, as vdll be the electrochemical deposition of a thin anti-interference layer. 

Two principle techniques for electrochemical enzyme deposition have been reported, entrapment in an electrochemically grown polymer and electrochemically aided absorption. A wide range of electrochemically grown polymers have been used. The polymer can function as both an entrapment matrix and as an anti-interference layer (7, 12-20), as a matrix for the immobilisation of the protein with an electron transfer mediator (21-23), and as an electron transfer matrix alone (24, 25), Electrochemically aided adsorption has received comparably less attention (26-30), However, in our experience (31) the latter technique results in larger responses and is more appropriate to microelectrodes. Here we will present results on the electrochemically aided adsorption of GOx and BSA, and also of urease. Furthermore to reduce the interferences at the GOx/ BSA electrode we will describe the deposition of an anti-interference layer of polypyrrole, which is grown on the electrode after the deposition of the proteins. 

The polypyrrole anti-interference layer was deposited after the deposition and... 

The above results demonstrate the use of electrochemical and photolithographic methods for the spatially controlled deposition of enzymatic and anti-interference layers in a controlled way upon the surface of miniature electrodes. Although the results concentrate upon ucose measurement, the example of urease indicates that the electrochemical method should be extendible to other enzymes and we are currently investigating this. We beUeve the measurements made using the electrodes with the thin anti-interference layer are particularly interesting and show that the modified electrodes can be used in complex matrixes such as complex yeast extract medium. 

So-called AR (anti-reflection) panel method is an historical method. In this method an AR panel attached to CDT face reduces the intensity of reflected light by the effect of light interference layer which is made on a separate glass plate (panel) by sputtering or... 

An efficient mechanism for rejection of the scattered laser-line radiation has to be incorporated. The major new development in this area is the introduction of holographic filters. These devices have the sharp cut-off characteristics of the multilayer dielectrics, but do not exhibit a harmonic structure in the transmission curve. The transmission is high (80-90%) and featureless, as opposed to the dielectrics which have numerous features in the transmission curve because of interference among the multiple layers. Two filters are sufficient to give Rayleigh-line rejection, and spectral information down to 150 cm" can be obtained. Another filter type is the Chevron unit [41] which has been shown by Nicolet, and possibly Bruker, to give Raman data down to 60 cm. Additionally, data can be obtained on both the Stokes and anti-Stokes bands [42]. 

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