Enzymatic Elimination of Interferences

The applicability of biosensors may be severely restricted by disturbances caused by sample constituents interfering with the binding or enzymatic conversion of the analyte, such as inhibitors or alternative 

Such interferences can be compensated by using difference measurements, which usually require a reference transducer. An elegant alternative is the use of enzymatic anti-interference systems containing enzymes in front of the sensor that catalyze the conversion of the disturbing compounds to inert products. Such systems have been developed in conjunction with analytical enzyme reactors as well as enzyme electrodes. 

The same reaction system, immobilized on porous glass, has been used by Winquist et al. (1986) in two reactors combined with an ammonia sensitive iridium metal oxide semiconductor structure in an FLA system. NH3 up to 0.2 mmol/1 could be completely removed in the glutamate dehydrogenase reactor. 

Matsumoto et al. (1988) coupled enzyme reactors for the elimination of glucose and ascorbic acid with enzyme reactors for the determination of sucrose, glucose and fructose in an FLA manifold. 

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 

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