Many substances in serum are criteria for many diseases . Unfortunately, a determination of clinically important substance is mainly performed by a colorimetric method An electrochemical method has advantages of being free from the influence of turbidity and coloration of a test solution and having a wide dynamic range as compared with a colorimetric method. An electrode or an enzyme-trapped electrode was severed with a dialysis membrane to prevent the adsorption of protein in a test solution

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... the electrode surface. The steady state current at a fixed potential was measured with the solution being stirred The enzyme activities in serum could be determined by measuring the increase or decrease in current due to hydrogen peroxide (using peroxidase entrapped ferrocene embedded carbon paste electrode, mPOFcCPE), NADH (using plastic formed carbon electrode, mPFCE, and mPOFcCPE in the presence of l-Methoxy-5-methylphenazinium methyl sulfate) , thiols (using glassy carbon electrode, mGCE), phenols (using mGCE) and uric acid (using mGCE) with the use of auxiliary enzymes of converting a substrate or product to the above-mentioned electro-active substances when necessary. Electro-active compounds in serum have no influence on this method, since the current due to these compounds remained constant in the course of measurement . In the determination of biochemical substances except enzyme, the current increase after the addition of enzyme or combination of enzymes that converts the object to the electro-active substance was measured In this method, an electro-active substance in serum such as uric acid did not interfere with the determination .