Urea determination with amperometric electrodes

The determination of alanine aminopeptidase (AAP, EC 3.4.11.14) is of importance in the rapid diagnosis of liver and bile diseases. Common assays involve the coupling of alanine hydrazide cleavage with a chro-mogenic reaction. Kirstein (1987) proposed indicating the rate of hydrazine formation electrochemically. In contrast to an amperometric urea sensor based on this indication method (see Section 3.1.21), the pH value in the near-electrode space remains unchanged while the concentration of electrode-active hydrazine rises. The incubation period for AAP assay is lowered to half of that needed in the conventional method, the two correlating with r = 0.994. 

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