Monitoring the enzymatic conversion of urea to ammonium by conventional or microchip capillary electrophoresis with contactless conductivity detection

Capillary electrophoresis with contactless conductivity detection was used to directly quantify the ammonium produced in the enzymatic conversion of urea with urease. This allowed the characterization of the reaction without having to use more elaborate indirect optical methods for quantification. The maximum rate of reaction, V-max, was determined as 5.1 mmol.mL(-1) min(-1), and the Michaelis-Menten constant, K,,, was determined as 16 mM. Furthermore, the method was successfully applied to the determination of urea in clinical samples of human blood by using a conventional capillary and a microchip device. (C) 2008 Elsevier Inc. All rights reserved.