A urease biosensor for the determination of urea in solutions and blood serum is made by immobilising urease in a bovine serum albumin membrane on the surface of an ion-sensitive field-effect transistor (ISFET). The sensor gives a linear response for concentrations of urea up to 2 mM at optimum parameters of the working buffer (10 mM potassium buffer, pH 7.4 with 200 mM NaCl). The high level of proteins in the serum decreases the biosensor response, but a 25-fold serum dilution gives reliable measurements. Twenty analyses can be made without a change in the sensor output. Repeated values do not differ by more than 10%. Urea measurements with the biosensor and the chemical urease-indophenol method show a high correlation. We propose that this biosensor is suitable for the medical determination of urea in blood serum.
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页码:429 / 431
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Weatherburn, Phenol-hypochlorite reaction for determination of ammonia, Analytical Chemistry, 39, pp. 163-166, (1967)