Determination of urea with an ammonia gas-sensitive semiconductor device in combination with urease |
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| Authors: | F Winquist A Spetz I Lundström B Danielsson |
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| Institution: | Laboratory of Applied Physics, Linköping Institute of Technology, S-581 83 Linköping Sweden;Department of Pure and Applied Biochemistry, Chemical Centre, University of Lund, S-220 07 Lund Sweden |
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| Abstract: | An ammonia gas-sensitive Ir/Pd MOS capacitor is used for urea determinations with the aid of urease in two different systems. One combination utilizes a reaction column with immobilized urease in a flow-injection system. The lower limit of urea detection for 150-μl samples was 0.2 μM. Urea in whole blood and blood serum was determined after a 500-fold dilution, and 15 samples per hour could be assayed. The relative standard deviation was 4.6% (n=10). Recovery tests were satisfactory. Values obtained for urea in serum correlated well with those from a spectrophotometric method. The other combination is based on a small flow cell with free urease enclosed between a dialysis membrane and a gas-permeable membrane. Urea was determined in the concentration range 0.01–50 mM. The enzyme probe could be used for up to four days without changes of behaviour. |
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