A NEW UREA SENSOR-BASED ON COMBINING THE SURFACE-ACOUSTIC-WAVE DEVICEWITH UREASE EXTRACTED FROM GREEN SOYA BEAN AND ITS APPLICATION - DETERMINATION OF UREA IN HUMAN URINE

The urea sensor was prepared by combining a surface acoustic wave (SAW ) device, in which a SAW resonator operating at 61 MHz and a pair of p arallel electrodes were used in series, with urease extracted from gre en soya bean. The Michaelis constant and maximum reaction rate of the urease were estimated as 2.14 mM and 27.18 kHz min(-1), respectively, at pH 7.0 and 25.0 degrees C. Influences of pH, temperature and effect ers on the response properties of the SAW urea sensor were investigate d. Recovery of the sensor ranged from 95 to 105% and the detection lim it of urea was 1.0 mu g ml(-1) (1.7 x 10(-5) M). The proposed sensor h as been successfully applied to the rapid determination of urea in hum an urine samples. The results are consistent with the reported values and also support the clinical diagnosis.