ENZYMATIC ASSAY OF ACID-PHOSPHATASE AND MICROANALYSIS OF CU2-IMPEDANCE SENSOR( AND AG+ WITH A SAW)

Using adenosine-5'-monophosphate (5'-AMP) as a substrate, the surface acoustic wave (SAW)-impedance sensor has been successfully applied to detection of acid phosphatase and microanalysis of Cu2+ and Ag+. The a ssay of acid phosphatase is based on the change in conductance of the solution caused by enzymatic reaction between 5'-AMP and acid phosphat ase. The microanalysis of Cu2+ and Ag+ is based on its inhibitory acti on on enzyme. The Michaelis constant and the corresponding maximum ini tial rate are estimated to be 4.49 x 10(-9) mol l(-1) and 8,841 Hz min (-1), respectively at pH 4.5 and 28 degrees C. The recovery of the sen sor system ranges from 97.9-107.0% (n = 6). The experimental detection limit of enzyme is 0.7 mU ml(-1). The inhibition of Cu2+ and Ag+ is a noncompetitive one. The possible inhibition mechanism is discussed. T he kinetic parameters and inhibition parameters are estimated. The det ection limits of Cu2+ and Ag+ is 7.6 X 10(-7) M and 2.0 X 10(-8) M. So me other factors such as temperature, pH value, and active energy are also discussed. (C) 1998 Elsevier Science Inc.