ENZYMATIC ANALYSIS OF L-LACTATE DEHYDROGENASE (LDH) WITH A SURFACE-ACOUSTIC-WAVE IMPEDANCE SENSOR AND ITS APPLICATION IN THE DETERMINATION OF LDH ACTIVITY IN HUMAN SERUM

A new method is described for the determination of L-lactate dehydroge nase (LDH) using a surface acoustic wave impedance sensor. The assay o f this enzyme is based on the change in conductance of the solution ca used by enzymic reaction between lactate, NAD(+) and LDH, A linear rel ationship between frequency response and enzyme concentration was obta ined and the detection limit was 4.8 U ml(-1). The Michaelis constant for lactate and the corresponding maximum initial rate were 0.03 mol I -1 and 13 kHz min(-1), respectively, Influences such as temperature, p H value and interferents were also investigated, The method was succes sfully applied in the clinical assay of LDH activity in human serum, T he results compared well with the reported values and support the clin ical diagnosis.