An investigation of interaction between DDVP and BuChE and the related analytical application using QCM

Polyvinyl pyrrolindone (PVP) and PVP with butyl cholinesterase (BuChE) were deposited respectively on quartz crystal microbalance (QCM) in order to investigate the adsorptive sensitivity of o,o-dimethyl-o-2, 2-dichlorvinyl phosphate (DDVP). It shows that the adsorption of DDVP on the surface of BuChE belongs to monomolecular layer and is much more sensitive than on the surface of PVP. The maximum coverage on the electrode surface is about 5.304×I0^-10 mol/cm². This area is corresponding to active sites of BuChE. It is calculated that a monomolecular layer of DDVP adsorbs in the active site serine of BuChE which is deeply located at the bottom of a narrow (20 Å) gorge and takes up more space at the extent of 10 Å. The poisoned mechanism of BuChE by DDVP has also been discussed. The linear relationship between the frequency and the concentration of DDVP exists in a range from 6.54ppm to 32.7ppm. This method has also been applied to determine DDVP in several samples of organophosphorus pesticides. The present results of our studies are quite satisfactory.