Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

The disposable electrochemical sensors with platinum composite electrode were successfully used for amperometric measurement of thiocholine produced from butyrylthiocholine by enzyme hydrolysis with butyrylcholinesterase (BChE, EC 3.1.1.8). The optimum potential was +500 mV vs the internal Ag/AgI/iodide (1 mmol/l) reference electrode. BChE was crosslinked with albumin and glutaraldehyde over the working electrode. Thus obtained biosensor was tested in various organic solvents (values of the hydrophobicity parameter log P from -1 to 5), no loss of activity was detected after a 5 min incubation in the solvents with log P greater than 2.5. The inhibition of the biosensor with paraoxon was studied in water, toluene, hexane, heptane and nonane. The extent of inhibition increased with solvent hydrophobicity (toluene > hexane > heptane), the inhibition obtained in water was similar as in heptane. Lower response than expected was obtained in nonane. The liquid-liquid extraction of paraoxon from aqueous samples to heptane provided significant improvement of sensitivity of the method. By this method, the lowest detected concentration of paraoxon was 0.03 μmol/l, resulting in the 20% inhibition of the biosensor signal after 5 min preincubation in the heptane extract.

Keywords: Amperometric biosensor; Cholinesterase.