Biosensor for direct determination of organophosphate nerve agents. 1. Potentiometric enzyme electrode

• Published in: Biosensors & bioelectronics 1999, Vol.14 (1), p.77-85
• Main Authors: Mulchandani, Priti, Mulchandani, Ashok, Kaneva, Irina, Chen, Wilfred
• Format: Article
• Language: English
• Subjects: Aldehydes; Animals; Aryldialkylphosphatase; Biological and medical sciences; Biosensing Techniques - statistics & numerical data; Biosensors; Biotechnology; Buffers; Catalysis; Cattle; Cross-Linking Reagents; Drug products; Electrodes; Enzyme electrode; Enzyme immobilization; Enzyme Stability; Esterases; Fundamental and applied biological sciences. Psychology; Glutaral; Hydrogen-Ion Concentration; Hydrolysis; Methods. Procedures. Technologies; Nerve agents; Nervous System - drug effects; Organophosphates; Organophosphorus Compounds - analysis; Organophosphorus Compounds - toxicity; Organophosphorus hydrolase; pH sensors; Phosphates; Potentiometric; Potentiometric sensors; Potentiometry; Serum Albumin, Bovine; Temperature; Thermal effects; Various methods and equipments
• ISSN: 0956-5663; 1873-4235
• DOI: 10.1016/S0956-5663(98)00096-7

A potentiometric enzyme electrode for the direct measurement of organophosphate (OP) nerve agents was developed. The basic element of this enzyme electrode was a pH electrode modified with an immobilized organophosphorus hydrolase (OPH) layer formed by cross-linking OPH with bovine serum albumin (BSA) and glutaraldehyde. OPH catalyses the hydrolysis of organophosphorus pesticides to release protons, the concentration of which is proportional to the amount of hydrolysed substrate. The sensor signal and response time was optimized with respect to the buffer pH, ionic concentration of buffer, temperature, and units of OPH immobilized using paraoxon as substrate. The best sensitivity and response time were obtained using a sensor constructed with 500 IU of OPH and operating in pH 8.5, 1 mM HEPES buffer. Using these conditions, the biosensor was used to measure as low as 2 μM of paraoxon, ethyl parathion, methyl parathion and diazinon. The biosensor was completely stable for at least one month when stored in pH 8.5, 1 mM HEPES +100 mM NaCl buffer at 4°C.