Electrochemical Sensing System for Detection of Organophosphate Neurotoxins

Abstract

Jet engine oils contain appreciable amount of toxic ingredients, however are considered safe provided the oil stays in the engine and appropriate precautionary measures are taken. Organophosphorus compound tricresyl phosphate (TCP), known to be a neurotoxin, is widely used as an anti-wear additive in jet engine oils. Bleed air system for cabin air delivery implies a risk of exposing passengers of airliners to TCP and products of its hydrolysis. The development of a highly-sensitive, robust, time and cost-efficient device for TCP detection on an airliner is of an increased practical interest. Electrochemical detection method was chosen in this work as it proved to be the most efficient tool for TCP detection. Non-electroactive TCP was hydrolyzed, and products of alkaline hydrolysis were detected via electrochemical methods. In flight conditions, it is critical to have a reaction design that would ensure a safe, robust and cost-effective hydrolysis of TCP with a high reaction conversion, thus requiring a reliable and effective reaction enhancement method. Ultrasonic irradiation is employed as a novel approach to enhance the alkaline hydrolysis reaction. TCP is hydrolyzed very slowly in neutral or acidic media, and considerably faster in alkaline solution. Boiling-enhanced alkaline TCP hydrolysis was performed to demonstrate the effectiveness of ultrasound irradiation acceleration of this reaction. An additional cresol detection technique, UV-vis spectrophotometry with the demonstrated limit of detection of p-cresol of 100 µM, was used for validation of the effectiveness of alkaline hydrolysis reaction. Electrochemical detection provided a significantly improved limit of p-cresol detection of 0.5 µM. From the perspective of developing a portable and time-efficient sensor for use on airliners, ultrasonic irradiation and electrochemical techniques proved to be effective for enhancing alkaline hydrolysis of TCP and rapid and highly-sensitive detection of cresol.