Detection of Methyl-Parathion in Seawater with an Enzyme Sensor Based on FIA and Colorimetric Principle

An AChE biosensor,connected with a flow injection analysis system(FIA),was derigned to detect methyl-parathion in seawater rapidly,by colorimetric determination of the activity change of the immobilized AChE from the organophosphorus pesticide.The working conditions for this system were optimized as follows: the temperature was 30 ℃;the dosage of immobilized AChE in the reactor was 0.05 U;the flow rate was(0.45 mL/min) for both the carrier and the samples,the inhibition time from the samples lasted for 20 min;the concentration and injection volumes of the substrate and the acetylthiocholine iodide were 0.100 mol/L and 100 μL respectively.Linder these conditions,the percent inhibition of the immobilized AChE increased with the concentration of methyl-parathion in seawater.For the samples with methyl-parathion from 0.1 μg/L to 100 μg/L,there was a good linearity(r=0.995?3) between the biosensor response and the logarithm of methyl-parathion concentration.When the system was used to measure the samples containing 0.8 μg/L and 5.0(μg/L) methyl-parathion,better accuracies and precisions were obtained,both the average relative error and the RSD were less than 10%.