Malachite Green and Leuco-Malachite Green Detection in Fish Using Modified Enzyme Biosensor

A modified enzyme-based biosensor was developed for amperometric measurement of total Malachite Green (sum of MG and LMG) in tilapia fish. The 4 UmL-1 butyrylcholinesterase enzyme (BuChE) was used and immobilized onto the surface of carbon paste electrode during the electro-polymerization of polypyrrole (PPy). It is a simple, rapid and sensitive technique used for determination of total MG using 0.1M phosphate buffer pH 8.0. In this study, butyrylthiocholine iodide (0.3 Mm BTCi) was used as a substrate which produced the thiocholine due to the enzymatic hydrolysis. Then, it was oxidized at 0.4V against silver-silver chloride electrode for 100 s. The modified enzyme biosensor provided a high sensitivity and linear concentration range from 0.25 to 10 ppb with a limit of detection (LOD) at 0.25 ppb. The results showed the linear standard curve of total MG standard solution (based on the current output in microampere) with the equation of y = - 0.9113x + 10.84, R2 = 0.9445.