Low-cost and portable absorbance measuring system to carbamate and organophosphate pesticides

This manuscript describes the development of a low-cost and portable solid-state absorbance measuring system that detects the thiocoline after the hydrolysis of substrates acetylthiocholine (ACTh) by acetylcholinesterase. Consisting in measure the relation between the amount of light transmitted through and absorbed by the enzymatic reaction that is carried out in the cuvette and expressed in voltage value. The proposed system indicated a detection limit of the enzyme (6.91 × 10−4 absorbance units/s) that is lower than the commercial diode-array spectrophotometer (2.29 × 10−3 absorbance units/s) equipment model 8452A from Hewlett-Packard. The working ranges for the developed system were 6.58 mM to 36.5 μM and 19.8 mM to 349 μM for the spectrophotometer, respectively. In addition, the system was employed to calculate the kinetic inhibition constants of three different enzymes (Electric Eel, Drosophila melanogaster and Genetically-modified D. melanogaster) toward paraoxon, carbofuran and malaoxon pesticides.