To determine the working amounts of sensing components, a range of concentrations for each of them was systematically optimized for the best combination of AChE as the enzyme, DTNB as the chromophore, and ATChI as the artificial substrate. Optimum concentrations were selected according to the quantified colour production and the observation based on the naked eye, since occasionally the proposed biosensor would be used in the field with minimum instrumental help. Figure 3 shows that increasing amount of biosensor components generally resulted in higher colour development as expected. For the determination of the optimal DTNB concentration, up to 5