UV/vis absorption spectra of the OP detection reaction (Scheme 2) in the absence (a) and presence of 8 g/mL of malathion (b). (c) Absorbance at 412 nm of the two reactions shown in (a) and (b) as a function of the reaction time. Note that fewer spectra are shown in (a) and (b) with respect to the data points in (c) for clarity purpose.