Simple and rapid colorimetric detection of p-nitrophenyl substituent organophosphorous nerve agents

We report a very simple and rapid chemical method for the detection of paraoxon and its p-nitrophenyl organophosphorous derivatives. The method uses only sodium borohydride followed by thermal enhancement that increases the sensitivity by two orders of magnitude. Visible, yellow color change of the neurotoxins caused by p-nitrophenolate ions can be rapidly observed at micromolar concentrations while UV–vis measurements enable unprecedented detection at the nanomolar level.