The chemical stability of both the spray solutions were inspected by UV-vis spectroscopy. Although Solution A remains highly stable in the tests, KMnO4 in Solution B could undergo gradual self-decomposition upon exposure to light and heat. The loss of the purple color and the presence of dark precipitates indicate a deactivation and may result in an invalid spray solution. Under the dark, cool environments, the loss of MnO4 -is 0.77% per day (Figure ), while 11.07% loss of that per day was observed under sunlight.