UV–Vis spectra for solutions of (a) J. decurrens Cham., (d) P. cupana Kunth, (g) marijuana and (b,e,h) FBBBS, and (c,f,i) of the mixture of FBBBS reagent with the three
plants. Note that a band at 471 nm is only observed for marijuana sample with FBBBS, corroborating with the selectivity of the FBBBS reagent