Rapid detection of isoprene based on UV-visible spectrophotometry

Isoprene, as the most abundant non-methane hydrocarbon, is mainly emitted by terrestrial plants, and can be oxidized into various secondary organic aerosols in the atmosphere. To detect isoprene efficiently is necessary for atmospheric chemistry research. In the present work, an optical probe for isoprene, benzo[g]phthalazine-1,4-dione (BPAD), was designed. The N=N group in BPAD is able to undergo Diels-Alder (D-A) reaction with isoprene, resulting in a significant decrease in absorbance at 420 nm, which make it possible to detect isoprene quantitatively. This method provides a detection limit 25 nmol·L−1 for isoprene in solution. Moreover, the isoprene amount in the atmosphere was measured using the method, and the values, (24.9 ± 0.6) μg·m−3 and (13.7 ± 1.3) μg·m−3, were obtained at the daytime and nighttime, respectively. Compared with the traditional chromatographic method, the optical method presented here is characteristic of low cost, less instrument-dependence and simple operation, providing an efficient and economical means for real-time monitoring of isoprene.