Using N-aminoperylene-3,4:9,10-tetracarboxylbisimide as a fluorogenic reactand in the optical sensing of aqueous propionaldehyde

Aldehydes are usually determined via chemical derivatization using a chromogenic and fluorogenic reagent followed by chromatographic separation and UV-visible detection. As a consequence, continuous on-line monitoring is impossible. Following our concept of reversible chemical reactions as the basis of optical sensors, we have investigated N-amino-N'-(1-hexylheptyl)perylene-3,4:9,10-tetracarboxylbisimide for aldehyde sensing. The fluorogenic reactand has been embedded in plasticized PVC, and the resulting thin layers have been exposed to aqueous samples of aliphatic aldehydes and ketones. The reactand exhibits a pronounced increase in fluorescence upon interaction with aldehydes since the chemical reaction causes a dequenching of perylene fluorescence. Upon interaction with aqueous propionaldehyde, sensor layers typically exhibit a dynamic range from 5 to 100 mM propionaldehyde, and the limit of detection amounts to 0.08 mM. The forward and reverse response time (t95) for a decade change in activity is in the range of 2-7 min, when measured at pH 2.5. The selectivity of sensor layers toward aldehydes correlates with their lipophilicity in that aldehydes with higher lipophilicity are more efficiently extracted into the polymer layer.