Paper Strip-based Fluorometric Determination of Cyanide with an Internal Reference

The rapid, selective, and sensitive determination of cyanide anion (CN (-)) using a simple paper strip is highly attractive because cyanide is acutely lethal to living organisms via all routes of administration, including alcohol consumption and inhaling cigarette smoke. Here, a synthetic probe (1) was designed for the selective determination of cyanide. The probe displays rapid and large blue spectral change ((abs) =148 nm, (em) = 165 nm) with respect to target recognition. Probe 1 exhibits a strong push-pull electronic effect and comprises a dimethylaminoaryl group as a donor and malononitrile as an acceptor; the -conjugation system can be destroyed by the Michael-type addition of cyanide at the electrophilic -positions of the nitrile groups, resulting in the marked emergence of a peak at (em) = 515 nm. The developed probe was successfully applied to a paper test strip because of its noticeable optical changes upon reaction with cyanide. The fabricated dumbbell-shaped paper strip with an internal reference allowed the cyanide detection, which is indispensable for quantitative analysis in point-of-care testing. The paper strip test showed selective response to cyanide, with a linear correlation in the range of 0-25 mM in a simple and cost-effective manner.