Abstract: In this study, a colorimetric probe was devised and synthesized by coupling a salicylaldehyde moiety, which acts as a recognition unit, to the naphthalimido diazonium salt (a signal unit) through an azo bond for the detection of cyanide. After reacting with cyanide, the absorption bands of the probe shifted from 404 to 505 nm and the color changed rapidly from yellow to red. The probe allowed ratiometric detection of cyanide in aqueous solution with a linear range of 0.5–40.0 μmol/L and a limit of detection (LOD) of 0.13 μmol/L, which is much lower than the maximum contaminant level (1.9 μmol/L) for cyanide in drinking water set by the World Health Organization. The probe also displayed excellent selectivity for CN- rather than other anions including F?, Cl?, Br?, I?, SCN?, AcO?, S2?, H2PO4?, N3? and NO3?. The method developed in this study gave the same results as those from the national standard method in real sample detection. In addition, the probe was successfully used to prepare test strips, which can be used to monitor cyanide conveniently, and the discernible concentration of cyanide can be as low as 5.0 μmol/L.

Key words: cyanide, food, test strip, colorimetric probe, detection