Analysis of cyanide using fluorogenic derivatization and capillary electrophoresis

Abstract

Samples containing cyanide were incubated at 85 °C in the presence of the fluorogenic reagent 3-(2-furoyl)quinoline-2-carboxaldehyde (FQ) and glutamic acid, and analyzed by capillary electrophoresis utilizing post-separation laser-induced fluorescence detection in a sheath flow cuvette. The separation time on a 25 cm long capillary at 800 Vcm−1 was 3 min with the fluorescent product eluting at 107 s. Flushing of the capillary was not required between runs. Signal was proportional with cyanide concentration from 50 nM to 1.5 μM. LOD and LOQ were determined to be 26 and 87 nM respectively. As an application, free cyanide in five individual apple seeds was measured and found to range from 12 to 86 ng/mg, with a mean of 55 ± 32 ng/mg. As a means for the detection of amygdalin, cyanide was enzymatically produced from amygdalin using the enzymes β-glucosidase and mandelonitrile lyase. The cyanide was then reacted with FQ and injected onto the capillary. Amygdalin was detected at a concentration of 1 μM.