Simultaneous determination of cyanide and thiocyanate in swine plasma by high-performance liquid chromatography with fluorescence detection based on a novel D-π-A carbazole-based turn-on fluorescence labeling reagent

The goal of the current work was to develop a simple and sensitive high-performance liquid chromatography in combination with the fluorescence detection (HPLC-FLD) method for the fluorescence turn-on determination of cyanide and thiocyanate in swine plasma. For this goal, we designed and synthesized a novel donor-π-bridge-acceptor (D-π-A) carbazole-based fluorescence labeling reagent, 2-(4-carbazol-9-yl-benzylidene)-malononitrile (CBM), to label cyanide and thiocyanate. Cyanide and thiocyanate can be rapidly labeled by CBM within only 5 min at room temperature (25 °C). Attractively, CBM itself has no fluorescence, while its cyanide and thiocyanate derivatives expressed intense fluorescence with the maximum excitation and emission wavelengths of 290 nm and 380 nm, which extraordinarily diminished the background interference and improved the detection sensitivity of cyanide and thiocyanate. The labeled derivatives were analyzed on a reversed-phase Eclipse XDB-C8 column within 8 min. The excellent linearities (R² > 0.996) of cyanide and thiocyanate were achieved with the limits of detection (LODs) and the limits of quantitation (LOQs) in the low micrograms per litre levels of 0.25 and 0.30 μg L^-1, 0.80 and 1.00 μg L^-1, respectively. Using the proposed HPLC-FLD method, we successfully determined the endogenous cyanide and thiocyanate in swine plasma with good applicability. Furthermore, the developed sensitive and reliable method could also be used for the determination of cyanide and thiocyanate in other samples.