A cyanine fluorophore with a hydrazide functionality as labelling reagent for aldehydes in liquid chromatography

A new hydrazide derivative of a cyanine dye is synthesized for the chemical derivatization of aldehydes. With this red absorbing fluorophore it is possible to apply visible diode laser induced fluorescence (DIO-LIF) detection in conventional-size liquid chromatography (LC). The dye is based on CY5.3a-IA, a sulfonated dicarbocyanine with a iodoacetamido reactive group. The detection limit of n-octylaldehyde is 7 × 10−8 M, limited by the reactivity of the label. Mixtures comprised of strongly resembling aldehydes were derivatized with the label and analyzed by LC-DIO-LIF. The potential applicability in biological problems is shown by the derivatization of 4-hydroxy-2-nonenal (HNE).