Design and synthesis of a novel fluorescent reagent, 6-oxy-(ethylpiperazine)-9-(2′-methoxycarbonyl) fluorescein, for carboxylic acids and its application in food samples using high-performance liquid chromatography

A novel derivatization reagent for carboxylic acids, 6-oxy-(ethylpiperazine)-9-(2′-methoxycarbonyl)fluorescein (EPMF) has been well designed and synthesized. It was used to label 13 fatty acids, n-butyric acid (C4), n-valeric acid (C5), n-hexanoic acid (C6), n-heptanoic acid (C7), n-octanoic acid (C8), n-nonanoic acid (C9), n-decanoic acid (C10), lauric acid (C12), myristic acid (C14), palmitic acid (C16), stearic acid (C18), oleic acid (C18:1) and linoleic acid (C18:2), successfully. The derivatization reaction with fatty acids was completed at 50 °C, 50 min. The derivatives of fatty acids were separated on a C18 reversed-phase column with gradient elution and fluorescence detection at λex/λem = 469/518 nm. The detection limits obtained were 0.4–2 nmol L−1 (signal-to-noise ratio of 3). The proposed method has been applied to the quantification of fatty acids in edible oil with recoveries over 93%. It has been demonstrated that EPMF is a prominent derivatization reagent for fatty acids and is suitable for HPLC.