Determination of biogenic amines in infusions of tea (Camellia sinensis) by HPLC after derivatization with 9-fluorenylmethoxycarbonyl chloride (Fmoc-Cl)

The reagent 9-fluorenylmethoxycarbonyl chloride (Fmoc-Cl) was used for the pre-column derivatization of the biogenic amines (BAs) cadaverine (Cad), histamine (Him), octopamine (Ocp), phenylethylamine (Pea), putrescine (Put), spermidine (Spd), spermine (Spm), tyramine (Tym) and the internal standard 1,6-diaminohexane (Dhx). The resulting Fmoc-derivatives were resolved by high-performance liquid chromatography on a Superspher(A (c)) C-18 column using a binary gradient generated from sodium acetate and acetonitrile. For quantification, the fluorescence of derivatives was used at 263 nm excitation and 313 nm emission wavelength. This approach was applied to free BAs extractable with boiling water from 14 black, 5 green, 1 Oolong, and 1 instant tea. Infusions were prepared by adding 35 ml boiling water to one gram of tea and extracted for 20 min. In the Oolong tea and two black teas, no BAs could be detected. Limits of detection were 0.07-1.0 pmol for BAs at signal-to-noise ratio 3:1. Besides most abundant Tym and Spm lower quantities of Pea, Put, and Spd were detected, albeit not in all teas. Quantities of Tym ranged from 16 to 431 mu g Tym/L infusion (1.1-25.3 mu gTym/g tea) and 31 to 319 mu g Spm/L infusion (1.5-16.9 mu g Spm/g tea). In none of the teas, Him was detected. Owing to the low amounts of free BAs in tea infusions, no health risks are to be expected even on consumption of large quantities of tea as beverage.