Abstract:

A simple and rapid reversed-phase high-performance liquid chromatographic (RP-HPLC) method for the
simultaneous analysis of 22 free amino acids was established and applied to analyze free amino acids in raspberries. The
method was based on pre-column derivatization with 2,4-dinitrofluorobenzene (DNFB). The compounds were separated on
a Hypersil ODS2 column. The mobile phase used was a mixture of phase A containing 40 mmol/L sodium acetate buffer (pH
6.4) and phase B containing 50% acetonitrile-water through the gradient elution. Detection was performed using a diode
array detector at 360 nm. The method showed good linearity with coefficients (R2) of determination varying between 0.993 1
and 1.000 0 and precision (relative standard deviation, RSD) ranging from 0.95% to 4.98%, and recovery rates were in the
range between 97.10% and 103.39% for 22 amino acids. The limits of detection and quantification were 0.39?2.87 μg/mL
and 1.29?9.47 μg/mL, respectively. This method proved to be simple and reproducible and was applied to detect 14 free
amino acids in raspberries, including 6 essential amino acids (EEAs). The contents of EEAs accounted for 29.36% of the
total amino acids. The amino acid content of raspberries is abundant, indicating that this kind of berry has the potential to be
developed into functional foods.

Key words: raspberry, free amino acids, high performance liquid chromatography (HPLC), pre-column derivatization, 2,4-dinitrofluorobenzene