Abstract: This paper used RP-HPLC to assay the whole free amino acids in fruits of 4 Litchi varieties. In this method, OPA and FMOC were selected as pre-column derivatizing reagent, NVAL as Internal Standard, and DAD variable-wavelength as measure function. The results showed that the RSD% for RT and Ax/AI of Amino Acids was from 0.01% to 3.02% and from 1.19% to 7.82% respectively. In the present study , the reclaim ratio was as high as 92.21% to 114.24%, indicating that this method was appropriate for free amino acid determination in fruits of Litchi varieties. The main free amino acids of fruits of four Litchi varieties are Ala,Glu, Arg, Asp and Phe, which occupied 60%of total free amino acids . Among four Litchi varieties , the content of total free amino acids from high to low is Huizhi, Luomizi, Heiye and Guiwei.

Key words: Litchi, total free amino acids, RP-HPLC, variable-wavelength measure