Objective:To determine the contents of amino acids of different origin of Dendrobii Officinalis Caulis. Method: The amino acids in Dendrobii Officinalis Caulis pretreated with phenyl isothiocyanate (PITC) and the content of derivatives was determined by HPLC.The determination was performed on CAPCELL PAK C18SG300 (4.6 mm×250 mm

5 μm) column with mobile phase A consisted of sodium acetate-acetic acid buffer solution (adjusted pH to 6.5 with acetic acid)-1% acetonitrile and mobile phase B consisted of sodium acetate-acetic acid buffer solution(adjusted pH to 6.5 with acetic acid);gradient elution.The column temperature was 25 ℃

flow rate was 0.6 mL · min -1

the detection wavelength was 254 nm. Result: The recovery of free amino acid and total amino acids were in the range of 92.48%-97.30% and 90.95%-95.63%

the RSD values are less than 3%. Different origin of free amino acid content of 10 samples in the range of 0.210 5%-0.571 2%

the total amino acid content in the range of 3.670 8%-6.890 4%

the essential amino acids accounted for the proportion of total free amino acids in the range of 0.094 4%-0.186 0% and accounted for the proportion of total amino acids in the range of 0.338 5%to 0.374 1%. Conclusion: The method is sensitive

accurate

with good repeatability and stability

can be used for the detection of amino acids in Dendrobii Officinalis Caulis

there was significant difference between the different origin of Dendrobium candidum samples of amino acid

there are differences in the proportion of essential amino acids.