Amino Acid Profiling of Samples by UPLC

The amino acid profile of the sample was analyzed according to a previous method with modifications [45 (link)]. The analysis was performed using Acquity ultrahigh-pressure liquid chromatography (UPLC) equipped with a photodiode array detector (Waters, Milford, MA, USA). Approximately 0.1 g of the sample was hydrolyzed with 5 mL of 6 M HCl at 110 °C for 22 h. The mixture was then transferred to a 50 mL volumetric flask and filtered with 0.45 µm filter paper. Then, 500 µL of filtrate was added to 40 µm α-aminobutyric acid as an internal standard and 460 µL of double-distilled water. Then, 10 µL of the solution was added to 70 µL of AccQ-Fluor borate buffer (Waters, USA) and 20 µL of reconstituted Fluor reagent (Waters, USA). The mixture was then incubated at 55 °C for 10 min, and 1 µL of the filtrate was injected into the UPLC system.