The amino acid compositions of tannery skin bit and its hydrolysates were determined by HPLC with pre-column derivatization method. The samples were firstly hydrolyzed by 6 mol/L HCl at 110 ℃ or 10 h, and then pre-column derivatized with phenyl isothiocyanate and separated by HPLC under the condition of gradient elution using a Inertsil ODS-3 C18 column (250 mm ×4.6 mm, 5 μm). The mobile phase A and B were acetonitrile and 0.1 mol/L sodium acetate, respectively. The injection volume of sample solution was 20 μL. The column temperature was 40 ℃ . The flow rate was 0.8 mg/mL and the wavelength for detection was 254 nm. It was found that the amino acid compositions of tannery skin bit and its hydrolysates were accurately determined by this method. Moreover, there were some differences in amino acid composition between tannery skin bit and its hydrolysates. The glycin content of skin bit hydrolysates prepared by protease 537, protease 1398 and protease 2709 was all lower than that of skin bit, but the content of basic amino acids in protease hydrolysates was higher while the acidic amino acid content in protease 537 and protease 1398 hydrolysates was lower compared with skin bit. Meanwhile, the methionine content of the skin bit hydrolysate prepared by protease 2709 was twice of that in skin bit. In general, this research provided an effective approach for the determination of amino acid composition of collagen and collagen hydrolysate.
