Determination of Methionine Sulfoxide in Compound Amino Acid Injection by HPLC with OPA Pre-column Derivatization

OBJECTIVE To establish a method for the content determination of methionine sulfoxide in Compound Amino Acid injection. METHODS O-phthaladehyde(OPA) pre-column derivatization HPLC was performed on the column of Agilent ZORBAX Eclipse AAA C₁₈(150 mm×4.6 mm, 5 µm) with mobile phase A 0.04 mol·L^-1 sodium dihydrogen phosphate solution (adjust pH to 7.8), mobile phase B acetonitrile-methanol-water (45:45:10)(gradient elution) at the flow rate of 2.0 ml·min^-1, the detection wavelength was 338 nm and the column temperature was 40℃. The sample solution was automatic mixed with OPA agent and borate buffer according to set procedure. RESULTS The linear range of methionine sulfoxide was 0.000 5-0.050 0 mg·mL^-1(R=0.999 9). The limit of quantitation was 0.250 5 μg·mL^-1, and the limit of detection was 0.083 5 μg·mL^-1. RSDs of precision, stability and repetitive test were all <3.0%. The average recovery was 99.1%(RSD=1.33%, n=9). CONCLUSION The method is simple, rapid and suitable for the content determination of methionine sulfoxide in Compound Amino Acid injection.