The result of survey other factors: The concentration of L-Arginine aspartate and L-Lysine hydrochloride were 200 mg / ml and 40 mg / ml, respectively; the duration for reaction between amino acids and OPA was 30 seconds; the concentration of o-phtalaldehyde to react with amino acids was 4000 mg / ml. The method was validated for specificity, linear (r > 0.999), precision (the mean recoveries in the range of 98.0 - 102.0% of the expected values), accuracy (RSD < 2%) and robustness (RSD <2%).