Abstract: The sample 0.250 0 g was dissolved in 5 mL of ethyl acetate, and contents of polymers in the solution were precipitated by addition of 15 mL of methanol. After standing for 5 min, the supernatant was taken and preserved. The precipitate was washed ultrasonically with methanol (5 mL in each washing) for 3 times. The washings were combined with the sepernatant and diluted to 50.0 mL with methanol. The solution was used for HPLC determination of the antioxidant 2246, using the column of Agela Venusil XBP C₁₈ as the stationary phase and mixture of CH₃OH and H₂O (9+1) as mobile phase in the separation. Method of external standard was adopted for quantification. Linear relationship between values of peak area and the respective mass concentrations of the antioxidant 2246 was kept in the range of 0.100-10.0 mg·L^-1, and value of lower limit of determination (10S/N) was found to be 0.002%. Test for recovery was made by addition of standard solution at 2 concentration levels of 0.100%, 0.250%, giving values of recovery of 99.8%, 97.7% and RSDs (n=6) of 0.3%, 0.2% respectively. The results of HPLC were further verified by HPLC-MS/MS analysis.