HPLC Determination of Resin Acids in Adhesives

The sample (2.500 g) was dissolved in 5 mL of ethyl acetate, and 15 mL of methanol was added into the solution to whirl for 0.5 min. The mixture was centrifuged at rate of 6 000 r·min^-1 for 10 min, and the centrifuge tube and sedimentation were washed by methanol. The supernatant and washing solution were combined and made its volume up to 25 mL. The above solution obtained was separated by HPLC using Waters XTerra RP18 column as the stationary phase and a mixture of acetonitrile-0.4% (φ) acetic acid solution (80+20) as the mobile phase. Detection wavelengths were 200 nm for dehydroabietic acid and 216 nm for abietic acid isomers. Linear relationships between values of peak area and mass concentration of resin acids were obtained in the range of 1.0-100.0 mg·L^-1, with lower limits of determination (10S/N) of 3.0 mg·kg^-1 for dehydroabietic acid and 10.0 mg·kg^-1 for abietic acid isomers. Test for recovery was made by standard addition method, giving results in the range of 91.9%-98.0%, with RSDs (n=6) ranged from 0.26% to 2.8%.