将经处理的样品裁剪成0.3 cm²大小的碎片，取此碎片样品4份，按2 mL·cm^-2的比例分别加入体积分数为10%，20%，50%的乙醇-水溶液和3%的乙酸-水溶液作为4种水基食品模拟物；在另一份样品中，按2 mL·cm^-2的比例加入橄榄油作为油基食品模拟物。以上5份样品及食品模拟物在40℃下浸泡10 d，将4份水基浸泡液分别蒸发至近干，加入甲醇2 mL溶解残渣，所得溶液经0.2 μm滤膜过滤后进行高效液相色谱分析。以C₁₈柱为固定相，用水（预先用甲酸调节酸度至pH 2.7）及甲醇（9+1）的混合液作为流动相进行色谱分离，在波长210 nm处进行紫外检测。测得水基浸泡液中巴豆酸的质量浓度在0.5~10 mg·L^-1内与其峰面积值呈线性关系，检出限（10S/N）为0.5 mg·L^-1；将油基浸泡液用甲醇5 mL振荡约30 s后，静置约10 min，再次振荡约30 s后，静置约10 min后，取出甲醇溶液，重复此甲醇萃取过程2次后，合并甲醇萃取液，蒸发至近干，加入甲醇2 mL溶解残渣，以下操作同上。测得油基浸泡液中巴豆酸的线性范围为1.0~20 mg·kg^-1，检出限（10S/N）为1.0 mg·kg^-1。方法用于测定塑料复合与纸塑复合类食品接触材料中巴豆酸的迁移量，加标回收率在86.2%~116%之间，测定值的相对标准偏差（n=6）不大于3.8%。

The pre-treated sample was cut out into pieces of 0.3 cm² and 4 portions were taken as samples and soaked separately with various water-based food simulants of (φ) 10%, 20%, 50% C₂H₅OH-H₂O solution and (φ) 3% HOAc-H₂O solution with their volumes calculated on the base of the ratio 2 mL·cm^-2. To another portion of the sample, oil-based food simulant of olive oil was added with its volume calculated by the same ratio of volume to area. All the 5 portions of the sample were soaked at 40℃ for 10 d. In case of water-based soakers, each of the 4 soaked extract was evaporated to near-dryness, and the residue was dissolved in 2 mL of CH₃OH. The solution obtained was filter through 0.2 μm filtering membrane and crotonic acid in the filtrate was determined by HPLC, using C₁₈ column as the stantionary phase and mixture of CH₃OH and H₂O (pre-adjusted to pH 2.7 with formic acid) mixed in the volumic ratio of (1+9) as the mobile phase. UV-detection was made at the wavelength of 210 nm. In case of the oil-based soaker, the olive oil was extracted with 5 mL of methanol, by shaking for 30 s and standing for 10 min. The extraction was repeated for 1 time more, and the extract in CH₃OH was separated and reserved. The process of extraction with CH₃OH was repeated for 2 times. The extracts of CH₃OH were combined and evaporated to near-dryness. The residue was dissolved in 2 mL of CH₃OH, and the procedure was carried out in the same way as described above. Linearity ranges were obtained between 0.5 to 10 mg·L^-1 for water-based food simulants and between 1.0 to 20 mg·kg^-1 for oil-based food simulant, with values of detection limits (10S/N) of 0.5 mg·L^-1 and 1.0 mg·kg^-1 respectively. This method was applied to the determination of migration amount of crotonic acid from the food contact materials (including composites of plastics and of paper-plastics), giving values of RSDs (n=6) within 3.8% and values of recovery obtained by standard addition method in the range of 86.2%-116%.