HPLC Determination of Migration Levels of Crotonic Acid from Food Contact Materials

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%.