GC-MS Determination of 5 Amides in Nylon and Other Food-Contacting Materials with Separation by Ultrasonicated Extraction

Conditions of ultrasonicated extraction for separation of 5 amides (i.e., acrylamide, methylacrylamide, caprolactam, oleamide and stearamide) from plastic food-contacting materials, e.g., nylon, were studied and optimized. The food-contacting material, as sample for analysis should be washed, air-dried and cut to small pieces of 0.5 cm×0.5 cm. A portion of the cut sample (1.00 g) was taken and extracted twice ultrasonically for 30 min at 25℃ using 25 mL of methanol in each extraction. The mixture was filtered, and the 2 filtrates were combined and evaporated to near-dryness by N₂-blowing at 45℃. The residue was dissolved and diluted to 50 mL with methanol. An aliquot of 1.0 mL was taken and filtered through 0.22 μm filtering membrane. The filtrate was used for GC-MS analysis under the working conditions of the instrument. Agilent HP5-MS chromatographic column and program of temperature elevation from 60℃ to 270℃ were adopted in GC-separation. MS determination was done at the respective retention times of the 5 amides. Linearity ranges of the standard curves of the 5 amides were found same between 5 to 100 mg·L^-1. Their detection limits (3S/N) were found in the range of 0.08 to 1.0 mg·L^-1. Using a blank sample as matrix, test for recovery was made by addition of mixed standard solution, giving results of recovery in the range of 90.2% to 104%. Values of RSDs (n=6) found were in the range of 0.78% to 1.7%. 4 substantial samples were analyzed by the present method, and only caprolactam was found in the nylon sample, giving a values of 10 mg·kg^-1, which was lower than the limit of migration (15 mg·kg^-1) as stipulated by the European Economic Community.