Determination and Migration of Three Kinds of Cyclosiloxanes in Food Contact Silicone Rubber

The contents of octamethylcyclotetrasiloxane(D4),decamethylcyclopentasiloxane(D5)and dodecamethylcyclohexasiloxane(D6)in food contact silicone rubber were respectively determined by solvent extraction-gas chromatography/mass spectrometry(solvent extraction-GC/MS),and the migration of D4~D6 from silicone rubber baking tray to oily food simulants were studied. Attenuated total reflectance-Fourier transform infrared spectroscopy(ATR-FTIR)was used to identify these three kinds of silicone rubber products. GC/MS was performed to detect the contents of D4~D6 in silicone rubber,which were extracted by optimized procedure using n-hexane and ultrasonicating for 30 min. Single~sided migration test was carried out with one kind of silicone rubber baking tray. The results showed that D4~D6 had good linearity within the mass concentration range of 0.5~20.0 μg/mL while the determination coefficients(R²)were greater than 0.9961.The detection limits were all less than 11.2 ng/mL and the quantitative limits were all less than 37.2 ng/mL. The average recoveries of D4~D6 were 85.20%~98.12% and the relative standard deviation(RSD)were 2.17%~4.27%(n=6). The results also showed that the contents of D4~D6 in both the silicone rubber nipple and the pressure cooker sealing ring were lower,while the contents of D4~D6 in the silicone rubber baking tray was the highest with the average values of D4~D6 being 175.08,824.12 and 901.17 mg/kg,respectively. Through migration test,it was found that the migration rate of D4~D6 in the silicone rubber baking tray were 71.36%,57.03% and 49.31%,when the migration of D4~D6 reached equilibrium in oily food simulants of 95% ethanol at 60 ℃. It indicates that D4~D6 will migrate into oily food,and D4 with small molecular weight is easier to release,and the relative safety issue cannot be ignored.