Interlaboratory study on caprolactam test for food-contact nylon products
2016
Watanabe, K. (Japan Chemical Innovation and Inspection Institute, Koto-ku, Tokyo (Japan). Tokyo Office) | Mutsuga, M. | Abe, T. | Abe, T. | Abe, Y. | Ohsaka, I. | Ohno, H. | Ohno, H. | Ohno, Y. | Ozaki, A. | Kakihara, Y. | Kobayashi, H. | Kondo, T. | Shibata, H. | Shirono, K. | Sekido, H. | Sonobe, H. | Takasaka, N. | Tajima, Y. | Tanaka, A. | Tanaka, H. | Nakanishi, T. | Nomura, C. | Haneishi, N. | Hayakawa, M. | Hikida, A. | Miura, T. | Yamaguchi, M. | Sato, K. | Akiyama, H.
The Japanese Food Sanitation Law sets a limit on the migration level of caprolactam for food-contacting nylon products. Here, we carried out an interlaboratory study in twenty laboratories to evaluate the performance of the official GC-FID test method and a GC-MS method as an alternative test method to the official method. Each laboratory quantified caprolactam in three test solutions in 20% ethanol as blind duplicates using GC-FID or GC-MS. The official method (GC-FID with absolute calibration) gave trueness, repeatability (RSDr) and reproducibility (RSDsub(R)) values of 96-97%, 3.3-5.4% and 4.0-6.7%, respectively. These values met the target criteria (trueness: 80-110%, RSDr: 10%, RSDsub(R): 25%). The performance of the method was further improved by the introduction of heptalactam as an internal standard. As for GC-MS method, some values of the RSDr exceeded 10% when absolute calibration was used. However, when an internal standard was introduced, the trueness, RSDr and RSDsub(R) of GC-MS method were all acceptable at 94-96%, 2.0-4.4% and 7.0-9.4%, respectively. Therefore, GC-MS with an internal standard is available as an alternative test method to the official method.
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