In an article published on September 20 in the peer-reviewed journal Polymer Testing, Di Feng and colleagues from the Beijing Laboratory for Food Quality and Safety, China report on the non-target analysis of chemicals that could potentially migrate from food contact articles made of silicone rubber. Various processing agents are used in the manufacture of silicone rubber, including antioxidants, fillers, vulcanizing agents, vulcanized accelerators, and diverse other residual additives. In addition, impurities in raw materials, as well as the newly-formed substances, may also be present in the final product (see also FPF background article).
The researchers analyzed 30 infant teats made of silicone rubber, bought in China in 2014-2015. Two extraction methods were compared, solid phase microextraction (SPME) and the purge-and-trap (P&T) method, both particularly suited for the analysis of volatile compounds. Compared to P&T, the SPME approach allowed for a simultaneous extraction of more compounds belonging to more chemical groups; however, volatile compounds with lower molecular weights were best extracted by the P&T method.
In total, 140 compounds, belonging to 12 categories, could be identified by combining the two extraction procedures. The 12 categories were alkanes, siloxanes, esters, aldehydes, aromatics, alcohols, ketones, ethers, phenols, thiazoles, amines, and terpenes.
To prioritize the detected 140 compounds for a more detailed safety evaluation, the authors performed a screening consisting of the following steps:
- Screening based on detection rate: removing the compounds with detection rates less than 10% (61 compounds excluded).
- Screening based on retention index: removing the compounds without published retention indices, except for those confirmed by the analytical standards (21 further compounds excluded).
- Screening based on relative content: removing the compounds with a relative content less than 1%, as estimated based on semi-quantification of chromatographic peaks (5 further compounds excluded).
As a result of this screening, the remaining 53 compounds were prioritized for further investigation. Among these compounds, the authors specifically highlight several alkanes, siloxanes, aromatics, and aldehydes, as well as trimethylsilanol (CAS 1066-40-6), butylated hydroxytoluene (BHT, CAS 128-37-0), N,N-dibutylformamide (CAS 761-65-9), and benzothiazole (CAS 95-16-9). For the safety evaluation, migration levels and associated health risks should be further evaluated.
Feng, D., et al. (2016). “Extraction, confirmation, and screening of non-target compounds in silicone rubber teats by Purge-and-Trap and SPME combined with GC-MS.” Polymer Testing 56: 91-98.