An article published on June 8, 2018 in the peer-reviewed journal Talanta reported on a nontarget analysis of nonvolatile compounds migrating from polypropylene (PP)-based food packaging films. Paula Vera and colleagues from the Analytical Chemistry Department, University of Zaragoza, Spain analyzed 26 manufacturer-provided samples of PP films used in the EU market to package a wide variety of foodstuffs. For each sample, migration experiments were performed with one or more of the four different food simulants, chosen depending on the intended use of the packaging film in question (often, more than one use was reported by the manufacturer). The four food simulants used were ethanol 10%, acetic acid 3%, ethanol 95%, and Tenax. The migrates were analyzed by liquid chromatography coupled with mass spectrometry (LC-MS) technique on a quadrupole time-of-flight (QTOF) mass spectrometer.
In total, the researchers identified and quantified 74 compounds. 16 of these substances were intentionally added substances (IAS), i.e., known to be authorized for plastic food contact materials (FCMs) and commercially used during PP manufacturing as, e.g., stabilizers, plasticizers, slip agents, surfactants, or lubricants. The remaining 58 chemicals were considered to be non-intentionally added substances (NIAS), as their intentional use in PP films could not be identified in the literature. The scientists organized these substances into six different groups shortly described next.
- 10 substances that included a 3,5-di-tert-butyl-4-hydroxyphenyl group; they could be degradation products of the antioxidants Irganox 1076 (CAS 2082-79-3) or Irganox 1010 (CAS 6683-19-8), both detected as IAS.
- 15 substances that included a glycerol group; they could be impurities in antifog/antistatic additive glyceryl monostearate (CAS 31566-31-1), detected as IAS.
- 9 substances identified as dihydroxy alquilamines, which could be either impurities, or reaction products, or breakdown products of some IAS; two of these compounds, N,N-bis(2-hydroxyethyl) tridecylamine (CAS 18312-57-7) and N,N-bis(2-hydroxyethyl) pentadecylamine (CAS 24910-32-5), were found in 15 out of 26 PP film samples.
- 7 substances identified as ceramides and dihydroceramides; some are used as functional ingredients in cosmetics, but their origin in plastics is unknown.
- 5 substances formed by amides bonded by ethylene, which could be degradation products of octadecanamide, N,N’-1,2-ethanediylbis- (CAS 110-30-5), a synthetic wax used “as a dispersing agent or internal/external lubricant” (it is unclear why the authors did not include this substance in the IAS list).
- 12 other substances forming structural groups with less members; the compound ‘Irgafos 168 OXO’ (CAS 95906-11-9), an oxo-derivative of Irgafos 168 (CAS 31570-04-4, detected as IAS), appeared in all but one PP film sample.
To assess the risks of migrating compounds, all quantified migration values were compared either to their respected specific migration limit (SML) if listed in the Plastics Regulation (Commission Regulation (EU) No 10/2011), or, for substances not listed in this regulation, to the maximum migration values calculated according to the threshold of toxicological concern (TTC) approach based on Cramer classification.
Five PP film samples did not comply with the Plastics Regulation because the sum of the compounds [N,N-Bis(2-hydroxyethyl) (C8-C18) amine] in the family of dihydroxy alquilamines exceeded their SML of 1.2 mg/kg. In one more sample, Irganox 1076 exceeded its SML of 6 mg/kg in the ethanol 95% food simulant.
With regard to non-listed compounds, six samples showed migration at levels exceeding the maximum values assigned according to Cramer class II (for some degradation products) or class III (for some amide compounds) when ethanol 95% was used as food simulant. Since three of these six samples also did not comply with the Plastics Regulation, this makes for a total number of nine non-compliant samples out of 26 samples overall.
The authors conclude that their work “opens up a wide range of possibilities for . . . companies that can reformulate and substitute some additives which are related with . . . NIAS found.”
Reference
Vera, P., et al. (2018). “Identification of non volatile migrant compounds and NIAS in polypropylene films used as food packaging characterized by UPLC-MS/QTOF.” Talanta (published June 8, 2018).
