Determination of mass transport properties in food/packaging systems by local measurement with Raman microspectroscopy

Abstract

A fast, nondestructive method based on the determination of local concentration profiles in the polymer thickness with Raman microspectroscopy is presented here. It was used to assess the diffusivity of a model molecule (p‐terphenyl) in amorphous polystyrene films at 95°C (2.38 ± 1.08 × 10−17 m2/s). This methodology was validated by comparison with a more classical destructive approach based on the monitoring of the concentration evolution in the whole of the film with gas chromatography (89.4 × 10−17 m2/s). These values were in agreement with data available in the literature for molecules of the same molecular weight and temperature range determined with local measurement and were significantly lower than those determined by global measurement. Raman microspectroscopy was found to be adapted to slow diffusion speeds typically found in high‐barrier polymers; this allowed diffusivity to be obtained long before the equilibrium was reached and, thus, without the need for the partition coefficient. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40958.

Diffusion of surface-active amphiphiles in silicone-based fouling-release coatings

“…Radioactive labelling [35], infrared microdensiometry [35], fluorescence tracing [36], time-of-flight secondary ion mass spectrometry (ToF-SIMS) [37] and X-ray photoelectron spectroscopy (XPS) [38] have been used with successful results. Similarly, the diffusion of different migrants in polymer hosts has also been studied by methods such as Raman spectroscopy [39], gas chromatography (GC) [39] and infrared spectroscopy (IR) [40] among others.…”

Worst case prediction of additives migration from polystyrene for food safety purposes: a model update

“…A c c e p t e d M a n u s c r i p t these data were determined by Bernardo (Bernardo 2012, Bernardo 2013, and present extremely high diffusion coefficients. As we have speculated (Martinez-Lopez et al 2014), this may be due to an underestimation of their solubility limit, or to the plasticization of PS. Nevertheless, as they represent a significant portion of the data, they should be taken into account for safety purposes.…”

General guidelines for a successful joint determination of the diffusion and the partition coefficients in polymeric food contact materials based on optimal experimental design

“…Consequently, the most intuitive way to determine the partition coefficient would be to run the experiment until a plateau in is observed in the concentration development, and assume that that is the equilibrium state 50,51 . Unfortunately, high barrier polymers exhibiting low or very low diffusion coefficients would require experiment times that may range from several months 50 to hundreds of years, 29 thus making this technique unfeasible. Because of this, an effort to determine the partition coefficients via mathematical modeling has been done 52–56 .…”

“…Other studies based on local measuring make use of more complex setups that allow to perform measurements in precise spots of the sample, and thus give access to the concentration distribution of the diffusing substance. The most popular among these have been Raman microspectroscopy 8,29,43 and fluorescence recovery after photobleaching. [39][40][41][42] The former can perform measurements with a spacing as narrow as 1 μm, while the latter is capable of measuring the two dimensional diffusion on a thin film, despite the caveat of requiring diffusing substance to be responsive to photobleaching.…”