In the past decade, applications of nanocomposites consisting of polymers and engineered nanoparticles have been significantly expanded, causing increasing concern about the release of nanoparticles and their by-products which may impact human health and the environment. This research aims to evaluate the release of nanoclay and surfactant (organo-modifier of nanoclay) from nanocomposites into food simulants.A graphite furnace atomic absorption spectrometry (GFAAS) method was developed for rapid measurement of organo-modified montmorillonite (O-MMT) concentration in water-ethanol solutions with Si and Al as markers of the nanoclay. Special precautions were taken to ensure the stability of O-MMT in water-ethanol solutions. A solution with an ethanol concentration higher than 70 % (v/v) was preferred to obtain a good dispersion of O-MMT in the sonicated solutions, while the dispersion in water was improved by the addition of an organic surfactant. The correlation between Si and Al concentrations and O-MMT concentrations in solution gave the composition of O-MMT which was in agreement with the results obtained by an X-ray fluorescence spectrometry (XRF) method. A liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed to measure the surfactant released from O-MMT into food simulants. Two types of O-MMT containing different quaternary alkylammonium surfactants were used. The release of surfactant from O-MMT was evaluated as a function of temperature, sonication and simulant type. There was more surfactant released at a higher temperature than at a lower one. More surfactant was released when sonication was applied to the nanoclay suspension. A substantial amount of surfactant was released into ethanol, while much less was released into the water/ethanol mixture (1:1, v/v) or pure water. The affinity between the solvent and the surfactant was discussed based on solubility parameters and correlated with the surfactant release into different solvents.Release assessment of O-MMT nanoclay and surfactant was performed on two types of polymer-clay nanocomposites: polypropylene (PP) and polyamide 6 (PA6) with O-MMT. The release experiment was carried out in accordance with ASTM D4754-11 with the nanocomposite films exposed to ethanol as a fatty-food simulant at 22, 40 and 70 °C. A GFAAS method was developed to measure the release of nanoclay. Both nanocomposites released small amounts of nanoclay particles (μg L-1 level) into ethanol. There were more nanoclay particles released from PP-clay films than PA6-clay films. There was no difference in the amount of nanoclay released from PP-clay films with different film thicknesses, revealing that the release mainly occurred at the film surface. A LC-MS/MS method was developed to identify and quantify the surfactant released into ethanol from the two nanocomposite systems. A substantial amount of surfactant in ethanol (mg L-1 level) was detected, indicating changes in the nanoclay structure within the nanocomposite while exposed to the solvent. Finally, Fick's diffusion equation was applied to describe the surfactant release. The diffusion coefficients were on a scale of 10-13 to 10-12 cm2 s-1 for the surfactant release from PP-clay films, and 10-13 to 10-10 cm2 s-1 for the surfactant release from PA6-clay films.
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