Migration due to indirect contact with packaging caused several major sanitary crises, including the spread contamination of dry food by mineral oils and printing ink constituents from cardboard. The issues are still not fully resolved because the mechanisms have been insufficiently described and the relationship between design, contamination level, type of contaminant, and conditions of storage (time and temperature) are poorly understood. This study proposes a forensic analysis of these phenomena when food is separated from cardboard by a plastic layer. Practical relationships and advanced simulation scenarios were devised and validated against the long-term migration between 20 and 60°C of 15 substances. They were chosen to be representative of the main contaminants of cardboard: aliphatic and aromatic mineral oils, photo-initiators and plasticisers. Data were summarised as iso-contamination curves and iso-contamination times up to 2 years. Simple rules are illustrated to extrapolate the results to arbitrary conditions in order to identify critical substances and to estimate the plastic film's thickness to keep the contamination within acceptable limits. Recommendations for the risk management of contamination routes without contact are finally drafted.
Blind deformulation is an important stake for several industries. This work was motivated by the identification and quantification of contaminants originated from food packaging systems. Many substances originating from plastic materials are indeed suspected to be endocrine disruptors but remain chiefly difficult to separate with spectroscopic techniques. We propose a tailored two-scale pursuit methodology to identify and quantify an arbitrary number of substances from the 1 H NMR spectrum of the mixture. Identified substances are included within a library of spectra and can be combined with undocumented ones. To preserve the initial resolution of NMR spectra, peak lines are spanned onto Gaussian kernels so that they can be identified, even when the positions and shapes of multiplets in the mixture are modified within tolerance ranges or when multiplets are overlapping. The deconvolution procedure starts with a crude pairwise search to build a list of likely substances, which is subsequently expanded as nested scenarios. Scenarios are built according to the risk of confusing similar substances. Quantification is carried out on a preference list of substances selected as in a voting system. Using a primary library of 52 substances (corresponding to 279 multiplets and 5620 lines), the reliability and robustness of the method were tested extensively in numerical experiments and by performing the brute-force deformulation of five processed common thermoplastics.
We report on a new accurate investigation tool whose principle is that of a Michelson interferometer with a broadband source, namely a phase-sensitive optical low-coherence interferometer, used to interrogate an optical micro-resonator based sensor for label-free biosensing applications. This set-up, which is able to provide the amplitude and also the phase of the guided mode in a single measurement, is also used to evaluate the performances of the micro-resonators. The best vertically coupled polymer racetrack micro-resonator fabricated displays a Q-factor higher than 38 000 and a finesse of 21 at 1527.7 nm when immersed in deionized water. The association of the phase-sensitive optical low coherence interferometer and the vertically coupled polymer micro-resonator in an opto-fluidic cell for biosensing applications was tested and allowed the detection of a concentration of glucose in water solution around 0.23 mg ml−1.
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