Mechanism of Formation of Volatile Organic Compounds from Oxidation of Linseed Oil

Furan-based fluorescent probe free radical capture membrane: Analysis of RO2 radical composition and transformation mechanism in urban atmosphere

Peroxyl radicals (RO2) are important components of atmospheric radical cycling and generation, but their formation, distribution and evolution mechanisms in the atmospheric environment have not been investigated. In this paper, we propose a novel atmospheric RO2 radical trapping membrane that can trap low carbon number (Rc ≤ 5) RO2 radicals and identify their R-group structures by fluorescence spectroscopy and chromatography. We also analyzed the composition and evolution mechanism of RO2 species under different meteorological conditions in the atmospheric environment of Lanzhou, China, to provide scientific support for the treatment and research of atmospheric chemical pollution.

Oil Media on Paper: Investigating the Effect of Linseed Oils on Lignocellulosic Paper Supports

Condition assessment of works of art created with oil media on paper could be a complex matter when presenting problems of damage due to the absorption of oil binders by the paper support, since they depend on several factors and occur in variable conditions. The present work refers to the results of an investigation on the effect of linseed oils on the color, opacity, morphology, tensile strength, and chemical properties of lignocellulosic papers, in comparison to that of pure cellulosic papers. Lignocellulosic papers are involved in research on new, yet significant, parameters that might influence the behavior of the oil-impregnated areas of the supports upon aging. The research was applied to mock-ups, made of two types of lignocellulosic paper impregnated with three types of linseed oil and subjected to accelaratated ageing in specific conditions of relative humidity and temperature in closed environment. The research involved colorimetry, opacity, tensile strength, pH measurements, SEM, FTIR, and VOC analysis with GC-MS. The results indicated that thermal-humid ageing caused the gradual darkening of the oil-impregnated mock-ups, alterations in opacity, and decrease of pH values, depending mainly on the formulation of linseed oil, as well as a reduction in tensile strength. FTIR analysis results indicated that the chemical changes that occur upon ageing supported the recorded optical and mechanical alterations, while VOC emissions are both associated with the paper type and the kinetics of degradation of the different types of linseed oil.

Oil Media on Paper: Investigating the Effect of Linseed Oils on Pure Cellulosic Paper Supports. A Research Matter of Damage Assessment

Oil media on paper, such as oil paintings, sketches, prints, and books, occasionally present problems associated with the effect of oil medium on the paper support, raising a composite matter of condition assessment as it depends on several factors. The present work examines the effect of linseed oil on paper and, in particular, the changes caused by three types of linseed oil on the optical, morphological, mechanical, and chemical properties of pure cellulosic paper, employing mock-ups submitted to artificial ageing in controlled conditions of relative humidity and temperature in airtight vessels. The study involved colorimetry, opacity, tensile strength, pH measurements, SEM, FTIR, and VOC analysis with GC-MS. Processing of the results has so far indicated that thermal-humid ageing caused the gradual darkening of the oil-impregnated mock-ups, as well as alterations in opacity, intense fall of pH values, and severe reductions in tensile strength, while linseed oil processing during manufacture has a significant impact. FTIR spectra have indicated that chemical changes upon ageing are in accordance with those of optical and mechanical changes, while VOC emissions are mostly associated with the drying and degradation of the different types of linseed oil.

Mechanism, indexes, methods, challenges, and perspectives of edible oil oxidation analysis

Edible oils are indispensable food components, because they are used for cooking or frying. However, during processing, transport, storage, and consumption, edible oils are susceptible to oxidation, during which various primary and secondary oxidative products are generated. These products may reduce the nutritional value and safety of edible oils and even harm human health. Therefore, analyzing the oxidation of edible oil is essential to ensure the quality and safety of oil. Oxidation is a complex process with various oxidative products, and the content of these products can be evaluated by corresponding indexes. According to the structure and properties of the oxidative products, analytical methods have been employed to quantify these products to analyze the oxidation of oil. Combined with proper chemometric analytical methods, qualitative identification has been performed to discriminate oxidized and nonoxidized oils. Oxidative products are complex and diverse. Thus, proper indexes and analytical methods should be selected depending on specific research objectives. Expanding the mechanism of the correspondence between oxidative products and analytical methods is crucial. The underlying mechanism, conventional indexes, and applications of analytical methods are summarized in this review. The challenges and perspectives for future applications of several methods in determining oxidation are also discussed. This review may serve as a reference in the selection, establishment, and improvement of methods for analyzing the oxidation of edible oil. HighlightsThe mechanism of edible oil oxidation analysis was elaborated.Conventional oxidation indexes and their limited values were discussed.Analytical methods for the determination of oxidative products and qualitative identification of oxidized and non-oxidized oils were reviewed.

Application of Artificial Neural Network Based on Traditional Detection and GC-MS in Prediction of Free Radicals in Thermal Oxidation of Vegetable Oil

In this study, electron paramagnetic resonance (EPR) and gas chromatography-mass spectrometry (GC-MS) techniques were applied to reveal the variation of lipid free radicals and oxidized volatile products of four oils in the thermal process. The EPR results showed the signal intensities of linseed oil (LO) were the highest, followed by sunflower oil (SO), rapeseed oil (RO), and palm oil (PO). Moreover, the signal intensities of the four oils increased with heating time. GC-MS results showed that (E)-2-decenal, (E,E)-2,4-decadienal, and 2-undecenal were the main volatile compounds of oxidized oil. Besides, the oxidized PO and LO contained the highest and lowest contents of volatiles, respectively. According to the oil characteristics, an artificial neural network (ANN) intelligent evaluation model of free radicals was established. The coefficients of determination (R2) of ANN models were more than 0.97, and the difference between the true and predicted values was small, which indicated that oil profiles combined with chemometrics can accurately predict the free radical of thermal oxidized oil.

Low temperature oxidation of linseed oil: a review

This review analyses and summarises the previous investigations on the oxidation of linseed oil and the self-heating of cotton and other materials impregnated with the oil. It discusses the composition and chemical structure of linseed oil, including its drying properties. The review describes several experimental methods used to test the propensity of the oil to induce spontaneous heating and ignition of lignocellulosic materials soaked with the oil. It covers the thermal ignition of the lignocellulosic substrates impregnated with the oil and it critically evaluates the analytical methods applied to investigate the oxidation reactions of linseed oil.

Initiation of radical chains by singlet oxygen (1Δg), and their propagation underpin the mechanism of oxidation of linseed oil, leading to the self-heating and formation of volatile organic species and higher molecular weight compounds. The review also discusses the role of metal complexes of cobalt, iron and manganese in catalysing the oxidative drying of linseed oil, summarising some kinetic parameters such as the rate constants of the peroxidation reactions.

With respect to fire safety, the classical theory of self-ignition does not account for radical and catalytic reactions and appears to offer limited insights into the autoignition of lignocellulosic materials soaked with linseed oil. New theoretical and numerical treatments of oxidation of such materials need to be developed. The self-ignition induced by linseed oil is predicated on the presence of both a metal catalyst and a lignocellulosic substrate, and the absence of any prior thermal treatment of the oil, which destroys both peroxy radicals and singlet O2 sensitisers. An overview of peroxyl chemistry included in the article will be useful to those working in areas of fire science, paint drying, indoor air quality, biofuels and lipid oxidation.