scholarly journals The Reactivity of Polyethylene Microplastics in Water under Low Oxygen Conditions Using Radiation Chemistry

Water ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3120
Author(s):  
Julie R. Peller ◽  
Stephen P. Mezyk ◽  
Sarah Shidler ◽  
Joe Castleman ◽  
Scott Kaiser ◽  
...  
Keyword(s):  
Surface Characterization ◽  
Solid Phase ◽  
Degradation Products ◽  
Morphological Changes ◽  
Aqueous Solubility ◽  
Radiation Chemistry ◽  
Dark Field ◽  
Gas Chromatography Mass Spectrometry ◽  
Low Oxygen ◽  
Oxygen Conditions

Polyethylene (PE) is an intensely utilized polymer, which has consequently led to it becoming a common environmental contaminant. PE and other plastic waste are known to be highly persistent in surface waters; however, chemical and physical changes do take place over time, dependent mostly on highly variable natural conditions, such as oxygen (O2) availability. Gamma radiation was used to generate reactive oxygen species, namely hydroxyl radicals, in initially aerated aqueous solutions to simulate the natural weathering of microplastics in waters where there are fluctuations and often depletions in dissolved O2. The headspace of the irradiated PE-containing solutions was probed for the formation of degradation products using solid-phase microextraction (SPME) fibers in combination with gas chromatography mass spectrometry (GCMS). The major species detected were n-dodecane, with trace levels of tridecane, 2-dodecanone, and hexadecane, which were believed to be predominately adsorbed in the PE microplastics in excess of their aqueous solubility limits. Surface characterization by Raman spectroscopy and light and dark field microscopy indicated no change in the chemical composition of the irradiated PE microplastics under low O2 to anaerobic conditions. However, morphological changes were observed, indicating radical combination reactions.

scholarly journals Two 2[5H]-Furanones as Possible Signaling Molecules in Lactobacillus helveticus

2006 ◽  
Vol 72 (9) ◽  
pp. 6053-6061 ◽  
Author(s):  
Maurice Ndagijimana ◽  
Melania Vallicelli ◽  
P. Sandro Cocconcelli ◽  
Fabrizio Cappa ◽  
Francesca Patrignani ◽  
...  
Keyword(s):  
Solid Phase ◽  
Morphological Changes ◽  
Starter Culture ◽  
Sodium Dodecyl ◽  
Signaling Molecules ◽  
Lactobacillus Helveticus ◽  
Gas Chromatography Mass Spectrometry ◽  
Gram Negative Bacteria ◽  
Cheese Ripening ◽  
Autolytic Activity

ABSTRACT Two 2[5H]-furanones, in association with medium-chain fatty acids, were released in whey by Lactobacillus helveticus exposed to oxidative and heat stresses. This species plays an important role in cheese technology, particularly for Swiss-type cheeses and Grana cheese. Moreover, it significantly contributes to cheese ripening by means of an early autolysis and the release of enzymes during processing. Experimental evidence of the involvement of the two 2[5H]-furanones, detected by a gas chromatography-mass spectrometry/solid-phase microextraction technique, in the autolysis phenomenon has been obtained. Zymograms performed by using renaturing sodium dodecyl sulfate-polyacrylamide gels were used to detect the bioactivity of the supernatants containing the two furanones on fresh cells of the same strain. In addition to bands corresponding to known autolysins, new autolysins were detected concomitant with the exposure of Lactobacillus helveticus to the supernatants, which can be regarded as conditioned media (CM), and to a commercial furanone, 5-ethyl-3-hydroxy-4-methyl-2[5H]-furanone (HEMFi), having spectral data similar to those of the newly described 2[5H]-furanones. Morphological changes were observed when fresh cells were exposed to CM containing the two 2[5H]-furanones and HEMFi. The two furanones produced by Lactobacillus helveticus, which met a number of criteria to be included in cell-cell signaling molecules, have a presumptive molecular mass lower than those of already known 3[2H]-furanones having an autolytic activity and being produced by gram-negative bacteria. Moreover, they present a different chemical structure with respect to the furanones already identified as products of Lactococcus lactis subsp. cremoris or to those identified in some cheeses with Lactobacillus helveticus as a starter culture.

Effect of Fe2+ on Ascorbic Acid - Methionine Pattern is Formed by the Reaction of Aroma Compounds

2013 ◽  
Vol 781-784 ◽  
pp. 591-595
Author(s):  
Di Liu ◽  
Yu Shao ◽  
Xiao Hong Yang
Keyword(s):  
Solid Phase Microextraction ◽  
Solid Phase ◽  
Degradation Products ◽  
Model Reaction ◽  
Flavor Compounds ◽  
Gas Chromatography Mass Spectrometry ◽  
Reaction Products ◽  
Competitive Reaction ◽  
Sulfur Containing ◽  
Sulfur Containing Compounds

By solid phase microextraction - Gas Chromatography - mass spectrometry (SPME-GC-MS) technique against acid and methionine bad blood (ASA-Met) model of the reaction products were identified, studied the effect of Fe2+ on the formation of flavor compounds in the model reaction. 27 flavour compounds of furan, pyrazine, thiophene, sulfur and other compounds, were identified, of which, sulfur-containing compounds such as aliphatic cyclic sulfides, sulfide, pyrazine is the main flavor components. Fe2+ was added to the model in the system, on one hand the about adding some sulfur compounds yield, pyrazine compounds significantly increase; on the other hand, Thiophenes significantly reduced compounds or even disappear. This shows that in the model reaction, Fe2+ promotes the thermal degradation of Met, at the same time, suggesting that Fe2+ as oxidant to promote NH3, NH3 and H2S to generate competitive reaction and ASA degradation products formed compounds containing nitrogen, resulting in reduced Thiophenes compounds yield.

scholarly journals Identification of Potential Extractables and Leachables in Cosmetic Plastic Packaging by Microchambers-Thermal Extraction and Pyrolysis-Gas Chromatography-Mass Spectrometry

Molecules ◽  
2020 ◽  
Vol 25 (9) ◽  
pp. 2115
Author(s):  
Pauline Murat ◽  
Sowmya Harohalli Puttaswamy ◽  
Pierre-Jacques Ferret ◽  
Sylvie Coslédan ◽  
Valérie Simon
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Solid Phase ◽  
Degradation Products ◽  
Gas Chromatography Mass Spectrometry ◽  
Pyrolysis Gas ◽  
Plastic Packaging ◽  
Chromatography Mass Spectrometry ◽  
Styrene Acrylonitrile ◽  
Materials Used

Most container–content interaction studies are carried out through migration tests on end products or simulants involving generally toxic solvents. This study was conducted with the aim of identifying potential leachables from materials used in cosmetic plastic packaging by using two approaches based on solvent-free extraction, i.e., solid-phase microextraction sampling and pyrolyzer/thermal desorption coupled with gas chromatography mass spectrometry. Volatile and semi-volatile intentionally and non-intentionally added substances were detected in seven packaging samples made of polypropylene, polyethylene, and styrene-acrylonitrile copolymer. Thirty-five compounds related to the polymers industry or packaging industry were identified, among them phthalates, alkanes, styrene, and cyanide derivates including degradation products, impurities, additives, plasticizers, and monomers. All except eight belong to the Cramer class I. These thermodesorption techniques are complementary to those used for migration tests.

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