Volatile Decomposition Products Research Articles

Thermal and metal‐catalyzed decomposition of methyl linolenate hydroperoxides

AbstractMuch work has been reported on the volatile oxidative products of fats and their impact on flavor deterioration, cellular damage and the decrease in safety of fatcontaining foods. However, relatively little information is available on the mechanism of hydroperoxide decomposition. Pure methyl linolenate hydroperoxides were decomposed thermally at 150 C and catalytically with ferric chloride‐ascorbic acid at room temperature. The volatile decomposition products were collected on porous polymer (Tenax) traps and concentrated by gel permeation chromatography. The total volatile products showed significant differences in composition by capillary gas chromatography‐mass spectrometry (GC‐MS). Thermal decomposition produced much more methyl octanoate (60.1%) and less 2,4‐heptadienal (0.5%) than catalytic decomposition (13.2 and 60.8%, respectively). The volatiles from the ferric chloride‐ascorbic acid system also contained unique products tentatively identified by GC‐MS as isomers of chloromethyl butene. These results may have important implications in evaluating precursors of flavor deterioration in vegetable oils containing linolenate and in understanding better the biological significance of lipid peroxidation.

Dynamic headspace capillary gas chromatographic analysis of soybean oil volatiles

AbstractTo develop new knowledge on preventing or eliminating the formation of undesirable flavors in soybean oil, we analyzed quantitatively the major volatile products in samples that were oxidized during storage in the dark at ambient conditions. The volatiles formed were recovered and separated by dynamic headspace capillary gas chromatography. The effect of sampling temperatures was investigated by heating the sample, sweeping the volatiles with helium and trapping and desorbing them from a porous polymer Tenax trap. The volatiles were flushed from the trap onto a fused silica capillary column with a bonded mixed dimethyldiphenyl siloxane phase. At peroxide values between 2 and 13, the major volatile products found were acrolein, pentene, pentane, 1‐penten‐3‐ol, pentanal, hexanal, 2‐hexenal, 2‐heptenal, 2,4‐heptadienal, 2‐octenal and 2,4‐decadienal. The profile of volatiles was significantly affected by the sampling temperature used and by the presence or absence of citric acid in the oils before storage. The relative amounts of volatile thermal decomposition products of linolenate and linoleate hydroperoxides, such as 2,4‐heptadienal and 2,4‐decadienal, increased significantly when samples were heated above 90 C. Dynamic headspace gas chromatography made it possible to analyze the volatiles in samples heated to 60 and 90 C. These volatiles may be representative of those present in oils at time of tasting.

Volatile Decomposition Products in the Air Oxidation of Triolein and Trilinolein

Purified triolein (TO) and trilinolein (TL) were oxidized by introducing oxygen at 75°C into the same apparatus as employed previously. In each oxidized sample, volatile decomposition products, especially aldehydes (as the origin of rancid odor), were identified by gas chromatography mass spectrometry, comparing with the products from the corresponding fatty acid methyl-ester.It was observed that heptane and octane as hydrocarbons, 1-heptanol and 1-octanol as alcohols, and heptanal, octanal, nonanal, decanal, 2-decenal and 2-undecenal as aldehydes were formed from TO, while pentane as a hydrocarbon and hexanal, heptanal, 2-heptenal, 2-octenal and 2, 4-decadienal as aldehydes were obtained from TL. The precursors of those products, the monohydroperoxides (MHP), and cleavage positions were discussed in comparison with those of methyl-esters. The formation mechanism of the above products could be explained except for heptanal from TO and 2-heptenal from TL (these were assumed to be secondary oxidation products). Further, 3-nonenal (or 2-nonenal), which was expected to be formed from TL, was not found. In the oxidation of TL, formation of 11-MHP was found in addition to 9-MHP and 13-MHP.The relative percentages of peak area were calculated from a gas chromatogram of volatiles derived from TO, and aldehydes accounted for about 67% of the area. The odor of octanal was the strongest. In the oxidation of TL, 2, 4-decadienal accounted for 42% of the total area, and the odor of hexanal was the strongest at each stage of oxidation.

Thermal decomposition of dicitratoborates

The thermal decompositions of dicitratoborates M1[B(C6H6O7)2]·nH2O (n=0–2, M1=Rb, K, Li, NH4) and M11[B(C6H6O7)2]2·8H2O (M11=Co, Ni, Mn, Cu, Zn, Cd) were investigated by means of TG, DTA and DTG methods. It was found that these thermal decompositions involve three successive stages: dehydration, the endothermal decomposition of the ligand, and oxidation of the residual organic component. The volatile products of decomposition in each stage were detected by means of gas chromatography. The method of TG-curve transformation into the curvedm/d T vs.m, wherem is the loss of weight at each moment of time, was used for a more detailed study of dehydration. The optimal conditions for TG-curve modification were found.

4528011 Immobilization of radwastes in glass containers and products formed thereby

This invention relates to the immobilization of toxic materials, e.g., radioactive materials, in glass for extremely long periods of time. Toxic materials, such as radioactive wastes, which may be in the form of liquids, or solids dissolved or dispersed in liquids or gases, are deposited in a glass container which is heated to evaporate off non-radioactive volatile materials, if present; to decompose salts, such as nitrates, if any, and to drive off volatile non-radioactive decomposition products, and then to collapse the walls of said container on said radwaste and seal the container and immobilize the contained radwaste, and then burying the resulting product underground or at sea. In another embodiment, the glass container also contains glass particles, e.g., spheres or granules, on which the radwaste solids are deposited. In other embodiments, the glass container can be made of porous glass or non-porous glass, and/or the contained glass particles can be made of porous or non-porous glass or mixtures of porous or non-porous glass, and/or the glass container can be open at one end and closed at the other or open at both ends, and/or the glass container can be closed at one end with a porous or non-porous closure and open at the other end or closed at the other end with a porous closure. When a porous glass container and/or porous glass particles are used, the radwaste deposits within the pores of the glass which are closed during the subsequent heating step after non-radioactive volatiles have been driven off and prior to sealing the container. There results a substantially impervious glass article in which the radwaste is entrapped and which is highly resistant to leaching action. The products resulting from the use of porous glass, as the container, contents, or both, can be used as sources of radioactivity for a variety of applications in medicine, sterilization, food preservation and any other application where radiation can be beneficially employed.

Effects of antioxidants, methyl silicone and hydrogenation on room odor of soybean cooking oils

AbstractRoom odor characteristics produced by heated soybean oil (SBO) and soybean oils hydrogenated with copper (CuHSBO) and nickel (NiHSBO) catalysts were evaluated by a trained panel. Oils were intermittently heated to 190 C for total heating periods of 5, 15 and 30 hr. Oil additives investigated included methyl silicone (MS), tertiary butylhydroquinone (TBHQ) and a polymeric antioxidant in various combinations with citric acid (CA). In room odor tests directly comparing SBO, CuHSBO and NiHSBO, panelists rated the hydrogenated oils as having significantly less odor intensity than the SBO. The combination of CA+MS had the greatest effect in lowering odor intensity of the heated oils, followed by the mixture of CA+MS+TBHQ. The low odor intensity of the MS‐treated oils remained fairly constant throughout the tests, while the higher intensity associated with all the other additive‐treated oils decreased with increasing heating times, possibly as the result of formation of more volatile decomposition products in the initial heating stages. Methyl silicone had the strongest effect of any additive in decreasing objectionable room odors in the oils. Partially hydrogenated SBO treated with up to 5 ppm of MS produced cooking oils with low room odor intensity and low color development during prolonged heating.

Experimental study of laser induced decomposition based processing of a brittle plastic, CR-39 (allyl diglycol carbonate)

A cw CO2 laser, coupled with an astigmatism free beam focussing mirrors arrangement is used for processing a brittle plastic, CR-39 without producing cracks, vents or chips. The processing is based on the formation of volatile products of laser-induced decomposition in the plastic. Threshold fluence for the decomposition (found to be independent of the power density and beam residence time) in CR-39 atλ=10.6μm is determined to be 25 J cm−2 and the decomposition threshold power density for cw irradiation 2.1±0.5 W cm−2. The depth and width of the tapered laser processed region are observed to increase with power density and beam residence time. The widths attain a steady state value of ∼ 1 mm at beam residence time above 65 ms, for a fixed power density (2.5×104 W cm−2) and sheet thickness (250 μm). Taper angle of the edges decreases with increasing power density and/or beam residence time. The heat affected zone (measured in crossed polarisers) around the processed region is found to extend with increasing beam residence time but remains unaffected on changing power density. The results are discussed in terms of the optical and thermophysical properties of CR-39 and the parameters of the interacting laser beam.

Analysis of autoxidized fats by gas chromatography‐mass spectrometry. IX. Homolytic vs. Heterolytic cleavage of primary and secondary oxidation products

AbstractTo elucidate the genesis of volatile lipid oxidation products, thermal homolytic and acid heterolytic decomposition processes were compared. Secondary oxidation products were decomposed thermally (200 C), and the volatiles formed were identified by capillary gas chromatography‐mass spectrometry (GC‐MS). Oxidation products also were decomposed in the presence of HCl‐methanol, and the resulting dimethyl acetals were identified by GC‐MS. The volatile thermal decomposition products were those expected by homolytic β‐scission on both sides of the hydroperoxide group. No dialdehydes were identified under our thermal decomposition conditions. In contrast, the acetals formed by acid decomposition were those expected by selective heterolytic scission between the hydroperoxide group and the allylic double bond. Dialdehydes identified from acid decomposition of cyclic peroxides and dihydroperoxides included malonaldehyde and 2,4‐hexadienedial.

Toxicity of polymethylmethacrylate thermodegradation products.

Polymethylmethacrylate was thermally degraded in air at 300 degrees C and the volatile decomposition products studied with gas chromatography-mass spectrometry. The main product was monomeric methacrylate, although many other compounds existed among the products. Electron spin resonance spectroscopy revealed the presence of free radicals. Wistar rats were exposed to the fumes of the plastic (300 degrees C) and their lungs and brain studied for biochemical effects. In the lung, the activity of 7-ethoxycoumarin O-deethylase decreased and an initial inhibition of glutathione peroxidase and superoxide dismutase was observed. The contents of reduced nonprotein sulfhydryl groups were decreased in the lung and brain. The exposures enhanced the activities of acetylcholine esterase, creatine kinase and NADPH-diaphorase in the brain. Scanning electron microscopy of the exposed lungs showed disorganization of ciliated cells, and the epithelial serous cells (Clara cells) were damaged.

STRUCTURAL TYPES IN PETROLEUM ASPHALTENES AS DEDUCED FROM PYROLYSIS/GAS CHROMATOGRAPHY/MASS SPECTROMETRY

ABSTRACT An integrated technique has been developed for the study of the thermal chemistry of petroleum fractions—particularly the asphaltenes. The procedure involves the integrated use of a pyroprobe/gas chroma-tographic/mass spectrometric technique which offers information about the structuraI-types and distribution within the volatile products from the thermal decomposition of asphaltenes. The technique offers itself as an attractive on-line analytical method for the study of structural types that occur in asphaltenes as well as a technique for studying the parameters that can influence asphaltene decomposition. The concept of deducing “average” structures of asphaltenes is briefly discussed in terms of the observance of the lower molecular weight species in the volatile products of the thermal decomposition.

Photosensitized oxidation of methyl linoleate monohydroperoxides: Hydroperoxy cyclic peroxides, dihydroperoxides, keto esters and volatile thermal decomposition products

AbstractPrevious studies of lipid secondary oxidation products have been extended to 6‐membered hydroperoxy cyclic peroxides from the singlet oxygenation of a mixture of 9‐ and 13‐hydroperoxides from autoxidized methyl linoleate. The oxidation product was fractionated by silicic acid chromatography with diethyl ether/hexane mixtures, and selected fractions were separated by polar phase high performance liquid chromatography. Products characterized by thin layer chromatography, gas liquid chromatography, ultraviolet, infrared, nuclear magnetic resonance and mass spectrometry included: 6‐membered cyclic peroxides (13‐hydroperoxy‐9,12‐epidioxy‐10‐ and 9‐hydroperoxy‐10,13‐epidioxy‐11‐octadecenoates), dihydroperoxides (8,13‐ and 9,14‐dihydroperoxyoctadecadienoates) and keto dienes (9‐ and 13‐oxooctadecadienoates). The 6‐membered hydroperoxy cyclic peroxides are apparently formed by 1,4‐addition of singlet oxygen to 9‐ and 13‐hydroperoxides withtrans, trans‐conjugated diene systems. Thermal decomposition of the 6‐membered hydroperoxy cyclic peroxides at 200 C produced methyl 9‐oxononanoate and hexanal as the major volatiles. Other volatiles included 2‐pentylfuran, pentane, 4‐oxo‐2‐nonenal, methyl furanoctanoate and methyl 9,12‐dioxo‐10‐dodecenoate.

Chemical reactions involved in the deep‐ fat frying of foods: IX. Identification of the volatile decomposition products of triolein

AbstractThe acidic and nonacidic volatile decomposition products (VDP) pro‐duced by pure triolein maintained at 185 C with periodic injection of steam were collected, fractionated and identified. A total of 93 compounds were positively or tentatively identified. A number of the compounds found were identified for the first time in fats or oil VDP. Among these newly identified compounds are: unsaturated acids, keto‐substituted unsaturated acids, ω‐enals, unsaturated esters and an unsaturated γ‐lactone.

Analysis of autoxidized fats by gas chromatography‐mass spectrometry: VIII. Volatile thermal decomposition products of hydroperoxy cyclic peroxides

AbstractSecondary oxidation products are important sources of volatiles because of their susceptibility to further decomposition. Volatiles from the thermal decomposition of hydroperoxy cyclic peroxides have been identified by capillary gas chromatography followed by mass spectrometry (GC‐MS). By using a saturated hydroperoxy cyclic peroxide as a synthetic model, the thermal decomposition pathways have been elucidated. Main cleavage occurs between the peroxide ring and the carbon‐bearing hydroperoxide group. Volatiles produced were generally similar to those from corresponding monohydroperoxides. New volatiles identified included methyl furan octanoate, methyl ketones, and conjugated diunsaturated aldehyde esters. The general fragmentation observed between the peroxide ring and the hydroperoxide‐bearing carbons is sufficiently predictable that it can be used as a tool for the structural characterization of hydroperoxy cyclic peroxides. Hydroperoxy cyclic peroxides from autoxidized and photosensitized oxidized methyl linolenate are suggested as important precursors of volatiles that may affect flavor quality of lipid‐containing foods.

Mechanism of action of pyrogenic silica as a smoke suppressant for polystyrene

The kinetic laws governing the forced burning of polystyrene-pyrogenic silica composites suggested formation of a surface “skin”; direct thermomechanical measurements were subsequently made of rates and extents of skin formation as a function of the type and loading of silica present; investigations were carried out on the effects of composition of the surrounding atmosphere, heating rate and degree of physical contact between the polymer and the additive on the amount of carbonaceous residue formed during thermal decomposition of the polymeric composites; and measurements were made of the influence of oxygen concentration on the extent of fuel retention when the composites burn. Silanol groups on the surface of the silica appear to react chemically with free radical species formed during the oxidative breakdown of polystyrene; this interaction results in the production of a skin, consisting of a cross-linked polymer structure with silica particles embedded in it and preventing the escape of the volatile decomposition products of the polymer which would otherwise lead to smoke formation. A parameter has been defined, the adsorption capacity, which is of crucial importance in the control of smoke generation, and a model has been devised which accounts for many of the experimental correlations found.

Effect of Heating Temperature and Time on the Volatile Oxidative Decomposition of Linolenate

ABSTRACTEthyl linolenate, was thermally oxidized at 70°C, 180°C, 250°C in a closed system in the presence of atmospheric oxygen. On the basis of the peroxide curve obtained at each of the three temperatures, three heating times were chosen for the analysis of the volatile decomposition products. These products were identified by gas chromatography‐mass spectrometry. The qualitative pattern of the volatile decomposition products was the same for all treatments. Nine of the products were consistent with compounds predicted from cleavage of the conjugated linolenate hydroperoxides, with the C9 oxo‐ester and the C8 ethyl ester produced in the largest amounts. Other predicted products were not detected and were hypothesized to undergo further degradations. Although the major effect of temperature was found to be a quantitative one, it was difficult to relate the amounts of oxidation products directly to a temperature‐ dependent preferential hydroperoxide scission.

Photosensitized oxidation of methyl linoleate: Secondary and volatile thermal decomposition products.

Studies of photosensitized oxidation of methyl linoleate show that the greater relative concentration of 9- and 13-hydroperoxides than 10- and 12-hydroperoxides is characteristic of singlet oxygenation and not due to either simultaneous autoxidation or type 1 photosensitized oxidation. Cyclization of the internal 10- and 12-hydroperoxides accounts for their lower relative concentrations. Secondary products separated by silicic acid and high pressure liquid chromatography were characterized spectrally (IR, UV,(1)H-NMR,(13)C-NMR, GC-MS). Major secondary products included diastereomeric pairs of 13-hydroperoxy-10,12-epidioxy-trans-8-octadecenote (I and III) and 9-hydroperoxy-10,12-epidioxy-trans-13-octadecenoate (II and IV); minor secondary products included hydroperoxy oxy genated and epoxy esters. Thermal decomposition of the hydroperoxy cyclic peroxides produced hexanal and methyl 10-oxo-8-decenoate as major volatiles from I and III and methyl 9-oxo-nonanoate and 2-heptenal from II and IV. Hydroperoxy cyclic peroxides may be important sources of volatile decomposition products of photooxidized fats.

Analysis of autoxidized fats by gas chromatography‐mass spectrometry: VII. Volatile thermal decomposition products of pure hydroperoxides from autoxidized and photosensitized oxidized methyl oleate, linoleate and linolenate

AbstractTo clarify the sources of undesirable flavors, pure hydroperoxides from autoxidized and photosensitized oxidized fatty esters were thermally decomposed in the injector port of a gas chromatograph‐mass spectrometer system. Major volatile products were identified from the hydroperoxides of methyl oleate, linoleate and linolenate. Although the hydroperoxides from autoxidized esters are isomerically different in position and concentration than those from photosensitized oxidized esters, the same major volatile products were formed but in different relative amounts. Distinguishing volatiles were, however, produced from each type of hydroperoxide. The 9‐ and 10‐hydroperoxides of photosensitized oxidized methyl oleate were thermally isomerized in the injector port into a mixture of 8‐, 9‐, 10‐ and 11‐hydroperoxides similar to that of autoxidized methyl oleate. Under the same conditions, the hydroperoxides from autoxidized linoleate and linolenate did not undergo significant interconversion with those from the corresponding photosensitized oxidized esters. The compositions of the major volatile decomposition products are explained by the classical scheme involving carboncarbon scission on either side of alkoxy radical intermediates. Secondary reactions of hydroperoxides are also postulated, and the hydroperoxy cyclic peroxides from methyl linoleate (photosensitized oxidized) and methyl linolenate (both autoxidized and photosensitized oxidized) are suggested as important precursors of volatiles.

Thermal Degradation of Glutamate Polymers

Abstract Thermal properties of precipitated samples and films of poly-γ-benzyl-L-glutamate (PBG) and poly-L-glutamic acid (PGA) have been studied using TGA, DSC, and pyrolysis. The PBG film was identified as that described by McKinnon and Tobolsky as “form C” (“film A” of Uematsu et al.) using IR, dielectric relaxation, and DSC data. The PGA film is α-helical (IR) and was further characterized by dielectric relaxation measurements. With the exception of water loss at ∼110° from PGA, TGA and DSC measurements reveal only incomplete endotherms corresponding to decomposition. Volatile decomposition products were trapped and identified using combined GC/IR and GC/MS techniques. Identified products were as follows: from PGB–CO2, NH3, H2O, toluene, benzaldehyde, benzyl alcohol, and benzoic acid; from PGA–CO2, NH3, CH3OH, acetone, and H2O. Only minor differences were noted in GC traces of the total volatile decomposition products in air or in nitrogen streams. No evidence for retained solvent in cast films was ob...

Correlation between the content of volatile matter and mineral matter in hard coals

If coal is heated to 900 °C, in the absence of air the organic coal substance and the associated mineral matter are decomposed. The analytically determined volatile-matter yield includes the volatile decomposition products of both the coal substance and the minerals. The correlation between mineral matter and ash and the volatile-matter yield is derived, and its accuracy shown by evaluation of test results. Methods are proposed for calculating a value for the volatile matter dmmf for coals of a particular mine. Various formulae for calculating the volatile matter of coals to dmmf basis are critically considered. Finally, a generally applicable equation for calculating dmmf volatile matter is derived which can be used for classification.

Thermal reactions of Lead(IV) chloride complexes in the solid state. Part I. Thermolysis of hexachloroplumbates and molecular complexes of PbCl 4 with pyridine, quinoline and isoquinoline

The thermal decomposition of hexachloroplumbic acid salts and of PbCl 4 complexes of pyridine, quinoline and isoquinoline has been investigated by thermogravimetry and differential thermal analysis. The decomposition has also been studied isothermally in a device allowing the analysis of both solid and volatile decomposition products. The products of all thermal reactions comprised PbCl 2, chlorine, appropriate aromatic bases, their hydrochlorides, chlorinated bases, and other compounds. The influence of sample weight, temperature, rate of removal of volatile products and the effect of certain substances on the course of the thermolysis has also been studied.