Exclusion Of Atmospheric Oxygen Research Articles

Negative-ion field desorption revitalized by using liquid injection field desorption/ionization-mass spectrometry on recent instrumentation

Field ionization (FI), field desorption (FD), and liquid injection field desorption/ionization (LIFDI) provide soft positive ionization of gaseous (FI) or condensed phase analytes (FD and LIFDI). In contrast to the well-established positive-ion mode, negative-ion FI or FD have remained rare exceptions. LIFDI provides sample deposition under inert conditions, i.e., the exclusion of atmospheric oxygen and water. Thus, negative-ion LIFDI could potentially be applied to highly sensitive anionic compounds like catalytically active transition metal complexes. This work explores the potential of negative-ion mode using modern mass spectrometers in combination with an LIFDI source and presents first results of the application of negative-ion LIFDI-MS. Experiments were performed on two orthogonal-acceleration time-of-flight (oaTOF) instruments, a JEOL AccuTOF GCx and a Waters Micromass Q-TOF Premier equipped with LIFDI sources from Linden CMS. The examples presented include four ionic liquids (ILs), i.e., N-butyl-3-methylpyridinium dicyanamide, 1-butyl-3-methylimidazolium tricyanomethide, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, and trihexyl(tetradecyl)phosphonium tris(pentafluoroethyl)trifluorophosphate), 3-(trifluoromethyl)-phenol, dichloromethane, iodine, polyethylene glycol diacid, perfluorononanoic acid, anionic surfactants, a tetraphosphazene silanol-silanolate, and two bis(catecholato)silanes. Volatile samples were delivered as vapors via the sample transfer capillary of the LIFDI probe or via a reservoir inlet. Condensed phase samples were applied to the emitter as dilute solutions via the sample transfer capillary. The compounds either yielded ions corresponding to their intact anions, A−, or the [M–H]− species formed upon deprotonation. This study describes the instrumental setups and the operational parameters for robust operation along with a discussion of the negative-ion LIFDI spectra of a variety of compounds.

From the discovery of field ionization to field desorption and liquid injection field desorption/ionization-mass spectrometry-A journey from principles and applications to a glimpse into the future.

The discovery of the ionizing effect of strong electric fields in the order of volts per Ångstrom in the early 1950s eventually led to the development of field ionization-mass spectrometry (FI-MS). Due to the very low ion currents, and thus, limited by the instrumentation of the 1960s, it took some time for the, by then, new technique to become adopted for analytical applications. In FI-MS, volatile or at least vaporizable samples mainly deliver molecular ions, and consequently, mass spectra showing no or at least minor numbers of fragment ion signals. The next major breakthrough was achieved by overcoming the need to evaporate the analyte prior to ionization. This was accomplished in the early 1970s by simply depositing the samples onto the field emitter and led to field desorption-mass spectrometry (FD-MS). With FD-MS, a desorption ionization method had become available that paved the road to the mass spectral analysis of larger molecules of low to high polarity and even of organic salts. In FD-MS, all of these analytes deliver spectra with no or at least few fragment ion peaks. The last milestone was the development of liquid injection field desorption/ionization (LIFDI) in the early 2000s that allows for sample deposition under the exclusion of atmospheric oxygen and water. In addition to sampling under inert conditions, LIFDI also enables more robust and quicker operation than classical FI-MS and FD-MS procedures. The development and applications of FI, FD, and LIFDI had mutual interference with the mass analyzers that were used in combination with these methods. Vice versa, the demand for using these techniques on other than magnetic sector instruments has effectuated their adaptation to different types of modern mass analyzers. The journey started with magnetic sector instruments, almost skipped quadrupole analyzers, encompassed Fourier transform ion cyclotron resonance (FT-ICR) and orthogonal acceleration time-of-flight (oaTOF) analyzers, and finally arrived at Orbitraps. Even interfaces for continuous-flow LIFDI have been realized. Even though being niche techniques to some degree, one may be confident that FI, FD, and LIFDI have a promising future ahead of them. This Account takes you on the journey from principles and applications of the title methods to a glimpse into the future.

A versatile and rapid coating method via a combination of plasma polymerization and surface‐initiated SET‐LRP for the fabrication of low‐fouling surfaces

In this work, we demonstrate the potential of surface-initiated single electron transfer living radical polymerization for surface modification applications that confer low-fouling properties. The versatility of the technique, which can be applied to a wide variety of substrates, has been displayed by the successful grafting of a range of monomers after immobilizing a bromine initiator on the surface via plasma polymerization. The thickness of the grafted surfaces can be controlled through variation of reaction parameters such as monomer concentration, reaction time, and the ratio between catalyst and ligand. Furthermore, the low-fouling properties of the resulting surfaces were demonstrated against fully concentrated serum proteins and adhesive fibroblast cells, via grafting of N-hydroxyethyl acrylamide (N-HEA) or [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA). This rapid and versatile coating technique, which has the ability to be applied to a wide range of substrates, can be performed in aqueous conditions without the exclusion of atmospheric oxygen, and shows excellent potential for the surface modification of biomaterial surfaces that require low-fouling properties. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2527–2536

Amide Bond Formation Using an Air‐Stable Source of AlMe3.

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Tests for the depolymerization of polyacrylamides as a potential source of acrylamide in heated foods.

This study was conducted to test the possibility that polyacrylamides used in agriculture may contribute to acrylamide formation in heated foods by thermal depolymerization. Two samples of polyacrylamide with low molecular weights of 1.5 and 10 kDa were used to test for in-chain and end-chain depolymerization. They were added as aqueous solutions to filter paper for heating in a drying/dry environment and added to a cooking oil for heating in a fatty environment. The heating conditions were 175 degrees C for 15 and 30 min, respectively. Both regimens were tested in the absence and presence of the redox-active metal ions Fe(III) and Cu(II), and all tests were conducted without the exclusion of atmospheric oxygen. There was no evidence of any significant depolymerization of polyacrylamide to free acrylamide monomer, <0.04%. In fact, residual levels of acrylamide present already in the low molecular weight polymers were seen to fall by 50-80% on heating. Consequently, it is concluded that even if polyacrylamides were to contaminate agricultural crops and foods derived therefrom (which itself is an unproven suggestion), there is no evidence that the polymers would depolymerize on heating of the food to form acrylamide in any significant amount.

Peat as a potential analogue for the long-term evolution in landfills

A survey of the existing studies on peat and its decomposition processes is presented with the aim to characterise the long-term behaviour of peat accumulating systems. The chemical and physical characteristics of peat together with its accumulation and decay processes have been analysed. Peat is an acidic mixture of dead and decomposed, mainly vegetable, matter formed in boggy areas; it is the youngest and least altered component of the combustible rocks and is characterised by the lowest content of fixed carbon and the highest content of volatile constituents. Peat is formed by degeneration processes under exclusion of atmospheric oxygen by the action of water; the speed of formation depends upon the climatic and environmental conditions. In most peatlands two layers can be characterised: the aerobic acrotelm and the anaerobic catotelm, their relative importance being controlled mainly by the position of the water table. In the acrotelm the aerobic processes are responsible for the loss of up to 90% of the original mass. Degeneration in the acidic and anaerobic catotelm is still imperfectly characterised even though the catotelm is the real site of peat accumulation. Most of the recent literature considers peat as composed of easily degradable compounds, e.g. polysaccharides, and recalcitrant matter (lignin and complex aromatics). The long-term destiny of peat has not been sufficiently characterised: although in a large majority of cases it seems probable that peat decomposes completely (even though slowly) provided that it is given a sufficiently long residence time in the catotelm, some cases can still be interpreted as examples of simple accumulation. The rates of influx of oxygen and hence the degradation of organic matter into both saturated and partially saturated peat have been estimated. The depletion rate is about 4500 g m −2 year −1 for partially saturated peat. The average depletion rate of the peat for this case will then be such that it will take on the order of 5 to 50 years to degrade half of the organics in a 10 cm partially saturated layer. For the water-saturated case the depletion rate varies between 8 and 12 g m −2 year −1, which is considerably lower than in the partially saturated region. The models used to analyse the field and laboratory data on generation, diffusion and emission of methane and carbon dioxide indicate that laboratory data and field observations agree reasonably well. It is suggested that peat-accumulating ecosystems may be valuable natural analogues for the study of the long-term destiny of industrial and municipal solid wastes. Accurate studies of active mires together with an ad hoc review of the existing literature give valuable insights in this problem. Peatlands might then be considered as organic waste deposition experiments lasting up to several thousands years.

Column leach study 1: Heavy metal dissolution characteristics from selected copper mine tailings

Mill tailings collected from seven copper mine mill sites in the western United States were examined by researchers from the Bureau of Mines for metal dissolution properties using a column leaching procedure involving a formulated “western rain” leachant. Studies investigated effects of height of waste column, wet/dry cycle, and maximum leachability of waste tailings. Further studies on selected samples indicated that treatment of acid-producing tailings with chemical stabilizers such as phosphates and carbonates did not greatly affect mobilization of heavy metals leached from these samples. Increased metal mobilization from unsaturated columns was often associated with decreased leachate pH and increased sulfate production, but was not observed in all samples examined. Results from these and other studies suggest that the driving force for metal dissolution and/or acid formation in unsaturated mine tailings is the oxidation of metal sulfides by atmospheric oxygen. The maintenance of tailings at or near saturation or the exclusion of atmospheric oxygen appear to produce leachates of nearly constant to slowly decreasing metal concentrations with each subsequent leaching.

Influence of ionizing radiation on the fatty acid composition of herring fillets

The effect of γ-irradiation (absorbed dose: 50 kGy, dose-rate: 2.9 kGy h ) on the distribution of fatty acid components in herring fillets has been examined using high-resolution gas chromatographic methods. Radiolytic treatment at 0°C and exclusion of atmospheric oxygen caused no significant decrease in the relative amounts of the constituent saturated, monounsaturated and polyunsaturated fatty acid components. Specifically, eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6), which are of particularly physiological interest were not affected by γ-rays, even after additional storage of the irradiated material at 0°C for 4 weeks. Irradiation of oil extracted from herring fillets or of herring oil/water emulsions under aerobic conditions, however, destroyed eicosapentaenoic acid and docosahexaenoic acid significantly. The loss of radio-resistance—as compared to the radiation-induced processes in the fillets—is explained by the absence of proteins, which effectively protect the lipid components from radiolytic decomposition. It is concluded that the commercial radiation processing of herring at the recommended dose levels (1–2 kGy) should not reduce the content of unsaturated fatty acid components.

Reduction of radiation-induced vitamin E- and B1- losses by irradiation of foodstuffs at low temperature and by exclusion of atmospheric oxygen

The protective effect of low temperatures during irradiation on vitamin B1 and E levels in foods is not abolished by subsequent storage or heating. Egg powder irradiated at 1 Mrad in the presence of air and stored for 4 months at ambient temperature lost 68% of its thiamin content when irradiated at 20 degrees C, 33% when irradiated at -30 degrees C. Sunflower oil irradiated at 3 Mrad in the presence of air and subsequently heated for 1 hour at 180 degrees C lost 98% of its alpha-tocopherol content when irradiated at 20 degrees C, 65% when irradiated at -30 degrees C. Exclusion of atmospheric oxygen by packaging under nitrogen reduced the loss of alpha-tocopherol in irradiated (0.1 Mrad) rolled oats after 8 months of storage from 56 to 5% and the loss of thiamin from 86 to 26%. Vacuum packaging was equally effective during the first 3 months and somewhat less effective during the following 5 months. Packaging under carbon dioxide showed no advantage over packaging in air. Sensory evaluation of rolled oats, raw or cooked, 1 and 3 months after irradiation with 0.1 Mrad indicated no significant quality difference between unirradiated and irradiated samples packaged under nitrogen.

Synthese von 2H‐Isoindol‐4,7 ‐dionen durch photochemische Cycloaddition von 2,3‐Diphenyl‐2H‐azirin an 1,4‐Chinone. 38. Mitteilung über Photoreaktionen

Abstract2, 3‐Diphenyl‐2H‐azirine (1) reacts on irradiation with light of wavelength 290–350 nm with 1,4‐benzoquinones 3–6 or with 1,4‐naphthoquinones 7–9 forming the yellow to red coloured 1,3‐diphenyl‐2H‐isoindole‐4, 7‐diones 10–13 (33–43% yield) resp. 1, 3‐diphenyl‐2H‐benzo[f]isoindole‐4,9‐diones 14–16 (33–36% yield) (Scheme 1). The structures of these hitherto unknown products follow from the analytical and spectral data.The probable formation of the isoindole‐diones is depicted in Scheme 2. The intermediate benzonitrile‐benzylide (2), which most certainly arises, adds onto the unsubstituted C, C‐double bond of the quinones and not onto the C,O‐double bonds. On exclusion of atmospheric oxygen there results from 1 and 2‐methyl‐1, 4‐benzoquinone (4) a product (probably b) which hardly absorbs in the region 350–450 nm. The latter, with the agency of atmospheric oxygen (but not 4), is converted into 5‐methyl‐1, 3‐diphenyl‐2H‐isoindole‐4, 7‐dione (11). The relative slowness of this oxidation (see Fig. 2) enables an almost complete photochemical transformation of the azirine 1, which only weakly absorbs above 290 nm. Otherwise 11, which strongly absorbs above 290 nm, would hinder the photolysis of 1.

Alternating Current Polarographic Determination of Dissolved Oxygen in Gasoline

In view of the well known fact that dissolved oxygen plays a very important role in petroleum refinery, the present investigation was undertaken to establish a rapid and accurate method for the determination of dissolved oxygen in gasoline . In 1924 Heyrovsky first reported that dissolved oxygen is reduced at the dropping mercury electrode to produce two waves3) . The first wave results from reduction to hydrogen peroxide :O2+2H++2e→H2O2(acid medium)O2+H2O2+2e→HO2-+OH-(neutral or alkaline medium).The second wave corresponds to the reduction of the hydrogen peroxide either to water or hydroxyl ion, depending on the pH:H2O2+2erarr;2H2O(acid medium)HO2-→3OH-(alkaline medium).The diffusion currents are normally well-defined and show a linear dependence on oxygen concentration. However, three main difficulties are encountered in the application of a.c, polarography to the determination of oxygen in gasoline: the limited solubility of gasoline in aqueous or semi-aqueous electrolyte system, the exclusion of atmospheric oxygen in handling sample and the accurate calibration of calibration curve. The first difficulty was resolved by adopting a supporting electrolyte of sodium hydroxide in absolute alcohol and the second by the disign of a special polarographic cell. Two ways of accurate calibration were investigated: by using water of known dissolved oxygen content directly as a calibration standard, and by using air-saturated alcoholic electrolyte as a secondary standard, the dissolved oxygen content being determined polarographically using water as a primary standard .

Crosslinking of Latex Rubber

Abstract Most of the properties of rubber are consistent with those expected of a high- molecular-weight linear polymer of isoprene. However, there are some features of its behavior that are inexplicable on this basis. They must be the result of the presence of small amounts of structures other than the regular head-to-tail chain of isoprene units. Bloomfield, in the first fundamental study of the properties of rubber from freshly tapped latex, found that the tree does not continue to build indefinitely a linear polymer, but that branching reactions occur in a rested tree. These reactions eventually convert individual latex particles into substantially single molecules of enormous molecular weight. Bloomfield also observed that small amounts of oxygen are intimately associated with the hydrocarbon, even when it is isolated directly from the tree with careful exclusion of atmospheric oxygen. Craig, Juve, and Davidson have found less certain indications of the presence of carboxyl groups, which, if they are present in the rubber in concentrations even approaching the amount indicated by their results, must be on side chains.

Crosslinking of Latex Rubber

Abstract Most of the properties of rubber are consistent with those expected of a high- molecular-weight linear polymer of isoprene. However, there are some features of its behavior that are inexplicable on this basis. They must be the result of the presence of small amounts of structures other than the regular head-to-tail chain of isoprene units. Bloomfield, in the first fundamental study of the properties of rubber from freshly tapped latex, found that the tree does not continue to build indefinitely a linear polymer, but that branching reactions occur in a rested tree. These reactions eventually convert individual latex particles into substantially single molecules of enormous molecular weight. Bloomfield also observed that small amounts of oxygen are intimately associated with the hydrocarbon, even when it is isolated directly from the tree with careful exclusion of atmospheric oxygen. Craig, Juve, and Davidson have found less certain indications of the presence of carboxyl groups, which, if they are...

The antistreptococcal property of milk. II. The effects of anaerobiosis, reducing agents, thiamine, and other chemicals on lactenin action.

Lactenin is reversibly inactivated by the exclusion of atmospheric oxygen. It is also inactivated by the sulfur-containing reducing agents cysteine, glutathione, thioglycollic acid, and BAL. Group A streptococci which have been acted upon by lactenin have been killed, and not merely prevented from multiplying, since they cannot be revived by inactivating lactenin through the addition of a reducing agent. Thiamine in great excess inactivates lactenin. The mechanism by which it accomplishes this has not been discovered, but it suggests that the mode of action of lactenin may be to deny thiamine to the lactenin-sensitive cell. Lactenin sensitivity is not, however, related to a requirement for exogenous thiamine, nor does lactenin appear to function by binding environmental thiamine in a form unavailable to the sensitive cell.

The determination of the peroxide values of edible fats and oils: The iodimetric method

AbstractFactors which influence the determination of peroxide values by the iodimetric method have been investigated. These include dissolved oxygen and moisture in the reagent, time and temperature of reaction, and amount of fat taken. The necessity for adequate de‐aëration of the reagent before admixture with the fat had been demonstrated for this, as previously for the photometric ferrous salt method, but the ratio between the “aërobic” and “anaërobic” values is much smaller for the iodimetric than for the ferrous salt method. Alternative procedures for determination of iodimetric peroxide values are recommended by (a) a “cold” method involving standing at laboratory temperature for one hour, or (b) a rapid “hot” method involving heating at the boiling point of the solvent for two minutes.The increase in apparent peroxide value observed in earlier iodimetric procedures when the quantity of fat taken for the determination was reduced, has been shown to be due to an increasing error reuniting from further oxidation of the fat by dissolved oxygen during the determination, rather than to a decreasing error due to loss of iodine by re‐absorption. In both the procedures now recommended, exclusion of atmospheric oxygen is adequate and the results, within reasonable limits, are independent of the size of the sample of fat taken.