Mixture Of Sulfite Research Articles

Application of oxygen scavengers in gel electromembrane extraction: A green methodology for simultaneous determination of nitrate and nitrite in sausage samples.

The generation of oxygen from electrolysis in gel electromembrane extraction (G-EME) causes a negative error when applied to the analysis of easily oxidized species such as nitrite. Nitrite in G-EME is oxidized by oxygen to nitrate, leading to the negative error and the impossibility of simultaneous analysis. In this work, the application of oxygen scavengers to the acceptor phase of the G-EME system was attempted to minimize the oxidation effect. Several oxygen scavengers were selected and examined according to their compatibility with ion chromatography. The mixture of sulfite and bisulfite (14mg L-1) showed the highest efficiency in preventing the oxidation of nitrite to nitrate. Under the optimized conditions, a good linear range was obtained (10-200μg L-1; R2>0.998) with a detection limit of 8µg L-1 for both nitrite and nitrate. This method was applied to the simultaneous determination of nitrite and nitrate in sausage samples.

Photocatalytic Hydrogen Production: Role of Sacrificial Reagents on the Activity of Oxide, Carbon, and Sulfide Catalysts

Photocatalytic water splitting is a sustainable technology for the production of clean fuel in terms of hydrogen (H2). In the present study, hydrogen (H2) production efficiency of three promising photocatalysts (titania (TiO2-P25), graphitic carbon nitride (g-C3N4), and cadmium sulfide (CdS)) was evaluated in detail using various sacrificial agents. The effect of most commonly used sacrificial agents in the recent years, such as methanol, ethanol, isopropanol, ethylene glycol, glycerol, lactic acid, glucose, sodium sulfide, sodium sulfite, sodium sulfide/sodium sulfite mixture, and triethanolamine, were evaluated on TiO2-P25, g-C3N4, and CdS. H2 production experiments were carried out under simulated solar light irradiation in an immersion type photo-reactor. All the experiments were performed without any noble metal co-catalyst. Moreover, photolysis experiments were executed to study the H2 generation in the absence of a catalyst. The results were discussed specifically in terms of chemical reactions, pH of the reaction medium, hydroxyl groups, alpha hydrogen, and carbon chain length of sacrificial agents. The results revealed that glucose and glycerol are the most suitable sacrificial agents for an oxide photocatalyst. Triethanolamine is the ideal sacrificial agent for carbon and sulfide photocatalyst. A remarkable amount of H2 was produced from the photolysis of sodium sulfide and sodium sulfide/sodium sulfite mixture without any photocatalyst. The findings of this study would be highly beneficial for the selection of sacrificial agents for a particular photocatalyst.

Effect of Antimelanotic Treatment and Vacuum Packaging on Melanosis and Quality Condition of Ice Stored Farmed Tiger Shrimp (Penaeus monodon)

The objective of the study was to evaluate the effect of vacuum packaging in combination with antimelanotic treatment on quality characteristics and melanosis in farmed tiger shrimp (Penaeus monodon) collected from Ratnagiri region of Maharashtra. The processed shrimps were treated with sulfite mixture in water (30 g kg-1) and divided into two lots each with 250 shrimps. One of them was vacuum packed, the other was air packed and stored under ice. The ice stored shrimps were analyzed for quality attributes and melanosis for a period of 27 days. The treated vacuum packed shrimps had a shelf life of 24 days, whereas air packed shrimp had 16 days only. Melanosis was absent in the shrimps from both the lots throughout the storage period. Based on the results, it could be concluded that the combination of antimelanotic treatment (sulphite mixture) and packaging could significantly delay the occurrence of melanosis and increase the storage life of shrimp in ice. DOI: http://dx.doi.org/10.3329/sja.v11i2.18400 SAARC J. Agri., 11(2): 33-47 (2013)

Fuel Cell Membranes Based on Grafted and Post‐Sulfonated Glycidyl Methacrylate (GMA)

AbstractGlycidyl methacrylate (GMA) was pre‐irradiation grafted into ETFE base film of 25 μm thickness up to graft levels of 300%. The grafted films were sulfonated using a mixture of sulfite and bisulfite. FTIR and SEM–EDX analysis of the synthesized films and membranes was performed to confirm the grafting and the sulfonation. A pronounced front mechanism for grafting of GMA into ETFE was found. Regarding ex situ fuel cell relevant properties, conductivities of up to 0.25 S cm–1 were attained. For the first time, fuel cell testing of this type of membrane is reported. These grafted membranes performed comparable to a commercial benchmark membrane (Nafion® 212) and better than a styrene‐based grafted membrane with similar conductivity. Post‐test FTIR analysis showed that a fraction of the grafted chains was lost during the test under constant current conditions, yet the membrane still exhibited superior durability compared to a styrene‐based grafted membrane. Hydrolysis of the methacrylate groups was shown not to be the principle cause of the loss of sulfonic acid groups.

An efficient synthesis of substituted bis(indolyl)methanes using sodium bromate and sodium hydrogen sulfite in water

Treatment of indole with substituted aldehyde in the presence of equimolar amount of sodium bromate and sodium hydrogen sulfite mixture in water yielded corresponding substituted bis(indolyl)methanes in good yields. This provides a facile and environmentally friendly method towards the synthesis of an important class of organic compounds.

A kinetic study of Cr(VI) reduction by calcium polysulfide

The goal of this study was to determine the influence of pH and oxygen conditions on the reaction kinetics of hexavalent chromium (Cr(VI)) with calcium polysulfide (CPS). The observed kinetic reaction rate, k obs, between Cr(VI) and CPS was evaluated for the pH range 5.5–8.5, aerobic open, aerobic closed and anaerobic conditions, and two Cr(VI) species (aqueous and adsorbed on goethite). The kinetic model followed a second-order reaction rate, unlike the first-order reaction rate of the Cr(VI)-sulfide reaction. k obs increased exponentially with pH in the range of 8.5 to 5.5 under anaerobic conditions, while under aerobic conditions k obs had a maximum at pH 7. Qualitative sulfur analyses showed that thiosulfates were present at and above pH 7 in the aerobic experiments, which can also reduce Cr(VI). Similarly, pure CPS in the presence of oxygen yielded sulfides and thiosulfates, while sulfide converted to a mixture of sulfite, thiosulfates, sulfites and sulfates. CPS is thus likely to have a longer residence time and greater reducing capacity in the subsurface compared to sulfide at neutral and basic pH environments.

Sulfite‐Radical Anions in Isolated Soy Proteins

Aqueous mixtures of manganese and sulfite, at levels found in isolated soy proteins (ISP) and defatted soy flakes, spontaneously react in the presence of oxygen to produce methanethiol from the 1-electron oxidation of methionine. The carbon and sulfur of methanethiol originate from the methyl-carbon and sulfur of methionine. Similar aqueous mixtures of sulfite, manganese, and oxygen also produce sufficient levels of free radicals to degrade fluorescein. The degradation of methionine by free radicals generated in the sulfite, manganese, and oxygen reaction mixture is inhibited by the free radical spin trapping agent 5,5-dimethyl-1-pyrroline N-oxide. Processing ISP with either L-cystine or potassium iodate reduces the free sulfite content of ISP and reduces the headspace methanethiol from aqueous ISP slurries to nondetectable levels. ISP processed without additives contained sufficient levels of free radicals to generate methanethiol from the oxidation of added methionine. There were no detectable levels of methanethiol produced when methionine was added to ISP processed with iodate.

Organosulfur oxoacids. Part 1. Synthesis, structure, and reactivity of dimethylaminoiminomethanesulfinic acid (DMAIMSA)

One of the major metabolites of dimethylthiourea, dimethylaminoiminomethanesulfinic acid (DMAIMSA), was synthesized by controlled oxidation of dimethylthiourea using hydrogen peroxide. The crystal structure was determined by X-ray crystallography. It is a zwitterionic species in its solid form, with a positive charge delocalized around an sp2-hybridized carbon center and two nitrogen atoms. It crystallizes in the triclinic P[Formula: see text] space group. The C—S bond, at 1.880(2) Å, is much longer than a typical C—S single bond length of 1.79 Å. It is also longer than the one observed in thiourea trioxide, a comparable sulfonic acid. This C—S bond is stable in acidic conditions and is easily cleaved in basic conditions or in the presence of suitable nucleophiles that can attack the positively disposed carbon center. DMAIMSA is highly reactive and easily decomposes in basic conditions to yield dithionite in the presence of oxygen, whereas in strictly anaerobic conditions it gives a mixture of sulfite and sulfide. The precursor to dithionite, SO2·–, is formed from the one-electron oxidation of the sulfoxylate anion, SO22–, which results from an initial heterolytic cleavage of the C—S bond in DMAIMSA. The sulfur center is oxidized, even by mild oxidants such as aqueous iodine, to sulfate. Key words: thiourea metabolites, synthesis, structure, reactivity.

Inhibition of superoxide dismutase, Vitamin C and glutathione on chemiluminescence produced by luminol and the mixture of sulfite and bisulfite

In a system which consisted of luminol (3-aminophthalhydrazide), cobalt sulfate (CoSO 4), alkaline buffer and the mixture of NaSO 3 and sodium bisulfite (NaHSO 3) (sulfite and bisulfite = 3:1, m/m), a strong chemiluminescence (CL) was observed using a BPCL ultra-weak luminometer. The CL signals resulted from 3-aminophthalate (the product of oxidized luminol), and were affected by the buffer pH, buffer medium and the concentrations of luminol, CoSO 4 and the NaSO 3–NaHSO 3 mixture. The observation that the CL intensities were inhibited by superoxide dismutase (SOD), Vitamin C (Vc) and glutathione (GSH) in a dose-dependent manner suggested that superoxide radical (O 2 −) was involved in the CL reaction and responsible for oxidation of luminol.

Combination of ashless antiwear additives with metallic detergents: interactions with neutral and overbased calcium sulfonates

The interactions of neutral and overbased calcium sulfonate detergents with ashless thiophosphate oil additives under boundary lubrication were studied. The ashless additives used were neutral and acidic dialkyldithiophosphate (DTPs) and neutral triaryl monothiophosphate (MTP). This study uses three surface analytical tools to provide elemental and chemical information at the surface and in the bulk of the derived tribochemical films. The elemental composition of the tribofilms was studied using X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray analysis (EDX) (combined with scanning electron microscopy (SEM)). Corresponding P and S X-ray absorption near edge structure (XANES) spectroscopy was also used to provide further insight into the chemical composition of the films. SEM images of the derived tribofilms revealed that each film had distinct topographical features associated with it. XPS and EDX revealed that when oil is blended with calcium sulfonate, considerable amount of calcium is incorporated into all the tribochemical films. The phosphorus content of the tribofilm was reduced substantially when the overbased detergent was combined with MTP additive. XANES spectroscopy of the P L-edge provided direct evidence for the formation of calcium phosphate in tribofilms from the ashless additives in combination with the detergent. S K-edge revealed that sulfate is the main sulfur species formed in the bulk for all three tribofilms in the presence of the neutral detergent while a mixture of sulfite and sulfide species are formed when the overbased was used. S L-edge XANES showed that calcium sulfonate has undergone some oxidation at the surface. A more antagonistic effect was observed for MTP, with the formation of a very thin phosphate film. Tribological performance was also evaluated. Surprisingly, combination of the neutral detergent with any of the AW additives did not result in any significant change in wear to the substrate. For MTP plus neutral detergent, the thinner phosphate film produced, combined with very little change in wear protection confirms that, not only is the tribochemistry dominated by calcium sulfonate, but also confirms the anti-scuffing and AW properties that are associated with it as well. Even more surprising, was the significant decrease in wear when the overbased detergent is used. This illustrates not only that the tribochemistry was dominated by the detergent, but also the exceptional AW properties of calcium carbonate.

Novel spectrofluorimetric method for the determination of sulfite with rhodamine B hydrazide in a micellar medium

A novel spectrofluorimetric method for the determination of sulfite using rhodamine B hydrazide as fluorogenic reagent in the presence of polyoxyethylene sorbitan monooleate (Tween 80) surfactant micelles is described. The method is based on the mixture of sulfite with rhodamine B hydrazide, a colorless, non-fluorescent substance in Tween 80 surfactant micelles which gives rhodamine B-like fluorescence emission. The fluorescence intensity increase is linearly related to the concentration of sulfite in the range 5–800 ng ml −1 with a detection limit of 1.4 ng ml −1 (3 σ). The optimal conditions for the detection of sulfite are evaluated and the possible detection mechanism is also discussed. The method has been successfully applied to the determination of total sulfite in wines and compares well with the standard iodimetric method.

Synthesis of indole-4-carboxaldehydes and 4-acetylindole fromN-alkyl-5-aminoisoquinolinium salts

N-Alkyl-5-aminoisoquinolinium salts (8a-d) are converted into indole-4-carboxaldehydes (1a-c) on heating in a two phase alkyl acetate-water system containing an excess of a 2:1 sodium bisulfite-sodium sulfite mixture. 4-Acetylindole 1e is prepared in the same way from 1-methyl-2-cyanomethylisoquinolinium bromide 8f.

Nonaromatic Products from Anoxic Conversion of Benzoyl-CoA with Benzoyl-CoA Reductase and Cyclohexa-1,5-diene-1-carbonyl-CoA Hydratase

The enzymes benzoyl-CoA reductase and cyclohex-1, 5-diene-1-carbonyl-CoA hydratase catalyzing the first steps of benzoyl-CoA conversion under anoxic conditions were purified from the denitrifying bacterium, Thauera aromatica. Reaction products obtained with [ring-(13)C(6)]benzoyl-CoA and [ring-(14)C]benzoyl-CoA as substrates were analyzed by high pressure liquid chromatography and by NMR spectroscopy. The main product obtained with titanium(III) citrate or with reduced [8Fe-8S]-ferredoxin from T. aromatica as electron donors was identified as cyclohexa-1, 5-diene-1-carbonyl-CoA. The cyclic diene was converted into 6-hydroxycyclohex-1-ene-1-carbonyl-CoA by the hydratase. Assay mixtures containing reductase, hydratase, and sodium dithionite or a mixture of sulfite and titanium(III) citrate as reducing agent afforded cyclohex-2-ene-1-carbonyl-CoA and 6-hydroxycylohex-2-ene-1-carbonyl-CoA. The potential required for the first electron transfer to the model compound S-ethyl-thiobenzoate yielding a radical anion was determined by cyclic voltammetry as -1.9 V versus a standard hydrogen electrode. The energetics of enzymatic ring reduction of benzoyl-CoA are discussed.

Pressurized flow-driven capillary electrochromatography using ion exchange resins

Capillary electrochromatography using cation and anion exchange resins under pressurized flow is demonstrated to be applied to the separation of charged solutes, such a lanthanide ions. The typical variation of elution order for the mixture of sulfite, sulfate, and thiosulfate ions, the reduction and extension of elution times due to the application of high voltage, and the simultaneous separation of cations and anions are demonstrated. A minor component appears by shifting the elution time of a major component while applying a high electric field. The electric resistance of the column was measured under electrochromatographic conditions, and its dependence on the applied voltage has been discovered. From the relationship between elution times and applied voltage, the sum of electrophoretic mobility of an ion and electroosmotic mobility is estimated for landthanide cations. The capacity factor in electrochromatography is found to depend, to some extent, on the potential gradient. © 1997 John Wiley & Sons, Inc. J Micro Sep9: 347–356, 1997

Light-induced changes in the quenching of 9-amino-acridine fluorescence by photosynthetic membranes due to atmospheric pollutants and their products

The normal changes in light-induced quenching of 9-amino-acridine fluorescence by detached thylakoid membranes obtained from lysed oat chloroplasts were compared with those in the presence of various concentrations of added ozone, sulphite, sulphate, nitrite and/or nitrate in order to determine if the ability of the photosynthetic membranes to create and maintain effective proton gradients were affected by the likely products of atmospheric pollution within plastids. No disturbances of thylakoid properties due to sulphate occurred below 2 m m whilst only concentrations of nitrate, sulphite or nitrite greater than 1 m m appeared to significantly affect the redistribution of the 9-amino-acridine probe in the light. Pulses of ozone, by contrast, were highly effective in creating significant reductions in light-induced quenching of 9-amino-acridine fluorescence even at very low dosages (50 nmoles). This damage to the effectiveness of thylakoids to generate proton gradients by ozone was enhanced by light and a secondary dark-dependent partial repair mechanism was detected. Experiments with mixed pollutants or their products revealed no ‘more than additive’ interactions between ozone plus sulphite or nitrite but the mixture of sulphite plus nitrite was a highly detrimental combination with synergistic effects detected at concentrations as low as 0·1 m m of each. These results would explain in large part the known sensitivity of photosynthetic reactions to ozone and to SO 2 plus NO 2 fumigations.

Nitrate reduction by higher plant peroxidase

In our previous experiments cell-free extracts from different plants, unable to form nitrite in the presence of nitrate and any nitrate reductase donator, reduced nitrate when incubated with a specific donordiethyldithiocarbamate and sulfite mixture [2,3] . Since the preparations possessed high peroxidase activity, it appeared logical to study peroxidase preparations of various purity with respect to their ability to reduce nitrate. The present work has shown that it is a peroxidase enzyme that is responsible for nitrate reduction under the conditions described below. Preparation 1 0.6 70 41.4 from Beitch 1.3 219 97.5 (Japan) 1.5 266 106.2 1.6 303 114.5 1.8 583 150.0

Organometallic reactions. Part XIII. The reaction of trialkyltin alkoxides and of bistrialkyltin oxides with sulphur dioxide, sulphodi-imides, and sulphinylamines

The addition of trialkyltin alkoxides (R13Sn·OR2) and of bistrialkyltin oxides (R13Sn·O·SnR31) to the heterocumulenes sulphur dioxide, sulphodi-imides (R3NSNR3) and sulphinyl-amines (R3NSO) have been investigated.Sulphur dioxide yields sulphites (R31Sn·O·SO·OR2 and R31Sn·O·SO·O·SnR31) from which the sulphur dioxide may be displaced by a more powerful acceptor such as an isocyanate.Bistrialkyltin oxides (but not trialkyltin alkoxides) react exothermically with diaryl sulphodi-imides. The NN′-diaryl-NN′-bis(tributyl-stannyl)sulphinyldiamines (R31Sn·NAr·SO·NAr·Sn·R31) which are formed behave in subsequent reactions as adducts between bis(trialkylstannyl)amines (R31Sn·NAr·SnR31) and sulphinylamines (ArNSO). Acceptor molecules such as icosyanates, sulphur dioxide, and chloral, displace the sulphinylamine, and give an adduct between the distannylamine and the new acceptor.Bistrialkyltin oxides react exothermically with sulphinylamines to give sulphimates (R31Sn·NR3·SO·O·SnR31) which appear to be in equilibrium with the corresponding NN′-sulphinyldiamines (R31Sn·NR3·SO·NR3·SnR31) and sulphite (R31Sn·O·SO·O·SnR31). Acceptors such as sulphur dioxide, phenyl isocyanate, or chloral, displace the sulphinylamine from the adduct but more sulphinylamine reacts to give the ditin sulphite and sulphodi-imide (R3NSNR3).The sulphinylamines are weak acceptors for the trialkytin alkoxides, and produce the sulphimates (R31Sn·NR2·SO·OR2) in equilibrium; these react with more sulphinylamines to give a mixture of sulphite (R31Sn·O·SO·OR2) and sulphodi-imide (R3NSNR3).

Radiochemical Determination of Polythionates.

Two radiochemical methods were developed for the determination of polythionates. In the first method, the polythionates are reacted with sulfite and with a mixture of sulfite and sulfide. The thiosulfate formed in these reac tions is then determined with Ag/sup 110/SCN. In the second method the sulfide contains the radioactive isotope S/sup 35/ and the amount of radioactive thiosulfate formed is instead determined. A correction must be applied for the amount of radioactive thiosulfate formed by isotopic exchange between the sulfide and thiosulfate. (auth)

LXXXIX.—Action of iodine on a mixture of sulphite and thiosulphate

The first page of this article is displayed as the abstract.