Mixture Of Nitrite Research Articles

Metabolic Behavior of Denitrifying Phosphate-Accumulating Organisms under Nitrate and Nitrite Electron Acceptor Conditions.

The effects of various types of electron acceptors on anoxic phosphorus uptake were investigated in detail to obtain a better insight into the metabolic behavior of denitrifying phosphate-accumulating organisms. Batch experimental tests under three different electron acceptor conditions, i.e., nitrate, nitrite and mixtures of nitrate and nitrite, were carried out using activated sludge cultivated in a sequencing batch reactor. The experimental results confirmed no inhibition of the utilization of nitrate or nitrite as an electron acceptor for anoxic phosphorus uptake. Anoxic phosphorus uptake occurred provided there was an electron acceptor present regardless of whether it was nitrate or nitrite. However, for nitrite a relatively small amount of anoxic phosphorus was taken up per nitrogen denitrified compared to nitrate. On the other hand, the amount of anoxic phosphorus taken up per nitrogen denitrified increased with an increase in the initial loading amount of electron acceptor in the case of nitrate, whereas it slightly decreased nitrite. Moreover, the amount of phosphorus taken up per nitrogen denitrified decreased with increasing mixed liquor suspended solid (MLSS) concentration in the case of nitrate, while it slightly increased for nitrite. From these results, it was confirmed that the activity of anoxic phosphorus uptake is strongly associated with the type and the initial loading amount of electron acceptor and the MLSS concentration under anoxic conditions.

The effect of paprika, garlic and salt on rancidity in dry sausages

Eight batches of ground fat and eight batches of a mixture of meat and fat (70 and 30%, respectively), were prepared by adding salt, paprika and garlic, in the proportions used for making chorizo — a dry fermented sausage — stuffed into natural casings and then ripened. The evolution of rancidity in these products was evaluated by means of total free fatty acid content, peroxide value and TBARS during the ripening period. Spanish paprika and salt showed antioxidant and prooxidant properties, respectively. Paprika was even able to inhibit the prooxidant effect of salt. Also, four batches of chorizo were made to compare the antioxidant effect of the spices (garlic and paprika) with a mixture of nitrate, nitrite and ascorbic acid. In this respect, paprika and garlic were as effective as the mixture of additives in inhibiting lipid oxidation.

Effect of nitrite on anoxic phosphate uptake in biological phosphorus removal activated sludge

Results from a series of batch experiments are presented, in which activated sludge obtained from an alternating type biological phosphorus removal process was exposed to nitrite or mixtures of nitrite and nitrate at various concentration levels. By comparing the course of phosphate, nitrite and nitrate (measured on-line) and the internal storage components PHB and PHV (measured manually for some experiments) with batches exposed to nitrate only, the effect of nitrite on anoxic phosphate uptake was investigated. How nitrite exposure affects subsequent aerobic phosphate uptake was also examined in one experiment. The experiments show that nitrite at low concentration levels (up to about 4 to 5 mg NO 2-N/l) is not detrimental to anoxic phosphate uptake and can serve as electron acceptor for anoxic phosphate uptake. Exposure to higher concentration levels (roughly 8 mg NO 2-N/l and greater) inhibits anoxic phosphate uptake completely, and aerobic phosphate uptake severely. The critical nitrite concentration above which nitrite inhibition of phosphate uptake occurs appears to be dependent on sludge conditions, lying in the range of from 5 to 8 mg NO 2-N/l for the experiments performed in this study. The inhibiting effect of nitrite was found to last for at least several hours after the nitrite exposure.

Influence of hexamine and sodium nitrite in combination with sodium benzoate and sodium propionate on fermentation and hygienic quality of wilted and long cut grass silage

Bale silage is usually made from long or restricted cut grass. Long cut herbage may be difficult to ensile, because of delayed and heterogenous fermentation. The aim of the present study was to find the optimal composition and level of an additive based on a mixture of hexamine, ie hexamethylene-tetraamine (HMTA) and sodium nitrite (NaN) together with sodium benzoate (NaB) and sodium propionate (NaP) to restrict aerobic deterioration. The silage crop (318 g DM kg−1; 158 g CP, 98 g ash, 89 g WSC, a buffering capacity of 200 mE and an ME value of 8.7 MJ per kg DM) consisting of about 30% ryegrass (Lolium perenne L), 30% meadow fescue (Festuca pratensis L) and 40% timothy (Phleum pratense L) was harvested by a self-loading wagon. Grass was ensiled in 4 l PVC laboratory silos. Silos of each treatment were either closed immediately with a water-seal or aerated with 2.3 l air per 24 h during the first 12 days of ensiling. Silages were treated with additives containing different concentrations and combinations of HMTA, NaN, NaB and NaP. Formic acid treated silage and untreated silage were used as controls. A mixture of HMTA and NaN (KSQ) improved fermentation by reducing pH, butyric acid, ammonia and increasing lactic acid and residual water-soluble carbohydrates (WSC) concentrations. This mixture also reduced the number of Clostridium spores in the silage. Addition to 300 g HMTA and 450 g NaN ton−1 FM was satisfactory to improve fermentation and restrict clostridial activity, but the aerobic stability of the silage was low. Addition of organic acid salts was more effective and improved both fermentation and storage stability. NaB (800 g) or a mixture of 690 g NaB and 210 g NaP was satisfactory to control aerobic stability. The use of HMTA and NaN in combination with NaB and NaP resulted in high hygienic quality and storage stability of silage made from unchopped and wilted grass. © 1999 Society of Chemical Industry

Influence of hexamine and sodium nitrite in combination with sodium benzoate and sodium propionate on fermentation and hygienic quality of wilted and long cut grass silage

Bale silage is usually made from long or restricted cut grass. Long cut herbage may be difficult to ensile, because of delayed and heterogenous fermentation. The aim of the present study was to find the optimal composition and level of an additive based on a mixture of hexamine, ie hexamethylene-tetraamine (HMTA) and sodium nitrite (NaN) together with sodium benzoate (NaB) and sodium propionate (NaP) to restrict aerobic deterioration. The silage crop (318 g DM kg−1; 158 g CP, 98 g ash, 89 g WSC, a buffering capacity of 200 mE and an ME value of 8.7 MJ per kg DM) consisting of about 30% ryegrass (Lolium perenne L), 30% meadow fescue (Festuca pratensis L) and 40% timothy (Phleum pratense L) was harvested by a self-loading wagon. Grass was ensiled in 4 l PVC laboratory silos. Silos of each treatment were either closed immediately with a water-seal or aerated with 2.3 l air per 24 h during the first 12 days of ensiling. Silages were treated with additives containing different concentrations and combinations of HMTA, NaN, NaB and NaP. Formic acid treated silage and untreated silage were used as controls. A mixture of HMTA and NaN (KSQ) improved fermentation by reducing pH, butyric acid, ammonia and increasing lactic acid and residual water-soluble carbohydrates (WSC) concentrations. This mixture also reduced the number of Clostridium spores in the silage. Addition to 300 g HMTA and 450 g NaN ton−1 FM was satisfactory to improve fermentation and restrict clostridial activity, but the aerobic stability of the silage was low. Addition of organic acid salts was more effective and improved both fermentation and storage stability. NaB (800 g) or a mixture of 690 g NaB and 210 g NaP was satisfactory to control aerobic stability. The use of HMTA and NaN in combination with NaB and NaP resulted in high hygienic quality and storage stability of silage made from unchopped and wilted grass. © 1999 Society of Chemical Industry

Sequential Spectrophotometric Determination of Microgram Amounts of Nitrate and Nitrite in Mixtures

This paper describes three new methods: the first may be used for the determination of nitrite; the second is applicable to determination of nitrate; and the third permits sequential determination of both nitrite and nitrate in mixtures with no prior separation. For the determination of nitrite and nitrate in synthetic mixtures containing 1:5 to 5:1 ratios of the ions, in tap water, and in river water, mean recoveries (for 3 to 22 μg of added NO−3and NO−2) are 96.1 and 98.1% (n= 15) and coefficients of variation are 2.2 and 2.5% for NO−3and NO−2(n= 5), respectively.

Nitric oxide adsorption at Pt(100) electrode surfaces

Nitric oxide adlayers formed at Pt(100) electrode surfaces have been characterized in situ by means of electrochemical and FTIR spectroscopic experiments. These adlayers can be reductively stripped from the electrode surface yielding dissolved ammonium as the main reduction product in acidic solution. From the voltammetric charge involved in this process the absolute NO coverage for the saturated adlayers has been calculated to be 0.5. This value agrees with that corresponding to the c(4×2) overlayer found by different authors under UHV conditions. The oxidation of the NO adlayer in acid media proceeds between 0.90 and 1.10 V RHE through the formation of surface species (probably a mixture of nitrite and nitro species), which can be further oxidized to dissolved nitrate anions at higher potentials. The same NO adlayers have been found to oxidize directly to dissolved nitrite anions in alkaline solutions. The potential dependence of the N–O stretching mode, which is shifted towards higher wavenumbers when the electrode potential increases, has been analyzed for the saturated NO adlayer. Linear relations were found both in acidic and neutral solutions with tuning rates of ca. 50 cm −1 V −1 in the potential region between 0.50 and 0.90 V RHE where the saturated NO adlayers are stable. A slow dissolution process has been evidenced at potentials slightly below 0.80 V for the NO adlayer in alkaline solutions.

Ammonia from iron(II) reduction of nitrite and the Strecker synthesis: do iron(II) and cyanide interfere with each other?

The question of whether the production of ammonia, from the reduction of nitrite by iron(II), is compatible with its use in the Strecker synthesis of amino acids, or whether the iron and the cyanide needed for the Strecker synthesis interfere with each other, is addressed. Results show that the presence of iron(II) appears to have little, or no, effect on the Strecker synthesis. The presence of cyanide does interfere with reduction of nitrite, but the reduction proceeds at cyanide/iron ratios of less than 4:1. At ratios of about 2:1 and less there is only a small effect. The reduction of nitrite and the Strecker can be combined to proceed in each other's presence, to yield glycine from a mixture of nitrite, Fe+2, formaldehyde, and cyanide.

Temperature tolerance of Penaeus setiferus postlarvae exposed to ammonia and nitrite

The critical thermal maximum (CTM) method was used to determine the acute effect of ammonia, nitrite and the combined effect of both toxicants on the thermal tolerance of white shrimp ( Penaeus setiferus) postlarvae. Ammonia did not affect the temperature response of shrimp. Nitrite exposure significantly decreased the temperature tolerance of postlarvae. Coexposure to ammonia and nitrite mixtures modified the CTM; an inverse relationship between ammonia/nitrite toxicity ratios and the CTM was observed. In single exposure, ammonia and nitrite concentrations were related to the mortality rate. No relation was observed between shrimp mortality and the thermal tolerance. Our results suggest that exposure to these nitrogenous compounds can decrease the ability of white shrimp postlarvae to tolerate additional thermal stress.

In Situ Electrochemical Promotion by Sodium of the Platinum-Catalyzed Reduction of NO by Propene

The Pt-catalyzed reduction of NO by propene exhibits strong electrochemical promotion by spillover Na supplied from a β‘‘-alumina solid electrolyte. In the promoted regime, rate increases by an order of magnitude are achievable. At sufficiently high loadings of Na the system exhibits poisoning, and excursions between the promoted and poisoned regimes are fully reversible. Reaction kinetic data obtained as a function of catalyst potential, temperature, and gas composition indicate that Na increases the strength of NO chemisorption relative to propene. This is accompanied by weakening of the N−O bond, thus facilitating NO dissociation, which is proposed as the critical reaction-initiating step. The dependence of N2/N2O selectivity on catalyst potential is in accord with this view: Na pumping to the Pt catalyst favors N2 production at the expense of N2O. X-ray photoelectron spectroscopic (XPS) data confirm that electrochemical promotion of the Pt film does indeed involve reversible pumping of Na to or from the solid electrolyte. They also show that under reaction conditions the promoter phase consists of a mixture of sodium nitrite and sodium nitrate and that the promoted and poisoned conditions of the catalyst correspond to low and very high loadings of these sodium compounds. Under all reaction conditions, a substantial fraction of the promoter phase is present as 3D crystallites.

Anion Radical of Mutagenic 3–methyl–5–nitropyridazine–1,2–dioxide

The mixture of sorbic acid and nitrite, both used as food additives, exhibits mutagenicity in a weak acidic milieu. The formed 3-methyl-5-nitropyridazine-1,2-dioxide was studied with cyclic voltammetry and EPR spectroscopy.

Antioxidative activity of nitrite in metmyoglobin induced lipid peroxidation

The antioxidative activity of nitrite in metmyoglobin (MMb)-initiated lipid peroxidation in linoleic acid emulsions was examined using oxygen consumption measurement. Nitrite decreased MMb-induced lipid peroxidation with increasing concentrations. The antioxidative effect of nitrite was independent of pH in the range 6.3–5.5, and 1% NaCl did not seem to influence the antioxidative activity of nitrite. Furthermore, nitrite reduced MMb denaturation during MMb-induced peroxidation of linoleic acid. Thermal analysis using differential scanning calorimetry showed that nitrite increased the denaturation temperature of MMb. However, direct complexation between nitrite and the iron center of MMb could not be confirmed using chromatographic methods and analysis of UV-visible spectra of mixtures of nitrite and MMb. The observed results can rather be explained by a weak reversible interaction between nitrite and MMb such as binding of nitrite at the entrance to the haem cavity protecting MMb against heat denaturation and protecting both MMb and the fatty acids against oxidative degradation.

Analysis of Inorganic Anions by Capillary Zone Electrophoresis.

Determination of inorganic anions by capillary zone electrophoresis is reported in this study. An anions mixture of bromide, chloride, fluoride, nitrite, sulfite, sulfate, perchlorate, chlorate and chlorite was separated by a capillary column and detected by indirect UV method. The running buffer contained 5mM ammonium dichromate, 10mM ammonium acetate, 20mM diethylenetriamine, and in 10% methanol solution at pH 9.3. A potential of 15kV at the cathode(reversed polarity) was utilized for the separation of inorganic anions. A complete separation of anions was achieved in less than 10 min and the applicabilities of the method were demonstrated for forensic evidences. We performed analysis of inorganic anions in toluene inhaled human's urine and in postmortem bloods by capillary zone electrophoresis and ion chromatography

Salivary thiol oxidase activity of Rhodnius prolixus

Cysteine and other thiol compounds can accelerate the unloading of nitric oxide (NO) from salivary nitrosyl-nitrophorins of the blood sucking bug Rhodnius prolixus. The dependence of NO unloading on cysteine concentration is biphasic, showing a maximum between 0.5 and 1 mM cysteine. The proposed mechanism of action for the unloading is a series of reactions where cysteine (at low concentrations) reacts with the heme group of nitrophorins to form cystine and superoxide. The superoxide then reacts with NO to form peroxynitrite, which decays to a mixture of nitrite and nitrate anions. At high cysteine concentrations, cysteine is converted to cystine and H 2O and thus no removal of NO from nitrophorins is observed. The thiol oxidase activity of Rhodnius nitrophorins is similar to that observed before in plant peroxidases [Pichorner et al., Phytochemistry 31, 3371 (1992)]. The possible physiological significance of this reaction to probing and feeding by R. prolixus is discussed.

Effects of age on endometrial carcinogenesis induced by concurrent oral administration of ethylenethiourea and sodium nitrite in mice

Aging effects on the susceptibility to chemical endometrial carcinogenesis were investigated in ICR female mice. The animals were divided into 3 groups of different ages: 1 month (young), 6 months (middle), and 12 months (old) at initiation of treatment. They received weekly oral administration of mixture of ETU (100 mg/kg body weight) and sodium nitrite (70 mg/kg body weight) for 6 months followed by a withdrawal period of 3 months. All animals were subjected to histopathology. The incidence of endometrial adenocarcinomas was highest in the middle age group (8/20), secondary in the old age group (4/20), and lowest in the young group (1/20). The incidence of atypical glandular hyperplasia, a precursor lesion of the tumor, was also higher in the middle age group. The endometrial adenocarcinomas showed morphological similarities among all age groups and the nuclei of tumor cells lost almost all staining reactivity to estrogen receptors. The labeling indices with bromodeoxyuridine (BrdU) were notably higher in the old age group than in the young and middle age groups. A further investigation on the aging process of female genital organs in control mice revealed that their senility seemed to be preceded by the formation of ovarian cysts which first appeared at 6 months of age with a concomitant elevation of plasma 17 beta-estradiol level. These results indicate that the susceptibility of the mouse endometrium to the carcinogenic effects of N-nitroso ETU could be closely linked with the stage of aging process of the genital organs and it appears to be most susceptible when initiated at around 6 months of age. However, the mitotic activity of neoplastic endometrial glandular cells seems to be higher in older mice than younger ones.

Application of free-radical chromogens to determination of nitrite and nitrate ions by EPR spectrometry

Various azines and substituted phenylene diamines are oxidized by the nitrite ion to give stable radicals in an autocatalytic reaction. This finding has now been developed into highly sensitive methods for nitrite determination by EPR spectrometry. Thus, when the reagent is phenothiazine, the detection limit for nitrite is 0.012 ppm, the relative standard deviation at 0.05 ppm is 1.9%, and the analytical range is 0–1.5 ppm. With N, N, N′, N′-tetramethyl- p-phenylenediamine as the reagent, the corresponding values are 0.025 ppm, 2.6%, and 0–1.3 ppm. Nitrate can be determined after prior reduction to nitrite. A mixture of nitrite and nitrate ions can also be quantitatively analysed. The EPR methods were applied to the determination of the nitrite and nitrate contents of prepacked cooked ham and of soft-spreading cheese. The results agreed well with those obtained by ISO and AOAC standard methods for these samples. ca*|Author for correspondence.

Electrochemical reduction of nitrogen oxyanions in 1 M sodium hydroxide solutions at silver, copper and CuInSe2 electrodes

The reduction of nitrate and nitrite ions was studied in 1m NaOH supporting electrolyte. Voltammetric investigations show that, on silver cathodes, nitrate reduction begins at potentials about 500 mV more positive than nitrite reduction, the latter being superimposed on hydrogen evolution. Electrolyses of nitrate solutions at −1.4V/sce give nitrite with good selectivity. On copper cathodes, nitrate and nitrite reductions occur in the same region of potentials and show similar voltammetric profiles. The dominant product of nitrite reduction is ammonia, whereas nitrate may be reduced to nitrite at −1.1 V/sce and to ammonia with high yields at −1.4 V/sce. Reduction of nitrogen oxyanions may also be performed on CuInSe2 (photo)cathodes. Photoassisted reductions of nitrate performed on p-CuInSe2 at −1.4 V/sce gave mixtures of ammonia, nitrite and hydrogen.

Experimental design and partial least squares for optimization of reversed-phase ion-interaction liquid chromatographic separation of nitrite, nitrate, and phenylenediamine isomers

Ion-interaction chromatographic data were treated by chemometric methods in order to optimize resolution and analysis time. A mixture of nitrite, nitrate, and 1,4- 1,3-, and 1,2-phenylenediamine at average 0.5 ppm levels was considered. The effect on retention of alkyl chain length of the ammonium salt used as the interaction reagent, its concentration, and flow rate were studied

Nitrite toxicity inAspergillus nidulans: Effect of mutation at thenihB gene

ThenihB gene ofAspergillus nidulans was found to confer sensitivity to elevated concentrations of nitrite, compact morphology and absence of conidiation. ThenihB locus was allocated to linkage group II and was recessive in heterozygous diploids. When thenihB1 mutant was grown on a mixture of nitrite plus NH 4 (+) its sensitivity to nitrite was unchanged. A possible role for this gene in nitrite transport and/or the maintenance of membrane integrity is discussed.

Kinetic-spectrofluorimetric determination of nitrite and nitrate at the nanograms per millilitre level by manual and flow-injection methods

The catalytic effect of nitrite on the oxidation of phenosafranine by bromate in acidic medium was studied by using the decrease in fluorescence intensity of phenosafranine. This kinetic—spectrofluorimetric method for nitrite is linear over the range 0.9–13.8 ng ml −1 with a relative standard deviation of about 1.5%. The method can be successfully adapted to flow-injection analysis in the stopped-flow mode. Manual and flow-injection methods were satisfactorily applied to the determination of nitrite in waters and meat products. The inclusion of a copperized cadmium column in the flow system allows the determination of nitrate and the sequential determination of nitrate and nitrite in mixtures.