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Search Results: 1 - 10 of 8276 matches for " nitrogen compounds "
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Interferences by Organic Nitrogen Compounds in Ammonium-N Determination
Muhammad Ayyaz Khan,T.H. Flower
Pakistan Journal of Biological Sciences , 1999,
Abstract: Organic nitrogen compounds were evaluated for interferences in NH4-N determination in water, 2M KCl and 0.5M K2SO4 at NH4-N level of 0 and 1.0 mg l-1. The results revealed that organic nitrogen compounds interfere negatively in NH4-N determination using the Technicon AutoAnalyzer II. Soil extracting solutions like 2M KCl and 0.5M K2SO4 further increased interferences by these compounds. These results suggested that a pre-treatment step either distillation or gas phase dialysis should be included to reduce the interferences caused by the organic nitrogen compounds in the NH4-N determination by the Technicon AutoAnalyzer II.
Ionic Liquid Assisted Extraction of Nitrogen and Sulphur-Containing Air Pollutants from Model Oil and Regeneration of the Spent Ionic Liquid  [PDF]
Ikenna Anugwom, P?ivi M?ki-Arvela, Tapio Salmi, Jyri-Pekka Mikkola
Journal of Environmental Protection (JEP) , 2011, DOI: 10.4236/jep.2011.26091
Abstract: Removal of air pollutants, such as nitrogen and sulphur containing compounds from a model oil (dodecane) was studied. An ionic liquid (1-ethyl-3-methylimidazolium chloride [C2mim] [Cl]) was used as an extractant. Liquid-liquid extraction by using 1-ethyl-3-methylimidazolium chloride [C2mim] [Cl] was found to be a very promising method for the removal of N- and S-compounds. This was evaluated by using a model oil (dodecane) with indole as a neutral nitrogen compound and pyridine as a basic nitrogen compound. Dibenzothiophene (DBT) was used as a sulphur compound. An extraction capacity of up to 90 wt% was achieved for the model oil containing pyridine, while only 76 wt% of indole in the oil was extracted. The extraction capacity of a model sulphur compound DBT was found to be up to 99 wt%. Regeneration of the spent ionic liquid was carried out with toluene back-extraction. A 1:1 toluene-to-IL wt ratio was performed at room temperature. It was observed that, for the spent ionic liquid containing DBT as a model compound more than 85 wt% (corresponding 3852 mg/kg) could be removed from the oil. After the second regeneration cycle, 86 wt% of the DBT was recovered from the ionic liquid to toluene. In the case of indole as the nitrogen containing species, more than 99 wt%, (corresponding to 2993 mg/kg) of the original indole was transferred from the model oil to the ionic liquid. After the first-regeneration cycle of the spent ionic liquid, 54 wt% of the indole–in-IL was transferred to toluene. Thus, both extractions of nitrogen and sulphur model compounds were successfully carried out from model oil and the back-extraction of these compounds from the ionic liquids to toluene demonstrated the proved the concept of the regeneration point of view.
Digest?o dos nutrientes e balan?o de compostos nitrogenados em cabras alimentadas com quatro níveis de proteína
Fonseca, C.E.M.;Valadares, R.F.D.;Valadares Filho, S.C.;Le?o, M.I.;Marcondes, M.I.;
Arquivo Brasileiro de Medicina Veterinária e Zootecnia , 2008, DOI: 10.1590/S0102-09352008000100027
Abstract: feed intake, ph, and ruminal ammonia concentration were evaluated in four goats in which omasal digesta was collected by ruminal fistula in order to estimate the ruminal digestion of nutrients. the urinary total nitrogen compounds (n) and the concentrations of n-urea in serum (nus), milk (nul), and urine were evaluated in 12 goats assigned to three 4x4 latin squares. the animals were fed rations composed of 50% of maize silage and 50% of concentrate, containing 11.5, 13.5, 15.5, and 17.5% of crude protein (cp) in the dry matter. with the exception of protein, the intake and total digestibility of the other nutrients were not influenced by the dietary cp levels. ruminal ph was reduced in the post-prandial period. as the n intake increased, ruminal concentration of ammonia, nus and nul concentrations, urinary volume the n balance increased. it was concluded that the level of 13.5%, or 245 grams of cp, is sufficient for goats producing 1.6kg per day and that the method of omasal digesta collection needs to be evaluated in more detail for its validation in goats.
Avalia??o da Composi??o de Vários Alimentos e Determina??o da Cinética Ruminal da Proteína, Utilizando o Método de Produ??o de Gás e Am?nia in Vitro
Londo?o Hernández, Fernando Iván;Valadares Filho, Sebasti?o de Campos;Paulino, Mario Fonseca;Mancio, Ant?nio Bento;Cecon, Paulo Roberto;Lana, Rogério de Paula;Magalh?es, Karla Alves;Reis, Sandro Luiz Rosa;
Revista Brasileira de Zootecnia , 2002, DOI: 10.1590/S1516-35982002000100027
Abstract: chemical determinations and kinetics studies of nitrogen compounds of 24 concentrate feedstuffs and 10 grasses were made using the concentrations of soluble nitrogen in tca and gas production. it was used 200 ml of ruminal fluid and 800 ml of medium for 100 vessels. it was used 1.0 g of trypticase and 0.1 ml of microminerals solution to prepare 400 ml of medium. it was used 0.8 g of ammonium bicarbonate and 7 g of sodium bicarbonate to prepare 200 ml of buffer solution and, to prepare 200 ml of macromineral solution, 1.15 g of na2hpo4 anhydrous, 1.25 g of kh2po4 anhydrous and 0.1 g of mgso4.7h2o were weighed. reducing solution was prepared with 0.64 g of cysteine-hcl, 0.64 g of sodium sulfide and 4 ml of 1n naoh. the disappearance of nitrogen compounds of feedstuffs was determined at 6 and 12 hours, where 1.875 mg of n was incubated with 0, 33, 67, 100 mg oh starch, 6 ml of medium, 4 ml of ruminal fluid-medium mixture and 0.1 ml of reducing solution using co2. data of degradation rates indicated that corn gluten feed, casein, dry grounded peanut grain, cassava rasp, sorghum silage with or without inoculum, corn silage and honeygrass showed the highest rates of protein degradation and the slowest degradation rates were obtained by sugar cane yeast, feather meal, fish meal, broiler litter using wood rind as adsorvent and signalgrass. estimates of degradation rates of forage feedstuffs were higher than degradation rates estimated previously by an inhibitor method. it is recommended to use 12 hours for incubation of concentrate feedstuffs and 6 hours for grasses.
The general mechanisms of attack of nitrogen nucleophiles on carbonyl compounds: facts that determine the change of the rate-pH profiles
Brighente, Inês Maria Costa;Yunes, Rosendo Augusto;
Journal of the Brazilian Chemical Society , 1997, DOI: 10.1590/S0103-50531997000500018
Abstract: it have been described a general mechanism for the attack step of the reactions between nitrogen nucleophiles and carbonyl compounds to form a neutral tetrahedral addition intermediate. this general mechanism is based on the relative importance of the "concerted" hydronium-ion catalyzed attack of the nitrogen base on the carbonyl compound with respect to the "step wise" mechanism that involves the previous formation of a zwitterionic tetrahedral intermediate (t±) and the posterior proton transfer to it from the hydronium-ion. the relative importance of this pathway gives origin to three kinds of profile rates vs ph for these reactions. on the other hand, the importance of the "stepwise" mechanism was attributed to a dependence on the stability of the t± intermediate that is related to the pka of the nitrogen base and the kad (the equilibrium constant for the formation of the neutral tetrahedral addition intermediate (t0)). the comparison of the reactions of p-chlorobenzaldehyde and norcamphor with different nitrogen nucleophiles led to the observation that the general mechanism depends on each type of carbonyl compound. this is due to the great influence of the steric and electronic effects of the compounds structure, and the fact that the pka value of the nitrogen base, which is more related to the stability of the t± than the t0 intermediate, is more important as a factor of prediction of the profiles than the value of kad, this value being more related to the stability of the t0 intermediate.
The influence of water management and environmental conditions on the chemical composition and beverage quality of coffee beans
Silva, Emerson A. da;Mazzafera, Paulo;Brunini, Orivaldo;Sakai, Emílio;Arruda, Flávio B.;Mattoso, Luiz Henrique C.;Carvalho, Cássia R. L.;Pires, Regina Célia M.;
Brazilian Journal of Plant Physiology , 2005, DOI: 10.1590/S1677-04202005000200006
Abstract: the influence of environmental conditions and irrigation on the chemical composition of green coffee beans and the relationship of these parameters to the quality of the beverage were investigated in coffee plantations in the regions of adamantina, mococa and campinas, in the state of s?o paulo, brazil. the chemical composition and physical aspects of green coffee beans produced in the three regions were related through principal component analyses (pca) to the quality of beverage, as determined by sensorial and electronic analyses. the chemical composition was affected by the environmental conditions. some differences in cup quality were detected by the electronic method but not by cup tasting. irrigation was not a major factor affecting chemical composition, since there were few differences in relation to non-irrigated coffee plants. the production site appeared to be the main influencing factor on biochemical composition. a pronounced difference was observed in adamantina, where annual average air temperature was 1.6-2.4oc warmer than in the other two areas and about 3.5oc above to the optimal limit for coffee cultivation.
Avalia??o da eficiência de extra??o de compostos nitrogenados da polpa de anchoíta (Engraulis anchoita)
Furlan, Valcenir Júnior Mendes;Silva, Ana Paula Rosa da;Queiroz, Maria Isabel;
Ciência e Tecnologia de Alimentos , 2009, DOI: 10.1590/S0101-20612009000400021
Abstract: the objective of this work was to evaluate the efficiency of the nitrogen compounds extraction like soluble proteins (sp), total nitrogen (tn), non protein nitrogen (npn), and nitrogen protein (np) from the anchovy pulp (engraulis anchoita), as well to investigate their proximal composition and freshness alteration based on the capture place. the anchovy pulp was submitted to nitrogen extraction treatment using nahco3 (0.1; 0.2; 0.3 and 0.5%), nacl 0.3% as solutions and distilled water. the pulp washing cycles using 0.1% nahco3, two cycles of distilled water, and one of nacl 0.3% demonstrated improved efficiency in the extraction of the nitrogenous compounds and sarcoplasmatic proteins. concerning the determination of the proximal composition, the anchovy in natura showed moisture content 77.2%, protein 16.8%, lipids 3.4%, and ash 2.4% and the values for the anchovy pulp were moisture 78.1%, protein 17.5%, lipids 2.4% and ash 2%. the freshness evaluation was accomplished through ph, total volatile bases (n-bvt), and trimethylamine (n-tma) and they were found 6.3; 11.5 mg.100 g-1 and 2.8 mg.100 g-1 for the anchovy in natura and 6.7; 20.2 mg.100 g-1; 3.1 mg.100 g-1 for the pulp, respectively.
Effects of fire on soil nitrogen dynamics and microbial biomass in savannas of Central Brazil
Nardoto, Gabriela Bielefeld;Bustamante, Mercedes Maria da Cunha;
Pesquisa Agropecuária Brasileira , 2003, DOI: 10.1590/S0100-204X2003000800008
Abstract: the objective of this work was to study the effects of fire on net n mineralization and soil microbial biomass in burned and unburned cerrado stricto sensu sites. the study was carried out from april 1998 to april 2000. the ph values were significantly higher in the burned site while soil moisture content was significantly higher in the unburned site (p<0.05). the soil c/n ratio was 22/1 and the available no3-n ranged between 1.5 and 2.8 mg kg-1 dry weight. however, the nh4-n concentration ranged between 3 and 34 mg kg-1 dry weight in the burned site and between 3 and 22 mg kg-1 dry weight in the unburned site. the nh4-n increased after fire, but no significant changes were observed for no3-n (p<0.05). the no3-n accumulation occurred in short periods during the rainy season. the rates of net n mineralization increased during the rainy season while reductions in soil microbial biomass were observed at both sites. this suggested that the peak in microbial activities occurred with the first rain events, with an initial net immobilization followed by net mineralization. both sites presented the same pattern for mineralization/immobilization, however, the amount of inorganic-n cycled annually in unburned site was 14.7 kg ha-1 per year while the burned site presented only 3.8 kg ha-1 of inorganic-n, one year after the burning.
Toxicological risk of melamine and cyanuric acid in food and feed
Pavel Suchy, Eva Straková, Ivan Herzig, Jaroslav Staňa, Renata Kalusová, Markéta Pospíchalová
Interdisciplinary Toxicology , 2009, DOI: 10.2478/v10102-009-0010-6
Abstract: From the toxicological point of view, in the last two years melamine and cyanuric acid have become matters of great interest. These substances, especially melamine, have been abused during food and feed adulteration by increasing the content of nitrogen compounds in these products. Melamine and cyanuric acid as individual substances do not pose any serious risk in terms of toxicology. From the point of view of toxicology, it is especially the complex of melamine with cyanuric acid that is important. This complex, also known as the melamine-cyanurate complex, is a cause of human and animal health problems. In this work we present two examples of the incidence of melamine and cyanuric acid in two feed products originating from China. They were rice and the pea concentrates intended for animal nutrition. Protein concentrates can be the main risk factor for food chain contamination with melamine and cyanuric acid, especially those of unknown origin. Feed with a high content of nitrogen compounds and low content of aminoacids can be regarded as particularly suspicious. A comparison of results for determining nitrogen compounds and amines can be used as proof of adulteration of protein feeds. These feeds must be subjected to further analysis to determine melamine and cyanuric acid.
Effects of fire on soil nitrogen dynamics and microbial biomass in savannas of Central Brazil
Nardoto Gabriela Bielefeld,Bustamante Mercedes Maria da Cunha
Pesquisa Agropecuária Brasileira , 2003,
Abstract: The objective of this work was to study the effects of fire on net N mineralization and soil microbial biomass in burned and unburned cerrado stricto sensu sites. The study was carried out from April 1998 to April 2000. The pH values were significantly higher in the burned site while soil moisture content was significantly higher in the unburned site (P<0.05). The soil C/N ratio was 22/1 and the available NO3-N ranged between 1.5 and 2.8 mg kg-1 dry weight. However, the NH4-N concentration ranged between 3 and 34 mg kg-1 dry weight in the burned site and between 3 and 22 mg kg-1 dry weight in the unburned site. The NH4-N increased after fire, but no significant changes were observed for NO3-N (P<0.05). The NO3-N accumulation occurred in short periods during the rainy season. The rates of net N mineralization increased during the rainy season while reductions in soil microbial biomass were observed at both sites. This suggested that the peak in microbial activities occurred with the first rain events, with an initial net immobilization followed by net mineralization. Both sites presented the same pattern for mineralization/immobilization, however, the amount of inorganic-N cycled annually in unburned site was 14.7 kg ha-1 per year while the burned site presented only 3.8 kg ha-1 of inorganic-N, one year after the burning.
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