oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Determination of nitrite, nitrate and total nitrogen in vegetable samples  [cached]
Manas Kanti Deb,Manisha Thakur,Pushpa Khande
Bulletin of the Chemical Society of Ethiopia , 2007,
Abstract: Yellow diazonium cation formed by reaction of nitrite with 6-amino-1-naphthol-3-sulphonic acid is coupled with β-naphthol in strong alkaline medium to yield a pink coloured azo dye. The azo-dyes shows absorption maximum at 510 nm with molar absorptivity of 2.5 ×104 M-1 cm-1. The dye product obeys Beer's law (correlation coefficient = 0.997), in terms of nitrite concentration, up to 2.7 μg NO2 mL-1. The above colour reaction system has been applied successfully for the determination of nitrite, nitrate and total nitrogen in vegetable samples. Unreduced samples give direct measure for nitrite whilst reduction of samples by copperized-cadmium column gives total nitrogen content and their difference shows nitrate content in the samples. Variety of vegetables have been tested for their N-content (NO2-/NO3-/total-N) with % RSD ranging between 1.5 to 2.5 % for nitrite determination. The effects of foreign ions in the determination of the nitrite, nitrate, and total nitrogen have been studied. Statistical comparison of the results with those of reported method shows good agreement and indicates no significant difference in precision.
Determination of Nitrate and Nitrite Contents of Syrian White Cheese  [PDF]
Mohammad Amer Zamrik
Pharmacology & Pharmacy (PP) , 2013, DOI: 10.4236/pp.2013.42024
Abstract: The levels of nitrate and nitrite were determined in 102 samples of Syrian white cheese which represents the major production of total cheeses, manufactured mainly from cow’s milk and sheep’s milk in a less degree. Determination of nitrate and nitrite levels has been made by spectrophotometric method. The results for nitrate in cow’s and sheep’s milk cheeses reveal an average of 5.10 and 6.25 mg/kg, respectively. The results for nitrite in cow’s and sheep’s milk cheese were found to contain 1.24 and 1.31 mg/kg as an average, respectively. Several factors can play a role in the interpretation of the high nitrate content, such as livestock nutrition by forge with high nitrate load and water contaminated with nitrogen fertilizer and domestic effluents, primitive production techniques in many cases, and adding nitrate salts to prevent the growth of gas-producing bacteria caused by failing in the hygienic conditions. There is a necessity to apply strict controls to reduce the presence of these two anions in the Syrian white cheese.
Impacts of Nitrate and Nitrite on Physiology of Shewanella oneidensis  [PDF]
Haiyan Zhang, Huihui Fu, Jixuan Wang, Linlin Sun, Yaoming Jiang, Lili Zhang, Haichun Gao
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0062629
Abstract: Shewanella oneidensis exhibits a remarkable versatility in anaerobic respiration, which largely relies on its diverse respiratory pathways. Some of these are expressed in response to the existence of their corresponding electron acceptors (EAs) under aerobic conditions. However, little is known about respiration and the impact of non-oxygen EAs on the physiology of the microorganism when oxygen is present. Here we undertook a study to elucidate the basis for nitrate and nitrite inhibition of growth under aerobic conditions. We discovered that nitrate in the form of NaNO3 exerts its inhibitory effects as a precursor to nitrite at low concentrations and as an osmotic-stress provider (Na+) at high concentrations. In contrast, nitrite is extremely toxic, with 25 mM abolishing growth completely. We subsequently found that oxygen represses utilization of all EAs but nitrate. To order to utilize EAs with less positive redox potential, such as nitrite and fumarate, S. oneidensis must enter the stationary phase, when oxygen respiration becomes unfavorable. In addition, we demonstrated that during aerobic respiration the cytochrome bd oxidase confers S. oneidensis resistance to nitrite, which likely functions via nitric oxide (NO).
Survey of Nitrate and Nitrite Levels of Fresh Vegetables in Turkey
Aylin Ayaz,Ali Topcu,Mine Yurttagul
Journal of Food Technology , 2013,
Abstract: In this study, the nitrate and nitrite contents of a total 258 samples of 7 different vegetables (tomato, carrot, head lettuce, leaf lettuce, iceberg, parsley and spinach) sold in Ankara markets in Turkey were determined during the period of 6 months. These vegetables are supposed to provide the major contribution to the intake of nitrate from the diet. Nitrite was estimated spectrophotometrically and nitrate after reduction to nitrite with cadmium column. The highest content of nitrate was found in parsley (1513.36 mg kg 1) followed by spinach (1456.04 mg kg 1), crisphead lettuce (1042.81 mg kg 1), butterhead lettuce (914.22 mg kg 1), iceberg (623.38 mg kg 1), carrot (190.03 mg kg 1) and tomato (11.06 mg kg 1). The mean nitrite values of spinach, parsley, crisphead lettuce, iceberg, butterhead lettuce, carrot and tomato were determined as 2.31, 1.78, 0.98, 0.92, 0.84, 0.65 and 0.36 mg kg 1 in fresh weight, respectively.
DETERMINATION OF NITRITE, NITRATE AND TOTAL NITROGEN IN VEGETABLE SAMPLES
Manas Kanti Deb, Manisha Thakur, Pushpa Khande
Bulletin of the Chemical Society of Ethiopia , 2007,
Abstract: Yellow diazonium cation formed by reaction of nitrite with 6-amino-1-naphthol-3-sulphonic acid is coupled with β-naphthol in strong alkaline medium to yield a pink coloured azo dye. The azo-dyes shows absorption maximum at 510 nm with molar absorptivity of 2.5 ×104 M-1 cm-1. The dye product obeys Beer\'s law (correlation coefficient = 0.997), in terms of nitrite concentration, up to 2.7 μg NO2 mL-1. The above colour reaction system has been applied successfully for the determination of nitrite, nitrate and total nitrogen in vegetable samples. Unreduced samples give direct measure for nitrite whilst reduction of samples by copperized-cadmium column gives total nitrogen content and their difference shows nitrate content in the samples. Variety of vegetables have been tested for their N-content (NO2-/NO3-/total-N) with % RSD ranging between 1.5 to 2.5 % for nitrite determination. The effects of foreign ions in the determination of the nitrite, nitrate, and total nitrogen have been studied. Statistical comparison of the results with those of reported method shows good agreement and indicates no significant difference in precision. KEY WORDS: Yellow diazonium cation, 6-Amino-1-naphthol-3-sulphonic acid, Vegetables, Nitrite in vegetables, Nitrate in vegetables, Total nitrogen in vegetables Bull. Chem. Soc. Ethiop. 2007, 21(3), 445-450.
Determination of nitrate and nitrite content of Turkish cheeses
A Top u, AA Top u, I Saldamli, M Yurttagül
African Journal of Biotechnology , 2006,
Abstract: The levels of nitrate and nitrite were determined in 185 samples of Turkish cheese having high consumption rate. All cheese samples contained nitrate and its level in Turkish white cheese produced from cow’s and sheep’s milk were found between 0.92 - 22.40 (mean 8.96±4.93) mg/kg and 0.47 - 23.68 (mean 12.35±6.28) mg/kg, respectively. Nitrate level in fresh kasar cheese and mature kasar cheese samples were 0.68 - 17.19 (mean 8.97±5.03) mg/kg and 1.76 - 13.31 (mean 9.45±4.03) mg/kg, respectively. Nitrite was detected 88.11% of cheese samples and mean nitrite values were found between 0.88- 1.64 mg/kg. The highest levels of nitrate and nitrite were determined in the Turkish white cheese samples produced from sheep’s milk. The nitrate content of the examined samples of Turkish cheese could be attributed to both external sources such as contamination by nitrate fertilizers, forage, and agricultural drinking water and addition of nitrate to the cheese milk. It is suggested that stricter control of nitrate in cheese is necessary, and that it should not be used to mask poor hygienic conditions during manufacturing. Hygienic condition must be kept at excellent level in related industries
Improvement of nitrate and nitrite reduction rates prediction
Estuardo,Carolina; Martí,M. Cristina; Huili?ir,César; Aspé Lillo,Estrella; Roeckel von Bennewitz,Marlene;
Electronic Journal of Biotechnology , 2008,
Abstract: reported models of denitrification rates integrate in an unique parameter the ph-dependent inhibition by hno2 and the ph effect on the bacterial metabolic activity; furthermore, they do not quantify separately the ph effect on the nitrate and on the nitrite reduction rates. the goal of this work was to quantify both effects on the kinetics of nitrate and nitrite reduction to improve the models’ predictive value. assays were performed at a ph range of 6.5-9.0 in batch reactors at 37oc with an activated sludge. at the studied ph range and at below the hno2 inhibitory concentration (0.004 mg l-1), the maximum nitrate reduction rate diminished 23% and 50% by decreasing or increasing, respectively, one ph unit from 8.0. the maximum nitrite reduction at ph 8.0 diminished 15% at ph 7.0 and 40% at ph 9.0. at hno2 concentrations over the inhibitory concentration, except at ph > 8.0, the maximum nitrate reduction rate diminished 50% upon decreasing the ph from 8.0 to 7.0 or increasing it from 8.0 to 9.0. inclusion of the ph effect in the reported models improved their predictive value; average deviations from the experimental data were reduced from 53% to 10.7% or 33.8% to 10.5% for nitrite and nitrate reduction rates, respectively.
The Evaluation of Serum Nitrite, Nitrate and Malonyldialdehyde Levels in Smokers
Rostami, M,Jorfi, M
Medical Laboratory Journal , 2010, DOI: http://www.goums.ac.ir/mljgoums/index.php?slc_lang=en&sid=1
Abstract: Background and objectives: Smokers are exposed to significantquantities of ROS (Reactive Oxygen Species); and The Level of NitricOxide (NO), the primary vasodilator produced by endothelial cells, ischanged by cigarette smoking. Cigarette smoking is associated withimpaired endothelium-dependent vasodilatation and cardiovasculardisease (CVD). The aim of this study is to determine the level of serumnitrite, nitrate and malondialdehyde (MDA) levels in smokers.Material and Methods: In this descriptive analytical study, 60 healthymale smokers and 60 male non-smokers (control group) were selected bya Purposive sampling and then serum levels of nitrite, nitrate and MDAin all patients were determined and compared to together.Results: Serum nitrite and nitrate level in smokers are 10.4±3.1 and19.6±5.9 and in non-smokers is 14.6±4.4 and 29.3±6.7 (p<0.00001)μmol/L, respectively. The results show that smokers’ are significantlylower than non-smokers’. Serum MDA level in smokers (11.7±2.6μmol/L) is significantly higher (p<0.00001) than non-smokers (8.3±1.9μmol/L).Conclusion: Based on the results, serum level of nitrite and nitrate arelower and MDA is higher in smokers. This difference can be related toCVD in smokers.Keywords: Smokers, Non-smokers, Nitrite, Nitrate, Malodialdehyde(MDA), cardiovascular disease (CVD).
Autotrophic denitrification for nitrate and nitrite removal using sulfur-limestone

Zhou Weili,Sun Yejue,Wu Bingtao,Zhang Yue,Huang Min,Miyanaga Toshiaki,Zhang Zhenjia,

环境科学学报(英文版) , 2011,
Abstract: Sulfur-limestone was used in the autotrophic denitrification process to remove the nitrate and nitrite in a lab scale upflow biofilter. Synthetic water with four levels of nitrate and nitrite concentrations of 10, 40, 70 and 100 mg N/L was tested. When treating the low concentration of nitrate- or nitrite-contaminated water (10, 40 mg N/L), a high removal rate of about 90% was achieved at the hydraulic retention time (HRT) of 3 hr and temperature of 20–25°C. At the same HRT, 50% of the nitrate or nitrite could be removed even at the low temperature of 5–10°C. For the higher concentration nitrate and nitrite (70, 100 mg N/L), longer HRT was required. The batch test indicated that influent concentration, HRT and temperature are important factors affecting the denitrification efficiency. Molecular analysis implied that nitrate and nitrite were denitrified into nitrogen by the same microorganisms. The sequential two-step-reactions from nitrate to nitrite and from nitrite to the next-step product might have taken place in the same cell during the autotrophic denitrification process.
Nitrate and Nitrite Levels of Natural Spring and Mineral Water in Van, Turkey
Nurhayat Atasoy,Suleyman Alemdar,Ufuk Mercan,Sema Agaoglu
Journal of Animal and Veterinary Advances , 2012, DOI: 10.3923/javaa.2011.352.355
Abstract: This study was performed to determine nitrate and nitrite levels of packaged natural spring and mineral water consumed in Van city of Turkey. A total of 200 water samples, belonging to 10 different companies, each of 100 pet spring water and 100 bottled mineral water samples were used as material. Nitrate and nitrite levels were measured by the spectrophotometric method. According to the results both nitrate and nitrite were found to be present in all water samples. Mean nitrate and nitrite concentrations were 3.66±0.028 and 0.045±0.003 mg L-1 in the spring water and 3.52±0.011 and 0.025±0.001 mg L-1 in the mineral water, respectively. Finally; nitrate and nitrite levels in water samples were in accordance with the related national and international regulations and considered safe for consuming.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.