F.I.B 4. Hydrogen, oxygen, nitrogen from
these substances
O Inorganic substances
O Physical solutes
O
Organic substances
O None of the above
Answers
Answer:
Organic nitrogen-containing compounds have many important roles in nature. They display an enormous structural diversity, in which nitrogen atoms can form part of simple functional groups or complex heterocyclic systems; they also have varying degrees of substitution and oxidation. The most noteworthy of these naturally occurring molecules are proteins, and most vitamins and hormones.
Nitrogen compounds can be classified as mineral or organic. Mineral compounds are essentially formed by the ammonium ion (NH4+), which is generated when ammonium salts are dissolved in water. Organic compounds, in contrast, are carbon and hydrogen
TABLE 12.1. Nitrogen Fractions of Interest in Winemaking
FractionCompoundsUse by MicroorganismsInorganic nitrogenAmmonia and ammonium: NH3 and NH4+Easily assimilatedOrganic nitrogenAmino acids with a molecular mass of <200 DaPolypeptides with a molecular mass of 200–10,000 Da.Non-assimilableProteins with a molecular mass of >10,000 Da
compounds that contain a nitrogen atom. All organic nitrogen-containing compounds can be considered as derivatives of ammonia in which one or more hydrogen atoms are substituted by hydrocarbon radicals. Of particular interest in this group are α-amino acids and their peptide and protein derivatives.
Another classification system, which is of more interest in winemaking, is based on how nitrogen compounds are used by microorganisms; that is, it distinguishes between assimilable and non-assimilable compounds. Examples of the former are the ammonium ion and free amino acids, and examples of the latter are peptides and proteins.
Must made from ripe grapes contains approximately 200 to 500 mg/L of total nitrogen, which is higher than the levels found in wine. Compared to white wine, red wine made by macerating on the skins has higher concentrations of low-molecular-weight nitrogen compounds but lower concentrations of proteins, as these interact with coloring matter, and settle at the bottom of fermentation tanks. The nitrogen content of both red and white wine is equivalent to approximately 20% dry extract, which corresponds to 70 to 700 mg/L of elemental nitrogen and 0.5 to 4 g/L of protein-derived nitrogen. The factor used to convert elemental nitrogen to protein nitrogen is 6.25.
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Water Analysis | Sewage☆
Carlos Bendicho, Isela Lavilla, in Encyclopedia of Analytical Science (Third Edition), 2019
Nitrogen-Containing Species
Nitrogen compounds must be monitored because it they can critically affect to aquatic ecosystems, in specially their high levels can cause eutrophication under certain conditions. Ammonia, organic species, nitrates and nitrites can be present in wastewaters. In general, ammonia and organic species are the most common in raw water and STP effluents contain mainly ammonia and nitrates. Ammonia is the initial product of the decay of nitrogenous organic wastes, its presence being an indication of such wastes. It originates from the deamination of nitrogen-containing organics and the hydrolysis of urea. The nitrate content in waters is usually low but can rise to appreciable levels in farming wastewater as a result of soil fertilization. Usually nitrites are present in very low concentration since these are rapidly oxidized to nitrates, while nitrite can be found in wastewaters from the microbiological reduction of nitrate or the oxidation of ammonia. Ammonia is usually determined by distillation and subsequently spectrophotometry (using automatized systems based in flow injection analysis or sequential injection), titrimetry, or potentiometry (adapted ion selective electrodes are used for continuous monitoring of ammonium in effluents). The TKN method is used to determine both organic nitrogen and ammonia (by acid digestion organic species are converted in ammonia). Organic nitrogen can be determined after distillation of ammonia by TKN method, so ammonia can be estimated by difference. Automatic and semi-automatic Kjeldahl analyzers can be used. Nitrite is usually determined spectrophotometrically using the Griess reaction and nitrate is determined by the same method after prereduction to nitrite (flow or sequential injection systems are also used). Nitrate can be also determined on-line by using an ion selective electrode. Optical sensors are available for nitrate and nitrite (some of these sensors are capable of determining simultaneously other relevant parameters). The determination of predominant species of nitrogen in water can provide additional information on water pollution stages, that is first, ammonia is produced by oxidation of organic nitrogen, nitrite is produced as an intermediate in the ammonia oxidation and finally nitrite is oxidized to nitrate.
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Bioactive Natural Products
Shu-Hua Qi, in Studies in Natural Products Chemistry, 2012