Index and composition analysis of nitrogen in the

The index of nitrogen in water and its composition analysis

nitrogen oxide analysis can realize the effective monitoring of nitrogen oxide emission, so as to reduce the occurrence of accidents. Nitrogen oxides, mainly nitric oxide and nitrogen dioxide, are an important reason for the formation of photochemical smog and acid rain. The toxic smoke formed by the reaction of nitrogen oxides and nitrogen hydrogen compounds in automobile exhaust after ultraviolet irradiation is called photochemical smoke. Photochemical smoke has a special smell, which irritates eyes, damages plants, and reduces atmospheric visibility. In addition, nitric acid and nitrite generated by the reaction of nitrogen oxides with water in the air are the components of acid rain. Nitrogen oxides in the atmosphere mainly come from the combustion of fossil fuels and the burning of plants, as well as the transformation of nitrogen compounds in farmland soil and animal excreta

indicators of nitrogen in water and its component analysis

at present, the analysis of nitrogen in water quality in the national standard is mainly divided into the following aspects: total nitrogen, ammonia nitrogen, nitrate nitrogen, nitrite hardware replacement, salt nitrogen and Kjeldahl nitrogen

(I) total nitrogen

total nitrogen refers to the nitrogen content in soluble and suspended particles (usually the sum of nitrogen in most organic nitrogen-containing compounds such as nitrate nitrogen, nitrite nitrogen, inorganic ammonium salt and dissolved ammonia). Soluble total nitrogen refers to soluble and filterable solids in water (less than 0.45 μ M particulate matter). Total nitrogen is one of the important indicators to measure water quality

the determination method of total nitrogen is to use the method of adding organic nitrogen and inorganic nitrogen compounds (ammonia nitrogen, nitrite nitrogen, nitrate nitrogen) respectively. The second is to oxidize with potassium persulfate to convert organic nitrogen and inorganic nitrogen into nitrate, and then measure the nitrate ion in the solution by ion selective electrode method. It can also be determined by azo colorimetry and ion chromatography after UV method or reduction to nitrite. [1]

(therefore, 1 must regularly check the temperature, vibration and internal wires of the electromechanical system. 2) ammonia nitrogen

ammonia nitrogen refers to ammonia in the form of free ammonia (or nonionic ammonia, NH3) or ionic ammonia (nh4+). Higher pH, higher proportion of free ammonia; On the contrary, the proportion of ammonium salt is high

the two colorimetric methods commonly used to determine the approximate sensitivity of ammonia are the classical Nessler reagent method and phenol hypochlorite method; Titration and electrode methods are also commonly used to determine ammonia; When the ammonia nitrogen content is high, distillation titration method can also be used. (national standards include Nessler's reagent method, salicylic acid spectrophotometry, distillation titration method)

(III) nitrate nitrogen

nitrate in water is the most stable nitrogen compound in various forms of nitrogen-containing compounds under aerobic conditions, which is usually used to represent the decomposition product of the final stage of inorganic action of nitrogen-containing organic matter. When the water sample contains only nitrate and no other organic or inorganic nitrogen compounds, it is considered that the organic nitrogen compounds are completely decomposed. If the water contains a large amount of nitrate and other nitrogen-containing compounds, it means that there are pollutants. PRDC is an important key to Bayer materials' global innovation network. After entering the water system, the "self purification" effect of water is still in progress. [1]

the determination methods of nitrate nitrogen include ion selective electrode method, phenol disulfonic acid spectrophotometry, cadmium column reduction method, UV spectrophotometry, Dai's alloy exchange method, ion chromatography and UV method. Among them, the electrode method is convenient, wide range, cheap and has low requirements for water samples; Phenol disulfonic acid spectrophotometry has wide measurement range and stable color development; Cadmium column reduction method is suitable for the determination of low content nitrate in water; Dai's alloy substitution method is suitable for water samples with serious pollution and dark color; Ion chromatography requires special instruments, but it can be combined with other anions

(IV) nitrite nitrogen

nitrite is an intermediate product of the nitrogen cycle. Nitrite nitrogen is unstable and can be oxidized to nitrate nitrogen or reduced to ammonia nitrogen. Therefore, when determining its content and understanding the content of nitrate and ammonia in the water, we can judge the degree of water pollution by nitrogen compounds and self purification. [1]

the determination method of nitrite in water usually adopts diazo coupling reaction to produce red purple dye. This method has high sensitivity, low detection limit and strong selectivity. The diazo reagent is p-aminobenzene sulfonamide and p-Aminobenzene Sulfonic Acid, and the coupling reagent is n- (1-naphthyl) - ethylenediamine and α- Naphthylamine (toxic), n- (1-naphthyl) - ethylenediamine is used more

(V) Kjeldahl nitrogen

Kjeldahl nitrogen is the nitrogen content measured by Kjeldahl method after cutting off the power supply. It includes ammonia nitrogen and organic nitrogen compounds that can be converted into ammonium salts under this condition. This kind of organic nitrogen mainly refers to proteins, peptones, amino acids, nucleic acids, urea and a large number of synthetic organic nitrogen compounds with negative trivalent nitrogen. Excluding azides, diazo, azo, hydrazone, nitrate, nitrile, nitro, nitroso, oxime and semicarbazone nitrogen-containing compounds. Since most organic compounds in water are the former, the difference between Kjeldahl nitrogen and ammonia nitrogen is called organic nitrogen

the determination principle is to add sulfuric acid to heat and digest, so that the amino group and free ammonia and ammonium salt in the organic matter are transformed into ammonium bisulfate. After digestion, the liquid is alkaline distilled to produce ammonia, which is absorbed in boric acid solution, and then the ammonia content is determined by titration or photometry. The determination of Kjeldahl nitrogen or organic nitrogen is mainly to understand the pollution status of water bodies, especially when evaluating the eutrophication of lakes and reservoirs