The determination method of total nitrogen in urban domestic waste is still blank in my country's sanitation industry. Various provinces and cities only refer to the analysis methods of soil or water quality during monitoring and analysis. Since the comprehensive and harmless treatment research of domestic waste requires understanding of the characteristics and components of domestic waste, this standard combines the current analysis methods in environmental monitoring and soil physical and chemical testing, and conducts comparative experiments and verification experiments in the laboratory to further modify and improve the analysis methods in view of the complexity and instability of domestic waste components, and compiles the determination method of total nitrogen in urban domestic waste. This standard specifies the method for determining total nitrogen using the semi-micro Kelvin method. This standard is applicable to the determination of urban domestic waste samples. CJ/T 103-1999 Determination of total nitrogen in urban domestic waste Semi-micro Kelvin method CJ/T103-1999 Standard download decompression password: www.bzxz.net

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Town Construction Industry Standard of the People's Republic of China CJ/T103—1999
Municipal Domestic Waste
Determination of Total Nitrogen
Semi-micro Kelvin Method
Municipal domestic refuseDetermination of total nitrogenSemi-microKjeldahlmethod
1999-11-24 Issued
2000-06-01 Implementation
Issued by the Ministry of Construction of the People's Republic of China
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CJ/T103—1999
The determination method of total nitrogen in urban domestic waste is still blank in my country's sanitation industry. In monitoring and analysis, provinces and cities only refer to the analysis methods of soil or water quality. Since the comprehensive utilization and harmless treatment of domestic waste research work requires understanding of the characteristics and components of domestic waste, this standard combines the current analysis methods in environmental monitoring and soil physical and chemical testing, and conducts comparative experiments and verification experiments in the laboratory to further modify and improve the analysis method in view of the complexity and instability of domestic waste components. The determination method of total nitrogen in urban domestic waste is compiled. This standard was proposed by the Standard and Quota Research Institute of the Ministry of Construction. This standard is under the jurisdiction of the Shanghai Municipal Environmental Sanitation Administration, the technical unit responsible for urban environmental sanitation standards of the Ministry of Construction.
This standard was drafted by the Tianjin Environmental Sanitation Engineering Design Institute. The main drafters of this standard are Han Zhimei and Zhang Fan. This standard is entrusted to the Tianjin Environmental Sanitation Engineering Design Institute for interpretation. Engineering Construction Standard Full-text Information System
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Urban Construction Industry Standard of the People's Republic of China Municipal Domestic Refuse
Determination of total nitrogen
Semi-micro Kjeldahl method
Municipal domestic refuseDetermination of total nitrogenSemi-micro Kjeldahl method
1Scope
CJ/T103—1999
This standard specifies the method for determining total nitrogen using the semi-micro Kjeldahl method. This standard is applicable to the determination of municipal domestic waste samples. 2
Cited standards
The clauses contained in the following standards constitute the clauses of this standard through reference in this standard. When this standard was published, the versions shown were valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest versions of the following standards. CJ/T3039—1995 Sampling and physical analysis methods for urban domestic waste 3 Collection and preparation of samples
3.1 The collection and preparation of samples shall be carried out in accordance with the provisions of CJ/T3039 to meet the specified 4-(1)b drying sample standard, and the processing process shall not exceed 24 hours. 3.2 The moisture content of urban domestic waste shall be determined in accordance with the provisions of C/T3039 to prepare for the conversion of sample measurement results.
3.3 The storage of samples shall be carried out in accordance with the provisions of CJ/T3039. Approved by the Ministry of Construction of the People's Republic of China on November 24, 1999, and implemented on June 1, 2000. Engineering Construction Standards Full Text Information System
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4 Principle
When the sample is digested with concentrated sulfuric acid in the presence of a catalyst (i.e. a mixture of potassium sulfate, anhydrous copper sulfate and selenium powder), various nitrogen-containing organic compounds undergo a complex high-temperature decomposition reaction and are converted into ammonium nitrogen. The ammonia distilled from the alkalization is absorbed by boric acid and titrated with an acid standard solution to calculate the total nitrogen content of the domestic waste (excluding all nitrate nitrogen 2. Using the reduction method and The non-reduction method is used to determine the nitrogen content of domestic waste, and the results are very close. Therefore, the Kelvin method is scientific and effective for the determination of total nitrogen in domestic waste samples. 5 Reagents
The distilled water used in this experiment is ammonia-free, and all reagents used without specified specifications are analytically pure.
5.1 Concentrated sulfuric acid, p=1.84g/mL.
5.2 Concentrated hydrochloric acid, p=1.19g/mL.
5.3 Anhydrous sodium carbonate (Na, Cog) standard reagent, must be dried at 180℃ for 2h before use and constant weight.
5.42% boric acid absorption solution (m/V).
5.540% sodium hydroxide solution (m/V).
5.60.02mol/L hydrochloric acid standard solution.
Put 16.7mL of hydrochloric acid in a 100mL volumetric flask, dilute to the mark with distilled water and shake well. This solution is a 2.0mol/L hydrochloric acid solution. Pipette 10.0mL of this solution in a 1000mL volumetric flask, dilute to the mark with distilled water and shake well. Then calibrate with anhydrous sodium carbonate (5.3).
Calibration: Accurately weigh 0.0200g (accurate to 0.0001g) of dried anhydrous sodium carbonate, put it in a conical flask, add 25mL of freshly boiled and cooled distilled water and 2 drops of indicator (5.7), and titrate with 0.02mol/L hydrochloric acid standard solution until the solution changes from green to light purple. Record the volume of the hydrochloric acid standard solution consumed, and calculate the concentration of the hydrochloric acid standard solution according to formula (1). The calibration result needs to be averaged using duplicate samples, and a blank experiment should be performed at the same time. 2
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m×1000×2
106X（VV）
0.053X（VV)
Wherein: ——
-Concentration of hydrochloric acid standard solution, mol/L; ——Weigh the mass of anhydrous sodium carbonate, g;
VThe volume of hydrochloric acid standard solution consumed by the sample, mL; V. ——The volume of hydrochloric acid standard solution consumed by the blank sample, mL; 2—The number of moles of hydrochloric acid required to neutralize 1 mol of anhydrous sodium carbonate; 106—The molar mass of anhydrous sodium carbonate, g/mol. The result should be expressed to four decimal places.
7 Methyl red-bromocresol green indicator
Weigh 0.3g bromocresol green and 0.2g methyl red (accurate to 0.01g) in a mortar, add a small amount of 95% ethanol and grind until the indicator is completely dissolved, dilute to 100mL with 95% ethanol, and store for one month.
5.8 Catalyst: Weigh 100g potassium sulfate, 10g copper sulfate pentahydrate (CuSO, 5HO) and 1g selenium powder in a mortar, grind and mix thoroughly, and store in a ground-mouth bottle.
6 Instruments
a) Analytical balance, sensitivity 0.0001g; b) Porcelain mortar;
c) Hard Kelvin flask, volume 500mL; d) Semi-micro nitrogen distillation apparatus;
e) Semi-micro burette, volume 5mL;
f) Conical flask, volume 150mL;
g) Quadruple adjustable electric furnace.
7 Operation steps
Digestion of sample
7.1.1 Weigh about 0.5g sample (accurate to 0.0001g) and put it into the bottom of a dry 500mL3
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Kjergler flask, add a small amount of distilled water to moisten the sample, add 2g catalyst (5.8) and 5mL concentrated sulfuric acid, shake the spoon, cover the flask with a small funnel, and place it on a thermostatic electric stove for low-temperature heating. When the reaction in the flask is moderate (about 30min), increase the temperature appropriately to keep the solution slightly boiling. The temperature should not be too high, and it is appropriate for the sulfuric acid vapor to condense and reflux at the upper 1/3 of the bottleneck. After the digestion solution has completely turned grayish white with a slight green color, continue digestion for 1h, stop heating and let it cool. 7.1.2 Transfer all the above-mentioned cooled digestion solution to a 50mL volumetric flask, and wash the Kelvin flask with a small amount of distilled water for 4 to 5 times and transfer it to the volumetric flask, adjust the volume, shake the spoon, and let it stand to obtain supernatant A.
7.2 Distillation of ammonia
7.2.1 Install the distillation device, see the device diagram, add a few glass beads to the round-bottom flask, and check whether it is leaking. Use distilled water instead of the sample for blank distillation, and clean the pipe with the water distillate (about 30 minutes). Kelvin Inquiry Apparatus
Semi-micro Kelvin Nitrogen Determination Apparatus Diagram
Figure Lianshao Le
7.2.2 Add 20mL of boric acid absorption solution (5.4) to a 150mL conical flask, and add 2 drops of indicator (5.7) Place the end of the condenser tube of the distillation device 4
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1cm below the absorption liquid surface, then draw 25mL of supernatant A into the distillation chamber, slowly add 10mL of sodium hydroxide solution, start the steam generator, and perform steam distillation. When the volume of the distillate is about 50mL, the distillation is completed when the distillate is neutral as measured by pH test paper, and wash the end of the condenser tube with a small amount of boric acid absorption liquid.
7.2.3 Titrate the distillate with the calibrated hydrochloric acid standard solution (5.6), and the solution changes from green to light purple. Record the volume of the hydrochloric acid standard solution used. 7.3 Blank experiment
The blank experiment is carried out simultaneously with the sample determination. Except for not adding the sample, the other operation steps are the same as the sample determination. The volume of the hydrochloric acid standard solution consumed by the blank should generally not exceed 0.1mL.
Description of analysis results
Total nitrogen concentration c(%2 is calculated according to formula (2):
(VV)cX14.01X2
1000×mm
V is the volume of the standard hydrochloric acid solution used to titrate the sample, mL; where:
............
V is the volume of the standard hydrochloric acid solution used to titrate the blank, mL;-the concentration of the standard hydrochloric acid solution, mol/L; Co
2——multiple times of fractionation,
mass of the sample, 83
14.01——nitrogen The molar mass of an atom, g/moL. The result should be expressed to four decimal places.
Precision and Accuracy
Three batches of samples were measured continuously in the laboratory, and three parallel samples were made for each batch. The nitrogen content was measured to be 0.3324%~0.3333%, and the relative standard deviation was <2.1%. Disodium ethylenediaminetetraacetate (CHN,O.Naz·2HO, referred to as EDTA) was used as the standard substance. 0.05g of the standard substance was added to 0.5g of the sample, and the spike recovery rate was measured to be 94.5%~99.3%. 5
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