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HJ 658-2013: Soil. Determination of organic carbon. Combustion oxidation-titration method
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Soil. Determination of organic carbon. Combustion oxidation-titration method
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HJ 658-2013
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Basic data | Standard ID | HJ 658-2013 (HJ658-2013) | | Description (Translated English) | Soil. Determination of organic carbon. Combustion oxidation-titration method | | Sector / Industry | Environmental Protection Industry Standard | | Classification of Chinese Standard | Z18 | | Classification of International Standard | 13.080 | | Word Count Estimation | 10,127 | | Quoted Standard | HJ/T 166; HJ/T 613 | | Regulation (derived from) | Department of Environmental Protection Notice No. 50 of 2013 | | Issuing agency(ies) | Ministry of Ecology and Environment | | Summary | This standard specifies: Determination of soil organic carbon burning oxidation titration. This standard applies to: soil organic carbon Determination, does not apply to oil sludge contaminated soil organic carbon determination. When the sample size is 0. | HJ 658-2013: Soil. Determination of organic carbon. Combustion oxidation-titration method---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Soil.Determination of organic carbon.Combustion oxidation-titration method
National Environmental Protection Standard of the People's Republic
Determination of soil organic carbon - combustion oxidation - titration
Soil - Determination of organic carbon – Combustion oxidation- titration
Method
Published on.2013-08-16
2013-09-01 Implementation
Ministry of Environmental Protection released
Content
Preface II
1 Scope.1
2 Normative references 1
3 principle of the method.1
4 interference and elimination..1
5 reagents and materials..1
6 instruments and equipment..2
7 sample 2
8 Analysis steps.3
9 Calculation and representation of results 3
10 precision and accuracy..4
11 Quality Assurance and Quality Control 4
12 Disposal of waste.4
13 Notes 4
Foreword
To implement the "Environmental Protection Law of the People's Republic of China", protect the environment, protect human health, and regulate organic carbon in soil
The method of determination is to develop this standard.
This standard specifies the combustion oxidation-titration method for the determination of organic carbon in soil.
This standard is the first release.
This standard was formulated by the Science and Technology Standards Department of the Ministry of Environmental Protection.
This standard is mainly drafted by. Dalian Environmental Monitoring Center.
This standard is verified by. Anshan Environmental Monitoring Center Station, Jinzhou Environmental Monitoring Center Station, and Yingkou City Environmental Monitoring
Xinzhan, Fushun Environmental Monitoring Center Station, Changchun Environmental Monitoring Center Station, Harbin Environmental Monitoring Center Station.
This standard was approved by the Ministry of Environmental Protection on August 16,.2013.
This standard has been implemented since September 1,.2013.
This standard is explained by the Ministry of Environmental Protection.
Determination of soil organic carbon - combustion oxidation - titration
1 Scope of application
This standard specifies the combustion oxidation-titration method for the determination of organic carbon in soil.
This standard applies to the determination of organic carbon in soil, and is not applicable to the determination of organic carbon in sludge-contaminated soil.
When the sample amount is 0.50 g, the detection limit of this method is 0.004%, the lower limit of determination is 0.016%, and the upper limit of measurement
It is 4.00%. When the organic carbon content in the sample is high, the sampling amount can be reduced, but the minimum can not be less than 0.050 g.
2 Normative references
The contents of this standard refer to the following documents or their terms. For undated references, the valid version is appropriate.
Used in this standard.
HJ/T 166 Technical Specifications for Soil Environmental Monitoring
HJ/T 613 Determination of dry matter and moisture in soils - Gravimetric method
3 Principle of the method
The air-dried soil sample is heated to more than 900oC in a furnace, and the organic carbon in the sample is oxidized to carbon dioxide.
The carbon dioxide is absorbed by an excess of cesium hydroxide solution to form a cerium carbonate precipitate, and the remaining cerium hydroxide after the reaction is dissolved with oxalic acid.
The droplet is determined, and the volume difference of the oxalic acid standard solution consumed by the blank titration and the sample titration is used to calculate the carbon dioxide generation, according to the dioxin.
The amount of carbon produced is used to calculate the organic carbon content in the soil.
4 interference and elimination
When the sample is heated above.200 °C, all carbonates are completely decomposed to produce carbon dioxide.
Positive interference is generated and can be removed by adding an appropriate amount of hydrochloric acid.
Carbon dioxide in the air produces a positive interference equivalent to 0.2% organic carbon, which is removed by subtracting the blank.
5 reagents and materials
Unless otherwise stated, analytically pure reagents that meet national standards were used for the analysis.
5.1 Carbon dioxide-free water. It is ready for use, and the conductivity is ≤0.2 mS/m (25°C).
5.2 Concentrated hydrochloric acid. ρ(HCl) = 1.19 g/ml.
5.3 n-butanol. φ (C4H9OH) ≥ 99.0%.
5.4 Ethanol. φ(C2H5OH) = 95%.
5.5 Oxalic acid (H2C2O4·2H2O). a reference reagent.
5.6 hydrochloric acid solution. c (HCl) = 4 mol/L
Measure 340 ml of concentrated hydrochloric acid (5.2), slowly pour into 500 ml of water (5.1) while stirring, and dilute with water (5.1) until
Mix 1000 ml.
5.7 Barium hydroxide (Ba(OH)2·8H2O).
5.8 Barium chloride (BaCl2·2H2O).
5.9 Barium hydroxide absorption solution I. ρ [Ba(OH)2]=1.40 g/L
Weigh 1.40 g of barium hydroxide (5.7) and 0.08 g of barium chloride (5.8) dissolved in 800 ml of water (5.1) and add 3 ml.
N-butanol (5.3), dilute to 1000 ml with water (5.1), and mix.
5.10 Barium hydroxide absorption liquid II. ρ [ Ba(OH) 2] = 2.80 g/L
Weigh 2.80 g of barium hydroxide (5.7) and 0.16 g of barium chloride (5.8) dissolved in 800 ml of water (5.1) and add 3 ml.
N-butanol (5.3), dilute to 1000 ml with water (5.1), and mix.
Note. After the above two kinds of absorbing liquids are prepared, they are sealed and stored, and placed for 1 d to precipitate.
5.11 Oxalic acid standard solution. ρ(H2C2O4·2H2O)=0.5637 g/L
Weigh 0.5637 g of oxalic acid (5.5) dissolved in water (5.1), transfer to a 1000 ml volumetric flask, and dilute with water (5.1).
Release to the marking line and mix. 1 ml This solution is equivalent to 0.1 ml of carbon dioxide under standard conditions (101.325 kPa, 273.15 K).
Available now.
5.12 Phenolphthalein indicator
Weigh 0.5 g of phenolphthalein in 50 ml of ethanol (5.4), then add 50 ml of water (5.1) and shake well.
6 Instruments and equipment
6.1 Tube furnace. using silicon carbon tube as heating body, can heat the sample to above 900 °C, the temperature can be adjusted, the precision is 1 °C;
The high temperature zone is longer than 90 mm.
6.2 Glass Absorbent Bottle. The absorption bottle volume is 450 ml, and the diameter of the glass plate is 10 mm or more.
6.3 Magnetic stirrer. The stirring speed is about 500 r/min and it is continuously adjustable.
6.4 Ceramic boat.
6.5 Air pump.
6.6 Gas Flow Meter. A float flow meter with a needle valve with a flow range of 0 to 1.0 L/min.
6.7 Balance. Accuracy is 0.1 mg.
6.8 Oven. The temperature adjustment range is 0 ~ 250 °C.
6.9 Soil screen. 2 mm (10 mesh), 0.097 mm (160 mesh), stainless steel.
6.10 Acid burette. 50.00 ml.
6.11 Common instruments and equipment used in general laboratories.
1--air flow direction; 2--tube furnace; 3--glass plate absorption bottle; 4--magnetic stirrer; 5--exhaust pump; 6--gas flow meter
Figure 1 Schematic diagram of the tube furnace combustion and absorption device
Note. Other devices equivalent to those of Figure 1 can also be used.
7 samples
7.1 Sample collection and preservation
The collection and storage of soil samples is carried out in accordance with the relevant provisions of HJ/T 166.
7.2 Preparation of samples
Place the soil sample in the air-drying tray and spread it into a thin layer of 2 ~ 3 cm thick, first removing the residues such as plants, insects, stones, etc.
Crush the clods with iron shovel or porcelain abrasive rods, turn them several times a day, and air dry.
Mix the air-dried soil thoroughly, use the quadruple method, take two parts, one part is retained, one part is ground to all over 2 mm (10
Mesh) soil sieve. Take 10 ~ 20 g of the sieved soil sample and grind it to the entire 0.097 mm (160 mesh) soil sieve.
Load into a brown stoppered glass bottle for testing.
7.3 Determination of dry matter content
The air-dried soil samples after 2 mm (10 mesh) sieve were accurately weighed, and the dry matter content of the soil was determined by reference to HJ/T 613.
8 Analysis steps
8.1 Preparation of samples
Weigh the appropriate amount of sample (7.2) to the nearest 0.001 g, place in the ceramic boat (6.4), and slowly add hydrochloric acid solution (5.6)
The sample did not bubble out. Mix well, let stand for 4 h, then dry at 60 ~ 70 °C for 16 h, to be tested.
Note 1. The concentration and amount of hydrochloric acid solution can be determined according to the quality of the sample to be weighed and the content of carbonate. If the soil sample contains only carbonate,
5 ml of hydrochloric acid solution (5.6) can be added per 1 g of sample.
8.2 Air tightness check
Connect the tube furnace combustion and absorption device, plug the glass plate absorption bottle (6.2), open the air pump (6.5), and close the gas flow.
Meter (6.6) front valve. If the flow rate of the flowmeter is zero, the equipment is airtight.
8.3 Determination
Accurately add the supernatant of.200 ml cesium hydroxide absorption solution I (5.9) to the glass-plate absorption bottle (6.2), and plug it tightly.
In the bottle, the above-mentioned ceramic boat (6.4) containing the sample is placed in a tube furnace, and the temperature of the tube furnace (6.1) is adjusted to 900 to 1000 °C.
Open the air pump (6.5), adjust the pumping flow rate to 0.5 L/min, adjust the speed of the magnetic stirrer (6.3) to make the bubble distribution.
Evenly. The reaction time is 600±10s. After the reaction is finished, pour out all the absorption liquid in a 250 ml stoppered glass bottle.
Allow to stand for 3~4 h to complete the precipitation of cesium carbonate. Accurately measure 50 ml of the supernatant in a 250 ml Erlenmeyer flask and add 4 ~ 5
Phenolphthalein indicator (5.12), titrated with oxalic acid standard solution (5.11) until the solution turns from red to colorless.
The oxalic acid standard solution volume V1 consumed.
Note 2. When the content of organic carbon in the sample is high, cesium hydroxide solution II (5.10) can be used as the sample absorbing solution.
8.4 Blank test
No sample was added to the ceramic boat (6.4), and the oxalic acid standard solution volume V0 consumed was recorded according to the measurement in step 8.3.
9 Calculation and representation of results
9.1 Calculation of results
The organic carbon content OCω (in terms of carbon, mass fraction, %) in the soil is calculated according to formulas (1) and (2).
Dmwmm ×= (1)
(2)
20012) (
10 ××××
×××−=
CVV
OCω
In the formula.
M1--the mass of dry matter in the sample, g;
M--sample sample amount, g;
Dmw -- dry matter content (mass fraction) of soil samples, %;
OCω - the content of organic carbon in soil samples (in terms of carbon, mass fraction), %;
V0--titration blank consumption oxalic acid standard solution volume, ml;
V1--titration sample consumption oxalic acid standard solution volume, ml;
C - oxalic acid standard solution mass concentration, g/L;
12--the molar mass of carbon, g/mol;
200--barium hydroxide absorption liquid volume, ml;
126--molar mass of oxalic acid, g/mol;
50-- volume of barium hydroxide absorption solution used for titration, ml.
9.2 Results representation
When the measurement result is < 1.00%, it is retained to three decimal places; when the measurement result is ≥1.00%, three valid positions are reserved.
digital.
10 Precision and accuracy
10.1 Precision
Six laboratories tested the certified reference material with an organic carbon content of 0.54% and 0.51% of the actual sample.
The relative standard deviations in the experimental room were 3.8%~10.6% and 1.9%~12.6%, respectively. The relative standard deviations between laboratories were respectively
2.7%, 3.2%; the repeatability limits were 0.11% and 0.11%, respectively; the reproducibility limits were 0.11% and 0.11%, respectively.
10.2 Accuracy
Six laboratories tested the certified standard samples with an organic carbon content of 0.54%, and the relative error was
0%~3.7%; the relative error final value is 2.2%±3.6%.
11 Quality Assurance and Quality Control
11.1 Each batch of samples should be tested at least 10% of parallel samples. When the number of samples is less than 10, each batch should be made at least one.
Parallel sample determination. When the sample organic carbon content is ≤1.00%, the difference between the parallel sample determination results should be within ±0.10%;
When the sample organic carbon content is >1.00%, the relative deviation of the parallel sample determination results is ≤10.0%.
11.2 When testing each batch of samples, a certified standard sample shall be analyzed and its measured value shall be within the guaranteed value range.
12 Waste treatment
Waste liquids such as waste acid and waste alkali generated by the laboratory and solid wastes should be collected regularly and entrusted to qualified units for disposal.
13 Precautions
13.1 The absorption efficiency of carbon dioxide is greatly affected by the size and distribution of the bubbles, so it is required that the glass plate absorbs the glass plate of the bottle.
The pores are small and the quality of the glass core should be checked before use. The method is as follows. pumping at a flow rate of 0.5 L/min, bubble path
(foam height) is 50 ± 5 mm, the glass plate resistance is 4.7 ± 0.7 kPa, and the bubbles are uniform, without extra large bubbles. Magnetic stir
Stirring speed of the mixer should be appropriate to distribute the bubbles evenly in the solution.
13.2 Before the first use of the ceramic boat, it should be placed in a small beaker, and a hydrochloric acid solution (5.6) should be added to the beaker to make it dip.
Not complete, take out after a while, drain, dry at 60~70 °C for 16 h, then put the ceramic boat into the tube furnace, adjust
The furnace temperature is 900~1000 °C, and it is burned for 10 min to remove the influence of the ceramic boat material on the measurement results.
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