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HJ 615-2011: Soil. Determination of organic carbon. Potassium dichromate oxidation spectrophotometric method
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Soil. Determination of organic carbon. Potassium dichromate oxidation spectrophotometric method
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HJ 615-2011
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Basic data | Standard ID | HJ 615-2011 (HJ615-2011) | | Description (Translated English) | Soil. Determination of organic carbon. Potassium dichromate oxidation spectrophotometric method | | Sector / Industry | Environmental Protection Industry Standard | | Classification of Chinese Standard | Z18 | | Classification of International Standard | 13.080 | | Word Count Estimation | 11,136 | | Date of Issue | 2010-04-15 | | Date of Implementation | 2011-10-01 | | Quoted Standard | HJ 613; HJ/T 166 | | Regulation (derived from) | Department of Environmental Protection Notice No. 32 of 2011 | | Issuing agency(ies) | Ministry of Ecology and Environment | | Summary | This standard specifies the determination of organic carbon in soil potassium dichromate oxidation spectrophotometry. This standard applies to dried soil organic carbon determination. This standard does not apply to chloride ion (Cl-) content greater than 2. 0 �� 104mg/kg salinization of the soil or the determination of soil salinization. | HJ 615-2011: Soil. Determination of organic carbon. Potassium dichromate oxidation spectrophotometric method
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Soil.Determination of organic carbon.Potassium dichromate oxidation spectrophotometric method
National Environmental Protection Standard of the People's Republic
Determination of soil organic carbon
Potassium dichromate oxidation-spectrophotometry
Soil-Determination of organic carbon
-Potassium dichromate oxidation spectrophotometric method
Published on.2011-04-15
2011-10-01 Implementation
Ministry of Environmental Protection released
Ministry of Environmental Protection
announcement
No. 32 of.2011
In order to implement the "Environmental Protection Law of the People's Republic of China", protect the environment, protect human health, and standardize environmental monitoring, the soil is now approved.
The three standards, such as the determination of dry matter and moisture in the soil, are national environmental protection standards and are released.
The standard name and number are as follows.
1. Determination of soil dry matter and moisture by weight method (HJ 613-2011);
2. Determination of soil tetramine by gas chromatography (HJ 614-2011);
The above standards have been implemented since October 1,.2011 and published by the China Environmental Science Press. The standard content can be found on the website of the Ministry of Environmental Protection.
Special announcement.
April 15,.2011
Content
Foreword..iv
1 Scope..1
2 Normative references..1
3 method principle..1
4 Interference and elimination.1
5 Reagents and materials.1
6 instruments and equipment.2
7 samples. 2
8 Analysis steps..2
9 Calculation and representation of results..3
10 Precision and Accuracy 3
11 Quality Assurance and Quality Control.4
12 Notes 4
Iv
Foreword
In order to implement the "Environmental Protection Law of the People's Republic of China", protect the environment, protect human health, and regulate the determination method of organic carbon in soil,
Develop this standard.
This standard specifies the potassium dichromate oxidation-spectrophotometry 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. Tianjin Environmental Monitoring Center, Liaoning Environmental Monitoring Experimental Center, Shenyang Environmental Monitoring Center Station, Anshan
Municipal Environmental Monitoring Center Station, Jinzhou Environmental Monitoring Center Station and Yingkou Environmental Monitoring Center Station.
This standard was approved by the Ministry of Environmental Protection on April 15,.2011.
This standard has been implemented since October 1,.2011.
This standard is explained by the Ministry of Environmental Protection.
Determination of soil organic carbon - Potassium dichromate oxidation - spectrophotometric method
1 Scope of application
This standard specifies the potassium dichromate oxidation-spectrophotometry for the determination of organic carbon in soil.
This standard applies to the determination of organic carbon in air-dried soil. This standard does not apply to chloride ion (Cl−) content greater than 2.0 × 104 mg/kg
Determination of salinized soil or salinized soil.
When the sample amount is 0.5 g, the detection limit of the method is 0.06% (by dry weight), and the lower limit of determination is 0.24% (by dry weight).
2 Normative references
The contents of this standard refer to the following documents or their terms. For undated references, the valid version applies to this standard.
HJ 613 Determination of dry matter and moisture in soils - Gravimetric method
HJ/T 166 Technical Specifications for Soil Environmental Monitoring
3 Principle of the method
Under heating, the organic carbon in the soil sample is oxidized by excess potassium dichromate-sulfuric acid solution, and hexavalent chromium (Cr6) in potassium dichromate
It is reduced to trivalent chromium (Cr3), which is proportional to the content of organic carbon in the sample, and the absorbance is measured at 585 nm.
The content of chrome (Cr3) is used to calculate the organic carbon content.
4 interference and elimination
4.1 The ferrous ion (Fe2) in the soil leads to a high determination of organic carbon. The soil sample can be spread into 2~ during sample preparation
A thin layer of 3 cm thick, fully exposed in air, oxidizes ferrous ions (Fe2) to ferric ions (Fe3) to eliminate interference.
4.2 Chloride ion (Cl−) in the soil results in a high determination of soil organic carbon, which is eliminated by adding an appropriate amount of mercury sulfate.
5 reagents and materials
Analytical purification reagents in accordance with national standards were used for analysis, unless otherwise stated. The experimental water is ≤0.2 mS/m at 25 °C.
Deionized water or distilled water.
5.1 Sulfuric acid. ρ(H2SO4) = 1.84 g/ml.
5.2 Mercury sulfate.
5.3 Potassium dichromate solution. c (K2Cr2O7) = 0.27 mol/L.
Weigh 80.00 g of potassium dichromate in an appropriate amount of water, dissolve it, transfer it to a 1 000 ml volumetric flask, dilute to volume with water, and shake well. Solution storage
Store in a reagent bottle at 4 °C.
5.4 Standard glucose solution. ρ(C6H12O6)=10.00 g/L.
Weigh 10.00 g of glucose in an appropriate amount of water, dissolve it, transfer it to a 1 000 ml volumetric flask, dilute to volume with water, and shake well. The solution is stored in
In the reagent bottle, the validity period is one month.
6 Instruments and equipment
6.1 Spectrophotometer. 585 nm wavelength with a 10 mm cuvette.
6.2 Balance. Accuracy is 0.1 mg.
6.3 Constant temperature heater. The temperature control accuracy is 135 °C ± 2 °C. The constant temperature heater has a heating hole, and the hole depth should be higher than that in the glass tube with a plug
The liquid level is about 10 mm, and the plug glass tube is exposed to the heating hole portion of about 150 mm.
6.4 Plug glass tube. With 100 ml mark line, the diameter is 35~45 mm.
Note. The outer wall of the glass tube with the plug must be able to adhere to the inner wall of the heating hole of the thermostat heater, otherwise the digestion is not guaranteed.
6.5 Centrifuge. 0 to 3 000 r/min with a 100 ml centrifuge tube.
6.6 Soil screen. 2 mm (10 mesh), 0.25 mm (60 mesh), stainless steel.
6.7 Common instruments and equipment used in general laboratories.
7 samples
7.1 Sample collection and preservation
The collection and storage of soil samples refer to the relevant regulations of HJ/T 166.
7.2 Preparation of samples
Place the soil sample in a clean white enamel tray and spread it into a thin layer 2 to 3 cm thick. First remove the residues such as plants, insects, stones, etc.
Crush the clods with rafts, dry naturally, and turn them several times a day when they are dry. Mix the air-dried soil thoroughly, use the quartering method, take two parts, one part
Retained, one part was passed through a 2 mm soil sieve for dry matter determination. Remove 10-20 g of the sample from the 2 mm sieve and further finely grind it.
It was placed in a brown stoppered glass via a 60 mesh (0.25 mm) soil sieve for testing.
7.3 Determination of dry matter content
Accurately weigh the appropriate amount of air-dried soil, and determine the dry matter content according to HJ 613.
8 Analysis steps
8.1 Drawing of the calibration curve
8.1.1 Separate 0.00, 0.50, 1.00, 2.00, 4.00 and 6.00 ml glucose standard solution (5.4) in 100 ml with a solution
In the glass tube, the corresponding organic carbon masses were 0.00, 2.00, 4.00, 8.00, 16.0, and 24.0 mg, respectively.
8.1.2 Add 0.1 g of mercury sulfate (5.2) and 5.00 ml of potassium dichromate solution (5.3), and shake well. Slowly add 7.5 ml of sulfuric acid (5.1),
Shake gently.
8.1.3 Turn on the thermostat heater and set the temperature to 135 °C. When the temperature rises to near 100 ° C, the above-mentioned plug-dissolved glass tube is opened.
Into the heating hole of the thermostat heater, start timing when the instrument temperature shows 135 °C, and heat for 30 min. Then turn off the thermostat heater switch,
Remove the glass tube with a plug digestion tube and cool to room temperature. Slowly add about 50 ml of water to each of the stoppered glass tubes and continue to cool to room temperature.
Make up to 100 ml of the line with water and shake it.
8.1.4 Measure the absorbance at a wavelength of 585 nm using a 10 mm cuvette with water as a reference.
8.1.5 Correct the absorbance at zero concentration to the ordinate and the corresponding organic carbon mass (mg) as the abscissa to draw a calibration curve.
8.2 Determination
Accurately weigh the appropriate amount of sample (7.2), carefully added to the 100 ml stoppered glass tube to avoid staining. Add the reagent according to 8.1.2,
Digest, cool, and make up according to 8.1.3. After the constant volume, the test solution was allowed to stand for 1 h, and about 80 ml of the supernatant was taken to the centrifuge tube at 2 000 r/min.
Centrifuge for 10 min, then stand still until clarified; or stand still in the stoppered glass tube until clarified. Finally take the supernatant according to 8.1.4
The amount of absorbance. The relationship between soil organic carbon content and sample volume is shown in Table 1.
Table 1 Relationship between soil organic carbon content and sample size
Soil organic carbon content /% 0.00 ~ 4.00 4.00 ~ 8.00 8.00 ~ 16.0
Sample sample size/g 0.400 0 ~ 0.500 0 0.200 0 ~ 0.250 0 0.100 0 ~ 0.125 0
Note 1. When the sample organic carbon content exceeds 16.0%, increase the amount of potassium dichromate solution and redraw the calibration curve.
Note 2. Under normal circumstances, it takes about 8 hours for the test solution to stand for clarification after centrifugation or to stand still for clarification for about 8 hours.
8.3 Blank test
No sample is added to the glass tube with plug digestion, and the measurement is carried out according to the procedures of 8.1.2, 8.1.3 and 8.1.4.
9 Calculation and representation of results
9.1 Calculation of results
The organic carbon content in the soil (by dry weight, mass fraction, %) is calculated according to formula (1) and formula (2).
Dm
Wm m= × (1)
Oc
( ) 100
AA aw
Bm
− −= × × × (2)
Where. - the mass of dry matter in the sample, g; 1m
M--sample sample amount, g;
Dmw -- dry matter content (mass fraction) of soil, %;
Ocω - the content of organic carbon in soil samples (by dry weight, mass fraction), %;
A--the absorbance of the sample digestion solution;
0A - the absorbance of the blank test;
A--the intercept of the calibration curve;
b--The slope of the calibration curve.
9.2 Results representation
When the measurement result is < 1.00%, it is retained to two decimal places; when the measurement result is ≥1.00%, three significant figures are retained.
10 Precision and accuracy
10.1 Precision
Six laboratories measured a uniform sample with an organic carbon content of 1.80%. the relative standard deviation in the laboratory was 0.6% to 4.0%.
The relative standard deviation between laboratories was 4.1%, the repeatability limit was 0.12%, and the reproducibility limit was 0.24%.
10.2 Accuracy
Six laboratories tested the certified standard samples with an organic carbon content of (1.80±0.16)%. the relative error was 2.2% to 8.3%.
The relative error was 5.6% ± 5.2%.
11 Quality Assurance and Quality Control
11.1 Two blank tests shall be performed for each batch of samples, and the relative deviation of the two measurements shall be ≤50%. A0 in equation (2) is two blank tests
The average of the measurements.
11.2 At least 10% of parallel samples should be measured for every 20 samples. When the number of samples is less than 10, at least one parallel should be determined for each batch of samples.
Double. When the organic carbon content of the sample is ≤1.00%, the difference between the two determination results should be within ±0.10%; when the organic carbon content of the sample
When >1.00%, the relative deviation of the two measurement results is ≤10.0%.
11.3 When testing each batch of samples, a certified reference material shall be analyzed and its measured value shall be within the guaranteed value range.
11.4 The correlation coefficient of the calibration curve should be greater than or equal to 0.999.
12 Precautions
12.1 In order to ensure the uniformity of the heating temperature of the constant temperature heater, when the sample is digested, 15 ml is placed in the heating hole without the sample.
The sulfuric acid (5.1) has a plug-dissolving glass tube to avoid the heating of the thermostat heater.
12.2 Sulfuric acid has strong chemical corrosiveness. Wear protective equipment as required to avoid contact with skin and clothing. Sample elimination
The solution should be operated in a fume hood. The waste liquid after the test should be disposed of properly.
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