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HJ 634-2012

Chinese Standard: 'HJ 634-2012'
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HJ 634-2012English449 Add to Cart Days<=3 Soil. Determination of ammonium, nitrite and nitrate by extraction with potassium chloride solution-spectrophotometric methods HJ 634-2012 Valid HJ 634-2012
HJ 634-2012Chinese17 Add to Cart <=1-day [PDF from Chinese Authority, or Standard Committee, or Publishing House]

   

BASIC DATA
Standard ID HJ 634-2012 (HJ634-2012)
Description (Translated English) Soil. Determination of ammonium, nitrite and nitrate by extraction with potassium chloride solution-spectrophotometric methods
Sector / Industry Environmental Protection Industry Standard
Classification of Chinese Standard Z15
Classification of International Standard 13.080
Word Count Estimation 17,167
Quoted Standard HJ 168; HJ 613; HJ/T 166; ISO/TS 14256-1
Adopted Standard ISO/TS 14256-1-2003, MOD
Drafting Organization Anshan Municipal Environmental Monitoring Center Station
Administrative Organization Ministry of Environment Protection
Regulation (derived from) Department of Environmental Protection Notice No. 16 of 2012;
Summary This standard specifies the determination of soil ammonia, nitrite nitrogen, nitrate nitrogen KCl extraction spectrophotometric method. This standard applies to soil ammonia, nitrite nitrogen, nitrate nitrogen determination. When the sample size is 40. 0g

HJ 634-2012
Soil - Determination of ammonium, nitrite and nitrate by extraction with potassium chloride solution-spectrophotometric methods
National Environmental Protection Standard of the People's Republic
Measurement of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in soil
Potassium chloride solution extraction - spectrophotometry
Soil-Determination of ammonium,nitrite and nitrate by extraction with
Potassium chloride solution -spectrophotometric methods
Published on 2012-02-29
2012-06-01 implementation
Environmental Protection Department
Content
Foreword ···· II
1 Scope ···· 1
2 Normative references ···· 1
3 Principles of the method ···· 1
4 Reagents and materials ··· 1
5 Instruments and Equipment ··· 4
6 samples ··· 5
7 Analysis steps ···· 5
8 Calculation and representation of results ···· 7
9 Precision and Accuracy ···· 8
10 Quality Assurance and Quality Control ·· 9
Appendix A (informative appendix) This standard is compared with the chapter number of ISO/T S 14256-1.2003 (E) ··· 10
Appendix B (informative) The technical differences between this standard and ISO/T S 14256-1.2003(E) and their causes ··· 12
Appendix C (Informative Appendix) Preparation of Reduction Column ·· 13
Foreword
In order to implement the Environmental Protection Law of the People's Republic of China, protect the environment, protect human health, and regulate ammonia nitrogen in the soil.
This standard is formulated for the determination of nitrite nitrogen and nitrate nitrogen.
This standard specifies the potassium chloride solution extraction-spectrophotometry for the determination of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in soil.
The technical content of this standard is to modify the use of soil quality nitrate nitrogen, nitrite nitrogen, ammonia nitrogen determination of potassium chloride
Solution Extraction Method (ISO/T S 14256-1.2003 (E)). Appendix A gives this standard and ISO/T S 14256-1.2003(E)
The chapter number comparison checklist, Appendix B gives the technical differences between this standard and ISO/T S 14256-1.2003 (E) and
the reason.
This standard is the first release.
Appendix A to Appendix C of this standard are informative annexes.
This standard was formulated by the Science and Technology Standards Department of the Ministry of Environmental Protection.
This standard is mainly drafted by. Anshan Environmental Monitoring Center Station.
This standard was approved by the Ministry of Environmental Protection on February 29, 2012.
This standard has been implemented since June 1, 2012.
This standard is explained by the Ministry of Environmental Protection.
Determination of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in soil
Potassium chloride solution extraction - spectrophotometry
1 Scope of application
This standard specifies the potassium chloride solution extraction-spectrophotometry for the determination of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in soil.
This standard applies to the determination of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in soil.
When the sample amount is 40.0 g, the detection limits of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the soil by the method are respectively
0.10 mg/kg, 0.15 mg/kg, 0.25 mg/kg, the lower limit of determination was 0.40 mg/kg, 0.60 mg/kg, and 1.00 mg/kg, respectively.
2 Normative references
The contents of this standard refer to the terms in the following documents. For undated references, the valid version applies to this
standard
HJ 168 Environmental Monitoring Analytical Methods Standard Revision Technical Guidelines
HJ 613 Soil Determination of dry matter and moisture Gravimetric method
HJ/T 166 Technical Specifications for Soil Environmental Monitoring
ISO/T S14256-1 Soil quality Determination of nitrate nitrogen, nitrite nitrogen, ammonia nitrogen Extraction of potassium chloride solution
Soil quality-Determination of nitrate, nitrite and ammonium in field-moist soils by extraction
With potassium chloride solution)
3 Principle of the method
3.1 Ammonia nitrogen
The potassium chloride solution extracts ammonia nitrogen from the soil. Under alkaline conditions, the ammonia ions in the extract are stored with hypochlorite ions.
It reacts with phenol to form a blue indophenol dye with maximum absorption at 630 nm. Ammonia in a certain concentration range
The nitrogen concentration and absorbance values ​​are in accordance with Lambert-Beer's law.
3.2 nitrite nitrogen
The nitrite nitrogen in the soil is extracted by potassium chloride solution. Under acidic conditions, the nitrite nitrogen in the extract is opposite to the sulfonamide.
A diazonium salt should be formed and coupled with N-(1-naphthyl)-ethylenediamine hydrochloride to form a red dye with a wavelength of 543 nm.
Maximum absorption. The nitrite nitrogen concentration and absorbance values ​​are in accordance with Lambert-Beer's law over a range of concentrations.
3.3 nitrate nitrogen
Nitrate nitrogen and nitrite nitrogen in soil are extracted by potassium chloride solution, and the extract is passed through a reduction column to reduce nitrate nitrogen.
For nitrite nitrogen, under acidic conditions, nitrite nitrogen reacts with sulfonamide to form diazonium salt, and then with N-(1-naphthyl) hydrochloride
- Ethylenediamine is coupled to form a red dye with maximum absorption at a wavelength of 543 nm. Determination of nitrate nitrogen and nitrite nitrogen total
the amount. The difference between the total amount of nitrate nitrogen and nitrite nitrogen and the nitrite nitrogen content is the nitrate nitrogen content.
4 reagents and materials
Analytically pure reagents that meet national standards are used for analysis, unless otherwise noted. The experimental water use conductivity is less than 0.2.
Deionized water at mS/m (measured at 25 ° C).
4.1 Ammonia nitrogen
4.1.1 Concentrated sulfuric acid. ρ(H2SO4) = 1.84 g/ml.
4.1.2 Sodium citrate dihydrate (C6H5Na3O7·2H2O).
4.1.3 Sodium hydroxide (NaOH).
4.1.4 Sodium dichloroisocyanurate (C3Cl2N3NaO3·H2O).
4.1.5 Potassium chloride (KCl). excellent grade pure.
4.1.6 Ammonium chloride (NH4Cl). excellent grade pure
Dry at 105 °C for 2 h.
4.1.7 Potassium chloride solution. c(KCl)=1 mol/L
Weigh 74.55 g of potassium chloride (4.1.5), dissolve it with an appropriate amount of water, transfer it to a 1000 ml volumetric flask, dilute to volume with water, and mix.
4.1.8 Ammonium chloride standard stock solution. ρ(NH4Cl)=200 mg/L
Weigh 0.764 g of ammonium chloride (4.1.6), dissolve it with an appropriate amount of water, add 0.30 ml of concentrated sulfuric acid (4.1.1), and after cooling,
Transfer to a 1000 ml volumetric flask, bring up to volume with water, and mix. The solution can be stored for one month at 4 ° C in the dark. Or direct purchase
Buy a commercially available certified standard solution.
4.1.9 Standard use solution of ammonium chloride. ρ(NH4Cl)=10.0 mg/L
Measure 5.0 ml of ammonium chloride standard stock solution (4.1.8) in a 100 ml volumetric flask, dilute to volume with water, and mix. Time is now
Match.
4.1.10 phenol solution
Weigh 70 g of phenol (C6H5OH) in 1000 ml of water. The solution is stored in a brown glass bottle at room temperature
It can be stored for one year.
Note. Avoid contact with skin and clothing when formulating phenol solution.
4.1.11 Dihydrate sodium nitroprusate solution
Weigh 0.8 g of sodium nitroprusside dihydrate {Na2[Fe(CN)5NO]·2H2O} dissolved in 1000 ml of water. The solution is stored in
In brown glass bottles, it can be stored for three months at room temperature.
4.1.12 buffer solution
Weigh 280 g of sodium citrate dihydrate (4.1.2) and 22.0 g of sodium hydroxide (4.1.3), dissolve in 500 ml of water, and transfer
In a 1000 ml volumetric flask, make up to volume with water and mix.
4.1.13 sodium nitroprusside-phenol developer
Measure 15 ml of sodium nitroprusside dihydrate (4.1.11) and 15 ml of phenol solution (4.1.10) and 750 ml of water, and mix.
The solution is ready for use.
4.1.14 sodium dichloroisocyanurate color developer
Weigh 5.0 g of sodium dichloroisocyanurate (4.1.4) dissolved in 1000 ml buffer solution (4.1.12) and store at 4 °C.
One month.
4.2 Nitrite nitrogen
4.2.1 Concentrated phosphoric acid. ρ(H3PO4)=1.71 g/ml.
4.2.2 Potassium chloride (KCl). excellent grade pure.
4.2.3 Sodium nitrite (NaNO2). excellent grade pure
Dry in a desiccator for 24 h.
4.2.4 Potassium chloride solution. c(KCl)=1 mol/L
Same as 4.1.7.
4.2.5 Standard stock solution of nitrite nitrogen. ρ(NO2-N)=1000 mg/L
4.926 g of sodium nitrite (4.2.3) was weighed, dissolved in an appropriate amount of water, transferred to a 1000 ml volumetric flask, and made up to volume with water.
uniform. The solution is stored in a polyethylene plastic bottle and can be stored for six months at 4 °C. Or buy a commercially available certified standard solution directly.
4.2.6 Nitrite nitrogen standard use solution I. ρ(NO2-N)=100 mg/L
Measure 10.0 ml of nitrite nitrogen standard stock solution (4.2.5) in a 100 ml volumetric flask, dilute to volume with water, and mix. use
Now available.
4.2.7 Nitrite nitrogen standard use liquid II. ρ(NO2-N)=10.0 mg/L
Measure 10.0 ml of nitrite nitrogen standard solution I (4.2.6) in a 100 ml volumetric flask, dilute to volume with water, and mix.
Available when used.
4.2.8 Sulfonamide solution (C6H8N2O2S)
Add 600 ml of water to a 1000 ml volumetric flask, then add 200 ml of concentrated phosphoric acid (4.2.1), then add 80 g of sulfonamide.
Make up to volume with water and mix. The solution can be stored for one year at 4 °C.
4.2.9 Hydrochloric acid N-(1-naphthyl)-ethylenediamine solution
Weigh 0.40 g of N-(1-naphthyl)-ethylenediamine (C12H14N2·2HCl) dissolved in 100 ml of water. Store at 4 ° C,
Stop using the solution as it darkens.
4.2.10 chromogenic agent
Separate 20 ml of sulfonamide solution (4.2.8), 20 ml of N-(1-naphthyl)-ethylenediamine hydrochloride solution (4.2.9), 20 ml
Concentrated phosphoric acid (4.2.1) was mixed in a 100 ml brown reagent bottle. Store at 4 ° C and stop using when the solution turns black.
4.3 Nitrate Nitrogen
4.3.1 Concentrated phosphoric acid. ρ(H3PO4)=1.71 g/ml.
4.3.2 Concentrated hydrochloric acid. ρ(HCl) = 1.12 g/ml.
4.3.3 Cadmium powder. Particle size 0.3 mm~0.8 mm.
4.3.4 Potassium chloride (KCl). excellent grade pure.
4.3.5 Sodium nitrate (NaNO3). excellent grade pure
Dry in a desiccator for 24 h.
4.3.6 Sodium nitrite (NaNO2). excellent grade pure
Same as 4.2.3.
4.3.7 Ammonium chloride (NH4Cl).
4.3.8 Copper sulfate (CuSO4.5H2O).
4.3.9 Ammonia water (NH4OH). excellent grade pure.
4.3.10 Potassium chloride solution. c(KCl)=1 mol/L
Same as 4.1.7.
4.3.11 Standard stock solution of nitrate nitrogen. ρ(NO3-N)=1000 mg/L
Weigh 6.068 g of sodium nitrate (4.3.5), dissolve it with a proper amount of water, transfer to a 1000 ml volumetric flask, dilute to volume with water, and mix.
The solution was stored in a polyethylene plastic bottle and stored for six months at 4 °C. Or buy a commercially available certified standard solution directly.
4.3.12 Nitrate nitrogen standard use solution I. ρ(NO3-N)=100 mg/L
Measure 10.0 ml of nitrate nitrate standard stock solution (4.3.11) in a 100 ml volumetric flask, dilute to volume with water, and mix. use
Now available.
4.3.13 Nitrate nitrogen standard use liquid II. ρ(NO3-N)=10.0 mg/L
Measure 10.0 ml of nitrate nitrogen standard solution I (4.3.12) in a 100 ml volumetric flask, dilute to volume with water, and mix.
Available when used.
4.3.14 Nitrate nitrogen standard use solution III. ρ(NO3-N)=6.0 mg/L
Measure 6.0 ml of standard use solution I (4.3.12) in a 100 ml volumetric flask, dilute to volume with water, and mix. Available when used.
4.3.15 nitrite nitrogen standard stock solution. ρ(NO2-N)=1000 mg/L
Same as 4.2.5.
4.3.16 nitrite nitrogen standard intermediate solution. ρ(NO2-N)=100 mg/L
Same as 4.2.6.
4.3.17 Nitrite nitrogen standard use solution III. ρ(NO2-N)=6.0 mg/L
Measure 6.0 ml of nitrite nitrogen standard intermediate solution (4.3.16) in a 100 ml volumetric flask, dilute to volume with water, and mix. use
Now available.
4.3.18 Ammonia solution. (1+3).
4.3.19 Ammonium chloride buffer solution stock solution. ρ(NH4Cl)=100 g/L
Dissolve 100 g of ammonium chloride (4.3.7) in a 1000 ml volumetric flask, add about 800 ml of water, and use an aqueous ammonia solution (4.3.18).
Adjust the pH value to 8.7~8.8, make up to volume with water, and mix.
4.3.20 Ammonium chloride buffer solution. ρ(NH4Cl)=10 g/L
Measure 100 ml of ammonium chloride buffer solution (4.3.19) in a 1000 ml volumetric flask, dilute to volume with water, and mix.
4.3.21 Sulfonamide solution
Same as 4.2.8.
4.3.22 Hydrochloric acid N-(1-naphthyl)-ethylenediamine solution
Same as 4.2.9.
4.3.23 chromogenic agent
Same as 4.2.10.
5 Instruments and equipment
5.1 Spectrophotometer. with a 10 mm cuvette.
5.2 pH meter. equipped with a glass electrode and a reference electrode.
5.3 Constant temperature water bath oscillator. The oscillation frequency can reach 40 times/min.
5.4 Reduction column. used to reduce nitrate nitrogen to nitrite nitrogen. See Appendix C for the preparation method.
5.5 Centrifuge. Speed ​​up to 3000 r/min with 100 ml polyethylene centrifuge tube.
5.6 Balance. Accuracy is 0.001 g.
5.7 Polyethylene bottle. 500ml with screw cap. Or other containers that neither absorb nor release the measured components into solution.
5.8 with colorimetric tube. 20 ml, 50 ml, 100 ml.
5.9 Sample sieve. 5 mm.
5.10 Common instruments and equipment used in general laboratories.
6 samples
6.1 Sample collection
Samples were collected in accordance with the relevant regulations of HJ/T 166.
6.2 Preservation of samples
Samples should be transported and stored at 4 °C after collection and analyzed within 3 days. Otherwise, it should be -20 °C (deep cold
Stored under freezing), the nitrate nitrogen and ammonia nitrogen in the sample can be stored for several weeks.
When determining the content of deep frozen nitrate nitrogen and ammonia nitrogen, the temperature and time of thawing should be controlled. Thaw at room temperature
When the sample is thawed, homogenized and extracted within 4 h, if it is thawed at 4 °C, the thawing time should not exceed 48 h.
Note 1. In order to shorten the thawing time of the sample, it should be broken into small particles before the sample is frozen.
6.3 Preparation of samples
Remove the debris from the collected soil samples, mix by hand or instrument, and pass through the sample sieve. Wear rubber when mixing by hand
Rubber gloves. After sieving, the sample is divided into two parts, one part is used to determine the dry matter content. For the determination method, see HJ 613; another part
It is used to determine the content of the component to be tested.
6.4 Preparation of samples
Weigh 40.0 g of sample (6.3), put it into a 500 ml polyethylene bottle, and add 200 ml of potassium chloride solution (4.1.7).
The shock was extracted in a constant temperature water bath shaker at 20±2 °C for 1 h. Transfer about 60 ml of the extract to a 100 ml polyethylene centrifuge tube.
Centrifuge at 3000 r/min for 10 min. Then transfer about 50 ml of the supernatant to a 100 ml colorimetric tube.
Prepare the sample and test it.
Note 2. The extract can also be prepared by standing at 4 ° C for 4 h instead of centrifugation.
6.5 Preparation of Blank Samples
Add 200 ml of potassium chloride solution to a 500 ml polyethylene bottle and prepare according to the same procedure as preparation of sample (6.4).
Blank sample.
Note 3. The sample needs to be analyzed within one day, otherwise it should be stored at 4 °C for less than one week.
7 Analysis steps
7.1 Ammonia nitrogen
7.1.1 Calibration
Measure 0, 0.10, 0.20, 0.50, 1.00, 2.00, 3.50 ml of ammonium chloride standard use solution (4.1.9) in a group
Prepare a standard series by adding water to 10.0 ml in a 100 ml plug colorimetric tube. The ammonia nitrogen content is 0, 1.0, 2.0, 5.0, respectively.
10.0, 20.0, 35.0 μg.
Add 40 ml of sodium nitroprusside-phenol developer (4.1.13) to the standard series, mix well and let stand for 15 min. Of course
After adding 1.00 ml of sodium dichloroisocyanurate coloring agent (4.1.14), mix thoroughly, at least 15 ° C ~ 35 ° C conditions
Allow to stand for 5 h. The absorbance was measured at 630 nm with water as a reference. Taking the corrected absorbance of zero concentration as a vertical sitting
The ammonia nitrogen content (μg) is plotted on the abscissa and a calibration curve is drawn.
7.1.2 Determination
Measure 10.0 ml of sample (6.4) to 100 ml with a colorimetric tube and measure according to the calibration curve (7.1.1)
The amount of absorbance.
Note 4. When the ammonia nitrogen concentration in the sample exceeds the highest point of the calibration curve, the sample is diluted with potassium chloride solution (4.1.7) and re-measured.
7.1.3 Blank test
Measure 10.0 ml blank sample (6.5) to 100 ml with a colorimetric tube and follow the calibration curve (7.1.1).
The absorbance is measured.
7.2 Nitrite nitrogen
7.2.1 Calibration
Measure the 0, 1.00, 5.00 ml nitrite nitrogen standard solution II (4.2.7) and 1.00, 3.00, 6.00 ml
Nitrite nitrogen standard use liquid I (4.2.6) in a set of 100 ml volumetric flask, dilute with water to the mark, mix, prepare the standard
The quasi-series has nitrite nitrogen contents of 0, 10.0, 50.0, 100, 300, and 600 μg, respectively.
Measure 1.00 ml of the above standard series in a set of 25ml plug colorimetric tubes, add 20 ml of water, and shake well. To each
Add 0.20 ml of color developer (4.2.10) to the colorimetric tube, mix well, let stand for 60 min to 90 min, and develop color at room temperature.
The absorbance was measured at a wavelength of 543 nm with water as a reference. To subtract the zero concentration of the corrected absorbance as the ordinate, nitrous oxide
The acid nitrogen content (μg) is plotted on the abscissa and a calibration curve is drawn.
7.2.2 Determination
Measure the absorbance according to the calibration curve (7.2.1) colorimetric tube by taking 1.00ml sample (6.4) to 25 ml colorimetric tube.
degree.
Note 5. When the nitrite nitrogen content in the sample exceeds the highest point of the calibration curve, the sample is diluted with potassium chloride solution (4.1.7), and the weight is heavy.
New measurement.
7.2.3 Blank test
Measure 1.00ml blank sample (6.5) to 25 ml colorimetric tube and measure according to calibration curve (7.2.1) colorimetric step
Absorbance.
7.3 Nitrate Nitrogen
7.3.1 Preparation of the reduction column before use
Open the piston and let the ammonium chloride buffer solution flow out of the reduction column. If necessary, wash off the salt formed on the surface with water.
Then use 20ml ammonium chloride buffer solution (4.3.20), 20ml ammonium chloride buffer solution (4.3.19) and
20 ml of ammonium chloride buffer solution was filtered through the reduction column (4.3.20) and used.
7.3.2 Calibration
Measure 0, 1.00, 5.00 ml of nitrate nitrogen standard use solution II (4.3.13) and 1.00, 3.00, 6.00 ml of nitrate
The standard of acid nitrogen is prepared by using liquid I (4.3.12) in a set of 100ml volumetric flasks, diluted with water to the mark, and mixed.
In the series, the nitrate nitrogen contents were 0, 10.0, 50.0, 100, 300, and 600 μg, respectively.
Close the piston and measure 1.00 ml of the calibration series in the reduction column. Add 10ml ammonium chloride buffer to the reduction column
Solution solution (4.3.20), then open the piston, pass the reduction column at a flow rate of 1 ml/min, and use a 50 ml plug colorimetric tube
Collect the eluent. When the liquid level reaches the top cotton, add 20ml ammonium chloride buffer solution (4.3.20), collection house.
There is effluent and remove the colorimetric tube. Finally, the reduction column was washed with 10 ml of ammonium chloride buffer solution (4.3.20).
To the above colorimetric tube, 0.20 ml of a color developing agent (4.3.23) was added, mixed well, and allowed to stand at room temperature for 60 minutes to 90 minutes.
The absorbance was measured at a wavelength of 543 nm with water as a reference. To subtract the zero concentration of the corrected absorbance as the ordinate, nitric acid
The salt nitrogen content (μg) is plotted on the abscissa and a calibration curve is drawn.
7.3.3 Determination
Measure 1.00 ml of the sample (6.4) into the reduction column and measure the absorbance according to the calibration curve (7.3.2).
Note. When the total amount of nitrate nitrogen and nitrite nitrogen in the sample exceeds the highest point of the calibration curve, dilute with potassium chloride solution (4.1.7).
Sample, re-measure.
7.3.4 Blank test
Measure 1.00 ml of the blank sample (6.5) into the reduction column and measure the absorbance according to the calibration curve (7.3.2).
8 Calculation and representation of results
8.1 Calculation of results
8.1.1 Ammonia nitrogen
The ammonia nitrogen content ω (mg/kg) in the sample was calculated according to the formula (1).
Rf
Mm ⋅⋅−= 01ω (1)
ω - the content of ammonia nitrogen in the sample, mg / kg;
1m -- the content of ammonia nitrogen in the sample obtained from the calibration curve, μg;
0m -- the content of ammonia nitrogen in the blank sample found from the calibration curve, μg;
V--the sample volume at the time of measurement, 10.0 ml;
f -- the dilution factor of the sample;
R--sample volume (including the volume of the extract and the volume of water in the soil) and the ratio of the dry soil, ml / g;
Calculate according to formula (2).
Dms
OHdmsES
Wm
dwmV
R ⋅
−⋅+= ]/)1([ 2 (2)
ESV - volume of extract, 200ml;
Sm -- the amount of sample, 40.0g;
OHd 2 - water density, 1.0 g / ml;
Dmw -- the dry matter content of the soil, %.
8.1.2 Nitrite nitrogen
The nitrite nitrogen content in the sample is ω (mg/kg), which is calculated according to formula (3).
Rf
Mm ⋅⋅−= 01ω (3)
ω - the content of nitrite nitrogen in the sample, mg / kg;
1m -- the content of nitrite nitrogen in the sample obtained from the calibration curve, μg;
0m -- the content of nitrite nitrogen in the blank sample found from the calibration curve, μg;
V--the sample volume at the time of measurement, 1.00 ml;
f -- the dilution factor of the sample;
R--sample volume (including the volume of the extract and the volume of water in the soil) and the ratio of the dry soil, ml / g;
Calculate according to formula (2).
8.1.3 Total nitrate nitrogen and nitrite nitrogen
The content of nitrate nitrogen and nitrite nitrogen in the sample is ω (mg/kg), which is calculated according to formula (4).
Rf
Mm ⋅⋅−= 01ω (4)
ω - the total amount of nitrate nitrogen and nitrite nitrogen in the sample, mg / kg;
1m -- the content of nitrate nitrogen and nitrite nitrogen in the sample obtained from the calibration curve, μg;
0m -- the content of nitrate nitrogen and nitrite nitrogen in the blank sample found from the calibration curve, μg;
V--the sample volume at the time of measurement, 1.00 ml;
f -- the dilution factor of the sample;
R--sample volume (including the volume of the extract and the volume of water in the soil) and the ratio of the dry soil, ml / g;
Calculate according to formula (2).
8.1.4 Nitrate nitrogen
Nitrate nitrogen content in the sample Nitrate nitrogen ω (mg/kg), calculated according to formula (5).
Nitrate nitrogen ω = total nitrate nitrogen and nitrite nitrogen ω - nitrate nitrogen sub-ω (5)
8.2 Results representation
When the measurement result is less than 1mg/kg, keep two decimal places; when the measurement result is greater than or equal to 1mg/kg, keep three
A valid number.
9 Precision and accuracy
9.1 Ammonia nitrogen
Soil samples with ammonia nitrogen contents of 0.73 mg/kg, 1.59 mg/kg, and 5.69 mg/kg were tested in the laboratory.
The relative standard deviations were 8.41%, 4.77%, and 4.63%, respectively.
The soil samples with ammonia nitrogen content of 1.62 mg/kg were spiked and analyzed in the laboratory. The scalar amount was 40μg.
And 100μg; the soil samples with ammonia nitrogen content of 5.76 mg/kg were spiked and analyzed, and the spiked amount was 200μg.
The recoveries of spiked samples were 80.9%~105%.
9.2 Nitrite nitrogen
In the laboratory, soil samples with nitrite nitrogen contents of 2.46 mg/kg, 4.09 mg/kg, and 8.64 mg/kg were taken.
The relative standard deviations were 5.72%, 1.66%, and 1.25%, respectively.
The actual soil samples with nitrite content of 2.46 mg/kg were spiked and analyzed in the laboratory. The scalar quantity was
400μg; the actual soil samples with nitrite nitrogen content of 4.07mg/kg were spiked and analyzed.
100μg and 360μg; the actual soil samples with nitrite nitrogen content of 9.04 mg/kg were spiked and analyzed.
The spiked amounts were 200μg and 600μg, respectively, and the actual sample spike recovery was 70.8%~91.7%.
9.3 Nitrate nitrogen
Soil samples with nitrate nitrogen content of 1.84 mg/kg, 16.2 mg/kg, and 21.9 mg/kg were used in the laboratory.
The relative standard deviations were 6.07%, 3.26%, and 4.18%, respectively.
The soil samples with nitrate nitrogen content of 1.85 mg/kg were spiked and analyzed in the laboratory. The scalar amounts were
40μg, 80μg; the soil samples with nitrate nitrogen content of 16.9mg/kg were spiked and analyzed, and the scalar amount was
300μg, 500μg, the soil samples with nitrate nitrogen content of 21.5mg/kg were spiked and analyzed.
For 400μg and 600μg, the actual sample recovery rate was 81%~114%.
10 Quality Assurance and Quality Control
10.1 At least one blank test shall be performed for each batch of samples, and the test results shall be lower than the method detection limit.
10.2 10% of parallel samples should be determined for each batch of samples. When the parallel double sample measurement result is >10.0mg/kg, the relative deviation should be
Within 10%, when the parallel double sample measurement result is ≤10.0mg/kg, the relative deviation should be within 20%.
10.3 A 10% spiked sample shall be determined for each batch of samples. Ammonia nitrogen spike recovery should be between 80% and 120%; nitrite nitrogen
The recovery rate of the spiked standard should be between 70% and 120%; the recovery rate of nitrate nitrogen should be between 80% and 120%.
10.4 The correlation coefficient of the calibration curve should be ≥0.999.
10.5 Each batch of samples should be analyzed with a standard solution of the intermediate point concentration of a calibration curve, and the measurement result and the calibration curve are concentrated.
The relative deviation of degrees should be ≤10%. Otherwise, the calibration curve needs to be redrawn.
10.6 Nitrate nitrogen reduction efficiency
Measure 1.00ml of nitrate nitrogen standard use solution III (4.3.14) and nitrite nitrogen standard use solution III (4.3.17),
Do not convert according to the procedure in 7.3.2 and measure the absorbance. The relative deviation of the measurement results should be within 5%, otherwise,
The cadmium powder in the reduction column is reprocessed.
Appendix A
(informative appendix)
This standard is compared with the chapter number of ISO/T S 14256-1.2003(E)
Schedule A.1 gives a checklist of the numbering of chapters in this standard and ISO/T S 14256-1.2003(E).
Schedule A.1 This standard is compared with the chapter number of ISO/T S 14256-1.2003(E)
This standard chapter number corresponds to the ISO/T S14256-1.2003 (E) chapter number
Related standard: HJ 633-2012    HJ 638-2012
Related PDF sample: HJ 633-2012    HJ 209-2017