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HJ 704-2014Soil quality-Determinationofavailablephosphorus. Sodium hydrogen carbonate solutionMoSbantispectrophotometric method (English PDF)

土壤有效磷的测定碳酸氢钠浸提-钼锑抗分光光度法

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Issued by

Ministry of Ecology and Environment

Level / Type

National · Mandatory

Issue date

September 15, 2014

Implementation date

December 1, 2014

Scope

HJ 704-2014 is the English-translated version of 土壤有效磷的测定碳酸氢钠浸提-钼锑抗分光光度法.

HJ 704-2014 — This standard specifies the determination of sodium bicarbonate leaching soil phosphorus - Molybdenum - Antimony Anti spectrophotometry. This standard applies to the determination of neutral and calcareous soil available phosphorus.

When the sample volume is 2.50 g, sodium bicarbonate solution using 50ml extraction, using 10 mm cuvette, the method detection limit of 0.5 mg/kg, detection limit of 2.0 mg/kg.

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Document preview — HJ 704-2014

National Standard of the People's Republic of China

Classification: Z 18

Issued by: Ministry of Ecology and Environment

Preface .ii
1. Scope .1
2 Normative references .1
3 Terms and definitions
4 Principle of the method .1
5 And eliminate interference
6 Reagents and materials
7 2 instruments and equipment
Sample 3

Foreword

To implement the "People's Republic of China Environmental Protection Law", protecting the environment, safeguarding human health, regulate soil available phosphorus Measuring method, the development of this standard.

This standard specifies the determination of sodium bicarbonate leaching soil phosphorus - Molybdenum - Antimony Anti spectrophotometry.

This standard is the first release.

Appendix A of this standard is an informative annex.

This standard is developed by the Ministry of Environmental Protection Science, Technology organization.

Drafting of this standard. Nantong Municipal Environmental Monitoring Center.

The standard verification. Jiangsu Provincial Environmental Monitoring Center, Yangzhou Municipal Environmental Monitoring Center, Zhenjiang Municipal Environmental Monitoring Center Station, Nantong City Agricultural Products Quality Testing Center, Suzhou Municipal Environmental Monitoring Center Station and Nantong, Tongzhou District Environmental Monitoring Station.

This standard MEP September 15, 2014 for approval.

This standard shall be December 1, 2014 implementation.

The standard explanation by the Ministry of Environmental Protection.

Determination of sodium bicarbonate extraction of soil phosphorus - Molybdenum - Antimony Anti spectrophotometry

1 Scope

This standard specifies the determination of sodium bicarbonate leaching soil phosphorus - Molybdenum - Antimony Anti spectrophotometry.

This standard applies to the determination of neutral and calcareous soil available phosphorus.

When the sample volume is 2.50 g, sodium bicarbonate solution using 50ml extraction, using 10 mm cuvette, the method detection limit of 0.5 mg/kg, detection limit of 2.0 mg/kg.

2 Normative references

This standard refers to the contents of the following documents or the terms. For undated references, the effective version suitable for this standard.

HJ/T 166 soil environmental monitoring technical specifications HJ 613 Determination of dry matter and soil moisture weight method NY/T 395-2012 farmland soil environmental quality monitoring technical specifications

3 Terms and Definitions

Soil phosphorus available phosphorous Abbreviated as AP, also known as available phosphorus, soil phosphorus in the plant during the growing season can be absorbed by plant roots, that is, in the present standard Under the conditions specified in the leaching out of the soil solution phosphorus, weakly adsorbed phosphorus, exchangeable phosphorus and soluble solid phosphate.

4 Principle of the method

With 0.5 mol/L sodium bicarbonate solution (pH = 8.5) leaching soil phosphorus. Extracts of phosphorus and molybdenum, antimony anti-color Agent to form phosphomolybdic blue, absorbance was measured at a wavelength of 880 nm at. Within a certain range of concentration, phosphorus content and absorbance in line with Lambert - Beer law.

5 and elimination of interference when extracts of arsenic concentrations greater than 2 mg/L interfere, it can remove sodium thiosulfate; sodium sulfide content of greater than 2 mg/L have Interference, nitrogen can be removed under acidic conditions; hexavalent chromium is greater than 50 mg/L of interference is removed with sodium sulfite; iron content to 20 mg/L, so that the results of the low 5%.

6 Reagents and materials

Unless otherwise indicated, the use of chemical analytical reagents meet the national standard analysis. Water was used to freshly prepared Ionized or distilled water.

6.1 sulfate. rho (H2SO4) = 1.84 g/ml.

Nitrate 6.2. rho (HNO3) = 1.51 g/ml.

6.3 acetic acid. rho (C2H4O2) = 1.049 g/ml.

6.4 potassium dihydrogen phosphate (KH2PO4). pure class distinctions.

Take appropriate amount of potassium dihydrogen phosphate in the weighing bottle, placed in 105 °C drying 2h, cooling in the oven and set aside.

6.5 Sodium hydroxide solution. omega (NaOH) = 10%.

Weigh 10 g of sodium hydroxide dissolved in water and diluted with water to 100 ml, stored in polyethylene bottles.

6.6 sulfuric acid solution. c (1/2 H2SO4) = 2 mol/L.

In 800 ml of water, stirring constantly slowly added 55 ml of sulfuric acid (6.1), until the solution was cooled, add water to 1000 ml, Mix well.

6.7 the nitric acid solution. 1 + 5 (V/V).

Formulated with nitric acid (6.2).

6.8 Extraction agent. c (NaHCO3) = 0.5 mol/L.

Weigh 42.0 g sodium bicarbonate dissolved in about 800 ml of water, diluted with water to about 990 ml, with sodium hydroxide solution (6.5) Adjusted to pH = 8.5 (with a pH meter), add water to 1L, temperature controlled at 25 ± 1 °C. Store in a polyethylene bottle, the solution should be used within 4h.

Note 1. The extraction agent temperature should be controlled at 25 ± 1 °C. When a specific control, preferably with a small room in a thermostatic chamber, in addition to the winter temperature to maintain 25 °C, but also Need to deionized water previously heated to 26 ~ 27 °C and then formulated.

6.9 antimony potassium tartrate solution. rho (K (SbO) C4H4O6 · 1/2H2O) = 5 g/L.

Weigh 0.5g antimony potassium tartrate was dissolved in 100 ml of water.

6.10 Molybdate solution

Measure 153ml of sulfuric acid (6.1) slowly into approximately 400 ml of water, stir well, cool. Another 10.0g paramolybdate was dissolved in 300ml of water to about 60 deg.] C, cooled. Then slowly poured sulfuric acid solution of ammonium molybdate solution, stir, then add 100 ml of tartar Antimony potassium acid solution (6.9), and finally water volume to 1L. The solution containing 10g/L ammonium molybdate and 2.75mol/L sulfuric acid. The solution it was stored in a brown bottle, stored for one year.

6.11 ascorbic acid solution. omega (C6H8O6) = 10%.

Weigh 10 g of ascorbic acid dissolved in water, was added 0.2 g EDTA disodium edetate and 8 ml of glacial acetic acid (6.3), Add water to 100ml. The solution was stored in a brown reagent bottle, it is stable at 4 °C for 3 months. Such as the color yellow, then abandoned to reconfiguration.

6.12 P standard stock solution. rho (P) = 100 mg/L.

Weigh 0.4394g potassium dihydrogen phosphate (6.4) dissolved in about 200 ml of water, add 5ml of sulfuric acid (6.1), then moved to 1000ml Volumetric flask, add water, and mix. The solution was stored in a brown reagent bottle, valid for one year. Or purchase a commercially available direct Certified reference materials.

6.13 Phosphorus standard solution. rho (P) = 5.00 mg/L.

Amount of 5.00 ml of phosphorus stock standard solution (6.12) in 100 ml volumetric flask, dilute to the mark with the extraction agent (6.8).

Pro with the existing service.

6.14 Indicator. 2,4-dinitrophenol or 2,6-dinitrophenol (C6H4N2O5), omega = 0.2%.

Weigh 0.2g 2,4- dinitrophenol or 2,6-dinitrophenol is dissolved in 100 ml of water, the solution was stored in a glass bottle.

7 Instruments and equipment

Experiment glassware must first washed with phosphate-free detergent, then nitric acid solution (6.7) soaked 24h, before re-use by Times with tap water and washed with deionized water.

7.1 Spectrophotometer. with 10mm cuvettes.

7.2 thermostat reciprocating oscillator. frequency can be controlled at 150 ~ 250r/min.

7.3 soil samples grinding equipment. shredders, agate mortar.

7.4 Analytical balance. accuracy of 0.0001g.

7.5 Soil sieve. aperture of 1mm or 20 mesh nylon screen.

7.6 stoppered conical flask. 150ml.

7.7 General Commonly used laboratory instruments and equipment.

7.8 filter. The filter paper test phosphorus.

8 Samples

8.1 Acquisition and Preservation

Press HJ/T relevant provisions of 166 soil samples were collected and stored.

8.2 Preparation of the sample

Samples were prepared in accordance with NY/T 395-2012 "soil environment quality monitoring technical specifications" for soil handling and preparation.

8.3 Determination of dry matter content

Accurately weighed amount of sample (8.2), with reference to HJ 613 Determination of dry matter content of the sample.

9 Analysis step

9.1 Preparation of the sample

Weigh 2.50g sample (8.2), in a dry 150ml stoppered Erlenmeyer flask, 50.0ml leaching agent (6.8), stopper Tight, placed on a reciprocating oscillator constant temperature at 25 ± 1 °C in the oscillation frequency of 180 ~ 200 r/min oscillations 30 ± 1min, immediately Phosphate-free filter paper (7.8) the filtrate should be analyzed on day.

Note 2. The extraction preferably has between 1 small room thermostat in winter should first open air until the temperature reaches 25 °C, and the inner temperature of the thermostat reciprocating oscillator After 25 °C, and then open the oscillator oscillates timing.

9.2 Calibration

Measure 0,1.00,2.00,3.00,4.00,5.00,6.00ml phosphorus respectively using standard solution (6.13) at 7 50ml Flask with a leaching agent (6.8) was added to 10.0ml. Add water to about 15 ~ 20ml, then add 1 drop of indicator (6.14), Was then added dropwise sulfuric acid solution (6.6) adjusted to nearly colorless solution, ascorbic acid solution was added 0.75ml (6.11), mix, 30 Seconds plus 5ml molybdate solution (6.10), water volume to 50ml, and mix. This standard series of phosphorus concentration were 0.00, 0.10,0.20,0.30,0.40,0.50,0.60mg/L.

Note 3. The above operation, there will be CO2 bubbles, should be slow shake flask, rendering the bubbles overflow bottle.

The above flask placed at room temperature for 30min (if the room temperature below 20 °C, can be placed in 25 ~ 30 °C water bath 30min).

By the following 10mm cuvette at wavelength of 880nm at room temperature higher than 20 °C ambient conditions colorimetric, deionized water as the reference points Do absorbance was measured. Reagent blank corrected absorbance as ordinate corresponding phosphorus concentration (mg/L) as the abscissa, school Standard curve.

9.3 Determination

10.0ml amount of test solution (9.1) in dry 50ml volumetric flask. Then follow the calibration (9.2) the same procedure Color development and measurement.

Note 4. The higher phosphorus content in a sample can be appropriate to reduce the volume of the sample, diluted to 10.0ml with leaching agent (6.8).

9.4 Blank test laboratory

Without the addition of soil samples, according to 9.1,9.3 same steps for color development and measurement.

10 Results Calculation and representation

10.1 Calculation Results

Available phosphorus content in soil samples omega (mg/kg), according to the equation (1) is calculated.

dmwmVb

VaAA

10 50]) [(omega (1)

Where. omega - available phosphorus content in soil samples, mg/kg;

A-- sample absorbance values;

A0-- absorbance values of the blank test;

a-- intercept of the calibration curve;

V1-- sample volume, 50ml;

50-- constant volume when the color volume, ml;

b-- slope of the calibration curve;

V2-- draw the sample volume, ml;

Amount m-- sample, 2.50g;

dmw - soil dry matter content (mass fraction),%.

10.2 The results are shown the measurement results of decimal places and consistent method detection limit up to three significant figures.

11 Precision and accuracy

11.1 Precision

6 laboratories, respectively soil available content of 4.6 mg/kg, 13.8 mg/kg, 23.3 mg/kg of unified sample the determination of the laboratory relative standard deviations were. 2.5% 4.3% 1.1% 5.2% 0.7% - 1.9%; interlaboratory the relative standard deviations were. 3.7%, 3.2%, 1.0%; repeatability limit. 0.2 mg/kg, 0.2 mg/kg, 0.2 mg/kg;

Reproducibility limit. 0.5 mg/kg, 1.2 mg/kg, 0.7 mg/kg.

11.2 Accuracy

Six laboratories on soil phosphorus content, respectively (13.8 ± 2.3) mg/kg and (23.3 ± 1.4) mg/kg of certified reference Substances were determined relative errors are. -10.0% -1.4% - -2.1% - 4.7%; final relative error values were.

(-4.8 ± 5.9)%, (- 3.7 ± 2.0)%.

12 Quality Assurance and Quality Control

The correlation coefficient of the calibration curve should be greater than 12.1 equals 0.999.

12.2 each batch of samples should be done two blank test, the test results should be below the detection limit.

12.3 parallel each batch of samples to be measured at least 10% of the two-sample, the sample is less than 10 should be measured at least a parallel twin-like.

Parallel sample measurement results allow poor should meet certain requirements (see Appendix A).

12.4 each batch of samples should be analyzed a certified reference material, the measured value should be within the guaranteed values.

12.5 each batch of samples to be done calibration curve.

13 Notes

13.1 all sampling instruments and equipment, analytical instruments and equipment should be treated no phosphorus. Glassware used in the tests Available (15) hydrochloric acid solution immersion 2h, or non-phosphorus detergent. After more than cuvette should use to dilute nitric acid or chromic acid lotion Soak a while, to remove the adsorbed molybdenum blue colored substance.

13.2 Due to leaching out of phosphorus affect baptized extract concentration, the ratio of water and soil, shaking time, temperature and the like, we have recommended Temperature Control Laboratory.

Appendix A

(Informative)

Parallel sample measured results allowable difference range Phosphorus content (mg/kg) allowed tolerance range in less than 10 mg/kg <=3mg/kg (absolute allowable difference) Greater than 10 mg/kg, equal to less than 25 mg/kg <=40% (relative allowable difference) Greater than 25 mg/kg, equal to less than 100 mg/kg <=15mg/kg (absolute allowable difference) Greater than 100 mg/kg <=25% (relative allowable difference)

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