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HJ 873-2017Soil. Determination of water soluble fluoride and total fluoride. Ion selective electrode method (English PDF)

土壤水溶性氟化物和总氟化物的测定离子选择电极法

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Issued by

Ministry of Ecology and Environment

Level / Type

National · Mandatory

Issue date

November 28, 2017

Implementation date

January 1, 2018

Scope

HJ 873-2017 is the English-translated version of 土壤水溶性氟化物和总氟化物的测定离子选择电极法.

HJ 873-2017 — Warning. Hydrochloric acid used in the experiment has strong volatility and corrosivity, the process should be carried out in a fume hood, the operation should be as required, wear protective equipment to avoid contact with skin and clothing.

1 scope of application this standard specifies the determination of soil water-soluble fluoride and fluoride ion selective electrode method. This standard applies to soil water-soluble fluoride and total fluoride determination.

When the sample weight is 0.2 g and the sample removal amount is 20.0 ml , The detection limit of total fluoride was 63 mg/kg, the lower limit of determination was 252 mg/kg and the upper limit of determination was 1.25 × 104 mg/kg.

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Document preview — HJ 873-2017

National Standard of the People's Republic of China

ICS: 13.080
Classification: Z 18

Issued by: Ministry of Ecology and Environment

Foreword
1 Soil water-soluble fluoride and total fluoride determination Ion-selective electrode method
2 Normative references
3 Terms and definitions
4 Method principle
25 Interference and elimination
49 Analysis steps
59.3 Blank test

Foreword

In order to carry out "Environmental Protection Law of the People's Republic of China", protect the environment, protect human health, standardize the soil water-soluble fluorine Determination of total fluoride and chemical compounds, the development of this standard.

This standard specifies the soil water-soluble fluoride and fluoride total ion selective electrode method.

Appendix A of this standard is an informative annex.

This standard is released for the first time.

This standard by the Environmental Protection Department of Environmental Monitoring Division and Science and Technology Standards Division to develop.

This standard was drafted. Nanjing Environmental Monitoring Center Station.

This standard verification unit. Taizhou Environmental Monitoring Center Station, Wuxi City Environmental Monitoring Center Station, Nantong City Environmental Monitoring Heart Station, Jiangsu Province Environmental Monitoring Center, Jiangsu Provincial Institute of Geological Survey and Physical and Chemical Testing Center of Jiangsu Province.

This standard MEP approved on November 28, 2017.

This standard since January 1, 2018 come into operation.

This standard is interpreted by the MEP.

1 Soil water-soluble fluoride and total fluoride determination Ion-selective electrode method

Warning. Hydrochloric acid used in the experiment has strong volatility and corrosivity, the process should be carried out in a fume hood, the operation should be as required, wear protective equipment to avoid contact with skin and clothing.

1 scope of application this standard specifies the determination of soil water-soluble fluoride and fluoride ion selective electrode method.

This standard applies to soil water-soluble fluoride and total fluoride determination.

When the sample amount of 5.0 g, sample removal amount of 40.0 ml, the standard method for determination of water-soluble fluoride detection limit of 0.7 mg/kg, the lower limit of determination is 2.8 mg/kg and the upper limit of determination is 125 mg/kg. When the sample weight is 0.2 g and the sample removal amount is 20.0 ml , The detection limit of total fluoride was 63 mg/kg, the lower limit of determination was 252 mg/kg and the upper limit of determination was 1.25 × 104 mg/kg.

2 Normative references

This standard references the following documents or the terms of them. For undated references, the effective version applies in this standard.

HJ 613 Determination of soil dry matter and moisture Gravimetric method HJ/T 166 Soil Environmental Monitoring Technical Specifications

3 Terms and definitions

The following terms and definitions apply to this standard.

Water-soluble fluoride water soluble fluoride Under the experimental conditions specified in this standard, water was extracted from soil samples measured fluoride (fluoride).

Total fluoride

Under the experimental conditions specified in this standard, the fluorides (in terms of fluorine) of the soil samples are extracted by alkali high temperature melting.

4 Method principle

The water-soluble fluoride in the soil is extracted with water and the total fluoride is extracted with an alkali-melting method. The total ionic strength Adjusting the buffer solution, using fluoride ion selective electrode method, the fluoride ion activity in the logarithm of the electrode potential was linear.

25 Interference and elimination

Al3, Fe3, Ca2, Mg2 and other metal ions easily form a complex with fluoride ions, resulting in negative interference, the interference range the degree depends on the type of metal ions, the concentration and pH of the solution. Under the experimental conditions specified in this standard, add the total ion strong Degree adjustment buffer solution to eliminate interference.

6 Reagents and materials Unless otherwise specified, the analysis of the use of analytical standards in line with national standards of chemical reagents, experimental water resistivity >= 18 Mohm · cm (25 ° C) deionized water.

6.1 Sodium hydroxide (NaOH).

6.2 Hydrochloric acid. rho (HCl) = 1.19 g/ml.

Bromocresol purple (C21H16Br2O5S).

Trisodium citrate (C6H5Na3O7 · 2H2O).

6.5 Sodium fluoride (NaF). superior grade pure, dried at 105 °C ~ 110 °C 2 h, placed in a desiccator cooled standby.

6.6 hydrochloric acid solution. 1 1.

Measure 50 ml hydrochloric acid (6.2) and dilute to 100 ml with water.

6.7 Sodium hydroxide solution. c (NaOH) = 0.2 mol/L.

Weigh 0.80 g sodium hydroxide (6.1), dissolved in water and diluted to 100 ml.

6.8 bromocresol purple indicator. w (C21H16Br2O5S) = 0.04%.

Weigh 0.10 g bromocresol purple (6.3), dissolved in 10 ml of sodium hydroxide solution (6.7), diluted with water to 250 ml.

6.9 Total ionic strength adjustment buffer solution (TISAB). 1.0 mol/L trisodium citrate buffer solution.

Weigh 294 g of trisodium citrate (6.4) in a 1000 ml beaker, add about 900 ml of water to dissolve, use hydrochloric acid solution (6.6) Adjust pH to 6.0 ~ 7.0, diluted to 1000 ml, stored in polyethylene bottles.

6.10 Fluorine standard stock solution. rho (F -) = 500 mg/L.

Weigh 1.1050 g sodium fluoride (6.5), dissolved in water, transferred to a 1000 ml volumetric flask, the volume of water to mark, Shake, stored in polyethylene bottles, refrigerated below 4 °C, light-sealed can be stored for 6 months; or purchase a certified public standard solution.

6.11 fluorine standard solution. rho (F -) = 50.0 mg/L.

Pipette 10.00 ml fluorine standard stock solution (6.10), transferred to 100 ml volumetric flask, diluted with water to the mark, shake.

Pro use now with.

7 instruments and equipment

7.1 Ion Meter. Resolution 0.1 mV.

7.2 fluoride ion composite electrode or fluoride ion selective electrode and saturated calomel/silver - silver chloride electrode.

7.3 ultrasonic cleaner. frequency (40 kHz ~ 60 kHz), the temperature can be displayed.

37.4 muffle furnace. room temperature ~ 800 °C.

7.5 Centrifuge. maximum speed of not less than 4000 r/min, with polyethylene/polypropylene centrifuge tube.

7.6 Extraction bottle. polyethylene/polypropylene bottle, 100 ml with lid.

7.7 Beaker. Polyethylene/polypropylene, 100 ml.

7.8 Nickel crucible. 50 ml with lid.

7.9 General laboratory equipment and equipment.

8 samples

8.1 Collection and preservation Collect and store soil samples according to HJ/T 166 requirements.

8.2 Sample Preparation the soil samples were placed in a dry dish, flattened into 2 cm ~ 3 cm thick layer, first remove the plant, insects, stones and other debris, Crush clods with wooden sticks, flip several times a day and air dry naturally.

Take a well-mixed, air-dried sample by quartering and grind over a 2 mm (10 mesh) soil sieve. Take coarse grinding samples, over 0.149 mm (100 mesh) soil sieve into a sample bag or polyethylene vial.

8.3 Determination of dry matter content the dry matter content of soil samples was determined according to the relevant requirements of HJ 613.

8.4 Sample Preparation

8.4.1 Water-soluble fluoride Accurately weigh 5 g (accurate to 0.01 g) of soil sample of 0.149 mm (100 mesh) sieve in extraction flask (7.6), add 50.0 ml of water, shake with a lid, at 25 °C ± 5 °C water bath temperature ultrasonic extraction 30 min, allowed to stand a few minutes, transferred to a centrifuge tube (7.5), centrifugation 5 min ~ 10 min (speed 4 000 r/min), to be measured.

Note. The extraction process, the water bath should not be less than the level of liquid extraction, water bath temperature can be added when the ice or ice pack cooling.

8.4.2 Total fluoride Accurately weigh 0.2 g (accurate to 0.000 1 g) of a 0.149 mm (100 mesh) soil sample in a nickel crucible (7.8) plus Into 2.0 g of sodium hydroxide (6.1), capped, placed in a muffle furnace. Temperature control program. the initial temperature of 300 °C for 10 min, Heat to 560 °C ± 10 °C for 30 min. Remove after cooling, with hot water (about 80 °C ~ 90 °C) dissolved, all transferred to the burning Cup (7.7), the solution was cooled and transferred to a 100 ml colorimetric tube, slowly added 5.0 ml hydrochloric acid solution (6.6), mix, Diluted with water to the mark, shake, stand still to be measured.

8.5 blank sample preparation Without soil samples, water-soluble fluoride blank samples were prepared according to the same procedures as sample preparation (8.4.1 and 8.4.2) respectively and total fluoride blank sample.

49 Analysis steps

9.1 Calibration curve established 9.1.1 standard series preparation

9.1.1.1 Water-soluble fluoride. Pipette 0 ml, 0.10 ml, 0.20 ml, 0.40 ml, 1.00 ml, 2.00 ml, 4.00 ml, 10.00 ml Fluorine standard solution (6.11) In a 50 ml volumetric flask, add 10.0 ml total ionic strength adjustment buffer solution (6.9) Water to the mark, mix well.

9.1.1.2 Total Fluoride. Pipette 0 ml, 0.10 ml, 0.20 ml, 0.40 ml, 1.00 ml, 2.00 ml, 4.00 ml, 10.00 ml fluoride standard solution (6.11) in a beaker (7.7), followed by adding 20.0 ml total fluoride blank sample (8.5) and 1 drop ~ Two drops of bromocresol purple indicator (6.8) were added dropwise to the solution of hydrochloric acid (6.6) while shaking it until the solution changed from blue to yellow.

The solution was transferred to 50 ml volumetric flask, add 10.0 ml total ionic strength adjustment buffer solution (6.9), with water to volume Marking, mix well.

Table 1 standard series, according to the actual concentration of the sample preparation, shall not be less than 6 points.

Table 1 fluorine standard solution series

Standard point 1 2 3 4 5 6 7 8 Volume V (ml) 0 0.10 0.20 0.40 1.00 2.00 4.00 10.00 Fluorine content m (µg) 0 5.0 10.0 20.0 50.0 100.200 500 Logarithm of fluorine content lg m - 0.699 1.000 1.301 1.699 2.000 2.301 2.699

9.1.2 Calibration curve established Transfer the standard series of solutions to a beaker (7.7) in order from low to high concentrations, insert the electrodes, stir until read by the instrument the number of stable (electrode potential response fluctuations of not more than 0.2 mV/min), record the potential response. In each standard series of solutions Fluorine content of the logarithm of the abscissa, with its corresponding potential response as the ordinate, were established water-soluble fluoride and total fluoride Calibration curve.

9.2 Sample Determination

9.2.1 Water-soluble fluoride Accurate removal of the sample (8.4.1) of the supernatant 40.0 ml (according to fluoride content to reduce the amount of removal) in 50 ml volumetric flask , Add 10.0 ml total ionic strength adjustment buffer solution (6.9), the volume of water to mark, mix, press the calibration curve to build the same procedure as set forth in (9.1.2) was used to determine the potential response of the sample.

9.2.2 Total fluoride Accurate pipetting of the supernatant of the sample (8.4.2) by 20.0 ml (increase or decrease of the amount of fluoride according to fluoride content) in the beaker (7.7) , Add 1 drop to 2 drops of bromocresol purple indicator (6.8), add hydrochloric acid solution (6.6) dropwise while shaking, until the solution consists of blue-violet the color changes to yellow. Transfer the entire solution to a 50 ml volumetric flask, add 10.0 ml total ionic strength adjustment buffer (6.9) the volume of water to markings, mix, according to the calibration curve established (9.1.2) the same steps to determine the sample potential response.

59.3 Blank test

Blank samples (8.5) are to be tested according to the same procedure as for sample determination (9.2).

10 Results Calculation and Presentation

10.1 Calculation Results Fluoride content in the sample m1 (µg), calculated according to equation (1).

Where.

m1 - content of fluoride in the sample (in terms of F-), µg;

E1 - the potential response of the sample, mV;

E - Intercept of calibration curve, mV;

S - slope of the calibration curve in mV.

The sample of water-soluble fluoride or total fluoride content omega (mg/kg), according to equation (2) Calculated.

Where.

omega - content of water-soluble fluoride or total fluoride in the sample (in F-), mg/kg;

m1 - the fluoride content in the sample, µg;

m - Weigh the quality of soil samples, g;

wdm - dry matter content in soil samples,%;

V1 - total volume of soil sample extract, ml;

V2 - the volume of the supernatant taken in the sample during the measurement, ml.

10.2 results indicated Water-soluble fluoride, when the test result is less than 10.0 mg/kg, the result will be one decimal place. When the test result is greater than or equal to 10.0 mg/kg, the result retains three significant figures.

Total fluoride, the result retains the integer when the test result is less than 100 mg/kg; when the test result is greater than or equal to 100 mg/kg, the result retains three significant figures.

Vwm

dmxx

1 lg =

611 precision and accuracy 11.1 precision Six laboratories on the soil water-soluble fluoride content of 3.5 mg/kg, 7.7 mg/kg and 11.3 mg/kg of uniform reality the relative standard deviations in the laboratory were 5.6% -8.5%, 3.2% -5.7% and 3.8% -5.2% respectively. The experiment the relative standard deviations (RSDs) were 8.9%, 7.0% and 5.5% respectively. The repeatability was 0.6 mg/kg, 1.0 mg/kg and 1.4 mg/kg, respectively.

Reproducibility limits were 1.1 mg/kg, 1.8 mg/kg and 2.1 mg/kg, respectively.

Six laboratories conducted a series of tests on the uniform realities of total fluoride in soils of 527 mg/kg, 680 mg/kg and 1.14 × 104 mg/kg the relative standard deviations in the laboratory were 4.1% -6.0%, 3.7% -5.3% and 3.8% -5.3% respectively. The experiment the relative standard deviations (RSDs) were 6.8%, 5.4% and 5.8%, respectively. The repeatability limits were 74 mg/kg, 89 mg/kg and 1.49 × 103 mg/kg; reproducibility limits were 120 mg/kg, 130 mg/kg and 2.28 × 103 mg/kg, respectively.

11.2 Accuracy

11.2.1 actual sample spike test Six laboratories on the soil water-soluble fluoride content of 3.5 mg/kg, 7.7 mg/kg and 11.3 mg/kg of uniform actual sample the spiked recoveries were 76.0% ~ 110%, 73.0% ~ 110% and 74.9% ~ 109%, respectively.

The final recoveries were 91.0% ± 13.0%, 85.7% ± 12.4% and 86.3% ± 10.0%, respectively.

In six laboratories, a uniform actual sample of total fluoride in soils of 527 mg/kg, 680 mg/kg and 1.14 × 104 mg/kg the spiked recoveries were 81.5% ~ 111%, 81.4% ~ 112% and 80.3% ~ 115%, respectively.

The final recoveries were 96.3% ± 12.4%, 98.0% ± 12.0% and 97.5% ± 13.8%, respectively.

11.2.2 certified reference material test the contents of water-soluble fluoride in soil were (5.1 ± 0.6) mg/kg, (10.8 ± 1.3) mg/kg and (14.6 ± 1.5) mg/kg certified standard samples were measured, the relative error range of -3.9% ~ 7.8%, - 5.6% ~ 5.6% and -2.1% ~ 6.2% and the final relative error was 2.0% ± 8.6%, - 1.7% ± 9.4% and 0.9% ± 6.6%, respectively.

Six laboratories had total fluoride levels of (219 ± 20) mg/kg, (561 ± 43) mg/kg and (2240 ± 112) mg/kg certified standard samples, the relative error range of -4.6% -4.1%, 0.9% -3.4% and -1.8% ~ 2.1%, the final relative error were 0.1% ± 6.8%, 2.5% ± 2.2% and -0.9% ± 3.0% respectively.

Method precision and accuracy statistical results see Appendix A.

12 Quality Assurance and Quality Control

12.1 Before the sample is measured, the performance of the electrode should be verified first, and the instructions for the use of the instrument and electrode should be met.

12.2 Each batch of sample analysis should establish a calibration curve, the correlation coefficient of the calibration curve >= 0.999; when the temperature is between 20 °C ~ 25 °C, for every 10-fold change in fluoride ion concentration, the electrode potential should be -58.0 mV ± 2.0 mV.

12.3 Each series of samples or every 20 samples should be measured standard series of zero-concentration point and an intermediate concentration point, the zero-concentration point determination results 7 should be lower than the detection limit of the method, the absolute value of the relative error between the measurement result of the intermediate concentration point and its standard value should be <=10%, otherwise, Find the reason, re-establish the calibration curve.

12.4 Each batch of samples should be at least two blank test, the measurement results should be below the detection limit.

12.5 Each batch of samples should be analyzed not less than 10% of the parallel samples (samples less than 10 at least when measured in a parallel sample), flat the relative deviation of the determination result of the sample line requires <=20%.

12.6 Each batch of samples shall be analyzed not less than 10% of the spiked samples (at least one spiked sample is determined when the number of samples is less than 10) plus Standard recovery should be controlled at 70% to 120%. Or choose to synchronize with the sample certified reference material analysis, the results should be guaranteed Value range.

13 Waste treatment

The waste liquid and waste generated in the experiment should be collected in a centralized manner and be properly kept and entrusted to a qualified unit for handling.

14 Precautions

14.1 should pay attention to electrode cleaning and maintenance, in line with the electrode instructions.

14.2 The sample should be brought to room temperature before the measurement. The standard series and the sample should be tested under the same environmental conditions. The electrode measures the temperature wave Do not move more than 1 °C.

14.3 The sample should be tested when the electrode is in equilibrium (electrode potential variation <=1 mV/min).

14.4 Determination of the process should be kept the same speed of stirring; If the use of magnetic stirring equipment, should prevent the mixing time is too long lead to the sample Temperature fluctuations are too large and affect the measurement results.

14.5 When the determination of high concentrations of samples, the application of water to fully wash the electrodes to meet the electrode requirements.

Appendix A

(Informative)

The precision and accuracy of the method the precision data from the six laboratories are summarized in Table A.1.

Table A.1 method precision summary table

project

average value

(Mg/kg)

Laboratory

The relative standard deviation(%) Laboratory the relative standard deviation(%) Repeatability limit r/(mg/kg) Reproducibility limit R/(mg/kg) Soil water-soluble fluoride 3.5 5.6 ~ 8.5 8.9 0.6 1.1 7.7 3.2 ~ 5.7 7.0 1.0 1.8 11.3 3.8 ~ 5.2 5.5 1.4 2.1 Soil total fluoride 527 4.1 ~ 6.0 6.8 74 120 680 3.7 ~ 5.3 5.4 89 130 1.14 × 104 3.8 ~ 5.3 5.8 1.49 × 103 2.28 × 103 the accuracy of the spiked recoveries of the actual samples measured in the six laboratories is summarized in Table A.2.

Table A.2 Method Accuracy Summary Table (actual sample spike recovery test)

project

Background average

(Mg/kg)

Scalar

(Mg/kg)

Spike recovery range Pi /(%) Spike recovery final value 2P S+/- /(%) Soil water-soluble fluoride 3.5 5.0 76.0 ~ 110 91.0 ± 13.0 7.7 10.0 73.0 ~ 110 85.7 ± 12.4 11.3 19.9 74.9 ~ 109 86.3 ± 10.0 Soil total fluoride 527 497 81.5 ~ 111 96.3 ± 12.4 680 994 81.4 ~ 112 98.0 ± 12.0 1.14 × 104 5.00 × 103 80.3 ~ 115 97.5 ± 13.8 the accuracy of certified reference material measured by six laboratories is summarized in Table A.3.

Table A.3 method accuracy summary table (certified reference material test)

project

Determination of the average (Mg/kg) True value and uncertainty (Mg/kg) Relative error range iRE /(%) the relative error of the final value RE 2RE S+/-/(%) Soil water-soluble fluoride 5.2 5.1 ± 0.6 -3.9 ~ 7.8 2.0 ± 8.6 10.6 10.8 ± 1.3 -5.6 ~ 5.6 -1.7 ± 9.4 14.7 14.6 ± 1.5 -2.1 ~ 6.2 0.9 ± 6.6 Soil total fluoride 219 219 ± 20 -4.6 to 4.1 0.1 ± 6.8 575 561 ± 43 0.9 ~ 3.4 2.5 ± 2.2 2221 2240 ± 112 -1.8 ~ 2.1 -0.9 ± 3.0

......
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