Soil quality -- Determination of perchlorate in soil using ion chromatography

This document specifies a method for the determination of perchlorate in soil and soil materials. Under the conditions specified in this document, a concentration as low as 0,1 mg/kg can be determined. The working range is restricted by the ion-exchange capacity of the separator column. Dilution of the water extracts to the working range can be necessary.

Qualité du sol -- Détermination du perchlorate des sols en utilisant la chromatographie ionique

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Published
Publication Date
20-Sep-2018
Current Stage
6060 - International Standard published
Start Date
10-Aug-2018
Completion Date
21-Sep-2018
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INTERNATIONAL ISO
STANDARD 20295
First edition
2018-09
Soil quality — Determination
of perchlorate in soil using ion
chromatography
Qualité du sol — Détermination du perchlorate des sols en utilisant la
chromatographie ionique
Reference number
ISO 20295:2018(E)
ISO 2018
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ISO 20295:2018(E)
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© ISO 2018

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Published in Switzerland
ii © ISO 2018 – All rights reserved
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ISO 20295:2018(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 1

5 Interferences ............................................................................................................................................................................................................ 2

6 Reagents ........................................................................................................................................................................................................................ 2

7 Apparatus ..................................................................................................................................................................................................................... 5

8 Procedure..................................................................................................................................................................................................................... 5

8.1 Pre-treatments ........................................................................................................................................................................................ 5

8.2 Extraction .................................................................................................................................................................................................... 5

8.3 Ion chromatography ........................................................................................................................................................................... 6

8.3.1 General...................................................................................................................................................................................... 6

8.3.2 Calibration ............................................................................................................................................................................. 6

8.3.3 Measurement of perchlorate ................................................................................................................................. 6

9 Quality control ........................................................................................................................................................................................................ 7

9.1 Performance of the separator column ................................................................................................................................ 7

9.2 Validity check of the calibration function ........................................................................................................................ 8

10 Calculation .................................................................................................................................................................................................................. 8

11 Expression of results ........................................................................................................................................................................................ 8

12 Test report ................................................................................................................................................................................................................... 9

Annex A (informative) Example of ion chromatography conditions and the selection of

extraction method ............................................................................................................................................................................................10

Annex B (informative) Results of interlaboratory validation study .................................................................................13

Annex C (informative) Elimination of dissolved sulfate, chloride, hydrogen carbonate,

carbonate and metals ...................................................................................................................................................................................17

Annex D (informative) Determination of perchlorate using inline matrix elimination and

applying re-injection analysis ..............................................................................................................................................................20

Annex E (informative) Determination of perchlorate using inline matrix elimination and

concentration applying two dimensional ion chromatography (2D) .........................................................23

Bibliography .............................................................................................................................................................................................................................27

© ISO 2018 – All rights reserved iii
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ISO 20295:2018(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso

.org/iso/foreword .html.

This document was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee SC 3,

Chemical and physical characterization.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2018 – All rights reserved
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ISO 20295:2018(E)
Introduction

Although perchlorate occurs naturally, it is mainly a manmade anion (ClO ). Usually, it is combined

+ + +

with NH , Na and K to form ammonium perchlorate, potassium perchlorate, and sodium perchlorate,

respectively. It was reported that more than 90 % of perchlorate is used in military activities. Due to

the excellent oxidizing capacity of perchlorate, it is added into propellant of rocket, missile, and satellite.

We can presume some routes of manmade perchlorate exposure to soil and groundwater. For example,

complete or incomplete explosion of the signal bomb (containing about 2 000 µg of perchlorate) in

target or impact area, oversupplying of perchlorate for complete combustion in firing point, grand scale

of fireworks could be the route of perchlorate exposure to soil and groundwater. In addition to these,

other route could come from waste treatment process. Because perchlorate in missile is naturally

deteriorated according to time, it should be recharged with a new one. In the past, incineration was

preferred for the treatment of deteriorated perchlorate. When the incineration process was carried out

in open space and kept as ash on site without any caution, it could be an important route of soil and

groundwater contamination. Perchlorate is very stable in water and is not adsorbed easily on soil

particle. From that view, surface water or groundwater could be contaminated more often than soil due

to surface runoff or leaching process. However, perchlorate can also contaminate soil and vegetation.

This kind of contamination could affect high level organisms in food chain. Perchlorate contamination

of drinking water and food chain potentially affect human health because it can interfere with iodide

uptake by the thyroid gland. Through this kind of interference, thyroid hormone production is

decreased and it cause hyperthyroidism. The permitted level of perchlorate concentration in drinking

water is below 15 ppb in Korea. Some states in the USA have an advisory level for perchlorate in drinking

water. It is very difficult to find a country to regulate perchlorate level in soil because it seems that

perchlorate contamination of soil is very rare in normal areas. However, perchlorate could be one of the

major contaminants at a target area or firing point in military field and it is needed to manage the

perchlorate concentration of soil to protect the vegetation, surface water, and groundwater. For this

purpose, a standard method for perchlorate analysis in soil has been developed.
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INTERNATIONAL STANDARD ISO 20295:2018(E)
Soil quality — Determination of perchlorate in soil using
ion chromatography
1 Scope

This document specifies a method for the determination of perchlorate in soil and soil materials.

Under the conditions specified in this document, a concentration as low as 0,1 mg/kg can be determined.

The working range is restricted by the ion-exchange capacity of the separator column. Dilution of the

water extracts to the working range can be necessary.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 8466-1, Water quality — Calibration and evaluation of analytical methods and estimation of

performance characteristics — Part 1: Statistical evaluation of the linear calibration function

ISO 8466-2, Water quality — Calibration and evaluation of analytical methods and estimation of

performance characteristics — Part 2: Calibration strategy for non-linear second-order calibration

functions
3 Terms and definitions
No terms and definitions are listed in this document.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at https: //www .electropedia .org/
4 Principle

A dried and sieved soil sample is used as the test portion. Perchlorate is extracted by distilled or

deionised water from the soil sample. Extraction is conducted by mechanical shaking and centrifugation.

After filtering the extract with a 0,45 µm membrane filter (e.g. cellulose acetate, hydrophilic

polypropylene or polyethersulphone filter), the filtrate is analysed by ion chromatography to determine

perchlorate.

If the adverse effects of anions, cations or organics are not negligible, appropriate pre-treatment for

the elimination of these effects should be applied. Selective removal of interfering elements using a

cartridge is one of the applicable pre-treatments.

The method requires the application of high-capacity separator columns, which allow the injection of

sample volumes up to 1 ml.

Perchlorate is separated by ion chromatography (IC). Detection is conducted by suppressed

conductivity (CD).
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ISO 20295:2018(E)

An anion-exchange resin is used as the stationary phase and an aqueous solution of salts of weak

monobasic acids and dibasic acids is used as an eluent for isocratic or gradient elution (e.g. carbonate-,

hydrogen carbonate-, hydroxide-eluent, and organic modifiers such as acetone, acetonitrile).

The concentration of perchlorate is determined after calibration of the overall procedure according to

ISO 8466-1 or ISO 8466-2.

Control experiments are necessary to check the validity of the calibration function. Replicate

determinations can be necessary. Use of a standard addition method can be required if matrix

interferences are expected.
NOTE The results of interlaboratory validation study can be found in Annex B.
5 Interferences

Any substance that has a retention time coinciding with perchlorate and producing a detector response

can interfere. Co-elution can be solved by changing columns, eluent strength (e.g. gradient elution),

modifying the eluent with organic solvents or by selective removal of the interference with sample pre-

treatment.

In the case of saline soil, a high concentration of chloride, sulfate, and carbonate in soil extracts can

cause interference with the determination of perchlorate. It was reported that an injection of 800 mg/l

of chloride, sulfate, and carbonate (about 6 mS/cm as of electrical conductivity) in perchlorate standard

solution (0,025 mg/l) resulted in 80 % of recovery for perchlorate (1). Additionally, metals like iron

or aluminium in soil extracts can have adverse effects on the performance of ion chromatograph due

to binding with the resin material of the separator or suppressor column. These interference can

be reduced by sample dilution, with the aid of special cation exchangers (e.g. Na-form, Ag-form, Ba-

form, H-form) or resolved by the application of advanced inline cutting or re-injection techniques (see

Annexes C, D and E).

Users of this document’s method should check their system individually for the significant interfering

concentration of anions and cations.

In case of agricultural soil containing phosphate fertilizer, pyrophosphate (P O ) or tripolyphosphate

2 7

(P O ) could be coeluted with perchlorate depending on the conditions of ion chromatography (2).

3 10
This kind of interference could be avoided by using an optimized eluent.

Clay particles (e.g. aluminosilicates) or organic compounds (e.g. humic acids) can plug the column even

though the centrifugation and filtering processes are applied. It is recommended to use a pre-column to

protect the analytical separator column.
6 Reagents

Use only reagents of pro-analysis grade free of compounds containing perchlorate. Weigh the

reagents with an accuracy of ±1 % of the nominal mass, unless stated otherwise. Prepare alternative

concentrations or volumes of solutions as described in 6.2 to 6.9, if necessary. Alternatively, use

commercially available solutions of the required concentration.
6.1 Water, with a resistivity of ≥18,2 MΩ cm (25 °C).
6.2 Potassium perchlorate, KClO .
6.3 Sodium hydrogen carbonate, NaHCO .
6.4 Sodium chloride, NaCl.
6.5 Sodium sulfate, Na SO .
2 4
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ISO 20295:2018(E)
6.6 Sodium nitrate, NaNO .
6.7 Eluents.
6.7.1 General

Degas all eluents used. Take steps to avoid any renewed air pick-up during operation (e.g. by helium

sparging and inline degassing).

The choice of eluent (e.g. potassium hydroxide, sodium hydrogen carbonate, sodium carbonate,

sodium hydroxide solutions; mixed with organic modifiers if needed) depends on the choice of column

and detector. Seek advice from the column supplier. Apply eluents that were prepared manually,

automatically or in situ electrochemically prepared. The chosen combination of separator column and

eluent should conform to the resolution requirements stated in Clause 9. Use eluents as long as the

requirements in 8.3.3 and in Clause 9 are met.

One example for an appropriate manually prepared eluent is given in 6.7.2. Additionally, another

example for an appropriate eluent prepared using a generating device is given in 6.7.3.

6.7.2 Sodium hydroxide, ρ(NaOH) = 65 mmol/l.

Prepare 65 mmol/l of NaOH by putting 5,2 g of 50 % (mass fraction) aqueous NaOH from the middle

portion of the reagent bottle into a 1 000 mL volumetric flask containing about 500 ml of degassed

water. Fill it up to the mark with degassed water. Mix this solution gently and degas by sparging with

argon or helium or sonicating under a vacuum for 10 min. For the preparation of 50 % (mass fraction)

aqueous NaOH, weigh 50 g of sodium hydroxide and transfer into a 100 ml volumetric flask. Dissolve

by adding water (6.1) and fill to the mark with water (6.1). Do not shake the 50 % (mass fraction) NaOH

bottle to avoid forming carbonate.

NOTE Solutions of sodium hydroxide can be susceptible to carbonate contamination resulting from the

adsorption of carbon dioxide from the atmosphere. This contamination can lead to irreproducible perchlorate

retention times, elevated instrument background conductivity and increased baseline noise/drift.

6.7.3 Potassium hydroxide, ρ(KOH) = 65 mmol/l.

If the ion chromatographic system has a generating device for KOH eluent, generate 65 mmol/l of KOH

eluent according to the manufacturer’s recommendations.

Depending on the column's properties the eluent composition can be different. According to the

manufacturer’s instructions, check which kind of eluent is appropriate for analysing perchlorate.

6.8 Standard solutions.
6.8.1 Perchlorate stock standard solution, ρ(ClO ) = 1 000 mg/l.

Dry potassium perchlorate in the oven at 100 °C for 2 h. Weigh (1,393 ± 0,001) g and transfer

quantitatively into a 1 000 ml volumetric flask. Dissolve by adding water (6.1) and fill to the mark with

water (6.1). Store this stock standard solution in the refrigerator at 2 °C to 8 °C using polyethylene or

glass bottles. This stock standard solution is stable for 12 months.

The use of commercially available certified stock standard solution is also possible.

Other alternative perchlorate compounds (e.g. sodium perchlorate, ammonium perchlorate) may also

be used in the preparation of (stock) standard solution.
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ISO 20295:2018(E)
6.8.2 Perchlorate standard solution I, ρ(ClO ) = 100 mg/l.

Add 10 ml of stock standard solution (6.8.1) into a 100 ml volumetric flask and fill it up to the mark with

water (6.1). Store this working standard solution in the refrigerator at 2 °C to 8 °C using polyethylene or

glass bottles. This standard solution would be stable for 6 months.

In addition, a working standard solution can be made through the dilution of commercially available

certified stock standard solution with water (6.1).
6.8.3 Perchlorate standard solution II, ρ(ClO ) = 1 mg/l.

Add 1,0 ml of perchlorate standard solution I (6.8.2) into a 100 ml volumetric flask and fill it up to the

mark with water (6.1). Store this working standard solution in the refrigerator at 2 °C to 8 °C using

polyethylene or glass bottles. This standard solution is stable for 3 months.
6.8.4 Perchlorate calibration standard solution.

Prepare the calibration standard solutions through the dilution of perchlorate standard solution I

(6.8.2) or perchlorate standard solution II (6.8.3). At least, five levels of concentration should be

prepared over the expected working ranges as evenly as possible (e.g. 0,05, 0,1, 0,2, 0,4, 0,8 and 1 mg/l).

6.8.5 Perchlorate system check solution, ρ(ClO ) = 0,5 mg/l.

Add 0,5 ml of perchlorate standard solution I (6.8.2) into a 100 ml volumetric flask and fill it up to the

mark with water (6.1). Prepare the solution on the day of use.
− −
− 2−
6.8.6 Matrix check stock solution, ρ(HCO , Cl , SO , NO ) each of 1 g/l.
3 3

Place 3,44 g of sodium hydrogen carbonate (6.3), 4,13 g of sodium chloride (6.4), 3,72 g of sodium

sulfate (6.5) and 3,42 g of sodium nitrate (6.6) in a 100 ml volumetric flask. Dissolve these compounds

in approximately 80 ml of water (6.1) and fill the flask up to the mark with water (6.1). This solution is

stable for 1 year.

Dilute 4 ml of this solution in 100 ml of water (6.1) to obtain the 1 g/l-stock solution. This solution

would be stable for 6 months.
6.8.7 Perchlorate matrix check stock solutions, ρ(ClO ), 2 mg/l.

Depending on the laboratory internal conditions chosen (e.g. separation characteristics), prepare a

check solution spiked with an appropriate perchlorate concentration. The composition of this check

solution should cover the actual conditions of samples as closely as possible. For example, to make

samples with chloride and sulfate concentrations of up to 50 mg/l each and a presumed perchlorate

concentration of 2 mg/l, follow the process described below:

Pipette 5 ml of the matrix check stock solution (6.8.6) and 2 ml of the perchlorate standard solution I

(6.8.2) into a 100 ml volumetric flask and fill it up to the mark with water (6.1).

The concentrations in this solution are: 50 mg/l of carbonate, chloride, sulfate, and nitrate, respectively,

and 2 mg/l of perchlorate. Prepare the solution on the day of use.
6.9 Blank solution.
Fill a volumetric flask (e.g. 100 ml) with water (6.1).
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ISO 20295:2018(E)
7 Apparatus

7.1 Horizontal mechanical shaker, maintaining a frequency of 100 cycles/min and offering a shaking

width of about 10 cm.
7.2 Centrifuge, should be used at a speed setting of 3 000 rpm.

7.3 Membrane filters, with 0,45 µm pore size or smaller (e.g. hydrophilic polypropylene or

polyethersulphone filter).

7.4 Cartridges, Ag-form, Ba-form, H-form and Na-form for the selective removal of chloride, sulfate,

carbonate and cations (e.g. iron, aluminium), respectively.
7.5 Analytical balance, being capable of making precise measurements of ±0,1 mg.
7.6 Ion chromatographic system.
7.6.1 Eluent reservoir, equipped with a degassing unit.

7.6.2 Pumping system, having an accurate flow rate and pulse-free flow and suitable for the isocratic

or gradient technique.

7.6.3 Injection valve, appropriate for reproducible injections into the high-pressure flow path,

equipped with sample loop which allow the injection of sample volumes up to 1 ml.

7.6.4 Separator column, with the specified separating performance (9.1).

7.6.5 Pre-column, having the capability to protect the analytical separator column.

NOTE In general, pre-columns contain the same as or similar resin materials to the analytical separator

column or non-functionalised resin.

7.6.6 Conductivity detector, thermally controlled and sensitive with a suppressor device.

7.6.7 Recording device.
8 Procedure
8.1 Pre-treatments

General pre-treatments include drying and sieving. The field moist sample is dried in the air or oven.

In the case of air drying, spread the soil sample no thicker than 5 cm on the tray. The tray should not

absorb any moisture from the soil. Additionally, direct sunlight should be avoided. For oven drying, the

temperature in the oven should not exceed 40 °C and a ventilation device should be equipped.

The dried sample is passed through a 2 mm sieve and then it is used as a test portion.

For other details of pre-treatments, refer to ISO 11464.
8.2 Extraction

Weigh (10 ± 0,1) g of dried and sieved soil sample into a 50 ml centrifuge tube. Add 30 ml of deionized

water. Shake it using a mechanical shaker (7.1) for 1 h at 100 cycles/min. After the shaking process,

centrifuge the mixture at 3 000 rpm for 1 h (Annex A). Filter the supernatant through a 25 mm

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ISO 20295:2018(E)

diameter and 0,45 µm pore size membrane filter with a syringe (e.g. hydrophilic polypropylene or a

polyethersulphone filter). In this step, discard the first portion (e.g. about 0,3 ml) of filtrate and filter the

remainder directly into a clean plastic vial. The filtrate is used for ion chromatographic determination.

If necessary, cartridges (7.4) are applicable for the removal of anionic and cationic interference in the

filtrate according to the manufacturer’s instructions.

For the verification of the filtering step, analyse 30 ml of 0,01 mg/l of perchlorate standard solution that

has passed through the filter in the same way as that described in 8.2. The recovery of the 0,01 mg/l of

perchlorate standard should fall between 80 % and 120 %.
8.3 Ion chromatography
8.3.1 General

Set up the ion chromatographic system (7.6) according to the manufacturer’s instructions. Run the

eluent, and confirm the baseline stability.

Perform the calibration as described in 8.3.2. Measure the samples and blank solution (6.9) according

to 8.3.3. An example of ion chromatography conditions can be found in Annex A.
8.3.2 Calibration

Inject the calibration standard solutions (6.8.4). The measured signal (peak area or peak height) is

proportional to the concentration of the perchlorate ion.

When the analytical system is first started up and at intervals afterwards, establish a calibration

function (see ISO 8466-1 or ISO 8466-2) for the measurement as follows. This is usually done by a

software of the instrument.

Use the data obtained (peak area or peak height) to calculate the regression line as specified in

ISO 8466-1 or ISO 8466-2.

Subsequently, verify the continuing validity of the established calibration function (9.2).

NOTE Generally, the calibration method is not restricted to a calibration strategy covering a single

concentration decade as specified in ISO 8466-1 or ISO 8466-2 only. When calibrating over a larger range than

one concentration decade, a loss of accuracy, compared to that specified in ISO 8466-1 or ISO 8466-2, can occur.

8.3.3 Measurement of perchlorate

Identify the peak of the perchlorate by comparing the retention time with that of the calibration

standard solution. Deviation of the retention time should not exceed 10 % within a batch. The use of a

pre-column is recommended to protect the analytical separator column.

If the concentration of perchlorate in the sample exceeds the calibration range, dilute the sample and

reanalyse it.

In case the concentration of perchlorate in the sample is outside of the calibration range, if necessary,

establish a new calibration function for a lower working range.

If matrix interferences influencing the retention time of perchlorate, are expected, check the system

suitability using standard addition method to confirm the results (verify the peaks by comparing the

retention time of the spiked sample with that of the original sample).

Peak resolution R between the anion of interest and its nearest peak should be checked according to

Clause 9.
Measure the blank solution (6.9) in the same way.
6 © ISO 2018 – All rights reserved
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