ISO 20295:2018

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 2018
© ISO 2018
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Published in Switzerland
ii © ISO 2018 – All rights reserved

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
Foreword
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This document was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee SC 3,
Chemical and physical characterization.
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iv © ISO 2018 – All rights reserved

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.
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).
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.
4−
In case of agricultural soil containing phosphate fertilizer, pyrophosphate (P O ) or tripolyphosphate
2 7
5−
(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
2 © ISO 2018 – All rights reserved

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.
−
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).
4 © ISO 2018 – All rights reserved

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
...