EN ISO 23470:2011

SLOVENSKI STANDARD
01-november-2011
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Soil quality - Determination of effective cation exchange capacity (CEC) and
exchangeable cations using a hexamminecobalt trichloride solution (ISO 23470:2007)
Bodenbeschaffenheit - Bestimmung der effektiven Kationenaustauschkapazität (KAK)
und der austauschbaren Kationen mit Hexammin-cobalt-trichlorid-Lösung (ISO
23470:2007)
Qualité du sol - Détermination de la capacité d'échange cationique (CEC) effective et
des cations échangeables à l'aide d'une solution de trichlorure de cobaltihexammine
(ISO 23470:2007)
Ta slovenski standard je istoveten z: EN ISO 23470:2011
ICS:
13.080.10 .HPLMVNH]QDþLOQRVWLWDO Chemical characteristics of
soils
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 23470
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2011
ICS 13.080.20
English Version
Soil quality - Determination of effective cation exchange capacity
(CEC) and exchangeable cations using a hexamminecobalt
trichloride solution (ISO 23470:2007)
Qualité du sol - Détermination de la capacité d'échange Bodenbeschaffenheit - Bestimmung der effektiven
cationique (CEC) effective et des cations échangeables à Kationenaustauschkapazität (KAK) und der
l'aide d'une solution de trichlorure de cobaltihexammine austauschbaren Kationen mit Hexammin-cobalt-trichlorid-
(ISO 23470:2007) Lösung (ISO 23470:2007)
This European Standard was approved by CEN on 10 June 2011.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same
status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2011 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 23470:2011: E
worldwide for CEN national Members.

Contents Page
Foreword .3

Foreword
The text of ISO 23470:2007 has been prepared by Technical Committee ISO/TC 190 “Soil quality” of the
International Organization for Standardization (ISO) and has been taken over as EN ISO 23470:2011 by
Technical Committee CEN/TC 345 “Characterization of soils” the secretariat of which is held by NEN.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by December 2011, and conflicting national standards shall be withdrawn
at the latest by December 2011.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 23470:2007 has been approved by CEN as a EN ISO 23470:2011 without any modification.

INTERNATIONAL ISO
STANDARD 23470
First edition
2007-05-01
Soil quality — Determination of effective
cation exchange capacity (CEC) and
exchangeable cations using a
hexamminecobalt trichloride solution
Qualité du sol — Détermination de la capacité d'échange cationique
(CEC) effective et des cations échangeables à l'aide d'une solution de
trichlorure de cobaltihexammine

Reference number
ISO 23470:2007(E)
©
ISO 2007
ISO 23470:2007(E)
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ii © ISO 2007 – All rights reserved

ISO 23470:2007(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Principle. 1
4 Reagents. 2
5 Apparatus . 2
6 Procedure . 3
7 Test report . 8
8 Validation. 8
Annex A (informative) Comparison of different methods for the determination of effective CEC . 9
Annex B (informative) Results of the interlaboratory comparison . 14
Bibliography . 16

ISO 23470:2007(E)
Foreword
IISO (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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 23470 was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee SC 3, Chemical
methods and soil characteristics.

iv © ISO 2007 – All rights reserved

INTERNATIONAL STANDARD ISO 23470:2007(E)

Soil quality — Determination of effective cation exchange
capacity (CEC) and exchangeable cations using a
hexamminecobalt trichloride solution
1 Scope
This International Standard specifies a method for the determination of the cation exchange capacity (CEC)
3+ 2+ 2+ + 2+ 2+ +
and the content of exchangeable cations (Al , Ca , Fe , K , Mg , Mn , Na ) in soils using a
hexamminecobalt trichloride solution as extractant.
NOTE As the pH of a soil suspension in the hexamminecobalt trichloride solution is close to the pH of the suspension
in water, this method is considered to give the effective CEC, i.e. the CEC at the soil pH.
This International Standard is applicable to all types of air-dried soil samples which have been prepared in
accordance with ISO 11464.
References and results of the comparison with other methods (barium chloride, ammonium acetate) are given
in Annex A.
2 Normative references
The following referenced documents are indispensable for the application 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 11464, Soil quality — Pretreatment of samples for physico-chemical analysis
3 Principle
Cations retained by a soil sample are exchanged with the hexamminecobalt ions of an aqueous solution, with
shaking for 60 min ± 5 min at a temperature of 20 °C ± 2 °C. The CEC is obtained by difference between the
initial quantity of hexamminecobalt in solution and the quantity remaining in the extract after the exchange
reaction. The measurement of hexamminecobalt concentration in the extract can be performed by direct
spectrophotometric measurement, or by the determination of total ammonium nitrogen or total cobalt
concentrations.
The quantities of exchanged cations are determined on the same extract using spectrometric methods, such
as inductively coupled plasma atomic emission spectrometry (ICP-AES).
NOTE 1 Exchangeable acidity can also be measured in the hexamminecobalt extract.
NOTE 2 When exchangeable cations are held in micropores into which ammonium ions but not hexamminecobalt ions
can enter, the CEC and exchangeable cation values determined with this method may be smaller than those determined
by the ammonium acetate method. This has been observed in some soils containing allophane and imogolite, for example
soils developed on volcanic rocks.
ISO 23470:2007(E)
4 Reagents
Only reagents of recognized analytical quality shall be used.
4.1 Distilled or demineralized water, exempt from the elements under analysis and having a
−1
conductivity of less than 0,5 µS·cm .
−1
4.2 Hexamminecobalt trichloride [Co(NH ) Cl ], 0,016 6 mol·l solution.
3 6 3
Dissolve, to within a milligram, 4,458 g of hexamminecobalt trichloride in a volumetric flask containing 700 ml
of distilled water (4.1). Make up to volume and mix.
1)
NOTE Hexamminecobalt trichloride can be purchased from Sigma-Aldrich or Fluka.
4.3 Anti-bumping granules (e.g. pumice stone in grain form, glass beads).
−1
4.4 Boric acid (40 g·l solution).
4.5 Tashiro indicator.
Dissolve 2,0 g of methyl red and 1,0 g of methylene blue in 1 000 ml of 95° ethanol.
4.6 Phenolphthalein.
Dissolve 1 g of phenolphthalein in 1 000 ml of 95° ethanol.
4.7 Sodium hydroxide solution, 33 % (ratio of mass to volume).
−1
4.8 Sulfuric acid (H SO ), 0,025 mol·l standard volumetric solution.
2 4
4.9 Ammonium sulfate, for analysis.
3+ 2+ 2+ + 2+ 2+ + −1
4.10 Stock solutions of Al , Ca , Fe , K , Mg , Mn , Na , 1,000 g·l .
These solutions are supplied with a certified composition from a reputable source and are checked on a
regular basis.
5 Apparatus
Usual laboratory apparatus and glassware, and in particular:
5.1 Analytical balance, the weighing uncertainty range of which will not exceed ± 0,1 % of the test
portion mass.
5.2 Containers for shaking, tightly stoppered, rigid or non-rigid wall, having a volume between 75 ml and
100 ml.
5.3 50 ml distributor, set at ± 0,25 ml of the delivered volume.
5.4 End-over-end shaker, allowing the permanent suspension of the soil/extraction solution mixture,
placed in ambient air at 20 °C ± 2 °C.

1) Sigma-Aldrich and Fluka are examples of suitable products available commercially. This information is given for the
convenience of users of this International Standard and does not constitute an endorsement by ISO of this product.
2 © ISO 2007 – All rights reserved

ISO 23470:2007(E)
5.5 Slow-filtration paper filters, allowing the checking of the adsorption level of the hexamminecobalt
ions by the filter. If it cannot be neglected with respect to the measured CEC values, it should be taken into
account (see 6.3).
5.6 Centrifuge and relevant centrifuge vials, of which the centrifugation time and speed depend on the
type of centrifuge and are selected with a view to securing a clear supernatant. 4 000 r/min for 20 min are
generally sufficient, but special care shall be taken due to the high content of fixed cobaltihexammine ions on
colloidal particles.
5.7 Distillation apparatus, of which the different parts shall be assembled to ensure tightness in order to
prevent any loss of ammonia or entrainment of sodium hydroxide.
5.8 Microburette.
5.9 Spectrophotometer, allowing measurements to be performed at wavelengths of 380 nm and 475 nm,
equipped with a 10 mm path-length measuring cell.
5.10 Inductively coupled plasma atomic emission spectrometer (ICP-AES) or flame atomic
absorption spectrometer.
6 Procedure
6.1 Test portion
Pretreat soil in accordance with ISO 11464.
If Q is the number of centimoles of positive charges provided by a given volume of hexamminecobalt solution,
the centimoles of positive charges carried by the test portion shall lie between Q/10 and Q/3 inclusive, see
Table 1.
Table 1 — Test portions (in 50 ml of solution 4.2)
+ −1
Measured CEC, cmol ·kg < 2,5 2,5 to 5 5 to 10 10 to 32 32 to 64
Test portion, g 10 10 5 2,5 1,25
Weigh, to within 0,1 %, the selected mass of the test portion (see ISO 11464) and transfer it to a container for
shaking (5.2).
6.2 Exchange reaction
Add 50 ml of the hexamminecobalt trichloride solution (4.2) and shake for 60 min ± 5 min by means of the
shaker (5.4). Filter immediately through the filter (5.5) or centrifuge (5.6). Collect the clear filtrate or
supernatant. Carry out the determinations within 24 h after extraction at the latest; otherwise ascertain the
neutrality of the storage conditions.
Produce an extraction “blank” under the same conditions, but without the test portion.
6.3 Determination of CEC
6.3.1 Determination of ammonia nitrogen by distillation
6.3.1.1 Procedure
Pipette 10 ml of the extract (6.2) into the distilling apparatus flask. Make up to the volume, to about 200 ml,
with water (4.1). Add the anti-bumping granules (4.3).
ISO 23470:2007(E)
Add to the distillate recovery container 40 ml of boric acid solution (4.4) and a few drops of Tashiro indicator
(4.5). Immerse the end of the cooling apparatus to a depth of at least 1 cm in the recovery liquid. Add a few
drops of phenolphthalein (4.6) to the distilling apparatus flask.
Assemble the apparatus, taking care to ensure its tightness.
Add approximately 10 ml of the sodium hydroxide solution (4.7) and progressively heat the flask so as to distil
about 150 ml of liquid within 30 min. After this lapse of time, verify the neutrality of the distillate which flows
from the end of the cooling apparatus by means of phenolphthalein paper. If the reaction is alkaline, resume
the distillation.
Titrate the ammonia by the standard volumetric solution of sulfuric acid (4.8).
Perform a titration blank test with water using the same reagents. The poured acid volume in this case will not
exceed 0,1 ml.
Verify periodically the efficiency of the apparatus by distilling a synthetic sample containing 5 mg of nitrogen
provided in the form ammonium sulfate (4.9). The poured volume, corrected for the blank, shall be between
6,95 ml and 7,35 ml inclusive (for a theoretical value of 7,15).
Then sample 10 ml of the extraction blank and determine the ammonia in the same manner. In the absence of
absorption of the hexamminecobalt by the filter in particular, use the solution (4.2) to perform this test.
6.3.1.2 Calculation of the CEC
The cation exchange capacity, expressed in centimoles of positive charges per kilogram, is given by the
following equation:
()VV−×2×c×50×100
T= (1)
2××Vm
where
V is the volume of the sulfuric acid solution used for the blank test, in millilitres;
V is the volume of the sulfuric acid solution used for the test, in millilitres;
c is the concentration of the sulfuric acid solution, in moles per litre;
V is the distilled volume of extract and blank test, in millilitres;
m is the mass of the test portion, in grams.
Verify periodically the efficiency of the apparatus by distilling:
⎯ 10 ml of the hexamminecobalt solution (4.2);
⎯ 5 ml of this solution.
The difference between the two volumes of sulfuric acid (4.8) added in the titration step shall be between
9,7 ml and 10,3 ml inclusive (for a theoretical value of 10,0).
6.3.2 Spectrophotometric determination
6.3.2.1 Calibration and measurement
The spectrophotometric determination of the dissolved hexamminecobalt is carried out at a wavelength of
475 nm without any pretreatment of the analysed solution. The calibration function shall be linear, e
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