FprEN 18259

SLOVENSKI STANDARD
oSIST prEN 18259:2025
01-december-2025
Izboljševalci tal in rastni substrati - Določanje elementov, topnih v zlatotopki
Soil improvers and growing media - Determination of aqua regia soluble elements
Bodenverbesserungsmittel und Kultursubstrate - Bestimmung von Elementen löslich in
Königswasser
Amendements du sol et supports de culture - Détermination des éléments solubles dans
l'eau régale
Ta slovenski standard je istoveten z: prEN 18259
ICS:
65.080 Gnojila Fertilizers
oSIST prEN 18259:2025 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN 18259:2025
oSIST prEN 18259:2025
DRAFT
EUROPEAN STANDARD
prEN 18259
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2025
ICS 65.080
English Version
Soil improvers and growing media - Determination of aqua
regia soluble elements
Amendements du sol et supports de culture - Bodenverbesserungsmittel und Kultursubstrate -
Détermination des éléments solubles dans l'eau régale Bestimmung von Elementen löslich in Königswasser
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 223.
If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 18259:2025 E
worldwide for CEN national Members.

oSIST prEN 18259:2025
prEN 18259:2025 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 5
5 Interferences . 5
5.1 General. 5
5.2 Spectral interferences . 6
5.3 Transport interferences . 6
5.4 Excitation interferences . 6
5.5 Chemical interferences . 6
5.6 Memory interferences . 6
6 Reagents . 6
6.1 General. 6
7 Apparatus . 7
8 Sampling . 8
9 Procedure . 8
9.1 Preparation of test and blank solution . 8
9.2 Preparation of the calibration solutions . 8
9.3 Measurement . 8
9.3.1 Instrument conditions . 8
9.3.2 Optimization of the instrument conditions . 9
9.3.3 Interferences . 9
9.3.4 Matrix effects . 9
9.3.5 Spiking . 9
10 Calculation and expression of the results . 10
11 Test report . 11
12 Validation of the method . 11
12.1 Validation in accordance with ISO 5725-2. 11
12.2 Performance characteristics. 11
Annex A (informative) Performance characteristics of the method . 12
Bibliography . 31

oSIST prEN 18259:2025
prEN 18259:2025 (E)
European foreword
This document (prEN 18259:2025) has been prepared by Technical Committee CEN/TC 223 “Soil
improvers and growing media”, the secretariat of which is held by NEN.
This document is currently submitted to the CEN Enquiry.
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
oSIST prEN 18259:2025
prEN 18259:2025 (E)
Introduction
This document is part of a modular approach and concerns the analytical measurement step. “Modular”
means that a test standard concerns a specific step in assessing a property and not the whole chain of
measurements. Inductively coupled plasma atomic emission spectrometry (ICP-AES) is nowadays widely
used and a well-established method in many laboratories.
oSIST prEN 18259:2025
prEN 18259:2025 (E)
1 Scope
This document specifies a method for the determination of elements in soil improvers or growing media
extracts using inductively coupled plasma-atomic emission spectrometry (ICP-AES).
NOTE 1 Alternatively, other suitable analytical techniques, e.g. inductively coupled plasma mass spectrometry
(ICP-MS) or atomic absorption spectrometry (AAS), are suitable for the measurement if the user proves that the
method gives the same results.
This method is applicable to aqua regia extracts prepared according to prEN 13650:2025.
NOTE 2 The method is suitable for the determination of other elements, provided the user has verified the
applicability.
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.
CEN/TS 17732:2022, Soil improvers and growing media - Terminology
EN 12579:2024, Soil improvers and growing media - Sampling
prEN 13650:2025, Soil improvers and growing media — Digestion by aqua regia for subsequent
determination of elements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in CEN/TS 17732:2022 apply.
4 Principle
The method is based on the inductively coupled plasma atomic emission spectrometry (ICP-AES)
measurement of the concentration of elements in soil improvers and growing media in aqua regia
extracts. The elements are determined after an appropriate dilution of the extract, if necessary. The
solution is dispersed by a suitable nebulizer of the ICP-AES instrument and the resulting aerosol is
transported into the plasma torch. Element specific emission spectra are produced by a radiofrequency
inductively coupled argon plasma where atoms or ions are excited at high temperature. The emission
spectra are dispersed by a spectrometer, and the intensities of the emission lines are monitored by
photosensitive devices. Multi-element determinations using sequential or simultaneous optical systems
and axial, radial or dual viewing of the plasma may be used.
5 Interferences
5.1 General
Interferences and matrix effects shall be recognized and appropriate measures to minimize them shall be
made. There are several types of interferences – see 5.2 to 5.6.
oSIST prEN 18259:2025
prEN 18259:2025 (E)
5.2 Spectral interferences
Spectral interferences are due to incomplete isolation of the radiation emitted by the analyte from other
detected radiation sources. Spectral interferences are caused by the background emission from
continuous or recombination phenomena, by stray light which causes background increase or overlap of
a spectral line from another element, or by the unresolved overlap of molecular band spectra. Background
emission and stray light can usually be compensated for by subtracting the background emission
measured adjacent to the analyte wavelength peak. To correct a sloping background shift, background
correction points on each side of the peak are used. The increase of background is more intensive with
axial-view instruments. Background correction is not required in cases of line broadening where a
background correction measurement would actually degrade the analytical result. A spectral line overlap
usually leads to the choice of an alternative line. If this is not possible, mathematical correction
procedures (e.g. inter-element correction technique or multi-component spectral fitting) can be used to
compensate for the interference. These correction procedures are usually a part of the instrument
software.
5.3 Transport interferences
Transport interferences are caused by differences in the properties between the sample solutions and
the calibration solutions (viscosity, surface tension, density, dissolved solid content, type and
concentration of acids). As a consequence, the supply of solution to the nebuliser, the efficiency of
nebulisation and the droplet size distribution of the aerosol is altered, resulting in a change of sensitivity.
Errors due to these interferences can be overcome by dilution of the solutions, by matrix matching, by
standard addition or by internal standard.
5.4 Excitation interferences
Excitation interferences are attributed to a change in the excitation conditions in the plasma, especially
by the presence of easily ionisable elements. The interference depends on the operating conditions of the
plasma (e.g. power, sample introduction, gas flowrate or observation height) and differ from element to
element. Improvement of the plasma conditions can therefore reduce excitation interferences. Other
possibilities are dilution of the solutions, matrix matching or the standard addition technique.
5.5 Chemical interferences
Chemical interferences are not significant with the ICP-AES technique, but if observed, they can be
minimized by a careful selection of operating conditions (e.g. radio frequency power, observation
position, gas flow rate and so forth).
5.6 Memory interferences
Memory interferences result when analytes in a previous sample contribute to the signals measured in a
new sample. This type of interference may be caused by sample deposits or the accumulation in pump
tubing, nebulizer, spray chamber or plasma torch. The possibility of memory interferences should be
recognized within an analytical run and suitable rinse steps and rinse times should be used.
6 Reagents
6.1 General
All reagents including water shall be of recognized analytical grade and they shall have negligible
concentration of the element to be determined if compared to the lowest concentration of that element
in the sample solution.
6.2 Nitric acid, c(HNO ) ≈ 14,3 mol/l; mass concentration ρ ≈ 1,4 g/ml
oSIST prEN 18259:2025
prEN 18259:2025 (E)
6.2.1 Diluted nitric acid solution, c(HNO ) = 5 mol/l
Add 350 ml of nitric acid (6.2) to 650 ml of water.
6.3 Hydrochloric acid, c(HCl) ≈ 12 mol/l; ρ ≈ 1,18 g/ml
6.4 Mixed acid solution, 0,8 mol/l nitric acid and 1,8 mol/l hydrochloric acid
Add 150 ml of hydrochloric acid (6.3) and 56 ml nitric acid (6.2) to 800 ml of water.
6.5 Standard stock solutions, c = 1 000 mg/l for each element
Both single-element stock solutions and multi-element stock solutions with adequate specification,
stating the acid used and the preparation technique, are commercially available. Multi-element stock
solutions are usually available at the individual mass concentration equal to 100 mg/l for each element.
These solutions are considered to be stable for more than one year, but in reference to guaranteed
stability, the recommendations of the manufacturer should be considered. Alternatively, the stock
solutions may be prepared by the dissolution of high purity metals.
6.5.1 Standard solution, c = 100 mg/l of element
Use commercially available solution of this concentration for each element or pipette, 10 ml of the
appropriate element stock solution (6.5) into a 100 ml volumetric flask. Add 10 ml of diluted nitric acid
(6.2.1), fill to the mark with water and mix well. This solution is used to prepare spiked test solutions and
calibration solutions.
6.5.2 Standard solution, c = 10 mg/l of element
Pipette 10 ml of standard solution (6.5.1) into a 100 ml volumetric flask. Add 10 ml of diluted nitric acid
(6.2.1), fill to the mark with water and mix well. This solution is used to prepare calibration solutions e.g.
for cadmium.
6.6 Argon, purity 99,995 % or better
7 Apparatus
7.1 Common laboratory glassware
7.2 Inductively coupled plasma atomic emission spectrometer
WARNING – It is essential that the manufacturer’s safety instructions are strictly observed when using
this apparatus.
The inductively coupled plasma atomic-emission spectrometer consists of a sample introduction system,
the plasma as an excitation source, an optical system, a detector and a computer with suitable software.
The sample is transported by the introduction system (rotation tube pump, nebuliser and a spray
chamber) to the plasma torch. Around the torch a water-cooled RF coil is placed. A frequency of 27 MHz
to 56 MHz with a power of 600 W to 2 000 W is usually used. The emission from the plasma can be
observed either from the side (radial) or from the torch central symmetrical axis (axial). Axial viewing
gives more signal intensity due to the increased observation path length of the normal analytical zone of
the plasma, but an increase of interference is also commonly observed. Spectral lines are measured and
registered either in a sequential or a simultaneous manner.
oSIST prEN 18259:2025
prEN 18259:2025 (E)
8 Sampling
Sampling is not part of the method specified in this document. EN 12579:2024 shall be followed dealing
with soil improvers and growing media. It is important that the laboratory receives a sample that is
representative of the product under consideration. The sample should not have been damaged or
changed during transport or storage.
9 Procedure
9.1 Preparation of test and blank solution
Aqua regia extracts are usually measured using ICP-AES directly with calibration solutions of the same
final concentration of aqua regia. The aqua regia extracts may also be used for the determination of other
elements.
A blank test is prepared for the measurement following the same procedure as for samples.
If dilution is necessary, dilute an aliquot portion of the extract in one or more steps so that the final
concentration of the element to be determined is approximately in the middle of the given calibration
range (9.2). In the final diluting step fill to the mark with the mixed acid solution (6.4) and mix well.
Prepare a diluted blank solution by pipetting a blank solution and dilute in the same way as the test
solution.
9.2 Preparation of the calibration solutions
Individual calibration series for each element or mixed series may be used. For cadmium calibration
standards, pipette volumes of 0 ml; 0,5 ml; 1 ml; 2 ml and 5 ml of the standard solution (6.5.2) into five
100 ml volumetric flasks respectively. For arsenic, copper, chromium, lead, nickel and zinc calibration
standards pipette volumes of 0 ml; 1 ml; 2 ml; 5 ml and 10 ml of the standard solution (6.5.1) into the
same five 100 ml volumetric flasks respectively.
Fill the volumetric flasks to the mark with the mixed acid solution (6.4).
The mass concentrations of cadmium in the calibration solutions are: 0 mg/l; 0,05 mg/l; 0,1 mg/l;
0,2 mg/l and 0,5 mg/l. The mass concentrations of arsenic, copper, chromium, lead, nickel and zinc in the
calibration solutions are: 0 mg/l; 1 mg/l; 2 mg/l; 5 mg/l and 10 mg/l respectively.
Individual sets of calibration solutions for each element may be used instead of the mixed calibration
solutions for all elements. If necessary, calibration solutions of higher or lower concentrations may be
prepared in the same way.
NOTE 1 Small differences in acid concentration between sample extracts and calibration solutions do not affect
the measurement.
NOTE 2 It is possible to calibrate the instrument for higher concentrations of the elements if the calibration curve
is linear.
9.3 Measurement
9.3.1 Instrument conditions
Due to differences between various kinds of instruments, no detailed instructions are given to operate
the specific instrument. The instruction provided by the manufacturer for waiting time, instrument
stability, gas flows, plasma conditions, nebuliser conditions, sample uptake rate, etc. should be followed.
The software of the instrument is used to calculate concentrations of the elements in the individual test
solutions. All test solutions, blanks and calibration solutions are measured under the same optimized
conditions using background correction and other suitable steps to eliminate or minimize interferences.
oSIST prEN 18259:2025
prEN 18259:2025 (E)
9.3.2 Optimization of the instrument conditions
The aim is to find the best sensitivity and precision and to minimize interferences for the set of lines to
be used. Emission efficiency is related, amongst other parameters, to the plasma temperature, which is a
function of RF power, argon gas flows and observation height (for radially viewed plasmas). Also, the type
of nebuliser and sample uptake rate will have an impact on the signal and the background.
9.3.3 Interferences
Background shall be measured adjacent to analyte lines on sample during analysis. The position selected
for the background intensity measurement, on one or both sides of the analytical line, will be determined
by the complexity of the spectrum adjacent to the analytical line. When working with an unknown matrix
it is necessary to check the signal of every element to be measured for possible interferences by studying
the region of the line. If spectral interferences (partial line overlap, line coincidence) occur, the
measurement shall be carried out at another wavelength. If this is not possible, correction of the
interference by mathematical correction procedures shall be carried out. High plasma power can
minimize the matrix influence.
Spectral lines which are free of interference by other elements shall be selected. As the spectral
interferences depend on the instrument resolution, they shall be identified for each type of instrument in
practical trials using mixtures of standard solutions containing the elements typically contained in
organic fertilizers and organo-mineral fertilizer samples of varying concentrations.
9.3.4 Matrix effects
The calibration blank and calibration solutions, calibration verification solution (one of the calibration
standard solutions used to check calibration of the instrument), blank test, sample solutions and quality
control solutions are measured after the stabilization of the instrument and verification of stable
conditions. Read the emission intensity of the solution at least twice and average the values. Run a
calibration blank and a calibration check solution every 20 samples or less and at the end of the
measurement.
Whenever an unknown matrix is encountered, check the following:
— matrix effects by running the spike sample;
— matrix effects by running a fivefold diluted sample;
— matrix effects by analysing at a different wavelength.
Spike recovery shall be between 90 % and 110 %. The difference between the results for the original
sample and the fivefold-diluted sample shall be less than 10 %. If the spike recovery or difference for the
diluted sample exceeds the given limit, a standard addition method shall be used.
9.3.5 Spiking
Add a known amount of a standard solution of the analyte and an equal amount of a blank solution to two
separate but equal portions of the sample solution (or its dilution). The spike shall be between 0,4 and
2 times the expected sample mass concentration. Measure both solutions as sample solutions. Determine
the ‘measured spike concentration' as the difference in mass concentration between the two spiked
sample portions.
EXAMPLE Spiking procedure: pipette 10 ml of a soil improver or growing medium extract or diluted extract
into two test tubes, add 0,1 ml of a standard solution (6.5.1) into the first test tube and 0,1 ml of blank into the
second test tube. Mix well and measure. To achieve a higher concentration of an element by spiking, stock solutions
of higher concentration may be used.
oSIST prEN 18259:2025
prEN 18259:2025 (E)
If the analytical results according to the standard addition method and the standard calibration method are equal,
the calibration curve method may be applied.
The standard addition method, spike recovery and dilution are recommended to check the efficiency of
interference reduction especially in complicated matrices and for unknown samples.
Examples of adequate wavelength are to be found in EN ISO 11885 (alternative wavelengths may be used
according to the instrument and recommendations of the producer) as well as potentially interfering
elements.
10 Calculation and expression of the results
Calculate the content of an element in the fertilizer, m , as a mass fraction in mg/kg according to
X
Formula (1).
V × XX− ××D 100
( )
dig S b
m = (1)
X
M× DM
w
...