oSIST prEN 13650:2025

SLOVENSKI STANDARD
01-december-2025
Izboljševalci tal in rastni substrati - Razklop z zlatotopko za določanje elementov
Soil improvers and growing media - Digestion by aqua regia for subsequent
determination of elements
Bodenverbesserungsmittel und Kultursubstrate - Aufschluss mit Königswasser zur
anschließenden Bestimmung der Elemente
Amendements du sol et supports de culture - Digestion à l’eau régale pour le dosage
ultérieur des éléments
Ta slovenski standard je istoveten z: prEN 13650
ICS:
65.080 Gnojila Fertilizers
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2025
ICS 65.080 Will supersede EN 13650:2001
English Version
Soil improvers and growing media - Digestion by aqua
regia for subsequent determination of elements
Amendements du sol et supports de culture - Digestion Bodenverbesserungsmittel und Kultursubstrate -
à l'eau régale pour le dosage ultérieur des éléments Aufschluss mit Königswasser zur anschließenden
Bestimmung der Elemente
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 13650:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 5
5 Reagents . 6
6 Apparatus . 6
6.1 General. 6
6.2 Method A — Thermal heating under reflux conditions . 6
6.3 Method B — Thermal heating with a heating block with containers . 6
7 Sample pre-treatment . 7
8 Sampling . 7
9 Procedure . 7
9.1 Safety . 7
9.2 Blank test . 7
9.3 Method A — Thermal heating under reflux conditions . 8
9.4 Method B — Thermal heating with a heating block with containers . 9
10 Test report . 9
11 Validation of the method . 10
11.1 Validation in accordance with ISO 5725-2. 10
11.2 Performance characteristics. 10
Annex A (informative) Adjustment to different digestion procedures and measurement
apparatuses . 11
A.1 Adjustment of the procedure to different final volumes . 11
A.2 Calculation of the sample weight . 11
A.2.1 General. 11
A.2.2 Calculation of the weight of the sample (dry matter) . 12
A.2.3 Calculation of the weight of the sample for analysis . 12
Annex B (informative) Performance characteristics of the method . 13
Bibliography . 32

European foreword
This document (prEN 13650:2025) 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 CEN Enquiry.
This document will supersede EN 13650:2001.
— the heating block procedure has been added to the reflux digestion procedure;
— the scope has been expanded including liming materials and preformed materials.
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.
Introduction
Aqua regia is applied to digest different matrices for the subsequent determination of many elements.
For example, a multi-matrix standard for aqua regia digestion of soil, treated biowaste, sludge and waste
was prepared by CEN/TC 444 “Environmental characterization of solid matrices”. CEN/TC 260
“Fertilizers and liming materials” published a standard with a similar procedure for organic and organo-
mineral fertilizers.
It is known that the digestion of soil improvers or growing media with aqua regia will not necessarily
lead to complete element recoveries and that the extract from a test sample may not reflect the total
concentrations of the target analytes. However, for most applications the result obtained based upon
digestion methods specified in this document are considered to be fit for the intended purpose.

1 Scope
This document specifies a method for the digestion of soil improvers and growing media using an aqua
regia digestion.
Materials containing more than about 28 % (m/m) organic matter will require treatment with additional
nitric acid. With high solute concentrations in extract solutions, spectral interferences and background
enhancement can be expected.
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 13039:2025, Soil improvers and growing media — Determination of organic content and ash
prEN 13040-1:2025, Soil improvers and growing media — Sample preparation — Part 1: Sample
preparation for chemical and physical tests, determination of dry matter content, moisture content and
laboratory bulk density
3 Terms and definitions
For the purposes of this document, the terms and definitions given in CEN/TS 17732:2022 and the
following apply.
3.1
aqua regia
digestion solution obtained by mixing 1 volume of nitric acid (mass fraction of 65 % to 70 %) and
3 volumes of hydrochloric acid (mass fraction of 35 % to 37 %)
3.2
digestion
mineralization of the organic matter of a sample and dissolution of its mineral part, more or less
completely, when reacting with a reagent mixture
4 Principle
A test portion is digested with aqua regia according to one of the following heating procedures:
— Method A: reflux for 120 min ± 10 min, followed by filtration/centrifugation;
— Method B: heating block at 105 °C ± 5 °C for 120 min + 10 min, followed by filtration/centrifugation.
5 Reagents
5.1 General
Use only acids and reagents of recognized analytical grade to avoid high blank values for subsequent
analytical measurements. Use a test blank solution throughout the procedure applying all steps with the
same amount of acids, but without a sample.
5.2 Water, having an electrical conductivity not higher than 0,2 mS/cm at 25 °C, free of the elements
to be determined.
5.3 Hydrochloric acid, c(HCl) = 12 mol/l; ρ ≈ 1,18 g/ml; 37 % mass/volume.
5.4 Nitric acid, c(HNO ) = 15 mol/l; ρ ≈ 1,42 g/ml; not less than 65 % mass/volume.
5.5 Nitric acid, c(HNO ) = 0,5 mol/l. Dilute 35 ml nitric acid (5.4) to 1 l with water (5.2).
5.6 Antifoaming agent, e.g. n-dodecane (C H ) or n-octanol (C H O) are suitable.
12 26 8 18
6 Apparatus
6.1 General
Usual laboratory apparatus. All glassware and plastics ware shall be adequately cleaned and stored to
avoid any contamination.
Depending upon the concentration of the element of interest, particular care should be exercised with
respect to the effective cleaning of the vessels.
6.2 Method A — Thermal heating under reflux conditions
6.2.1 Digestion vessel, temperature-resistant and capable of containing the mixture of sample and
digest solution, for example a quartz vessel. The digestion vessel shall have a volume of at least 5 times
of the volume of the aqua regia used. The inner wall of the vessel shall be inert and shall not release
substances to the digest in excess of the purity requirements of the subsequent analysis.
Silica or borosilicate glass vessels may be used instead of quartz vessels.
It may be necessary to periodically clean the digestion vessels with a suitable surfactant to remove
persistent deposits.
6.2.2 Reflux condenser, adaptable to the digestion vessel (6.2.1).
6.2.3 Absorption vessel, volatile species trap, in an open digestion system capable of trapping one or
more volatile measurement species, adaptable to the reflux condenser (6.2.2).
6.2.4 Heating device, for example a heating mantle, thermostatic controlled, or an aluminium block
thermostat.
6.3 Method B — Thermal heating with a heating block with containers
6.3.1 Digestion tube, 50 ml plastic tube, temperature-resistant and capable of containing the mixture
of sample and digest solution, with a screw cap from e.g. polypropylene.
The part of the tube not being heated and the screw cap function as a condenser but are not really a reflux
system. The material of the tube and screw cap need to be tested to be sure that release of elements of
interest does not take place. Other materials and vessels with other volumes than mentioned above are
allowed to be used if suitability has been proven.
6.3.2 Temperature controlled heating block, heating block able to heat the tube(s) to a temperature
of 105 °C ± 5 °C.
6.4 Sample containers, plastics and glass containers are both suitable.
6.5 Filter paper, usually with a pore size of 0,45 µm and resistant to the diluted aqua regia final
digestion solution.
6.6 Volumetric flasks, usually of nominal capacity of 50 ml or 100 ml.
6.7 Analytical balance, with an accuracy of 1 mg or better.
6.8 Boiling aids, anti-bumping granules or glass beads, diamet
...