oSIST prEN 17778:2026
(Main)Organic and organo-mineral fertilizers - Determination of chromium(VI) content
- Abstract
This document specifies a method for the determination of hexavalent chromium (chromium(VI)) in organic and organo-mineral fertilizers.
The method specified is suitable to quantify the chromium(VI) content in organic and organo-mineral fertilizers down to 2 mg/kg dry matter.
The results obtained from this method are strictly dependent on the extraction conditions. Results obtained by using other extraction procedures (extraction solution, pH of the extraction solution, extraction time, extraction temperature, etc.) are not comparable with the results produced by the procedure described in this document.
This document is applicable to fertilizing products blends where a blend is a mix of at least two of the following components: fertilizers, liming materials, soil improvers, growing media, inhibitors, plant biostimulants and where organic matter is present in at least one of the products in the blend. In case a fertilizing product blend is composed only of inorganic products, the European Standard for inorganic fertilizers or liming materials applies. Variations in analytical methods for fertilizing product blends can lead to differing results as some components or matrix interactions can affect the outcome. Validation procedures have shown that developed standard methods are robust and reliable across diverse product compositions, but possible interferences and unexpected results when analysing fertilizing product blends are possible.
- Status
- Not Published
- Public Enquiry End Date
- 01-Apr-2026
- Technical Committee
- KAT - Soil quality
- Current Stage
- 4020 - Public enquire (PE) (Adopted Project)
- Start Date
- 11-Feb-2026
- Due Date
- 01-Jul-2026
- Completion Date
- 29-Apr-2026
oSIST prEN 17778:2026 is CEN's draft European Standard for determining chromium(VI) in organic and organo-mineral fertilizers. It specifies a laboratory method based on phosphate-buffer extraction and ion chromatography with UV/VIS detection, for manufacturers, test laboratories, quality teams and conformity-checking users working with EU fertilising products. The method also applies to fertilizing product blends when organic matter is present in at least one component.
What does oSIST prEN 17778:2026 specify?
oSIST prEN 17778:2026 specifies a procedure for measuring hexavalent chromium, written as chromium(VI) or Cr(VI), in organic and organo-mineral fertilizers and in certain fertilizing product blends. The document is organized into scope, references, terms, principle, reagents, apparatus, procedure, calculation, precision and test reporting, followed by informative annexes.
The scope also makes the method's working conditions clear in practice: the result depends on the extraction conditions, so results from other extraction solutions, pH values, times or temperatures are not comparable. That matters if a laboratory wants results that can be defended against the procedure in this standard.
| Annex | What it covers |
|---|---|
| Annex A | Results of the inter-laboratory study and statistical precision data |
| Annex B | Example chromatographic conditions for the direct detection method |
| Annex C | Example chromatographic conditions for the method with post-column reaction |
| Annex ZA | Relationship with Regulation (EU) 2019/1009 and the corresponding essential requirements |
What are the key requirements of oSIST prEN 17778:2026?
oSIST prEN 17778:2026 requires a controlled extraction, a validated chromatographic measurement, recovery checking and reporting on a dry-matter basis. In practice, the standard is as much about keeping the chemistry and the timing consistent as it is about reading the instrument signal.
- Clause 4, Principle - oSIST prEN 17778:2026 gives two compliance routes: test total chromium so long as the result is below the chromium(VI) limit, or test chromium(VI) directly. This matters because a total chromium result can be used as a practical screening tool, while direct chromium(VI) measurement is the specific route covered here.
- Clause 4 and 7.2 - The method extracts chromium(VI) with phosphate buffer at pH 7,0 to pH 8,0, then analyses the filtered extract by ion-exchange chromatography with UV-VIS detection. For the reader, this means the extraction chemistry is not optional - it is the core of the measurement.
- 7.2.1 and 7.2.2 - Solid samples and liquid samples use different sample masses and extraction times, and the extract must be filtered and checked for pH before instrumental analysis. The extract should be measured as soon as possible and no later than 60 min after extraction, which matters because chromium(VI) can be reduced after preparation.
- 7.2.1 and 7.2.2 - Oxygen is displaced with oxygen-free argon or nitrogen, and magnesium chloride solution may be added when significant chromium(III) is expected. In practice, this is a stability safeguard for samples that may reduce chromium(VI) during handling.
- 7.3 and Annex B or Annex C - The standard allows either direct detection at 372 nm or post-column reaction with 1,5-diphenylcarbazide at 540 nm. This gives laboratories a choice based on available equipment, but they still need to verify the chosen setup with the recovery check.
- 7.4 - Calibration uses external standards prepared from the chromium(VI) standard solution, with at least five levels in the stated range. For users, this means the lab must build a calibration curve that covers the expected sample concentration, not just run a single check standard.
- 7.5 - The recovery rate must be determined to show that matrix effects are under control, and it has to fall within the stated acceptance range. If the added chromium(VI) is not recovered as expected, the sample may contain reducing agents, which is a useful warning when dealing with organic matrices.
- 8, 9 and 10 - Results are calculated on a dry-matter basis, precision is supported by inter-laboratory data, and the test report must record the result, dry matter, recovery, method type, deviations and dates. That makes the result traceable and usable for compliance decisions.
What terms does oSIST prEN 17778:2026 define?
oSIST prEN 17778:2026 uses a small set of technical terms that matter for reporting and interpretation.
- chromium(VI) content / Cr(VI) - the amount of chromium(VI) measured after extraction with an aqueous salt solution at pH 7,0 to pH 8,0, reported as mg/kg dry matter.
- dry matter - the non-water portion of the sample, used here to express the final chromium(VI) result on a comparable basis.
- recovery rate - the percentage showing how much added chromium(VI) is found again after spiking, used to check matrix effects and method performance.
- fertilizing product blends - mixes of at least two components such as fertilizers, liming materials, soil improvers, growing media, inhibitors and plant biostimulants, where organic matter is present in at least one component.
- repeatability - closeness of results obtained under the same laboratory conditions, used here to judge short-term consistency of the method.
- reproducibility - closeness of results obtained in different laboratories, used here to show how the method performs across sites and operators.
- chromatographic conditions - the column, detector, mobile phase and operating settings used to separate and measure chromium(VI).
Who uses oSIST prEN 17778:2026?
oSIST prEN 17778:2026 is used by analytical laboratories that test organic and organo-mineral fertilizers, and by laboratories that examine fertilizing product blends containing organic matter. It is also relevant to fertilizer manufacturers, quality control teams, buyers, and conformity assessment or market surveillance bodies that need laboratory evidence for product compliance.
The document is especially relevant where chromium(VI) is a safety or quality parameter under Regulation (EU) 2019/1009. In practice, users need a method they can apply consistently to release batches, investigate nonconformities, compare results, or support regulatory files.
What changed in oSIST prEN 17778:2026 from the previous edition?
oSIST prEN 17778:2026 will supersede CEN/TS 17778:2022. The foreword lists these significant technical changes: adoption of the CEN Technical Specification as a European Standard with Annex ZA added, an updated introduction, clarified scope for fertilizing product blends, updated normative references and bibliography, an updated principle, shorter extraction time in 7.2.1, Clause 8 aligned with prEN 17773:2026 for dry-matter calculation and expression, a modified test report, Annex A added, and Annex B and Annex C updated with new chromatograms.
Which standards are used with oSIST prEN 17778:2026?
oSIST prEN 17778:2026 relies on a small group of companion standards for vocabulary, sample handling, dry matter and precision work.
| Standard | What it contributes |
|---|---|
| prEN 17773:2026 | Dry matter content, used to convert chromium(VI) results to a dry-matter basis |
| prEN 12944-1:2026 | General fertilizer vocabulary |
| prEN 12944-2:2026 | Fertilizer-specific terms and definitions |
| EN 1482-2:2024 | General sample preparation provisions |
| EN 1482-1 | Recommended general sampling provisions mentioned in the procedure |
| EN 1482-3 | Recommended sampling of static heaps mentioned in the procedure |
| prEN 17768 | Aqua regia digestion route for total element determination, cited in the principle |
| prEN 17770 | ICP-AES determination of total elements after aqua regia digestion, cited in the principle |
| ISO 5725-1 and ISO 5725-2 | Precision concepts and calculation of repeatability and reproducibility |
| ISO 13528 | Homogeneity testing used in the inter-laboratory study |
| ISO 17034 | Competence requirements for the reference material producer used in Annex A |
What does the oSIST prEN 17778:2026 document contain?
oSIST prEN 17778:2026 contains the full analytical method from sample preparation through result expression. Clause 5 lists reagents, Clause 6 lists equipment, and Clause 7 gives the extraction and chromatographic procedure for solid and liquid samples, including calibration and recovery checks.
Clause 8 provides the calculation and dry-matter expression of the chromium(VI) result, including the recovery-rate formula. Clause 9 summarizes precision from the inter-laboratory study, with repeatability and reproducibility data in table form. Annex B and Annex C provide example chromatographic setups and figures for the two detection approaches, while Annex A gives the study results that support the method's performance.
Relations
- Effective Date
- 01-Mar-2026
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Frequently Asked Questions
oSIST prEN 17778:2026 is a draft published by the Slovenian Institute for Standardization (SIST). Its full title is "Organic and organo-mineral fertilizers - Determination of chromium(VI) content". This standard covers: This document specifies a method for the determination of hexavalent chromium (chromium(VI)) in organic and organo-mineral fertilizers. The method specified is suitable to quantify the chromium(VI) content in organic and organo-mineral fertilizers down to 2 mg/kg dry matter. The results obtained from this method are strictly dependent on the extraction conditions. Results obtained by using other extraction procedures (extraction solution, pH of the extraction solution, extraction time, extraction temperature, etc.) are not comparable with the results produced by the procedure described in this document. This document is applicable to fertilizing products blends where a blend is a mix of at least two of the following components: fertilizers, liming materials, soil improvers, growing media, inhibitors, plant biostimulants and where organic matter is present in at least one of the products in the blend. In case a fertilizing product blend is composed only of inorganic products, the European Standard for inorganic fertilizers or liming materials applies. Variations in analytical methods for fertilizing product blends can lead to differing results as some components or matrix interactions can affect the outcome. Validation procedures have shown that developed standard methods are robust and reliable across diverse product compositions, but possible interferences and unexpected results when analysing fertilizing product blends are possible.
This document specifies a method for the determination of hexavalent chromium (chromium(VI)) in organic and organo-mineral fertilizers. The method specified is suitable to quantify the chromium(VI) content in organic and organo-mineral fertilizers down to 2 mg/kg dry matter. The results obtained from this method are strictly dependent on the extraction conditions. Results obtained by using other extraction procedures (extraction solution, pH of the extraction solution, extraction time, extraction temperature, etc.) are not comparable with the results produced by the procedure described in this document. This document is applicable to fertilizing products blends where a blend is a mix of at least two of the following components: fertilizers, liming materials, soil improvers, growing media, inhibitors, plant biostimulants and where organic matter is present in at least one of the products in the blend. In case a fertilizing product blend is composed only of inorganic products, the European Standard for inorganic fertilizers or liming materials applies. Variations in analytical methods for fertilizing product blends can lead to differing results as some components or matrix interactions can affect the outcome. Validation procedures have shown that developed standard methods are robust and reliable across diverse product compositions, but possible interferences and unexpected results when analysing fertilizing product blends are possible.
oSIST prEN 17778:2026 is classified under the following ICS (International Classification for Standards) categories: 65.080 - Fertilizers. The ICS classification helps identify the subject area and facilitates finding related standards.
oSIST prEN 17778:2026 has the following relationships with other standards: It is inter standard links to SIST-TS CEN/TS 17778:2023. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
oSIST prEN 17778:2026 is associated with the following European legislation: EU Directives/Regulations: 2019/1009; Standardization Mandates: M/564, M/564 AMD 1, M/564 AMD 2. When a standard is cited in the Official Journal of the European Union, products manufactured in conformity with it benefit from a presumption of conformity with the essential requirements of the corresponding EU directive or regulation.
oSIST prEN 17778:2026 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
01-marec-2026
Organska in organsko-mineralna gnojila - Določanje kroma Cr(VI)
Organic and organo-mineral fertilizers - Determination of chromium(VI) content
Organische und organisch-mineralische Düngemittel - Bestimmung des Gehalts an
Chrom(VI)
Engrais organiques et organo-minéraux - Détermination de la teneur en chrome(VI)
Ta slovenski standard je istoveten z: prEN 17778
ICS:
65.080 Gnojila Fertilizers
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
DRAFT
EUROPEAN STANDARD
prEN 17778
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2026
ICS 65.080 Will supersede CEN/TS 17778:2022
English Version
Organic and organo-mineral fertilizers - Determination of
chromium(VI) content
Engrais organiques et organo-minéraux - Organische und organisch-mineralische Düngemittel -
Détermination de la teneur en chrome(VI) Bestimmung des Gehalts an Chrom(VI)
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 260.
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
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 17778:2026 E
worldwide for CEN national Members.
prEN 17778:2026 (E)
Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Principle . 7
5 Reagents . 7
6 Apparatus . 8
7 Procedure . 9
7.1 Sampling and sample preparation . 9
7.2 Preparation of analytical solution . 9
7.2.1 Solid samples . 9
7.2.2 Liquid samples . 10
7.3 Chromatographic conditions . 10
7.4 Calibration. 10
7.5 Determination of the recovery rate . 11
8 Calculation and expression of results . 12
8.1 Calculation of chromium(VI) content . 12
8.2 Recovery rate (according to 7.5) . 13
8.3 Expression of results . 13
9 Precision . 13
9.1 Inter-laboratory study . 13
9.2 Repeatability . 13
9.3 Reproducibility . 13
10 Test report . 14
Annex A (informative) Results of the inter-laboratory study . 15
A.1 Inter-laboratory tests . 15
Annex B (informative) Chromatographic conditions for direct detection method . 17
B.1 General . 17
B.2 Example of ion chromatographic conditions . 17
B.2.1 Mobile phase reagents . 17
B.2.2 Instrumental conditions . 17
Annex C (informative) Chromatographic conditions for method with post-column reaction
............................................................................................................................................................... 19
C.1 General . 19
C.2 Chromatographic system and apparatus required . 19
C.3 Example of analytical conditions . 20
prEN 17778:2026 (E)
C.3.1 Mobile phase and post-column reagents . 20
C.3.2 Preparation of the mobile phase . 20
C.3.3 Preparation of post-column reagent . 20
C.3.4 Instrumental conditions . 21
C.4 Examples of chromatograms . 21
Annex ZA (informative) Relationship of this European Standard and the essential
requirements of Regulation (EU) 2019/1009 making available on the market of EU
fertilising products aimed to be covered . 23
Bibliography . 24
prEN 17778:2026 (E)
European foreword
This document (prEN 17778:2026) has been prepared by Technical Committee CEN/TC 260
“Fertilizers and liming materials”, the secretariat of which is held by DIN.
This document is currently submitted to the CEN Enquiry.
This document will supersede CEN/TS 17778:2022.
Compared to the previous edition, prEN 17778:2026 includes the following significant technical
changes:
— the CEN Technical Specification has been adopted as a European Standard including the
addition of Annex ZA;
— Introduction modified to add standards used as basis for the document and the description of
Annexes A, B and C;
— Scope (Clause 1) updated including clarifications on fertilizing product blends;
— Normative references (Clause 2) and Bibliography updated;
— Principle (Clause 4) updated;
— 7.2.1 modified to reduce the time for extraction;
— Clause 8, aligned to prEN 17773:2026 regarding the calculation and the expression of the
results for the dry matter;
— Test report (Clause 9) modified with addition of further information;
— Annex A (Results of the interlaboratory study) added;
— Annex B and Annex C modified with substitution of chromatograms.
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.
For relationship with EU Legislation, see informative Annex ZA, which is an integral part of this
document.
prEN 17778:2026 (E)
Introduction
Regulation (EU) 2019/1009 [2] lays down the rules on the making available on the market of EU
fertilizing products and the specific safety and quality requirements for the defined product
function categories (PFCs). Organic and organo-mineral fertilizers have been classified as
PFC 1(A) and PFC 1(B).
This document provides the method for the determination of the chromium(VI) extraction and
determination as mentioned in Annex I, Part II, PFC 1(A) and PFC 1(B) of Regulation (EU)
2019/1009 [2] in order to measure the compliance with the related requirement in that
Regulation.
Standards for determination of chromium(VI) in soil and waste [3], fertilizers [4] and for leather
[1] were studied and considered as a basis of this document.
This document contains two annexes (B and C) which describe two possible ways for determining
chromium(VI) by ion chromatography. Annex B describes an example of chromatographic
conditions for the direct detection method, while Annex C explains the chromatographic
conditions for method with post-column reaction. Both methods can be applied to determine
chromium(VI). The choice depends on the equipment available in laboratories.
The inter-laboratory study reflects the final statistical characteristics of the method for the
determination of chromium(VI) content in organic and organo-mineral fertilizers. The results are
given in Annex A (informative).
WARNING — Persons using this document should be familiar with usual laboratory practice. This
document does not purport to address all of the safety issues, if any, associated with its use. It is
the responsibility of the user to establish appropriate health and safety practices and to ensure
compliance with any national regulatory conditions.
IMPORTANT — It is absolutely essential that tests conducted according to this document are
carried out by suitably trained staff.
prEN 17778:2026 (E)
1 Scope
This document specifies a method for the determination of hexavalent chromium (chromium(VI))
in organic and organo-mineral fertilizers.
The method specified is suitable to quantify the chromium(VI) content in organic and organo-
mineral fertilizers down to 2 mg/kg dry matter.
The results obtained from this method are strictly dependent on the extraction conditions. Results
obtained by using other extraction procedures (extraction solution, pH of the extraction solution,
extraction time, extraction temperature, etc.) are not comparable with the results produced by
the procedure described in this document.
This document is applicable to fertilizing products blends where a blend is a mix of at least two of
the following components: fertilizers, liming materials, soil improvers, growing media, inhibitors,
plant biostimulants and where organic matter is present in at least one of the products in the
blend. In case a fertilizing product blend is composed only of inorganic products, the European
Standard for inorganic fertilizers or liming materials applies. Variations in analytical methods for
fertilizing product blends can lead to differing results as some components or matrix interactions
can affect the outcome. Validation procedures have shown that developed standard methods are
robust and reliable across diverse product compositions, but possible interferences and
unexpected results when analysing fertilizing product blends are possible.
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.
prEN 17773:2026, Organic and organo-mineral fertilizers — Determination of the dry matter
content
prEN 12944-1:2026, Fertilizers, liming materials and inhibitors — Vocabulary — Part 1: General
terms
prEN 12944-2:2026, Fertilizers, liming materials and inhibitors — Vocabulary — Part 2: Terms
relating to fertilizers
EN 1482-2:2024, Fertilizers, liming materials and inhibitors — Sampling and sample preparation
— Part 2: general sample preparation provisions
3 Terms and definitions
For the purposes of this document, the terms and definitions given in prEN 12944-1:2026 and
prEN 12944-2:2026 and the following apply.
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/
prEN 17778:2026 (E)
3.1
chromium(VI) content
Cr(VI)
amount of chromium(VI) in organic and organo-mineral fertilizers determined after extraction
with an aqueous salt solution at pH 7,0 to pH 8,0
Note 1 to entry: The chromium(VI) content is reported as chromium(VI) in milligrams per kilogram
(mg/kg), expressed as the dry mass of the sample.
[SOURCE: EN ISO 17075-2:2017 [1], 3.1, modified: “leather” is replaced by “organic and organo-
mineral fertilizers”]
4 Principle
To prove the compliance with the limit value for chromium(VI) in organic and organo-mineral
fertilizers, there is the possibility to choose between:
— Using a testing method determining the total chromium content, as long as the result of the
test shows a content below the limit value for chromium(VI). In such a case, it can be safely
assumed that the organic fertilizer or the organo-mineral fertilizer complies with the limit
value for chromium(VI).
— Using a testing method which determines only chromium(VI) content.
The determination of the total chromium in organic and organo-mineral fertilizers can be
performed by aqua regia digestion (prEN 17768 [5]) and ICP-AES determination (prEN 17770
[6]).
This standard specifies the procedure to directly determine the content of chromium(VI) in
organic and organo-mineral fertilizers: extractable chromium(VI) is leached from the sample in
phosphate buffer at pH 7,0 to pH 8,0. An aliquot of the filtered extract is analysed for
chromium(VI) using ion-exchange chromatography with UV-VIS detection.
5 Reagents
All reagents used shall have at least analytical grade.
5.1 Extraction solution
Dissolve 22,8 g dipotassium hydrogen phosphate trihydrate (K HPO ·3H O) in 1 000 ml water
2 4 2
(5.7), adjusted to pH 8,0 ± pH 0,1 with phosphoric acid solution (5.2). Degas this solution with
either argon or nitrogen (5.6) or ultrasonic bath.
Standard practice is to make up a fresh solution each day. However, the solution can be kept for
up to one week in a refrigerator at (4 ± 3) °C but shall be warmed to room temperature and
degassed prior to use.
5.2 Phosphoric acid solution
700 ml o-phosphoric acid, density ρ = 1,71 g/ml, made up to 1 000 ml with water (5.7).
First add approximately 200 ml of water (5.7) to a 1 000 ml volumetric flask, then add the 700 ml
of o-phosphoric acid and dilute to the mark with water (5.7).
5.3 Potassium dichromate (K Cr O ), dried for (16 ± 2) h at (105 ± 2) °C.
2 2 7
prEN 17778:2026 (E)
5.4 Chromium(VI) stock solution
Dissolve 2,829 g potassium dichromate (K Cr O ) (5.3) in water (5.7) in a volumetric flask and
2 2 7
make up to 1 000 ml with water (5.7). 1 ml of this solution contains 1 mg of chromium.
The solution can be kept for up to 12 months in a refrigerator at (4 ± 3) °C but shall be warmed to
room temperature prior to use.
It is also possible to use a commercial standard solution with a certified Cr(VI) concentration that
can be connected to national standards. Observe the expiry date or recommended shelf life stated
by the manufacturer.
5.5 Chromium(VI) standard solution
Pipette 1 ml of solution (5.4) into a 1 000 ml volumetric flask and make up to the mark with
extraction solution (5.1). 1 ml of this solution contains 1 μg of chromium.
The solution can be kept for up to one week in a refrigerator at (4 ± 3) °C but shall be warmed to
room temperature prior to use.
A stock solution of hexavalent chromium at this concentration level is an alternative available
commercially.
5.6 Argon or nitrogen, oxygen-free
Preference should be given to argon as an inert gas instead of nitrogen because argon has a higher
specific mass than air.
5.7 Distilled or deionised water, with a specific conductivity not higher than 0,2 mS/m at
25 °C, free from the elements to be determined.
5.8 Magnesium chloride hexahydrate (MgCl⋅6H O)
2 2
Dissolve 85,4 g of magnesium chloride hexahydrate (MgCl⋅6H O) in a 100 ml volumetric flask,
2 2
dilute with water (5.7), close and mix thoroughly.
6 Apparatus
Usual laboratory equipment and, in particular, the following.
−1
6.1 Suitable mechanical orbital shaker, (100 ± 10) min .
6.2 Conical flask, of capacity 250 ml, with stopper.
6.3 Aeration tube and flow meter, suitable for a flow rate of (50 ± 10) ml/min.
6.4 pH meter, with glass electrode.
6.5 Membrane filter, 0,45 μm pore size [polytetrafluoroethylene (PTFE) or polyamide 6.6].
6.6 Common laboratory glassware and pipettes.
6.7 Vacuum device, suitable for filtration of extraction solution, mobile phase, and sample
extracts.
6.8 Ion-exchange chromatograph, with UV/VIS detector or high-performance liquid
chromatography (HPLC) with anion-exchange column and UV/VIS detector. A photo diode
array detector (DAD) is recommended.
prEN 17778:2026 (E)
6.9 Analytical balance, capable of weighing to 0,1 mg.
6.10 Syringe membrane filters of polyamide 6.6 of 0,45 μm pore size, for filtration of standards.
6.11 Suitable vials for ion chromatography or HPLC.
7 Procedure
7.1 Sampling and sample preparation
Sampling is not part of the method specified in this document. Recommended sampling methods
are given in EN 1482-1 [7] and in EN 1482-3 [8].
It is important that the laboratory receives a sample that is representative of both the product
under consideration and the given analysis. The sample should not have been damaged or
changed during transport or storage.
Sample preparation shall be carried out in accordance with EN 1482-2:2024.
For products that can decompose or react when heated, grinding shall be carried out in order to
prevent heating.
Details about the sampling and sample preparation shall be given in the test report.
7.2 Preparation of analytical solution
7.2.1 Solid samples
The operator shall weigh approximately (2 ± 0,1) g of sample of organic or organo-mineral
fertilizer to the nearest 0,001 g with an analytical balance (6.9).
Following tasks shall be performed:
— Pipette 100 ml (V ) of degassed solution (5.1) into a 250 ml conical flask (6.2). Displace
oxygen by passing oxygen-free argon (or nitrogen) (5.6) into the flask for 5 min with a volume
flow of (50 ± 10) ml/min. Remove the aeration tube (6.3), add the sample and close the flask
with a stopper. Record the extract volume as V and the mass of the sample as m.
— Shake the conical flask with the sample for (30,0 ± 0,5) min on a mechanical orbital shaker at
−1
(100 ± 10) min (6.1) at room temperature to extract the chromium(VI).
— Shake the suspension in a smooth circular movement to keep the sample from adhering to
the wall of the flask and avoid shaking faster than specified.
— Immediately after completing the 30 min of extraction, filter the contents of the conical flask
through a membrane filter into a glass or plastic vessel with lid. Check the pH of the solution.
The pH of the solution shall be between 7,0 and 8,0. If the pH of the solution is not within this
range, start the complete procedure again. Consider using a smaller sample mass, if the pH is
not between 7,0 and 8,0. In this case, the quantification limit will be increased.
— Transfer an aliquot of the filtered extract into a vial (6.11). Instrumental determination of
chromium(VI) should be performed as soon as possible and no later than 60 min after the
extraction phase to avoid risks of reduction.
— If the sample is expected to contain a significant amount of chromium(III), 1 ml of magnesium
chloride solution (5.8) can be added before displacing oxygen into the 250 ml volumetric flask
(6.2) containing the 100 ml of the extraction solution (5.1).
prEN 17778:2026 (E)
7.2.2 Liquid samples
The operator shall weigh approximately (10 ± 0,1) g of sample of organic or organo-mineral
fertilizer to the nearest 0,001 g with an analytical balance (6.9).
The following tasks shall be performed:
— Pipette 100 ml (V ) of degassed solution (5.1) into a 250 ml conical flask (6.2). Displace oxygen
by passing oxygen-free argon (or nitrogen) (5.6) into the flask for 5 min with a volume flow of
(50 ± 10) ml/min. Remove the aeration tube (6.3), add the sample and close the flask with a
stopper. Record the extract volume as V (100 ml + sample volume in ml).
— Shake the conical flask with the sample for (10 ± 0,5) min on a mechanical orbital shaker at
−1
(100 ± 10) min (6.1) at room temperature to extract the chromium(VI).
— Shake the suspension in a smooth circular movement to keep the sample from adhering to the
wall of the flask and avoid shaking faster than specified.
— Immediately after completing the 10 min of extraction, filter the contents of the conical flask
through a membrane filter into a glass or plastic vessel with lid. Check
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