CEN/TS 17721:2022

SLOVENSKI STANDARD
01-februar-2023
Rastlinski biostimulanti - Določevanje pH-vrednosti za tekoče mikrobne
biostimulante/mikrobne proizvode - Določevanje pH-vrednosti
Plant biostimulants - Determination of the pH for liquid microbial plant biostimulants/pH in
microbial products - Determination of pH
Pflanzen-Biostimulanzien - Bestimmung des pH Wertes für flüssige mikrobielle Pflanzen-
Biostimulanzien/pH Wert in mikrobiellen Produkten - Bestimmung des pH Wertes
Biostimulants des végétaux - Détermination du pH des biostimulants microbiens liquides
des végétaux/pH dans les produits microbiens - Détermination du pH
Ta slovenski standard je istoveten z: CEN/TS 17721:2022
ICS:
65.080 Gnojila Fertilizers
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

CEN/TS 17721
TECHNICAL SPECIFICATION
SPÉCIFICATION TECHNIQUE
March 2022
TECHNISCHE SPEZIFIKATION
ICS 65.080
English Version
Plant biostimulants - Determination of the pH for liquid
microbial plant biostimulants/pH in microbial products -
Determination of pH
Biostimulanzien für die pflanzliche Anwendung -
Bestimmung des pH-Wertes für flüssige mikrobielle
Biostimulanzien für die pflanzliche Anwendung/pH-
Wert in mikrobiellen Produkten - Bestimmung des pH-
Wertes
This Technical Specification (CEN/TS) was approved by CEN on 3 January 2022 for provisional application.

The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to
submit their comments, particularly on the question whether the CEN/TS can be converted into a European Standard.

CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS
available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in
parallel to the CEN/TS) until the final decision about the possible conversion of the CEN/TS into an EN is reached.

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, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 17721:2022 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 . 10
5 Apparatus and materials . 10
5.1 General . 10
5.2 pH measuring apparatus . 10
5.3 Water . 11
5.4 pH meter . 11
5.5 pH electrode . 11
5.6 Standard buffer solutions . 12
5.7 Storage solution for the pH electrodes . 12
6 Sampling . 12
7 Procedure. 12
7.1 General . 12
7.2 Test conditions . 12
7.3 Calibration . 12
7.4 Number of determinations . 13
7.5 Measuring the pH value . 13
8 Evaluation . 13
9 Test report . 13
Bibliography . 15

European foreword
This document (CEN/TS 17721:2022) has been prepared by Technical Committee CEN/TC 455 “Plant
Biostimulants”, the secretariat of which is held by AFNOR.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a Standardization Request given to CEN by the European
Commission and the European Free Trade Association.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN/CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to announce this Technical Specification: 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, Turkey and the United
Kingdom.
Introduction
This document was prepared by the experts of CEN/TC 455 “Plant Biostimulants”. The European
Committee for Standardization (CEN) was requested by the European Commission (EC) to draft
European standards or European standardization deliverables to support the implementation of
Regulation (EU) 2019/1009 of the European Parliament and of the Council of 5 June 2019 laying down
rules on the making available on the market of EU fertilising products (“FPR” or “Fertilising Products
Regulation”). This standardization request, presented as M/564, also contributes to the Communication
on “Innovating for Sustainable Growth: A Bio economy for Europe”. Working Group 5 “Labelling and
denominations” was created to develop a work program as part of this standardization request.
Technical Committee CEN/TC 455 “Plant Biostimulants” was established to carry out the work program
that will prepare a series of standards. The interest in biostimulants has increased significantly in Europe
as a valuable tool to use in agriculture. Standardization was identified as having an important role in
order to promote the use of biostimulants. The work of CEN/TC 455 seeks to improve the reliability of
the supply chain, thereby improving the confidence of farmers, industry, and consumers in biostimulants,
and will promote and support commercialisation of the European biostimulant industry.
Liquid microbial plant biostimulants have a pH optimal for contained microorganisms and for plants [1].
WARNING — Persons using this document should be familiar with normal laboratory practice. This
document does not purport to address all of the safety problems, if any, associated with its use. It is the
responsibility of the user to establish appropriate safety and health practices and to ensure compliance
with any national regulatory conditions.
IMPORTANT — It is absolutely essential that tests conducted in accordance with this document be
carried out by suitably trained staff.
1 Scope
This document specifies a method for laboratory measurement of the pH value in liquid microbial plant
biostimulants, using pH electrodes with a glass membrane.
From the scope of this document plant biostimulants other than microbial plant biostimulants are
excluded because there is no essential requirement in the Regulation (EU) 2019/1009 [1] for measuring
the pH of non-microbial plant biostimulants.
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 17702-1, Plant biostimulants - Sampling and sample preparation - Part 1: Sampling
CEN/TS 17702-2, Plant biostimulants - Sampling and sample preparation - Part 2: Sample preparation
CEN/TS 17724, Plant biostimulants - Terminology
EN ISO 3696:1995, Water for analytical laboratory use - Specification and test methods (ISO 3696:1987)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in CEN/TS 17724 and the following
apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
pH
measure for the acidic or basic reaction of an aqueous solution or dispersion
Note 1 to entry: Notation of pH: the p and the H are vertically on one line.
Note 2 to entry: The acidic reaction is determined by the activity of the existing hydrogen ions. The basic reaction
is determined by the activity of the existing hydroxide ions. The direct relationship between the activities of the
hydrogen ions and the hydroxide ions is described by the ionic product of the water.
3.2
pH value
decadal logarithm of the hydrogen ion activity multiplied with (−1)
 
m ⋅γ

a
H++mH,
H+
 
pH=pa =−=lg  −lg
H+

 
mm

 
with
am= ⋅γ
H++H mH, +
where
a is the activity of the hydrogen ion, expressed in mole per kilogram (mol/kg);
H+
m is the standard molality expressed in mole per kilogram (mol/kg);
γ is the activity coefficient of the hydrogen ion;
m,H+
m is the molality of the hydrogen ion, expressed in mole per kilogram (mol/kg).
H+
Note 1 to entry: The pH value is not measurable as a measure of a single ion activity. Therefore, pH(PS) values of
solutions of primary reference material (PS, en: Primary Standard) are determined, which are approximated to it
and can be attributed to it. This is based on a worldwide agreement; see EN ISO 80000-9:2019, Annex C [3].
3.3
potentiometric measuring chain
combination of electrochemical half cells
3.4
pH (combination) electrode
pH (single-rod) measuring chain
potentiometric measuring chain (3.3) providing a voltage which depends on the pH value (3.2) of the
measuring solution
Note 1 to entry: One of the two electrochemical half cells is the pH measuring electrode, the second is a reference
electrode (3.5) (see Figure 1).
Note 2 to entry: The use of an integrated temperature sensor during the measurement of the pH value is
recommended (see Figure 1).
Key
1 reference electrode, consisting in 2, 3 and 4
2 reference element
3 reference electrolyte
4 diaphragm
5 pH measuring electrode, consisting of 6, 7 and 8
6 reference element
7 glass membrane
8 internal buffer
9 temperature sensor
U pH proportional voltage
Figure 1 — Design of a pH electrode with glass membrane and temperature sensor (schematic
illustration)
Note 3 to entry: This document refers to pH electrodes with glass membranes. The electrode shaft should be made
of material resistant to chemicals and solvents.
3.5
reference electrode
electrode providing a constant potential which is independent from the pH value (3.2) of the measuring
solution
Note 1 to entry: At present, the most commonly used type is the silver/silver chloride reference electrode,
...