prEN ISO 22125-1

• Abstract:

  This document specifies a method for the measurement of 99Tc in all types of waters by liquid scintillation counting (LSC).; The method is applicable to test samples of supply/drinking water, rainwater, surface and ground water, as well as cooling water, industrial water, domestic, and industrial wastewater after proper sampling and handling, and test sample preparation. A filtration of the test sample is necessary.; The detection limit depends on the sample volume and the instrument used. The method described in this document, using currently available LSC instruments, has a detection limit of approximately 5 Bq·kg−1 to 20 Bq·kg−1, which is lower than the WHO criteria for safe consumption of drinking water (100 Bq l−1)[3]. These values can be achieved with a counting time of 30 min for a sample volume varying between 14 ml to 40 ml. The method presented in this document is not intended for the determination of ultra-trace amount of 99Tc.; The activity concentration values in this document are expressed by sample mass unit instead of sample volume unit as it is usually the case in similar standards. The reason is that 99Tc is measured in various matrix types such as fresh water or sea water, which have significant differences in density. The activity concentration values can be easily converted to sample volume unit by measuring the sample volume. However, it increases the uncertainty on the activity concentration result.; The method described in this document is applicable in the event of an emergency situation, but not if 99mTc is present at quantities that could cause interference and not if 99mTc is used as a recovery tracer.; The analysis of Tc adsorbed to suspended matter is not covered by this method.; It is the user's responsibility to ensure the validity of this test method for the water samples tested.

• Status: Not Published
• Publication Date: 11-Oct-2027
• ICS: 13.060.60 - Examination of physical properties of water
• Technical Committee: CEN/TC 230 - Water analysis
• Drafting Committee: CEN/TC 230 - Water analysis
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 08-Jun-2026
• Completion Date: 08-Jun-2026
• Ref Project: oSIST prEN ISO 22125-1:2026 - Water quality - Technetium-99- Part 1: Test method using liquid scintillation counting (ISO/DIS 22125-1:2026)

• Revises: EN ISO 22125-1:2019 - Water quality - Technetium-99 - Part 1: Test method using liquid scintillation counting (ISO 22125-1:2019)
• Effective Date: 05-Nov-2024

Overview

prEN ISO 22125-1:2026 – Water quality – Technetium-99 – Part 1: Test method using liquid scintillation counting – establishes a standard methodology for measuring the activity concentration of Technetium-99 (^99Tc) in water using liquid scintillation counting (LSC). Developed by CEN in collaboration with ISO, this document addresses the need to monitor ^99Tc, a significant anthropogenic radionuclide, in various water matrices including drinking, surface, ground, industrial, and wastewater. The method supports routine environmental monitoring, regulatory compliance, and emergency assessments for radioactivity in water.

Key Topics

• Scope and Applicability:
  The standard is designed to measure ^99Tc across a broad spectrum of water types, such as:

  • Supply/drinking water
  • Rainwater
  • Surface and ground water
  • Industrial water
  • Domestic and industrial wastewater
  • Cooling water

• Detection Limits:
  Using current LSC instruments and sample preparation protocols, the method achieves detection limits of approximately 5 to 20 Bq·kg^−1, surpassing the World Health Organization’s threshold for safe drinking water (100 Bq/l).

• Sample Preparation:

  • Proper sampling and handling are required to ensure representative results.
  • Filtration of samples is mandatory to remove suspended solids, as the method targets soluble ^99Tc forms.
  • Acidification and stabilization of samples with appropriate reagents is outlined.

• Reporting and Units:
  Activity concentrations are expressed per sample mass (Bq·kg^−1) rather than per volume, accommodating differing densities among water matrices (e.g., freshwater vs. seawater).

• Quality Assurance:
  Laboratories are responsible for verifying method validity for their samples. The document outlines requirements for quality control, instrument verification, and analyst competency.

Applications

• Routine Water Quality Assessment:
  The standard allows for reliable quantification of ^99Tc to meet national and international water safety regulations, facilitating compliance for:

  • Environmental monitoring agencies
  • Drinking water suppliers
  • Wastewater treatment facilities
  • Industrial operators

• Emergency Response:
  The methodology is suitable for rapid assessment of water radioactivity following nuclear incidents-provided interfering ^99mTc is not present in significant quantities.

• Regulatory Compliance and Reporting:
  Meets requirements for documentation and traceability of analytical data, supporting decision-making and public health protection.

• Research and Environmental Studies:
  Provides a robust framework for scientific investigations into radionuclide behavior, distribution, and fate in aquatic environments.

• Quality Control in Laboratories:
  Supports interlaboratory comparisons, method verification, and reference material analysis to ensure accuracy and reliability in radioanalytical laboratories.

Related Standards

For harmonized water quality and radioactivity measurement, prEN ISO 22125-1:2026 refers to several complementary standards, including:

• ISO 5667 Series:
  Guidance on water sampling techniques, sample preservation, and transportation.
• ISO 10703:
  High-resolution gamma-ray spectrometry for radionuclide analysis.
• ISO 11929:
  Determination of characteristic limits for ionizing radiation measurements.
• ISO 19361:
  Test methods using liquid scintillation counting for beta emitters.
• ISO 80000-10:
  Standardizes quantities and units in atomic and nuclear physics.
• ISO/IEC 17025:
  General requirements for the competence of testing and calibration laboratories.

By following prEN ISO 22125-1, laboratories and water utilities gain a validated tool for ensuring water safety and environmental protection with respect to Technetium-99, supporting national and international standards for radioactive substances in water.

SLOVENSKI STANDARD
01-maj-2026
Kakovost vode - Tehnecij Tc-99 - 1. del: Preskusna metoda s štetjem s
tekočinskim scintilatorjem (ISO/DIS 22125-1:2026)
Water quality - Technetium-99- Part 1: Test method using liquid scintillation counting
(ISO/DIS 22125-1:2026)
Wasserbeschaffenheit - Technetium 99 - Teil 1: Verfahren mit dem
Flüssigszintillationszähler (ISO/DIS 22125-1:2026)
Qualité de l'eau - Technétium-99 - Partie 1: Méthode d’essai par comptage des
scintillations en milieu liquide (ISO/DIS 22125-1:2026)
Ta slovenski standard je istoveten z: prEN ISO 22125-1
ICS:
13.060.50 Preiskava vode na kemične Examination of water for
snovi chemical substances
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 22125-1
ISO/TC 147/SC 3
Water quality — Technetium-99 —
Secretariat: AFNOR
Part 1:
Voting begins on:
Test method using liquid 2026-03-16
scintillation counting
Voting terminates on:
2026-06-08
Qualité de l'eau — Technétium-99 —
Partie 1: Méthode d’essai par comptage des scintillations en
milieu liquide
ICS: 17.240; 13.060.60
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
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RECIPIENTS OF THIS DRAFT ARE INVITED
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PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 22125-1:2026(en)
DRAFT
ISO/DIS 22125-1:2026(en)
International
Standard
ISO/DIS 22125-1
ISO/TC 147/SC 3
Water quality — Technetium-99 —
Secretariat: AFNOR
Part 1:
Voting begins on:
Test method using liquid
scintillation counting
Voting terminates on:
Qualité de l'eau — Technétium-99 —
Partie 1: Méthode d’essai par comptage des scintillations en
milieu liquide
ICS: 17.240; 13.060.60
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
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Published in Switzerland Reference number
ISO/DIS 22125-1:2026(en)
ii
ISO/DIS 22125-1:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 2
4 Symbols . 2
5 Principle . 4
6 Sampling and storage . 5
7 Procedure . 6
8 Quality assurance and quality control program . 6
8.1 General .6
8.2 Instrument verification .6
8.3 Contamination .6
8.4 Interference control .6
8.5 Method verification .6
8.6 Demonstration of analyst capability . .7
9 Expression of results . 7
9.1 General .7
9.2 Tracer activity added .7
99mTc 95m
9.2.1 or Tc is used as a recovery tracer .7
9.2.2 Re is used as a recovery tracer .7
9.3 Count rate and net count rate .7
95m 99m
9.3.1 Net count rate when Tc or Tc tracer is used as recovery tracer .7
9.3.2 Net count rate when Re tracer is used as recovery tracer .8
9.4 Chemical recovery .8
99m 95m
9.4.1 Tc or Tc is used as a recovery tracer .8
9.4.2 Re is used as a recovery tracer .8
9.5 Efficiency .8
9.6 Activity concentration of Tc . .8
9.7 Combined uncertainties .9
99m 95m
9.7.1 Tc or Tc is used as a recovery tracer .9
9.7.2 Re is used as a recovery tracer .9
9.8 Decision threshold .9
9.9 Detection limit .10
9.10 Probabilistically symmetric coverage interval .10
9.10.1 Limits of the probabilistically symmetric coverage interval .10
9.10.2 The shortest coverage interval .10
10 Test report .11
Annex A (informative) Example of LSC spectrum.12
Annex B (normative) Liquid scintillation cocktail .13
Annex C (normative) Quench curve . 14
Annex D (informative) Method 1 — Quaternary amine extraction chromatography resin .15
Annex E (informative) Method 2 — extraction chromatography resin containg CMPO dissolved
in TBP resin .18
Annex F (informative) Method 3 — Anion exchange resin .21
Bibliography .24

iii
ISO/DIS 22125-1:2026(en)
Foreword
ISO (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.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 3,
Radioactivity measurements.
This second edition cancels and replaces the first edition (ISO 22125-1:2019), which has been technically
revised.
The main changes are as follows:
— The format of the standard has been modified to align with the most recent ones;
— The most recent version of the introduction, sampling, quality assurance and quality control, and the
test report sections have been added;
— The formulae and their symbols have been reviewed.
A list of all the parts in the ISO 22125 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/DIS 22125-1:2026(en)
Introduction
Radionuclides are present throughout the environment; thus, water bodies (e.g. surface waters, ground
waters, sea waters) contain radionuclides, which can be of either natural or anthropogenic origin.
3 14 40
— Naturally-occurring radionuclides, including H, C, K and those originating from the thorium and
210 210 222 226 228 227 232 231 234 238
uranium decay series, in particular Pb, Po, Rn, Ra, Ra, Ac, Th, Pa, U and U,
can be found in water bodies due to either natural processes (e.g. desorption from the soil and runoff by
rain water) or released from technological processes involving naturally occurring radioactive materials
(e.g. mining, mineral processing, oil, gas and coal production, water treatment, and the production and
use of phosphate fertilisers).
55 59 63 90 99
— Anthropogenic radionuclides such as Fe, Ni, Ni, Sr, Tc, transuranic elements (e.g. Np, Pu, Am,
60 137
Cm), and some gamma emitting radionuclides, such as Co and Cs, can also be found in natural
waters. Small quantities of anthropogenic radionuclides can be discharged from nuclear facilities to the
environment as a result of authorized routine releases. The radionuclides present in liquid effluents
[1]
are usually controlled before being discharged to the environment and water bodies. Anthropogenic
radionuclides used for medical and industrial applications can be released to the environment after use.
Anthropogenic radionuclides are also found in waters due to contamination from fallout resulting from
above-ground nuclear detonations and accidents such as those that have occurred at the Chornobyl and
Fukushima nuclear facilities.
Radionuclide activity concentrations in water bodies can vary according to local geological characteristics
and climatic conditions and can be locally and temporally enhanced by releases from nuclear facilities
[2][3]
during planned, existing, and emergency exposure situations. Some drinking water sources can thus
contain radionuclides at activity concentrations that can present a human health risk. The World Health
[4]
Organization (WHO) recommends to routinely monitor radioactivity in drinking waters and to take
proper actions when needed to minimize the health risk.
National regulations usually specify the activity concentration limits that are authorized in drinking waters,
water bodies, and liquid effluents to be discharged to the environment. These limits can vary for planned,
existing, and emergency exposure situations. As an example, during either a planned or existing situation,
99 −1[4]
the WHO guidance level for Tc in drinking water is 100 Bq·l , see NOTES 1 and 2. Compliance with these
limits is assessed by measuring radioactivity in water samples and by comparing the results obtained, with
[5] [6]
their associated uncertainties, as specified by ISO/IEC Guide 98-3:2008 and ISO 5667-20:2008 .
[4]
NOTE 1 If the value is not specified in Annex 6 of Reference , the value has been calculated using the formula
[4] [7] [8]
provided in Reference and the dose coefficient data from References and .
[4]
NOTE 2 The guidance level calculated in Reference is the activity concentration that results in an effective dose
−1 −1
of 0,1 mSv·a to members of the public for an intake of 2 l·d of drinking water for one year. This is an effective
dose that represents a very low level of risk to human health and which is not expected to give rise to any detectable
[4]
adverse health effects .
This document contains method(s) to support laboratories, which need to determine Tc in water
samples. The method described in this document can be used for various types of waters (see Clause 1).
For radiometric methods, minor modifications such as sample volume and counting time can be made if
needed to ensure that the decision threshold, limit of detection, and uncertainties are below the required
limits. This can be done for several reasons such as emergency situations, lower national guidance limits
and operational requirements.
v
DRAFT International Standard ISO/DIS 22125-1:2026(en)
Water quality — Technetium-99 —
Part 1:
Test method using liquid scintillation counting
WARNING — Persons using this document should be familiar with normal laboratory practices. 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 determine
the applicability of any other restrictions.
NOTE — It is absolutely essential that tests conducted according to this document be carried out by
suitably trained staff.
1 Scope
WARNING — Persons using this document should be familiar with normal laboratory practices. 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 determine
the applicability of any other restrictions.
IMPORTANT — It is absolutely essential that tests conducted according to this document be carried
out by suitably trained staff.
This document specifies methods to determine Tc by liquid scintillation counting (LSC) in water supplies,
drinking water, rainwater, surface and ground water, marine water, as well as cooling water, industrial
water, domestic, and industrial wastewater after proper sampling, handling, and test sample preparation.
The detection limit depends on the sample volume, the instrument used, the background count rate, the
detection efficiency, the counting time, and the chemical yield. The minimum detectable activity of the
−1
methods described in this document, using currently available LSC apparatus, is approximately 5 Bq·l
−1 -1 [4]
to 20 Bq·l , which is lower than the WHO criteria for safe consumption of drinking water (100 Bq·l ).
These values can be achieved with a counting time of 60 min for a sample volume varying between 14 ml to
40 ml. The method presented in this document is not intended for the determination of ultra-trace activity
concentrations of Tc.
99m
The method described in this document is applicable in the event of an emergency situation, but not if Tc
99m
is present at quantities that could cause interference and not if Tc is used as a recovery tracer.
Filtration of the test sample is necessary for the methods described in this document if suspended solids are
present as the methods presented in this document can only be used to determine soluble Tc. The analysis
of Tc adsorbed to suspended matter is not covered by this method. The analysis of the insoluble fraction
requires a mineralization step that is not covered by this document. In this case, the measurement is made
on the different phases obtained. The final activity is the sum of all the measured activity concentrations.
It is the user’s responsibility to ensure the validity of this test method for the water samples tested.
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.

ISO/DIS 22125-1:2026(en)
ISO 5667-1, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes and sampling
techniques
ISO 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples
ISO 5667-10, Water quality — Sampling — Part 10: Guidance on sampling of waste waters
ISO 10703, Water quality — Determination of the activity concentration of radionuclides — Method by high
resolution gamma-ray spectrometry
ISO 11929, Determination of the characteristic limits (decision threshold, detection limit and limits of the
confidence interval) for measurements of ionizing radiation — Fundamentals and application
ISO 19361, Measurement of radioactivity — Determination of beta emitters activities — Test method using
liquid scintillation counting
ISO 20042, Measurement of radioactivity — Gamma emitting radionuclides — Generic test method using
gamma spectrometry
ISO 80000-10, Quantities and units — Part 10: Atomic and nuclear physics
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM:1995)
ISO/IEC Guide 99, International vocabulary of metrology — Basic and general concepts and associated terms
(VIM)
3 Terms, definitions and symbols
For the purposes of this document, the terms and definitions given in ISO 80000-10 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 http:// www .electropedia .org/
4 Symbols
For the purposes of this document, the symbols and designations given in ISO 80000-10, ISO 11929 series,
ISO/IEC Guide 98-3, ISO/IEC Guide 99 and the following apply.
99m 95m
A Activity of Tc or Tc, the tracer, measured in the final fraction using a different Bq
M
technique than LSC
A Activity of Tc, the measurand, added to prepare the quench curve Bq
Q
99m 95m
A Activity of Tc or Tc, the tracer, added Bq
T
α Probability of the false positive decision
β Probability of the false negative decision
-1
c Reagent concentration mol·l
99 -1
c Activity concentration of Tc, the measurand Bq∙l
A
99 -1
Decision threshold of Tc, the measurand Bq∙l

ISO/DIS 22125-1:2026(en)
99 -1
Detection limit of Tc, the measurand Bq∙l
99 -1
, Lower and upper limits of the probabilistically symmetric coverage interval of Tc, Bq∙l
the measurand, respectively
99 -1
Lower and upper limits of the shortest coverage interval of Tc, the measurand, Bq∙l
,
respectively
99 -1
Possible or assumed true quantity values of Tc, the measurand Bq∙l
99m 95m -1
Activity concentration of Tc or Tc tracer solution at the moment of separation Bq∙g
-1
c Massic concentration of Re tracer solution g∙g
SC
-1
DPM Disintegrations per minute min
ε Counting efficiency
Φ Distribution function of the standardized normal distribution; Φ(k ) = p applies
p
1−γ Probability for the coverage interval of Tc, the measurand
k Quantiles of the standardized normal distribution for the probabilities p
p
(for instance p = 1−α , 1− β or 1−γ/2 )
k Quantiles of the standardized normal distribution for the probabilities q
q
(for instance q = 1−α, 1− β or 1−γ/2)
-1
Decay constant of the isotope (ex: is the decay constant of Po)
λ s
m Sample mass kg
m Mass of the purified solution containing Tc ready for LSC measurement and for g
which a fraction is used for recovery determination
m Mass of aliquot of the purified Tc solution (m ), which is used for LSC determination g
1 0
m Mass of aliquot of the purified Tc solution (m ), which is used for recovery determi- g
2 0
nation
m Mass of Re carrier added g
c
m Mass of Re carrier initially present in the sample g
Ci
m Mass of Re carrier measured in the final fraction using a different technique than LSC g
CM
m Mass of carrier solution g
SC
m Mass of tracer solution g
ST
m Mass of tracer solution added to the spiked solution to determine the contribution in g
STS
Tc, the measurand, from the tracer solution
N Number of background counts measured in the LSC spectrum for a given time in the
region of interest of Tc, the measurand
N Number of counts measured in the LSC spectrum for a given time in the region of
g
interest of Tc, the measurand
p Probability for the coverage interval of Tc, the measurand

ISO/DIS 22125-1:2026(en)
q Probability for the coverage interval of Tc, the measurand
99 -1
r Background count rate in the region of interest of Tc, the measurand s
o
R Chemical recovery
c
99 -1
r Gross count rate in the region of interest of Tc, the measurand s
g
99 -1
r Net count rate of Tc, the measurand s
net
99 -1
r Net count rate of Tc, the measurand, added to the spiked solution to determine the s
SP
contribution in Tc from the tracer solution
99 -1
r Count rate contribution of Tc from the tracer s
T
99 -1
r Net count rate of Tc, the measurand, for unspiked reagent blank solution used to s
US
determine the contribution in Tc from the tracer solution
SQPE Spectral quench parameter of the external standard
t Time s
99 99
T Radioactive half-life of the isotope (ex: T Tc is the radioactive half-life of Tc) s
1/2 1/2
t Counting time of the background by LSC s
TDCR Triple to double coincidence ratio
t Counting time of the sample by LSC s
g
tSIE Transformed spectral index of the external standard
U Expanded uncertainty
u Standard uncertainty
Relative uncertainty
99 -1
Standard uncertainty of the activity concentration of Tc, the measurand Bq∙l
99 -1
Standard uncertainty of the estimator as a function of an assumed true value of Tc, Bq∙l
the measurand
99 -1
Standard uncertainty of an estimate of Tc, the measurand when the true value is Bq∙l
equivalent to the detection limit
V Sample volume l
ω Distribution function of the standardized normal distribution
-1
w Estimate of the calibration factor l
5 Principle
Technetium is mainly an anthropogenic element, but trace amounts are found in uranium ores. It has no
235 [9]
stable isotope. Technetium-99 is a significant fission product of U (approximatively 6 % yield ) with a
5 [10]
maximum beta-energy of (294 ± 1) keV and a half-life of (2,1 ± 0,1) × 10 years .
To determine Tc in water, a water sample is collected, filtered, acidified, and oxidized (see Clause 6). A
tracer is added before the separation to take into account the losses of recovery during the purification
step. Enough tracer is added to obtain a good statistical precision and be easily distinguished from a blank

ISO/DIS 22125-1:2026(en)
95m 99m
sample. The tracers that can be used are stable Re, Tc and Tc. Stable Re is often used as a recovery
[9]
tracer for Tc measurement due to its similar reactivity . It has the advantages of being easily available and
[11][12]
stable. Technetium is more volatile than Re when heated in acidic solutions . However, the difference
in volatility can be negligable in some acidic conditions, which have not being fully defined. Evaporation in a
HNO solution is believed to minimize HTcO volatilization compared to HCl. If Re is used as a recovery tracer
3 4
when the method includes a vaporization step, the laboratory shall ensure that there is no discrepensy in
chemical recovery between Re and Tc.
— When Re is used as a chemical recovery tracer, a sub-sample (m ) of known mass is taken before the LSC
measurement for the recovery determination. It is recommended to complete the recovery determination
before counting the sample.
Rhenium can be measured for example by:
[13]
— ICP-OES according to ISO 11885
[14]
— AAS according to ISO 15586
[15][16]
— UV-visible spectroscopy
99m 95m
— When Tc or Tc is used as a chemical recovery tracer, the chemical recovery is determined by
[9] 99m 95m
gamma spectrometry . Enough activity of Tc or Tc is added to obtain at least 10 000 counts when
counting the sample. The sample is directly placed in the gamma spectrometer, without any sample pre-
treatment. It is measured according to the instrument specifications and in accordance with ISO 10703
95m 99m
and ISO 20042. Tc or Tc should completely decay before measuring the sample by LSC. It can
99m 95m
take several days for Tc and several months for Tc depending on the initial quantity added. It is
99m 95m
strongly recommended to use Tc as a tracer rather than Tc due to a faster decay and also because
95m 99 [9]
commercial Tc standard solutions could contain a significant amount of Tc .
Technetium-99 is separated from potential interferences, which consist of any isotope that can cause the
liquid scintillator to emit light in the region of interest (ROI) of Tc, using one of the methods presented in
Annex D, Annex E, or Annex F.
After removal of the potential interferences, the chemical recovery (R ) is determined. The purified sample
c
is transferred into a liquid scintillation counting vial and a liquid scintillation cocktail is added according to
the specifications of Annex B. The sample is left in the dark for a few hours to reduce the luminescence as the
presence of luminescence prevents the proper measurement of the samples. Then, each vial is counted for
the appropriate amount of time by LSC (an example of LSC spectrum is shown in Annex A). If a luminescence
peak is observed, the sample is left in the dark for a few more hours until no luminescence is observed and
re-counted. For samples with a high activity concentration, dilution of the sample is required to avoid resin
and detector saturation during the separation and counting steps, respectively.
After measurement, the activity concentration of Tc is calculated and reported (see Clause 9 and Clause 10
for more details).
6 Sampling and storage
Sampling, handling, and storage of the water shall be done as specified in ISO 5667-1, ISO 5667-3 and
[17] [18]
ISO 5667-10 and guidance is given for the different types of water in ISO 5667-4 , ISO 5667-5:2006 , EN
[19] [20] [21] [22]
ISO 5667-6:2016 , ISO 5667-7:1993 , ISO 5667-11:2009 , and ISO 5667-14:2014 . It is important
that the laboratory receives a sample that is truly representative and has neither been damaged nor modified
during either transportation or storage.
The sample is filtered to remove suspended matter using a 0,45 μm filter. A smaller pore size filter can also
be used, but the filtration can be time consuming. Technetium (VII) is not strongly adsorbed to plastic or
glass container, but it can be reduced by the organic and inorganic matter in the sample to technetium oxide
−1
(TcO ). After filtration, the sample is acidified with nitric acid (HNO ) to 0,01 mol∙l HNO . Then, hydrogen
2 3 3
-
peroxide (H O ) is added to maintain Tc as TcO and reduce its adsorption to the container walls. An
2 2 4
−1
addition of H O to bring the sample to a concentration of 0,02 mol∙l is recommended.
2 2
ISO/DIS 22125-1:2026(en)
7 Procedure
Purify the sample from potential interferences. Purification methods are described in Annex D, Annex E, or
Annex F.
Measure Tc by LSC. Count the sample activity for the required period of time, typically for 1 h.
8 Quality assurance and quality control program
8.1 General
Measurement methods shall be performed by suitably skilled staff under a quality assurance program, such
as the one that is described in ISO/IEC 17025.
Special care shall be taken in order to limit the influence of parameters that can bias the measurement and
lead to a non-representative result. Failure to take sufficient precautions during the different steps of the
measurement process such as sampling, transportation and storage, reagents, transfer, and instrument can
require corrective factors to be applied to the measured results.
8.2 Instrument verification
Major instrument parameters such as detection efficiency, background signal, and quench factor shall be
periodically monitored within a quality assurance program established by the laboratory and in accordance
with the manufacturer’s instructions.
8.3 Contamination
Verify that the reagents and glassware used to perform the analysis have not been contaminated by Tc
and other beta emiting radionuclides present in the laboratory through the periodic performance of reagent
blank analysis. Laboratory procedures shall ensure that laboratory and equipment contamination as well as
sample cross contamination is avoided.
A minimum of one reagent blank sample shall be prepared with ultrapure water. It shall be filtered and
preserved as specified in Clause 6. The average of several reagent blanks can be used and is preferred. Also,
measuring reagent blank samples at regular intervals enables to rapidly detect a background issue when
measuring the samples.
Blanks without tracer should be occasionally prepared, even if not needed to calculate the activity
concentration of the measurand, to ensure the absence of tracer contamination. Tracer contamination
usually happens when the tracer has not been properly removed when cleaning dishware and that dishware
is re-used for another analysis. It will result in a higher than expected recovery and an erroneously low
measurand activity concentration will be reported.
The LSC vials used, glass or plastic, should have a reduced K content.
8.4 Interference control
It is the user's responsibility to ensure that all potential interferences have been removed. The removal
of potential interferences is limited by the decontamination factor of the method and the instrumental
capabilities.
8.5 Method verification
A periodic verification of the method accuracy should be performed. This can be accomplished by:
— participating in intercomparison exercises;
— analysing reference materials;

ISO/DIS 22125-1:2026(en)
— analysing spiked samples.
The repeatability of the method should be verified (for example, by replicate measurements).
The chemical recovery (R ) should be monitored for quality control (see subclause 9.4).
c
8.6 Demonstration of analyst capability
If an analyst has not performed this procedure before, a precision and bias test should be performed by
running a duplicate measurement of a reference or spiked material. Acceptance limits should be defined by
the laboratory. A similar evaluation should be performed by the analysts who routinely apply this procedure.
9 Expression of results
9.1 General
-1 -1
Measurement results are expressed as activity concentrations in Bq∙l or Bq∙kg with associated
uncertainties, presented in a test report. The coverage factor for the expanded uncertainty is specified in
the presentation of results.
9.2 Tracer activity added
99mTc 95m
9.2.1 or Tc is used as a recovery tracer
The activity of the tracer added (A ) is calculated using Formula (1):
T
(1)
9.2.2 Re is used as a recovery tracer
The amount of tracer added (m ) is calculated using Formula (2):
c
(2)
9.3 Count rate and net count rate
The count rates are calculated using Formula (3) and Formula (4):
(3)
(4)
It is recommended to count the background at least the same amount of time as for the sample.
95m 99m
9.3.1 Net count rate when Tc or Tc tracer is used as recovery tracer
95m 99m 99
When Tc or Tc is used as a recovery tracer, a significant amount of Tc can be present in the tracer.
To be able to calculate this contribution, a series of reagent blanks, with no tracer added, shall be prepared
using the same method as for the samples. After separation, half the method blanks are spiked with a known
amount of the tracer solution, m . The tracer is allowed to decay until it is undetectable by LSC. This can
STS
be done at the same time as the real samples to be more time efficient. The unspiked and spiked samples
are then measured by LSC and the average count rate of the spiked, r , and unspiked, r , reagent blanks
SP US
is determined. The contribution of Tc from the tracer, r , varies as a function of the sample recovery, R ,
T c
ISO/DIS 22125-1:2026(en)
but not the instrumental background. Therefore, the net count rate, r , is calculated based on the mass of
net
tracer added to the sample, m , and the background count rate, r , and is determined using Formula (5):
ST 0
(5)
9.3.2 Net count rate when Re tracer is used as recovery tracer
The net count rate of the sample (r ) is calculated using Formula (6), which corrects for the fact that only a
net
fraction of the sample is measured by LSC.
(6)
9.4 Chemical recovery
99m 95m
9.4.1 Tc or Tc is used as a recovery tracer
The chemical recovery (R ) is calculated using Formula (7):
c
(7)
9.4.2 Re is used as a recovery tracer
The chemical recovery (R ) is calculated using Formula (8):
c
(8)
The relative standard uncertainty of R is calculated using Formula (9):
c
(9)
9.5 Efficiency
The efficiency is determined using a quench curve. The instruction to prepare the quench curve are
described in Annex C.
9.6 Activity concentration of Tc
The activity concentration (c ) of Tc in the test sample is calculated using Formula (10):
A
(10)
The term w in Formula (10) is isolated in Formula (11) to calculate the decision threshold and the detection
limit.
(11)
ISO/DIS 22125-1:2026(en)
9.7 Combined uncertainties
This subclause contains the Formulae needed to calculate the uncertainty on c . The uncertainties on λ, T ,
A 1/2
t and t are considered negligible for the calculation of u(c ). According to ISO/IEC Guide 98-3, the combined
g 0 A
uncertainty of c is calculated using Formula (12):
A
(12)
If needed, calculate the standard uncertainty of c as a function of its true value, noted , using
A
Formula (13):
(13)
99m 95m
9.7.1 Tc or Tc is used as a recovery tracer
The relative standard uncertainty of w is calculated using Formula (14):
(14)
The relative standard uncertainty of R is calculated using Formula (15)):
c
(15)
The relative standard uncertainty of A is calculated using Formula (16):
T
(16)
9.7.2 Re is used as a recovery tracer
The relative standard uncertainty of w is calculated using Formula (17):
(17)
The relative standard uncertainty of R is calculated using Formula (9).
c
9.8 Decision threshold
-1
The decision threshold , expressed in Bq∙l , is obtained from Formula (18) (see ISO 11929 series). This
yields:
(18)
where α = 0,05 with k = 1,65, are values often chosen by default.
1 − α
When , is calculated using Formula (19):
(19)
When the background is very low, or when , is calculated with Formula (20) according to ISO 11929
series:
(20)
ISO/DIS 22125-1:2026(en)
9.9 Detection limit
The detection limit is calculated using the implicit Formula (21) according to ISO 11929 series:
(21)
β = 0,05 with k = 1,65 are often chosen by default.
1 − β
The detection limit can be calculated by solving Formula (21) for or, more simply, by iteration with a
starting approximation .
When taking k = k = k and the solution of Formula (21) the detection limit is given by Formula (22):
1 − α 1 − β
(22)
where α= 0,05 with k = 1,65, are values often chosen by default.
1-α
9.10 Probabilistically symmetric coverage interval
9.10.1 Limits of the probabilistically symmetric coverage interval
The lower, , and upper, , coverage limits are calculated using Formula (23) and Formula (24) according
to ISO 11929 series:
(23)
(24)
where
being the distribution function of the standardized normal distribution;
(1-γ) is the probability for the coverage interval of the measurand;
ω = 1 can be set if .
In this case the probabilistically symmetric coverage interval is given by Formula (25):
(25)
γ
γ= 0,05 and then, k = 1,96 are values often chosen by default.
1-γ/2
9.10.2 The shortest coverage interval
As described in
...