ISO/DIS 22125-1

ISO/TC 147/SC 3

Secretariat: AFNOR

Date: 2026-01-19

Water quality — Technetium-99 —

Part 1:
Test method using liquid scintillation counting

Qualité de l'eau — Technétium-99 —

Partie 1: Méthode d’essai par comptage des scintillations en milieu liquide

DIS stage

© ISO 2026

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Contents

Foreword

Introduction

Scope

Normative references

Terms, definitions and symbols

Symbols

Principle

Sampling and storage

Procedure

Quality assurance and quality control program

General

Instrument verification

Contamination

Interference control

Method verification

Demonstration of analyst capability

Expression of results

General

Tracer activity added

Count rate and net count rate

Chemical recovery

Efficiency

Activity concentration of 99 Tc

Combined uncertainties

Decision threshold

Detection limit

Probabilistically symmetric coverage interval

Test report

(informative) Example of LSC spectrum

(normative) Liquid scintillation cocktail

(normative) Quench curve

(informative) Method 1 — Quaternary amine extraction chromatography resin

(informative) Method 2 — extraction chromatography resin containg CMPO dissolved in TBP resin

(informative) Method 3 — Anion exchange resin

Bibliography

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.

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.

• Naturally-occurring radionuclides, including ³H, ¹⁴C, ⁴⁰K and those originating from the thorium and uranium decay series, in particular ²¹⁰Pb, ²¹⁰Po, ²²²Rn, ²²⁶Ra, ²²⁸Ra, ²²⁷Ac, ²³²Th, ²³¹Pa, ²³⁴U and ²³⁸U, 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).
• Anthropogenic radionuclides such as ⁵⁵Fe, ⁵⁹Ni, ⁶³Ni, ⁹⁰Sr, ⁹⁹Tc, transuranic elements (e.g. Np, Pu, Am, Cm), and some gamma emitting radionuclides, such as ⁶⁰Co and ¹³⁷Cs, 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 are usually controlled before being discharged to the environment^[1] 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 during planned, existing, and emergency exposure situations.^[2][3] Some drinking water sources can thus contain radionuclides at activity concentrations that can present a human health risk. The World Health Organization (WHO) recommends to routinely monitor radioactivity in drinking waters^[4] 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, the WHO guidance level for ⁹⁹Tc in drinking water is 100 Bq·l^−1[4], see NOTES 1 and 2. Compliance with these limits is assessed by measuring radioactivity in water samples and by comparing the results obtained, with their associated uncertainties, as specified by ISO/IEC Guide 98-3 [5] and ISO 5667-20 [6].

NOTE 1 If the value is not specified in Annex 6 of Reference ^[4], the value has been calculated using the formula provided in Reference ^[4] and the dose coefficient data from References ^[7] and ^[8].

NOTE 2 The guidance level calculated in Reference ^[4] is the activity concentration that results in an effective dose of 0,1 mSv·a⁻¹ to members of the public for an intake of 2 l·d⁻¹ 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 adverse health effects^[4].

This document contains method(s) to support laboratories, which need to determine ⁹⁹Tc 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.

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.

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 ⁹⁹Tc 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 methods described in this document, using currently available LSC apparatus, is approximately 5 Bq·l⁻¹ to 20 Bq·l⁻¹, which is lower than the WHO criteria for safe consumption of drinking water (100 Bq·l^-1).^[4] 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 ⁹⁹Tc.

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.

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 ⁹⁹Tc. The analysis of ⁹⁹Tc 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.

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 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)

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/

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.

Technetium is mainly an anthropogenic element, but trace amounts are found in uranium ores. It has no stable isotope. Technetium-99 is a significant fission product of ²³⁵U (approximatively 6 % yield^[9]) with a maximum beta-energy of (294 ± 1) keV and a half-life of (2,1 ± 0,1) × 10⁵ years^[10].

To determine ⁹⁹Tc 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 sample. The tracers that can be used are stable Re, ^95mTc and ^99mTc. Stable Re is often used as a recovery tracer for Tc measurement due to its similar reactivity^[9]. It has the advantages of being easily available and stable. Technetium is more volatile than Re when heated in acidic solutions ^[11][12]. However, the difference in volatility can be negligable in some acidic conditions, which have not being fully defined. Evaporation in a HNO₃ solution is believed to minimize HTcO₄ volatilization compared to HCl. If Re is used as a recovery tracer 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 (m₂) 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:

• ICP-OES according to ISO 11885
• AAS according to ISO 15586
• UV-visible spectroscopy^[15][16]
• When ^99mTc or ^95mTc is used as a chemical recovery tracer, the chemical recovery is determined by gamma spectrometry ^[9]. Enough activity of ^99mTc or ^95mTc 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 and ISO 20042. ^95mTc or ^99mTc should completely decay before measuring the sample by LSC. It can take several days for ^99mTc and several months for ^95mTc depending on the initial quantity added. It is strongly recommended to use ^99mTc as a tracer rather than ^95mTc due to a faster decay and also because commercial ^95mTc standard solutions could contain a significant amount of ⁹⁹Tc ^[9].

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 ⁹⁹Tc, using one of the methods presented in Annex D, Annex E, or Annex F.

After removal of the potential interferences, the chemical recovery (R_c) is determined. The purified sample 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 ⁹⁹Tc is calculated and reported (see Clause 9 and Clause 10 for more details).

Sampling, handling, and storage of the water shall be done as specified in ISO 5667-1, ISO 5667-3 and ISO 5667-10 and guidance is given for the different types of water in  ISO 5667-4, ISO 5667-5 [18], EN ISO 5667-6 [19], ISO 5667-7 [20], ISO 5667-11 [21] , and ISO 5667-14 [22] . 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 (TcO₂). After filtration, the sample is acidified with nitric acid (HNO₃) to 0,01 mol∙l⁻¹ HNO₃. Then, hydrogen peroxide (H₂O₂) is added to maintain Tc as TcO₄^- and reduce its adsorption to the container walls. An addition of H₂O₂ to bring the sample to a concentration of 0,02 mol∙l⁻¹ is recommended.

Purify the sample from potential interferences. Purification methods are described in Annex D, Annex E, or Annex F.

Measure ⁹⁹Tc by LSC. Count the sample activity for the required period of time, typically for 1 h.

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.

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.

Verify that the reagents and glassware used to perform the analysis have not been contaminated by ⁹⁹Tc 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 ⁴⁰K content.

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.

A periodic verification of the method accuracy should be performed. This can be accomplished by:

• participating in intercomparison exercises;
• analysing reference materials;
• analysing spiked samples.

The repeatability of the method should be verified (for example, by replicate measurements).

The chemical recovery (R_c) should be monitored for quality control (see subclause 9.4).

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.

Measurement results are expressed as activity concentrations in Bq∙l^-1 or Bq∙kg^-1 with associated uncertainties, presented in a test report. The coverage factor for the expanded uncertainty is specified in the presentation of results.

The activity of the tracer added (A_T) is calculated using Formula (1):

(1)

The amount of tracer added (m_c) is calculated using Formula (2):

(2)

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.

When ^95mTc or ^99mTc is used as a recovery tracer, a significant amount of ⁹⁹Tc 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_STS. The tracer is allowed to decay until it is undetectable by LSC. This can 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_SP, and unspiked, r_US, reagent blanks is determined. The contribution of ⁹⁹Tc from the tracer, r_T, varies as a function of the sample recovery, R_c, but not the instrumental background. Therefore, the net count rate, r_net, is calculated based on the mass of tracer added to the sample, m_ST, and the background count rate, r₀, and is determined using Formula (5):

(5)

The net count rate of the sample (r_net) is calculated using Formula (6), which corrects for the fact that only a fraction of the sample is measured by LSC.

(6)

The chemical recovery (R_c) is calculated using Formula (7):

(7)

The chemical recovery (R_c) is calculated using Formula (8):

(8)

The relative standard uncertainty of R_c is calculated using Formula (9):

(9)

The efficiency is determined using a quench curve. The instruction to prepare the quench curve are described in Annex C.

The activity concentration (c_A) of ⁹⁹Tc in the test sample is calculated using Formula (10):

(10)

The term w in Formula (10) is isolated in Formula (11) to calculate the decision threshold and the detection limit.

(11)

This subclause contains the Formulae needed to calculate the uncertainty on c_A. The uncertainties on λ, T_1/2, t_g and t₀ are considered negligible for the calculation of u(c_A). According to ISO/IEC Guide 98-3, the combined uncertainty of c_A is calculated using Formula (12):

(12)

If needed, calculate the standard uncertainty of c_A as a function of its true value, noted , using Formula (13):

(13)

The relative standard uncertainty of w is calculated using Formula (14):

(14)

The relative standard uncertainty of R_c is calculated using Formula (15)):

(15)

The relative standard uncertainty of A_T is calculated using Formula (16):

(16)

The relative standard uncertainty of w is calculated using Formula (17):

(17)

The relative standard uncertainty of R_c is calculated using Formula (9).

The decision threshold , expressed in Bq∙l^-1, is obtained from Formula (18) (see ISO 11929 series). This yields:

(18)

where α = 0,05 with k_{1 − α} = 1,65, are values often chosen by default.

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)

The detection limit is calculated using the implicit Formula (21) according to ISO 11929 series:

(21)

β = 0,05 with k_{1 − β} = 1,65 are often chosen by default.

The detection limit can be calculated by solving Formula (21) for or, more simply, by iteration with a starting approximation .

When taking k_{1 − α} = k_{1 − β} = k and the solution of Formula (21) the detection limit is given by Formula (22):

(22)

where α= 0,05 with k_1-α= 1,65, are values often chosen by default.

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= 0,05 and then, k_1-γ/2 = 1,96 are values often chosen by default.

As described in detail in ISO 11929 series the lower limit of the shortest coverage interval, , and the upper limit of the shortest coverage interval, , are calculated from a primary measurement result, c_A, of the measurand and the standard uncertainty, u(c_A) , associated with c_A, either by Formula (26):

(26)

or in the case where , by Formula (27):

(27)

  being the distribution function of the standardized normal distribution;

The relations 0 ≤ < apply and the approximation of Formula (25) is valid.

The test report should conform to the requirements of ISO/IEC 17025 and shall contain at least the following information:

1. reference to this document, i.e. ISO 22125-1:20XX;
2. the method used from either Annex D, E, or F;
3. identification of the sample;
4. units in which the results are expressed;
5. the test result:
6. when the activity concentration, cA, is compared with the decision threshold (see ISO 11929 series);
7. if the result is less than the decision threshold, the result of the measurement is expressed as ≤ ,
8. if the result is greater than the decision threshold, the result of the measurement is expressed as or with the associated k value,
9. when the activity concentration, c_A is compared with the detection limit;
10. if the result is less than the detection limit, the result of the measurement is expressed as ≤ ,
11. if the result is greater than the detection limit, the result of the measurement is expressed as or with the associated k value.
12. the date used to calculate the sample activity concentration;
13. the date of issue of the report.

Complementary information can be provided such as the following:

a) relevant dates such as the date of sampling, the date of the sample receipt, and the date of the analysis start, where these dates are critical to the validity and application of the results;

b) the uncertainty can also be expressed as the limits of the probabilistically symmetric coverage interval , ,  and/or the limits of the shortest coverage interval , ;

c) probabilities α, β and (1 − γ);

d) decision threshold and the detection limit;

e) if the detection limit exceeds the guideline value, it shall be documented that the method is not suitable for the measurement purpose;

f)  mention of any relevant deviation from the standard likely to affect the results and any unusual features observed.

NOTE It is occasionally requested by the customer or regulator to compare the primary measurement result, , with the detection limit, , in order to decide whether the physical effect is recognized or not. Such stipulation is not in accordance with the ISO 11929 series. The consequence is that it is decided too frequently that the physical effect is absent while in fact it is not.

1. 
   (informative)
   
   Example of LSC spectrum

Key

Ordinate Counts

Abscissa Channels

Figure A.1 — Example of 99Tc LSC spectrum (5 Bq counted 30 minutes)

1. 
   (normative)
   
   Liquid scintillation cocktail

Chose the scintillation cocktail according to the characteristics of the test sample to be analysed (acidic, alkaline, or precipitate) and according to the properties of the detection equipment.

The characteristics of the scintillation cocktail shall ensure the mixture is homogeneous and stable at the given mixing ratio and at the temperature of the counting system.

It is recommended to:

• store the scintillation cocktail in the dark at room temperature; and,
• avoid exposure to direct sunlight or fluorescent light in order to prevent interfering luminescence, particularly just before counting; and,
• comply with storage conditions specified by the scintillation cocktail supplier.

The mixtures of scintillation cocktail and test sample taken for testing should be disposed of as chemical waste, and, depending on the levels of radioactivity, may require disposal as radioactive waste.

1. 
   (normative)
   
   Quench curve

A quench calibration curve shall be constructed to determine the measurement efficiency. This curve is made by adding a known amount of ⁹⁹Tc to blank aliquots and varying the concentration of a quenching agent. The quench curve is obtained by plotting the detection efficiency (ε) against the quenching index value such as tSIE, SQPE, TDCR, or direct DPM. The samples collected after the chromatographic separation should have a similar quenching index for a specific type of matrix as the chemical medium is very similar.

The quench curve is obtained with a series of working standards (e.g. 10), presenting different levels of quench. The matrix of the working standards is representative of the test sample matrix to be measured (same scintillation liquid, same ratio scintillation liquid‑test sample). The working standards is prepared as follows:

• add an equivalent quantity of ⁹⁹Tc standard to each vial (A_Q). The activity of the standard shall be sufficient for the counting rate to achieve a known statistical precision, even in the case of a strong quench;
• add the blank reference solution (same matrix as the sample);
• add the scintillation cocktail;

At least one working standard is used without addition of the quenching agent. An increasing quantity of quenching agent such as tartrazine and nitromethane is added to the other working standard solutions to simulate the expected range of quench values encountered in the samples to be measured.

The standards are counted by liquid scintillation counting to determine the net count rate from ⁹⁹Tc (r_net) in the counting window of the test samples. The counting efficiency (ε) is calculated for each vial using Formula (C.1):

(C.1)

The quench parameter is usually generated by the instrument. The counting efficiency (ε) of each vial is plotted on as a function of the quench parameter Q. A polynomial regression curve and its equation are calculated using a software. The shape of the quench calibration curve cannot be predicted.

1. 
   (informative)
   
   Method 1 — Quaternary amine extraction chromatography resin
   1. Principle

The sample is filtered, acidified, and oxidized as described in Clause 6. The tracer is added. Technetium-99 is purified from potential interferences by passing the solution through a quaternary amine extraction chromatography resin, which selectively extracts Tc. Then, ⁹⁹Tc is measured by LSC. An approximate detection limit of 5 Bq·l⁻¹ is usually obtained using this method. This method is based on reference ^[23].

• 1. Reagents and apparatus
     1. Reagents

Use only reagents of recognized analytical grade.

• • • 1. Tracer solution, Re or ^95mTc or ^99mTc standard solution.
      2. Chromatographic extraction resin with a quaternary amine, 2 ml cartridge.
      3. Nitric acid solution, c(HNO₃) = 0,1 mol·l⁻¹.
      4. Nitric acid solution, c(HNO₃) = 0,01 mol·l⁻¹.
      5. Nitric acid + hydrofluoric acid solution, c(HF) = 0,5 mol·l⁻¹ in c(HNO₃) = 0,02 mol·l⁻¹.
      6. Nitric acid solution, c(HNO₃) = 2 mol·l⁻¹
      7. Nitric acid solution, c(HNO₃) = 12 mol·l⁻¹
      8. Ultrapure water, with a resistivity of more than 18,2 MΩ cm at 25 °C and total organic carbon less than 1 μg∙l⁻¹.
      9. Liquid scintillation cocktail, chosen according to the specifications of Annex B.
      10. ⁹⁹Tc standard solution.
    1. Apparatus

Usual laboratory equipment including the following:

• • • 1. Analytical balance, accuracy 0,1 mg.
      2. Disposable polypropylene centrifuge container, minimum volume of 50 ml.
      3. Multi-hole vacuum box, e.g. 12 positions.
      4. Hot plate.
      5. Liquid scintillation vial.
      6. Liquid scintillation counter.
      7. Vacuum filtration system.
      8. Filters, of pore size 0,45 µm.
      9. Pipettes.
      10. Plastic tubes.
  1. Procedure
     1. Sample preparation

Weigh approximately 40 ml of the filtered sample, m, using an analytical balance (D.2.2.1) in a 50 ml disposable plastic centrifuge container (D.2.2.2). Record the sample volume, V, if it is desired to express the final concentration in a volume unit.

Add the tracer to the sample (D.2.1.1) and record the mass of solution added, m_ST using an analytical balance (D.2.2.1). Add an activity of yield tracer, which can be measured with sufficient precision to calculate the chemical yield.

• • 1. Sample purification by extraction chromatography

Place a 2 ml extraction chromatography resin cartridge with a quaternary amine (D.2.1.2) on top of a multi-holes vacuum box (D.2.2.3) using the appropriate connectors and reservoirs to pass the reagents through the resin.

Precondition the extraction resin with 5 ml of 0,1 mol·l⁻¹ (D.2.1.3).

Pass the sample through the resin at a flow rate of 1 ml·min⁻¹ to 2 ml·min⁻¹.

Rinse the resin twice with 25 ml (total 50 ml) of 0,01 mol·l⁻¹ HNO₃ (D.2.1.4).

If ²³⁴Th is present, rinse the resin another time with 25 ml of 0,5 mol·l⁻¹ HF in 0,02 mol·l⁻¹ HNO₃ (D.2.1.5).

If a high amount of Ru and/or Mo is present, rinse the resin another time twice with 20 ml (total 40 ml) of 2 mol·l⁻¹ HNO₃ (D.2.1.6).

Elute Tc from the resin into a glass beaker using 25 ml of 12 mol·l⁻¹ HNO₃ (D.2.1.7).

• • 1. Sample preparation for LSC measurement

Vaporize the sample solution on a hot plate (D.2.2.4) until 0,5 ml is left. It is suggested not to heat at a temperature above 80 °C to minimize the chemical recovery losses.

Transfer the 0,5 ml sample to a LSC vial (D.2.2.5). Rinse the container with up to 5 ml of water (D.2.1.8) and transfer this rinse solution to the LSC vial (D.2.2.5) and adjust to 5,5 ml if needed.

• • 1. Measurement
       1. Using Re tracer

Transfer 0,5 ml of the eluate and weigh the amount transferred, m₂, in a plastic tube (D.2.2.10).

Use the transffered solution to determine Re recovery, R_c.

Add up to 15 ml of LSC cocktail (D.2.1.9) in the LSC vial and mix the sample.

Let the sample stand in the instrument rack to reduce the luminescence by dark adaptation.

Measure the ⁹⁹Tc in the samples by LSC (D.2.2.6).

• • • 1. Using ^95mTc or ^99mTc tracer

Measure the tracer in the samples by gamma spectrometry and calculate the chemical recovery, R_c.

Let ^95mTc or ^99mTc decay completely.

Add up to 15 ml of LSC cocktail (D.2.1.9) in a 20 ml liquid scintillation vial and mix the sample.

Let the sample stand in the instrument rack to reduce the luminescence by dark adaptation.

Measure ⁹⁹Tc in the samples by LSC (D.2.2.6).

1. 
   (informative)
   
   Method 2 — extraction chromatography resin containg CMPO dissolved in TBP resin
   1. Principle

The sample is filtered, acidified, and oxidized as described in Clause 6. The tracer is added. Technetium-99 is purified from potential interferences by proceeding to a calcium phosphate co-precipitation followed by a solid phase extraction using an extraction chromatography resin containing octylphenyl-N,N-di-isobutyl carbamoylphosphine oxide (CMPO) dissolved in tributyl phosphate (TBP). Then Technetium-99 is measured by LSC. An approximate detection limit of 5 Bq·l⁻¹ is usually obtained using this method. This method is based on reference ^[24].

• 1. Reagents and apparatus
     1. Reagents

Use only reagents of recognized analytical grade.

• • • 1. Tracer solution, Re or ^95mTc or ^99mTc standard solution.
      2. Calcium chloride solution, c(CaCl₂) = 1 mol·l⁻¹.
      3. Phosphoric acid solution, c(H₃PO₄) = 14,8 mol·l⁻¹.
      4. Hydrogen peroxide solution, c(H₂O₂) = 8,82 mol·l⁻¹.
      5. Ammonium hydroxide solution, c(NH₄OH) = 14,5 mol·l⁻¹.
      6. Sulfuric acid solution, c(H₂SO₄) = 18 mol·l⁻¹.
      7. Chromatographic extraction resin containing octylphenyl-N,N-di-isobutyl carbamoylphosphine oxide (CMPO) dissolved in tributyl phosphate (TBP), 2 ml cartridge.
      8. Sulfuric acid solution, c(H₂SO₄) = 2 mol·l⁻¹.
      9. Ultrapure water, with a resistivity of more than 18,2 MΩ cm at 25 °C and total organic carbon less than 1 μg∙l⁻¹.
      10. Liquid scintillation cocktail, chosen according to the specifications of Annex B.
      11. ⁹⁹Tc standard solution.
    1. Apparatus

Usual laboratory equipment including the following:

• • • 1. Analytical balance, accuracy 0,1 mg.
      2. Disposable polypropylene centrifuge containers, minimum volume of 50 ml.
      3. Centrifuge.
      4. Multi-holes vacuum box, e.g. 12 positions.
      5. Hot plate.
      6. Liquid scintillation vial.
      7. Liquid scintillation counter.
      8. Vacuum filtration system.
      9. Filters, of pore size 0,45 µm.
      10. Pipettes.
  1. Procedure
     1. Sample preparation

Weigh approximately 40 ml of the filtered sample, m, using an analytical balance (E.2.2.1) in a 50 ml disposable plastic centrifuge container (E.2.2.2). Record the sample volume ,V, if it is desired to express the final concentration in a volume unit.

Add the tracer to the sample (E.2.1.1) and record the mass of solution added, m_ST using an analytical balance (E.2.2.1). Add an activity of yield tracer, which can be measured with sufficient precision to calculate the chemical yield.

Add 0,5 ml of 1 mol·l⁻¹ CaCl₂ (E.2.1.2) (except for sea water, as the amount of calcium is already sufficient), 0,2 ml of 14,8 mol·l⁻¹ H₃PO₄ (E.2.1.3), and 0,1 ml of 8,82 mol·l⁻¹ H₂O₂ solution (E.2.1.4). Mix the sample to homogenize and wait 5 min.

• • 1. Calcium phosphate precipitation

Add 1 ml of 14,5 mol·l⁻¹ NH₄OH (E.2.1.5) and mix the sample. Wait 5 min for the precipitate to be formed.

Centrifuge the sample (E.2.2.3).

Transfer the supernatant to a disposable 50 ml plastic container (E.2.2.2) and add 4,4 ml of 18 mol·l⁻¹ H₂SO₄ (E.2.1.6) to the supernatant. Mix the sample and wait 30 min to let the sample cool to room temperature.

CAUTION — The dissolution of H₂SO₄ in water is highly exothermic, which could make the plastic softer. It is important to be careful when closing the container cap.

• • 1. Sample purification by extraction chromatography

Place a 2 ml extraction resin cartridge (i.e. approximately 0,7 g of dry resin) (E.2.1.7) on top of a multi-holes vacuum box (E.2.2.4) using the appropriate connectors and reservoirs to pass the reagents through the resin.

Precondition the extraction resin with 10 ml of 2 mol·l⁻¹ H₂SO₄ (E.2.1.8).

Pass the sample through the resin at a flow rate of 3 ml·min⁻¹ to 4 ml·min⁻¹.

Rinse the resin with 30 ml of 2 mol·l⁻¹ H₂SO₄ (E.2.1.8).

Bring to boiling water in a clean glass beaker on a hot plate (E.2.2.5) (near boiling water).

Elute Tc and Re from the resin using approximately 14 ml of the near boiling water (E.2.1.9) in a 50 ml plastic container (E.2.2.2). The elution should be done as quickly as possible to maintain the high water temperature. The volume of water can be measured by a graduated reservoir on top of the resin such as a syringe. Let the solution cool to room temperature.

CAUTION — Wear appropriate protective gloves when manipulating the hot water glass beaker to avoid burns.

• • 1. Measurement
       1. Using Re tracer

Transfer 5 ml of the eluate in an in a 20 ml LSC vial (E.2.2.6) and weigh the amount transferred, m₁.

Determine Re recovery, R_c, using the remaining solution eluate.

Add up to 15 ml of LSC cocktail (E.2.1.10) in the LSC vial and mix the sample.

Let the sample stand in the instrument rack to reduce the luminescence by dark adaptation.

Measure the ⁹⁹Tc in the samples by LSC (E.2.2.7).

• • • 1. Using ^95mTc or ^99mTc tracer

Measure the tracer in the samples by gamma spectrometry and calculate the recovery, R_c.

Let ^95mTc or ^99mTc decay completely.

Transfer 5 ml of the eluate in a 20 ml LSC vial (E.2.2.6) and weigh the amount transferred, m₁.

Add up to 15 ml of LSC cocktail (E.2.1.10) in the LSC vial and mix the sample.

Let the sample stand in the instrument rack to reduce the luminescence by dark adaptation.

Measure the ⁹⁹Tc in the samples by LSC (E.2.2.7).

1. 
   (informative)
   
   Method 3 — Anion exchange resin
   1. Principle

The sample is filtered, acidified, and oxidized as described in Clause 6. The tracer is added. Technetium-99 is purified from potential interferences by passing the solution through an anion exchange resin, which contains a quaternary amine that selectively extracts Tc. Then ⁹⁹Tc is measured by LSC. An approximate detection limit of 20 Bq·l⁻¹ is usually obtained using this method. This method is based on Reference ^[25].

• 1. Reagents and apparatus
     1. Reagents

Use only reagents of recognized analytical grade.

• • • 1. Tracer solution,^95mTc or ^99mTc standard solution.
      2. Strong basic anion exchange resin, 0,8 ml.
      3. Hydrochloric acid solution, c(HCl) = 0,5 mol·l⁻¹.
      4. Ultrapure water, with a resistivity of more than 18,2 MΩ cm at 25 °C and total organic carbon less than 1 μg∙l⁻¹.
      5. Nitric acid solution, c(HNO₃) = 0,5 mol·l⁻¹.
      6. Nitric acid solution, c(HNO₃) = 10 mol·l⁻¹.
      7. Liquid scintillation cocktail, chosen according to the specifications of Annex B.
      8. ⁹⁹Tc standard solution.
    1. Apparatus

Usual laboratory equipment including the following:

• • • 1. Analytical balance, accuracy 0,1 mg.
      2. Disposable polypropylene centrifuge container, minimum volume of 50 ml.
      3. Multi-holes vacuum box, e.g. 12 positions.
      4. Hot plate.
      5. Liquid scintillation vial.
      6. Liquid scintillation counter.
      7. Filters, of pore size 0,45 µm.
      8. Vacuum filtration system.
      9. Pipettes.
      10. Plastic tubes.
  1. Procedure
     1. Sample preparation

Weigh approximately 14 ml of the filtered sample, m, using an analytical balance (F.2.2.1) in a 50 ml disposable plastic centrifuge container (F.2.2.2). Record the sample volume, V, if it is desired to express the final concentration in a volume unit. Add the tracer to the sample (F.2.1.1) and record the mass of solution added, m_ST, using an analytical balance (F.2.2.1). Add an activity of yield tracer, which can be measured with sufficient precision to calculate the chemical yield.

• • 1. Sample purification by anion exchange chromatography

Prepare an anion exchange resin column (F.2.1.2) of 4 cm with an internal diameter of 5 mm (~0,8 ml resin volume) (longer columns can be used, but the quantity of eluent shall be adjusted).

Place the resin on top of a multi-holes vacuum box (F.2.2.3) using the appropriate connectors and reservoirs to pass the reagents through the resin.

Precondition the anion exchange resin with 2 ml 0,5 mol·l⁻¹ HCl (F.2.1.3), followed by 2 ml of ultrapure water (F.2.1.4).

Pass the sample through the resin at a flow rate of 1 ml·min⁻¹ to 2 ml·min⁻¹.

Rinse the resin with 2 ml of 0,5 mol·l⁻¹ HNO₃ (F.2.1.5).

Elute Tc from the resin in a glass beaker using 10 ml of 10 mol·l⁻¹ HNO₃ (F.2.1.6).

• • 1. Sample preparation for LSC measurement

Vaporize the sample solution on a hot plate (F.2.2.4) until 1 ml is left. It is suggested not to heat at a temperature above 80 °C to minimize the chemical recovery losses.

Complete to 12 ml with water (F.2.1.4).

• • 1. Measurement
       1. Using Re tracer

Transfer 2 ml of the eluate and weigh the amount transferred, m₂, in a plastic tube (F.2.2.10).

Use the transffered solution to determine Re recovery, R_c.

Add up to 15 ml of LSC cocktail (F.2.1.7) in the LSC vial and mix the sample.

Let the sample stand in the instrument rack to reduce the luminescence by dark adaptation.

Measure the ⁹⁹Tc in the samples by LSC (F.2.2.6).

• • • 1. Using ^95mTc or ^99mTc tracer

Measure the tracer in the samples by gamma spectrometry and calculate the recovery, R_c.

Let ^95mTc or ^99mTc decay completely.

Transfer 5 ml of the eluate in a 20 ml LSC vial (F.2.2.5) and weigh the amount transferred, m₁.

Add up to 15 ml of LSC cocktail (F.2.1.7) in LSC vial and mix the sample.

Let the sample stand in the instrument rack to reduce the luminescence by dark adaptation.

Measure the ⁹⁹Tc in the samples by LSC (F.2.2.6).

Bibliography

[1] IAEA, Environmental and Source Monitoring for Purposes of Radiation Protection. Safety Guide No. RS-G-1.8. International Atomic Energy Agency, Vienna, 2005

[2] ICRP, (2007) Annals of the ICRP - Publication 103: The 2007 Recommendations of the International Commission on Radiological Protection Editor J. Valentin Published for The International Commission on Radiological Protection, 2007

[3] IAEA GSG-2, Criteria for use in preparedness and response for a nuclear or radiological emergency (Jointly sponsored by FAO, IAEA, ILO, PAHO, WHO). International Atomic Energy Agency, Vienna, 2011

[4] WHO, Guidelines for Drinking-water Quality. Fourth Edition incorporating the first and the second addenda. World Health Organization, Geneva, 2022.

[5] ISO/IEC Guide 98-3:2008, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in measurement (GUM:1995)

[6] ISO 5667-20:2008, Water quality — Sampling — Part 20: Guidance on the use of sampling data for decision making — Compliance with thresholds and classification systems

[7] ICRP Publication 72 (1995) Age-dependent doses to members of the public from intake of radionuclides – Part 5 Compilation of ingestion and inhalation coefficients

[8] ICRP Publication 119 (2012) Compendium of dose coefficients based on ICRP publication 60

[9] Shi K., Hou X., Roos P., Wu W., Determination of technetium-99 in environmental samples: A review. Anal. Chim. Acta. 2012, 709 pp. 1–20

[10] Laboratoire National Henri Becquerel. Recommended Data. Tables of evaluated data and comments from Decay Data Evaluation Project. Available (viewed 2025-05-01) at: http://www.lnhb.fr/home/nuclear-data/nuclear-data-table/

[11] Smith W.T., Line L.E., Bell W.A., The vapor pressure of rhenium heptoxide and perrhenic acid. J. Am. Chem. Soc. 1952, 74 pp. 4964–4966

[12] Smith W.T., Cobble J.W., Boyd G.E., Thermodynamic Properties of Technetium and Rhenium Compounds. I. Vapor Pressures of Technetium Heptoxide, Pertechnic Acid and Aqueous Solutions of Pertechnic Acid. J. Am. Chem. Soc. 1953, 75 pp. 5773–5776

[13] ISO 11885, Water quality — Determination of selected elements by inductively coupled plasma optical emission spectrometry (ICP-OES)

[14] ISO 15586, Water quality — Determination of trace elements using atomic absorption spectrometry with graphite furnace

[15] Likussar W., Sparks G.E., Boltz D.F., The ultraviolet spectrophotometric determination of rhenium by the pyrrolidinedithiocarbamate method. Anal. Chim. Acta. 1970, 52 (2) pp. 349–355

[16] Thompson R.J., Gore R.H., Trusell F., Methyl-2-pyridyl ketoxime as a colorimetric reagent for rhenium. Anal. Chim. Acta. 1964, 31 pp. 590–594

[17] ISO 5667-4, Water quality — Sampling — Part 4: Guidance on sampling from lakes, natural and man-made

[18] ISO 5667-5:2006, Water quality — Sampling — Part 5: Guidance on sampling of drinking water from treatment works and piped distribution systems

[19] EN ISO 5667-6:2016, Water quality - Sampling - Part 6: Guidance on sampling of rivers and streams (ISO 5667-6:2014)

[20] ISO 5667-7:1993, Water quality — Sampling — Part 7: Guidance on sampling of water and steam in boiler plants

[21] ISO 5667-11:2009, Water quality — Sampling — Part 11: Guidance on sampling of groundwaters

[22] ISO 5667-14:2014, Water quality — Sampling — Part 14: Guidance on quality assurance and quality control of environmental water sampling and handling

[23] Technetium-99 in Water, Eichrom procedure TCW01, revision 1.7, Eichrom technologies, May 1, 2014

[24] Guérin, N., Gagné, A., Kramer-Tremblay, S. A rapid method for the routine monitoring of 99Tc by liquid scintillation counting. J. Radioanal. Nucl. Chem., 2017, 314(3) , 2009-2017

[25] Eroglu, A.E., McLeod, C.W., Leonard, K.S., McCubbin, D. Determination of technetium in sea-water using ion exchange and inductively coupled plasma mass spectrometry with ultrasonic nebulisation, J. Anal. At. Spectrom. 1998, 13 pp. 875-878