ISO/DIS 20899:2026(en)

ISO TC 147/SC 3

Secretariat: AFNOR

Date: 2025-12-24

Water quality — Plutonium and neptunium — Test method using ICP-MS

© ISO 2026

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Contents

Foreword iv

Introduction v

1 Scope 1

2 Normative references 2

3 Terms and definitions 2

4 Symbols 2

5 Principle 3

6 Sampling and sample storage 5

7 Chemical reagents and apparatus 5

7.1 Chemical reagents 5

7.2 Apparatus 6

8 Sample preparation 6

8.1 General 6

8.2 Storage 6

8.3 Chemical separation 6

9 Measurement procedure 7

9.1 Instrument verification 7

9.2 Quantification with internal calibration and isotopic dilution 7

10 Expression of results 7

10.1 General 7

10.2 Mass bias evaluation 8

10.3 Internal calibration and isotopic dilution 8

11 Uncertainties for isotopic dilution 8

12 Instrumental limit of detection 9

13 Limit of quantification 9

14 Activity concentration determination 9

15 Test report 9

Annex A (informative) Chemical separation of plutonium and neptunium by specific resin 11

A.1 Principle 11

A.2 Technical resources 11

A.2.1 Chemical reagents 11

A.2.2 Equipment 11

A.3 Procedure 11

A.3.1 General 11

A.3.2 Chemical separation 11

A.3.3 Measurement 12

Bibliography 13

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 some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).

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 20899:2018), which has been technically revised.

The main changes are as follows:

— The scope was clarified

— Addition of recommendations regarding potential interferences

— The common SC 3 template for Introduction was implemented

— The common SC 3 template for Test report was implemented

— The bibliographical references were updated

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, ⁶⁰Co, ⁶³Ni, ⁹⁰Sr, ⁹⁹Tc, ¹³⁷Cs transuranic elements (e.g., Np, Pu, Am, and 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 in drinking water are respectively 1 Bq·l−1^[4] for ²³⁹Pu, ²⁴⁰Pu, ²³⁷Np and 10 Bq·l−1^[4] for ²⁴¹Pu, 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 to these limits, as specified by ISO/IEC Guide 98-3 and ISO 5667-20^[5],

NOTE 1 If the WHO guidance level 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 [6] and [7].

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 for 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 to support laboratories, which need to determine ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu and ²³⁷Np in water samples. The method described in this document can be used for various types of waters (see Clause 1). Minor modifications such as sample volume and counting time can be made if needed to ensure that the decision threshold, detection limit, 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 — Plutonium and neptunium — Test method using ICP-MS

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.

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 the ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu and ²³⁷Np by inductively coupled plasma mass spectrometry (ICP-MS). The mass concentrations obtained can be converted into activity concentrations.

Due to its relatively short half-life and ²³⁸U isobaric interference, ²³⁸Pu can hardly be measured by this method. To quantify ²³⁸Pu isotope by mass spectrometry, other techniques can be used (ICP-MS with collision-reaction cell, ICP-MS/MS with collision-reaction cell or chemical separation). Alpha spectrometry measurement, as described in ISO 13167,^[8] is currently used^[9].

The method is applicable to test samples of supply/drinking water, rainwater, surface and ground water, marine water, as well as cooling water, industrial water, domestic, and industrial wastewater after proper sampling and handling, and test sample preparation.

A chemical separation of Np and Pu, with quantitative removal of all other elements (including uranium, americium, etc.) is mandatory, given all the potential interferences that may bias the measurement or lead to false positives. Chemical separations can eliminate most of the ²³⁸U. However, use of reagents, glassware, and atmosphere for the chemical separation, will also add ²³⁸U to the samples and prevent measurement of ²³⁸Pu.

The limit of detection depends on the sample volume, the instrument used, the background count rate, the detection efficiency, the counting time, and the chemical yield. The detection limit of the method described in this document, using currently available ICP-MS apparatus, is approximately 1 mBq·l^-1 for ²³⁹Pu, ²⁴⁰Pu, ²³⁷Np and 1 Bq·l^-1 for ²⁴¹Pu, which is lower or of the same order of magnitude than the WHO criteria for safe consumption of drinking water (1 mBq·l^-1 for ²³⁹Pu, ²⁴⁰Pu, ²³⁷Np and 10 Bq·l^-1 for ²⁴¹Pu^[4]).This method covers the measurement of those radionuclides in water at activity concentrations between approximately^[10][11]:

— 1 mBq·l⁻¹ to 5 Bq·l⁻¹ for ²³⁹Pu, ²⁴⁰Pu and ²³⁷Np;

— 1 Bq·l⁻¹ to 5 Bq·l⁻¹ for ²⁴¹Pu.

Samples with higher activity concentrations than 5 Bq·l⁻¹ can be measured if a dilution is performed.

The higher is the concentration factor, the lower are the LD and LQ expressed in Bq/L of water. A preconcentration is especially useful for the quantification of 241Pu that is usually the less abundant isotope of plutonium.

The method described in this document is applicable in the event of an emergency situation.

Filtration of the test sample is necessary. The analysis of ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu and ²³⁷Np 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 performed separately on each phase or the total phase.

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/IEC Guide 98‑3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in measurement (GUM:1995)

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 17294‑1:2024, Water quality — Application of inductively coupled plasma mass spectrometry (ICP-MS) — Part 1: General requirements

ISO 17294‑2:2023, Water quality — Application of inductively coupled plasma mass spectrometry (ICP-MS) — Part 2: Determination of selected elements including uranium isotopes

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

For the purposes of this document, the terms and definitions given in ISO/IEC Guide 98-3, ISO/IEC Guide 99 and ISO 80000-10 apply.

The principle of measurement of analysis using ICP-MS is described in ISO 17294-1 and ISO 17294-2.

ICP-MS has been successfully used to measure the mass concentrations of plutonium isotopes (²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu) and ²³⁷Np in water samples.

The results can be converted in activity concentrations using the specific activity as a conversion factor given in Table 1 [^[9],^[12],^[13],^[14]].

The typical measurement time is several minutes per sample, including sample uptake, counting time and washout before the next sample.

Table 1 — Plutonium and neptunium isotopes half-lives and specific activities^[10][11]

The Pu and Np isotopes in the water sample have to be measured after filtration (at 0,45 μm pore size) and acid preservation if suspended particles are present for the determination of dissolved radionuclides and a specific chemical separation shall be performed to limit potential interferences due to uranium isotopes^[12] to ²⁴¹Am (with ²⁴¹Pu) and many potential polyatomic interferences.^[15] An example of chemical separation is given in Annex A.

As described in the ISO 17294 series, a tracer is needed to calculate the chemical recovery and to perform an isotopic dilution. A known amount of pure certified tracer standard solution is added to the sample test portion and the calculation of isotope concentration is based on the isotopic ratios.

Activity certified standard solution can be converted into mass certified standard solution thanks to specific activities in Table 1. External calibration requires more samples preparations and measurements, and more complicated calculations. Therefore, if a certified isotope dilution tracer (²⁴²Pu or ²⁴⁴Pu for plutonium quantification) is available, quantification by isotope dilution is highly preferable.

For the determination of plutonium isotopes in water, ²⁴²Pu is commonly used but ²⁴⁴Pu can also be chosen.

The chemical yield obtained for plutonium can be applied to neptunium.^[16] This may lead to a potential bias that should be quantified. Other methods should be used such as external calibration, addition of the short lived ²³⁹Np as tracer, standard additions of ²³⁷Np in several test portions of the sample, etc.

It is also important to evaluate the mass bias and to correct it (see 10.2).

Examples of limits of quantification that can be obtained with a quadrupole ICP-MS are given in Table 2.

Table 2 — Examples of limits of quantification^[13][14]

LD depend on the sensitivity and background of the instrument and on the concentration factor of the chemical separation. Given a concentration factor of 1 000, LD in the µBq/L range for ²³⁹Pu and ²⁴⁰Pu and in the mBq/L range for ²⁴¹Pu may be achieved. For example, if 1L of water is analyzed, the limit of detection of ²³⁹Pu is 1mBq/sample. If the eluent is 15ml, even if the recovery rate is low as 50 %, the LQ of ICP-MS can reach 33 mBq/l.

It is important to ensure that all potential interferences have been removed prior to measurement. The most significant interference affecting radionuclide measurement by ICP-MS is isobaric, specific polyatomic and tailing interferences, see Table 3.

Table 3 — Interference of plutonium and neptunium affecting ICP-MS ^[9],[17]

Through chemical separation, high uranium decontamination factor can be achieved but remaining uranium concentration is likely to be still above the typical ²³⁸Pu concentration expected in water. In addition, this ²³⁸Pu concentration is expected to be lower than the L_Q reported. For this reason, current instrumentation is not suited for ²³⁸Pu measurements, in normal conditions. However, assuming that a collision-reaction cell could be installed onto a more sensitive instrument, such a newer instrument could be more suited for the separation of isobaric interferences.

For example, the potential presence of ²⁴¹Am in analysed samples and that its presence might create a high bias for ²⁴¹Pu or potential presence on ²⁴²Pu in the analysed samples, e.g. separate from added ²⁴²Pu tracer.^[18] The most important interference in ²³⁷Np determination is from ²³⁸U, if the sample has high concentrations of uranium, as is often the case with environmental samples. However, the ²³⁸U peak will tail partly or totally over the ²³⁷Np peak in a mass spectrum, if the Np/U separation has not been efficient.

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 is given in References [19] to [26] It is important that the laboratory receives a sample that is truly representative and has neither been damaged nor modified during transportation or storage.

Perform the storage and pre-treatment steps (filtration and acidification) described in Clause 8 when sampling or immediately afterwards.

Minimising contamination and losses is of primary concern. Impurities in the reagents and dust on the laboratory equipment, in contact with the samples can be potential sources of stable element contamination that increases the background at m / z = 237 to 244. The sample containers can lead to either a positive or a negative bias in the determination of trace elements by superficial desorption or adsorption^[27] and^[28].

Use only reagents of recognized analytical grade.

7.1.1 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.

Unless otherwise stated, water refers to ultrapure water.

7.1.2 Blank sample, is taken through the entire procedure, including chemical separation.

Diluted acid solution is used to determine the background spectra for the various masses.

7.1.3 Certified standard solutions of isotopes, with known isotopic composition, is recommended to evaluate the mass bias.

Use of a reference solution with known actinide isotopic composition is recommended for standard bracketing (measured at least twice, before and after the sample, in several repetitions).

7.1.4 Tracer solution (for example ²⁴²Pu).

This is prepared by successive dilutions of the certified standard solution, the last dilution being in 1 % to 2 % nitric acid (volume). Concentration is adjusted in link with the method validation. The water samples are spiked with a known amount of this solution at the beginning of the procedure.

7.1.5 Quality control solution, solution of plutonium solution with certified isotopic composition, different than the one used for isotopic dilution should be used if possible.

7.1.6 Argon gas, at least 99,995 % pure.

7.1.7 Diluted nitric acid, 2 % volume, for example.

The usual laboratory apparatus and, in particular, the following.

7.2.1 Analytical balance, for example, capable of achieving ±0,1 mg precision.

7.2.2 Argon supply, equipped with low pressure control.

7.2.3 ICP-MS apparatus - quadrupole, (with or without collision or reaction cell capability), tandem, sector field, single or multi-collector. Follow the manufacturers instruction for laboratory setup and instrument operation.

7.2.4 Auto-sampler device, if available.

7.2.5 Membrane filter, 0,45 μm.

The sample is filtered to remove suspended matter using a 0,45 μm filter (e.g. 0,45 μm PTFE membrane) (7.2.5).

Acidify with nitric acid (7.1.7) to ensure that the pH of the sample is less than 2.

For a representative analysis of drinking water, filtration is not required.

Follow ISO 5667-3. Perform the analysis as soon as possible.

A chemical separation from potential interferences is performed, for example, as explained in Annex A. Other procedures for chemical separation can also be used (such as those described in References [9] [12], [13], [14], [29], [30], [31] and [32]).

Measure the volume of the test portion, V or weigh the mass of the test portion of the sample.

A pre-concentration step can be added (see Reference [8]), for example, using a co-precipitation method with Fe³⁺ solution. This precipitation consists of the addition of Fe³⁺ carrier solution and the precipitation of iron with the addition of ammonia to pH 10. The supernatant is discarded and the iron hydroxide precipitate, which contains the plutonium and the other actinides, is dissolved with concentrated nitric acid.

Follow the instructions provided by the instrument manufacturer and the steps described in ISO 17294-1:2024, Clauses 7 and 9 in particular and ISO 17294-2:2023, Clauses 8 to 11 in particular.

The instrument sensitivity, limit of detection, measurement precision, and measurement bias should be determined for every analysis performed on the instrument.

Although the chemical separation is done to avoid common interferences (mainly with ²³⁸U and UH⁺ effect at 239 m/z area), the potential interferences for the masses of interest should be reported in a separate table. It is recommended to measure the count rate at m/z = 238 to assess if the amount of ²³⁸U is sufficiently low so as not to interfere. The collision-reaction cell settings or mathematical corrections for common interferences shall be used.

Before any sample measurement, measure the quality control solution (7.1.5). Ensure that the measured value of the concentration does not deviate from the expected value (within measurement limits). If the deviation exceeds the established measurement limits (optimum sensitivity, optimum stability), follow the recommendations of the instrument manufacturer and perform the optimization of parameters again.

The blank solution (7.1.2) is measured as a sample. The obtained value shall be subtracted from the measured sample values.

A rinsing sequence shall be performed. The sample introduction system is rinsed between analysis of each sample using a diluted solution of HNO₃ (7.1.7). Then, a blank solution is processed to verify that all remaining Np and Pu isotopes are removed from the system by returning to the baseline.

The “peak tailing effect” (also referred to as “abundance sensitivity”) can significantly increase the background in the masses adjacent to a relatively intense peak, like the one of ²³⁸U on mass 239 m/z. The amplitude of this “peak-tailing effect” depends on the instrument; it is usually stronger with high resolution ICP-MS than with quadrupole-based ICP-MS.

The plutonium isotopic concentrations are calculated based on the ²⁴²Pu (or ²⁴⁴Pu) standard solution isotopic composition and concentration introduced in the samples.

Isotopic ratios in the standard tracer solution shall be different than the one in the sample test portion.

For maximum precision and accuracy on quantification, the mass of tracer added should be high enough to limit the associated measurement uncertainty.

Perform measurement on samples.

If any, impurities of other plutonium isotopes in the standard solution that will be still present after the chemical separation shall be quantified with precision and corrections shall be made as well as for mass bias.

The result is expressed as an estimate of the “true” value, to which an uncertainty is associated, itself a combination of elementary uncertainties.

If dilutions were carried out, apply the appropriate factor to the values of the sample.

The results, with their associated uncertainties, are expressed in mass concentration. The coverage factor is specified in the presentation of the results.

The measurement bias is a correction factor that corrects for all the measurement deviations between the tracer and the analyte. It includes correction for the mass bias and the variation of signal intensity between the tracer and the analyte. When a stable tracer or internal standards is used, it also corrects for the fact that only one isotope of the element is used for the measurement.

This fractionation coefficient deviation can be defined as a function of the different masses studied. The true ratio (R) of isotopes A and B can be expressed from the ratio measured, r, by different relations called linear law, power law, kinetic law, equilibrium law or generalized power law^[33].

The bias per unit mass (α) is determined measuring a certified solution (7.1.3) (or a reference solution when using standard bracketing).

The linear law is commonly used, as shown by Formula (1):

(1)

In the following formulae, the raw counts or isotopic ratio are corrected of the mass bias, if needed.

The associated uncertainty shall be determined.

The use of uranium isotopic standard solution for mass bias determination is possible. It is easily available and easier to handle than plutonium isotopic standard solutions.

²⁴²Pu is generally used as isotope dilution tracer (but ²⁴⁴Pu can also be used): a known quantity of ²⁴²Pu, generally determined by weighing, is added to each sample and is thus used to calculate the concentration of other plutonium isotopes present in the sample:

With an internal standard, the mass concentration (ρ) of the plutonium isotopes or ²³⁷Np, expressed in μg·l⁻¹, is given in Formula (2):

(2)

with Formula (3):

(3)

where

j is the mass number of the tracer (242 or 244);

i is the mass number of the analyte (237, 239, 240 or 241).

It is possible to use counts instead of count rates in all formulae only if the counting time is the same for all isotopes.

With ²⁴²Pu or ²⁴⁴Pu as a tracer, the uncertainty^[30] associated with the mass concentration of the plutonium isotopes or ²³⁷Np is expressed by Formula (4):

(4)

with Formula (5):

(5)

where

j is the mass number of the tracer (242 or 244);

i is the mass number of the analyte (237, 239, 240 or 241).

The instrumental limit of detection, L_DI, for a given mass, is obtained from an extension of the standard deviation associated with the measurements obtained for 3 test portions of the blank, as shown in Formula (6):

(6)

The limit of detection, L_D, is expressed in μg·l⁻¹ using L_DI (equivalent to three times the background counts deviation) in the case of isotope dilution (with ²⁴²Pu for example) using Formula (7):

(7)

The instrumental limit of quantification, L_Qins, for a given mass, can be evaluated as 10 times the standard deviation associated with the measurements obtained for 10 test portions of the blank, as shown by Formula (8):

(8)

The limit of quantification (L_Q) can be expressed in μg·l⁻¹ in the case of isotope dilution (with ²⁴²Pu for example) by Formula (9):

(9)

The mass activity can be calculated using the specific activity C_s given in Table 1 following Formula (10):

(10)

The activity concentration uncertainty is expressed by Formula (11):

(11)

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

a) a reference to this document, i.e. ISO/DIS 20899:2025;

b) identification of the sample;

c) units in which the results are expressed;

d) the test result can be given according to method 1 or method 2. The method used shall be clearly stated in the report.

Method 1)

— if the result is less than the limit of detection, the result of the measurement is expressed as ≤ L_D,

— if the result is between the limit of detection and the limit of quantification, the result of the measurement is expressed as ≤ L_Q,

— if the result is greater than the limit of quantification, the result of the measurement is expressed as (ρ ± k·u(ρ) or ρ ± U(ρ)) or as (c ± k·u(c) or c ± U(c)) with the associated k value

If the limit of detection exceeds the guideline value, it shall be documented that the method is not suitable for the measurement purpose.

Method 2)

— if the result is less than the limit of quantification, the result of the measurement is expressed as ≤ L_Q,

— if the result is greater than the limit of quantification, the result of the measurement is expressed as (ρ ± k·u(ρ) or ρ ± U) or as (c ± k·u(c) or c ± U) with the associated k value

If the limit of quantification exceeds the guideline value, it shall be documented that the method is not suitable for the measurement purpose

e) the date used to calculate the sample mass activity

f) the date of issue of the report.

Complementary information can be provided such as:

g) 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

h) the limit of application;

i) the limit of detection and limit of quantification;

j) mention of any relevant deviation from this document 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, C, with 453 the detection limit, LD, in order to decide whether the physical effect is recognized or not. Such stipulation is not in 454 accordance with the ISO 11929 series. The consequence is that it is decided too frequently that the physical effect is 455 absent while in fact it is not.

1. 
   (informative)
   
   Chemical separation of plutonium and neptunium by specific resin
   1. Principle

This technique is based on the selective chromatographic extraction of plutonium and neptunium, especially from uranium isotopes, using a resin coated with a specific extractant, an aliphatic quaternary amine. The chemical separation is fast and well suited for monitoring plutonium and neptunium activity in waters by ICP-MS measurements.

• 1. Technical resources
     1. Chemical reagents

A.2.1.1 Nitric acid, concentrated, c(HNO₃) = 69 % minimum.

A.2.2.2 Sodium nitrite (NaNO₂).

A.2.2.3 Different Nitric acid c(HNO₃) solutions, 8 mol·l⁻¹, 3 mol·l⁻¹, 0,01 mol·l⁻¹.

A.2.2.4 Hydrochloric acid (HCl) solution, 9 mol·l⁻¹.

• • 1. Equipment

Standard laboratory equipment and, in particular, the following.

A.2.2.1 Analytical balance, to an accuracy of 0,1 mg.

A.2.2.2 Evaporator or hot plate.

A.2.2.3 Specific extractant coated resin columns.

• 1. Procedure
     1. General

This procedure is carried out with two main steps: extraction and elution of plutonium and neptunium. In all steps, if not specified, the flow rate should be of approximately 1 ml·min^-1.

NOTE In some cases, the flow through resin columns is very poor because of sample impurities. Working with vacuum is therefore very helpful to support the flow.

A pre-concentration step can be added,^[8] for example, using a co-precipitation method with Fe³⁺ solution. This precipitation consists of the addition of FeCl₃ and the precipitation of iron with the addition of ammonia to pH 9. The supernatant is discarded and the iron hydroxide precipitate, which contains the plutonium and the other actinides, is dissolved with concentrated nitric acid.

• • 1. Chemical separation

The operations are carried out as follows:

a) measure the sample test portion volume;

b) weigh and add the tracer (²⁴²Pu, for example);

c) dilute the sample with the required volume of concentrated nitric acid (A.2.2.1) to obtain a nitric acid concentration of 3 mol·l⁻¹ (A.2.1.3) in the test portion, or evaporate it to dryness and add 3 mol·l⁻¹ of nitric acid;

d) adjust the oxidation state of Pu and Np to (IV) and (V), respectively by adding an excess of NaNO2(A.2.2.2);

e) set up the resin bed (for example, 2 ml resin bed); the following steps are given for this resin bed volume);

f) condition the resin by passing 20 ml of 3 mol·l⁻¹ HNO₃ (A.2.1.3);

g) pour the sample test portion on top of the resin;

h) wash the resin with 5 ml of 3 mol·l⁻¹ HNO₃ (A.2.1.3), pour the rinsed solution on top of the resin;

i) wash the resin with 20 ml of 8 mol·l⁻¹ HNO3 (A.2.1.3) to eliminate remaining uranium isotopes;

j) wash the resin with 20 ml of 9 mol·l⁻¹ HCl(A.2.1.4) to elute thorium isotopes; discard the washings;

k) place a clean receiving container under the resin column and elute neptunium and plutonium isotopes with 15 ml of 0,01 mol·l⁻¹ HNO3(A.2.1.3);

NOTE Plutonium and neptunium can be eluted using other reagents^{[23][24][25][26]}.

l) fill up the eluate to a defined volume or evaluate the total elution volume.

• • 1. Measurement

a) Perform ICP-MS measurement.

b) Evaluate mass concentrations of isotopes.

c) Calculate the corresponding activity concentrations.

Bibliography

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[2] ICRP. Annals of the ICRP – Publication 103: The 2007 Recommendations of the International Commission on Radiological Protection. Valentin J. (ed.) 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. World Health Organization, Geneva, 2022

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

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

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

[8] ISO 13167:2015, Water quality — Plutonium, americium, curium and neptunium — Test method using alpha spectrometry

[9] Lariviere D. et al. Radionuclide determination in environmental samples by inductively coupled plasma mass spectrometry. Spectrochimica Acta Part B Atomic Spectroscopy, 2006, 61, pp. 877–904

[10] Bureau International des Poids et Mesures (BIPM). Monographie BIPM-5. https://www.bipm.org/fr/publications/monographie-ri-5.html. Nuclear database: Decay data evaluation project. http://www.nucleide.org/DDEP_WG/DDEPdata.htm; http://www.nucleide.org/DDEP_WG/DDEPdata.htm

[11] NIST. https://www.nist.gov/pml/data/comp.cfm

[12] Xu Y. et al. Determination of plutonium isotopes in environmental samples using radiochemical separation combined with radiometric and mass spectrometric measurements. Talanta. 2014, 119, pp. 590–595

[13] Hou X., et al. Critical comparison of radiometric and mass spectrometric methods for the determination of radionuclides in environmental, biological and nuclear waste samples. Analytica Chimica Acta, 2008, 608, pp. 105–139

[14] Maxwell S. Rapid determination of ²³⁷Np and Pu isotopes in water by inductively-coupled plasma mass spectrometry and alpha spectrometry. Journal of Radioanalytical and Nuclear Chemistry, 2011, 287, pp. 223–230, DOI 10.1007/s 10967-010-0825-9

[15] Pointurier F., Hémet P., A. Hubert, Journal of Analytical Atomic Spectrometry, 23 (2008) 94–102

[16] Jixin Qiao and al. Reliable determination of 237Np in environmental solid samples using 242Pu as a potential tracer. TALANTA. 2011, 84, pp. 494–500

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

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

[21] ISO 5667‑6, Water quality — Sampling — Part 6: Guidance on sampling of rivers and streams

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

[23] ISO 5667‑8, Water quality — Sampling — Part 8: Guidance on the sampling of wet deposition

[24] ISO 5667‑9, Water quality — Sampling — Part 9: Guidance on sampling from marine waters

[25] ISO 5667‑11, Water quality — Sampling — Part 11: Guidance on sampling of groundwaters

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

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