Soil, treated biowaste, sludge and waste - Digestion of aqua regia soluble fractions of elements (ISO 54321:2020)

This European Standard specifies two methods for digestion of soil, treated biowaste, sludge and waste by the use of aqua regia as digestion solution.
This European Standard is applicable for the following elements:
aluminium (Al), antimony (Sb), arsenic (As), barium (Ba), beryllium (Be), bismuth (Bi), boron (B), cadmium (Cd), calcium (Ca), cerium (Ce), cesium (Cs), chromium (Cr), cobalt (Co), copper (Cu), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), gallium (Ga), germanium (Ge), gold (Au), hafnium (Hf), holmium (Ho), indium (In), iridium (Ir), iron (Fe), lanthanum (La), lead (Pb), lithium (Li), lutetium (Lu), magnesium (Mg), manganese (Mn), mercury (Hg), molybdenum (Mo), neodymium (Nd), nickel (Ni), palladium (Pd), phosphorus (P), platinum (Pt), potassium (K), praseodymium (Pr), rubidium (Rb), rhenium (Re), rhodium (Rh), ruthenium (Ru), samarium (Sm), scandium (Sc), selenium (Se), silicon (Si), silver (Ag), sodium (Na), strontium (Sr), sulfur (S), tellurium (Te), terbium (Tb), thallium (Tl), thorium (Th), thulium (Tm), tin (Sn), titanium (Ti), tungsten (W), uranium (U), vanadium (V), ytterbium (Yb), yttrium (Y), zinc (Zn), and zirconium (Zr).
This European Standard may also be applicable for the digestion of other elements.
Digestion with aqua regia will not necessarily accomplish total decomposition of the sample. The extracted analyte concentrations may not necessarily reflect the total content in the sample.

Boden, behandelter Bioabfall, Schlamm und Abfall - Aufschluss von mit Königswasser löslichen Anteilen von Elementen (ISO 54321:2020)

Dieses Dokument legt zwei Verfahren zum Aufschluss von Boden, behandeltem Bioabfall, Schlamm und Abfall mit einem Königswasser-Aufschluss fest.
Der Aufschluss mit Königswasser führt nicht zwangsläufig zur vollständigen Zersetzung der Probe. Die Konzentrationen der extrahierten Analyte spiegeln nicht unbedingt den Gesamtgehalt in der Probe wider, aber stellen die in Königswasser unter den Bedingungen dieses Prüfverfahrens löslichen Metalle dar. Es herrscht allgemein Einigkeit darüber, dass für umweltbezogene Analysen die Ergebnisse für den vorgesehenen Zweck des Umweltschutzes geeignet sind.
Dieses Dokument ist anzuwenden für die nachstehend aufgeführten Elemente:
Aluminium (Al), Antimon (Sb), Arsen (As), Barium (Ba), Beryllium (Be), Boron (B), Cadmium (Cd), Calcium (Ca), Chrom (Cr), Cobalt (Co), Kupfer (Cu), Eisen (Fe), Blei (Pb), Magnesium (Mg), Mangan (Mn), Quecksilber (Hg), Molybdän (Mo), Nickel (Ni), Phosphor (P), Kalium (K), Selen (Se), Silber (Ag), Natrium (Na), Strontium (Sr), Schwefel (S), Tellur (Te), Thallium (Tl), Zinn (Sn), Titan (Ti), Vanadium (V) und Zink (Zn).
Dieses Dokument kann auch auf den Aufschluss anderer Elemente angewandt werden, sofern der Anwender die Anwendbarkeit überprüft hat.

Sols, biodéchets traités, boues et déchets - Digestion des éléments solubles dans l’eau régale (ISO 54321:2020)

Le présent document spécifie deux méthodes de digestion de sols, de biodéchets traités, de boues et de déchets en utilisant une digestion à l'eau régale.
La digestion à l'eau régale n'aboutit pas nécessairement à une décomposition totale de l'échantillon. Les concentrations des analytes extraits peuvent ne pas nécessairement refléter les teneurs totales dans l'échantillon, mais représentent les métaux solubles dans l'eau régale dans les conditions du présent mode opératoire d'essai. Il est généralement admis qu'aux fins d'analyses environnementales, les résultats sont adaptés à la finalité prévue, à savoir la protection de l'environnement.
Le présent document est applicable aux éléments suivants:
aluminium (Al), antimoine (Sb), arsenic (As), baryum (Ba), béryllium (Be), bore (B), cadmium (Cd), calcium (Ca), chrome (Cr), cobalt (Co), cuivre (Cu), fer (Fe), plomb (Pb), magnésium (Mg), manganèse (Mn), mercure (Hg), molybdène (Mo), nickel (Ni), phosphore (P), potassium (K), sélénium (Se), argent (Ag), sodium (Na), strontium (Sr), soufre (S), tellure (Te), thallium (Tl), étain (Sn), titane (Ti), vanadium (V) et zinc (Zn).
Le présent document peut également être appliqué à la digestion d'autres éléments, à condition que l'utilisateur en ait vérifié l'applicabilité.

Tla, obdelani biološki odpadki, blato in odpadki - Razklop frakcij elementov, topnih v zlatotopki (ISO 54321:2020)

General Information

Status
Published
Public Enquiry End Date
02-Jan-2020
Publication Date
08-Mar-2021
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
21-Aug-2020
Due Date
26-Oct-2020
Completion Date
09-Mar-2021

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SLOVENSKI STANDARD
SIST EN ISO 54321:2021
01-april-2021

Tla, obdelani biološki odpadki, blato in odpadki - Razklop frakcij elementov, topnih

v zlatotopki (ISO 54321:2020)

Soil, treated biowaste, sludge and waste - Digestion of aqua regia soluble fractions of

elements (ISO 54321:2020)

Boden, behandelter Bioabfall, Schlamm und Abfall - Aufschluss von mit Königswasser

löslichen Anteilen von Elementen (ISO 54321:2020)

Sols, biodéchets traités, boues et déchets - Digestion des éléments solubles dans l’eau

régale (ISO 54321:2020)
Ta slovenski standard je istoveten z: EN ISO 54321:2021
ICS:
13.030.20 Tekoči odpadki. Blato Liquid wastes. Sludge
13.080.10 Kemijske značilnosti tal Chemical characteristics of
soils
SIST EN ISO 54321:2021 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 54321:2021
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SIST EN ISO 54321:2021
EN ISO 54321
EUROPEAN STANDARD
NORME EUROPÉENNE
January 2021
EUROPÄISCHE NORM
ICS 13.030.20; 13.080.10
English Version
Soil, treated biowaste, sludge and waste - Digestion of aqua
regia soluble fractions of elements (ISO 54321:2020)

Sols, biodéchets traités, boues et déchets - Digestion Boden, behandelter Bioabfall, Schlamm und Abfall -

des éléments solubles dans l'eau régale (ISO Aufschluss von mit Königswasser löslichen Anteilen

54321:2020) von Elementen (ISO 54321:2020)
This European Standard was approved by CEN on 18 July 2020.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 54321:2021 E

worldwide for CEN national Members.
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SIST EN ISO 54321:2021
EN ISO 54321:2021 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 54321:2021
EN ISO 54321:2021 (E)
European foreword

This document (EN ISO 54321:2021) has been prepared by Technical Committee ISO/TC 190 "Soil

quality" in collaboration with Technical Committee CEN/TC 444 “Environmental characterization of

solid matrices” the secretariat of which is held by NEN.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by July 2021, and conflicting national standards shall be

withdrawn at the latest by July 2021.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of

North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the

United Kingdom.
Endorsement notice

The text of ISO 54321:2020 has been approved by CEN as EN ISO 54321:2021 without any modification.

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SIST EN ISO 54321:2021
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SIST EN ISO 54321:2021
INTERNATIONAL ISO
STANDARD 54321
First edition
2020-08
Soil, treated biowaste, sludge and
waste — Digestion of aqua regia
soluble fractions of elements
Sols, biodéchets traités, boues et déchets — Digestion des éléments
solubles dans l’eau régale
Reference number
ISO 54321:2020(E)
ISO 2020
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SIST EN ISO 54321:2021
ISO 54321:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
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SIST EN ISO 54321:2021
ISO 54321:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 2

5 Interferences and sources of errors ................................................................................................................................................. 2

6 Reagents ........................................................................................................................................................................................................................ 3

7 Apparatus ..................................................................................................................................................................................................................... 3

7.1 General ........................................................................................................................................................................................................... 3

7.2 Method A — Apparatus for thermal heating under atmospheric conditions ................................... 3

7.2.1 Method A1 — Thermal heating under reflux conditions .............................................................. 3

7.2.2 Method A2 — Thermal heating with a heating block with containers ............................. 4

7.3 Method B — Microwave digestion with temperature control, closed vessels ................................. 4

8 Procedure..................................................................................................................................................................................................................... 5

8.1 General ........................................................................................................................................................................................................... 5

8.2 Blank test ..................................................................................................................................................................................................... 5

8.3 Method A — thermal heating under atmospheric conditions ....................................................................... 5

8.3.1 Method A1 — Thermal heating under reflux conditions .............................................................. 5

8.3.2 Method A2 — Thermal heating with a heating block with containers ............................. 6

8.4 Method B — Microwave digestion with temperature control, closed vessels ................................. 7

9 Test report ................................................................................................................................................................................................................... 7

Annex A (informative) Repeatability and reproducibility data for soil, biowaste and sludge

samples ........................................................................................................................................................................................................................... 9

Annex B (informative) Repeatability and reproducibility data for waste samples ..........................................10

Bibliography .............................................................................................................................................................................................................................37

© ISO 2020 – All rights reserved iii
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SIST EN ISO 54321:2021
ISO 54321:2020(E)
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 190, Soil quality, Subcommittee

SC 3, Chemical and physical characterization, in collaboration with the European Committee for

Standardization (CEN) Technical Committee CEN/TC 444, Environmental characterization of solid

matrices, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna

Agreement).

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 2020 – All rights reserved
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SIST EN ISO 54321:2021
ISO 54321:2020(E)
Introduction

Regarding the comparability of the procedure described in this document with those of the other

standards mentioned above the next remarks can be made:
— This document describes the digestion of solid samples with aqua regia.

— Differences in the procedures of the different standards are small. An important difference between

the reflux procedures as described in ISO 11466 and EN 13657 and EN 16174 concerns the waiting

time after addition of the acid to the sample, before the digestion starts. ISO 11466 specifies a

waiting time of 16 h, both European standards state that the digestion can start after the first strong

reactions have ceased. In validation work it was proven that the difference between 2 h and 16 h of

waiting was negligible, therefore this document follows the approach of EN 13657 and EN 16174.

— The heating block procedure was added to the reflux and microwave digestion procedures. The

procedure was adopted from the Dutch standard NEN 6961, which specifies a boiling time of 2 h to

4 h. This document specifies a boiling time of 2 h.

The methods specified in this document are providing multi-element aqua regia digestion techniques

for soil, treated biowaste, sludge and waste prior to analysis. It is known that the digestion of

environmental samples with aqua regia will not necessarily lead to complete element recoveries, and

that the extract from a test sample may not reflect the total concentrations of the target analytes.

However, for most environmental applications the result obtained based upon digestion methods

specified in this document are considered to be fit for the intended purpose.

This document is validated for several types of matrices as indicated in Table 1.

Table 1 — Matrices for which this document is validated
Matrix Materials used in the validation test
Municipal sludge
Industrial sludge
Sludge Sludge from electronic industry
Ink waste sludge
Sewage sludge
Compost
Biowaste (Meth-
od A)
Composted sludge
Agricultural soil
Soil
Sludge amended soils
City waste incineration fly ash (“oxidised” matrix)
City waste incineration bottom ash (“silicate” matrix)
Ink waste sludge (organic matrix)
Waste
Electronic industry sludge (“metallic” matrix)
BCR 146R (sewage sludge)
BCR 176 (city waste incineration ash)

WARNING — Persons using this document should be familiar with usual laboratory practice.

Some of the reagents used in this document are highly corrosive and very toxic. Safety

precautions are absolutely necessary, not only due to the strong corrosive reagents, but also to

the high temperature and high pressure.

The use of laboratory-grade microwave equipment with isolated and corrosion resistant safety

devices is required. Domestic (kitchen) type microwave ovens shall not be used, as corrosion

by acid vapours may compromise the function of the safety devices and prevent the microwave

© ISO 2020 – All rights reserved v
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SIST EN ISO 54321:2021
ISO 54321:2020(E)

magnetron from shutting off when the door is open, which could result in operator exposure to

hazardous levels of microwave energy.

All procedures should be performed in a fume hood or in closed force-ventilated equipment. By

the use of strong oxidising reagents, the formation of explosive organic intermediates is possible,

especially when dealing with samples with a high organic content. Do not open pressurized

vessels before they have cooled down. Avoid contact with the chemicals and the gaseous reaction

products.

IMPORTANT — It is absolutely essential that tests conducted according to this document be

carried out by suitably trained staff.
vi © ISO 2020 – All rights reserved
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SIST EN ISO 54321:2021
INTERNATIONAL STANDARD ISO 54321:2020(E)
Soil, treated biowaste, sludge and waste — Digestion of
aqua regia soluble fractions of elements
1 Scope

This document specifies two methods for digestion of soil, treated biowaste, sludge and waste by the

use of an aqua regia digestion.

Digestion with aqua regia will not necessarily accomplish total decomposition of the sample. The

extracted analyte concentrations may not necessarily reflect the total content in the sample but

represent the aqua regia soluble metals under the condition of this test procedure. It is generally agreed

that for environmental analysis purposes, the results are fit for the intended purpose to protect the

environment.
This document is applicable for the following elements:

Aluminium (Al), antimony (Sb), arsenic (As), barium (Ba), beryllium (Be), boron (B), cadmium (Cd),

calcium (Ca), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), magnesium (Mg),

manganese (Mn), mercury (Hg), molybdenum (Mo), nickel (Ni), phosphorus (P), potassium (K),

selenium (Se), silver (Ag), sodium (Na), strontium (Sr), sulfur (S), tellurium (Te), thallium (Tl), tin (Sn),

titanium (Ti), vanadium (V), and zinc (Zn).

This document can also be applied for the digestion of other elements, provided the user has verified

the applicability.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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/
3.1
aqua regia

digestion (3.2) solution obtained by mixing 1 volume of nitric acid (mass fraction of 65 % to 70 %) and

3 volumes of hydrochloric acid (mass fraction of 35 % to 37 %)

Note 1 to entry: These mass percentages agree with the concentrations of 6.2 and 6.3.

3.2
digestion

mineralization of the organic matter of a sample and dissolution of its mineral part, more or less

completely, when reacting with a reagent mixture
3.3
dry residue

dry matter expressed as a percentage by mass after drying at 105 °C ± 5 °C to the constancy of weight

© ISO 2020 – All rights reserved 1
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SIST EN ISO 54321:2021
ISO 54321:2020(E)
3.4
laboratory sample
sample (3.5) intended for laboratory inspection of testing
[SOURCE: ISO 11074:2015, 4.3.7]
3.5
sample
portion of material selected from a larger quantity of material
[SOURCE: ISO 11074:2015, 4.1.17]
3.6
test portion
analytical portion

quantity of material of proper size for measurement of the concentration or other properties of interest,

removed from the test sample (3.7)

Note 1 to entry: The test portion may be taken from the laboratory sample directly if no preparation of sample is

required (e. g. with liquids), but usually it is taken from the prepared test sample.

Note 2 to entry: A unit or increment of proper homogeneity, size and fineness, needing no further preparation,

may be a test portion.
[SOURCE: ISO 11074:2015, 4.3.15]
3.7
test sample
analytical sample

portion of material resulting from the laboratory sample (3.4) by means of an appropriate method of

sample pre-treatment and having the size (volume/mass) necessary for the desired testing or analysis

[SOURCE: ISO 11074:2015, 4.1.3]
4 Principle

A test portion is digested with aqua regia according to one of the following heating procedures:

— Method A: procedure under atmospheric conditions
— A1: reflux for (120 ± 10) min, followed by filtration/centrifugation;

— A2: heating block at (105 ± 5) °C for (120 + 10) min, followed by filtration/centrifugation.

— Method B: microwave digestion

— B1: Temperature controlled procedure: at (175 ± 5) °C for (10 ± 1) min in a closed vessel followed

by filtration/centrifugation.
5 Interferences and sources of errors

The container in which the sample is delivered and stored can be a source of errors. Its material shall

be chosen according to the elements to be determined (e.g. elemental Hg can penetrate polyethylene

walls very fast in both directions. Glass can contaminate samples with its major elements: e.g. B, Na, K,

Si and Al).

Grinding or milling samples includes a risk of contamination of the sample by the environment (air, dust,

wear of milling equipment). Due to elevated temperature losses of volatile compounds are possible.

For the determination of elements forming volatile compounds (e.g. Hg, As) special care has to be taken

during sample pre-treatment.
2 © ISO 2020 – All rights reserved
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SIST EN ISO 54321:2021
ISO 54321:2020(E)

All glassware and plastics ware shall be adequately cleaned and stored in order to avoid any

contamination.

In the case of filtration of the digested solution it is necessary to take care that the filtration procedure

does not introduce contaminants.

Ensure that all of the test portion is brought into contact with the acid mixture in the digestion vessel.

Some elements of interest can be lost due to precipitation with ions present in the final digest solution,

e.g. low soluble chlorides, fluorides and sulfates.
6 Reagents

Use only acids and reagents of recognized analytical grade to avoid high blank values for subsequent

analytical measurements. Use a test blank solution throughout the procedure applying all steps with

the same amount of acids, but without a sample.
6.1 Water, e.g. deionized.
6.2 Hydrochloric acid, c(HCl) ≈ 12 mol/l.
6.3 Nitric acid, c(HNO ) ≈ 15 mol/l.
6.4 Nitric acid, c(HNO ) ≈ 0,5 mol/l.
Dilute 35 ml nitric acid (6.3) to 1 l with water (6.1).
6.5 Antifoaming agent, e.g. n-dodecane (C H ) or n-octanol (C H O) are suitable.
12 26 8 18
7 Apparatus
7.1 General

Usual laboratory apparatus. All glassware and plastics ware shall be adequately cleaned and stored in

order to avoid any contamination.

Depending upon the concentration of the element of interest, particular care should be exercised with

respect to the effective cleaning of the vessels.
7.2 Method A — Apparatus for thermal heating under atmospheric conditions
7.2.1 Method A1 — Thermal heating under reflux conditions

7.2.1.1 Digestion vessel, temperature- and pressure-resistant and capable of containing the mixture

of sample and digest solution, for example a quartz vessel. The digestion vessel shall have a volume of at

least 5 times of the volume of the aqua regia used. The inner wall of the vessel shall be inert and shall not

release substances to the digest in excess of the purity requirements of the subsequent analysis.

NOTE 1 Silica or borosilicate glass vessels can be used instead of quartz vessels.

NOTE 2 It can be necessary to periodically clean the digestion vessels with a suitable surfactant to remove

persistent deposits.
7.2.1.2 Reflux condenser, adaptable to the digestion vessel (7.2.1.1).
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ISO 54321:2020(E)

7.2.1.3 Absorption vessel, volatile species trap, in an open digestion system capable of trapping one

or more volatile measurement species, adaptable to the reflux condenser (7.2.1.2).

7.2.1.4 Heating device, for example a heating mantle, thermostatic controlled, or an aluminium block

thermostat.
7.2.2 Method A2 — Thermal heating with a heating block with containers

7.2.2.1 Digestion tube, 50 ml propylene tube with a screw cap from polypropylene.

The part of the tube not being heated and the screw cap function as a condenser, but are not really

a reflux system. The material of the tube and screw cap need to be tested in order to be sure that

release of elements of interest does not take place. Other materials and vessels with other volumes than

mentioned above are allowed to be used if suitability has been proven.

7.2.2.2 Temperature controlled heating block, heating block able to heat the tube(s) to a temperature

of (105 ± 5) °C.
7.3 Method B — Microwave digestion with temperature control, closed vessels

7.3.1 Digestion vessel, for pressurized microwave digestion, typically 100 ml volume, reagent-,

temperature- and pressure-resistant and capable of containing the mixture of sample and digest solution.

The vessel shall be suitable for the safe application in the temperature and pressure range applied,

capable of withstanding pressures of at least 3 000 kPa.

Digestion vessels made of perfluoroalkoxylalkane (PFA), modified polytetrafluoroethylene (PTFE) or

quartz, and equipped with a safety pressure releasing system to avoid explosion of the vessel, shall

be used. The inner wall of the vessel shall be inert and shall not release contaminations to the digest

solution.

It can be necessary to periodically clean the digestion vessels with a suitable surfactant to remove

persistent deposits.

7.3.2 Microwave digestion system, corrosion resistant and well ventilated. All electronics shall be

protected against corrosion for safe operation.

Use a laboratory-grade microwave oven with temperature feedback control mechanisms.

The microwave digestion system should be able to control the temperature with an accuracy of ±5 °C

and automatically adjust the microwave field output power within 2 s of sensing. Temperature sensors

shall be accurate to ±2 °C, including the final reaction temperature of (175 ± 5) °C. Temperature

feedback control provides the primary performance mechanism for the method. Due to the variability

in sample matrix types and microwave digestion equipment (i.e. different vessel types and microwave

designs), control of the temperature during digestion is important for reproducible microwave heating

and comparable data. Manufacturer specifications of the microwave digestion system must fit these

specifications. The accuracy of the temperature measurement system should be periodically tested

on blank samples at an elevated temperature according to the manufactures instructions. If the

temperature deviates by more than 2 °C from the temperature measured by an external, calibrated

temperature measurement system, the microwave temperature measurement system should be re-

calibrated.
7.4 Sample containers, plastics and glass containers are both suitable.

7.5 Filter paper, usually with a pore size of 0,45 µm and resistant to the diluted aqua regia final

digestion solution.
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SIST EN ISO 54321:2021
ISO 54321:2020(E)
7.6 Volumetric flasks, usually of nominal capacity of 50 ml or 100 ml.
7.7 Analytical balance, with an accuracy of 1 mg or better.

7.8 Boiling aids, anti-bumping granules or glass beads, diameter 2 mm to 3 mm, acid washed.

8 Procedure
8.1 General

Pre-treat, soil, sludge and biowaste samples according to e.g. EN 16179 or ISO 11464 and waste samples

according to e.g. EN 15002.

Determine the dry matter content, depending on the matrix of the sample, e.g. according to EN 15934.

For waste samples the next remarks apply:

— Pre-treatment should include drying or grain size reduction below a particle size of 250 µm for solid

waste or homogenizing by use of a high speed mixer or sonification for liquid waste samples.

— The mass of test portion for a single digestion has to be selected in a way, that:

— it is representative for the laboratory sample;
— it complies with the specifications of manufacturer of the digestion unit.

Referring to the manufacturer’s instructions, the upper limits of mass of the test portion shall be taken

into account.

— For representativeness reasons a mass above 200 mg is to be preferred for the test portion. Follow,

for safety reasons, the manufacturer’s instructions regarding the maximum amount of organic

carbon in the sample.
8.2 Blank test

Carry out a reagent blank test digestion in parallel with the determination, using the same procedure

and the same quantities of all the reagents as in the determination, but omitting the test portion. The

laboratory shall define acceptable limits.

NOTE The measurement of a blank is introduced to determine the contribution of the extracting solution,

glassware, digestion tube and filter paper used to the measured value.
8.3 Method A — thermal heating under atmospheric conditions
8.3.1 Method A1 — Thermal heating under reflux conditions

Weigh approximately 3 g of the test sample (waste samples 1 g to 10 g), with an accuracy of 0,001 g (or

at least three significant
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