ISO 54321:2020
(Main)Soil, treated biowaste, sludge and waste — Digestion of aqua regia soluble fractions of elements
Soil, treated biowaste, sludge and waste — Digestion of aqua regia soluble fractions of elements
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.
Sols, biodéchets traités, boues et déchets — Digestion des éléments solubles dans l’eau régale
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.
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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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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.
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Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
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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
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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.
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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
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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.
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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
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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.
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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.
3
6.4 Nitric acid, c(HNO ) ≈ 0,5 mol/l.
3
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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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 figures), and transfer to the digestion vessel (7.2.1.1).
In case of dry samples moisten the test portion with about 0,5 ml to 1,0 ml of water (6.1) and add,
dropwise, if necessary, to reduce foaming, with mixing, (21,0 ± 0,1) ml of hydrochloric acid (6.2)
followed by (7,0 ± 0,1) ml of nitric acid (6.3). Connect the reflux condenser (7.2.1.2) to the digestion
vessel (7.2.1.1). Fill the absorption vessel (7.2.1.3) with approximately 15 ml nitric acid (6.4). Connect
the absorption vessel to the reflux condenser, and let stand at room temperature until any effervescence
almost ceases to allow for slow oxidation of the organic matter in the sample.
The time of standing at room temperature can have an influence on the digestion rate of aqua regia.
For consistency, it is recommended to start heating as soon as possible after the first strong reaction
has ceased.
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ISO 54321:2020(E)
30 ml of aqua regia is only sufficient for the oxidation of about 0,5 g organic carbon. If there is any
doubt of the amount of carbon present, estimate the amount of carbon in the sample or carry out a
determination of TOC. If there is more than 0,5 g of organic carbon in the test portion, proceed as
follows.
Allow first reaction with the aqua regia to subside. Then add an extra 1 ml of nitric acid (6.3) only to
every 0,1 g of organic carbon above 0,5 g. Do not add more than 10 ml of nitric acid at any given time,
and allow any reaction to subside before proceeding further.
Connect the digestion vessel (7.2.1.1) to the heating device (7.2.1.4) and raise the temperature of the
reaction mixture to reflux conditions and maintain for 2 h ensuring that the condensation zone is lower
than 1/3 of the height of the reflux condenser, then allow to cool. Add the content of the absorption
vessel to the reaction vessel via the reflux condenser, rinsing both the absorption vessel and condenser
with further 10 ml of diluted nitric acid (6.4).
Transfer quantitatively the solution content of each vessel into a suitable sized volumetric flask and add
water (6.1) to the volume mark.
Alternatively, another procedure can be applied, such that the adjustment to volume with the solid
residue still present shall be carried out immediately after digestion.
If the measurement solution contains particles due to precipitation which may clog nebulizers or
interfere with an injection of the sample into the instrument, the sample may be centrifuged, allowed to
settle, or filtered (7.5).
The measurement solution is now ready for analysis for elements of interest using appropriate
elemental analysis techniques.
8.3.2 Method A2 — Thermal heating with a heating block with containers
Weigh an amount of not more than 2 g of the test portion (typically 0,5 g to 1 g of dry sample) containing
not more than 0,15 g of organic carbon with an accuracy of 0,001 g (or at least three significant figures)
and transfer it into the digestion vessel (7.2.2.1).
The amount of the test sample depends on the amount of organic matter. The maximum amount of
organic carbon shall not exceed 0,15 g when 8 ml of aqua regia is used. Per additional 0,1 g organic
carbon (more than this 0,15 g), 1 ml of additional concentrated HNO (6.3) shall be added before the
3
digestion process is started.
N.B.: For some elements, e.g. barium and chromium, the additional volume of HNO is essential in order
3
to have a sufficient recovery upon digestion.
In case of dry samples moisten the test portion with a few drops of water (6.1). Add (6,0 + 0,1) ml
hydrochloric acid (6.2) followed by (2,0 + 0,1) ml nitric acid (6.3). Let stand at room temperature until
any effervescence almost ceases to allow for slow oxidation of the organic matter in the sample.
The time of standing at room temperature can have an influence on the digestion rate of aqua regia.
For consistency, it is recommended to start heating as soon as possible after the first strong reaction
has ceased.
Loosely screw on the tube cap (not very tight!) and place the digestion vessel on the heating block
(7.2.2.2) and slowly increase the temperature to the boiling point. Keep the temperature on the boiling
point during (120 + 10) min.
Let the vessel cool down to room temperature and fill up with water (6.1) to the volume mark.
If a non-graduated digestion tube is used, transfer quantitatively the solution into a suitable sized
volumetric flask and add water (6.1) to the volume mark. Alternatively, another procedure can be
applied, such that the adjustment to volume with the solid residue still present shall be carried out
immediately after digestion.
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ISO 54321:2020(E)
If the measurement solution contains particles due to precipitation which may clog nebulizers or interfere
with an injection of the sample into the instrument, the sample may be centrifuged or filtered (7.5).
The measurement solution is now ready for analysis for elements of interest using appropriate
elemental analysi
...
NORME ISO
INTERNATIONALE 54321
Première édition
2020-08
Sols, biodéchets traités, boues et
déchets — Digestion des éléments
solubles dans l’eau régale
Soil, treated biowaste, sludge and waste — Digestion of aqua regia
soluble fractions of elements
Numéro de référence
ISO 54321:2020(F)
©
ISO 2020
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ISO 54321:2020(F)
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2020
Tous droits réservés. Sauf prescription différente ou nécessité dans le contexte de sa mise en œuvre, aucune partie de cette
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Publié en Suisse
ii © ISO 2020 – Tous droits réservés
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ISO 54321:2020(F)
Sommaire Page
Avant-propos .iv
Introduction .v
1 Domaine d’application . 1
2 Références normatives . 1
3 Termes et définitions . 1
4 Principe . 2
5 Interférences et sources d’erreur . 2
6 Réactifs . 3
7 Appareillage . 3
7.1 Généralités . 3
7.2 Méthode A — Appareillage de chauffage thermique en conditions atmosphériques . 3
7.2.1 Méthode A1 — Chauffage thermique en conditions atmosphériques . 3
7.2.2 Méthode A2 — Chauffage thermique, à l’aide d’un bloc chauffant avec des
récipients . 4
7.3 Méthode B — Digestion par micro-ondes, avec régulation de la température, dans
des récipients fermés . 4
8 Mode opératoire. 5
8.1 Généralités . 5
8.2 Essai à blanc . 6
8.3 Méthode A — Chauffage thermique en conditions atmosphériques . 6
8.3.1 Méthode A1 — Chauffage thermique en conditions atmosphériques . 6
8.3.2 Méthode A2 — Chauffage thermique, à l’aide d’un bloc chauffant avec des
récipients . 7
8.4 Méthode B — Digestion par micro-ondes, avec régulation de la température, dans
des récipients fermés . 7
9 Rapport d’essai . 8
Annexe A (informative) Données de répétabilité et de reproductibilité relatives aux
échantillons de sol, de biodéchet et de boue . 9
Annexe B (informative) Données de répétabilité et de reproductibilité relatives aux
échantillons de déchets .10
Bibliographie .38
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ISO 54321:2020(F)
Avant-propos
L'ISO (Organisation internationale de normalisation) est une fédération mondiale d'organismes
nationaux de normalisation (comités membres de l'ISO). L'élaboration des Normes internationales est
en général confiée aux comités techniques de l'ISO. Chaque comité membre intéressé par une étude
a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,
gouvernementales et non gouvernementales, en liaison avec l'ISO participent également aux travaux.
L'ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui
concerne la normalisation électrotechnique.
Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont
décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier, de prendre note des différents
critères d'approbation requis pour les différents types de documents ISO. Le présent document a été
rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir www
.iso .org/ directives).
L'attention est attirée sur le fait que certains des éléments du présent document peuvent faire l'objet de
droits de propriété intellectuelle ou de droits analogues. L'ISO ne saurait être tenue pour responsable
de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant
les références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de
l'élaboration du document sont indiqués dans l'Introduction et/ou dans la liste des déclarations de
brevets reçues par l'ISO (voir www .iso .org/ brevets).
Les appellations commerciales éventuellement mentionnées dans le présent document sont données
pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un
engagement.
Pour une explication de la nature volontaire des normes, la signification des termes et expressions
spécifiques de l'ISO liés à l'évaluation de la conformité, ou pour toute information au sujet de l'adhésion
de l'ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les obstacles
techniques au commerce (OTC), voir www .iso .org/ avant -propos.
Le présent document a été élaboré par le comité technique ISO/TC 190, Qualité du sol, sous-comité SC 3,
Méthodes chimiques et caractéristiques physiques, en collaboration avec le comité technique CEN/TC 444,
Méthodes d'essai pour la caractérisation environnementale des matrices solides, du Comité européen de
normalisation (CEN) conformément à l’Accord de coopération technique entre l’ISO et le CEN (Accord de
Vienne).
Il convient que l’utilisateur adresse tout retour d’information ou toute question concernant le présent
document à l’organisme national de normalisation de son pays. Une liste exhaustive desdits organismes
se trouve à l’adresse www .iso .org/ fr/ members .html.
iv © ISO 2020 – Tous droits réservés
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ISO 54321:2020(F)
Introduction
En ce qui concerne la comparabilité du mode opératoire décrit dans le présent document avec ceux des
autres normes mentionnées ci-dessus, les remarques suivantes peuvent être faites:
— le présent document décrit la digestion d’échantillons solides par de l’eau régale;
— les différences entre les modes opératoires des différentes normes sont minimes. Une différence
importante entre les modes opératoires de reflux décrits dans l’ISO 11466, l’EN 13657 et l’EN 16174
porte sur le temps d’attente après l’ajout de l’acide à l’échantillon, avant le début de la digestion.
L’ISO 11466 spécifie un temps d’attente de 16 h; les deux Normes européennes indiquent que la
digestion peut commencer après la fin des premières réactions fortes. Il a été prouvé, lors de travaux
de validation, que la différence entre 2 h et 16 d’attente était négligeable, c’est pourquoi le présent
document suit l’approche de l’EN 13657 et de l’EN 16174;
— le mode opératoire avec bloc chauffant a été ajouté aux modes opératoires de digestion par micro-
ondes et à reflux. Le mode opératoire a été tiré de la norme néerlandaise NEN 6961 qui spécifie un
temps d’ébullition de 2 h à 4 h. Le présent document spécifie un temps d’ébullition de 2 h.
Les méthodes spécifiées dans le présent document fournissent des techniques de digestion à l’eau
régale de plusieurs éléments contenus dans les sols, les biodéchets traités, les boues et les déchets avant
l’analyse. Il est connu que la digestion à l’eau régale d’échantillons prélevés dans l’environnement ne
conduit pas nécessairement à une décomposition complète des éléments et que l’extrait obtenu à partir
d’un échantillon pour essai peut ne pas refléter les concentrations totales des analytes cibles. Cependant,
pour la plupart des applications environnementales, les résultats obtenus par les méthodes de digestion
spécifiées dans le présent document sont considérés comme pertinents pour la finalité prévue.
Le présent document est validé pour plusieurs types de matrices, comme indiqué dans le Tableau 1.
Tableau 1 — Matrices pour lesquelles le présent document est validé
Matrice Matériaux utilisés dans l’essai de validation
Boues urbaines
Boues industrielles
Boues Boues produites par l’industrie électronique
Boues d’encres usagées
Boues de curage
Composte
B io dé c h e t s
(méthode A)
Boues compostées
Sols agricoles
Sol
Sols amendés par des boues
Cendres volantes d’incinération des déchets urbains (matrice «oxydée»)
Mâchefers d’incinération des déchets urbains (matrice «silicatée»)
Boues résiduaires d’encre (matrice «organique»)
Déchet
Boues d’industrie électronique (matrice «métallique»)
BCR 146R (boues de curage)
BCR 176 (cendres d’incinération des déchets urbains)
AVERTISSEMENT — Il convient que les utilisateurs du présent document connaissent bien les
pratiques courantes de laboratoire. Certains des réactifs utilisés dans le présent document sont
fortement corrosifs et très toxiques. Il est absolument nécessaire de prendre des mesures de
sécurité, non seulement en raison des réactifs fortement corrosifs, mais aussi de la température
et de la pression élevées.
© ISO 2020 – Tous droits réservés v
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ISO 54321:2020(F)
Un matériel à micro-ondes de laboratoire muni de dispositifs de sécurité isolés et résistants
à la corrosion est requis. Les fours à micro-ondes à usage domestique (cuisine) ne doivent pas
être utilisés, car la corrosion par les vapeurs acides peut compromettre le fonctionnement des
dispositifs de sécurité et empêcher l’arrêt du magnétron à l’ouverture de la porte, ce qui pourrait
entraîner une exposition de l’opérateur à des niveaux dangereux d’énergie de micro-ondes.
Il convient que toutes les étapes des modes opératoires soient réalisées sous une hotte
ventilée ou dans un équipement fermé à ventilation forcée. Du fait de l’utilisation de réactifs
fortement oxydants, la formation de produits organiques intermédiaires explosifs est possible,
en particulier lors du traitement d’échantillons à forte teneur en matières organiques. Ne pas
ouvrir les récipients sous pression avant qu’ils n’aient refroidi. Éviter tout contact avec les
produits chimiques et les produits de réaction gazeux.
IMPORTANT — Il est absolument essentiel que les essais réalisés conformément au présent
document soient effectués par du personnel ayant suivi une formation appropriée.
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NORME INTERNATIONALE ISO 54321:2020(F)
Sols, biodéchets traités, boues et déchets — Digestion des
éléments solubles dans l’eau régale
1 Domaine d’application
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.
2 Références normatives
Le présent document ne contient aucune référence normative.
3 Termes et définitions
Pour les besoins du présent document, les termes et définitions suivants s’appliquent.
L’ISO et l’IEC tiennent à jour des bases de données terminologiques destinées à être utilisées en
normalisation, consultables aux adresses suivantes:
— ISO Online browsing platform: disponible à l’adresse https:// www .iso .org/ obp
— IEC Electropedia: disponible à l’adresse http:// www .electropedia .org/
3.1
eau régale
solution de digestion (3.2) obtenue en mélangeant 1 volume d’acide nitrique (fraction massique de 65 %
à 70 %) et 3 volumes d’acide chlorhydrique (fraction massique de 35 % à 37 %)
Note 1 à l'article: Ces pourcentages massiques sont en accord avec les concentrations indiquées en 6.2 et 6.3.
3.2
digestion
minéralisation de la matière organique d’un échantillon et dissolution de sa partie minérale, plus ou
moins complètement, quand elle est mise en réaction avec un mélange de réactifs
3.3
matière sèche
résidu sec exprimé en pourcentage massique après séchage à 105 °C ± 5 °C jusqu’à poids constant
© ISO 2020 – Tous droits réservés 1
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ISO 54321:2020(F)
3.4
échantillon pour laboratoire
échantillon (3.5) destiné à être utilisé pour un contrôle ou pour des essais en laboratoire
[SOURCE: ISO 11074:2015, 4.3.7]
3.5
échantillon
partie de matériau choisie dans une quantité de matériau plus grande
[SOURCE: ISO 11074:2015, 4.1.17]
3.6
prise d’essai
partie analysée
quantité de matériau, prélevée dans l’échantillon pour essai (3.7), suffisante pour permettre la mesure
de la concentration ou de toute autre propriété étudiée
Note 1 à l'article: Si, en l’absence de toute préparation, la prise d’essai peut être prélevée directement dans
l’échantillon pour laboratoire (par exemple dans le cas de liquides), elle est généralement prélevée dans
l’échantillon préparé pour essai.
Note 2 à l'article: On peut considérer comme prise d’essai une unité ou un prélèvement élémentaire suffisamment
homogène et pur(e), de taille appropriée, et qui ne nécessite aucune autre préparation.
[SOURCE: ISO 11074:2015, 4.3.15]
3.7
échantillon pour essai
échantillon analysé
prise de matériau, issue de l’échantillon pour laboratoire (3.4) au moyen d’une méthode appropriée de
traitement préalable des échantillons, et ayant la taille (volume/masse) nécessaire pour les essais ou
l’analyse souhaités
[SOURCE: ISO 11074:2015, 4.1.3]
4 Principe
Une prise d’essai est digérée à l’eau régale conformément à l’un des modes opératoires de chauffage
suivants:
— méthode A: mode opératoire en conditions atmosphériques:
— A1: reflux pendant (120 ± 10) min, suivi d’une filtration/centrifugation;
— A2: bloc chauffant à (105 ± 5) °C pendant (120 ± 10) min, suivi d’une filtration/centrifugation;
— méthode B: digestion par micro-ondes:
— B1: mode opératoire à température contrôlée: à (175 ± 5) °C pendant (10 ± 1) min dans un
réacteur fermé, suivi d’une filtration/centrifugation.
5 Interférences et sources d’erreur
Le récipient dans lequel l’échantillon est livré et conservé peut être source d’erreurs. Sa matière doit
être choisie en fonction des éléments à analyser (par exemple, le mercure élémentaire peut pénétrer
dans les parois en polyéthylène très rapidement, aussi bien dans un sens que dans l’autre. Le verre peut
contaminer des échantillons avec ses principaux éléments, par exemple B, Na, K, Si et AI).
2 © ISO 2020 – Tous droits réservés
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ISO 54321:2020(F)
Le broyage des échantillons comporte un risque de contamination de l’échantillon par l’environnement
(par exemple air, poussière, usure de l’équipement de broyage). Des pertes de composés volatils sont
possibles à températures élevées.
En vue de la détermination des éléments formant des composés volatils (par exemple Hg, As), un soin
tout particulier doit être apporté lors du prétraitement de l’échantillon.
L’ensemble de la verrerie et du matériel plastique doit être nettoyé et stocké de façon appropriée, afin
d’éviter toute contamination.
En cas de filtration de la solution après digestion, il est nécessaire de veiller à ce que le mode opératoire
de filtration n’introduise pas de contaminants.
S’assurer que la totalité de la prise d’essai est mise en contact avec le mélange acide dans le flacon de
digestion.
Certains éléments étudiés peuvent être perdus en raison d’une précipitation avec des ions présents
dans la solution de digestion finale, par exemple les chlorures, fluorures et sulfates peu solubles.
6 Réactifs
Utiliser uniquement des acides et des réactifs de qualité analytique reconnue afin d’éviter des valeurs
de blanc élevées pour les mesures analytiques ultérieures. Utiliser une solution d’essai à blanc tout au
long du mode opératoire, en suivant toutes les étapes et en appliquant les mêmes quantités d’acides,
mais sans inclure d’échantillon.
6.1 Eau, par exemple déionisée.
6.2 Acide chlorhydrique, c(HCl) ≈ 12 mol/l.
6.3 Acide nitrique, c(HNO ) ≈ 15 mol/l.
3
6.4 Acide nitrique, c(HNO ) ≈ 0,5 mol/l.
3
Diluer 35 ml d’acide nitrique (6.3) à 1 l avec de l’eau (6.1).
6.5 Agent antimoussant, le n-dodécane (C H ) ou le n-octanol (C H O) par exemple, sont
12 26 8 18
appropriés.
7 Appareillage
7.1 Généralités
Matériel courant de laboratoire. L’ensemble de la verrerie et du matériel plastique doit être nettoyé et
stocké de façon appropriée, afin d’éviter toute contamination.
Suivant la concentration de l’élément à analyser, il convient d’apporter un soin tout particulier au
nettoyage efficace des récipients.
7.2 Méthode A — Appareillage de chauffage thermique en conditions atmosphériques
7.2.1 Méthode A1 — Chauffage thermique en conditions atmosphériques
7.2.1.1 Réacteur de digestion, résistant à la température et à la pression et pouvant contenir le
mélange de l’échantillon et de la solution de digestion, par exemple un flacon en quartz. Le récipient
de réaction doit avoir un volume d’au moins cinq fois celui de l’eau régale utilisée. La paroi interne des
© ISO 2020 – Tous droits réservés 3
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ISO 54321:2020(F)
récipients doit être inerte et ne doit pas libérer de substances dans la solution de digestion à un niveau
supérieur aux exigences de pureté de l’analyse ultérieure.
NOTE 1 Des récipients en silice ou en borosilicate peuvent être utilisés à la place des récipients en quartz.
NOTE 2 Il peut être nécessaire de nettoyer périodiquement les réacteurs de digestion avec un agent tensioactif
approprié afin d’éliminer les dépôts tenaces.
7.2.1.2 Réfrigérant à reflux pouvant s’adapter sur le récipient de digestion (7.2.1.1).
7.2.1.3 Chambre d’absorption, piège pour les substances volatiles servant, dans un système de
digestion ouvert, à piéger une ou plusieurs substances volatiles à mesurer, pouvant s’adapter sur le
réfrigérant à reflux (7.2.1.2).
7.2.1.4 Dispositif de chauffage, par exemple un chauffe-ballon avec thermostat ou un bloc chauffant
en aluminium avec thermostat.
7.2.2 Méthode A2 — Chauffage thermique, à l’aide d’un bloc chauffant avec des récipients
7.2.2.1 Tube de digestion, tube en propylène de 50 ml muni d’un bouchon à vis en polypropylène.
La partie non chauffée du tube et le bouchon à vis fonctionnent comme un réfrigérant, mais ne
constituent pas vraiment un système à reflux. Il est nécessaire de soumettre à essai la matière du tube
et du bouchon à vis pour vérifier l’absence de libération des éléments étudiés. Il est permis d’utiliser
d’autres matières et des récipients de volumes différents que ceux susmentionnés si leur adéquation a
été démontrée.
7.2.2.2 Bloc chauffant avec régulation de la température, bloc chauffant pouvant chauffer le(s)
tube(s) à une température de (105 ± 5) °C.
7.3 Méthode B — Digestion par micro-ondes, avec régulation de la température, dans
des récipients fermés
7.3.1 Réacteur de digestion, pour digestion par micro-ondes sous pression, typiquement d’un
volume de 100 ml, résistant au réactif, à la température et à la pression et pouvant contenir le mélange
de l’échantillon et de la solution de digestion. Le réacteur doit être utilisable en toute sécurité dans la
gamme de températures et de pressions appliquée, et doit pouvoir supporter des pressions d’au moins
3 000 kPa.
Les réacteurs de digestion utilisés doivent être en perfluoroalkoxylalcane (PFA), en
polytétrafluoréthylène modifié (PTFE) ou en quartz, et doivent être équipés d’un système de protection
contre la surpression permettant d’éviter leur explosion. La paroi interne du réacteur doit être inerte et
ne doit pas libérer de contaminants dans la solution de digestion.
Il peut être nécessaire de nettoyer périodiquement les réacteurs de digestion avec un agent tensioactif
approprié afin d’éliminer les dépôts tenaces.
7.3.2 Système de digestion par micro-ondes, résistant à la corrosion et bien ventilé. Toute
l’électronique doit être protégée contre la corrosion pour un fonctionnement en toute sécurité.
Utiliser un four à micro-ondes de laboratoire équipé d’une régulation de la puissance couplée à une
mesure de la température.
Il convient que le système de digestion par micro-ondes soit capable de réguler la température avec une
exactitude de ± 5 °C et de régler automatiquement la puissance de sortie du champ de micro-ondes dans
les 2 s qui suivent la détection. Les capteurs de température doivent avoir une exactitude de ± 2 °C, y
compris pour la température finale de réaction de (175 ± 5) °C. La régulation de la puissance couplée
4 © ISO 2020 – Tous droits réservés
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ISO 54321:2020(F)
à une mesure de la température constitue le principal mécanisme de performance de la méthode.
En raison de la variabilité des types de matrices d’échantillons et de l’équipement de digestion par
micro-ondes (c’est-à-dire différents types de réacteurs et différentes conceptions de micro-ondes),
la régulation de la température pendant la digestion est importante pour la reproductibilité du
chauffage aux micro-ondes et la comparabilité des données. Les spécifications du fabricant du système
de digestion par micro-ondes doivent être conformes à ces spécifications. Il convient de contrôler
périodiquement l’exactitude du système de mesure de la température sur des échantillons à blanc à
une température élevée conformément aux instructions du fabricant. Si la température s’écarte de plus
de 2 °C de la température mesurée par un système de mesure de la température externe étalonné, il
convient d’étalonner à nouveau le système de mesure de la température du four à micro-ondes.
7.4 Récipients à échantillons, des récipients en matière plastique ou en verre sont appropriés.
7.5 Papier-filtre, habituellement d’une taille de pore de 0,45 µm et résistant à la solution de digestion
dans l’eau régale finale diluée.
7.6 Fioles jaugées, habituellement d’une capacité nominale de 50 ml ou 100 ml.
7.7 Balance analytique, ayant une exactitude de 1 mg ou mieux.
7.8 Régulateurs d’ébullition, granules anti-projection ou billes de verre, de 2 mm à 3 mm de diamètre,
lavées à l’acide.
8 Mode opératoire
8.1 Généralités
Prétraiter les échantillons de sols, boues et biodéchets conformément à l’EN 16179 ou à l’ISO 11464 et
les échantillons de déchets conformément à l’EN 15002, par exemple.
Déterminer la teneur en matière sèche, en fonction de la matrice de l’échantillon, par exemple selon les
indications de l’EN 15934.
Pour les échantillons de déchets, les remarques suivantes s’appliquent:
— il convient que le prétraitement comprenne le séchage, la réduction granulométrique en dessous
d’une taille de particule de 250 µm pour des déchets solides, l’homogénéisation à l’aide d’un
mélangeur rapide ou la sonification pour les échantillons liquides;
— la masse de la prise d’essai à analyser pour une seule digestion doit être choisie de façon à être:
— représentative de l’échantillon pour laboratoire;
— conforme aux spécifications du fabricant de l’unité de digestion;
Les masses limites supérieures de la prise d’essai indiquées dans les instructions du fabricant doivent
être prises en compte.
— pour des raisons de représentativité, une masse supérieure à 200 mg est préférable pour la prise
d’essai. Pour des raisons de sécurité, suivre les instructions du fabricant relatives à la quantité
maximale de carbone organique dans l’échantillon.
© ISO 2020 – Tous droits réservés 5
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ISO 54321:2020(F)
8.2 Essai à blanc
Effectuer un essai de digestion à blanc parallèlement à la détermination, en suivant le même mode
opératoire et en utilisant les mêmes quantités de réactifs que pour la détermination, mais sans inclure
la prise d’essai. Le laboratoire doit définir les limites acceptables.
NOTE Le mesurage d’un blanc permet de déterminer la contribution de la solution d’extraction, de la
verrerie, du tube à digestion et du papier-filtre à la valeur mesurée.
8.3 Méthode A — Chauffage thermique en conditions atmosphériques
8.3.1 Méthode A1 — Chauffage thermique en conditions atmosphériques
Peser environ 3 g de l’échantillon pour essai (1 g à 10 g pour les échantillons de déchets) à 0,001 g près
(ou au moins avec trois chiffres après la virgule), et les transférer dans un récipient de digestion (7.2.1.1).
Si les échantillons sont secs, humidifier la prise d’essai avec environ 0,5 ml à 1,0 ml d’eau (6.1) et ajouter
tout en mélangeant, si nécessaire goutte à goutte pour réduire la formation de mousse, (21,0 ± 0,1) ml
d’acide chlorhydrique (6.2) puis (7,0 ± 0,1) ml d’acide nitrique (6.3). Raccorder le réfrigérant à reflux
(7.2.1.2) au réacteur de digestion (7.2.1.1). Remplir la chambre d’absorption (7.2.1.3) avec environ 15 ml
d’acide nitrique (6.4). Raccorder la chambre d’absorption au réfrigérant à reflux et laisser reposer à
température ambiante jusqu’à ce que l’effervescence ait presque cessé afin de permettre l’oxydation
lente des matières organiques dans l’échantillon.
Le temps de repos à température ambiante peut avoir une influence sur la vitesse de digestion de l’eau
régale. Pour des raisons de cohérence, il est
...
FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 54321
ISO/TC 190/SC 3
Soil, treated biowaste, sludge and
Secretariat: DIN
waste — Digestion of aqua regia
Voting begins on:
202004-22 soluble fractions of elements
Voting terminates on:
Sols, biodéchets traités, boues et déchets — Digestion des éléments
20200617
solubles dans l’eau régale
ISO/CEN PARALLEL PROCESSING
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO
ISO/FDIS 54321:2020(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN
DARDS TO WHICH REFERENCE MAY BE MADE IN
©
NATIONAL REGULATIONS. ISO 2020
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ISO/FDIS 54321:2020(E)
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© ISO 2020
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ISO/FDIS 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
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ISO/FDIS 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 nongovernmental, 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.
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.
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ISO/FDIS 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 EN 54321 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
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ISO/FDIS 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.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 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
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ISO/FDIS 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 pretreatment.
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ISO/FDIS 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.
3
6.4 Nitric acid, c(HNO ) ≈ 0,5 mol/l.
3
Dilute 35 ml nitric acid (6.3) to 1 l with water (6.1).
6.5 Antifoaming agent, e.g. ndodecane (C H ) or noctanol (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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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 have 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 perfluoro alkoxyl alkane (PFA), modified polytetrafluoroethene (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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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, antibumping granules or glass beads, diameter 2 mm to 3 mm, acid washed.
8 Procedure
8.1 General
Pretreat, 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 representability 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 figures), and transfer to the digestion vessel (7.2.1.1).
In case of dry samples moisten the test portion with about 0,5 ml to 1,0 ml of water (6.1) and add,
dropwise, if necessary, to reduce foaming, with mixing, (21,0 ± 0,1) ml of hydrochloric acid (6.2)
followed by (7,0 ± 0,1) ml of nitric acid (6.3). Connect the reflux condenser (7.2.1.2) to the digestion
vessel (7.2.1.1). Fill the absorption vessel (7.2.1.3) with approximately 15 ml nitric acid (6.4). Connect
the absorption vessel to the reflux condenser, and let stand at room temperature until any effervescence
almost ceases to allow for slow oxidation of the organic matter in the sample.
The time of standing at room temperature can have an influence on the digestion rate of aqua regia.
For consistency, it is recommended to start heating as soon as possible after the first strong reaction
has ceased.
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30 ml of aqua regia is only sufficient for the oxidation of about 0,5 g organic carbon. If there is any
doubt of the amount of carbon present, estimate the amount of carbon in the sample or carry out a
determination of TOC. If there is more than 0,5 g of organic carbon in the test portion, proceed as
follows.
Allow first reaction with the aqua regia to subside. Then add an extra 1 ml of nitric acid (6.3) only to
every 0,1 g of organic carbon above 0,5 g. Do not add more than 10 ml of nitric acid at any given time,
and allow any reaction to subside before proceeding further.
Connect the digestion vessel (7.2.1.1) to the heating device (7.2.1.4) and raise the temperature of the
reaction mixture to reflux conditions and maintain for 2 h ensuring that the condensation zone is lower
than 1/3 of the height of the reflux condenser, then allow to cool. Add the content of the absorption
vessel to the reaction vessel via the reflux condenser, rinsing both the absorption vessel and condenser
with further 10 ml of diluted nitric acid (6.4).
Transfer quantitatively the solution content of each vessel into a suitable sized volumetric flask and add
water (6.1) to the volume mark.
Alternatively, another procedure can be applied, such that the adjustment to volume with the solid
residue still present shall be carried out immediately after digestion.
If the measurement solution contains particles due to precipitation which may clog nebulizers or
interfere with an injection of the sample into the instrument, the sample may be centrifuged, allowed to
settle, or filtered (7.5).
The measurement solution is now ready for analysis for elements of interest using appropriate
elemental analysis techniques.
8.3.2 Method A2 — Thermal heating with a heating block with containers
Weigh an amount of not more than 2 g of the test portion (typically 0,5 g to 1 g of dry sample) containing
not more than 0,15 g of organic carbon with an accuracy of 0,001 g ((or at least three significant figures))
and transfer it into the digestion vessel (7.2.2.1).
The amount of the test sample depends on the amount of organic matter. The maximum amount of
organic carbon shall not exceed 0,15 g when 8 ml of aqua regia is used. Per additional 0,1 g organic
carbon (more than this 0,15 g), 1 ml of additional concentrated HNO (6.3) shall be added before the
3
digestion process is started.
N.B.: For some elements, e.g. barium and chromium, the additional volume of HNO is essential in order
3
to have a sufficient recovery upon digestion.
In case of dry samples moisten the test portion with a few drops of water (6.1). Add (6,0 + 0,1) ml
hydrochloric acid (6.2) followed by (2,0 + 0,1) ml nitric acid (6.3). Let stand at room temperature until
any effervescence almost ceases to allow for slow oxidation of the organic matter in the sample.
The time of standing at room temperature can have an influence on the digestion rate of aqua regia.
For consistency, it is recommended to start heating as soon as possible after the first strong reaction
has ceased.
Loosely screw on the tube cap (not very tight!) and place the digestion vessel on the heating block
(7.2.2.2) and slowly increase the temperature to the boiling point. Keep the temperature on the boiling
point during (120 + 10) min.
Let the vessel cool down to room temperature and fill up with water (6.1) to the volume mark.
If a non-graduated digestion tube is used, transfer quantitatively the solution into a suitable sized
volumetric flask and add water (6.1) to the volume mark. Alternatively, another procedure can be
applied, such that the adjustment to volume with the solid residue still present shall be carried out
immediately after digestion.
6
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