SIST EN ISO 15587-2:2003
(Main)Water quality - Digestion for the determination of selected elements in water - Part 2: Nitric acid digestion (ISO 15587-2:2002)
Water quality - Digestion for the determination of selected elements in water - Part 2: Nitric acid digestion (ISO 15587-2:2002)
This part of ISO 15587 specifies a method for extracting trace elements from a water sample using nitric acid as a digestion agent. The method is applicable to all types of waters with a suspended solids concentration of less than 20 g/l and a total organic carbon (TOC) concentration expressed as carbon of less than 5 g/l.
The nitric acid digestion method is empirical and it might not necessarily release elements completely. However, for most environmental applications the result is fit for purpose.
Nitric acid digestion is suitable for the release of: Al*, As, B, Ba*, Be*, Ca, Cd, Co, Cr*, Cu, Fe*, Hg, K, Mg*, Mn, Mo, Na, Ni, P, Pb, Se, Sr, Tl, V*, Zn (asterisk indicates a possible lower recovery compared to the aqua regia digestion method specified in ISO 15587-1). It is suitable for the release of Ag only if the sample is stabilized immediately after digestion. Nitric acid digestion is not suitable for Sb, Sn and for the digestion of refractory compounds such as SiO 2, TiO2 and Al2O3.
The method is generic and may be implemented using a wide variety of equipment provided the digestion composition is unchanged, the digestion temperature is known, and the digestion duration is in accordance with this temperature.
Wasserbeschaffenheit - Aufschluss für die Bestimmung ausgewählter Elemente in Wasser - Teil 2: Salpetersäure-Aufschluss (ISO 15587-2:2002)
Dieser Teil von ISO 15587 legt ein Verfahren zur Extraktion von von Spurenelementen in einer Wasserprobe durch Aufschluss mit Salpetersäure fest. Das Verfahren ist auf alle Wässer mit einer Massenkonzentration an suspendierten Stoffen kleiner 20 g/l und einer Massenkonzentration an gesamtem organisch gebundenem Kohlenstoff (TOC) kleiner 5 g/l anwendbar.
Der Salpetersäure-Aufschluss ist eine empirische Festlegung und es werden nicht unbedingt alle Elemente vollständig aufgeschlossen. Jedoch ist das Ergebnis für die meisten Fragestellungen im Bereich der Umweltanalyse geeignet.
Der Salpetersäure-Aufschluss ist geeignet für die Freisetzung von: Al*, As, B, Ba*, Be*, Ca, Cd, Co, Cr*, Cu, Fe*, Hg, K, Mg*, Mn, Mo, Na, Ni, P, Pb, Se, Sr, TI, V*, Zn. (das Sternchen weist darauf hin, dass gegebenenfalls eine gegenüber dem in ISO 15587-1, siehe [1], angegebenen Königswasser-Aufschluss verringerte Wiederfindungsrate gegeben ist). Für die Freisetzung von Ag ist er nur geeignet, wenn die Probe unmittelbar nach dem Aufschluss stabilisiert wird. Der Aufschluss ist nicht geeignet für Sb, Sn und für refraktäre Verbindungen wie SiO2, TiO2 und Al2O3.
Das Verfahren ist universell anwendbar und kann unter Verwendung verschiedener Ausrüstungen durchgeführt werden, vorausgesetzt
3 die Zusammensetzung der Aufschlusslösung wird nicht verändert,
3 die Aufschlusstemperatur ist bekannt und
3 die Aufschlussdauer und Temperatureinstellung sind angepasst.
Qualité de l'eau - Digestion pour la détermination de certains éléments dans l'eau - Partie 2: Digestion a l'acide nitrique (ISO 15587-2:2002)
L'ISO 15587-2 spécifie une méthode d'extraction d'éléments sous forme de traces dans un échantillon d'eau, en utilisant de l'acide nitrique comme agent de digestion. La méthode est applicable à tous les types d'eaux dont la concentration massique en solides en suspension est inférieure à 20 g/l et la concentration massique en carbone organique totale (COT), exprimée en carbone, est inférieure à 5 g/l.
La méthode de digestion à l'acide nitrique est empirique et elle n'extrait pas toujours en totalité les éléments. Toutefois, pour la plupart des applications environnementales, le résultat répond aux besoins.
La digestion à l'acide nitrique permet la libération des éléments suivants: Al*, As, B, Ba*, Be*, Ca, Cd, Co, Cr*, Cu, Fe*, Hg, K, Mg*, Mn, Mo, Na, Ni, P, Pb, Se, Sr, Tl, V*, Zn (l'astérisque indique un rendement potentiellement plus faible par rapport à la méthode de digestion à l'eau régale spécifiée dans l'ISO 15587-1). La méthode convient pour la libération de Ag uniquement si l'échantillon est stabilisé immédiatement après la digestion. La digestion à l'acide nitrique ne convient pas pour Sb, Sn et pour la digestion de composés réfractaires comme SiO2, TiO2 et Al2O3.
La méthode est générique et peut être mise en oeuvre à l'aide d'une grande variété de matériels sous réserve que la composition de la digestion ne soit pas modifiée, que la température de digestion soit connue, et que la durée de digestion corresponde à cette température.
Kakovost vode - Razklop za določevanje izbranih elementov v vodi - 2. del: Razklop z dušikovo (V) kislino (ISO 15587-2:2002)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 15587-2:2003
01-maj-2003
.DNRYRVWYRGH5D]NORS]DGRORþHYDQMHL]EUDQLKHOHPHQWRYYYRGLGHO
5D]NORS]GXãLNRYR 9 NLVOLQR ,62
Water quality - Digestion for the determination of selected elements in water - Part 2:
Nitric acid digestion (ISO 15587-2:2002)
Wasserbeschaffenheit - Aufschluss für die Bestimmung ausgewählter Elemente in
Wasser - Teil 2: Salpetersäure-Aufschluss (ISO 15587-2:2002)
Qualité de l'eau - Digestion pour la détermination de certains éléments dans l'eau -
Partie 2: Digestion a l'acide nitrique (ISO 15587-2:2002)
Ta slovenski standard je istoveten z: EN ISO 15587-2:2002
ICS:
13.060.50 3UHLVNDYDYRGHQDNHPLþQH Examination of water for
VQRYL chemical substances
SIST EN ISO 15587-2:2003 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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EUROPEAN STANDARD
EN ISO 15587-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2002
ICS 13.060.50
English version
Water quality - Digestion for the determination of selected
elements in water - Part 2: Nitric acid digestion (ISO 15587-
2:2002)
Qualité de l'eau - Digestion pour la détermination de Wasserbeschaffenheit - Aufschluss für die Bestimmung
certains éléments dans l'eau - Partie 2: Digestion à l'acide ausgewählter Elemente in Wasser - Teil 2: Salpetersäure-
nitrique (ISO 15587-2:2002) Aufschluss (ISO 15587-2:2002)
This European Standard was approved by CEN on 1 March 2002.
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 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2002 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 15587-2:2002 E
worldwide for CEN national Members.
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EN ISO 15587-2:2002 (E)
CORRECTED 2002-04-17
Foreword
This document (ISO 15587-2:2002) has been prepared by Technical Committee ISO/TC 147
"Water quality" in collaboration with Technical Committee CEN/TC 230 "Water analysis", the
secretariat of which is held by DIN.
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 September 2002, and conflicting
national standards shall be withdrawn at the latest by September 2002.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy,
Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the
United Kingdom.
Endorsement notice
The text of the International Standard ISO 15587-2:2002 has been approved by CEN as a
European Standard without any modifications.
NOTE Normative references to International Standards are listed in annex ZA (normative).
2
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EN ISO 15587-2:2002 (E)
Annex ZA
(normative)
Normative references to International Publicationswith their relevant
European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text, and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions
of any of these publications apply to this European Standard only when incorporated in it by
amendment or revision. For undated references the latest edition of the publication referred to
applies (including amendments).
NOTE Where an International Publication has been modified by common modifications,
indicated by (mod.), the relevant EN/HD applies.
Publication Year Title EN/HD Year
ISO 3696 1987 Water for analytical laboratory use — EN ISO 3696 1995
Specifications and test methods
ISO 5667-3 1994 Water quality – Sampling – Part 3: Guidance EN ISO 5667-3 1995
on the preservation and handling of samples
3
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INTERNATIONAL ISO
STANDARD 15587-2
First edition
2002-03-01
Water quality — Digestion for the
determination of selected elements in
water —
Part 2:
Nitric acid digestion
Qualité de l'eau — Digestion pour la détermination de certains éléments
dans l'eau —
Partie 2: Digestion à l'acide nitrique
Reference number
ISO 15587-2:2002(E)
©
ISO 2002
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ISO 15587-2:2002(E)
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ii © ISO 2002 – All rights reserved
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ISO 15587-2:2002(E)
Contents Page
Foreword.iv
1 Scope .1
2 Normative references.1
3 Term and definition .2
4 Principle.2
5 Reagents.2
6 Apparatus .2
7 Sampling.3
8 Procedure .3
9 Test report .5
Annex A (informative) Digestion in an open system using electrical heating.6
Annex B (informative) Digestion in an open system using microwave-assisted heating .8
Annex C (informative) Digestion in a closed system using microwave assisted heating.10
Annex D (informative) Digestion in a closed system using an autoclave.14
Annex E (informative) Performance checks.16
Bibliography.17
© ISO 2002 – All rights reserved iii
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ISO 15587-2:2002(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
The main task of technical committees is to prepare International Standards. Draft International Standards adopted
by the technical committees are circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this part of ISO 15587 may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 15587-2 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2, Physical,
chemical and biochemical method.
ISO 15587 consists of the following parts, under the general title Water quality — Digestion for the determination of
selected elements in water:
Part 1: Aqua regia digestion
Part 2: Nitric acid digestion
Annexes A to E of this part of ISO 15587 are for information only.
iv © ISO 2002 – All rights reserved
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INTERNATIONAL STANDARD ISO 15587-2:2002(E)
Water quality — Digestion for the determination of selected
elements in water —
Part 2:
Nitric acid digestion
WARNING — Persons using this part of ISO 15587 should be familiar with normal laboratory practice. This
part of ISO 15587 does not purport to address all of the safety problems, if any, associated with its use. It is
the responsibility of the user to establish appropriate safety and health practices and to ensure compliance
with any national regulatory conditions.
1 Scope
This part of ISO 15587 specifies a method for extracting trace elements from a water sample using nitric acid as a
digestion agent. The method is applicable to all types of waters with a suspended solids concentration of less than
20 g/l and a total organic carbon (TOC) concentration expressed as carbon of less than 5 g/l.
The nitric acid digestion method is empirical and it might not necessarily release elements completely. However, for
most environmental applications the result is fit for purpose.
Nitric acid digestion is suitable for the release of: Al*, As, B, Ba*, Be*, Ca, Cd, Co, Cr*, Cu, Fe*, Hg, K, Mg*, Mn,
Mo, Na, Ni, P, Pb, Se, Sr, Tl, V*, Zn (asterisk indicates a possible lower recovery compared to aqua regia digestion
method specified in ISO 15587-1, see reference [1]). It is suitable for the release of Ag only if the sample is
stabilized immediately after digestion. Nitric acid digestion is not suitable for Sb, Sn and for the digestion of
refractory compounds such as SiO , TiO and Al O .
2 2 2 3
The method is generic and may be implemented using a wide variety of equipment provided
the digestion composition is unchanged,
the digestion temperature is known, and
the digestion duration is in accordance with this temperature.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this part of ISO 15587. For dated references, subsequent amendments to, or revisions of, any of these publications
do not apply. However, parties to agreements based on this part of ISO 15587 are encouraged to investigate the
possibility of applying the most recent editions of the normative documents indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain
registers of currently valid International Standards.
ISO 3696:1987, Water for analytical laboratory use — Specification and test methods
ISO 5667-3:1994; Water quality — Sampling — Part 3: Guidance on the preservation and handling of samples
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ISO 15587-2:2002(E)
3 Term and definition
For the purposes of this part of ISO 15587, the following term and definition applies.
3.1
wet digestion
treatment with reactive liquid chemicals with the aim of bringing analytes into solution so as to be suitable for
subsequent analysis
NOTE The degree to which analytes are brought into solution suitable for subsequent analysis may depend on the
principle of the subsequent analysis. Some analytical methods require the element in solution independent of its chemical state,
others require a specific valence or a specific ionic species, for instance hydride atomic spectrometry, photometry and
[4]
electrochemical methods. For the latter, special attention should be paid to the presence of chemically stable organometals .
4 Principle
The test portion is digested with nitric acid at a defined temperature. The temperature is at least the boiling point
(103 °C at 101,3 kPa) and at most 175 °C. At the boiling point (101,3 kPa), the minimum duration to release the
digestible fraction is 120 min. The maximum duration is set at four times the minimum duration. By convention, both
the required minimum and maximum duration are assumed to halve with every 15 °C increase in temperature
above the boiling point (see Figure 1).
After digestion the digest is clarified, if necessary.
5 Reagents
During analysis, use only reagents of recognized analytical grade that meet the purity requirements of the
subsequent analysis. Verify their purity by performing a blank test.
5.1 Water, complying with grade 1 of ISO 3696. Grade 2 may be used if it meets the purity requirements for the
subsequent analysis.
5.2 Nitric acid, c(HNO ) = 15,8 mol/l, ρ = 1,4 kg/l.
3
Nitric acid is available both as ρ(HNO ) = 1,40 kg/l, approximately 65 % by mass and ρ(HNO ) = 1,42 kg/l,
3 3
approximately 69 % by mass. Both are suitable.
5.3 Antifoaming agent, for instance n-dodecane (C H ).
12 26
5.4 Ammonia solution, approximately 25 % by mass.
6 Apparatus
6.1 Digestion vessel, temperature- and pressure-resistant and capable of containing the mixture of sample and
digest solution.
If a closed vessel is applied, its inner wall shall be inert and shall not release substances to the digest in excess of
the purity requirements of the subsequent analysis.
6.2 Vapour recovery system, capable of recovering the evaporated digest during open digestion (e.g. reflux
condenser) and designed to minimize losses.
Materials in contact with the vapour shall be inert and shall meet the purity requirements of the subsequent
analysis.
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ISO 15587-2:2002(E)
6.3 Volatile species trap, in an open digestion system capable of trapping one or more volatile measurement
species which may pass through the vapour recovery system (6.2).
This trap may comprise condensation equipment or equipment to absorb these species in nitric acid or aqua regia.
Materials in contact with the vapour shall be inert and shall meet the purity requirements of the subsequent
analysis.
6.4 Heating device, capable of maintaining the target temperature for the required time period.
6.5 Filter paper, cellulose-based ashless type, with a median pore size adapted to the apparatus used for
analysis.
It shall not be able to release substances to the digest in excess of the purity requirements of the subsequent
analysis and shall not absorb substances from the digest beyond the level of negligible impact on trueness of the
analytical result.
6.6 Anti-bumping granules or roughened glass beads, having a diameter of 2 mm to 3 mm and acid-washed
[for instance with warm nitric acid (5.2) diluted to 10 % by volume with water (5.1)].
6.7 Volumetric flask, usually of nominal capacity 50 ml or 100 ml.
6.8 Graduated pipettes or dispensers.
7 Sampling
Handle and preserve the water sample in accordance with ISO 5667-3.
The digestion procedure (see clause 8) is based on a test portion of 25,0 ml ± 0,1 ml taken from a well-shaken
homogeneous water sample. Any test portion larger than 20 ml is allowed, provided that the volume of nitric acid is
modified proportionally.
If suspended solids make it impossible to deliver a representative test portion of a known volume, deliver the test
portion otherwise, for instance by weighing. Calculate the volume from the determination of its mass, possibly
corrected for the mass and density of solids. Report the uncertainty of the volume if it is higher than 0,1 ml for a
volume of 25 ml.
8 Procedure
8.1 Preparation
Carefully acid-wash digestion equipment in contact with the digestion solution and volumetric ware [for instance
with warm nitric acid (5.2) diluted to 10 % by volume with water (5.1)] and rinse with water (5.1).
Add a test portion of 25,0 ml ± 0,1 ml to the digestion vessel (6.1).
Add 6,25 ml ± 0,1 ml of nitric acid (5.2). The boiling point of this mixture is equal to 103 °C.
If excessive foaming occurs, add one or more drops of antifoaming agent (5.3).
Swirl and allow the mixture to stand until any visible reaction has stopped.
If the digestion vessel is of the open type, proceed with 8.2. If not, proceed with 8.3.
Examples of digestion in an open system are given in annexes A and B.
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ISO 15587-2:2002(E)
8.2 Digestion in an open system
Connect the digestion vessel (6.1) to the vapour recovery system (6.2).
Connect the volatile species trap (6.3), so as to prevent volatile measurement species from passing through the
vapour recovery system.
Place the digestion vessel in the heating device (6.4).
Increase the temperature to the boiling point.
Maintain boiling for at least 120 min. As the boiling point decreases with altitude add 20 min to the minimum
duration for every 1 000 m above sea level. The maximum allowed duration equals four times the minimum
duration.
Once the digestion period is completed, allow the digestion vessel to cool. If silver is an analyte, add 30 ml of
ammonia solution (5.4) to the digestion vessel immediately after cooling.
If the volatile species trap (6.3) is used, add the contents to the digestion vessel.
Rinse the trap and/or the condenser with water (5.1), for instance 10 ml, and decant. Collect the water in the
digestion vessel.
Dismount the digestion vessel from the digestion system.
Examples of digestion in an open system are given in annexes A and B.
8.3 Digestion in a closed system
Cap the digestion vessel (6.1) and weigh it.
Connect the digestion vessel to or place it in the heating device (6.4).
Increase the temperature of the digestion mixture slowly to temperature T between the boiling point (103 °C at
d
101,3 kPa) and 175 °C.
Maintain digestion for a period ∆t of at least 10 min and at most 480 min (101,3 kPa).
Given the digestion period ∆t, expressed in minutes, the digestion temperature T , expressed in degrees Celsius,
d
shall meet the following condition:
206,6 − 21,64 × ln(∆t) < T < 236,6 − 21,64 × ln(∆t) (1)
d
NOTE 1 Boundary conditions in equation (1) reflect the assumption of clause 4 on release kinetics and duration time.
The permitted domain of digestion temperature and duration is shown in Figure 1.
Once the digestion period is completed, allow the digestion vessel to cool. Weigh the digestion vessel and accept
the digest if the mass loss is consistent with the mass loss of a well documented reference material known to lead
to acceptable results.
Uncap and vent the digestion vessel in a fume hood.
If silver is an analyte, add 30 ml of ammonia solution (5.4) to the digestion vessel immediately after cooling.
Examples of digestion in a closed system are given in annexes C and D.
NOTE 2 Several microwave units control power rather than temperature. A procedure to establish the relationship between
microwave power and temperature is given in C.6.
4 © ISO 2002 – All rights reserved
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ISO 15587-2:2002(E)
Figure 1 — Domain of permitted digestion temperature and duration
8.4 Sample transfer
Decant the sample into a suitable acid-cleaned volumetric flask (6.7). In order to transfer the analytes
quantitatively, wash the digestion vessel (6.1) with water (5.1) and decant the washings. Collect the water in the
same volumetric flask.
If the transfer of particles that might interfere with the subsequent analysis cannot be avoided by simple
decantation, decant the digest through a filter paper (6.5), collecting the filtrate in a suitable acid-cleaned volumetric
flask (6.7). Wash the digestion vessel with water (5.1) and decant the washings through the filter paper (6.5).
Collect the filtrate in the same volumetric flask.
Fill the volumetric flask to the mark after addition of reagents required for subsequent sample handling and
analysis.
The extract is ready for determination.
Examples of performance checks are given in annex E.
9 Test report
The test report can be prepared separately or in conjunction with the test report of the subsequent analytical
method. Either of these shall include the following information:
a) a reference to this part of ISO 15587, i.e. ISO 15587-2;
b) the identity of the water sample;
c) the volume of the test portion and its uncertainty if higher than 0,5 %;
d) the conditions of digestion;
e) any deviation from this method.
© ISO 2002 – All rights reserved 5
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ISO 15587-2:2002(E)
Annex A
(informative)
Digestion in an open system using electrical heating
A.1 Principle
A test portion of a water sample, which may contain up to 20 g/l suspended solids and up to 5 g/l organic carbon, is
digested by boiling the test portion under reflux with nitric acid during a period between 120 min and 480 min.
A.2 Reagents
Use the reagents as specified in clause 5.
A.3 Apparatus
Usually, borosilicate glass is suitable for parts in contact with the digestion solution. If low concentrations of
leachable elements are to be analysed, other construction materials may be used, for instance quartz (high
temperatures) and polyethene or polypropene (low temperatures). Examples of leachable elements are B, Na,
K and Al.
A.3.1 Digestion vessel, made of borosilicate glass, and having a nominal volume of 100 ml.
A.3.2 Reflux condenser, a straight-through type, with conical ground-glass joints and made of borosilicate glass.
Water-cooled condensers with a minimum effective length of at least 200 mm have been found suitable.
A.3.3 Roughened glass beads, having a diameter of 2 mm to 3 mm and acid-washed [for instance with warm
nitric acid (5.2) diluted to 10 % by volume with grade 1 water (5.1)].
A.3.4 Temperature-controlled heating apparatus, capable of heating the contents of the digestion vessel to
reflux temperature.
A.3.5 Volumetric flask, made of borosilicate glass, and having a nominal volume of 100 ml.
A.3.6 Graduated pipettes or dispensers.
A.4 Sampling
Preserve and handle water samples in accordance with ISO 5667-3.
Take a test portion of 40 ml ± 0,2 ml from a well-shaken homogeneous water sample.
If suspended solids make it impossible to deliver a representative test portion of a known volume, the test portion
may be delivered otherwise, for instance by weighing. Calculate the volume from the determination of its mass,
possibly corrected for the mass and density of solids. Report the uncertainty of the volume if it is higher than 0,2 ml.
6 © ISO 2002 – All rights reserved
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ISO 15587-2:2002(E)
A.5 Procedure
Carefully acid-wash the digestion equipment in contact with the digestion solution and volumetric ware [for instance
with warm nitric acid (5.2) diluted to 10 % by volume with grade 1 water (5.1)].
Take a test portion of 40 ml ± 0,2 ml and transfer it to the digestion vessel (A.3.1).
Add the roughened glass beads (A.3.3).
Add 10,0 ml ± 0,2 ml of nitric acid (5.2). If excessive foaming occurs, add one or more drops of antifoaming agent
(5.3).
Swirl and allow the mixture to stand until any visible reaction has stopped.
Connect the digestion vessel to the reflux condenser (A.3.2).
Place the digestion vessel in the temperature-controlled heating apparatus (A.3.4).
Increase the temperature slowly until reflux conditions are reached, ensuring that the condensation zone is lower
than one third of the height of the condenser.
Maintain the boiling temperature for a period between 120 min and 480 min. As the boiling point (103 °C at
101,3 kPa) decreases with altitude, add 20 min to the minimum of 120 min for every 1 000 m above sea level.
Once the digestion period is completed, allow the digestion vessel to cool.
Rinse the reflux condenser with grade 1 water (5.1) and decant the washings. Collect the water in the digestion
vessel.
Dismount the digestion vessel from the digestion system.
Decant the sample into the acid-cleaned volumetric flask (A.3.5).
In order to transfer the analytes quantitatively, wash the digestion vessel with grade 1 water (5.1) and decant.
Collect the water in the same volumetric flask.
Fill the volumetric flask to the mark after addition of reagents, which are required for subsequent sample handling
and analysis.
The extract is ready for determination.
A.6 Test report
The test report can be prepared separately or in conjunction with the test report of the subsequent analytical
method. Either of these shall include the following information:
f) a reference to this part of ISO 15587, i.e. ISO 15587-2;
g) the identity of the water sample;
h) the volume of the test portion and its uncertainty if higher than 0,5 %;
i) the conditions of digestion;
j) any deviation from this method.
© ISO 2002 – All rights reserved 7
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ISO 15587-2:2002(E)
Annex B
(informative)
Digestion in an open system using microwave-assisted heating
B.1 Principle
A test portion of a water sample, which may contain up to 20 g/l suspended solids and up to 5 g/l organic carbon, is
digested by boiling the test portion under reflux in a flask heated by microwave unit with nitric acid during a period
between 120 min and 480 min.
B.2 Reagents
Use the reagents specified in clause 5. Verify their purity by performing a blank test.
B.3 Apparatus
Usually, borosilicate glass is suitable for parts in contact with the digestion solution. If low concentrations of
leachable elements are to be analysed, other construction materials may be used, for instance quartz (high
temperatures) and polyethene or polypropene (low temperatures). Examples of leachable elements are B, Na,
K and Al.
B.3.1 Digestion vessel, made of borosilicate glass, and having a nominal volume of 50 ml.
B.3.2 Reflux condenser, made of borosilicate glass.
B.3.3 Roughened glass beads, having a diameter of 2 mm to 3 mm (or anti-bumping granules), acid-washed
[for instance with warm nitric acid (5.2) diluted to 10 % by volume with grade 1 water (5.1)].
B.3.4 Microwave unit, consisting of a programmer and microwave module capable of heating the digestion
vessel to the boiling point.
B.3.5 Volumetric flask, made of borosilicate glass, and having a nominal capacity of 50 ml.
B.3.6 Graduated pipettes or dispensers.
B.4 Sampling
Water sample preserved and handled in accordance with ISO 5667-3.
Take a test portion of 20,0 ml ± 0,1 ml from a well-shaken homogeneous water sample.
If suspended solids make it impossible to deliver a representative test portion of a known volume, the test portion
may be delivered otherwise, for
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