SIST EN ISO 12846:2012
(Main)Water quality - Determination of mercury - Method using atomic absorption spectrometry (AAS) with and without enrichment (ISO 12846:2012)
Water quality - Determination of mercury - Method using atomic absorption spectrometry (AAS) with and without enrichment (ISO 12846:2012)
ISO 12846:2012 specifies two methods for the determination of mercury in drinking, surface, ground, rain and waste water after appropriate pre-digestion. For the first method, an enrichment step by amalgamation of the Hg on, for example, a gold/platinum adsorber is used. For the second method, the enrichment step is omitted.
The choice of method depends on the equipment available, the matrix and the concentration range of interest. Both methods are suitable for the determination of mercury in water. The method with enrichment commonly has a practical working range from 0,01 µg/l to 1 µg/l. The mean limit of quantification (LOQ) reported by the participants of the validation trial was 0,008 µg/l. This information on the LOQ gives the user of ISO 12846:2012 an orientation and does not replace the estimation of performance data from laboratory specific data. It has to be considered that it is possible to achieve lower LOQs with specific instrumentation (e.g. single mercury analysers).
The method without enrichment commonly has a practical working range starting at 0,05 µg/l. The LOQ reported by the participants of the validation trial was 0,024 µg/l. It is up to the user, based on the specific application, to decide whether higher concentrations are determined by omitting the enrichment step and/or by diluting the sample(s). The sensitivity of both methods is dependent on the selected operating conditions.
Another possibility for the determination of extremely low Hg concentrations down to 0,002 µg/l without pre-concentration is the application of atomic fluorescence spectrometry (see ISO 17852). Specific atomic-absorption mercury analysers allow determinations down to 0,010 µg/l without pre-concentration.
In general, the determination of trace concentrations of Hg by AAS (or AFS) is dependent on clean operating conditions in the laboratory and on the use of high-purity chemicals with negligible low-Hg blanks.
Note that ISO 12846:2012 may be applied to industrial and municipal waste water after an additional digestion step performed under appropriate conditions and after suitable method validation. A potential sample stability issue (mercury loss) for anaerobic reducing industrial effluents has to be considered thoroughly.
Wasserbeschaffenheit - Bestimmung von Quecksilber - Verfahren mittels Atomabsorptionsspektrometrie (AAS) mit und ohne Anreicherung (ISO 12846:2012)
Diese internationale Norm legt zwei Verfahren zur Bestimmung von Quecksilber in Trink-, Oberflächen-, Grund-, Regen- und Abwasser nach einem geeigneten Vor-Aufschluss fest. Im ersten Verfahren, beschrieben in Abschnitt 6, wird ein Anreicherungsschritt durch Amalgamieren des Quecksilbers z. B. auf Gold- oder Platin-Adsorbentien genutzt. Bei dem in Abschnitt 7 beschriebenen Verfahren wird auf den Anreicherungsschritt verzichtet. Die Wahl des Verfahrens ist abhängig von der zur Verfügung stehenden Ausrüstung, der Matrix und dem Konzentrationsbereich. Beide Verfahren sind geeignet zur Bestimmung von Quecksilber in Wasser. Das Verfahren mit Anreichungsschritt (siehe Abschnitt 6) ist üblicherweise in einem Bereich von 0,03 µg/l bis 1 µg/l anwendbar. Die mittlere Bestimmungsgrenze (BG), ermittelt durch die Teilnehmer des Validierungsringversuchs (siehe Anhang A), lag bei 0,017 µg/l. Dies kann als Anhaltspunkt genutzt werden. Der Arbeitsbereich für das Verfahren ohne Anreichungsschritt (siehe Abschnitt 7) beginnt üblicherweise bei 0,05 µg/l. Die durch die Teilnehmer des Validierungsringversuchs (siehe Anhang A) ermittelte mittlere Bestimmungsgrenze lag bei 0,024 µg/l. Es ist dem Anwender überlassen, zu entscheiden, ob höhere Konzentrationen durch Weglassen des Anreicherungsschritts oder durch Verdünnung der Proben in dem jeweiligen Verfahren bestimmt werden. Die Empfindlichkeit beider Verfahren ist abhängig von den gewählten Betriebsbedingungen. Eine andere Möglichkeit zur Bestimmung von extrem niedrigen Quecksilberkonzentrationen bis zu 0,002 µg/l ohne eine Anreicherung ist die Anwendung der Atomfluoreszenzspektroskopie (siehe ISO 17852). Bestimmte Atomabsorptions-Quecksilber-Analysatoren erlauben Bestimmungen bis zu einer Konzentration von 0,010 µg/l ohne vorhergehende Anreicherung.
Qualité de l'eau - Dosage de mercure - Méthode par spectrométrie d'absorption atomique (SAA) avec et sans enrichissement (ISO 12846:2012)
Kakovost vode - Določevanje živega srebra - Metoda atomske absorpcijske spektrometrije (AAS) s predkoncentracijo ali brez nje (ISO 12846:2012)
Ta mednarodni standard določa dve metodi za določevanje živega srebra v pitni, površinski, deževni in odpadni vodi po ustreznem predhodnem razklopu. Prva metoda (opisana v točki 6) vključuje fazo predkoncentracije, in sicer amalgamiranje Hg na primer zlat/platinast adsorber. Pri metodi, navedeni v točki 7, faze predkoncentracije ni. Izbira metode je odvisna od opreme, ki je na voljo, matrice in aktualnega območja koncentracije. Obe metodi sta primerni za določevanje živega srebra v vodi. Praktični delovni razpon metode s predkoncentracijo (glejte točko 6) je navadno od 0,01 μg/l do 1 μg/l. Povprečna poročana meja kvantifikacije (LOQ) pri validacijskem poskusu (glejte Dodatek A) je bila 0,008 μg/l. Te informacije o meji kvantifikacije so smernice za uporabnika tega mednarodnega standarda in ne nadomeščajo ocene podatkov o delovanju na podlagi laboratorijskih podatkov. Upoštevati je treba, da je nižje meje kvantifikacije mogoče doseči z nekaterimi instrumenti (npr. analizatorji živega srebra). Praktični delovni razpon metode brez predkoncentracije (glejte točko 7) se pogosto začne pri 0,05 μg/l. Poročana meja kvantifikacije pri validacijskem poskusu (glejte Dodatek A) je bila 0,024 μg/l. Uporabnik se mora na podlagi specifične uporabe odločiti, ali se bodo višje koncentracije določale brez faze predkoncentracije in/ali z redčenjem vzorcev. Občutljivost obeh metod je odvisna od izbranih delovnih razmer. Še ena možnost za določevanje izredno nizkih koncentracij Hg do 0,002 μg/l brez predkoncentracije je atomska fluorescenčna spektrometrija (glejte standard ISO 17852) Specifični atomski absorpcijski analizatorji živega srebra omogočajo določevanje brez predkoncentracije do 0,010 μg/l. Na splošno je določevanje koncentracij Hg v sledovih z atomsko absorpcijsko spektrometrijo (AAS) (ali atomsko fluorescenčno spektrometrijo (AFS) odvisno od čistih delovnih razmer v laboratoriju in uporabe zelo čistih kemikalij z zanemarljivimi surovci z majhnimi količinami Hg.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 12846:2012
01-junij-2012
1DGRPHãþD
SIST ISO 5666:2000
.DNRYRVWYRGH'RORþHYDQMHåLYHJDVUHEUD0HWRGDDWRPVNHDEVRUSFLMVNH
VSHNWURPHWULMH $$6 VSUHGNRQFHQWUDFLMRDOLEUH]QMH ,62
Water quality - Determination of mercury - Method using atomic absorption spectrometry
(AAS) with and without enrichment (ISO 12846:2012)
Wasserbeschaffenheit - Bestimmung von Quecksilber - Verfahren mittels
Atomabsorptionsspektrometrie (AAS) mit und ohne Anreicherung (ISO 12846:2012)
Qualité de l'eau - Dosage de mercure - Méthode par spectrométrie d'absorption
atomique (SAA) avec et sans enrichissement (ISO 12846:2012)
Ta slovenski standard je istoveten z: EN ISO 12846:2012
ICS:
13.060.50 3UHLVNDYDYRGHQDNHPLþQH Examination of water for
VQRYL chemical substances
SIST EN ISO 12846:2012 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 12846:2012
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SIST EN ISO 12846:2012
EUROPEAN STANDARD
EN ISO 12846
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2012
ICS 13.060.50
English Version
Water quality - Determination of mercury - Method using atomic
absorption spectrometry (AAS) with and without enrichment
(ISO 12846:2012)
Qualité de l'eau - Dosage du mercure - Méthode par Wasserbeschaffenheit - Bestimmung von Quecksilber -
spectrométrie d'absorption atomique (SAA) avec et sans Verfahren mittels Atomabsorptionsspektrometrie (AAS) mit
enrichissement (ISO 12846:2012) und ohne Anreicherung (ISO 12846:2012)
This European Standard was approved by CEN on 14 April 2012.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same
status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 12846:2012: E
worldwide for CEN national Members.
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SIST EN ISO 12846:2012
EN ISO 12846:2012 (E)
Contents Page
Foreword .3
2
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SIST EN ISO 12846:2012
EN ISO 12846:2012 (E)
Foreword
This document (EN ISO 12846:2012) 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 October 2012, and conflicting national standards shall be withdrawn at
the latest by October 2012.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland, Turkey and the United Kingdom.
Endorsement notice
The text of ISO 12846:2012 has been approved by CEN as a EN ISO 12846:2012 without any modification.
3
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SIST EN ISO 12846:2012
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SIST EN ISO 12846:2012
INTERNATIONAL ISO
STANDARD 12846
First edition
2012-04-15
Water quality — Determination of
mercury — Method using atomic
absorption spectrometry (AAS) with and
without enrichment
Qualité de l’eau — Dosage du mercure — Méthode par spectrométrie
d’absorption atomique (SAA) avec et sans enrichissement
Reference number
ISO 12846:2012(E)
©
ISO 2012
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SIST EN ISO 12846:2012
ISO 12846:2012(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2012
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO’s
member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2012 – All rights reserved
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SIST EN ISO 12846:2012
ISO 12846:2012(E)
Contents Page
Foreword .iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Principle . 2
4 General interferences . 2
5 Sample collection and pre-treatment for drinking, surface, ground and rain-water samples . 3
6 Determination of mercury after tin(II) chloride reduction and enrichment by amalgamation . 4
6.1 Reagents and standards . 4
6.2 Apparatus and instrumentation . 6
6.3 Instrumental set-up . 8
6.4 Procedure . 8
6.5 Calculation . 9
7 Determination of mercury after tin(II) chloride reduction without enrichment . 9
7.1 Reagents and standards . 9
7.2 Apparatus and instrumentation . 9
7.3 Sample collection and pre-treatment for drinking, surface, ground and rain-water samples .10
7.4 Sample collection and pre-treatment for waste-water samples .10
7.5 Instrumental set-up .10
7.6 Procedure .10
7.7 Calculation . 11
8 Expression of results . 11
9 Test report . 11
Annex A (informative) Performance data .12
Bibliography .15
© ISO 2012 – All rights reserved iii
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SIST EN ISO 12846:2012
ISO 12846:2012(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 2.
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 document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 12846 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2, Physical,
chemical and biochemical methods.
This first edition of ISO 12846 cancels and replaces the editions (ISO 5666:1999, ISO 16590:2000), which
have been technically revised.
iv © ISO 2012 – All rights reserved
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SIST EN ISO 12846:2012
ISO 12846:2012(E)
Introduction
In natural water sources, mercury compounds generally occur in very low concentrations of less than 0,1 µg/l.
Higher concentrations may be found, for example, in industrial waste water. Both inorganic and organic
compounds of mercury may be present. Mercury can also accumulate in sediments and sludges.
In order to fully decompose all of the mercury compounds in the presence of particles in the sample, an
additional digestion procedure is necessary. This additional digestion can be omitted only if significant amounts
of previous comparison data clearly demonstrate this.
For reliable measurements in the low-concentration range, the highest purity reagents, clean vessels, mercury-
free air in the laboratory and a very stable measurement system are essential.
This International Standard is a state-of-the-art revision of existing standards for the determination of mercury
by AAS with and without a pre-enrichment step combining the advantages of the existing methods with new
developments and technique. The following methods are considered:
A) Methods without enrichment:
— ISO 5666:1999, Water quality — Determination of mercury;
— EN 1483:2007, Water quality — Determination of mercury — Method using atomic absorption spectrometry.
B) Methods with enrichment:
— ISO 16590:2000, Water quality — Determination of mercury — Methods involving enrichment by
amalgamation;
— EN 12338:1998, Water quality — Determination of mercury — Enrichment methods by amalgamation.
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SIST EN ISO 12846:2012
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SIST EN ISO 12846:2012
INTERNATIONAL STANDARD ISO 12846:2012(E)
Water quality — Determination of mercury — Method using atomic
absorption spectrometry (AAS) with and without enrichment
WARNING – Potassium bromate, used in significant quantities for sample preservation in this
International Standard, is carcinogenic and suitable safety precautions shall be taken. Precautions
should be taken to detoxify any residual bromate by reduction to bromide before disposal.
Persons using this International Standard should be familiar with normal laboratory practice. This
standard 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.
IMPORTANT — It is absolutely essential that tests conducted in accordance with this International
Standard be carried out by suitably qualified staff. Mercury and mercury compounds are very toxic.
Extreme caution should be exercised when handling samples and solutions which contain or may
contain mercury.
1 Scope
This International Standard specifies two methods for the determination of mercury in drinking, surface,
ground, rain and waste water after appropriate pre-digestion. For the first method (described in Clause 6), an
enrichment step by amalgamation of the Hg on, for example, a gold/platinum adsorber is used. For the method
given in Clause 7, the enrichment step is omitted.
The choice of method depends on the equipment available, the matrix and the concentration range of interest.
Both methods are suitable for the determination of mercury in water. The method with enrichment (see Clause 6)
commonly has a practical working range from 0,01 µg/l to 1 µg/l. The mean limit of quantification (LOQ)
reported by the participants of the validation trial (see Annex A) was 0,008 µg/l. This information on the LOQ
gives the user of this International Standard an orientation and does not replace the estimation of performance
data based on laboratory-specific data. It has to be considered that it is possible to achieve lower LOQs with
specific instrumentation (e.g. single mercury analysers).
The method without enrichment (in Clause 7) commonly has a practical working range starting at 0,05 µg/l. The
LOQ reported by the participants of the validation trial (see Annex A) was 0,024 µg/l. It is up to the user, based on
the specific application, to decide whether higher concentrations are determined by omitting the enrichment step
and/or by diluting the sample(s). The sensitivity of both methods is dependent on the selected operating conditions.
Another possibility for the determination of extremely low Hg concentrations down to 0,002 µg/l without
pre-concentration is the application of atomic fluorescence spectrometry (see ISO 17852). Specific atomic-
absorption mercury analysers allow determinations down to 0,010 µg/l without pre-concentration.
In general, the determination of trace concentrations of Hg by AAS (or AFS) is dependent on clean operating
conditions in the laboratory and on the use of high-purity chemicals with negligible low-Hg blanks.
NOTE This International Standard may be applied to industrial and municipal waste water after an additional digestion
step performed under appropriate conditions and after suitable method validation (see 7.4). A potential sample stability
issue (mercury loss) for anaerobic reducing industrial effluents has to be considered thoroughly.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable
for its application. For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
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SIST EN ISO 12846:2012
ISO 12846:2012(E)
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 5667-1, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes and
sampling techniques
ISO 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples
ISO 8466-1, Water quality — Calibration and evaluation of analytical methods and estimation of performance
characteristics — Part 1: Statistical evaluation of the linear calibration function
ISO 8466-2, Water quality — Calibration and evaluation of analytical methods and estimation of performance
characteristics — Part 2: Calibration strategy for non-linear second order calibration functions
3 Principle
Mono- or divalent mercury and organo-mercury compounds as well are converted to divalent mercury by
oxidation with KBrO -KBr and then reduced to the elemental form by tin(II) chloride in an acid medium.
3
Elemental mercury is then stripped from the solution with the aid of a stream of inert gas or mercury-free air.
Alternatively, samples may be preserved with dichromate/HNO and digested under appropriate conditions
3
(e.g. using potassium permanganate/potassium peroxodisulfate). This technique is not part of this International
Standard and has therefore to be validated appropriately by the user.
If the enrichment step is applied, the mercury (in the form of atomic vapour) is transported in a stream of inert
gas with negligible mercury content to a quartz tube with a suitable heating and adsorbent (e.g. gold-platinum
gauze) on which the mercury is adsorbed.
Other adsorbents based on the principle of amalgamation are allowed if the user demonstrates fitness for purpose.
The mercury is then released by rapid heating of the adsorbent (desorption at 600 °C as a minimum) and
further transported in a stream of carrier gas to the absorption cell where the absorbance is measured at
253,7 nm in the radiation beam of an atomic absorption spectrometer. Concentrations are calculated using a
calibration curve or using the standard addition method.
If the enrichment step is omitted, the mercury is transported directly into a cuvette. Absorbances are also
measured at a wavelength of 253,7 nm.
4 General interferences
With mercury, there is a risk that exchange reactions, that is adsorption and desorption, will occur on the walls
of the sampling and reaction vessels. The instructions in 6.2.5.2 should therefore be followed exactly.
Mercury vapour can diffuse through various plastics; this phenomenon needs to be taken into consideration
in the choice of tubing material. Glass or special plastics tubing, e.g. FEP tubes [FEP = perfluoro(ethene-
propene)], should be used. Silicone tubing, for example, is unsuitable.
Easily reducible elements, such as gold, silver and platinum, amalgamate with elemental mercury and may
therefore cause suppression. Additionally, iodide is a significant interferent causing severe suppression of the
mercury signal.
Volatile organic substances can absorb in the UV range and although automatic background correction is used
to compensate for this, it still results in a degraded signal-to-noise ratio.
All solutions should be brought to the same temperature (<25 °C) before reduction and stripping of the mercury
vapour. Water condensation on the cuvette windows has to be prevented, e.g. by heating the cuvette with, for
example, an infrared lamp.
NOTE Tin(II) chloride causes extensive contamination of the apparatus with tin. Considerable interferences occur if
tin has to be determined afterwards on the same system.
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SIST EN ISO 12846:2012
ISO 12846:2012(E)
Table 1 provides acceptable maximum concentrations of some matrix elements in the measurement solution known
not to cause interference. Above the given concentrations, the elements listed may cause significant interferences
by reducing the original signal for more than 10 %. Interference effects were tested with a 100 ng/l standard.
Table 1 — Acceptable concentrations of some matrix elements
in a measurement solution
Values in mg/l
Reducing agent SnCl (6.1.8)
2
Medium 0,5 mol/l HCl
Element
Cu(II) 500
Ni(II) 500
Ag(I) 1
I(-I) 0,1
As(V) 0,5
Bi(III) 0,5
Sb(III) 0,5
Se(IV) 0,05
5 Sample collection and pre-treatment for drinking, surface, ground and rain-
water samples
Carry out the sampling as specified in ISO 5667-1 and ISO 5667-3 using only the sampling vessels
specified in 6.2.5.2.
Make sure that the sampling vessel contains no mercury and causes no loss of mercury by adsorption or diffusion.
With the following approach, a combined preservation and digestion step is carried out on the arrival of samples
in the laboratory.
Stabilize the samples by adding 1,0 ml of hydrochloric acid (6.1.7) per 100 ml of the sample, preferably
during the sampling in the field. To avoid handling the acid during field sampling and to minimize the risk of
contamination, it is recommended that the hydrochloric acid (6.1.7) be placed in a bottle in the laboratory
prior to sampling. In this case, the bottle shall be filled without first being rinsed with the sample. On arrival
of the samples at the laboratory, add 2 ml of the potassium bromide/potassium bromate reagent (6.1.4) per
100 ml of the sample. Samples shall be preserved within 48 h of collection. The maximum allowable time for
adding the bromide/bromate reagent is 6 d after collection. Allow the samples to stand for at least 30 min. If
the yellow colouration due to free bromine does not persist after 30 min, add a further 1 ml of the potassium
bromide/potassium bromate reagent (6.1.4) and allow the samples to stand for another 30 min.
NOTE In order to calculate the dilution factor of the sample caused by adding the reagent, the volume of the sample
can, for example, be determined by weighing both the full sample bottle and the empty and dry sample bottle.
WARNING — The bromate/bromide reagent should be added in the laboratory due to potential health
and safety hazards to sampling operatives.
Note that volume correction is necessary.
Prepare a reagent blank (6.1.9) containing the same amounts of reagents and analyse along with the
corresponding sample. If additional potassium bromide/potassium bromate reagent (6.1.4) is added to the
samples, the same amounts shall be added to the standards used for the calibration.
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SIST EN ISO 12846:2012
ISO 12846:2012(E)
If preserved samples are to be stored, analyse them within 2 weeks after collection. The maximum storage time
is 4 weeks after collection. An indication of insufficient stability of the sample is the decolourisation caused by
the progressing consumption of free bromine.
For all aqueous samples, prepare a field blank and analyse as required. Use the same type of container and
the same quantity of all reagents as were used in the sample collection. Treat the field blank like a sample.
If waste waters are to be analysed, see 7.4 with regard to the pre-treatment of samples.
6 Determination of mercury after tin(II) chloride reduction and enrichment by
amalgamation
6.1 Reagents and standards
Reagents and water can contain mercury as an impurity. For high sensitivity, use ultra-pure reagents or those
with a particularly low mercury content compared to the lowest analyte concentration.
6.1.1 Water, with a purity fulfilling the requirements for grade 1, as specified in ISO 3696 for all sample
preparations and dilutions.
6.1.2 Potassium bromate solution, c(KBrO ) = 0,033 3 mol/l.
3
Dissolve 1,39 g of potassium bromate in 250 ml of water (6.1.1). Potassium bromate can be purified, if necessary,
by heating in a muffle furnace overnight at 250 °C ± 20 °C.
The solution is stable for about 1 month.
6.1.3 Potassium bromide solution, c(KBr) = 0,2 mol/l.
Dissolve 5,95 g of potassium bromide in 250 ml of water (6.1.1). Potassium bromide can be purified, if necessary,
by heating in a muffle furnace overnight at 300 °C ± 20 °C.
The solution is stable for about 1 month.
6.1.4 Potassium bromide/potassium bromate reagent.
Mix equal volumes of potassium bromate (6.1.2) and potassium bromide solution (6.1.3). A total volume of
200 ml will allow digestion for 100 samples.
NOTE Pre-mixed ampoules for potassium bromate/bromide stock solution are commercially available. This reagent
has been found to contain negligible mercury concentrations.
The reagent can remain stable for several days and up to several weeks. This point shall be checked. The
solution should be colourless.
6.1.5 Hydroxylammonium chloride solution, ρ(NH ClOH) = 120 g/l.
4
Dissolve 6,0 g of hydroxylammonium chloride in water (6.1.1) in a 50 ml volumetric flask and make up to volume.
This solution may be purified by the addition of 1,0 ml of SnCl solution (6.1.8) and purging overnight at
2
500 ml/min with Hg-free N . Flow injection systems may require less SnCl for purification of the solution.
2 2
The solution is stable for about 1 month.
NOTE An ascorbic acid solution (L-ascorbic acid, 100 g/l) is also permissible. It is up to the user of this International
Standard to demonstrate the fitness for purpose of this reduction procedure.
6.1.6 Nitric acid, ρ(HNO ) = 1,4 g/ml.
3
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SIST EN ISO 12846:2012
ISO 12846:2012(E)
NOTE Nitric acid is available both as ρ(HNO ) = 1,40 g/ml [w(HNO ) = 650 g/kg] and ρ(HNO ) = 1,42 g/ml
3 3 3
[w(HNO ) = 690 g/kg]. Both are suitable for use in this method provided the mercury content is negligible.
3
6.1.7 Hydrochloric acid, (HCl), w(HCl) = 360 g/kg [ρ(HCl) = 1,19 g/ml].
Depending on the working range of the method, the hydrochloric acid used to stabilize the sample and standards
can be further purified using the following procedure.
Add 1 ml of the tin(II) chloride solution (6.1.8) to 1 l of the acid. Bubble the solution with argon, nitrogen or air,
e.g. at a flow rate of 2 l/min for 15 min. The initial SnCl concentration in the HCl is 0,002 %.
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6.1.8 Tin(II) chloride solution, ρ(SnCl⋅2H O) = 20 g/l.
2 2
Add 10,0 g of tin(II) chloride dihydrate to 50 ml of hydrochloric acid (6.1.7). Heat to dissolve. Dilute to 500 ml
with water (6.1.1). To remove any traces of mercury, bubble the solution with argon or nitrogen, e.g. at a flow
rate of 2 l/min for 15 min.
NOTE The hydrochloric acid used to prepare this solution can be of analytical grade since any mercury present will
be removed on bubbling.
6.1.9 Reagent blank.
For each 100 ml, prepare a solution containing 1,0 ml of hydrochloric acid (6.1.7) and 2 ml of the potassium
bromide/potassium bromate reagent (6.1.4). It is essential that the same reagents used for sample and standard
preparation be used to prepare the reagent blank. Treat the reagent blank like a sample.
On the continuous-flow system, the reagent blank solution is run as a background for automatic blank subtraction.
This solution should be checked for mercury and, if found to exceed twice the reported quantification limit
(LOQ), should be rejected and prepared again using reagents with acceptably low mercury concentrations.
6.1.10 Mercury standard solutions.
All standards shall contain the same concentration of the potassium bromide/potassium bromate
reagent (6.1.4) as the samples. Increased levels of bromide suppress the mercury signal.
6.1.10.1 Mercury stock solution A, ρ(Hg) = 1 000 mg/l.
Use a commercially available quantitative standard solution.
This solution is stable for at least 6 months.
Alternatively, use a stock solution prepared from ultra-purehemicals (99,99 %/99,999 % mass
fraction pure). Dissolve 0,135 4 g of mercury(II) chloride HgCl in 20 ml water (6.1.1). Add 5 ml of nitric
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acid (6.1.6) and dilute to 100 ml with water (6.1.1).
WARNING — Do not dry the inorganic salt, it is highly toxic and volatile.
6.1.10.2 Mercury stock solution B, ρ(Hg) = 10 mg/l.
Dilute 1 ml of stock solution A (6.1.10.1) to 100 ml with reagent blank (6.1.9) in a volumetric borosilicate flask.
Prepare weekly.
6.1.10.3 Mercury stock solution C, ρ(Hg) = 100 µg/l.
Dilute 1 ml of stock solution B (6.1.10.2) to 100 ml with reagent blank (6.1.9) in a volumetric borosilicate flask.
Prepare the solution on the day of use.
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