ISO 5666:1999
(Main)Water quality — Determination of mercury
Water quality — Determination of mercury
Qualité de l'eau — Dosage du mercure
Kakovost vode – Določevanje živega srebra
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IS0
INTERNATIONAL
5666
STANDARD
First edition
1999-05-01
Determination of mercury
Water quality -
Qualit de I’eau - Dosage du mercure
Reference number
IS0 5666: 1999(E)
---------------------- Page: 1 ----------------------
IS0 5666:1999(E)
Contents
1
........................................................................................................................................................................
1 Scope
1
..............................................................................................................................................
2 Normative references
1
..............................................................................................................................................
3 General interferences
.................................................. 2
4 Determination of mercury after tin(H) chloride reduction without enrichment
...............................
9
5 Determination of mercury after sodium tetrahydroborate reduction without enrichment
11
6 Precision data .
.............................................................................................. 13
Annex A (informative) Ultrasonic digestion method
.............................................................................................. 14
Annex B (informative) Autoclave digestion method
............................................................................................. 15
Annex C (informative) Microwave digestion method
0 IS0 1999
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 the publisher.
International Organization for Standardization
l CH-1211 Geneve 20 l Switzerland
Case postale 56
Internet iso @ iso.ch
Printed in Switzerland
ii
---------------------- Page: 2 ----------------------
0 IS0
IS0 5666: 1999(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0
member bodies). The work of preparing International Standards is normally carried out through IS0 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. IS0 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.
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.
International Standard IS0 5666 was prepared by Technical Committee ISOmC 147, Water qua/it-,
Subcommittee SC 2, Physical, chemical and biochemical methods.
This first edition cancels and replaces the first editions of IS0 5666-I:1983 and IS0 5666-2:1983, which have been
technically revised.
Annexes A, B and C of this International Standard are for information only.
---------------------- Page: 3 ----------------------
0 IS0
IS0 5666:1999(E)
Introduction
In natural water sources, mercury compounds generally occur only in very low concentrations (less than 0,l pg/l).
Higher concentrations may be found, for example, in waste water. Mercury can accumulate in sediment and sludge.
Both inorganic and organic compounds of mercury may be present.
In order to fully decompose all of the mercury compounds, a digestion procedure is necessary. Digestion can be
omitted only if it is certain that the mercury concentration can be measured without this pretreatment.
For measurements in the low concentration range, highest purity reagents, clean reaction vessels, mercury-free air
in the laboratory and a very stable measurement system are essential. It should be investigated whether, and to
what extent, particular problems will require the specification of additional marginal conditions.
It is absol utely essential that tests conducted according to this International Standard are carried out by suitably
qualified s taff.
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INTERNATIONAL STANDARD o Iso IS0 5666:1999(E)
Water quality - Determination of mercury
1 scope
This International Standard specifies two methods for the determination of mercury in water, for example in ground,
surface and waste waters.
In the method described in clause 4, tin(ll) chloride is used as reducing agent. In the method given in clause 5,
sodium tetrahydroborate is used as reducing agent. The choice of the method depends on the equipment available
and the matrix (see clause 3). Both methods are suitable for the determination of mercury in the concentration
range from 0,l pg/I to 10 pg/l. Higher concentrations can be determined if the water sample is diluted.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard 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 IS0 and IEC
maintain registers of currently valid International Standards.
IS0 5667-l :I 980, Water quality - Sampling - Par? I: Guidance on the design of sampling programmes.
IS0 5667-2:1991, Water quality - Sampling - Part 2: Guidance on sampling techniques.
Part 3: Guidance on the preservation and handing of samples.
IS0 5667-3:1994, Water quality - Sampling -
3 General interferences
With mercury there is a risk that exchange reactions, i.e. adsorption and desorption, will occur on the walls of the
reaction vessel (see 4.4).
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. perfluoro(ethylene-propylene) (FEP) tubes, may be
used. Silicone tubing is unsuitable.
Volatile organic substances can absorb in the UV range and be mistaken for mercury. These are for the most part
removed by adding potassium permanganate until the solution is permanently coloured red and aerating for IO min
with an inert gas, before reduction of the mercury compounds. Often, such interference by non-specific absorption
can also be eliminated using a background compensation system.
All solutions have to be brought to the same temperature (c 25 “C) before reduction and stripping of the mercury
vapour. Water condensation on the cuvette windows can be prevented by heating the cuvette with, for example, an
infrared lamp.
The interferences which occur due to the presence of other elements in the matrix are dependent on the choice of
reducing agent. Element concentrations in excess of those listed in Table 1 can cause results which are too low.
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0 IS0
IS0 5666:1999( E)
Fewer interferences from heavy metals arise if tin(ll) chloride is used as reducing agent rather than sodium
tetrahydroborate. When using flow systems, interference effects due to heavy metals can be less than indicated in
Table 1.
Table 1 - Acceptable concentrations of some matrix elements in a measurement solution,
in milligrams per litre
Am 091 10 1
I- 100 IO
OJ
095
AS(V) 075 OS
03
Bi(lll) 0,05 OS
03 OS 095
Sb(lll)
Se( IV) 0,005 0,05 0,05
Tin(ll) chloride causes such extensive contamination of the apparatus with tin that considerable interferences
occur
if sodium tetrahydroborate is used afterwards. Separate systems are therefore essential for reductions with tin(ll)
chloride and with sodium tetrahydroborate.
WARNING - Mercury and mercury compounds are very toxic. Extreme caution should be exercised when
handling samples and solutions which contain or may contain mercury.
4 Determination of mercury after tin(H) chloride reduction without enrichment
4.1 Principle
Mono- or divalent mercury is reduced to the elemental form by tin(ll) chloride in an acid medium. Elemental mercury
is then stripped from the solution with the aid of a stream of inert gas or mercury-free air and, in the form of an
atomic gas, transported into a cuvette. Absorbances are measured at a wavelength of 253,7 nm in the radiation
beam of an atomic absorption spectrometer. Concentrations are calculated using a calibration curve.
4.2 Interferences
See also clause 3.
NOTE
Iodide in concentrations > 0,l mg/l causes interferences in the determination due to the formation of mercury
complexes. In this case another method such as reduction with sodium tetrahydroborate (see clause 5) is
necessary
Because of the redox potential of the tin(ll) chloride solution, various inorganic mercury compounds, such as
mercury sulfide and organic mercury compounds, cannot be reduced fully without digestion.
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OISO
IS0 5666:1999(E)
4.3 Reagents
4.3.1 General requirements
As a minimum, use “analytical grade” reagents or those with particularly low mercury content. Water shall be
double-distilled or of similar purity. The mercury content of the water and reagents shall be negligible compared to
the lowest analyte concentration.
4.3.2 Nitric acid, p(HNOs) = I,40 g/ml.
4.3.3 Sulfuric acid, p(H2S04) = I,84 g/ml
4.3.4 Hydrochloric acid, p(HCI) = 1 ,I 6 g/ml
4.3.5 Potassium permanganate solution
Dissolve 50 g of potassium permanganate (KMnOJ), in 1 000 ml of water.
4.3.6 Stabilizer solution
Dissolve 5 g of potassium dichromate, K2Cr207, in 500 ml of nitric acid (see 4.3.2) and dilute to 1000 ml with water.
WARNING - Potassium dichromate is toxic. Caution should be exercised when handling the solid material
or its solutions.
4.3.7 Potassium peroxodisulfate solution
Dissolve 40 g of potassium peroxodisulfate, K&08, in 1 000 ml of water.
4.3.8 Hydroxylammonium chloride solution
Dissolve 10 g of hydroxylammonium chloride, NHdOCI, in 100 ml of water.
4.3.9 Tin(ll) chloride solution
Dissolve 5 g of tin(ll)chlo dihydrate, SnCl2.2H20, in 30 ml of hydrochloric acid (4.3.4); dilute to 100 ml with
water. With flow systems, use a solution of lower concentration, e.g. 0,5 g in 100 ml. Prepare this solution fresh
daily from the more concentrated solution by diluting with water.
If a high result for the blank (4.6) is obtained, pass nitrogen through the solution for 30 min in order to remove traces
of mercury
4.3.10 Mercury stock solution I, p(Hg) = 100 mg/l
Dissolve 108,O mg of mercury(ll) oxide, HgO, in IO ml of the stabilizer solution (4.3.6); dilute to 1 000 ml with water.
1 ml of this solution corresponds to 0,l mg of mercury.
It is possible for stock solution I to be prepared from a commercially available mercury standard. This solution is
stable for at least 1 year.
Mercury stock solution II, p(Hg) = 1 mg/l
4.3.11
Add 10 ml of stabilizer solution (4.3.6) to 10 ml of stock solution I (4.3.10) and dilute to 1000 ml with water. 1 ml of
this solution corresponds to 1 pg of mercury.
The solution is stable for about 1 week.
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0 IS0
IS0 5666: 1999(E)
Mercury standard solution (I), p(Hg) = 100 pg/l
4.3.12
Add 10 ml of stabilizer solution (4.36) to 100 ml of stock solution II (4.3.11) and dilute to 1 000 ml with water. 1 ml of
this solution corresponds to 100 ng of mercury.
Prepare this solution on the day of use.
4.3.13 Mercury standard solution 0, p(Hg) = 50 pg/i
Add IO ml of stabilizer solution (4.3.6) to 50 ml of stock solution BE (4.3.11) and dilute to 1000 ml with water. 1 ml of
this solution corresponds to 50 ng of mercury.
Prepare this solution on the day of use.
4.3.14 Mercury calibration solutions
Prepare calibration solutions aopropriate for the volume and expected mercury concentrations of the measurement
I
sample solutions:
For the concentration range from 0,5 pg/l to 5 pg/l, for example, proceed as follows.
- Pipette into a series of six 100 ml volumetric flasks 1 ml, 2 ml, 4 ml, 6 ml, 8 ml and 10 ml respectively of
mercury standard solution (2) (4.3.13).
- Add 1 ml of stabilizer solution (4.3.6) to each 100 ml volumetric flask.
Fill to the mark with water and mix thoroughly.
These calibration solutions contain 0,5 pg/l, 1 pg/l, 2 pg/l, 3 pg/i, 4 pg/l and 5 pg/l mercury respectively. They shall
be prepared freshly before each series of measurements. If calibration measurements shall be done in duplicate
prepare another set of solutions.
4.3.15 Reagent blank solution
Prepare a volume of blank solution corresponding to that of the measurement solution by adding 10 ml of stabilizer
solution (4.3.6) per 1000 ml of water. Use the same digestion procedure as for the sample (4.6). Include the reagent
blank in each batch of analyses.
4.3.16 Rinsing solution for glassware
Add to about 500 ml of water 150 ml of nitric acid (4.3.2) and dilute with water to 1 000 ml.
4.4 Apparatus
4.4.1 General requirement
Before use, all glasswa re shall be washed thoroughly with dilute nitric acid (4.3.16) and then rinsed thoroughly
several times w lith water (4.3.1).
4.4.2 Atomic absorption with a monitoring system. An instrument with background correction
spectrometer
system is recommended.
4.4.3 Radiation source for the determination of mercury, e.g. a hollow cathode or electrodeless discharge lamp.
4.4.4 Mercury accessory (see Figure I), consisting of:
- abso rption cell comprised of a borosilicate glass or quartz cuvette, of in side diameter about 2 cm, length at
least .I5 cm (dependent on the AAS instrument) with quartz end-windows;
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0 IS0
IS0 5666: 1999(E)
- air-circulating pump (e.g. membrane pump, peristaltic pump), capacity 1 I/min to 2 I/min, with plastics tubing
(closed system) or inert gas cylinder with pressure-reducing valve (open system);
- flow meter with plastics (see clause 3) tubing (open system). An open system is advantageous for high concen-
trations of mercury;
- reaction vessel consisting of, for example, a 100 ml, 250 ml or 1 000 ml flat-bottomed flask as shown in the
diagram, with ground glass stopper, wash-bottle insert with glass frit of porosity 1;
- heating source for the measuring cell, sufficient to prevent condensation of water.
The temperature of the measuring cell shall be the same throughout the analysis.
An example of a closed system is shown in Figure 1.
1
Key
1 Absorption cell, i.d. 2 cm; length 15 cm
2 Air circulating pump, of capacity 1 Vmin to 2 Vmin
3 Ground glass stopper 29/32
4 Reaction flask, capacity 100 ml, 250 ml or 1 000 ml
5 Glass frit
Care should be taken with regard to the choice of plastics material for pumps and tubing (see clause 3).
NOTE 1
NOTE 2 A continuous flow or flow injection system is possible as an alternative. The instructions given by the manufacturer
should be followed.
Figure 1 - Accessory for the determination of mercury with tin(ll) chloride (closed system)
4.4.5 100 ml, 200 ml, and 1000 ml volumetric flasks.
4.4.6 1 ml, 5 ml and IO ml pipettes.
NOTE Rather than pipettes, it is advantageous to use a dispensing apparatus, since the risk of introducing trace
contaminants is significantly reduced.
5
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0 IS0
ISO5666:1999(E)
4.5 Sampling and sample pretreatment
Carry out sampling in accordance with IS0 5667-1, IS0 5667-2 and IS0 5667-3.
) or fluoridized ethylene-propylene
Use sampling vessels constructed of borosilicate glass, quartz, polysulfone (PSU
polymerizate (FEP).
mercury by adsorption.
Make sure that the sampling vessel contains no mercury and causes no losses of
In order to limit losses due to, for example, adsorption on the vessel walls, add IO ml of stabilizer solution (4.3.6)
and make up to 1 000 ml with the sample.
Verify that the sample has a pH of approximately 1 and shows a yellow-orange colour, indicating an excess of
dichromate.
If necessary, add additional stabilizer solution, and include the appropriate volume correction factor in the calcula-
tions.
4.6 Digestion method using potassium permanganate/potassium peroxodisulfate
Carry out the wet chemical digestion procedure as follows. Alternatively, use one of the digestion methods indicated
in annex A, B, or C but verify that the efficiency of that method compared to the wet digestion method is equivalent.
Transfer 100 ml of the stabilized (see 4.5) water sample or an appropriate volume (maximum 1 000 ml) of
sample to a flask made of one of the materials listed in 4.5.
Carefully add 15 ml of potassium permanganate solution (4.3.5), 1 ml of nitric acid (4.3.2) and 1 ml of sulfuric
acid (4.3.3).
Shake the mixture well after each addition.
Allow the solution to stand for 15 min, then add 10 ml of potassium peroxodisulfate solution (4.3.7).
Place the loosely stoppered flask on a heating block or water bath and digest at 95 OC for 2 h.
During the digestion, ensure that there is an excess of potassium permanganate. If necessary, increase the
amount of potassium permanganate added or start with a smaller volume of sample.
Allow the solution to cool to room temperature.
If different sample volumes and, accordingly, different reagent volumes have been used, dilute the digests to a
specific volume.
Analyze the digests as soon as possible.
Prepare a reagent blank solution in the same manner, using the corresponding volume of water (4.3.1) with
stabilizer
...
INTERNATIONAL ISO
STANDARD 5666
First edition
1999-05-01
Water quality — Determination of mercury
Qualité de l'eau — Dosage du mercure
A
Reference number
ISO 5666:1999(E)
---------------------- Page: 1 ----------------------
ISO 5666:1999(E)
Contents
1 Scope .1
2 Normative references .1
3 General interferences.1
4 Determination of mercury after tin(II) chloride reduction without enrichment.2
5 Determination of mercury after sodium tetrahydroborate reduction without enrichment.9
6 Precision data .11
Annex A (informative) Ultrasonic digestion method.13
Annex B (informative) Autoclave digestion method.14
Annex C (informative) Microwave digestion method.15
© ISO 1999
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 the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
ii
---------------------- Page: 2 ----------------------
© ISO
ISO 5666:1999(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.
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.
International Standard ISO 5666 was prepared by Technical Committee ISO/TC 147, Water quality,
Subcommittee SC 2, Physical, chemical and biochemical methods.
This first edition cancels and replaces the first editions of ISO 5666-1:1983 and ISO 5666-2:1983, which have been
technically revised.
Annexes A, B and C of this International Standard are for information only.
iii
---------------------- Page: 3 ----------------------
© ISO
ISO 5666:1999(E)
Introduction
In natural water sources, mercury compounds generally occur only in very low concentrations (less than 0,1 μg/l).
Higher concentrations may be found, for example, in waste water. Mercury can accumulate in sediment and sludge.
Both inorganic and organic compounds of mercury may be present.
In order to fully decompose all of the mercury compounds, a digestion procedure is necessary. Digestion can be
omitted only if it is certain that the mercury concentration can be measured without this pretreatment.
For measurements in the low concentration range, highest purity reagents, clean reaction vessels, mercury-free air
in the laboratory and a very stable measurement system are essential. It should be investigated whether, and to
what extent, particular problems will require the specification of additional marginal conditions.
It is absolutely essential that tests conducted according to this International Standard are carried out by suitably
qualified staff.
iv
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INTERNATIONAL STANDARD © ISO ISO 5666:1999(E)
Water quality — Determination of mercury
1 Scope
This International Standard specifies two methods for the determination of mercury in water, for example in ground,
surface and waste waters.
In the method described in clause 4, tin(II) chloride is used as reducing agent. In the method given in clause 5,
sodium tetrahydroborate is used as reducing agent. The choice of the method depends on the equipment available
and the matrix (see clause 3). Both methods are suitable for the determination of mercury in the concentration
range from 0,1 μg/l to 10 μg/l. Higher concentrations can be determined if the water sample is diluted.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard 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 5667-1:1980, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes.
ISO 5667-2:1991, Water quality — Sampling — Part 2: Guidance on sampling techniques.
ISO 5667-3:1994, .
Water quality — Sampling — Part 3: Guidance on the preservation and handling of samples
3 General interferences
With mercury there is a risk that exchange reactions, i.e. adsorption and desorption, will occur on the walls of the
reaction vessel (see 4.4).
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. perfluoro(ethylene-propylene) (FEP) tubes, may be
used. Silicone tubing is unsuitable.
Volatile organic substances can absorb in the UV range and be mistaken for mercury. These are for the most part
removed by adding potassium permanganate until the solution is permanently coloured red and aerating for 10 min
with an inert gas, before reduction of the mercury compounds. Often, such interference by non-specific absorption
can also be eliminated using a background compensation system.
All solutions have to be brought to the same temperature (< 25 °C) before reduction and stripping of the mercury
vapour. Water condensation on the cuvette windows can be prevented by heating the cuvette with, for example, an
infrared lamp.
The interferences which occur due to the presence of other elements in the matrix are dependent on the choice of
reducing agent. Element concentrations in excess of those listed in Table 1 can cause results which are too low.
1
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© ISO
ISO 5666:1999(E)
Fewer interferences from heavy metals arise if tin(II) chloride is used as reducing agent rather than sodium
tetrahydroborate. When using flow systems, interference effects due to heavy metals can be less than indicated in
Table 1.
Table 1 — Acceptable concentrations of some matrix elements in a measurement solution,
in milligrams per litre
Reducing agent NaBH directly NaBH directly SnCl directly
4 4 2
(element)
Medium 0,5 mol/l HCl 5 mol/l HCl 0,5 mol/l HCl
+ 0,2 g/l Fe(III)
Cu(II) 10 10 500
Ni(II) 1 500 500
Ag(I) 0,1 10 1
–
I 100 10 0,1
As(V) 0,5 0,5 0,5
Bi(III) 0,05 0,5 0,5
Sb(III) 0,5 0,5 0,5
Se(IV) 0,005 0,05 0,05
Tin(II) chloride causes such extensive contamination of the apparatus with tin that considerable interferences occur
if sodium tetrahydroborate is used afterwards. Separate systems are therefore essential for reductions with tin(II)
chloride and with sodium tetrahydroborate.
WARNING — Mercury and mercury compounds are very toxic. Extreme caution should be exercised when
handling samples and solutions which contain or may contain mercury.
4 Determination of mercury after tin(II) chloride reduction without enrichment
4.1 Principle
Mono- or divalent mercury is reduced to the elemental form by tin(II) chloride in an acid medium. Elemental mercury
is then stripped from the solution with the aid of a stream of inert gas or mercury-free air and, in the form of an
atomic gas, transported into a cuvette. Absorbances are measured at a wavelength of 253,7 nm in the radiation
beam of an atomic absorption spectrometer. Concentrations are calculated using a calibration curve.
4.2 Interferences
NOTE See also clause 3.
Iodide in concentrations > 0,1 mg/l causes interferences in the determination due to the formation of mercury
complexes. In this case another method such as reduction with sodium tetrahydroborate (see clause 5) is
necessary.
Because of the redox potential of the tin(II) chloride solution, various inorganic mercury compounds, such as
mercury sulfide and organic mercury compounds, cannot be reduced fully without digestion.
2
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© ISO
ISO 5666:1999(E)
4.3 Reagents
4.3.1 General requirements
As a minimum, use "analytical grade" reagents or those with particularly low mercury content. Water shall be
double-distilled or of similar purity. The mercury content of the water and reagents shall be negligible compared to
the lowest analyte concentration.
4.3.2 Nitric acid, r(HNO ) = 1,40 g/ml.
3
4.3.3 Sulfuric acid, r(H SO ) = 1,84 g/ml
2 4
4.3.4 Hydrochloric acid, r(HCl) = 1,16 g/ml
4.3.5 Potassium permanganate solution
Dissolve 50 g of potassium permanganate (KMnO ), in 1 000 ml of water.
4
4.3.6 Stabilizer solution
Dissolve 5 g of potassium dichromate, K Cr O , in 500 ml of nitric acid (see 4.3.2) and dilute to 1000 ml with water.
2 2 7
WARNING — Potassium dichromate is toxic. Caution should be exercised when handling the solid material
or its solutions.
4.3.7 Potassium peroxodisulfate solution
Dissolve 40 g of potassium peroxodisulfate, K S O , in 1 000 ml of water.
2 2 8
4.3.8 Hydroxylammonium chloride solution
Dissolve 10 g of hydroxylammonium chloride, NH OCl, in 100 ml of water.
4
4.3.9 Tin(II) chloride solution
Dissolve 5 g of tin(II)chloride dihydrate, SnCl ⋅2H O, in 30 ml of hydrochloric acid (4.3.4); dilute to 100 ml with
2 2
water. With flow systems, use a solution of lower concentration, e.g. 0,5 g in 100 ml. Prepare this solution fresh
daily from the more concentrated solution by diluting with water.
If a high result for the blank (4.6) is obtained, pass nitrogen through the solution for 30 min in order to remove traces
of mercury.
4.3.10 Mercury stock solution I, r(Hg) = 100 mg/l
Dissolve 108,0 mg of mercury(II) oxide, HgO, in 10 ml of the stabilizer solution (4.3.6); dilute to 1 000 ml with water.
1 ml of this solution corresponds to 0,1 mg of mercury.
It is possible for stock solution I to be prepared from a commercially available mercury standard. This solution is
stable for at least 1 year.
4.3.11 Mercury stock solution II, r(Hg) = 1 mg/l
Add 10 ml of stabilizer solution (4.3.6) to 10 ml of stock solution I (4.3.10) and dilute to 1000 ml with water. 1 ml of
this solution corresponds to 1 μg of mercury.
The solution is stable for about 1 week.
3
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© ISO
ISO 5666:1999(E)
4.3.12 Mercury standard solution (1), r(Hg) = 100 μg/l
Add 10 ml of stabilizer solution (4.3.6) to 100 ml of stock solution II (4.3.11) and dilute to 1 000 ml with water. 1 ml of
this solution corresponds to 100 ng of mercury.
Prepare this solution on the day of use.
4.3.13 Mercury standard solution (2), r(Hg) = 50 μg/l
Add 10 ml of stabilizer solution (4.3.6) to 50 ml of stock solution II (4.3.11) and dilute to 1000 ml with water. 1 ml of
this solution corresponds to 50 ng of mercury.
Prepare this solution on the day of use.
4.3.14 Mercury calibration solutions
Prepare calibration solutions appropriate for the volume and expected mercury concentrations of the measurement
sample solutions:
For the concentration range from 0,5 μg/l to 5 μg/l, for example, proceed as follows.
Pipette into a series of six 100 ml volumetric flasks 1 ml, 2 ml, 4 ml, 6 ml, 8 ml and 10 ml respectively of
mercury standard solution (2) (4.3.13).
Add 1 ml of stabilizer solution (4.3.6) to each 100 ml volumetric flask.
Fill to the mark with water and mix thoroughly.
These calibration solutions contain 0,5 μg/l, 1 μg/l, 2 μg/l, 3 μg/l, 4 μg/l and 5 μg/l mercury respectively. They shall
be prepared freshly before each series of measurements. If calibration measurements shall be done in duplicate
prepare another set of solutions.
4.3.15 Reagent blank solution
Prepare a volume of blank solution corresponding to that of the measurement solution by adding 10 ml of stabilizer
solution (4.3.6) per 1000 ml of water. Use the same digestion procedure as for the sample (4.6). Include the reagent
blank in each batch of analyses.
4.3.16 Rinsing solution for glassware
Add to about 500 ml of water 150 ml of nitric acid (4.3.2) and dilute with water to 1 000 ml.
4.4 Apparatus
4.4.1 General requirement
Before use, all glassware shall be washed thoroughly with dilute nitric acid (4.3.16) and then rinsed thoroughly
several times with water (4.3.1).
4.4.2 Atomic absorption spectrometer with a monitoring system. An instrument with background correction
system is recommended.
for the determination of mercury, e.g. a hollow cathode or electrodeless discharge lamp.
4.4.3 Radiation source
4.4.4 Mercury accessory (see Figure 1), consisting of:
absorption cell comprised of a borosilicate glass or quartz cuvette, of inside diameter about 2 cm, length at
least 15 cm (dependent on the AAS instrument) with quartz end-windows;
4
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© ISO
ISO 5666:1999(E)
air-circulating pump (e.g. membrane pump, peristaltic pump), capacity 1 l/min to 2 l/min, with plastics tubing
(closed system) or inert gas cylinder with pressure-reducing valve (open system);
flow meter with plastics (see clause 3) tubing (open system). An open system is advantageous for high concen-
trations of mercury;
reaction vessel consisting of, for example, a 100 ml, 250 ml or 1 000 ml flat-bottomed flask as shown in the
diagram, with ground glass stopper, wash-bottle insert with glass frit of porosity 1;
heating source for the measuring cell, sufficient to prevent condensation of water.
The temperature of the measuring cell shall be the same throughout the analysis.
An example of a closed system is shown in Figure 1.
Key
1 Absorption cell, i.d. 2 cm; length 15 cm
2 Air circulating pump, of capacity 1 l/min to 2 l/min
3 Ground glass stopper 29/32
4 Reaction flask, capacity 100 ml, 250 ml or 1 000 ml
5 Glass frit
NOTE 1 Care should be taken with regard to the choice of plastics material for pumps and tubing (see clause 3).
NOTE 2 A continuous flow or flow injection system is possible as an alternative. The instructions given by the manufacturer
should be followed.
Figure 1 — Accessory for the determination of mercury with tin(II) chloride (closed system)
4.4.5 100 ml, 200 ml, and 1000 ml volumetric flasks.
4.4.6 1 ml, 5 ml and 10 ml pipettes.
NOTE Rather than pipettes, it is advantageous to use a dispensing apparatus, since the risk of introducing trace
contaminants is significantly reduced.
5
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© ISO
ISO 5666:1999(E)
4.5 Sampling and sample pretreatment
Carry out sampling in accordance with ISO 5667-1, ISO 5667-2 and ISO 5667-3.
Use sampling vessels constructed of borosilicate glass, quartz, polysulfone (PSU) or fluoridized ethylene-propylene
polymerizate (FEP).
Make sure that the sampling vessel contains no mercury and causes no losses of mercury by adsorption.
In order to limit losses due to, for example, adsorption on the vessel walls, add 10 ml of stabilizer solution (4.3.6)
and make up to 1 000 ml with the sample.
Verify that the sample has a pH of approximately 1 and shows a yellow-orange colour, indicating an excess of
dichromate.
If necessary, add additional stabilizer solution, and include the appropriate volume correction factor in the calcula-
tions.
4.6 Digestion method using potassium permanganate/potassium peroxodisulfate
Carry out the wet chemical digestion procedure as follows. Alternatively, use one of the digestion methods indicated
in annex A, B, or C but verify that the efficiency of that method compared to the wet digestion method is equivalent.
Transfer 100 ml of the stabilized (see 4.5) water sample or an appropriate volume (maximum 1 000 ml) of
sample to a flask made of one of the materials listed in 4.5.
Carefully add 15 ml of potassium permanganate solution (4.3.5), 1 ml of nitric acid (4.3.2) and 1 ml of sulfuric
acid (4.3.3).
Shake the mixture well after each addition.
Allow the solution to stand for 15 min, then add 10 ml of potassium peroxodisulfate solution (4.3.7).
Place the loosely stoppered flask on a heating block or water bath and digest at 95 °C for 2 h.
During the digestion, ensure that there is an excess of potassium permanganate. If necessary, increase the
amount of potassium permanganate added or start with a smaller volume of sample.
Allow the solution to cool to room temperature.
If different sample volumes and, accordingly, different reagent volumes have been used, dilute the digests to a
specific volume.
Analyze the digests as soon as possible.
Prepare a reagent blank solution in the same manner, using the corresponding volume of water (4.3.1) with
stabilizer solution (4.3.6) added instead of the water sample.
NOTE Permanganate can cause blank pro
...
SLOVENSKI STANDARD
SIST ISO 5666:2000
01-januar-2000
1DGRPHãþD
SIST ISO 5666-1:1996
SIST ISO 5666-2:1997
SIST ISO 5666-3:1997
.DNRYRVWYRGH±'RORþHYDQMHåLYHJDVUHEUD
Water quality -- Determination of mercury
Qualité de l'eau -- Dosage du mercure
Ta slovenski standard je istoveten z: ISO 5666:1999
ICS:
13.060.50 3UHLVNDYDYRGHQDNHPLþQH Examination of water for
VQRYL chemical substances
SIST ISO 5666:2000 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST ISO 5666:2000
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SIST ISO 5666:2000
INTERNATIONAL ISO
STANDARD 5666
First edition
1999-05-01
Water quality — Determination of mercury
Qualité de l'eau — Dosage du mercure
A
Reference number
ISO 5666:1999(E)
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SIST ISO 5666:2000
ISO 5666:1999(E)
Contents
1 Scope .1
2 Normative references .1
3 General interferences.1
4 Determination of mercury after tin(II) chloride reduction without enrichment.2
5 Determination of mercury after sodium tetrahydroborate reduction without enrichment.9
6 Precision data .11
Annex A (informative) Ultrasonic digestion method.13
Annex B (informative) Autoclave digestion method.14
Annex C (informative) Microwave digestion method.15
© ISO 1999
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 the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
ii
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SIST ISO 5666:2000
© ISO
ISO 5666:1999(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.
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.
International Standard ISO 5666 was prepared by Technical Committee ISO/TC 147, Water quality,
Subcommittee SC 2, Physical, chemical and biochemical methods.
This first edition cancels and replaces the first editions of ISO 5666-1:1983 and ISO 5666-2:1983, which have been
technically revised.
Annexes A, B and C of this International Standard are for information only.
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SIST ISO 5666:2000
© ISO
ISO 5666:1999(E)
Introduction
In natural water sources, mercury compounds generally occur only in very low concentrations (less than 0,1 μg/l).
Higher concentrations may be found, for example, in waste water. Mercury can accumulate in sediment and sludge.
Both inorganic and organic compounds of mercury may be present.
In order to fully decompose all of the mercury compounds, a digestion procedure is necessary. Digestion can be
omitted only if it is certain that the mercury concentration can be measured without this pretreatment.
For measurements in the low concentration range, highest purity reagents, clean reaction vessels, mercury-free air
in the laboratory and a very stable measurement system are essential. It should be investigated whether, and to
what extent, particular problems will require the specification of additional marginal conditions.
It is absolutely essential that tests conducted according to this International Standard are carried out by suitably
qualified staff.
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SIST ISO 5666:2000
INTERNATIONAL STANDARD © ISO ISO 5666:1999(E)
Water quality — Determination of mercury
1 Scope
This International Standard specifies two methods for the determination of mercury in water, for example in ground,
surface and waste waters.
In the method described in clause 4, tin(II) chloride is used as reducing agent. In the method given in clause 5,
sodium tetrahydroborate is used as reducing agent. The choice of the method depends on the equipment available
and the matrix (see clause 3). Both methods are suitable for the determination of mercury in the concentration
range from 0,1 μg/l to 10 μg/l. Higher concentrations can be determined if the water sample is diluted.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard 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 5667-1:1980, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes.
ISO 5667-2:1991, Water quality — Sampling — Part 2: Guidance on sampling techniques.
ISO 5667-3:1994, .
Water quality — Sampling — Part 3: Guidance on the preservation and handling of samples
3 General interferences
With mercury there is a risk that exchange reactions, i.e. adsorption and desorption, will occur on the walls of the
reaction vessel (see 4.4).
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. perfluoro(ethylene-propylene) (FEP) tubes, may be
used. Silicone tubing is unsuitable.
Volatile organic substances can absorb in the UV range and be mistaken for mercury. These are for the most part
removed by adding potassium permanganate until the solution is permanently coloured red and aerating for 10 min
with an inert gas, before reduction of the mercury compounds. Often, such interference by non-specific absorption
can also be eliminated using a background compensation system.
All solutions have to be brought to the same temperature (< 25 °C) before reduction and stripping of the mercury
vapour. Water condensation on the cuvette windows can be prevented by heating the cuvette with, for example, an
infrared lamp.
The interferences which occur due to the presence of other elements in the matrix are dependent on the choice of
reducing agent. Element concentrations in excess of those listed in Table 1 can cause results which are too low.
1
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SIST ISO 5666:2000
© ISO
ISO 5666:1999(E)
Fewer interferences from heavy metals arise if tin(II) chloride is used as reducing agent rather than sodium
tetrahydroborate. When using flow systems, interference effects due to heavy metals can be less than indicated in
Table 1.
Table 1 — Acceptable concentrations of some matrix elements in a measurement solution,
in milligrams per litre
Reducing agent NaBH directly NaBH directly SnCl directly
4 4 2
(element)
Medium 0,5 mol/l HCl 5 mol/l HCl 0,5 mol/l HCl
+ 0,2 g/l Fe(III)
Cu(II) 10 10 500
Ni(II) 1 500 500
Ag(I) 0,1 10 1
–
I 100 10 0,1
As(V) 0,5 0,5 0,5
Bi(III) 0,05 0,5 0,5
Sb(III) 0,5 0,5 0,5
Se(IV) 0,005 0,05 0,05
Tin(II) chloride causes such extensive contamination of the apparatus with tin that considerable interferences occur
if sodium tetrahydroborate is used afterwards. Separate systems are therefore essential for reductions with tin(II)
chloride and with sodium tetrahydroborate.
WARNING — Mercury and mercury compounds are very toxic. Extreme caution should be exercised when
handling samples and solutions which contain or may contain mercury.
4 Determination of mercury after tin(II) chloride reduction without enrichment
4.1 Principle
Mono- or divalent mercury is reduced to the elemental form by tin(II) chloride in an acid medium. Elemental mercury
is then stripped from the solution with the aid of a stream of inert gas or mercury-free air and, in the form of an
atomic gas, transported into a cuvette. Absorbances are measured at a wavelength of 253,7 nm in the radiation
beam of an atomic absorption spectrometer. Concentrations are calculated using a calibration curve.
4.2 Interferences
NOTE See also clause 3.
Iodide in concentrations > 0,1 mg/l causes interferences in the determination due to the formation of mercury
complexes. In this case another method such as reduction with sodium tetrahydroborate (see clause 5) is
necessary.
Because of the redox potential of the tin(II) chloride solution, various inorganic mercury compounds, such as
mercury sulfide and organic mercury compounds, cannot be reduced fully without digestion.
2
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SIST ISO 5666:2000
© ISO
ISO 5666:1999(E)
4.3 Reagents
4.3.1 General requirements
As a minimum, use "analytical grade" reagents or those with particularly low mercury content. Water shall be
double-distilled or of similar purity. The mercury content of the water and reagents shall be negligible compared to
the lowest analyte concentration.
4.3.2 Nitric acid, r(HNO ) = 1,40 g/ml.
3
4.3.3 Sulfuric acid, r(H SO ) = 1,84 g/ml
2 4
4.3.4 Hydrochloric acid, r(HCl) = 1,16 g/ml
4.3.5 Potassium permanganate solution
Dissolve 50 g of potassium permanganate (KMnO ), in 1 000 ml of water.
4
4.3.6 Stabilizer solution
Dissolve 5 g of potassium dichromate, K Cr O , in 500 ml of nitric acid (see 4.3.2) and dilute to 1000 ml with water.
2 2 7
WARNING — Potassium dichromate is toxic. Caution should be exercised when handling the solid material
or its solutions.
4.3.7 Potassium peroxodisulfate solution
Dissolve 40 g of potassium peroxodisulfate, K S O , in 1 000 ml of water.
2 2 8
4.3.8 Hydroxylammonium chloride solution
Dissolve 10 g of hydroxylammonium chloride, NH OCl, in 100 ml of water.
4
4.3.9 Tin(II) chloride solution
Dissolve 5 g of tin(II)chloride dihydrate, SnCl ⋅2H O, in 30 ml of hydrochloric acid (4.3.4); dilute to 100 ml with
2 2
water. With flow systems, use a solution of lower concentration, e.g. 0,5 g in 100 ml. Prepare this solution fresh
daily from the more concentrated solution by diluting with water.
If a high result for the blank (4.6) is obtained, pass nitrogen through the solution for 30 min in order to remove traces
of mercury.
4.3.10 Mercury stock solution I, r(Hg) = 100 mg/l
Dissolve 108,0 mg of mercury(II) oxide, HgO, in 10 ml of the stabilizer solution (4.3.6); dilute to 1 000 ml with water.
1 ml of this solution corresponds to 0,1 mg of mercury.
It is possible for stock solution I to be prepared from a commercially available mercury standard. This solution is
stable for at least 1 year.
4.3.11 Mercury stock solution II, r(Hg) = 1 mg/l
Add 10 ml of stabilizer solution (4.3.6) to 10 ml of stock solution I (4.3.10) and dilute to 1000 ml with water. 1 ml of
this solution corresponds to 1 μg of mercury.
The solution is stable for about 1 week.
3
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SIST ISO 5666:2000
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ISO 5666:1999(E)
4.3.12 Mercury standard solution (1), r(Hg) = 100 μg/l
Add 10 ml of stabilizer solution (4.3.6) to 100 ml of stock solution II (4.3.11) and dilute to 1 000 ml with water. 1 ml of
this solution corresponds to 100 ng of mercury.
Prepare this solution on the day of use.
4.3.13 Mercury standard solution (2), r(Hg) = 50 μg/l
Add 10 ml of stabilizer solution (4.3.6) to 50 ml of stock solution II (4.3.11) and dilute to 1000 ml with water. 1 ml of
this solution corresponds to 50 ng of mercury.
Prepare this solution on the day of use.
4.3.14 Mercury calibration solutions
Prepare calibration solutions appropriate for the volume and expected mercury concentrations of the measurement
sample solutions:
For the concentration range from 0,5 μg/l to 5 μg/l, for example, proceed as follows.
Pipette into a series of six 100 ml volumetric flasks 1 ml, 2 ml, 4 ml, 6 ml, 8 ml and 10 ml respectively of
mercury standard solution (2) (4.3.13).
Add 1 ml of stabilizer solution (4.3.6) to each 100 ml volumetric flask.
Fill to the mark with water and mix thoroughly.
These calibration solutions contain 0,5 μg/l, 1 μg/l, 2 μg/l, 3 μg/l, 4 μg/l and 5 μg/l mercury respectively. They shall
be prepared freshly before each series of measurements. If calibration measurements shall be done in duplicate
prepare another set of solutions.
4.3.15 Reagent blank solution
Prepare a volume of blank solution corresponding to that of the measurement solution by adding 10 ml of stabilizer
solution (4.3.6) per 1000 ml of water. Use the same digestion procedure as for the sample (4.6). Include the reagent
blank in each batch of analyses.
4.3.16 Rinsing solution for glassware
Add to about 500 ml of water 150 ml of nitric acid (4.3.2) and dilute with water to 1 000 ml.
4.4 Apparatus
4.4.1 General requirement
Before use, all glassware shall be washed thoroughly with dilute nitric acid (4.3.16) and then rinsed thoroughly
several times with water (4.3.1).
4.4.2 Atomic absorption spectrometer with a monitoring system. An instrument with background correction
system is recommended.
for the determination of mercury, e.g. a hollow cathode or electrodeless discharge lamp.
4.4.3 Radiation source
4.4.4 Mercury accessory (see Figure 1), consisting of:
absorption cell comprised of a borosilicate glass or quartz cuvette, of inside diameter about 2 cm, length at
least 15 cm (dependent on the AAS instrument) with quartz end-windows;
4
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SIST ISO 5666:2000
© ISO
ISO 5666:1999(E)
air-circulating pump (e.g. membrane pump, peristaltic pump), capacity 1 l/min to 2 l/min, with plastics tubing
(closed system) or inert gas cylinder with pressure-reducing valve (open system);
flow meter with plastics (see clause 3) tubing (open system). An open system is advantageous for high concen-
trations of mercury;
reaction vessel consisting of, for example, a 100 ml, 250 ml or 1 000 ml flat-bottomed flask as shown in the
diagram, with ground glass stopper, wash-bottle insert with glass frit of porosity 1;
heating source for the measuring cell, sufficient to prevent condensation of water.
The temperature of the measuring cell shall be the same throughout the analysis.
An example of a closed system is shown in Figure 1.
Key
1 Absorption cell, i.d. 2 cm; length 15 cm
2 Air circulating pump, of capacity 1 l/min to 2 l/min
3 Ground glass stopper 29/32
4 Reaction flask, capacity 100 ml, 250 ml or 1 000 ml
5 Glass frit
NOTE 1 Care should be taken with regard to the choice of plastics material for pumps and tubing (see clause 3).
NOTE 2 A continuous flow or flow injection system is possible as an alternative. The instructions given by the manufacturer
should be followed.
Figure 1 — Accessory for the determination of mercury with tin(II) chloride (closed system)
4.4.5 100 ml, 200 ml, and 1000 ml volumetric flasks.
4.4.6 1 ml, 5 ml and 10 ml pipettes.
NOTE Rather than pipettes, it is advantageous to use a dispensing apparatus, since the risk of introducing trace
contaminants is significantly reduced.
5
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SIST ISO 5666:2000
© ISO
ISO 5666:1999(E)
4.5 Sampling and sample pretreatment
Carry out sampling in accordance with ISO 5667-1, ISO 5667-2 and ISO 5667-3.
Use sampling vessels constructed of borosilicate glass, quartz, polysulfone (PSU) or fluoridized ethylene-propylene
polymerizate (FEP).
Make sure that the sampling vessel contains no mercury and causes no losses of mercury by adsorption.
In order to limit losses due to, for example, adsorption on the vessel walls, add 10 ml of stabilizer solution (4.3.6)
and make up to 1 000 ml with the sample.
Verify that the sample has a pH of approximately 1 and shows a yellow-orange colour, indicating an excess of
dichromate.
If necessary, add additional stabilizer solution, and include the appropriate volume correction factor in the calcula-
tions.
4.6 Digestion method using potassium permanganate/potassium peroxodisulfate
Carry out the wet chemical digestion procedure as follows. Alternatively, use one of the digestion methods indicated
in annex A, B, or C but verify that the efficiency of that method compared to the wet digestion method is equivalent.
Transfer 100 ml of the stabilized (see 4.5) water sample or an appropriate volume (maximum 1 000 ml) of
sample to a flask made of one of the materials listed in 4.5.
Carefully add 15 ml of potassium permanganate solution (4.3.5), 1 ml of nitric acid (4.3.2) and 1 ml of sulfuric
acid (4.3.3).
Shake the mixture well after each addition.
Allow the solution to stand for 15 min, then add 10 ml of potassium peroxodisulfate solution (4.3.7).
Place the loosely stoppered flask on a heating block or water bath and digest at 95 °C for 2 h.
During the digestion, ensure that there is an excess of potassium permanganate. If necessary, increase the
amount of potassium permanganate added or start with a smaller volume of sample.
Allow the solution to cool to room tempe
...
NORME ISO
INTERNATIONALE 5666
Première édition
1999-05-01
Qualité de l'eau — Dosage du mercure
Water quality — Determination of mercury
A
Numéro de référence
ISO 5666:1999(F)
---------------------- Page: 1 ----------------------
ISO 5666:1999(F)
Sommaire
1 Domaine d’application .1
2 Références normatives .1
3 Interférences générales.1
4 Dosage du mercure après réduction par le chlorure d'étain(II) sans enrichissement.2
5 Dosage du mercure après réduction par le tétrahydroborate de sodium sans enrichissement.9
6 Données de fidélité.12
Annexe A (informative) Méthode de digestion par ultrasons .13
Annexe B (informative) Méthode de digestion avec un autoclave .14
Annexe C (informative) Méthode de digestion par micro-ondes.15
© ISO 1999
Droits de reproduction réservés. Sauf prescription différente, aucune partie de cette publication ne peut être reproduite ni utilisée sous quelque
forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie et les microfilms, sans l'accord écrit de l'éditeur.
Organisation internationale de normalisation
Case postale 56 • CH-1211 Genève 20 • Suisse
Internet iso@iso.ch
Imprimé en Suisse
ii
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© ISO
ISO 5666:1999(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 (CEI) en ce qui concerne la normalisation électrotechnique.
Les Normes internationales sont rédigées conformément aux règles données dans les Directives ISO/CEI, Partie 3.
Les projets de Normes internationales adoptés par les comités techniques sont soumis aux comités membres pour
vote. Leur publication comme Normes internationales requiert l'approbation de 75 % au moins des comités
membres votants.
La Norme internationale ISO 5666 a été élaborée par le comité technique ISO/TC 147, Qualité de l’eau, sous-
comité SC 2, Méthodes physiques, chimiques et biochimiques.
Cette première édition annule et remplace les premières éditions de l'ISO 5666-1:1983 et de l'ISO 5666-2:1983,
dont elle constitue une révision technique.
Les annexes A, B et C de la présente Norme internationale sont données uniquement à titre d’information.
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© ISO
ISO 5666:1999(F)
Introduction
Dans les eaux naturelles, les composés du mercure n'existent généralement qu'en faibles concentrations (moins de
0,1 μg/l). Des concentrations plus élevées peuvent apparaître, par exemple dans les eaux usées. Le mercure peut
s'accumuler dans les sédiments et dans les boues. Des composés inorganiques et organiques du mercure peuvent
être présents.
Pour décomposer le plus complètement les composés du mercure, une procédure de digestion est nécessaire. On
ne peut renoncer à une telle procédure que si la concentration en mercure peut être mesurée sans ce
prétraitement.
Pour les mesurages dans une gamme de faibles concentrations, il est essentiel que les réactifs soient d'une pureté
maximale, les récipients de réaction propres, l'air du laboratoire exempt de mercure et le système de mesurage très
stable. Il convient de rechercher dans quelle mesure des problèmes particuliers nécessiteront des spécifications de
conditions particulières supplémentaires.
Il est essentiel que les essais conduits selon la présente Norme internationale soient effectués par un personnel
convenablement qualifié.
iv
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NORME INTERNATIONALE © ISO ISO 5666:1999(F)
Qualité de l'eau — Dosage du mercure
1 Domaine d’application
La présente Norme internationale spécifie deux méthodes pour le dosage du mercure, par exemple dans les eaux
souterraines, dans les eaux de surface et dans les eaux usées.
Dans la méthode décrite à l'article 4, le chlorure d'étain(II) est utilisé comme agent réducteur. Dans la méthode
décrite à l'article 5, le tétrahydroborate de sodium est utilisé comme agent réducteur. Le choix de la méthode
dépend de l'équipement disponible et de la matrice (voir l'article 3). Les deux méthodes conviennent pour le dosage
du mercure dans l'eau, dans une gamme de concentrations de 0,1 μg/l à 10 μg/l. Des concentrations plus élevées
peuvent être déterminées si l'échantillon d'eau est dilué.
2 Références normatives
Les documents normatifs suivants contiennent des dispositions qui, par suite de la référence qui y est faite,
constituent des dispositions valables pour la présente Norme internationale. Pour les références datées, les
amendements ultérieurs ou les révisions de ces publications ne s'appliquent pas. Toutefois, les parties prenantes
aux accords fondés sur la présente Norme internationale sont invitées à rechercher la possibilité d’appliquer les
éditions les plus récentes des documents normatifs indiqués ci-après. Pour les références non datées, la dernière
édition du document normatif en référence s'applique. Les membres de l’ISO et de la CEI possèdent le registre des
Normes internationales en vigueur.
ISO 5667-1:1993, Qualité de l'eau — Échantillonnage — Partie 1: Guide général pour l'etablissement des
programmes d'échantillonnage.
ISO 5667-2:1991, Qualité de l'eau — Échantillonnage — Partie 2: Guide général sur les techniques
d'échantillonnage.
ISO 5667-3:1994, Qualité de l'eau — Échantillonnage — Partie 3: Guide général pour la conservation et la
manipulation des échantillons.
3 Interférences générales
Lors de l'analyse du mercure, il existe un risque de réactions d'échange, c'est-à-dire d'adsorption et de désorption
se produisant sur les parois du récipient de réaction (voir 4.4).
La vapeur de mercure peut diffuser à travers différentes matières plastiques. Ce phénomène nécessite d'être pris
en considération lors du choix du matériau des tubes. Des tubes en verre ou en matière plastique spéciale, par
exemple les tuyaux en FEP (FEP = copolymère éthylène-propylène fluoré), peuvent être utilisés. Les tubes en
silicone ne conviennent pas.
Des substances organiques volatiles peuvent absorber dans le domaine UV et peuvent être prises pour du
mercure. Ces substances sont, pour la plupart, éliminées par ajout de permanganate de potassium jusqu'à
coloration persistante rouge de la solution et aération pendant 10 min au moyen d'un gaz inerte avant la réduction
des composés du mercure. Souvent, une telle absorption non spécifique peut également être éliminée par un
système de compensation de fond.
1
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© ISO
ISO 5666:1999(F)
Toutes les solutions doivent être amenées à la même température (< 25 °C) avant la réduction et le dégagement de
la vapeur de mercure. La condensation d'eau sur les fenêtres de la cuve peut être évitée par chauffage de la cuve,
par exemple avec une lampe à infrarouge.
Les interférences dues à la présence d'autres éléments dans la matrice dépendent du choix de l'agent réducteur.
Des concentrations d'éléments supérieures à celles figurant dans le Tableau 1 peuvent entraîner des résultats trop
faibles.
Les interférences dues aux métaux lourds sont limitées si le chlorure d'étain(II) est utilisé comme agent réducteur à
la place du tétrahydroborate de sodium. En utilisant des systèmes en flux, les effets des interférences dues aux
métaux lourds peuvent être inférieures à celles indiquées dans le Tableau 1.
Tableau 1 — Concentrations acceptables de certains éléments de la matrice dans une solution de mesure,
en milligrammes par litre
Agent réducteur NaBH NaBH SnCl
4 4 2
(élément)
directe directe directe
Milieu 0,5 mol/l HCl 5 mol/l HCl 0,5 mol/l HCl
+ 0,2 g/l Fe(III)
Cu(II) 10 10 500
Ni(II) 1 500 500
Ag(I) 0,1 10 1
-
I 100 10 0,1
As(V) 0,5 0,5 0,5
Bi(III) 0,05 0,5 0,5
Sb(III) 0,5 0,5 0,5
Se(IV) 0,005 0,05 0,05
L'utilisation de chlorure d'étain(II) entraîne une contamination par l'étain telle que des interférences importantes
peuvent se produire si l'on utilise ensuite le tétrahydroborate de sodium. Pour cette raison, il est essentiel d'utiliser
des systèmes séparés pour la réduction avec le chlorure d'étain(II) et avec le tétrahydro-borate de sodium.
AVERTISSEMENT — Le mercure et les composés du mercure sont très toxiques. Il convient de prendre des
précautions appropriées lors de la manipulation des échantillons et des solutions contenant ou pouvant
contenir du mercure.
4 Dosage du mercure après réduction par le chlorure d'étain(II) sans enrichissement
4.1 Principe
Le mercure monovalent ou divalent est réduit à sa forme élémentaire par le chlorure d'étain(II) en milieu acide. Le
mercure élémentaire est ensuite dégagé de la solution à l'aide d'un courant de gaz inerte ou d'air exempt de
mercure et transporté sous forme de gaz atomique dans une cuve de mesure. Les absorbances sont mesurées à la
longueur d'onde de 253,7 nm dans le faisceau optique d'un spectromètre d'absorption atomique. Les concentrations
sont calculées à l'aide d'une courbe d'étalonnage.
4.2 Interférences
NOTE Voir également l'article 3.
Les concentrations en iodure > 0,1 mg/l provoquent des interférences lors du dosage, par la formation de
complexes de mercure. Dans ce cas, il est nécessaire d'utiliser une autre méthode, telle que la réduction par le
tétrahydroborate de sodium (voir l'article 5).
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En raison du potentiel redox de la solution de chlorure d'étain(II), de nombreux composés inorganiques du mercure
tels que le sulfure de mercure et des composés organiques du mercure ne peuvent être réduits entièrement sans
digestion préalable.
4.3 Réactifs
4.3.1 Exigences générales
Utiliser au minimum des réactifs de «qualité analytique» ou de teneur particulièrement faible en mercure. L'eau doit
être bidistillée ou de pureté équivalente. La teneur en mercure de l'eau et des réactifs doit être négligeable
comparée à la plus faible concentration à déterminer.
4.3.2 Acide nitrique, r(HNO ) = 1,40 g/ml.
3
4.3.3 Acide sulfurique, r(H SO ) = 1,84 g/ml.
2 4
4.3.4 Acide chlorhydrique, r(HCl) = 1,16 g/ml.
4.3.5 Solution de permanganate de potassium
Dissoudre 50 g de permanganate de potassium, KMnO , dans 1 000 ml d'eau.
4
4.3.6 Agent stabilisant
Dissoudre 5 g de dichromate de potassium, K Cr O , dans 500 ml d'acide nitrique (4.3.2) et diluer la solution avec
2 2 7
de l'eau à 1 000 ml.
AVERTISSEMENT — Le dichromate de potassium est toxique. Il convient de prendre des précautions
appropriées lors de la manipulation de la matière solide ou de ses solutions.
4.3.7 Solution de peroxodisulfate de potassium
Dissoudre 40 g de peroxodisulfate de potassium, K S O , dans 1 000 ml d'eau.
2 2 8
4.3.8 Solution de chlorure d'hydroxylammonium
Dissoudre 10 g de chlorure d' hydroxylammonium, NH OCl, dans 100 ml d'eau.
4
4.3.9 Solution de chlorure d'étain(II)
Dissoudre 5 g de chlorure d'étain(II) dihydraté, SnCl ,2H O, dans 30 ml d'acide chlorhydrique (4.3.4); diluer à
2 2
100 ml avec de l'eau. Avec des systèmes en flux, utiliser une solution moins concentrée, par exemple 0,5 g dans
100 ml. Préparer cette solution fraîchement chaque jour par dilution de la solution la plus concentrée avec de l'eau.
Si on obtient une valeur à blanc élevée (voir 4.6), purger la solution à l'azote pendant 30 min afin d'éliminer les
traces de mercure.
4.3.10 Solution mère I de mercure, r(Hg) = 100 mg/l
Dissoudre 108,0 g d'oxyde de mercure(II), HgO, dans 10 ml d'agent stabilisant (4.3.6). Diluer avec de l'eau à
1 000 ml. 1 ml de cette solution correspond à 0,1 mg de mercure.
La solution mère I peut aussi être préparée à partir d'une solution étalon disponible dans le commerce. Cette
solution se conserve pendant au moins 1 an.
4.3.11 Solution mère II de mercure, r(Hg) = 1 mg/l
Ajouter 10 ml de l'agent stabilisant (4.3.6) à 10 ml de solution mère I (4.3.10) et diluer à 1 000 ml avec de l'eau. 1 ml
de cette solution correspond à 1 μg de mercure.
Cette solution se conserve environ 1 semaine.
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4.3.12 Solution étalon de mercure (1), r(Hg) = 100 μg/l
Ajouter 10 ml de l'agent stabilisant (4.3.6) à 100 ml de la solution mère II (4.3.11) et diluer avec de l'eau à 1 000 ml.
1 ml de cette solution correspond à 100 ng de mercure.
Préparer cette solution le jour de son utilisation.
4.3.13 Solution étalon de mercure (2), r(Hg) = 50 μg/l
Ajouter 10 ml de l'agent stabilisant (4.3.6) à 50 ml de la solution mère II (4.3.11) et diluer avec de l'eau à 1 000 ml.
1 ml de cette solution correspond à 50 ng de mercure.
Préparer cette solution le jour de son utilisation.
4.3.14 Solutions de mercure pour l'étalonnage
Préparer des solutions d'étalonnage appropriées au volume et aux concentrations en mercure attendues dans les
solutions de mesure.
Pour la gamme de concentration de 0,5 μg/l à 5 μg/l, opérer, par exemple, comme suit.
Dans une série de six fioles jaugées de 100 ml, introduire, à l'aide d'une pipette, 1 ml, 2 ml, 4 ml, 6 ml, 8 ml et
10 ml de la solution étalon de mercure (2) (4.3.13).
À chaque fiole jaugée de 100 ml, ajouter 1 ml d'agent stabilisant (4.3.6).
Compléter jusqu'au trait avec de l'eau et mélanger soigneusement.
Ces solutions d'étalonnage contiennent respectivement 0,5 μg/l, 1 μg/l, 2 μg/l, 3 μg/l, 4 μg/l et 5 μg/l de mercure.
Elles doivent être fraîchement préparées avant chaque série de mesures. Si les mesurages d'étalonnage doivent
être faits en double, préparer une nouvelle série de solutions.
4.3.15 Solution du blanc réactif
Préparer un volume de la solution de blanc correspondant à celui de la solution de mesure en ajoutant 10 ml de
l'agent stabilisant (4.3.6) pour 1 000 ml d'eau. Utiliser le même procédé de digestion que pour l'échantillon (voir
4.6). Inclure le blanc réactif dans chaque série d'analyses.
4.3.16 Solution pour rincage de la verrerie
Ajouter à environ 500 ml d'eau, 150 ml d'acide nitrique (4.3.2) et diluer avec de l'eau à 1 000 ml.
4.4 Appareillage
4.4.1 Exigences générales
Avant utilisation, la verrerie doit être soigneusement lavée avec de l'acide nitrique dilué (4.3.16) et rincée ensuite
plusieurs fois avec de l'eau (4.3.1).
4.4.2 Spectromètre d'absorption atomique, muni d'un système d'enregistrement. L'emploi d'un instrument avec
correction de l'absorption non spécifique est recommandé.
4.4.3 Source de rayonnement pour le dosage du mercure, par exemple une lampe à cathode creuse ou une
lampe à décharge sans électrode.
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4.4.4 Dispositifs complémentaires (voir Figure 1), comportant:
une cellule d'absorption constituée par une cuve en verre borosilicaté ou en quartz, de diamètre interne
d'environ 2 cm et d'au moins 15 cm de longueur (en fonction de l'appareil de spectrométrie d'absorption
atomique) avec des fenêtres optiques en quartz;
une pompe de circulation d'air (par exemple pompe à membrane, pompe péristaltique), de débit 1 l/min à
2 l/min, avec tubes en plastique (système fermé) ou bouteille de gaz inerte équipée d'un dispositif de réduction
de la pression (système ouvert);
un débitmètre avec tubes en plastique (voir l'article 3) (système ouvert); un système ouvert est avantageux
pour les concentrations élevées en mercure;
récipients de réaction constitués, par exemple, de ballons à fond plat de 100 ml, 250 ml ou 1 000 ml, comme
indiqué sur le schéma, munis de bouchons en verre rodé et d'un flacon laveur avec verre fritté de porosité 1;
une source de chauffage pour la cellule de mesure, de façon à prévenir la condensation de l'eau.
La température de la cellule de mesure doit rester stable pendant toute l'analyse.
Un exemple de système fermé est indiqué à la Figure 1.
NOTE 1 Il convient de veiller au choix des matériaux plastiques des pompes et des tubes (voir l'article 3).
NOTE 2 Un système à flux continu ou flux injecté peut également être utilisé. Il convient de suivre les instructions du
fabricant.
Légende
1 Cellule d'absorption (diamètre interne 2 cm; longueur 15 cm)
2 Pompe de circulation d'air (débit 1 l/min à 2 l/min)
3 Bouchon en verre rodé 29/32
4 Flacon de réaction (100 ml, 250 ml ou 1 000 ml)
5 Verre fritté
Figure 1 — Dispositif pour le dosage du mercure avec le chlorure d'étain(II) (système fermé)
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4.4.5 Fioles jaugées de 100 ml, 200 ml et 1 000 ml.
4.4.6 Pipettes de 1 ml, 5 ml et 10 ml.
NOTE Plutôt que des pipettes, il est avantageux d'utiliser des distributeurs volumétriques, car le risque d'introduire des
impuretés est significativement réduit.
4.5 Échantillonnage et prétraitement de l'échantillon
Effectuer l'échantillonnage selon l'ISO 5667-1, l'ISO 5667-2 et l'ISO 5667-3.
Utiliser des récipients d'échantillonnage en verre borosilicaté, quartz, polysulfone (PSF) ou polymère éthylène-
propylène fluoré (FEP).
S'assurer que le récipient échantillonnage ne contient pas de mercure et ne conduit pas à des pertes de mercure
par adsorption.
Afin de limiter les pertes, par exemple, par adsorption sur les parois du récipient, ajouter 10 ml d'agent stabilisant
(4.3.6) dans le récipient et compléter à 1 000 ml avec l'échantillon.
Vérifier que l'échantillon a un pH d'environ 1 et présente une coloration jaune-orangée indiquant un excès de
dichromate.
Si nécessaire, ajouter une quantité supplémentaire d'agent stabilisant et inclure le facteur de correction approprié
dans les calculs.
4.6 Méthode de digestion utilisant le permanganate de potassium/peroxodisulfate de potassium
Appliquer la méthode de digestion chimique par voie humide décrite ci-après. Il est également possible d'utiliser
l'une des méthodes de digestion décrites aux annexes A, B et C, mais vérifier que l'efficacité de cette méthode
comparée à la méthode de digestion par voie humide est équivalente.
Transvaser 100 ml de l'échantillon d'eau stabilisé (voir 4.5) ou un volume approprié (1 000 ml maximum) de
l'échantillon dans un ballon constitué de l'un des matériaux cités en 4.5.
Ajouter soigneusement 15 ml de solution de permanganate de potassium (4.3.5), 1 ml d'acide nitrique (4.3.2) et
1 ml d'acide sulfurique (4.3.3).
Bien agiter la solution après chaque ajout.
Laisser reposer la solution pendant 15 min, puis ajouter 10 ml de solution de peroxodisulfate de potassium
(4.3.7).
Placer le ballon avec le bouchon non complètement fermé sur un bloc chauffant ou dans un bain-marie et
procéder à la digestion pendant 2 h à 95 °C.
Pendant la digestion, s'assurer qu'il y a un excès de permanganate de potassium. Si nécessaire, augmenter la
quantité de permanganate de potassium ou recommencer avec un volume d'échantillon plus faible.
Laisser refroidir la solution à température ambiante.
Si l'on a utilisé des volumes d'échantillon différents et, par conséquent, des volumes de réactifs différents,
diluer les solutions de digestion à un volume défini.
Analyser ces solutions le plus rapidement possible.
Préparer de manière analogue une solution du blanc réactif, en ajoutant, à la place de l'échantillon d'eau à
analyser, le volume d'eau correspondant (4.3.1) et l'agent stabilisant (4.3.6).
NOTE Le permanganate peut provoquer des problèmes de blanc. Dans ce cas, il convient de réduire la concentration
...
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