ISO/TR 19588:2017
(Main)Background information and guidance on environmental cyanide analysis
Background information and guidance on environmental cyanide analysis
ISO/TR 19588:2017 provides background information on the various International (ISO), American (ASTM, EPA), and European (CEN) cyanide methods for soils, waters, effluents and wastes. It gives guidance on how to carry out fit for purpose analysis of various forms of cyanide in environmental samples, the significance of the results, how to minimize interference effects and the preservation of samples. Some information is also provided on other national and international cyanide methods.
Informations et lignes directrices sur l'analyse environnementale du cyanure
General Information
Standards Content (Sample)
TECHNICAL ISO/TR
REPORT 19588
First edition
2017-07
Background information and guidance
on environmental cyanide analysis
Informations et lignes directrices sur l’analyse environnementale
du cyanure
Reference number
ISO/TR 19588:2017(E)
©
ISO 2017
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ISO/TR 19588:2017(E)
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ISO/TR 19588:2017(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Cyanide methods for soil, water, effluents and wastes considered for this document .2
5 Summary of cyanide species and degradation products . 3
5.1 Main cyanide species . 3
5.1.1 Free cyanide . 3
5.1.2 Simple (weakly complexed) cyanides . 3
5.1.3 Strongly complexed cyanides . 4
5.2 Cyanide degradation products . 4
5.2.1 Cyanogen halides . 4
5.2.2 Thiocyanate (SCN) . 4
5.2.3 Organic cyanides . 4
-
5.2.4 Cyanates (CNO ) . 4
5.2.5 Cyanide environmental fate and degradation potential . 5
6 Information on cyanide analysis parameters to determine various cyanide species
(see also Annex B) . 5
6.1 General . 5
6.2 Free cyanide. 6
6.3 Liberatable Cyanide . 6
6.3.1 General. 6
6.3.2 Easily liberatable cyanide (ELC) . 6
6.3.3 Free cyanide (or alternatively: easily liberatable cyanide) . 6
6.3.4 Weak acid dissociable (WAD) cyanide . 6
6.4 Total cyanide . 6
6.5 Cyanide amenable to chlorination . 7
7 Current ISO/CEN environmental cyanide standards (see also Annex C) .7
7.1 Water . 7
7.1.1 ISO 6703 . 7
7.1.2 ISO 17690 . 7
7.1.3 ISO 14403-1 . 8
7.1.4 ISO 14403-2 . 8
7.2 Soil . 9
7.2.1 ISO 11262 . 9
7.2.2 ISO 17380 . 9
7.3 Waste (Slurries) . 9
7.3.1 CEN/TS 16229 . 9
7.4 Concluding remark .10
8 Other national and international cyanide standards, methodologies and guides .10
8.1 General .10
8.2 USEPA Method Kelada-01: Kelada automated test methods for total cyanide, acid
dissociable cyanide, and thiocyanate, Revision 1.2 (2001) .10
8.3 USEPA Method 335.4 Determination of total cyanide by semi-automated
colorimetry, Revision 1.0 (August 1993) . .11
8.4 USEPA Method 9012b Total and amenable cyanide (Automated colorimetric, with
off-line distillation), Revision 2 (Nov 2004, Rev 2) .11
8.5 USEPA Method 9010C Total and amenable cyanide: Distillation (Nov 2004, Rev 3) .11
8.6 USGS I-2302/I-4302/I-6302 Cyanide, calorimetric, barbituric acid, automated-
segmented flow (1989) .11
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ISO/TR 19588:2017(E)
8.7 EPA/OIA-1677-09 Available cyanide by flow injection, ligand exchange,
and amperometry .12
8.8 ASTM International methods .12
8.9 The Picric acid method for determining weak acid dissociable (WAD) cyanide .12
8.10 Standard methods for the examination of water and wastewater standard
-
methods 4500-CN cyanide (1999) .13
8.11 The determination of cyanide and thiocyanate in soils and similar matrices
(2011). Methods for the examination of waters and associated materials, standing
committee of analysts, 2011 (Method 235) .14
8.12 The determination of cyanide in waters and associated materials (2007) Methods
for the Examination of Waters and Associated Materials, Standing Committee of
Analysts, 2011 (Method 214) .15
8.13 The Direct Determination of Metal Cyanides by Ion Chromatography with UV
[23]-[28] 15
Absorbance Detection .
9 Sample preservation and interferences .16
9.1 Sample preservation .16
9.1.1 ISO 5667-3 .16
9.1.2 ISO 17690 .17
9.1.3 Other cyanide methods .17
9.2 Interferences .18
10 Conclusions .19
Annex A (informative) Summary of cyanide terms and definitions .20
Annex B (informative) Summary of cyanide analytical methods .23
Annex C (informative) Summary of the methodology scopes and performance
characteristics of the ISO/CEN cyanide standards .28
Annex D (informative) Summary of ASTM international cyanide methods .37
Annex E (informative) Summary of potential cyanide method interference effects .42
Bibliography .46
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ISO/TR 19588:2017(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee SC 3,
Chemical methods and soil characteristics, in cooperation with ISO/TC 147, Water quality.
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ISO/TR 19588:2017(E)
Introduction
Cyanide is a useful industrial chemical and its key role in the mining industry is to extract gold from its
ores. Worldwide, mining uses approximately 13 % of the total production of manufactured hydrogen
cyanide while the remaining 87 % is used in many other industrial processes, apart from mining. In
manufacturing, cyanide is used to make paper, textiles, and plastics. It is present in the chemicals used
to develop photographs. Cyanide salts are used in metallurgy for electroplating, metal cleaning, and
removing gold from its ore. Cyanide gas (HCN) is used to exterminate pests and vermin in ships and
buildings.
There is a large number of “official national and international methods” for the analysis of various
cyanide parameters for waters, effluents, leachates, soils and wastes. This document attempts to
provide background information and guidance on environmental cyanide analysis.
Cyanide can exist in many chemical forms (cyanide species) with various toxicity levels for a given mass
-
of CN. Highest toxicity has free cyanide appearing as HCN or CN .
Hydrogen cyanide is a colourless, poisonous gas having an odour of bitter almonds (mp = −13,4 °C,
-
bp = 25,6 °C, pKa = 9,36). It is readily soluble in water existing as HCN or CN , or both, depending on
the pH conditions (Figure 1). At a pH of 7 or less in water, free cyanide is effectively present entirely as
-
HCN; at pH 11 or greater, free cyanide is effectively present entirely as CN .
Figure 1 — Dissociation degree (%) of hydrocyanic acid (HCN) with pH
Owing to its high toxicity at low concentrations (especially to fish), “free or bioavailable cyanide” is
[1]-[7]
regulated in environmental wastewater discharges and in drinking waters . Cyanide is regarded
as an acute rather than a chronic toxin as low levels can be metabolised. It does not bioaccumulate. The
sensitivity of aquatic life to available cyanide varies with the species present and the characteristics
of the water matrix. Fish and aquatic invertebrates are particularly sensitive to bioavailable cyanide
exposure.
[6]
It is worth noting that the WHO guideline limit for cyanide in drinking water is 70 µg/l. An allocation
of 20 % of the tolerable daily intake (TDI) to drinking water is made because exposure to cyanide from
other sources is normally small and because exposure from water is only intermittent. This results in
the guideline value of 70 µg/l which is considered to be protective for both acute and long-term human
exposure.
Hydrogen cyanide and many complexed cyanides are readily soluble in water. An overview of solubilities
in water is given in Table 1.
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ISO/TR 19588:2017(E)
[32]
Table 1 — Solubility of cyanides in water
Solubility Temperature
Species
g/l °C
Alkaline cyanides
LiCN very high unknown
NaCN 583 20
KCN 716 25
RbCN very high unknown
CsCN very high unknown
Alkaline earth cyanides
Mg(CN) unstable
2
Ca(CN) unstable
2
Sr(CN) 4H O very high unknown
2 2
Ba(CN) very high unknown
2
Heavy metal cyanides
−5
AgCN 2,8 × 10 18
AuCN almost insoluble unknown
Pt(CN) almost insoluble unknown
2
Co(CN) 2H O almost insoluble unknown
2 2
−3
Zn(CN) 5,8 × 10 18
2
CuCN 0,014 20
Ni(CN) 4H O 0,0 592 18
2 2
Cd(CN) 17 15
2
Hg(CN) 93 14
2
Pb(CN) high unknown
2
Pd(CN) high unknown
2
Therefore, the majority of methods are on the analysis of soluble cyanides in water, mainly to protect
the environment from toxic effects.
The toxicity of a metal cyanide complex is associated with its stability constant because the more easily
dissociated cyanide species will release cyanide more readily into the environment. The more stable
metal cyanide complexes are less likely to release cyanide into the environment.
The stability constants of the various relevant cyanide species is given in Table 2. Any complex with
a log K > about 35 is regarded as a strong complex, with lower relative toxicity, and will generally
10
only be detected when using a total cyanide method, often without quantitative recovery of the strong
complexes. There are method recovery problems of strong complexes in most total cyanide methods.
Nickel and copper cyanide complexes are considered to be in the weak acid dissociable (WAD) category
due to greater relative toxicity.
Table 2 — Stability constants (log K at 25 °C) of relevant metal cyanide complexes
10
Metal cyanide
Stability constant Weak or strong complex Reference
complex
(log K at 25 °C) (Strong log K > 30)
10 10
2-
[Cd(CN) ] 17,9 Weak [10]
4
2-
[Zn(CN) ] 19,6 Weak [10]
4
–
[Ag(CN) ] 20,5 Weak [10]
2
3-
[Cu(CN) ] 23,1 Weak [10]
4
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ISO/TR 19588:2017(E)
Table 2 (continued)
Metal cyanide
Stability constant Weak or strong complex Reference
complex
(log K at 25 °C) (Strong log K > 30)
10 10
2-
[Ni(CN) ] 30,2 Weak [10]
4
Hg(CN) 32,8 Weak and dissociable ASTM D 6696
2
4-
[Fe(CN) ] 35,4 Strong [10]
6
-
[Au(CN) ] , 37 (best estimate) Strong [10]
2
2-
[Pt(CN) ] 40,0 Strong [17]
4
2-
[Pd(CN) ] 42,4 Strong [10]
4
3-
[Fe(CN) ] 43,6 Strong [10]
6
3-
[Co(CN) ] 64 (best estimate) Strong [10]
6
It is sometimes difficult to determine any individual species without interference from other cyanide
species or interference species (thiocyanate) and some cyanide degradation products (ammonia, nitrite
and nitrate) that may be present.
Thus, cyanide method parameters are empirical, where the actual method protocol often determines
the result obtained. Hence, cyanide is a method defined analyte. This is especially true for samples with
complex matrices. Many methods will determine the sum of a number of species with some not being
quantitatively determined (i.e. incomplete breakdown). Thus, it is essential that any standard cyanide
method is drafted in an unambiguous manner and the method protocol shall be closely followed to
ensure consistent results are obtained within and between laboratories. Moreover, all values reported
shall be attributed to the specific method applied.
A comprehensive overview of cyanide management is given in Reference [1].
It is felt that any regulatory limit legislation should specify the actual method to be used especially
for “bioavailable” cyanide (e.g. free, weak and dissociable, available, weak acid dissociable or easily
liberated cyanide).
NOTE The terms easily liberated cyanide and easily liberatable are both widely used and refer to the same
parameter.
It is vitally important to understand how the numerous forms of cyanide are incorporated into water
quality regulations for the protection of human health and the environment. In many countries, the
regulatory agencies tasked with implementing regulations and the public who are ultimately affected
by those regulations do not fully understand the implications of choosing one form of analysis over
another upon which to base numerical water quality standards. Also the effect of matrix interferences
on the results is not fully appreciated.
Methods with options (e.g. distillation versus gas membrane diffusion); or cyanide ion detection
systems based upon colorimetry or amperometry may give different results owing to variation in
species detection efficiencies and/or interference effects.
4- - 2-
Even when determining “total cyanide” some species such as [Fe(CN) ] , [Au(CN) ] , [Pt(CN) ] ,
6 2 4
2- 3-
[Pd(CN) ] and [Co(CN) ] may not be fully broken down to cyanide (or hydrogen cyanide) and some
4 6
distillation methods may convert thiocyanate (SCN) to cyanide.
Another issue is that there are few reference materials for the various cyanide parameters other than
for total cyanide. This is mainly due to the unstable nature of most cyanide species in environmental
matrices. Thus, traceable calibration in most matrices can be very difficult to achieve.
There are also a number of significant interference effects from a range of species. Clause 9 gives
[7]-[21]
guidance. More useful information is also given elsewhere .
There is no universal agreement on the best technique to overcome (or minimize) these interference
effects. The recommended guidance given is often that the method user should demonstrate that the
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ISO/TR 19588:2017(E)
method employed should be fit for purpose in relation to the samples analysed. This can be difficult
for contract laboratories which receive a wide range of unknown origin samples when using a method
for which the laboratory is accredited and the method may be inappropriate for some sample matrices.
It is important to appreciate that a single employed method may not be suitable for all the samples
received and site specific holding time analysis studies may be required to verify stability of samples
being transported to a laboratory.
A number of studies in soil samples have demonstrated that it is impossible to obtain reliable results for
easily liberatable cyanide (ELC) using a manual ELC cyanide extraction/reflux method. Consequently,
the current ISO 11262 standard does not include an ELC method.
Another key issue is the use of suitable interference and preservation treatments of the sample between
taking and analysing the sample. The presence of sulfide drastically reduces the maximum permitted
storage time from taking the sample to analysing it from 7 days to 24 hours (ISO 5667-3). See also
Reference [7].
It is considered important that regulators consider the typical measurement uncertainty when
setting very low regulatory cyanide limits; typical background levels of the parameter of interest and
finally how to ensure there is no significant sample degradation prior to analysis. See Annex C and
Reference [4].
The objective of this document is to provide a broad overview, background and guidance in the above
areas. It has attempted to review this very complex topic and highlight the various problems of carrying
out fit for purpose sampling and analysis for various cyanide species in a wide range of waters and
soils especially at low levels. It should also be helpful as a training aid for staff involved in the analysis
of cyanide. It should also be relevant to regulatory bodies involved in both setting cyanide species
regulatory limits and monitoring regulatory cyanide analysis results.
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TECHNICAL REPORT ISO/TR 19588:2017(E)
Background information and guidance on environmental
cyanide analysis
1 Scope
This document provides background information on the various International (ISO), American (ASTM,
EPA), and European (CEN) cyanide methods for soils, waters, effluents and wastes. It gives guidance
on how to carry out fit for purpose analysis of various forms of cyanide in environmental samples, the
significance of the results, how to minimize interference effects and the preservation of samples. Some
information is also provided on other national and international cyanide methods.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
See Annex A.
NOTE It is important to note that there is limited international consensus about many of these terms. The
International Cyanide Management Code — under guidance of the United Nations Environmental Program
(UNEP) and the International Council on Metals and the Environment (ICME) are two examples.
The International Cyanide Management Institute (ICMI) was established for the purpose of administering the
“International Cyanide Management Code for the Manufacture, Transport and Use of Cyanide in the Production
of Gold”, and to develop and provide information on responsible cyanide management practices and other factors
related to cyanide use in the gold mining industry.
ICMI’s primary responsibilities are to administer the International Cyanide Management Code for gold mining,
promote the Cyanide Code’s adoption and implementation, evaluate its implementation, manage the certification
process and to make information on the safe management practices for cyanide widely available.
The “International Cyanide Management Code For the Manufacture, Transport, and Use of Cyanide In the
Production of Gold” (Code) was developed by a multi-stakeholder Steering Committee under the guidance
of the United Nations Environmental Program (UNEP) and the then- International Council on Metals and the
Environment (ICME).
The Code is an industry voluntary program for gold mining companies. It focuses exclusively on the safe
management of cyanide and cyanidation mill tailings and leach solutions. Companies that adopt the Code shall
have their mining site processing operations that use cyanide to recover gold audited by an independent third
party to determine the status of Code implementation. Those operations that meet the Code requirements can
be certified. A unique trademark symbol can then be utilized by the certified operation. Audit results are made
public to inform stakeholders of the status of cyanide management practices at the certified operation.
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