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United States
Environmental Protection
Agency
Environmental Monitoring and
Support Laboratory
Cincinnati OH 45268
^T V
V
Research and Development
EPA-600/S4-83-054 Dec. 1983
Project Summary
Development and Evaluation of
Procedures for the Analysis of
Simple Cyanides, Total Cyanide,
and Thiocyanate in Water and
Wastewater
D. Ingersoll, W. R. Harris, D. C. Bomberger, and D. M. Coulson
This research program was initiated
to develop and/or evaluate analytic test
procedures for the analysis of simple
cyanides, total cyanides, and thiocyan-
ates.
Seven methods for the analysis of
simple cyanides have been investi-
gated. Included are: (1) an ion-
exchange procedure; (2) a continuous
flow distillation; (3) an EDTA electrode
method; (4) the AISI aeration method;
(5) an EDTA aeration method; (6) the
modified Roberts-Jackson method;
and (7) the EPA method for Cyanides
Amenable to Chlorination. The methods
that show the most promise are the
modified Roberts-Jackson method, the
EDTA aeration procedure, and the pro-
cedure "Cyanides Amenable to Chlo-
rination."
Of all the procedures studied, the
modified Roberts-Jackson method is
the best. It gives complete recovery for
all but one of the simple cyanides with-
out decomposing the complex cyanides.
However, the most significant operating
characteristic is its unique ability to
perform accurately in the presence of
both sulfide and thiocyanate.
In addition to these methods for
simple cyanides, we have evaluated the
EPA method with an ion-selective elec-
trode finish for the analysis of total
cyanide, and have also developed and
evaluated ligand-exchange and high
temperature distillation procedures for
the analysis of total cyanides. The
ligand-exchange procedure appears to
be the most advantageous method of
analysis of total cyanides. It not only
gives recoveries comparable to those
found for the EPA method, but also
is unaffected by the presence of either
sulfide or thiocyanates. Analysis time is
also reduced.
Methods investigated for the analysis
of thiocyanates included colorimetric,
high performance liquid chromato-
graphic, and atomic absorption spec-
trophotometric methods. All these
methods are based on the formation
and extraction of a dithiocyanatodipyri-
dylcopper (II) complex. None of the
methods studied can accurately
quantitate thiocyanate below 30 ppb.
This report was submitted in partial
fulfillment of Contract No. 68-03-
2714 by SRI International under the
sponsorship of the U.S. Environmental
Protection Agency. This report covers
the period from September 1978
through April 1980.
This Project Summary was developed
by EPA's Environmental Monitoring and
Support Laboratory. Cincinnati. OH. to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
The Federal Water Pollution Control
Act Section 304(h), as amended after
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1972, requires that the Administrator
promulgate guidelines establishing test
procedures for the analysis of pollutants.
These test procedures must be applicable
to measure a specific pollutant in a wide
variety of industrial effluents. The
objectives of this work were to review the
pertinent literature; to determine the
technical approaches to be taken for
development; and to evaluate test
procedures for analysis of cyanides and
thiocyanates Two new methods for total
cyanide were developed and evaluated
during this study and are compared with
the EPA procedure for total cyanide.
Three methods for thiocyanate were
tested. These procedures depend on the
chloroform extraction of the neutral
dithiocyanatodipyridylcopper (II) complex
to separate the SCN" from the sample
matrix The thiocyanate was quantitated
by colonmetry, high performance liquid
chromatography, or graphite furnace
atomic absorption spectroscopy. Statisti-
cal evaluation of the test results was
obtained at several concentration levels
for each of the methods studied.
Six existing procedures for the analysis
of simple cyanides were evaluated and
compared to the EPA-approved method,
"Cyanides Amenable to Chlorination,"
found in the Manual of Methods for
Chemical Analysis of Water and Wastes,
1979, EPA-600/4-79-020. A statistical
evaluation of the test results was obtained
at several concentration levels.
Conclusions
Total Cyanides
High Temperature Distillation
The primary advantage of this
procedure is its ability to recover cyanide
from all compounds studied, including
the thermodynamically stable, kineti-
cally inert K3(Co(CN)6). The method is
subject to a number of interferences
including sulfide and thiocyanate. The
lower limit of detection using this method
is estimated to be 6 ppb, higher than any
of the other total cyanide methods
studied.
EPA Total Cyanides
The digestion-distillation procedure
approved by the EPA for the analysis of
total cyanides was evaluated. Complete
recoveries of cyanide were possible from
all of the compounds studied except
K3(Co(CN)6). Included in this list are the
stable fern and ferrocyanide complexes.
The lower limit of detection is 2 ppb ± 1
ppb. The relative standard deviation
above 10 ppb is less than ± 10%. The
main disadvantage of the procedure is
interference from a number of
compounds. Of major concern are sulfide
and thiocyanate. Various procedures
have been described to alleviate these
problems, but these procedures also
introduce additional problems. As such,
this method should be used for the
analysis of cyanide in samples that do not
contain either sulfide or thiocyanates.
Ligand-Exchange
A procedure was developed that gives
not only complete recovery of jcyanide
from all of the compounds studied except
K3(Co(CN)6), but also is unaffected by the
presence of either sulfide or thiocyanate.
This is a major development in the field of
cyanide analysis, since these compounds
have historically been a major problem.
Another advantage is a 30% reduction in
analysis time. The lower limit of detection
is 2 ppb ± 1 ppb. The relative standard
deviation above 10 ppb is less than ± 10%.
Simple Cyanides
Ion Exchange
An ion exchange procedure for the
analysis of simple cyanides was
evaluated and found to be unacceptable.
Among its deficiencies are: (1) the lower
limit of detection is well above 2 ppm; (2)
analyses are time consuming; and (3)
there is incomplete recovery of cyanide
from the column during the rinsing
operations. Only considerable
developmental effort could improve the
performance of this procedure.
EDTA Electrode
Although this is a relatively simple
procedure, its use is limited only to
samples that do not contain certain other
interfering compounds. The procedure is
able to accurately measure only easily
dissociable cyanides. Only with
additional developmental work could this
procedure be made to operate efficiently.
Continuous-Flow Distillation
Although this procedure is fast and
easy to operate, the iron cyanides are
partially decomposed, which leads to
spuriously high results. A vast amount of
additional work is required to improve the
performance of this method. However,
this procedure could be adapted for use
as an analytical method for total
cyanides.
AISI Aeration
The major disadvantage of this
procedure is its inability to obtain
complete recoveries from the cyanide
equivalent to cyanides amenable t
chlorination. Also of concern are it
increased lower limit of detection (5 ppt
and lower precision. These problems ar
inherent in the technical design of th
apparatus and could probably b
improved through modifications of th
apparatus and procedure.
EDTA Aeration
In an effort to take advantage of th
beneficial characteristics of th
preceding two methods, an EDT/s
Aeration procedure was developed an
evaluated. Incomplete recoveries <
cyanide were found from half of th
simple cyanides studied and a lower lim
of detection of 5 ppb. Most significant!
neither thiocyanate nor sulfide (as Pb!
interfere with an analysis.
EPA Procedure for Cyanides
Amenable to Chlorination
The EPA procedure for chlorinatic
and distillation of the samples has bee
evaluated in our laboratories. Incomple'
recoveries of cyanide were found from
number of simple cyanide species. The;
recoveries were also concentratic
dependent. Recoveries could probably t
improved by altering the chlorinatic
conditions. The lower limit of detection
2 ppb + 1 ppb. Since the method does re
on the EPA-approved total cyanii
methodology, all of the deficiencies ass
ciated with that method are also appli
able here. Because of its widespread us
additional effort should be expended
improve the method.
Modified Roberts-Jackson
Incomplete recovery of cyanide is fou
only from the mercury-cyanii
compounds. The addition of chloride i
during analysis will probably overcor
this deficiency. The procedure
unaffected by the presence of eith
sulfide or thiocyanate. Other compoun
that interfere are removed befc
analysis. A lower limit of 2 ppb + 1 ppt
possible with a precision of ± 10% abc
10 ppb.
Thiocyanates
Three different analytical techmqu
for the analysis of thiocyanate have be
investigated--colori metry, hi<
performance liquid chromatography, a
atomic absorption spectroscopy. All thr
methods rely on the formation of a mix
ligand complex between copper (
pyridine, and thiocyanate. The comple>
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normally extracted into chloroform, at
which point problems develop. At
concentrations below 200 ppb, the high
background level of copper interferes
with detection of thiocyanate. Thus, even
though the analytical methods are quite
sensitive, the effective lower limit of the
detection of thiocyanate is over 100 ppb.
Recommendations
The following recommendations are
made for the analysis of simple cyanides,
total cyanides, and thiocyanates.
1. Developmental work on the ligand-
exchange method for analysis of
total cyanide should be continued.
In particular, the conditions of
analysis should be improved and
this optimized procedure should be
made more rugged and evaluated on
both laboratory standards and field
samples.
2. If the analysis of metal-cyanide
complexes are more stable than
either ferri or ferrocyanide is needed
additional effort should be expended
on the development of the high
temperature distillation.
3 Performance of the Roberts-
Jackson method of analysis could be
improved with minor modification.
A comprehensive evaluation of the
method should be conducted to
determine the effect of chloride ion
on cyanide recoveries and
interferences. On this basis, a
procedure should be optimized and
evaluated on laboratory-prepared
samples.
4. Recoveries from EPA procedure
"Cyanides Amenable to Chlorina-
tion" might be improved by modifying
the chlorination procedure. A study
should be undertaken to determine
the most efficient chlorination
conditions and a modified procedure
should be developed.
5. It is felt that the lower limits of
detection for cyanide could be
lowered by one order of magnitude
by adjusting the pH of the solution in
the electrode finish. The optimum
pH should be determined and then
used in all the electrode procedures
6. To accurately assess the perform-
ance of the more effective total
cyanide and simple cyanide
methods, it is necessary to conduct
a limited sampling and analysis
schedule of industrial effluents. The
sites selected for monitoring should
represent widely divergent sources
and include sites where cyanide and
common interferences are expected.
Some sites that should be sampled
include refineries, coking
operations, and coal gasification
industries.
7. The methods evaluated for
thiocyanate analysis are unsatis-
factory
D. Ingersoll, W. Ft. Harris, D. C. Bomberger. and D. M. Coulson are with SRI
International, Menlo Park. CA 94025.
Gerald D. McKee is the EPA Project Officer (see below).
The complete report, entitled "Development and Evaluation of Procedures for the
Analysis of Simple Cyanides, Total Cyanide, and Thiocyanate in Water and
Wastewater." (Order No. PB 84-112 663; Cost: $14.50, subject to change) will
be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Monitoring and Support Laboratory
U.S. Environmental Protection Agency
Cincinnati. OH 45268
US GOVERNMENT PRINTING OFFICE 1983-659-017/7233
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Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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