chapter - ii sl'ectrophoto~letric deteriiination of...
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CHAPTER - II
Sl"'ECTROPHOTO~lETRIC DETERI"IINATION Of CYANIDE
USING ANTHRANILIC ACID AND ITS APPLICATION
'rO BIOLOGICAL F'LUIDS
SUi"iMARY
The method describes the determination of
cyanide by conversion of cyanide into cyanogen bromide
followed by the reaction with pyridine. The glutaconic
aldehyde so formed is condensed with anthranilic acid
to give a yellow-orange dye which shows a maximum
absorption at 400 nm. Beer's law is obeyed in the range
of 1 - 7 ppm. The molar absorptivity and Sandell's
sensitivity was found to be 3.12x103 lit.mol-1cm-1 and
0.0083 fg cm-2 respectively. The method has been
successfully applied for the determination of cyanide
in biological samples.
Published in Analyst, 109 (1984) 1619.
SPECTrtuPHU'l.'OJV,E'l'RIC DE.TERl'IINATION OE' CYANIDE
lJSINli A;,THrlA!:!l.LIC ACID AND ITS APPLICATION
TO BIOLOGICAL FLUIDS
Cyanides are among the most toxic of all
industrial chemicals and they are produced in large
quantities and are used in different applications (1).
Hydrogen cyanide, hydrocyanic acid, or as it is often
called 'prussic acid' is a colourless gas, with a
penetrating odour resembling that of bitter almonds,
Cyanides are used in various industries, e.g., in
extraction of noble metals, manufacturing of organic
chemicals, electroplating, hardening of steel, metal
polishing and photography (2) • Hydrogen cyanide is
used extensively as a fumigant, particularly in the
fumigatiou of ships and citrus trees. Apart from its
principal use in the fumigation, hydrogen cyanide is
used as a reagent in industry and is encountered in
concentrations that may be dangerous in certain indus
trial processes, as for instance in blast furnaces, dye
stuff works, gas works, coke ovens, tanneries, fertili
zer plants and gold gilting and gold mining (2),
The main danger of cyanide and the simple
soluble cyanides is the sudden resorption of concentra
tion doses (a drop of liquid hydrogen cyanide leads to
death in few seconds) but the danger is less acute when
Nevertheless 100-200 mg HCN m-3 inhaled in hal! to one
hour is lethal (3) , Hydrogen cyanide acts by stopping
the oxidation of pro to plasm in the tissue cells, With
high concentrations the symptoms appear rapidly, viz,
giddiness, headache, unconsciousness and convulsions
with cessation of respiration as a result of paralysis
of the respiratory centre in the brain, Repeated .
exposure to small concentration of cyanide over a long
period causes symptoms such as weakness, nausea, muscle
cramps, loss of appetite and psychoses (2). Relatively
little gross or microscopic pathology can be seen
following inhalation of hydrogen cyanide, While there
may be scattered hemorrhages and scattered congestion,
these are probably the result of anoxia, Venous blood
may appear of brighter red colour than normal. Hydrogen
cyanide vapour is absorbed extremely rapidly through the
respiratory tract; the liquid and possibly the concentra
ted vapour are absorbed directly through intact skin (1).
·As per the C & EN 1 s Dec., 2, 1985 report of
American Chemical Society, the recent Bhopal gas tragedy
appears to have two aspects in the cyanide issue, One
is the direct exposure and the other is the indirect
exposure owing to unusual generation of toxic amounts of
hydrogen cyanide in the body after exposure to methyl
isocyanate (MIC). Below is shown the proposed mechanism
for the generation of cyanide in the body after eXPosure
to rvnc,
33
34
•
Hb-NH ... + O=C=N-CH3
MIC
[
H H · I I +
Hb-N-C-N5CH "VIV
H
l -
.. - ·-·~ . --.. --~-::;:::;-;:::-::-;-~~r:::---:===="'......---'-_.J The recom~ended maximum allowab e concen
of cyanide is 5 mg m-3 in air calculated as CN-. The
world Health Organization recommends that water contain-
ing more than 0.01 ppm of cyanide (as CN-) should be
rejected as unfit for domestic supplies (4).
The detection and determination of cyanide ion
in small amounts become very important because of the
extreme toxicity of cyanide to living matter. Since
many years there has been steady increase in the methods
for determination and detection of cyanide. The methods
available are not only for 11 free cyanides" (from HCN, KCN,
and NaCN) and unstable cyano-complexes, such as
I Zn(CN4) 12- but also !or relatively stable complex
cyanides, such as, ferrocyanides and cobalticyanides,
which although are not showing typical cyanide proper
ties, are still toxic and classified by most health
author! ties with cyanides. The methods available for
cyanide detection and determination can be classified
into two groups:
(a) Non-colourimetric and
(b) Colourimetric.
The following methods fall under the non
colourimetric group -
(i) Titrimetric methods using visual end-point
indicators. The earliest reported method for determin
ing cyanide is Liebig's titrimetric method (5) based on
the formation of turbidity due to silver cyanide. This
titration is subjected to error in alkaline (6) and
ammoniacal medium (7). A similar method proposed by
Deniger (8) is based on the turbidity due to silver
iodide in the presence of ammonium hydroxide. Accurate
results are obtained in carefully regulated ammonium
hydroxide concentrations (9,10). Beerst~ (11)
modified the Deniger method .by introducing photoelectric
colourimeter and turbidimeter for end-point detection.
Ryan and Culshaw (12) reported the use of p-dimethyl
aminobenzylidene rhodanine as an indicator in Liebig's
method and this modification was recommended by the
American Public Health Association (13) for determination
35
of cyanide concentrations of 1 ppm and more. Other
titrim~tric methods involving the use of different
indicators and titrants have been reported. Diphenyl
carbazide (14), Calcein (15) and thiofluorescein (16)
36
have been used as indicators for argentimetric titrations.
Cupric diethyl dithiocarbamate (17), Variamine Blue (18)
and Nitrobenzene (with ferricyan1de)(19) are used for
titration involving the formation of mercury cyanide.
In a recently developed method cyanide is oxidised by
N-bromosuccinimide and then titrated argentimetrically
using starch-iodide, methyl blue or bromo-thymol blue
as indicator (20).
(ii) Titrimetric methods involving instrumental end
point detection make use of potentiometric titration of
cyanide with silver nitrate described by Treadwell et al.
(21) and Clark (22), This method has been applied for
the determination of cyanide in biological samples (23).
Amperometric titration is also equal in accuracy and
precision (24). Direct amperometry with a rotating
silver anode and a platinum cathode has been used by
f'ilcCloskey (25). Amperometric determination of cyanide
using flow through electrode has been made use by
Pihlar et al. (26) • Polarographic methods suggested
by Karchmer and Walker (27) and Hetman (28) are quite
sensitive too,
(iii) Gas chromatographic method have been employed
for cyanide determination by Woolmington (29), Schneider
and Freund (30) and Honma (31).
Colourimetric methods include -
1) Methods involving formation of a metal complex.
Some of these methods although specific for cyanide and
37
of ample sensitivity, produce unstable colours. Formation
of thiocyanate from cyanide (by reaction with polysulphide)
and then ferric ferrithiocyanate producing a blood red
colour, is an excellent test for cyanide (32). Another
extremely sensitive test for cyanide is the Prussian
blue test (33-35). The copper acetate-benzidine test
(36,37) is extremely sensitive and easily applied test
for the detection of cyanide. The Weehuizen method
(38-40) involves the oxidation of phenolphthalein in
alkaline solution
copper II ions in
to the corresponding red phthalein by and
the presence of cyanide,(. is a recommended
method. Indicator tube method for the determination of
cyanide involves indicato~ like bromothymol blue, bromo
cresol green, etc. (41).
The ability of the cyanide ion to form stable
complexes and cause demasking of inner-complex bonded
transition metals has also been used by various workers
for the detection and determination Of cyanide (42-44).
Methods developed by Brooke {45) and Hanker et al. (46)
are also based on the above mentioned principle.
Sensitivity is enhanced by complex formation with dimethyl
glyoxime (47). Several methods involving demasking
effects of mercury II too have been used for cyanide
determination (48,49). Spectrophotometric determination
of cyanide is also possible through ligand exchange
reaction proposed by Verma et al. (50) and Roman et al.
(51) and formation of ion-association complexes (52,53).
Schilt (54) described the spectrophotometric determinat
ion of cyanide baaed on the formation and extraction of
neutral dicyanobis (1,10 phenanthroline)-iron II complex,
produced by the exchange reaction between the reagent
ferroin and cyanide.
38
Indirect spectrophotometric determination of
cyanide have come up quite rapidly. It has been reported
by Wronski (55), Yamasaki and Ito (56), Ohlweiler and
l':editsch (57) and Gregorowicz et al. (58).
Of late, many more such methods have been
developed which are very sensitive for cyanide determi
nation but tedious too. Dagnal et al. (59) made use of
the inhibiting effect of cyanide ion on the formation of
the blue colour in neutral aqueous solution of silver/
1:10 phenanthroline, bromopyragallol red complex.
Wei-Fu Sheng et al's (60) paper reported that the
supression of the reaction of 2-(5-Br-pyridyl azo)-5-
diethyl aminophenol with Ni2+ can be used to determine
cyanide, It was found that Cu(II), chromazurol S(I) and
excess of cetyl pyridinium chloride (II) formed a stable
aquo red complex suitable for determination of cyanide(61).
Other reagents for indirect spectrophotometric determi
nation are Cadion 2B in presence of Triton X-100 (62,63),
5-phenyl azo-8-amino quinoline (64), (C.I. Mordent Blue 29)
hexadecylpyridinium complex (65) and copper(II)-2, 2'
bipyridyl ketone-2-pyridyl hydrazone (66). Ultra violet
methods for the determination of cyanide has also been
cited in the literature (67,68),
2) Colourimetric methods based on Konig reaction,
For the detection and determination of amall amounts of
cyanide in trade wastes and effluents and for water
(69,70) are based on the colourimetric procedure developed
by Alridge (71, 72) which is an example of Konig synthe
sis (73) and Epstein (74). The best known spectrophoto
metric methods for the determination af cyanide are
based on the formation af cyanogen bromide or cyanogen
chloride, which then reacts with pyridine to yield
glutaconic aldehyde ;, " .. :: which is then subsequently
39
condensed with pyrazolone (74), benzidine (75), p-phenylene-'
diamine (76), barbituric acid (77), o-dinitrobenzene (78),
isonicotinic acid-barbituric acid (79), dicarboxidine(BO),
ethyl acetone or benzoyl acetate (81). Many of these
reagents viz. benzidine, p-phenylenediamine are themselves
carcinogenic and hence their use is not desirable,
Scanning the literature :'. , reveals that still
there is need of more selective, sensitive and simple
methods for the determination of cyanide which can be
carried out with considerable ease, and also without the
use of any carcinogenic reagent. In this search, a new
method has been developed in which the determination of
cyanide is carried out by converting cyanide into cyano-
gen bromide followed by the reaction with pyridine. The
glutaconic aldehyde so formed is condensed with anthra
nilic acid, a non-toxic and easily available compound,
forming a yellow-orange dye, which is measured at 400 nm.
The Beer's law is obeyed in the range of 1-7 ppm. The
optimum reaction conditions and other analytical para
meters have been investigated. The method is success
fully applied to the determination of cyanide in
biological samples.
EXPEaiMENTAL
~paratus:
An ECIL Model GS-865 spectrophotometer and Carl
Zeiss spekol were used with 1-cm matched silica cells
for all spectral measurements.
Reagents:
Standard cyanide solution - ~5C.mg of potassium cyanide
was dissolved in 100 ml of de-ionised water to give a
solution of concentration 1 mg/ml. Appropriate dilution
of the stock solution was made to give a working standard
of 10 fg/ml.
Pyridine reagent - 3 ml of concentrated hydrochloric
acid was mixed with 18 ml of freshly distilled pyridine
and 12 ml of deionised water was added to prepare the
reagent.
Sodium arsenite solution- A 1.5% (w/v) solution of
sodium arsenite was prepared in deionised water.
Anthranilic acid A 0.1% (w/v) solution of anthranilic
acid was prepared in deionised water.
40
41 Uromine water - A saturated solution of bromine water
was prepared.
All chemicals used were of AnalaR grade and
solutions were prepared in deionised, deareated water.
Procedure:
An aliquot of aqueous sample containing 10-70 pg
(1-7 ppm) of cyanide was taken in a 10 ml volumetric
flask. To it 0.3 ml of saturated bromine water was
added and the mixture was allowed to stand for 1 minute
for complete bromination. The excess of bromine was
decolourised by dropwise addition of sodium arsenite
solution. Then 0.4 ml pyridine reagent followed by 1 ml
of anthranilic acid solution were added. The mixture
was allowed to stand for 10 minutes for full colour deve
lopment. The volume was then made upto the lllll.rk and the
absorbance was measured at 400 nm using distilled water
as reference. The same procedure was followed for the
blank, which gave no colour under these conditions.
~ULTS M~D DISCUSSIONS
Spectral characteristics:
The absorption spectra of the dye is shown in
I!'ig. 1. The spectra shows a maximum absorption at 400 nm.
The reagent blank has negligible absorption in this range.
Effect of Varying Reaction Conditions:
For bromination the amount of bromine water
needed was checked by adding various amounts of saturated
42
O.B ..-------------------------,
0.7
B 0.6
0.5 w u z <{
~ 0.4 A 0
(f)
m <{
0.3
0.2
0.1
350 3 75 400 425 450 475 500
WAVELENGTH nm
FIG.1. ABSORPTION SPECTRA OF THE DYE A. CONCENTRATION OF CYANIDE= 30J..tg/10ml. B. CONCENTRATION OF CYANIDE= SOJ...tg/1 Om!.
bromine water. i. minimum 0.2 ml of bromine water was
needed for complete bromination of the cyanide to
cyanogen bromide (Fig. 2). An excess of bromine caused
no effect as the excess was decolourised with sodium
arsenite solution.
43
Sodium arsenite solution was added dropwise until
the bromine was decolourised. In the range of 0.2 to 1 ml
of 1.5% sodium arsenite solution, no change in the absor
bance values were observed (Fig. 3). Decrease in the
absorbance was marked when more than 1 ml of sodium
arsenite was added.
The amount of pyridine reagent needed for the
conversion of cyanogen bromide into glutaconic aldehyde
was also checked. A minimum of 0.2 ml of pyridine
reagent was needed for the reaction. Addition upto 1 ml
of pyridine reagent had no noticeable effect on the
absorbance but above 1 ml there was decrease in absorb-
ance (Fig. 4).
It was found that constant absorbance values
were obtained with the addition of volumes of 0.1%
anthranilic acid solution from 1 to 5 ml (Fig. 5).
The effects of time and temperature on the
colour development were studied, It was observed that
10 minutes were needed for full·colour development
(Fig. 6) and the colour remained stable for 15 minutes 0 in the range of 15-35 c. At higher temperature there was·
a decrease in absorbance (Fig. 7).
,, .
44
0 7 E ., c 06 "" "' C)
0
'"~ 0 5 1-w u z 04 <( m a:: 03 0 (f)
m 0 2 <(
0 1
0 7 E c 0 6
C)
C)
'" 0 5 ~
w u z 0 4 <(
~ 0 3 0 (f)
m 0 2 <(
0 1
' ' ' 0.1 o.2 o.3 o.L. o.5 o.6 o.? o.e
AMOUNT OF SATURATED BROMINE WATER,ml
FIG. 2. EFFECT OF BROMINA TION CONCENTRATION OF CYANIDE= 50,Ltg/10ml.
0.2 0.4 0.6 0.8 1.0 1.4 1.6 AMOUNT OF 1.5% SODIUM ARSENITE SOLUTJON,ml J:·
FIG.3. EFFECT OF SODIUM ARSENITE ON COLOUR REACTION CONCENTRATION OF CYANIDE=50).!g/10ml.
0 7 E c 06
0 0
"· 0 5 w u
0 4 z < CD
03 0:: 0 lfl CD 0 2 <
0 1
0.2 0.4 0.6 o.s 1. 0 1.2 1 . 4 AMOUNT OF PYRIDINE REAGENT, ml
FIG.L.. EFFECT OF PYRIDINE ON COLOUR REACTION CONCENTRATION OF CYANIDE=50}Jg/10.ml.
0 7 ~ E c 0 6 1- "' 0
0 0
"· 0 5 1-w u
041-z < CD
031-0:: 0 lfl CD 021-<
0 1
' '
0.5 1.0 2.0 3.0 4.0 5.0 6.0 AMOUNT OF 0.1% ANTHRANILIC ACID,ml
45
FIG. 5. EFFECT OF ANTHRANILIC ACID ON COLOUR REACTION
CONCNTRATION OF CYANIDE= 50J.Igl10ml.
0.7 E c 0 6 C) •
C)
....r, 0.5 w u z 0.4 <(
CD a: 0.3 0 ln
CD 0.2 <(
0. 1
0.7
E c 0.6
C)
C)
....r._ 0 5 w u z 0.4 <(
CD a: 0.3 0 ln CD 0.2 <(
0.1
46
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
FIG.6. EFFECT OF TIME (minutes) ON COLOUR DEVELOPMENT
CONCENTRATION OF CYANIDE,50).lg/10ml.
\
5 10 15 20 25 30 35 40
FIG. 7. EFFECT OF TEMPERATURE (C) ON COLOUR DEVELOPME NT, CONCENTRATION OF CYANIDE, 50JJ9 /10m!.
Beer's Law, fY,olar Absorptivity, Sandell's Sensitivity
and neproducibility:
The colour system was found to obey Beer's law
4'i
in the range of 10 to 70 fg per 10 ml o! cyanide solution,(Fi~·fi).
The molar absorptivity and Sandell's
found to be 3.12x103 l.mol-1cm-1 and
sensitivity were -2 0 .0083 ,Pg em
respectively. The reproducibility of the method was
checked by seven replicate determinations (Table I).
The standard deviation and relative standard deviations
computed from the results in Table I were found to be
0.01 and 0.15% respectively.
Effect of Foreign Species:
Interferences from organic pollutants viz.
benzene, phenol, ethanol, benzaldehyde, etc. and metal
ions such as zinc, cadmium, lead, mercury and iron were
not observed, Oxidising and reducing agents if present
in small amounts, are removed by sodium arsenite and
bromine water, respectively. The tolerance limits for
diverse species ar8 shown in Table II.
iU?Plication of the Meth2,!!:
The method has been applied to the detection of
cyanide in urine and whole blood, Several samples of
urine and blood were tested and were found to be free of
cyanide. Known amounts of cyanide were therefore added
to these samples and they were analysed by the above
procedure and Alridge's method (71) after deproteini
sation with trichloroacetic acid (71). The results in
E c
0 0
O.B
0.7
0.6
"' ~ 0.5 w u z ~ CD 0:: 0 .L, 0 {/)
CD <(
0.3
0.2
0.1
10 20 30 40 50 60
CYANIDE CONCE NTRATION,ttg /10 ml
FIG. 8. CALIBRATION CURVE FOR CYANIDE.
48
70
TABLE - I
HEljHOWCIBILITY OF THE METHOD
Concentration of cyanide - 30 pg/10 ml
-------------------------------------------------------Serial
No. Absorbance max - 400 nm
-------------------------------------------------------1 0.36
2 0.35
3 0.35
4 0.36
5 0.37
6 0.35
7 0.37
Mean = 0.36
Standard deviation = 0.01
Relative standard deviation = 0.15 96
-------------------------------------------------------
49
TABLE - II
EFFECT OF FOREIGN IONS
Concentration of cyanide - 40 pg/10 ml
y------------------------------------------------------Foreign Ions (Tolerance limit in ppm)*
-------------------------------------------------------Benzene (2000), Phenol (1000), Benzaldehyde (800),
Ethanol (1200), Aniline (500), Nitrobenzene (100),
Formaldehyde (700), Hydroxylamine (500), Zn2
+ (200),
Cd2+ ( 100) 1 Pb2+ ( 150), Hl+ ( 100), Fe2+ (250) 1
eu2+ (300), K+ (500), Na+ {500), soz- (350),
Thiocyanates - interfere.
-------------------------------------------------------* Amount of foreign species that cause z 2% error.
50
Table III a & b show that the recoveries !rom urine and
whole blood samples were about 95 and 98% respectively,
which is in agreement with the results of Alridge's
method.
CONCLUSIOti
The method is simple, sensitive and rapid, No
use is made'of carcinogenic compounds and it can be
successfully applied for the detection of cyanide in
biological fluids.
I QMIIIIIIJIIIIIIIWI m" 1~1 "~ T 8492
51
TABLE - III
RECOVEJW OF CYANIDE FROf/1 BIOLOGICAL FLUIDS
----------------------------------------------------------Sample Cyanide Cyanide
No. added/fg found by present method*
Recovery Cyanide Recovery % found by %
Alridge' s method *
pg ?g ----------------------------------------------------------
1
2
3
4
1
2
3
4
{a) VOLU!'lE OF URINE SAMPLE
15 14.25 95.0
30 28.45 94.8
45 42.80 95.2
60 56.15 93.6
(b) VOLUME OF BLOOD SAMPLE
15 14.78 97.9
30 29.45 98.2
45 44.10 98.0
60 58.30 97.2
- 1 ml.
14.25 95.0
28.55 95.2
42.75 95.0
56.10 93.5
- 1 ml.
14.70 98.0
29.35 97.8
44.20 98.2
58.50 97.5
---------------------------------------------------------- •'
* Mean of three repetitive analyses.
52
1 •
2.
4.
5.
6.
7.
8.
9.
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