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Correspondence Author: Dr. Ajay Sharma;
Head, P.G. Deptt. of Chemistry, Govt. College, Sirohi,(RAJ.), India
e-mail-ajay395@gmail.com
J. Chem. Bio. Phy. Sci. Sec. A. 2013, Vol.3, No.2,929-935
Estimation of Cystiene Using Sodium
Nitroprusside by a Newer Photochemical
Method
Shailendra Singh Rathore, Ravi Sharma, Devendra Kadam
and Ajay Sharma
February 2013- April 2013, Vol. 3, No. 2, 929-935. E- ISSN: 2249 –1929
Journal of Chemical, Biological and Physical Sciences
An International Peer Review E-3 Journal of Sciences
Available online atwww.jcbsc.org
Section A: Chemical science
CODEN (USA): JCBPAT
Research Article
929
J. Chem. Bio. Phy. Sci. Sec.C, 2013, Vol.3, No.2, 929-935.
Estimation of Cystiene Using Sodium Nitroprusside by a
Newer Photochemical Method
1
Shailendra Singh Rathore, Ravi Sharma
2
, Devendra Kadam
3
and Ajay Sharma
1*
1
Department of Chemistry, Government College, Sirohi-307001(RAJ.), India
2
Department of Chemistry, Government College, Sheoganj,(Sirohi) (RAJ.), India
3
Benzir College & Research Centre, Barkatullaha University, Bhopal, India
Received: 14 February 2013; Revised: 8 March 2013; Accepted: 10 March 2013
Abstract: A newer fast, convenient and inexpensive quantitative method for the
determination of Cystiene using photochemical exchange reaction of sodium
nitroprusside has been investigated. Sodium nitroprusside is a photolabile complex and it
undergoes photochemical ligand exchange reactions rapidly. Some recent efforts have
been made to utilise such reactions for the estimation of some sulphur containing anions
and electron rich organic molecules. The progress of the reaction is observed
spectrophotometrically. The effects of different parameters like pH, change of
concentration of sodium nitroprusside, concentration of ligands, light intensity etc. on
percentage error was investigated. The efforts were made to minimise the percentage
error and some optimum conditions were obtained. Such reaction can be used for the
determination of Cystiene in the range of millimoles to micromoles, hence it is important
to know whether such estimations can be done successfully and that to with the desired
accuracy.
Keywords: photochemical exchange reaction, sodium nitroprusside, quantitative,
Cystiene, percentage error.
Estimation
… Shailendra Singh Rathore et al.
930
J. Chem. Bio. Phy. Sci. Sec. A, 2013, Vol.3, No.2, 929-935.
INTRODUCTION
Photochemistry plays a pivotal role in a number of chemical and biological processes. Photosynthesis is
such an important photochemical reaction controlled by nature, which still exists as a challenge to the
photochemists. The essential feature of photochemistry is probably the way in which the excited states of
the atoms or molecules play a part in process of interest. It is apparent that the absorption or emission of
radiation to/from these states is the concern of spectroscopists as well as the photochemists.
Photosensitized reactions are widely used in many technical and biological areas. Organic chemist may
seek an improved understanding through the example that photochemistry gives the relationship between
reactivity and electronic and molecular structure
1
. Photosensitized reactions like copolymerization have
been reported by Wayne and Burrows et al.
2
.
Cysteine is a sulphur containing amino acid and it is presented in the form of its oxidized product
cysteine. In this form, the disulphide cross links may be intra or intermolecular. The thiol group of
Cysteine is active and it is blocked by a wide range of aralkyl. The commonly used blocking groups are
Benzyl
3
, diphenyl methyl
4
, and triphenylmethyl
5,6
. Cysteine is a major metal binding sites in proteins as a
ligand, it shows ambidentate behaviour and can be tridentate or bidentate through coordination of
(S,N,O) (S,N) (N,O) or (S,O) donor atoms. The strong affinity of soft metal ions for ionized thiol groups
also gives rise to monodentate behaviour. The thiol anion is also a very effective metal binding site.
Some of the known modes of binding of cysteine to various metal ions is given in Table-III . A number
of cysteine complexses have been studied and it seems that at least two functional groups on the liagnd
7
are utilized for binding it to the metal atom. One of these must be sulphur, while the other may
be –COOH or NH
28
. Cysteine has been used as a detoxicant and as dough conditioner.
The photocatalytic oxidation of ascorbic acid with the evolution of hydrogen by platinum loaded
TiO
2
-[Ru(bpy)
3
]
+2
system was observed by Taqui Khan et al.
9
. Belousov et al.
10
studied the
photocatalytic properties of homogeneous colloids and heterogenous vanadium containing system (in
etahnol). The photocatalytic cyclisation of 7-styryl-1-H-pyrool-(2,6)-pyridiuinium bromide was
investigated by Ogali and Walker
11
.The effect of inorganic anions on the TiO
2
based photocatalytic
oxidation of aqueous ammonia and nitrite was reported by Zhu et al.
12
.
A comparison between TiO
2
and Fenton plus photo-Fenton in a solar pilot plant was reported by
Maldonado et al.
13
.
Matsuo and Udea
14
used TiO
3
-TiO
2
composite powder for the photocatalytic
bleaching of methylene blue. Photocatalytic degradation and adsorption of di-isopropyl fluorophosphate
and dimethyl phosphonate over dry and wet rutile TiO
2
was studied by Kiselev et al.
15
. Physiochemical
and photocatalytic characterization of TiO
2
/Pt nanoparticles has been made by Liu et al.
16
. Yuan et al.
17
observed Fe assisted photocatalytic degradation of microcystin- LR using titanium dioxide.
Photodegradation and adsorption of 1,4-dioxane on TiO
2
was carried by Yamazaki et al.
18
.
Photocatalytic selective oxidation of methanol to methyl formate in gas phase over titanium (IV) oxide in
a flow-type reactor was reported by Kominami et al.
19
. Lv et al.
20
synthesized floriated ZnFe
2
O
4
with
porous nanorod structures and determined its photocatalytic hydrogen production ability under visible
light. Role of defects and paramagnetic species in solar photoactivity of nano-N-TiO
2
from tertiary
amine was reported by Spadavecchia et al.
21
. Effect of light source on the catalytic degradation of
protocatechuic acid in a ferrioxalate-assisted photo-Fenton process was observed by Monteagudo et al.
22
.
Lo et al.
23
manufactured novel twin reactor to separate evolution of hydrogen and oxygen in
photocatalytic water splitting. Photocatalytic oxidation for antimicrobial control in built environment
was studied by Chen et al.
24
.
Estimation
… Shailendra Singh Rathore et al.
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J. Chem. Bio. Phy. Sci. Sec. A, 2013, Vol.3, No.2, 929-935.
EXPERIMENTAL
A 100 mL stock solution of Cysteine (M/100) and 100 mL stock solution of sodium nitroprusside
(M/100) were prepared by dissolving 0.1210g of Cysteine and 0.2979g of sodium nitroprusside in doubly
distilled water. 20 mL of stock sodium nitroprusside solution was diluted to 100 mL to form M/500
concentration and then it was divided into five equal parts (20 mL each). In each beaker the solution of
(M/100) Cysteine was mixed as 0.4 mL, 0.8 mL, 1.2mL, 1.6mL and 2.0 mL and all the beakers were
exposed to a 200 watt tungsten lamp for 13 minutes. A change in colour of solution was observed from
light red to pale yellow.
An aliquot of 5.0 mL solution was taken out from each reaction mixture and change in optical density
was observed spectrophotometrically at λ
max
= 310 nm. A graph was plotted between optical density and
known concentration of Cysteine i.e. [1.96 x 10
-4
M, 2.91 x 10
-4
M, 3.84 x 10
-4
M, 5.66 x 10
-4
M, 7.42 x
10
-4
M, 8.23 x 10
-4
M]. A straight line was obtained, which was used later on as a calibration curve. 1.0
mL sample solution of known Cysteine concentration was mixed in 20 mL of sodium nitroprusside
(M/500) and it was exposed to tungsten lamp under identical conditions. The optical density was
measured spectrophotometrically and the concentration of sample solution was determined by the
calibration curve. From this determined concentration the percentage error was calculated for Cysteine
sample solution.
EFFECT OF PH
The photochemical reaction of sodium nitroprusside in presence of Cysteine may be affected by the
variation in pH value and the estimation of Cysteine may also be affected accordingly. Therefore the
effect of pH on quantitative estimation of Cysteine was studied at different pH range. The results are
reported in Table -1
Table -1: Effect of PH
[SNP] = 6.3 x 10
–
3
M [Cysteine] = 2.5 x 10
-
3
M
Light Intensity = 14.0 mWcm
-
2
λ
max
= 310 nm
pH Error (%)
4.0 3.5
4.5 3.2
5.0 3.1
5.5 2.7
6.0 2.2
6.5 1.0
7.0 2.0
7.5 2.3
8.0 2.5
8.5 2.5
9.0 3.0
9.5 3.2
10.0 3.2
10.5 3.4
11.0 3.5
Estimation
… Shailendra Singh Rathore et al.
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J. Chem. Bio. Phy. Sci. Sec. A, 2013, Vol.3, No.2, 929-935.
It was observed that the minimum error in the estimation of Cysteine is found at pH = 6.5 i.e. only 1.0%
which is within permissible limit. Below pH = 6.5 cysteine remains in protonated form, which is not
good donor whereas on other hand pH higher than 7, it remains in anionic form, but the percentage error
is high in alkaline range indicating that it is not a good donor in spite of being negatively charged. The
results indicate that cysteine replaces some ligands from the coordination sphere of iron easily in the
form of zwitter ion to form the complex.
EFFECT OF CYSTEINE CONCENTRATION
The effect of the concentration of Cysteine on the estimation was also observed by taking different
concentration of cysteine and keeping all other factors identical. The results are reported in Table -2
Table -2: Effect of Cysteine Concentration
[SNP] = 6.3 x 10
-
3
M pH = 6.5
Light Intensity = 14.0 mWcm
-
2
λ
max
= 310 nm
[Cysteine] x 10
3
M Error (%)
1.0 3.0
1.4 2.7
1.5 2.5
1.6 2.5
1.8 2.3
2.0 2.0
2.2 1.5
2.5 1.0
2.8 1.5
3.3 2.0
4.0 2.5
5.0 3.0
6.6 3.5
It was observed that the minimum error in the estimation of Cysteine is found at Cysteine concentration
2.5 x 10
-3
M i.e. only 1.0% that is within permissible limit. As the concentration of Cysteine increases the
complex formation tendency increases and hence the percentage error found in estimation of Cysteine is
minimum but as the concentration is increased higher than 2.5 x 10
-3
M there may be possibility of some
larger units 2 or more than 2 molecules of Cysteine bind together through intermolecular hydrogen
bonding. Such a unit will not participate in complex formation due to its larger size and lower
nucleophilicity, therefore limited complex formation takes place resulting into increase in error at higher
concentration of Cysteine.
EFFECT OF SODIUM NITROPRUSSIDE CONCENTRATION
The effect of variation of concentration of sodium nitroprusside on the quantitative estimation of
Cysteine and percentage error was observed by taking different concentration of sodium nitroprusside
and keeping all other factors identical. The results are reported in Table 3.It was found that the minimum
error in the estimation of Cysteine is found at sodium nitroprusside concentration 6.3 x 10
3
M i.e. only
1.0%, which is within permissible limit. As the concentration of sodium nitroprusside increases the
complex formation tendency increases, it reaches maximum at sodium nitroprusside concentration 6.3 x
Estimation
… Shailendra Singh Rathore et al.
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J. Chem. Bio. Phy. Sci. Sec. A, 2013, Vol.3, No.2, 929-935.
10
3
M but if the concentration is further increased it will start acting like a internal filter and it will not
permit the desired light intensity to reach sodium nitroprusside molecule in the bulk of the solution, as a
consequence only limited number of sodium nitroprusside molecule will be excited to participate in the
complex formation resulting into increase in percentage error.
Table- 3: Effect of Sodium Nitroprusside Concentration
[Cysteine] = 2.5 x 10
-
3
M pH = 6.5
Light Intensity = 15.0 mWcm
-
2
λ
max
= 310 nm
[SNP] x 10
-
3
M Error (%)
3.0 4.5
3.3 4.0
4.0 3.5
4.4 2.7
5.0 2.2
5.5 2.0
5.8 1.5
6.3 1.0
6.6 1.5
7.1 2.1
7.6 2.5
8.3 3.5
9.0 4.5
10.0 4.5
EFFECT OF LIGHT INTENSITY
The effect of light intensity on the percentage error in the estimation of Cysteine while its photochemical
reaction with sodium nitroprusside has been observed by varying the distance between the exposed
surface of the reaction mixture and tungsten lamp light source. The result for tungsten lamp are tabulated
in Table -4
Table -4: Effect of Light Intensity
[Cysteine] = 2.5 x 10
-
3
M pH = 6.5
[SNP] = 6.3 x 10
-
3
M
λ
max
= 310 nm
Light Intensity (mWcm
-
2
) Error (%)
6.0 3.5
7.0 3.2
8.0 2.8
9.0 2.5
10.0 1.7
11.0 1.5
12.0 1.2
13.0 1.0
14.0 1.0
15.0 1.0
16.0 1.0
Estimation
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J. Chem. Bio. Phy. Sci. Sec. A, 2013, Vol.3, No.2, 929-935.
It is observed that the minimum error in the estimation of Cysteine is found at tungsten lamp intensity =
13.0 mWcm
-2
i.e. only 1.0% which is within permissible limit. As the light intensity was increased the
number of photons striking per unit area per second will also increase. As a result the complex formation
became little bit easier on increasing light intensity, on further increasing the light intensity beyond 13.0
mWcm
-2
the error remains almost constant indicating that the desired light intensity for maximum
(complete) formation of complex requires this much intensity and any increase will not increase the
amount of complex formed. This will result into a constant error above this intensity.
OPTIMUM CONDITIONS
The photochemical reaction between sodium nitroprusside and Cysteine was carried out. It was observed
that if the estimation of Cysteine is carried out under these given conditions the percentage error
observed is minimum (1.0 %) and within permissible limit.
The optimum conditions are given below:
(i) pH = 6.5
(ii) [Sodium Nitroprusside] = 6.3 x 10
-3
M
(iii) [Cysteine] = 2.5 x 10
-3
M
(iv) Light Intensity = 13.0 mWcm
-2
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Corresponding author: Dr. Ajay Sharma
;
Head, P.G. Deptt. Of Chemistry,
Govt. College, Sirohi-307001(RAJ.), India
e-mail-ajay395@gmail.
com