Investigation of electrochemica behaviour of chromium(VI)-dithiocarbamate complexes detection of chromium(VI) in real samples

Article abstract of DOI:10.13005/ojc/340209

A facile, rapid and sensitive catalytic hydrogen signal method has been developed for the analysis of chromium(VI) using two new ligands Ammonium N-phenylpiperazine-1-carbodithioate (APP-CDT) and Ammonium N-benzylpiperidine-1-carbodithioate (ABP-CDT) were

Full text of DOI:10.13005/ojc/340209

ISSN: 0970-020 X
CODEN: OJCHEG
018, Vol. 34, No.(2):
Pg. 675-682
ORIENTAL JOURNAL OF CHEMISTRY
An International Open Free Access, Peer Reviewed Research Journal
2
www.orientjchem.org
Investigation of Electrochemical Behaviour of
Chromium(VI)-dithiocarbamate Complexes
Detection of Chromium(VI) in Real Samples
1
2
NIRANJAN THONDAVADA , GIRIDHAR CHEMBETI ,
1
2
GAN. G. REDHI and VENKATASUBBA NAIDU NUTHALAPATI
1
Department of Chemistry, Durban University of Technology, P.O. Box 1334, Durban 4000, South Africa.
Department of Chemistry, Sri Venkateswara University, Tirupati-517502, Andhra Pradesh, India.
2
*
Corresponding author E-mail: niranjan994@gmail.com
http://dx.doi.org/10.13005/ojc/340209
(Received: December 09, 2017; Accepted: January 31, 2018)
ABSTRACT
A facile, rapid and sensitive catalytic hydrogen signal method has been developed for the
analysis of chromium(VI) using two new ligands Ammonium N-phenylpiperazine-1-carbodithioate
(
APP-CDT) and Ammonium N-benzylpiperidine-1- carbodithioate (ABP-CDT) were synthesized.
The method was depending on the reaction of chromium(VI) with APP-CDT and ABP-CDT at pH
.6 and 7.8 respectively in supporting electrolyte (NH Cl-NH OH) medium. The resulting oxidation
8
4
4
peaks were obtained at -1.68V and -1.60 V vs SCE respectively, due to the catalytic hydrogen
signals (CHS’s). Different experimental conditions such as pH effects, background electrolyte
(
NH Cl-NH OH) effects and carbodithioate (CDT) and chromium(VI) ion effects were studied.
4 4
The present technique was successfully used to detect chromium(VI) in several environmental,
biological samples. It was demonstrated that the obtained recovery percentages (95-99%) were
comparable to the Atomic Absorption Spectrophotometry (AAS) method.
Keywords: D.C. Polarography, Chromium(VI), Catalytic hydrogen signals (CHS’s),
Ammonium N-phenylpiperazine-1-carbodithioate (APP-CDT) and Ammonium
N-benzylpiperidine-1-carbodithioate (ABP-CDT).
INTRODUCTION
chromium(VI) species are well-known to be noxious
and give rise various healthiness problems . The
2
Generally, chromium exists in nature as
literature reports suggest that the Cr(VI) compounds
are more noxious than Cr(III) compounds . The
salts of chromium are widely adopted in industries,
resulted in the water pollution. Large amounts of
3
chromium(VI) and chromium(III), and its valence
state in natural water depends on the presence of
1
organic matter and oxygen content . The
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4

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76
THONDAVADA et al., Orient. J. Chem., Vol. 34(2), 675-682 (2018)
-
1
chromium is expected to enter into environment from performed by taking 3.928 g L of CuSO .2H O and
4
2
leather, steel and chrome-plating industries. In it was dissolved in millipore water then made
drinking water, tolerance limits of chromium is found up to the mark in one litre flask. Preparation of
-
1
to be 50 μg L and therefore, it is appraised to be APP-CDT /ABP-CDT (0.01 M) by taking 2.55/2.67 g
toxic and of great concern when found beyond its and then dissolved it in 100 mL millipore water. Standard
4
acceptable limits .
ligands and supporting electrolyte solutions were
freshly prepared and stored at 4 C.
o
Different analytical methods such as
5
inductively coupled plasma-mass spectroscopy , Synthesis of APP-CDT and ABP-CDT
inductively coupled plasma-atomic emission
4
0 g of carbon disulphide was steadily
mixed with 45 of 1-phenylpiperazine/
-benzylpiperidine dissolved in 25 mL deionized
6
7
spectroscopy , electroanalytical , nuclear and
spectroscopy
g
8
-10
have been determined for the
4
detection of chromium(VI). However, the above
reported methods are sensitive, but relatively
expensive and require specialized technicians to
operate the instruments. The current catalytic
hydrogen signals of Cr(VI)-thiocompound
compounds were testified for waste water, industrial
run-offs and agrarian resources from these research
o
water at 4 C with constant agitation. Then 0.1 N
NH OH was slowly added into the reaction mixture
4
to achieve neutralization. The final white coloured
solid was collected and purified by repeated
1
9-26
washing with acetone (Scheme 1a-b)
.
1
1-18
Experimental procedure
laboratory
in maximum research laboratories. This paper deals
with the development of a sensitive, cost-effective NH Cl-NH OH, ligands (APP-CDT and ABP-CDT)
and the equipment’s used are existing
In a 100 mL beaker measured volumes of
4
4
catalytic hydrogen signals technique for the and then metal solutions were added. By using 0.1
detection of chromium(VI). The method was
performed by two new reagents namely,
Ammonium N-phenylpiperazine-1-carbodithioate
M HCl and NaOH, the desired pH was altered and
then poured into the polarographic cell. Pure
nitrogen gas (99.9 %) was passed through the
solution for about fifteen min to take away the
amount of oxygen present in the sample solution.
Lastly, the polarograms were documented by
means of the D.C. Polarography technique.
(
1
APPC-DTC) and Ammonium N-benzylpiperidine-
-carbodithioate (ABPC-DTC) which gives CHSs
with the metal-carbodithioate complexes at ambient
conditions. The attained results were equated with
Atomic Absorption Spectrophotometry (AAS).
RESULTS AND DISCUSSION
MATERIALS AND METHODS
In this section, various experimental
conditions were optimized to detect chromium(VI)
at DME.
Instrumentation
Direct current polarography, model
CL-357 and Cl-25 were used in this study (Elico
Private Ltd, Hyderabad, India). The Shimadzu AA
pH effect
6300 spectrometer equipped with a hollow cathode
The pH effect on CHSs was performed by
generating the polarograms at different pH’s ranging
from 5.0-10.0, retain the chromium(VI) and ligands
concentration at 4.0 ppm and 0.4/0.5 M respectively
in supporting electrolyte medium. The wave
shape continued to be unaffected, however,
the peak steadily goes-up till pH values of 8.6/7.8
(APP-CDT/ABP-CDT) and after reaching these pH
lamp and a deuterium background corrector, at
respective wavelengths (resonance line) using an
air acetylene flame was used. The instrumental
parameters were those recommended by the
manufacturer.
Reagents
The chemicals like NH , CS , NH Cl, values peak goes-down. Therefore, maximum pH
3
2
4
1
-phenylpiperazine and 4-benzylpiperidine were values were chosen as ideal for further studies. With
obtainedfromSDFinechemicals, India. Thepreparation increase in pH, the peak potential moved to words
-
1
of chromium(VI) stock solution (1 μg mL ) was negative scale as illustrated in Figure 2.

THONDAVADA et al., Orient. J. Chem., Vol. 34(2), 675-682 (2018)
677
Scheme 1. Synthesis of (A) APP-CDT (B) ABP-CDT
Supporting electrolyte effect(NH Cl-NH OH)
4
4
This study was performed by adjusting the
supporting electrolyte concentration from 0.05-1.0
M keeping 4.0 ppm Cr(VI) ion and 3.0/4.0
APP-CDT/ABP-CDT constant at pH 8.6/7.8
respectively. Peak increased till the concentration
reaches 0.4/0.5 M NH Cl for APP-CDT/ABP-CDT,
4
but decreased beyond these concentrations.
Consequently, these values were chosen as ideal
for further studies as illustrated in Figure 3.
Fig. 1. The CHSs of Chromium(VI) in
NH Cl-NH OH medium with (A) APP-CDT:
4
4
(
a) Blank (b) 3.0 mM APP-CDT (c) 4.0 ppm Cr(VI)
d) 3.0 mM APP-CDT +4.0 ppm Cr(VI), (B) ABP-CDT: (a)
Blank (b) 4.0 mM ABP-CDT (c) 4.0 ppm Cr(VI) (d)
.0 mM ABP-CDT +4.0 ppm Cr(VI)].
(
4
Fig. 3. Effect of supporting electrolyte for the
analysis of Cr(VI) with APP-CDT and ABP-CDT
Effect of reagents concentration
The impact of reagents concentration
of APP-CDT/ABP-CDT on the catalytic peaks of
Cr(VI)-DTC were studied using different
concentrations ranging from 0.2 mM to 6.0 mM.
Remarkably, it was noticed that height of the peak
increased till 3.0/4.0 mM (APP-CDT/ABP-CDT).
Therefore, the maximum peaks obtained at3.0/4.0 mM
Fig. 2. Effect of pH for the analysis of Cr(VI) with

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THONDAVADA et al., Orient. J. Chem., Vol. 34(2), 675-682 (2018)
(APP-CDT/ABP-CDT), and with excess addition of Effect of mercury pressure on peak height
CDT, the peak was not proportionate to the
concentration of the ligands. On increasing the
concentration of carbodithioate, peak potential
attracts towards more negative. The differences of
peak height as a function of concentration of CDT is
The effect of pressure of mercury
in the reservoir on the peak height was studied at
different mercury column heights. As the column
height (h) of the mercury reservoir is increased peak
2
7
not stating the typical nature of CHSs . The height and i √h are marginally decreased where
c
28-30
maximum peak shape is indicatory of adsorption
see Fig. 4). The not sequential portion of a curve
from Langmuir adsorption isotherm, and the plot of
[Carbodithioate] /i } vs [Carbodithioate] is a straight
ic √h is the average catalytic current. The diminish of
(
the peak height with the rise in mercury reservoir is
32
characteristic of CHSs as illustrated in Table 1.
{
P
line (Fig. 5), indicating the nature of CHSs.
Table 1: Effect of mercury pressure for the
analysis of chromium (VI) APP-CDT and ABP-CDT
S.No
Maximum
Current/μA
suppressor/% APP-CDT ABP-CDT
Gelatin
1
0.000
0.005
0.010
62.10
54.54
47.20
54.55
54.32
47.10
2
3
Trition X-100
1
2
3
0.000
0.002
0.004
61.20
55.64
53.86
57.54
49.52
46.42
Fig. 4. Effect of reagent concentration for the
analysis of Cr(VI) withAPP-CDT and ABP-CDT
Effect of maximum suppressors on peak height
The gelatine and Triton X-100 effects
ranging from 0.005 to 0.01% and 0.002 to 0.004%
was performed on the nature analyte signal in
NH Cl-NH OH buffer in the presence of CDT. The
4
4
peak height was reduced (20%) by adding 0.005%
gelatine with slight decrease in peak height.
However, increase in the gelatine concentration,
the peak potential shifts towards less negative. By
adding 0.002% Triton X-100 the CHSs were
decreased by 10%. Beyond 0.002% of Triton
X-100, the CHSs reduced marginally in both cases,
33, 34
suggesting the catalytic nature of the signals
illustrated in Table.2.
as
Fig. 5. Effect of Langmuir Adsorption Isotherm
Plot of Cr(VI) APP-CDT and ABP-CDT
Table 2: Effect of maximum suppressors for the analysis of chromium(VI)
APP-CDT and ABP-CDT
S.No
Height of the
mercury column/cm Current/μA
APP-CDT
ABP-CDT
/.A Current/μA
/μA
1
2
3
4
22
27
32
37
60.15
59.55
59.85
58.60
14.264
12.483
11.492
10.322
55.20
53.65
52.10
51.35
12.247
10.851
9.806
8.169

THONDAVADA et al., Orient. J. Chem., Vol. 34(2), 675-682 (2018)
679
Effect of temperature on peak height
The temperature effect was performed at
various temperature ranging from 15-40 C. It was
phosphate, thiosulphate, citrate, perchlorate and
sulphate do not impede with the CHSs of
chromium(VI)- CDT system. Though, carbonate and
EDTA affect gravely by suppressing the CHSs of
Cr(VI) as per they give rise to strong complexes
with the metal ion. Nitrite and nitrate give CHSs
with Cr(VI) in the absence of CDT also.
o
found that CHSs increased with the temperature,
however the temperature coefficient values
o
decrease until 30 C whilst i becomes temperature
c
30
o
independent beyond 30 C .
Effectofchromium(VI)Concentrationonpeakheight
Effect of indifferent cations
The indifferent cations effect was verified
at fixed pH, ligand and chromium (VI) and NH Cl-
The effect of concentration of chromium
(
VI) was carried out by varying 0.05-5.0 ppm for
4
APP-CDT and ABP-CDT respectively. The CHSs
increased proportionately with chromium (VI). The
linear bond attained within the CHSs and metal
ionconcentrationinalimitedrange(Fig. 6)isaspredicted
NH OH concentrations. In this study, sodium, alkali
4
chlorides, lithium and calcium were used. The
existence of these ions reduces the CHSs as
shown in Fig. 7-8. The obtained results suggested
that the calcium has stronger supressing effect on
the CHSs compared to other ions. The CHSs drops
constantly with increase in chloride ions
concentration. The sodium chloride effect was lower
than potassium chloride, with lithium chloride and
calcium chloride peak height decrease highly. In
all cases, with increase in chloride concentration
potential of the CHSs shifted to more negative
potentials. The decrease in CHSs due to indifferent
ions suggested the adsorption properties of
chromium(VI)-CDT complexes on the electrode
31
the nature of CHSs , and explored the feasibility of
detection of chromium(VI) in ultra-micro levels.
3
0, 32
surface
.
Fig. 6. Effect of chromium(VI) on peak current for
the analysis of chromium(VI) with APP-CDT and
ABP-CDT
Effect of foreign ions on the detection of Cr(VI)
Different metal ions effect on chromium
(VI) was carried out based on the CHSs. The CHSs
of the mixture comprising 4.0 ppm Cr(VI), in 0.4/0.5
M NH Cl at pH 8.6/7.8 for two ligands (3.0/4.0 mM
4
APP-CDT/ABP-CDT) as bonding agents. Metal ions
2
+
2+
2+
2+
2+
5+
such as Fe , Co , Ni , Mn , Cu , V in 100 fold
excess were recorded. Interestingly, it was found
2
+
3+
Fig. 7. Effect of Indifferent Ions on
APP-CDT-Cr(VI) complex
that Co oxidized to Co by atmospheric oxygen
was separated by bubbling of N gas and triggered
2
with CDTs. The resulted solid was removed and
filtrate was polarographed after nitrogen gas
5
+
bubbling. On the other hand, V slightly interfered
then disguised by addition of 2 ml 1% sodium
2
+
fluoride solution. Similarly, Ni also precipitate in
the pH range of Cr(VI)- CDT systems. The excipient
2
+
2+
2+
effect with other metals namely, Cd , Hg , Pb ,
3
+
+
6+
4+
+4
4+
4+
6+
Al , Ag , U , Se , Te , Ce , Sn and Mo was
studied. Amongst these metal ions, only Mo
enormously interfered as the CHSs of Mo was
attained even in the nonappearance of CDT. The
remarks were alike for two ligands. The other ions
such as bromide, fluoride, tartrate, iodide,
6
+
6
+
Fig. 8. Effect of Indifferent Ions on ABP-CDT-Cr(VI)
Complex

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THONDAVADA et al., Orient. J. Chem., Vol. 34(2), 675-682 (2018)
Chennai, India. All the samples were prior
Real sample applications
This technique is adopted to analysis concentrated to 100 ml for easy detection of analyte.
chromium(VI) in various environmental, biological The obtained results are tabulated in Tables 3-4.
and agricultural matrices. In this study, 1 L of each 10 g of Triticum aestivum (Wheat) and 5 g of Spinacia
environmental samples were brought from steel oleracea (Palaku) brought from vegetable market,
alloy industries situated at Gajulamandyam, Tirupati, Chittoor District and were processed by
Chittoor District, India. The leather wastewater was using dry method. The attained results are presented
sampled from tanning industries located near to in Tables 5-6.
Table 3: Analysis of chromium(VI) with APP-CDT in industrial runoffs around
Tirupati, (Industrial Estate) Chittoor District, A.P. India
CHSs method
Cr(VI)
Sample Added/ppm
(DC polarography)
APP-CDT
AAS method
APP-CDT
a
Cr(VI) Found
ppm
%Recovery
(R.S.D )
Cr(VI)Found %Recovery
b
b
/
/ppm
(R.S.D )
I
0.8
1.596
1.615
1.584
1.596
1.592
1.582
1.588
1.592
1.585
98.47(2.89)
98.14(2.30)
99.20(2.17)
99.35(2.11)
98.75(2.28)
97.54(2.52)
99.10(1.94)
97.93(2.94)
98.49(2.61)
1.582
1.604
1.584
1.582
1.592
1.575
1.596
1.582
1.595
99.24(1.92)
97.96(2.28)
98.52(2.26)
100.21(1.28)
98.35(2.45)
97.66(2.58)
99.75(2.33)
98.20(2.64)
100.50(1.28)
0
0
.8
.8
II
III
0.8
0
0
.8
.8
0.8
0
0
.8
.8
a5 ml of the sample is used, RSD (n=6)
b
I-Upper India Steel Ltd; II-Pioneer Alloy Casting Ltd; III- S.K.S Alloy Casting Ltd.
Table 4: Analysis of Chromium(VI) with ABP-CDT in industrial runoffs around
Tirupati, (Industrial Estate) Chittoor District, A.P. India
CHCSs method
Cr(VI)
Sample Added/ppm
(DC polarography)
ABP-CDT
AAS method
ABP-CDT
a
Cr(VI)Found
ppm
%Recovery
(R.S.D )
Cr(VI)Found
/ppm
%Recovery
(R.S.D )
b
b
/
I
0.8
1.486
1.495
1.526
1.568
1.542
1.582
1.586
1.595
1.594
97.85(2.34)
98.64(2.65)
98.95(2.42)
99.10(1.25)
99.50(1.90)
98.55(1.25)
98.10(2.24)
97.82(2.36)
100.15(1.45)
1.624
1.587
1.579
1.604
1.596
1.628
1.578
1.582
1.592
97.84(1.97)
99.36(2.10)
98.25(2.15)
99.56 (1.55)
98.92(2.46)
97.92(1.95)
99.64(2.26)
98.49(1.89)
97.82(1.96)
0
0
.8
.8
II
III
0.8
0
0
.8
.8
0.8
0
0
.8
.8
a
b
5
ml of the sample is used, RSD(n=6)
I-Upper India Steel Ltd; II-Pioneer Alloy Casting Ltd; III-S.K.S Alloy Casting Ltd.

THONDAVADA et al., Orient. J. Chem., Vol. 34(2), 675-682 (2018)
681
Table 5: Analysis of Chromium(VI) with APP-CDT in agricultural materials around
Tirupati, Chittoor District, A.P. India
CHSs method
Cr(VI)
Added/ppm
(DC polarography)
APP-CDT
AAS method
APP-CDT
a
Sample
Cr(VI)Found
ppm
%Recovery
(R.S.D )
Cr (VI)Found
/ppm
%Recovery
(R.S.D )
b
b
/
I
1.0
2.04
1.97
1.85
1.96
1.89
1.88
100.12(1.86)
99.62(1.92)
98.54(2.46)
99.18(1.95)
98.45(2.36)
98.36(2.24)
1.92
1.87
1.94
2.08
1.87
2.05
98.95(2.18)
98.65(2.42)
98.58(2.16)
100.15(2.28)
98.91(1.72)
100.26(1.84)
1
1
.0
.0
II
1.0
1
1
.0
.0
a
b
5
ml of the sample is used, RSD(n=6)
I –Triticum aestivum (Wheat); II- Spinacia oleracea (Palaku)
Table 6: Analysis of Chromium(VI) with ABP-CDT in agricultural materials around
Tirupati, Chittoor District, A.P. India
CHSs method
Cr(VI)
Added/ppm
(DC polarography)
ABP-CDT
AAS method
ABP-CDT
a
Sample
Cr(VI)Found
ppm
%Recovery
(R.S.D )
Cr(VI)Found
/ppm
%Recovery
(R.S.D )
b
b
/
I
1.0
1.94
1.99
2.15
1.97
1.89
2.04
98.10(2.45)
99.89(1.96)
100.15(1.82)
98.45(2.36)
98.74(2.35)
100.05(1.84)
1.99
1.97
1.98
1.95
1.96
1.98
99.00(2.35)
98.25(2.28)
97.95(2.12)
98.35(2.54)
99.20(2.38)
99.24(2.16)
1
1
.0
.0
II
1.0
1
1
.0
.0
a
b
5
ml of the sample is used, RSD(n=6)
I-Triticum aestivum (wheat); II-Spinacia oleracea (Palaku)
Table 7: Analysis of Chromium(VI) with APP-CDT and ABP-CDT in cow’s milk
Cr(VI)Found in samples, ppm*
Cow’s Milk
Cr (VI)
CHSs method
AAS Method
Added/ppm
(DC Polarography)
APP-CDT
ABP-CDT
APP-CDT
ABP-CDT
1
2
3
4
5
6
7
8
9
1
.
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.11(1.628) 1.13(1.532)
1.14(1.515) 1.09(1.715)
1.12(1.843) 1.11(1.418)
1.15(1.494) 1.159(1.662)
1.12(1.734) 1.14(1.483)
1.10(1.559) 1.12(1.813)
1.13(1.746) 1.14(1.449)
1.11(1.722) 1.16(1.682)
1.15(1.416) 1.15(1.496)
1.10(1.821) 1.12(1.773)
1.14(1.642)
1.12(1.524)
1.12(1.846)
1.16(1.482)
1.14(1.742)
1.13(1.542)
1.14(1.710)
1.12(1.749)
1.16(1.397)
1.13(1.827)
1.13(1.684)
1.10(1.588)
1.10(1.617)
1.13(1.489)
1.11(1.585)
1.12(1.8480
1.16(1.463)
1.15(1.632)
1.14(1.448)
1.13(1.747)
.
.
.
.
.
.
.
.
0.
1
ml of the sample is used
*RSD for 5 individual determinations

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THONDAVADA et al., Orient. J. Chem., Vol. 34(2), 675-682 (2018)
In a crucible, samples of milk was dropped (VI), outcomes of this study illustrated that
o
slowly and heated for one hour at 450 -500 C, chromium(VI) gives CHSs from Metal-CDT
without frothing moisture was vaporised. The ash
complexes. The sequential dependency of CHSs
on various parameters such as CDT’s concentration
and pH, suggested the catalytic nature of the signals
and involvement of adsorption process. The
variation of CHSs with as a function of mercury
reservoir height and chromium(VI) also indicated
the characteristics feature of catalytic signals. It was
demonstrated that the data fitted well into Langmuir
adsorption isotherm curve. It was concluded that by
collected was liquefied in 3 mL conc. HNO and
3
evaporated, and again liquified in the 3 mL of dilute
HNO . The obtained samples were filtered and
3
diluted to 25 mL in a flask for future experiments.
These samples were used to investigate
chromium(VI) and results are presented in Table.7.
CONCLUSION
A reliable, sensitive and reproducible using CHSs method, chromium(VI) detection is
CHSs method was established to detect chromium selective and reproducible.
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