Determination of Ni(II) with picolinaldehyde-4-phenyl-3-thiosemicarbazone used as a chromogenic reagent in a nonionic micellar system

Article abstract of DOI:10.3906/kim-1005-643

Spectrophotometric determination of Ni(II) was carried out using picolinaldehyde-4-phenyl-3-thiosemicarbazone (PAPT) as a complexing/chromogenic reagent. The possibility of using a micellar system was explored to enhance the degree of detection and allow a more sensitive spectrophotometric method for the determination of nickel ions. The anionic surfactant Triton X-100 greatly enhanced the molar absorptivity and limit of detection relative to that observed with bulk water or an organic solvent. The linear calibration graphs were obtained for 0.5-2.0 mg L-1 and 0.001-1.0 mg L -1 of Ni(II) in aqueous and surfactant media, respectively. Using this approach, the limit of detection for the PAPT-Ni(II) complex (based on 3σ of blank absorbance/slope) was found to be 0.0008 mg L -1 with a micellar enhancement reagent. The interference from over 50 cations, anions, and complexing agents was studied at 0.50 mg L -1 of Ni(II); most metal ions can be tolerated in considerable amounts in aqueous micellar solutions. TUeBITAK.

Full text of DOI:10.3906/kim-1005-643

Turk J Chem
5 (2011) , 925 – 937.
3
¨
˙
ꢀ
c TUBITAK
doi:10.3906/kim-1005-643
Determination of Ni(II) with
picolinaldehyde-4-phenyl-3-thiosemicarbazone used as a
chromogenic reagent in a nonionic micellar system
1
1,∗
1
Aamna BALOUCH , Muhammad Iqbal BHANGER , Farah Naz TALPUR ,
2
Willie L. HINZE
1
National Centre of Excellence in Analytical Chemistry, University of Sindh,
Jamshoro-PAKISTAN
e-mail: dbhanger2000@yahoo.com
2
Department of Chemistry (Salem-Hall), Wake Forest University,
Winston-Salem, NC-USA
Received: 31.05.2010
Spectrophotometric determination of Ni(II) was carried out using picolinaldehyde-4-phenyl-3-thiosemicar-
bazone (PAPT) as a complexing/chromogenic reagent. The possibility of using a micellar system was ex-
plored to enhance the degree of detection and allow a more sensitive spectrophotometric method for the
determination of nickel ions. The anionic surfactant Triton X-100 greatly enhanced the molar absorptivity
and limit of detection relative to that observed with bulk water or an organic solvent. The linear calibration
−
1
−1
graphs were obtained for 0.5-2.0 mg L
and 0.001-1.0 mg L
of Ni(II) in aqueous and surfactant media,
respectively. Using this approach, the limit of detection for the PAPT-Ni(II) complex (based on 3σ of blank
−
1
absorbance/slope) was found to be 0.0008 mg L
with a micellar enhancement reagent. The interference
−
1
from over 50 cations, anions, and complexing agents was studied at 0.50 mg L
can be tolerated in considerable amounts in aqueous micellar solutions.
of Ni(II); most metal ions
Key Words: Spectrophotometry, surfactant, Ni(II), PAPT
Introduction
1
−3
The toxicity of nickel is well known in causing asthma and cancer of the nose, lungs, and intestine
when
individuals are exposed to Ni-containing jewelry, cooking utensils, and clothing fasteners. Studies showed
∗
Corresponding author
9
25

Determination of Ni(II) with picolinaldehyde-4-phenyl-3-thiosemicarbazone..., A. BALOUCH, et al.
that the accumulation of Ni in the body may lead to lung fibrosis and cardiovascular and kidney diseases,
4
in addition to the most serious concerns related to nickel’s carcinogenic activity. It was confirmed that the
5
−6
tissues of cardiac patients had high levels of Ni, indicating its possible detrimental effects.
Therefore, trace
7
−9
analysis of nickel continues to be significant. Several researchers
have reported on the atomic absorption
spectroscopy (AAS) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) methods for nickel
determination; however, all such methods suffer from limitations including high cost, particularly in laboratories
1
0,11
with limited budgets in developing countries. Chemiluminescent methods
based on the catalytic action of
Ni(II) are subject to interference from various metal ions capable of activating or inhibiting the reactions.
Spectrophotometric methods also suffer from limitations in sensitivity and selectivity, but are still widely
used due to their rapidity and simplicity. Their selectivity and sensitivity depend on the type of reaction
1
2
and the chromogenic reagent used.
Picolinaldehyde-4-phenyl-3-thiosemicarbazone (PAPT) is a convenient
reagent reported for spectrophotometric determination of nickel and cobalt in mixtures and of nickel alone by
1
3,14
the extraction method with low sensitivity.
In addition, PAPT has been employed for the simultaneous
1
5
spectrophotometric determination of iron, vanadium, and cobalt in crude petroleum oil in an acidic medium.
1
3,16,17
However, metal- PAPT complexes are sparingly soluble in aqueous media,
necessitating the use of such
1
8,19
toxic organic solvents as chloroform, benzene, or carbon tetrachloride for the extraction step.
Metal ion determination through solvent extraction suffers from some inherent disadvantages, being
environmentally undesirable, expensive, and time-consuming, and often lacking selectivity and sensitivity. To
eliminate the need for organic solvents, aqueous micellar solutions can be utilized to solubilize insoluble chelating
2
0
agents along with their metal complexes, and they are compatible with many analytical techniques. Surfactant
solutions solubilize the species of interest, enhance the sensitivity of the analytical method by their catalytic
potential, and also offer many advantages, including low cost, environmental friendliness, and a high capacity
to concentrate a wide variety of analytes of varying nature with high recoveries and a high concentration
2
1−25
factor.
The aim of the present study was to develop a simple and selective spectrophotometric method for the
trace determination of nickel with PAPT reagent in the presence of nonionic micelles, such as polyoxyethylene
octyl phenyl ether (Triton X-100 [TX-100]), in aqueous solutions.
Experimental
Apparatus
All absorbance measurements were conducted using a PerkinElmer UV-Lambda 2 spectrophotometer.
A
Nicolet 5700 FT-IR spectrophotometer (Thermo Electron Corporation, MA, USA) with a total attenuated
reflectance accessory was employed for IR measurements. A WTW (Weilheim, Germany) pH meter with a
combination glass-Ag/AgCl electrode was used for the pH measurements. Elemental analysis was carried out on
a CHNS analyzer (Series 1112 FLASH, Thermo Electron Corporation). A HITACHI 180-50 atomic absorption
spectrophotometer (HITACHI, Tokyo, Japan) with an air-acetylene or nitrous oxide-acetylene flame was used
for comparison of our method with results obtained from AAS.
9
26

Determination of Ni(II) with picolinaldehyde-4-phenyl-3-thiosemicarbazone..., A. BALOUCH, et al.
Reagents, standards, and samples
All standard solutions were prepared from analytical-grade salts of respective materials. Ultrapure water
−
1
(
conductivity: 0.050 μS cm ) was obtained from a Milli-Q purification system (PURELAB Prima 7 BP,
PURELAB Classic UV) used for the preparation of all samples, standards and blanks. Glassware was cleaned
by soaking in acidified solutions of KMnO4 or K2 Cr2 O7 , followed by washing with concentrated HNO3 and
rinsing with water.
Synthesis procedure for picolinaldehyde-4-phenyl-3-thiosemicarbazone
1
4
The chelating agent, PAPT, was synthesized according to the reported method. Briefly, 0.01 mol (1.07 g)
of pyridine-2-carboxaldehyde was dissolved in 10.0 mL of methanol and mixed with a methanolic solution of
4
-phenyl-3-thiosemicarbazide (0.01 mol, 1.67 g). Next, 2.00 mL of concentrated acetic acid was added and the
◦
contents were refluxed for 30 min at 80.0 C. The mixture was cooled to room temperature and the yellowish
solid precipitate obtained was filtered, recrystallized from ethanol, dried, and stored in an amber bottle. The
◦
melting point of the solid was found to be 195.0 C, which is in good agreement with the reported literature
◦
26
value (196.0 C). Elemental analysis of the PAPT (C13 H12 N4 S) was as follows: calculated% C = 60.94,
H = 4.69, N = 21.88, and S = 12.50; found% C = 60.91, H = 4.65, N = 22.11, and S = 12.01. The FT-IR
−
1
spectrum exhibited major peaks at the following wave numbers (cm ): 3306.61 (υ N-H), 1595.41 (υ C=N),
548.3, 1523.03, 1497.35, 1467.39 (υ-ring breeding vibration of phenyl and pyridine), and 1187.07 (υ C=S).
1
Preparation of nickel ion standards solutions
−
1
Stock solutions (1000 mg L ) of nickel were prepared by dissolving the appropriate amount of nickel sulfate
Merck, Germany) in water acidified to a pH of approximately 5 with the addition of 2.00 mL of 0.001 M H2 SO4
(
and dilution to a final volume of 100.0 mL.
Preparation of surfactant solution
A 10% (v/v) solution of polyoxyethylene octyl phenyl ether (TX-100) was freshly prepared by dissolving 10.0
mL of pure polyoxyethylene octyl phenyl ether (Merck) in 30 mL of ultrapure deionized water sonicated for 15
min, then diluted up to the mark in a 100.0-mL volumetric flask.
Preparation of sodium hydroxide and sulfuric acid solution
A sodium hydroxide solution of 1.0 M was prepared by dissolving the appropriate amount in 40 mL of deionized
water, then increasing the volume up to the mark in a 100.0-mL volumetric flask with deionized water and
standardizing by the standard titration procedure. Less concentrated solutions were prepared by series dilution.
9
27

Determination of Ni(II) with picolinaldehyde-4-phenyl-3-thiosemicarbazone..., A. BALOUCH, et al.
Real sample digestion method
Chocolates and candies
The chocolate and candy samples were digested by the conventional digestion method (CDM) for nickel analysis.
About 0.5 g of each selected sample, 1 of each chocolate and candy (n = 3), was weighed in separate Pyrex
flasks (50 mL in capacity) and the contents of the flasks were treated with a mixture of HNO3 , H2 SO4 , and
H2 O2 (1:1:1, v/v/v) for decomposition.
◦
The contents of the flasks were heated on an electric hotplate at 80 C for 2-3 h, until clear. After the
cooling of the digestion flask, the resulting solutions were evaporated until semidried, and then 5.0-8.0 mL of
water was added and the pH of the solution was adjusted to approximately 7 by the addition of 0.01 M NaOH.
The final volume was increased to 25.0 mL. An aliquot of 0.5-2.0 mL was then taken and analyzed for its nickel
contents.
Water samples
Water samples were collected from Manchar Lake, Sindh, Pakistan, and from a domestic tap. In both cases
1
00.0 mL of each water sample was filtered with Whatman No. 40 filter paper and evaporated to near dryness.
In order to dissolve the salts 5.0 mL of concentrated HNO3 and 10.0 mL of water were added and the solution
was heated in a fume hood. The solution was cooled and neutralized with 0.01 M NaOH solution. The resulting
solution was then filtered and quantitatively transferred to a 25.0-mL volumetric flask and diluted to the mark
with water. An aliquot (1.02.0 mL) of this solution was pipetted into a 10.0-mL calibrated flask and the nickel
content was determined.
Experimental procedures for calibration data
Slightly acidic solutions (pH of approximately 5.00) containing 0.50-100.0 μg of nickel ion were added to 10.0-
mL volumetric flasks followed by the addition of 2.00 mL of 0.05% (w/v) PAPT solution in dimethylformide
and 0.10 mL of 0.01 M NaOH (pH of approximately 10-11), and then diluted to a final volume with 10% (v/v)
TX-100 solution. After mixing the solution, the absorbance of the metal-PAPT complex was measured versus
an appropriate blank solution within 10-15 min at 430 nm.
Results and discussion
Absorption spectra
The absorption spectra of PAPT and its nickel complex in the micellar solution are shown in Figure 1. Maximum
absorbance of the PAPT-Ni(II) complex was observed at 390 nm in acetic acid-acetate buffer and at 400 nm in
1
3
chloroform; however, in the aqueous TX-100 micellar solution, the wavelength maximum bathochromically
shifted to 430 nm.
9
28

Determination of Ni(II) with picolinaldehyde-4-phenyl-3-thiosemicarbazone..., A. BALOUCH, et al.
1
0
0
.0
.8
.6
A
B
C
A 0.4
0
0
.2
.0
PAPT-Blank
D
-0.1
3
80
400
420
440
460
480 500
nm
520
540
560
580
600
Figure 1. Absorption spectra of PAPT-Ni(II) complex in micellar solution (curve A); PAPT-Ni(II) complex in acetic
acid-acetate buffer (curve B); PAPT-Ni(II) complex in chloroform extract (curve C); and reagent blank (curve D) in
1
−
TX-100. Conditions: final Ni(II) ion concentration was 0.50 mg L ; [PAPT] = 0.001171 M, [TX-100] = 1.0% (v/v);
◦
pH = 10.2 at 25 C.
Factors influencing the chelating reaction and metal complex
To optimize the conditions for determination of Ni(II), such factors as pH, surfactant type and concentration,
reagent concentration, and composition of complexes were evaluated.
Effects of surfactants
In the absence of surfactants, the chromogenic system gives a low analytical signal. To enhance the absorption
(i.e., molar absorptivity), the effects of various surfactants on the PAPT-Ni(II) chromogenic system were
examined. The order of the absorbance was TX-100 > Brij35 > Tween 80 > cetyltrimethylammonium bromide
(CTAB), as illustrated in Figure 2. The absorbance of PAPT-Ni(II) increases considerably in the presence of
1
3
a nonionic surfactant, which is attributed to the uncharged complex in basic media, as reported previously.
However, when anionic surfactant sodium dodecyl sulfate (SDS) was added, the solution turned turbid and the
absorbance of the PAPT-Ni(II) complex was difficult to measure.
Figure 3 shows the effect of surfactant concentration on the absorbance of the PAPT-Ni(II) complex. A
solution of 1.0 mL of 10% (v/v) TX-100 gave a constant and maximum absorbance, which was used for further
study.
Effect of pH
The color of the nickel complex had a maximum intensity in the basic medium at a pH greater than 10:
++
+
Ni(HPAPT)2 Ni(PAPT)2 + 2H .
9
29

Determination of Ni(II) with picolinaldehyde-4-phenyl-3-thiosemicarbazone..., A. BALOUCH, et al.
0
0
0
.6
.5
.4
1
.9
.8
.7
.6
.5
.4
.3
.2
.1
0
0
0
0
0
0
0
0
0
0
0.3
0
0
.2
.1
0
PAPT
TX-100
Brij35
CTAB
Twe e n
0
1
2
3
4
8
0
Type of surfa cta nt
TX-100, %
Figure 2. Effect of surfactant type on the absorbance
Figure 3. Effect of TX-100 concentration on the ab-
of PAPT-Ni(II) complex and water alone. Conditions:
1
sorbance of PAPT-Ni(II) complex. Conditions: final
−1
−
final Ni(II) ion concentration was 0.50 mg L ; [PAPT] =
Ni(II) ion concentration was 0.50 mg L ; [PAPT] =
◦
0.001171 M, [CTAB] = 0.06 M, [TX-100] = 2%, [Brij35]
0.001171 M; pH = 10.2 at 25 C.
◦
=
1%, [Tween 80] = 1%; pH = 10.2 at 25 C.
Experimental results demonstrated that the optimal reaction pH value for nickel with PAPT was 10.2 in
a micellar system, as shown in Figure 4.
Effect of chelate (PAPT) concentration
−
1
The PAPT reagent concentration was varied under otherwise identical conditions (0.50 mg L
metal ion, 0.001
M NaOH, 1.0 mL of 10% TX-100 (v/v)). Figure 5 shows the effect of the reagent PAPT concentration on the
absorbance of the PAPT-Ni(II) complex within a range of from 7.8 × 10− to 2.3 × 10
5
−3
M. An increase in
−
4
−3
reagent concentration enhanced the absorbance up to a concentration of from 3.9 × 10
to 1.5 × 10
M,
−
3
after which a decrease was observed. For up to 10 mg of Ni(II), 1.5 × 10
for complete reaction. Therefore, a final PAPT concentration of 1.5 × 10
M reagent solutions were enough
M was selected as optimum and
−
3
utilized in the recommended procedure.
Stability of the chromogenic system
The absorbance of the PAPT–Ni(II) chromogenic system reaches a maximum value within 10 min at room
temperature and remains stable for at least 24 h. The temperature did not affect the stability of the complex
◦
at up to 50 C.
Calibration graph and sensitivity
−
1
The effect of metal concentration was studied over 0.001-1.0 mg L , distributed in 2 different sets (0.001-
−
1
0
.10 and 0.10-1.0 mg L ) for convenience of measurement. The calibration graph (Figures 6a and 6b) was
9
30

Determination of Ni(II) with picolinaldehyde-4-phenyl-3-thiosemicarbazone..., A. BALOUCH, et al.
0
0
0
0
0
.45
.4
.35
.3
.25
.2
.15
.1
0
0
0
0
0
0
.6
.5
.4
.3
.2
.1
0
0
0
0
0
.05
0
0
0.001
0.002
0.003
0.004
0
0.0005
0.001
0.0015
0.002
0.0025
NaOH [M]
PAPT [M]
Figure 4. Effect of NaOH concentration on the ab-
Figure 5. Effect of reagent (PAPT) concentration on the
sorbance of PAPT-Ni(II) complex. Conditions: final
−
absorbance of PAPT-Ni(II) complex. Conditions: final
−1
1
Ni(II) ion concentration was 0.50 mg L ; [PAPT] =
Ni(II) ion concentration was 0.50 mg L ; [TX-100] =
◦
◦
0
.001171 M, [TX-100] = 1.0% (v/v); pH = 10.2 at 25 C.
1.0% (v/v); pH = 10.2 at 25 C.
1
1
.4
.2
1
y = 0.9873x + 0.32
0
0
0
0
0
0
.6
.5
.4
.3
.2
.1
0
2
R
= 0.9947
y = 3.9975x + 0.083
2
R
= 0.9962
0
0
0
0
.8
.6
.4
.2
0
0
0.02
0.04
0.06
0.08
0.1
0.12
0
0.2
0.4
0.6
Ni [m g/L]
0.8
1
1.2
Ni [m g /L]
Figure 6a. Linear calibration graph from 0.001 to 0.1 mg
Figure 6b. Linear calibration graph from 0.1 to 1.0 mg
−
1
−1
L
of Ni(II). Conditions: [PAPT] = 0.001171 M, [TX-
◦
L
of Ni(II). Conditions: [PAPT] = 0.001171 M, [TX-
◦
1
00] = 1.0% (v/v); pH = 10.2 at 25 C.
100] = 1.0% (v/v); pH = 10.2 at 25 C.
−
1
constructed following the general procedure. The absorbance was linear for 0.5-2 mg L
and 0.001-1.00 mg
−
1
L
of Ni(II) in organic and surfactant media, respectively. The linear regression equation was A = 3.9877CNi
−
1
+
=
0.0837 with a correlation coefficient of r = 0.9975 for the concentration range of 0.001-0.1 mg L
and A
−
1
0.9873CNi + 0.32 with a correlation coefficient of r = 0.9962 for the concentration range of 0.1-1.0 mg L
−
1
of nickel, where A = absorbance and CNi = the concentration of Ni(II) in mg L . Beer’s law was obeyed in
9
31

Determination of Ni(II) with picolinaldehyde-4-phenyl-3-thiosemicarbazone..., A. BALOUCH, et al.
−
1
the range of 0.001-1.00 mg L
of Ni(II). From the slope of the calibration graph, the molar absorptivity for
5
5
−1
−1
PAPT-Ni(II) in TX-100 was found to be 2.41 × 10 and 5.79 × 10 L mol
cm
in its absence, under optimized conditions.
The limit of detection for the PAPT-Ni(II) complex (based on 3σ of blank absorbance/slope) was found to be
for 0.001-0.1 and 0.1-1.0
−
1
4
−1
−1
mg L , respectively, as compared to 3.0 × 10 L mol
cm
−
1
0
.0008 mg L
using the micellar enhancement reagent. The optimized parameters are summarized in Table
1
. This proposed PAPT method is simple and rapid (nonextractive), convenient, and more selective relative to
2
5,27−31
the existing spectral absorption methods
for the determination of nickel.
Table 1. Analytical parameters obtained after optimization.
1
3
Selected parameter
pH
Micellar system
Organic system
8-9
10-12
Surfactant
TX-100, 1.0% (v/v)
Chloroform
0.0039
0.025
Reagent (PAPT) M
Reagent (PAPT) %
Time for reaction, min
0.001171
0.0075
10
20-40
10-15
◦
Temperature C
25
−
1
1
0
.001-0.1 mg L
Abs = 0.9873C + 0.32
Abs =3.9975C + 0.083
430
NR*
Calibration equation
−
1
0
.1-1.0 mg L
NR*
Wave length (nm)
400
−
1
Linear range (mg L
)
0.001-1.0
0.5-2.0
−
0
.001-0.1 mg L
0.9962
Regression of calibration
NR*
−
1
0
.1-1.0 mg L
0.9947
*NR: not reported
Determination of PAPT-Ni(II) complex stoichiometry
3
2
Job’s method of continuous variation was applied for identifying the composition of the predominant complex.
Equimolar 1 × 10− M solutions of nickel and PAPT were prepared and the classical procedure followed. The
composition of the PAPT-Ni(II) complex was found to be 2:1.
4
Interference study
−
1
The interference study was performed by analyzing fixed concentrations of Ni(II) (0.50 μg mL ) in the presence
and absence of different concentrations of each interfering ion. The reagent PAPT is a nonselective photometric
reagent; its selectivity is improved by the selection of an appropriate pH (i.e., alkaline media). In addition,
whereas the absorption maxima of many metal ions with PAPT complexes are at 410 nm, the PAPT-Ni(II)
−
1
complex absorbs at 430 nm. The tolerance limits were taken as the concentration in mg L
causing a relative
error of 5% or less in the concentration of analyte. The tolerance limits for all ions examined are given in Table
2
9
. A number of cations do not interfere, even when present at 50- to 100-fold excess in concentration.
32

Determination of Ni(II) with picolinaldehyde-4-phenyl-3-thiosemicarbazone..., A. BALOUCH, et al.
Table 2. Effect of foreign species on proposed determination of nickel ion.
Species
Tolerance ratio
−
1
(
folds per mg L
)
I, PO4 , SCN
1000
250
Oxalate, Fe(II)/(III), Co(II)
Azide, Be(II), Br, F
3
4
−
PO
200
100
3
3
−
2+
Al(III), AsO , ascorbic acid, Ba
CO3-, Cl-, NO3
2
−
+
Tartrate, SO , sulfide, Sb(III), Ag
4
2
+
Ca , Cr(III&VI)
Ce(III&IV), Mn(II&VII), Mg(II), W(VI)
+
Zn(II), Ga(III), Au(III), K
+
Se(II), Na , Hg(II)
Pb(II), Mo(VI), Pd(II), Sn(II), Tl(I), Cu(II)
Cd(II), In(III), 1,10-phenonthroline
EDTA
50
25
−
1
Conditions: Final Ni(II) ion concentration was 0.50 mg L ; [PAPT] = 0.001171 M, [TX-100] = 1.0% (v/v); pH = 10.2
◦
at 25 C.
Applications
Determination of Ni (II) in water and synthetic samples
In order to test the applicability of the proposed method to the analysis of real samples, the method was applied
to Ni(II) ions in environmental water samples collected from Manchar Lake and a domestic tap. Spiked samples
were analyzed by the proposed method and the results are summarized in Table 3. A synthetic mixture was also
prepared to validate the method in the presence of all ions mentioned in Table 4 and to calculate the percentage
recovery. EDTA was added to assess whether it masked the Ni(II) ion to form a complex with PAPT or not,
but the excellent percentage recovery showed that it did not affect the complexation between Ni(II) and PAPT.
Results of the analysis of the synthetic mixtures are shown in Table 4.
−
1
Table 3. Determination of nickel in water sample (μg L , n = 3).
Samples Sample source Added
Ni
34.3
37.7
0.0
Recovery (%) ± SD
96 ± 5.3
S1
Lake water
0.0
.0
0.0
.0
5
S2
Tap water
104 ± 4.2
5
5.2
9
33

Determination of Ni(II) with picolinaldehyde-4-phenyl-3-thiosemicarbazone..., A. BALOUCH, et al.
Table 4. Determination of nickel in synthetic mixture.
−
1
−1
Composition of mixtures, mg L
Ni(II), mg L
Added Found
Sample
A
Recovery (%)
−
1
(
20 mg L for all added metal ions)
2
+
Ni
0.50
.80
0.50
.00
0.50
.00
0.49
0.80
0.5
98 ± 0.5
100 ± 0.0
100 ± 0.0
98 ± 0.5
98 ± 0.6
100 ± 0.0
0
2
+
2+
B
C
D
E
Ni + Ca + Na + K
1
0.98
0.49
1.00
0.52
0.97
0.51
0.95
2
+
2+
3+
Ni + Ca + Na + K + Cr + Ba + Pb
1
2
+
2+
3+
Ni + Ca + Na + K + Cr + Ba +
0.50
1.00
0.50
1.00
3
3
−
Pb + Mg + AsO + NO3
3+
97 ± 1.8
100 ± 1.8
100 ± 1.8
2
+
2+
Ni + Ca + Na + K + Cr + Ba + Pb + Mg +
3
3
−
2+
AsO + NO3 + Mo(VI) + Sn + EDTA (200)
Determination of Ni(II) in food samples
Nickel ions were analyzed in food samples such as chocolate, candy, soft drinks, and juices that were obtained
from a local market in Hyderabad. The results of the analyses are summarized in Table 5. Nickel ion was
successfully determined in all food samples by the proposed method with an acceptable standard deviation
−
1
(
0.02-0.35 mg L ). The results obtained by the proposed method were compared to those obtained from
atomic absorption analysis. The major source of Ni in chocolate may be the use of hydrogenated vegetable oil
for its preparation.
Table 5. Determination of nickel in food samples.
a
b
Samples
Ni %RSD
Ni (AAS) %RSD
−
1
Juice and soft drink (mg L
)
S1
S2
S3
S4
0.455 ± 0.058
0.102 ± 0.020
0.383 ± 0.036
0.095 ± 0.011
0.192 ± 0.093
0.075 ± 0.007
0.253 ± 0.120
0.145 ± 0.031
Chocolate and candy (μg g
−
1
)
S1
S2
S3
5.12 ± 0.35
3.89 ± 0.25
2.02 ± 0.18
4.33 ± 0.25
3.55 ± 0.22
1.45 ± 0.13
%RSD: Relative standard deviation.
a
Determined by proposed method (n = 3).
b
Determined by atomic absorption spectrophotometry (n = 3).
9
34

Determination of Ni(II) with picolinaldehyde-4-phenyl-3-thiosemicarbazone..., A. BALOUCH, et al.
Table 6 compares the analytical parameters for various reported spectrophotometric methods and the
proposed method for the determination of Ni(II), showing the superiority of the present method over existing
methods.
Table 6. Comparison of some spectrophotometric determination methods for nickel.
Linear
−
1
−1
Reagent
Medium/
solvent
Interfering
ions
λmax ε, M cm
range,
Ref
27
−
1
nm
μg mL
Cu(II), Co(II),
Pd(II), Ag(I),
Zn(II), Fe(II)
Cu(II), Co(II),
Ti(IV)
4
5
-Me-BTAMB
Aqueous, SDS
640
13.2 × 10
0.0-0.4
4
4
6
-Me-BTAMSB
QADP
Aqueous, SDS
Chloroform
620
574
8.22 × 10
12.4 × 10
0.0-0.6
28
29
Cu(II), Co(II),
Cd(II), V(V) )
Zn(II), Fe(III
Cu(II),Co(II),
Pd(II),Mn(II),
Zn(II), Fe(III)
Co(II), Ag(I)
Co(II)
0.04-0.72
0.1-1.0
4
PANS
Chloroform
570
5.6 × 10
30
4
QADEAA
PAN
Aqueous, SDS
595
569
13.8 × 104
4.62 × 10
0.01-0.40
0.03-1.80
31
21
Aqueous, Tween 80
Co(II), Cd(II),
V(V), Zn(II),
Fe(III)
4
PAPT
PAPT
Chloroform
TX-100
400
430
2.7 × 10
0.8-2
13
5
2
5
.41 × 105
.79 × 10
0.001-0.1
0.1-1.0
No interference
This work
5
-Me-BTAMB: 2-[2-(5-methylbenzothiazolyl)azo]-5-dimethylaminobenzoic acid
-Me-BTAMSB: [2-(6-methylbenzothiazolyl)azo]-5-N-ethyl-N-sulfomethyl) aminobenzoic acid
6
QADP: 2-[2-(4-methylquinolyl)azo]-5-diethylaminophenol
PANS: 1-(2-pyridylazo)-2-naphthol-6-sulfonic acid
QADEAA: 2-(2-quinolylazo)-5-diethylaminoaniline
PAN: 1-(2-pyridylazo)-2-naphthol
PAPT: picolinaldehyde-4-phenyl-3-thiosemicarbazone
Conclusion
A simple, economical, and environmentally friendly spectrophotometric method for the trace determination of
nickel is described here; it is more sensitive than the existing spectral methods. The molar absorptivity for
5
5
−1
−1
PAPT-Ni(II) in TX-100 was found to be 2.41 × 10 and 5.79 × 10 L mol
cm
for 0.001-0.1 and 0.1-1.0
−
1
4
−1
−1
mg L , respectively, as compared to 3.0 × 10 L mol
cm
in its absence. The use of aqueous TX-100
9
35

Determination of Ni(II) with picolinaldehyde-4-phenyl-3-thiosemicarbazone..., A. BALOUCH, et al.
solution not only serves to remove the need for organic solvents but also enhances the analytical signal and
consequently the sensitivity of method. With the use of a micellar system, less of the PAPT chelating reagent is
required. The method is applicable to complex matrices and serves as a single-step, quick method that requires
no clean-up process for interfering ions.
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