Şerife SAÇMACI et al.
444 Bull. Korean Chem. Soc. 2011, Vol. 32, No. 2
DOI 10.5012/bkcs.2011.32.2.444
Novel Solid Phase Extraction Procedure for Some Trace Elements
in Various Samples Prior to Their Determinations by FAAS
Şerife SAÇMACI,* Şenol KARTAL, Mustafa SAÇMACI,† and Cengiz SOYKAN†
Erciyes University, Department of Chemistry, Faculty of Arts and Sciences, TR-38039, Kayseri, Turkey
*
E-mail: sacmaci@erciyes.edu.tr
†
Bozok University, Department of Chemistry, Faculty of Arts and Sciences, 66200, Yozgat, Turkey
Received August 3, 2010, Accepted November 25, 2010
A novel method that utilizes poly(5-methyl-2-thiozyl methacrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic
acid-co-divinylbenzene) [MTMAAm/AMPS/DVB] as a solid-phase extractant was developed for simultaneous preconcentration of trace Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Ni(II), Pb(II), and Zn(II) prior to the measurement by
flame atomic absorpiton spectrometry (FAAS). Experimental conditions for effective adsorption of the metal ions were
optimized using column procedures. The optimum pH value for the simultaneously separation of the metal ions on the
new adsorbent was 2.5. Effects of concentration and volume of elution solution, sample flow rate, sample volume and
interfering ions on the recovery of the analytes were investigated. A high preconcentration factor, 100, and low relative
1
standard deviation values, ≤ 1.5% (n = 10), were obtained. The detection limits (µg L‒ ) based on the 3s criterion were
0.18 for Cd(II), 0.11 for Co(II), 0.07 for Cr(III), 0.12 for Cu(II), 0.18 for Fe(III), 0.67 for Mn(II), 0.13 for Ni(II), 0.06 for
Pb(II), and 0.09 for Zn(II). The validation of the procedure was performed by the analysis of two certified reference
materials. The presented method was applied to the determination of the analytes in various environmental samples
with satisfactory results.
Key Words: Chelating resin, Separation, Preconcentration, Trace element, FAAS
Introduction
The determination of metal ions at trace level is very important in the context of environmental protection, food and agricul1
tural chemistry, and high purity materials. The release of heavy
metals into the environment is a potential threat to water and
soil quality as well as to aquatic life and human health. Moreover, metal ions do not degrade biologically like organic pollutants, their presence in industrial effluents or drinking water is
a public health problem due to their ingestion and therefore
2,3
possible accumulation in living organisms. For the determination of trace elements in environmental samples, inductively
coupled plasma-atomic emission spectrometry (ICP-AES),4,5
6
inductively coupled plasma-mass spectrometry (ICP-MS) and
7,8
atomic absorption spectrometry (AAS) are the most widely
used techniques for analyzing these harmful metal ions. They
are usually insufficient due to matrix interferences and very low
concentrations of metal ions. Therefore, a separation/preconcentration step is required.8
Solid phase extraction is an extraction method that uses a
solid phase and a liquid phase to isolate one, or one type, of analyte from a solution. Also, this method had the advantages of
being more sensitive, simple environment friendly, faster and
sampler saving. It has known as a powerful tool for separation
and preconcentration of various inorganic and also organic
8,9
analytes.
Among the various seperation and preconcentration techniques proposed up to now, solid phase extraction using a chelate
resin is one of the most practical ways to satisfy these requirements.10-12 Therefore, a variety of chelating resins have been
studied from the viewpoint of the effective and/or selective
adsorption of elements.3 Much attention has been drawn to the
synthesis of chelating resins and to the investigation of their
adsorption behavior for the selective and quantitative separation
of specific metal ions from various matrices, because both their
adsorption ability and adsorption selectivity are superior to those
of ion exchangers in a trace and/or ultra trace concentration
range. Chelating resins are typically characterised by functional
groups containing O, N, S and P donor atoms which coordinate
to different metal ions.13-15
Crosslinked copolymers containing 2-acrylamido-2-methyl1-propanesulfonic acid functional groups (AMPS) have a great
potential for many applications as ion-exchange resin and gas
separation membrane in the water purification industry, and
for monitoring heavy metals in various environmental samples.
Chelating resins are superior for selectivity in solid phase extraction and ion exchange due to their triple functions, i.e., ion
exchange, chelate formation and physical adsorption. Chelating
and/or ion exchange type adsorbents used in speciation studies
have shown a preferential affinity for a single oxidation state
of metal. The chelating resin adsorbents, which have large specific surface areas and high adsorption rates, are increasingly
used in removal and preconcentration of toxic metal ions from
aqueous solutions. The adsorption of heavy metal ion from
aqueous solution to adsorbent is usually affected by the surface
functional groups of the adsorbent.16
Poly(5-methyl-2-thiozylmethacrylamide-co-2-acrylamido2-methyl-1-propanesulfonic acid-co-divinylbenzene) (MTMAAm/AMPS/DVB) resin includes a thiazole cycle. Thiazole
and its derivatives have biological significance, e.g., they are
found in the vitamin B1 molecule and coenzyme cocarboxylase.17 Various thiazole derivatives have shown herbicidal,
Novel Solid Phase Extraction Procedure
Bull. Korean Chem. Soc. 2011, Vol. 32, No. 2
18
anti-inflamatory, anti-microbial, and/or anti-parasitic activity.
Therefore, this resin seems to be a suitable candidate for further
chemical modifications.
In this work, poly(5-methyl-2-thiozyl methacrylamide-co-2acrylamido-2-methyl-1-propanesulfonic acid-co-divinylbenzene) as a new chelating resin for the separation/preconcentration of the metal ions has been proposed. The analytical conditions for the quantitative recoveries of the analyte ions including
pH, amounts of the resin, sample volume, etc. were investigated.
According to our literature knowledge, there is no any study
for separation/preconcentration of the analytes by using this
chelating resin. We here report the usefulness of the chelating
resin to separate and concentrate the metal ions in environmental
samples. The new adsorbent has been used for the separation and
preconcentration of trace Cd(II), Co(II), Cr(III), Cu(II), Fe(III),
Mn(II), Ni(II), Pb(II), and Zn(II) ions occurring in water, soil
and food samples prior to their determinations by FAAS.
Experimental
Instrument. A PerkinElmer model AAnalyst 800 flame atomic absorption spectrometer (Norwalk, CT, USA) equipped
with a deuterium background correction system and an airacetylene burner was used for the determination of all the metal
ions. The operating conditions adjusted in the spectrometer
were carried out according to the standard guidelines of the
manufacturer. A Consort model C533 pH meter with a combined
pH glass-electrode was employed for measuring pH values in
the aqueous phase.
Reagents and Solutions. Distilled deionized water (DDW)
was used throughout the experimental works. All the reagents
used were of analytical grade. High purity reagents purchased
from Merck (Darmstadt, Germany) were used for preparation
of all the stock solutions. Standard stock solutions of Cd(II),
Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Ni(II), Pb(II), and Zn(II)
(1,000 mg L‒1) were prepared by dissolving their nitrate salts
‒1
in distilled deionized water with the addition of 1 mol L HNO3
and further diluted daily prior to use. The calibration standards
were not submitted to the separation-preconcentration procedure. All the plastic and glassware were cleaned by soaking in
dilute HNO3 (1+1) and rinsed with distilled deionized water
prior to use.
The chelating resin, MTMAAm/AMPS/DVB, was synthesized as reported in the literature.16 The synthesized polymer was
washed successively with 1 mol L‒1 HNO3, NaOH, ethyl alcohol
and distilled deionized water. Then the chelating resin was dried
in an oven at about 60 oC. A glass mini column containing 0.5 g
of the resin in water suspension has 10 cm length and 1.0 cm in
diameter. The resin bed height in the column was approximately
1.0 cm. A small amount of glass-wool was placed on the top of
the resin to avoid disturbance during the sample passage. The
mini column was washed thoroughly with distilled water and
then pre-conditioned at the working pH 2.5 using acetic acid/
sodium acetate buffer solution before passing the solutions
containing the analyte ions.
Synthesis of the Chelating Resin. Firstly, 5-methyl-2-thiozyl
methacrylamide (MTMAAm) monomer was synthesized. For
doing this, to a well-stirred solution of 2-amino-5-methylthia-
H3C
SO 3H
S
CH2
N
C
H3C
HN
C
-
CH2
O
C
C
H
CH2
C
CH3
CH2
O
C
C
CH2
H
C
C
O
HN
NH
H3C
-
H
C
C
O
C
CH2
H
CH2
CH3
NH
CH3
-
445
CH3
CH2
SO 3H
N
S
CH3
Figure 1. The structure of the polymer resin.
zole and triethylamine in dichloromethane, methacryloyl chloride was added dropwise under cooling conditions (0 - 5 oC).
After the complete addition of methacryloyl chloride, the reaction mixture was stirred for 12 h at room temperature, then
filtered and evaporated with a rotavapor. A yellow product was
obtained and recrystallized from ethanol as a yellow powder.
The preparation of MTMAAm/AMPS/DVB resin was carried
out with a radical initiator in dimethylformamide solution. To
a polymerization flask, the two appropriate monomers MTMAAm and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), the crosslinking reagent divinylbenzene (DVB), and the
initiator azobisisobutyronitrile (AIBN) were added. The system
o
was kept under nitrogen for 3 h at 70 C. Subsequently, the resin
was filtered and washed with abundant diethylether and dried
under vacuum at 50 oC until a constant weight was obtained. The
conversion of the monomer to the polymer resin was determined
gravimetrically (yield, 80%).16 The structure of the polymeric
resin is illustrated in Fig. 1.
General Procedure for Preconcentration. The preconcentration procedure was tested with the model solutions containing
known amounts of the metal ions before application to real samples, and percentage recoveries were calculated. For doing this,
25 mL of the model solution containing the analytes was adjusted to the pH 2.5 using 2 mL of acetic acid/sodium acetate buffer
solution and the sample solution was loaded to the column. The
flow of the sample solution through the mini column was gravitationally performed at a flow rate of 6.0 mL min‒1. The flow rate
of the sample solution was controlled by using the stopcock of
the mini column. After being completed the passing of the
sample solution, the column was washed with a small amount
of distilled water. Then, the retained metal ions were eluted from
the column by the aid of 10 mL of 2 mol L‒1 HCl at a flow rate of
6.0 mL min‒1. The metal ion concentrations in the eluate solution
were determined by the flame atomic absorption spectrometry
(FAAS).
Analysis of Real Samples. A 0.1 g of soil sample was put into
Şerife SAÇMACI et al.
Bull. Korean Chem. Soc. 2011, Vol. 32, No. 2
a 100 mL of beaker and a mixture of 6 mL of HCl (37%, w/w)
and 2 mL of HNO3 (65%, w/w) was added and the digestion was
performed on a hot plate adjusted to 200 oC. 1.0 g of each of
black tea, cinnamon and dill samples, 0.5 g of INCT-TL-1 tea
leaves certified reference material were digested with a mixture
of 6 mL of concetrated HNO3 and 2 mL of H2O2 solutions. After
the digestion, the suspension obtained from soil samples was
filtered through a blue ribbon filter paper and completed to 50
mL with distilled deionized water. The resulting clear solutions
from the plant samples were completed to 50 mL with distilled
deionized water. Analyses for blank samples were carried out
in the same way without sample. Then the preconcentrationseparation procedure given above was applied to the obtained
solutions. After the preconcentration step, the final measurement volumes were completed to 5 mL, and the solutions were
measured by FAAS.
The proposed preconcentration procedure was also applied
to SPS-WW2 Batch 108 certified reference material (10 mL),
tap water, lake water, waste water and rain water samples (1000
mL). The natural water samples were filtered through Millipore
cellulose membrane filters (0.45 µM pore size, 47 mm diameter). The other processes for analyzing these water samples
were the same just mentioned above.
Results and Discussion
Effect of pH. The pH is a very important factor for chelate
formation in solid phase extraction processes for the purposes
of separation and preconcentration. In order to find the optimum
pH, the effect of pH on the preconcentration of the metal ions
using the chelating resin was investigated. For this purpose,
25 mL of model solution including 20 µg of Cr(III), Fe(III) and
Pb(II), 10 µg of Mn(II), Co(II), Ni(II) and Cu(II), 5 µg of Cd(II),
and 2 µg of Zn(II) was used in the pH range of 1-10 by adjusting
with buffer solutions. The retained ions were eluted by 10 mL of
2 mol L‒1 HCl. The analyte ions in the eluate were determined
by FAAS. The results are shown in Fig. 2. The analyte ions were
quantitatively recovered in the pH range of 1.5 - 4. According
to the results, the optimum pH was 2.5 for the purpose of multielement separation/preconcentration. So, the pH 2.5 has been
chosen as the separation/preconcentration acidity for the subsequent studies.
Effect of Type, Concentration and Volume of Eluent. For the
elution of the trace metals adsorbed on the chelating resin, dilute
acid solutions having different concentrations and volumes
were investigated. For this reason, various elution solutions
were used for desorption of the trace metals from the chelating
resin. The results are given in Table 1. It was found that 10 mL
of 2 mol L‒1 HCl was sufficient for complete elution of all the
metal ions studied. Therefore, 10 mL of 2 mol L‒1 HCl solution
was used as eluent in further experiments.
Effect of Flow Rate of Sample. The effect of the flow rate of
sample solution was examined under the optimum conditions
‒1
(pH 2.5, eluent: 10 mL of 2 mol L HCl). The influences of the
sample flow rate on the recoveries of the metal ions were investigated in the range of 1.0 - 10.0 mL min‒1. The flow rates were
adjusted with the aid of the stopcock of the column. The results
are given in Fig. 3. For the flow rates higher than 6 mL min‒1, the
recovery of the metal ions were not quantitative, except for
‒1
Cr(III) and Co(II) ions, and so a flow rate of 6 mL min was
chosen for the subsequent experiments for both sample and
elution solutions.
Influences of the Amounts of the Chelating Resin. The effects
of the amounts of the chelating resin on adsorption of the metals
were investigated at the flow rates of 6 mL min‒1 of sample and
elution solutions. The results are given in Fig. 4. The recovery
values increased with the increasing amounts of the chelating
resin and reached to quantitative value (recovery about 100%)
for the amount of 0.5 g of the resin. The recovery of the metal
ions decreased with increasing amounts of the resin beyond
120
Cu
Cd
Pb
Ni
Co
Cr
Fe
Mn
Zn
100
Recovery (%)
446
80
60
40
20
0
0
2
4
6
8
10
12
pH
Figure 2. Effect of pH on the recovery of the analytes (sample volume:
‒1
25 mL, chelating resin: 0.50 g, eluent: 10 mL of 2 mol L HCl, n = 3).
Table 1. Effect of volume and concentration of HCl and HNO3 solutions on the recovery of the analytes (sample volume: 25 mL, pH 2.5, n = 3)
Concentration and type of
Volume (mL)
eluent
‒1
3 mol L HNO3
3 mol L‒1 HNO3
‒1
2 mol L HNO3
2 mol L‒1 HCl
1 mol L‒1 HCl
‒1
2 mol L HCl
a
Average ± standard deviation.
25
10
10
10
10
5
Recovery (%)
a
Cd(II)
Co(II)
Cr(III)
Cu(II)
Fe(III)
Mn(II)
Ni(II)
Pb(II)
Zn(II)
95 ± 1
95 ± 1
91 ± 2
98 ± 1
96 ± 1
76 ± 2
92 ± 2
90 ± 1
84 ± 2
100 ± 2
93 ± 2
79 ± 1
100 ± 1
100 ± 2
100 ± 2
100 ± 1
100 ± 3
91 ± 1
97 ± 1
97 ± 1
80 ± 1
95 ± 1
92 ± 1
74 ± 1
100 ± 1
100 ± 2
88 ± 2
100 ± 1
100 ± 3
100 ± 1
100 ± 1
100 ± 2
91 ± 1
100 ± 1
91 ± 2
77 ± 1
96 ± 1
95 ± 1
88 ± 2
99 ± 1
89 ± 1
77 ± 3
100 ± 1
100 ± 1
90 ± 1
100 ± 1
98 ± 1
76 ± 2
91 ± 2
90 ± 3
100 ± 2
100 ± 2
95 ± 3
57 ± 1
Bull. Korean Chem. Soc. 2011, Vol. 32, No. 2
120
120
100
100
80
Cu
Cd
Pb
Ni
Co
Cr
Fe
Mn
Zn
60
40
20
0
Recovery (%)
Recovery (%)
Novel Solid Phase Extraction Procedure
60
40
0
0
2
4
6
8
10
12
120
Cu
Cd
Pb
Ni
Co
Cr
Fe
Mn
Zn
100
80
60
40
20
0
0.2
0.4
0.6
0
200
400
600
800
1000
1200
Sample volume (mL)
Figure 3. Effect of flow rate of sample solution on the recovery of the
analytes (sample volume: 25 mL, chelating resin: 0.5 g, pH 2.5, eluent:
‒1
10 mL of 2 mol L HCl, n = 3).
Recovery (%)
Cu
Cd
Pb
Ni
Co
Cr
Fe
Mn
Zn
20
Sample flow rate (mL/min)
0
80
447
0.8
Amounts of resin (g)
Figure 4. Influences of the amounts of the chelating resin (sample volume: 25 mL, sample flow rate: 6 mL min‒1, pH 2.5, eluent: 10 mL of 2
‒1
mol L HCl, n = 3).
0.6 g due to the insufficient eluent volume. If the eluent volume
was higher than 10 mL, the recoveries were quantitative. In all
subsequent studies, the glass column was filled with 0.5 g of
the chelating resin.
Effect of Sample Volume. In order to deal with real samples,
especially water samples, containing very low concentrations
of the metal ions, the maximum applicable sample volume
must be determined. For this purpose, 25 - 1000 mL volumes of
the model solutions containing 2 - 20 µg of the trace elements
were passed through the column under the optimum conditions.
The recovery values as a function of sample volume are shown
in Fig. 5. The recoveries were quantitative and constant up to
1000 mL of the sample solution, except for Cd(II) and Ni(II),
because they have been recovered quantitatively only up to
500 mL of the sample volume. The preconcentration factor was
calculated as the ratio of the highest sample volume (1000 mL)
to the eluent volume (10 mL) and found to be 100 for all the
metal ions, except for Cd(II) and Ni(II) ions, which is 50 for
them.
Effect of Matrix Ions. The effects of possible matrix ions
Figure 5. Effect of the sample volume on the recovery of the metal ions
‒1
(resin amount: 0.5 g, eluent: 10 mL of 2 mol L HCl, pH 2.5, sample
‒1
flow rate: 6 mL min , n = 3).
(Na+, K+, Ca2+, Mg2+, Cl‒, NO3‒, SO42‒, PO43‒) present in environmental samples on the recoveries of the studied elements
were also examined by adding the known concentration of each
matrix ion to the model solution containing the studied trace
elements. The results are summarized in Table 2. The tolerated
amounts of each ion were the concentration values tested that
caused less than 5% alteration in the absorbance. Although some
diverse ions have caused negative interfering effects on the
recoveries of certain metal ions studied; i.e., Na+, K+, SO42‒ and
PO43‒ on the recoveries of Cd (81 - 86%), Mg2+ on the Cr and Ni
+
+
2+
‒
(90 - 92%), Na , K and Ca on the Co (90 - 92%), Cl on the Fe
2+
2+
2‒
(90%), and Ca , Mg and SO4 on the Mn (80 - 89%). As can
be seen from Table 2, the ions normally present in natural samples did not interfere under the experimental conditions used (recoveries ≥ 95%). These results indicate that the proposed separation/preconcentration method for the studied trace elements
could be applied to various environmental samples.
Adsorption Capacity of the Resin. The adsorption capacity
of the MTMAAm/AMPS/DVB resin for the analyte ions was
studied using batch technique. A known amount of the chelating
resin (0.1 g) was equilibrated with a known and excess amount
of the metal ion solution (10 mg in 50 mL) by shaking for 30 min
at pH 2.5. The mixture was then filtered off and the filtrate was
diluted 20-100 fold. Concentrations of the metal ions in the filtrate were determined by FAAS. Adsorption capaties (mg g‒1,
n = 3) were found to be: 29.5 ± 0.7 for Cd(II), 28.4 ± 0.5 for
Co(II), 7.8 ± 0.2 for Cr(III), 4.3 ± 0.1 for Cu(II), 41.2 ± 1.2 for
Fe(III), 18.6 ± 1.1 for Mn(II), 20.7 ± 0.8 for Ni(II), 44.3 ± 0.8 for
Pb(II), and 34.3 ± 1.6 for Zn(II).
Analytical Performance. In order to determine the detection
limit (DL) of the proposed method, the pH of the blank solutions
(25 mL, n = 20) was adjusted to pH 2.5 using CH3COOH/CH3COONa buffer solution and then the preconcentration method
was applied. The detection limits, calculated as the amount of
analyte required to yield a net peak equal to three times the
standard deviation of the blank solution, were found to be 0.18
for Cd(II), 0.11 for Co(II), 0.07 for Cr(III), 0.12 for Cu(II), 0.18
for Fe(III), 0.67 for Mn(II), 0.13 for Ni(II), 0.06 for Pb(II), and
0.09 µg L‒1 for Zn(II). In the calculation of the DL of the method,
448
Şerife SAÇMACI et al.
Bull. Korean Chem. Soc. 2011, Vol. 32, No. 2
Table 2. Effect of volume and concentration of HCl and HNO3 solutions on the recovery of the analytes (sample volume: 25 mL, pH 2.5, n = 3)
Ion
+
Na
K+
Ca2+
Mg2+
SO42‒
Cl‒
NO3‒
PO43‒
Recovery (%)a
Concentration
‒1
(mg L )
Cd(II)
Co(II)
Cr(III)
Cu(II)
Fe(III)
Mn(II)
Ni(II)
Pb(II)
Zn(II)
2500
4000
800
400
1000
4500
1000
5000
84 ± 1
81 ± 1
94 ± 1
95 ± 1
87 ± 1
95 ± 1
96 ± 1
86 ± 1
90 ± 1
90 ± 1
92 ± 2
94 ± 1
96 ± 1
100 ± 1
95 ± 1
100 ± 1
95 ± 1
100 ± 2
100 ± 2
90 ± 1
100 ± 2
95 ± 2
96 ± 1
99 ± 1
96 ± 1
98 ± 1
96 ± 1
100 ± 2
96 ± 1
100 ± 1
100 ± 1
96 ± 1
100 ± 1
100 ± 1
94 ± 1
95 ± 1
96 ± 1
90 ± 2
97 ± 1
98 ± 1
96 ± 2
94 ± 2
83 ± 2
80 ± 2
89 ± 1
95 ± 3
98 ± 1
96 ± 1
100 ± 1
94 ± 2
100 ± 1
92 ± 1
100 ± 1
100 ± 1
96 ± 1
95 ± 1
95 ± 1
96 ± 1
95 ± 1
95 ± 1
90 ± 1
99 ± 1
95 ± 1
100 ± 1
98 ± 2
94 ± 2
94 ± 1
98 ± 1
95 ± 1
95 ± 2
98 ± 2
99 ± 3
a
Average ± standard deviation.
Table 3. The results of accuracy test for samples (sample volume: 250 mL, final volume: 10 mL, n = 3)
Added (µg)
Tap water
Found (µg)
Recovery (%)
Added (µg)
Dill samples
Found (µg)
Recovery (%)
Cd
15
30
14.3 ± 0.2a
29.2 ± 0.6
95
99
2.5
5.0
0.6 ± 0.1
3.1 ± 0.1
5.6 ± 0.2
100
100
Co
15
30
15.2 ± 0.5
29.8 ± 0.7
101
97
5
10
4.9 ± 0.3
9.8 ± 0.7
98
98
Cr
15
30
3.6 ± 0.5
18.4 ± 0.5
33.4 ± 0.9
99
99
5
10
4.9 ± 0.6
9.9 ± 0.5
98
100
Cu
15
30
33.3 ± 0.3
48.1 ± 0.4
62.4 ± 1.4
99
97
15
30
6.1 ± 0.3
20.9 ± 0.4
35.8 ± 0.6
99
99
Fe
15
30
29.3 ± 1.4
44.1 ± 1.1
59.4 ± 1.4
99
100
50
100
102 ± 2
150 ± 2
200 ± 3
96
98
Mn
15
30
14.6 ± 0.5
28.9 ± 1.3
97
95
5
10
6.6 ± 0.7
11.4 ± 0.4
16.3 ± 0.9
96
97
15
30
14.8 ± 0.4
29.7 ± 0.6
99
99
2.5
5.0
2.7 ± 0.1
5.1 ± 0.2
7.6 ± 0.5
96
98
Pb
15
30
14.9 ± 0.1
29.8 ± 1.1
99
99
5
10
5.1 ± 0.2
9.8 ± 0.4
102
98
Zn
25
50
57.0 ± 1.6
82.6 ± 1.8
108 ± 2
102
102
2.5
5.0
3.1 ± 0.1
5.5 ± 0.4
7.9 ± 0.9
96
96
Ni
a
Average ± standard deviation.
the 100 fold preconcentration factor was taken into consideration. For the metal ions studied, regression coefficients (R2) of
the calibration curves were between 0.9990 and 0.9996. The
precision of the method under the optimum conditions was determined by performing successive 10 retention and elution cycles followed by FAAS. The relative standard deviations for the
metals studied were lower than 2%.
Accuracy and Application of the Method. In order to investi-
gate the accuracy of the proposed procedure, the first work
made was the recovery study. For this reason, the known amounts of the analyte ions were added to tap water and aqueous
digests of dill samples and then the proposed method has been
applied. The results are shown in Table 3. A good agreement was
obtained between the added and the measured amounts of the
metals. The recovery values calculated were always higher
than 95%, thus confirming the accuracy of the proposed proce-
Novel Solid Phase Extraction Procedure
Bull. Korean Chem. Soc. 2011, Vol. 32, No. 2
449
Table 4. The levels of trace elements in the certified reference materials after the application of the presented procedure
Cd(II)
SPS-WW2 Batch 108
Certified value (µg L‒1)
‒1
Found (µg L )
Recovery (%)
INCT-TL-1 tea leaves
‒1
Certified value (µg L )
Found (µg L‒1)
Recovery (%)
Co(II)
100.0 ± 0.5 300 ± 2
102 ± 2a 304 ± 4
102
101
30.2 ± 4.0
29.8 ± 1.3
99
Cr(III)
Cu(II)
Fe(III)
Mn(II)
Ni(II)
1000 ± 5 2000 ± 10 5000 ± 25 2000 ± 10 5000 ± 25
997 ± 11 1890 ± 12 5006 ± 19 1891 ± 14 4886 ± 13
100
95
100
95
98
387 ± 42 1.91 ± 0.22 20.4 ± 1.5
385 ± 3 1.88 ± 0.20 19.8 ± 1.1
100
98
97
432
435 ± 4
101
Pb(II)
Zn(II)
500 ± 3
497 ± 8
99
3000 ± 15
3015 ± 11
101
0.16 ± 0.01 6.12 ± 0.52 1.78 ± 0.24 34.7 ± 2.7
0.15 ± 0.01 6.00 ± 0.40 1.73 ± 0.20 34.1 ± 1.1
96
98
97
98
a
At 95% confidence level (mean ± t·s /√n).
Table 5. The application of the presented method to the real samples for their heavy metal contents (n = 3)
Metal ions
‒1
Water samples (µg L )
Cd(II)
Co(II)
1.6 ± 0.4
2.1 ± 0.8
-
3.4 ± 0.4
-
5.8 ± 0.1
0.58 ± 0.1
-
0.5 ± 0.1
0.3 ± 0.1
-
Tap water
Lake water
Waste water
Rain water
‒1
Solid samples (µg g )
Soil
Black tea
Dill
Cinnamon
Cr(III)
Cu(II)
Fe(III)
Mn(II)
Ni(II)
Pb(II)
Zn(II)
3.6 ± 0.5a 33.3 ± 0.3 29.3 ± 1.4
-b
0.13 ± 0.06 57.0 ± 1.6
5.6 ± 0.9 4.8 ± 0.4 30.1 ± 1.5
6.4 ± 0.9
9.8 ± 0.9
19.0 ± 1.8 32.8 ± 1.2 88.4 ± 1.9 27.3 ± 1.4 15.1 ± 1.3 6.4 ± 0.8 26.3 ± 1.1
27.2 ± 0.6 195 ± 2
13.8 ± 1.1 10.2 ± 1.1
11.4 ± 0.9
2.0 ± 0.4 3.5 ± 0.5 595 ± 2
12.7 ± 0.5 9.0 ± 1.1
6.1 ± 0.3 102 ± 2
6.7 ± 0.6
7.5 ± 0.9
25.4 ± 1.0
6.6 ± 0.7
14.4 ± 0.9
1.9 ± 0.3
4.6 ± 0.2
2.7 ± 0.1
-
6.3 ± 0.8 0.50 ± 0.03
0.9 ± 0.1 1.7 ± 0.1
3.1 ± 0.1
3.5 ± 0.8
a
At 95% confidence level (mean ± t·s /√n). bBelow detection limit.
Table 6. Comparative data from some recent studies on preconcentration-separation of heavy metal ions
Method
Analytes
System
Eluent
SPE
SPE
SPE
SPE
Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn
Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, V, Zn
Cd, Co, Cu, Mn, Ni, Pb
Cd, Co, Cu, Pb, Zn
FAAS
ICP-AES
FAAS
FAAS
2.0 mol L HCl
‒1
2.0 mol L HNO3
‒1
1.0 mol L HNO3
‒1
0.1 mol L HCl
‒1
2.0 mol L HCl-1.5
‒1
mol L HNO3
‒1
4.0 mol L HNO3
a
SPE Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn
FAAS
SPE Cu, Fe, Zn
FAAS
‒1
DL (µg L‒1)
RSDa (%)
PFb
pH
Reference
0.06 - 0.67
0.003 - 0.28
0.08 - 0.26
1.95 - 9.50
≤ 1.5
1.9 - 5.1
2.98
100
50
100
17
2.5
5.5
8.0
6.7
This work
[3]
[8]
[19]
0.3 - 13.9
0.95 - 1.0
1.01 - 2.58 100 - 300 3.5 - 7.0
<4
90
6.0
[20]
[21]
b
Relative standard deviation. Preconcentration factor.
dure and its independence from the matrix effects. These results
confirm the validity of the proposed separation/preconcentration
method.
To validate the accuracy of the solid phase extraction procedure, the second work made was to analyze the certified reference materials, SPS-WW2 Batch 108 Wastewater level 2 and
INCT-TL-1 Tea leaves. The proposed method was applied to
these two certified reference materials for the determination of
the metal ions. The results are given in Table 4. The observed
values of the analytes in the certified reference materials were
in good agreement with their certified values.
The method was also extended for the separation and preconcentration of the trace elements in tap water, waste water, lake
water and rain water samples. The final measurement volume
was 5 mL for all the samples. The results are shown in Table 5.
The observed values of the analytes were in good agreement
with those given in the literature for the real samples.
Comparison with Other Analytical Techniques. The comparison of the obtained results with those given in the literature is
shown in Table 6. The main novelty of this work is the firstly
use of the MTMAAm/AMPS/DVB resin for the separation/preconcentration purpose by applying the solid phase extraction.
The other advantages obtained with the proposed method can
be explained in the following by sequence of importance: (a)
low detection limits, (b) lower RSD% values than those of the
other methods, (c) the acidic working medium (pH 2.5) and
450
Şerife SAÇMACI et al.
Bull. Korean Chem. Soc. 2011, Vol. 32, No. 2
good tolerance limits towards many interfering ions, (d) the
accuracy of the method are satisfactory, (e) the simultaneous
nature of the determination, (f) the simplicity, accuracy, and
easily applicability of the method, (g) the easy elution of the
analytes with only 10 mL of 2 mol L‒1 HCl, (h) a high preconcentration factor, 100, and (i) the resin has high recycle numbers.
2.
3.
4.
Conclusion
5.
6.
This newly designed chelating resin can be successfully
employed for the separation, preconctration and determination
of Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Mn(II), Ni(II), Pb(II),
and Zn(II) ions in soil, food and various water samples by
FAAS. The MTMAAm/AMPS/DVB material is an effective
chelating resin and offers a useful multi-element preconcentration technique for applying to various environmental samples,
such as lake water, waste water and solid samples with acceptable accuracy and precision. The high stability of the resin permitted hundreds of adsorption-elution cycles along the studies
without any significant decrease in the recoveries. The validation of the developed method was successfully performed by
analyzing the certified reference materials. Also the trace element contents were determined in natural waters, soil and food
samples.
7.
Acknowledgments. The authors are grateful for the financial
support of the Unit of the Scientific Research Projects of Erciyes
University with Project Contract No EÜBAP-FBA-07-34.
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