An enrichment/separation system for atomic absorption spectrometric determinations of Cu(II), Fe(III), Ni(II) and Co(II) has been established. The procedure is based on the adsorption of the analytes as calmagite chelates on Chromosorb-102. The effects of some parameters including pH, amount of ligand, salt matrix, flow rates of sample and eluent solutions were investigated. Under optimized conditions, the relative standard deviation of the combined method of sample treatment, preconcentration and determination with FAAS (N=5) is generally lower than 5%. The limit of detection (3σ) was between 6.0-112. 9 μg/L. The results were used for preconcentration of analytes from some sodium and ammonium salt

Elçi, Latif

Saracoglu, S.

Soylak, M.

English

Pamukkale Üniversitesi Açık Erişim Arşivi

Sorbent Extraction of Some Metal Ions on a Gas Chromatographic Stationary Phase  Bull. Korean Chem. Soc. 2003, V l. 24, No. 5     555
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reSorbent Extraction of Some Metal Ions on a Gas Chromatographic Stationary
Phase Prior to Their Flame Atomic Absorption Determinations
M. Soylak,* S. Saracoglu,† and L. Elci‡
Erciyes University, Faculty of Art and Science, Department of Chemistry, 38039 Kayseri-TURKEY
†Erciyes University, Faculty of Education, 38039 Kayseri-TURKEY
‡Pamukkale University, Faculty of Art-Science, Department of Chemistry, 20020 Denizli-TURKEY
Received September 24, 2002
An enrichment/separation system for atomic absorption spectrometric determinations of Cu(II), Fe(III), Ni(II)
and Co(II) has been established. The procedure is based on the adsorption of the analytes as calmagite chelate
on Chromosorb-102. The effects of some parameters including pH, amount of ligand, salt matrix, flow rates of
sample and eluent solutions were investigated. Under optimized conditions, the relative standard deviation of
the combined method of sample treatment, preconcentration and determination with FAAS (N=5) is generally
lower than 5%. The limit of detection (3σ) was between 6.0-112.9 µg/L. The results were used for
preconcentration of analytes from some sodium and ammonium salt. 
Key Words : Trace metals, Impurities, Chromosorb-102, Preconcentration, Calmagite
Introduction
The determination of trace impurities in salt samples is
important, because of the effects of the impurities on some
electrical, mechanical and chemical properties of the salt
sample and the necessity of the high purity salt samples in
certain areas such as semiconductors, nuclear industry etc.1,2
Atomic absorption spectrometry (AAS) is the one of the
important technique for the determination traces metals. To
determine trace metals in various samples by AAS, a
separation and preconcentration technique is frequently
required, because of the low concentration of metals ions
and the presence of interference.3 
Many methods include membrane filtration, coprecipitation,
solvent extraction, cloud point extraction etc. have been
developed for preconcentration of trace metals.3-6 The
adsorption of trace elements onto stationary phases has
proved to be a valuable preconcentration technique because
it provides very high concentration factors, compared the
other techniques, and often permits an interference free
determination.3-7 The key to a successful separation of an
analyte is the choice of the chemical interaction between the
analyte and column material. Adsorption of complexed
metals on sorbents, such as activated carbon, Amberlite
XAD resins, naphthalene, C-60, silicagel etc have been
widely applied to the preconcentration of metals from
various samples.8-12 Chromosorb resins (Chromosorb -101,
-102, -105, -108 etc.) are synthetic polymeric materials13,14
and have been used for gas chromatography as stationary
phases, because they have good physical and chemical
properties such as porosity, high surface area, durability and
purity and are resistant in concentrated mineral acid,
concentrated bases and organic solvents for a long time.
They have been used for the preconcentration of tra
heavy metal ions in the various samples.13-21
Calmagite is widely used chelating agent that has a lar
formation constant with metal ions and is also used 
preconcentration of metal ions. Ferreira et al.22 have been
used calmagite as complexing agent for copper with the 
line sorption of the complexes on XAD-2. The determi
ation of Cu by FAAS was performed after preconcentrati
f calmagite complex on XAD-2.23 Calmagite was also used
for the enrichment of Mo(VI) on activated carbon.24 The
preconcentration of calmagite metal complexes on cellul
nitrate membrane filter have been performed by Soylaket
al.25 The same reagent was used for the preconcentratio
some metal ions from seawater samples on XAD-1180.26
In the present work, the analytical conditions for th
quantitative recoveries of some metal ions as chelates w
calmagite on Chromosorb-102 were investigated. 
Experimental Section
Reagents and Solutions. Analytical reagent-grade chemical
were employed for the preparation of all solutions. Fres
prepared doubled distilled water, from a quartz still, w
used in all experiments. Stock metal ion solutions, 1000 m
(E. Merck) were diluted daily to obtaining reference an
working solutions. Calmagite (1.0× 10−2 M) was dissolved
in water and prepared daily. Chromosorb-102 (80-100 me
(Sigma) was washed successively with methanol, water, 1
HNO3 in acetone, water, 1 M NaOH and water.
Sodium phosphate buffer (0.1 M) was prepared by add
an appropriate amount of phosphoric acid (Merck) 
sodium dihydrogen phosphate solution to result in a solut
of pH 2. Ammonium acetate buffers (0.1 M) were prepar
by adding an appropriate amount of acetic acid (Merck)
ammonium acetate solutions to result in solutions of pH 4
and ammonium chloride buffer solutions (0.1 M) we
*Corresponding author: phone and fax: +90 352 4374933, e-mail:
soylak@erciyes.edu.tr
556    Bull. Korean Chem. Soc. 2003, Vol. 24, No. 5 M. Soylak et al.
 as
o
lso
ies,
he
ite.
ut
er
lso
ere
t.
ely
re
 M
r
.
ten-
ns
iteprepared by adding an appropriate amount of ammonia
(Merck) to ammonium chloride solutions to result in solutions
of pH 8-10. 
Instrument . The instrumental detection system used was
a Perkin-Elmer Model 3110 AAS. The operating parameters
were those recommended by the manufacturer. All measure-
ments were carried out without background correction with
air/acetylene flame. A pH meter, Nel pH-900 Model was
employed for measuring pH values in the aqueous phase.
The samples were introduced to the nebulizer of AAS by
using micro injection method.27 100 µL of sample was
injected to a mini home-made Teflon funnel with a
Eppendorf Pipette. The Teflon funnel was connected to the
nebulizer with capillar tubing. The peak height signals were
recorded. 
Column Preparation. A glass column with an inner
diameter of 10 mm and a length of 100 mm, equipped with
porous frits, was filled up to a height of about 25 mm with a
suspension of 500 mg of resin in water. Prior to use, the resin
was preconditioned with buffer solution. After each
experiment, the column was rinsed with water and stored.
Test Procedure for Preconcentration. A required volume
of a 1.0× 10−2 M solution of calmagite was added to 50 mL
of solution containing 10 µg of the each metal ion and
brought to desired pH between 2 and 10. The column was
preconditioned with 10-15 mL of the water brought to the
same pH of working pH. The sample solution was permitted
to flow through the column at a flow rate of 5 mL/min. After
passing of this solution, the column was rinsed twice with 10
mL of water. The retained metal-chelates were eluted with
10 mL portion of 1 M HNO3 in acetone at a flow rate of 5
mL/min. The eluate was evaporated to near dryness. The
residue was diluted to 2-5 mL with 1 M HNO3. The metal
concentrations in the final solution were determined by
flame AAS. 
Application to Real Samples. Five gram of salt sample
was dissolved in 50 mL of distilled water. 2 mL of calmagite
was added to this solution and the pH of solution was
adjusted to 8 with ammonium chloride buffer solution. The
sample was passed through the column at a 5 mL/min, then,
the adsorbed metal chelates to the column were eluted with
10 mL 1 M HNO3 in acetone. The eluate was evaporated to
near dryness. It was diluted to 2 mL with 1 M HNO3. To
determine the analytes in the concentrated solutions, an
aliquot 100 µL of the solution was introduced to the
nebulizer of FAAS by microinjection method. 
Results and Discussion
Effect of the pH on the Retentions. pH is a very
important factor for efficient recoveries of analyte ions. The
influence of pH on the solid phase extraction was studied in
the range of 2-10. The pHs of the each solution were
adjusted by the addition of relevant buffer solution given in
the Experimental and were controlled by pH meter. The
results are presented in Figure 1. The recovery depended on
the pH that was nearly constant in the pH range of 6-10, 4-10
for Ni and Co, Cu and Fe respectively. pH 8 was selected
working pH. The volume of the buffer solution had n
efficient effects on the recoveries. 
Influences of the Amounts of Calmagite. The influences
of the amounts of calmagite on the recoveries were a
examined. The results are given in Figure 2. The recover
≥ 95%, are quantitative for each of Fe, Ni and Co in t
examinated range, for Cu in the range 0.5-2 mL calmag
The recoveries obtained from the sample solution witho
calmagite were not quantitative except for Fe. All furth
studies 2 mL of calmagite was used as ligand. 
The Effect of Eluent Type. The effects of eluents on the
recoveries of analytes from Chromosorb-102 were a
investigated. Quantitative recoveries for all analytes w
obtained with 10 mL of 1 M HNO3 in acetone. The recovery
of nickel was quantitative with all of investigated eluen
While with 1 M HNO3, Cu, Fe and Ni were quantitatively
recovered, with acetone, only Ni and Co were quantitativ
recovered. Also, selective eluation of metal ions we
possible with some eluents. For example with 5 mL of 0.5
HNO3, only nickel was recovered quantitatively. All furthe
studies 10 mL of 1 M HNO3 in acetone was used as eluent
Sample and Eluent Flow Rates. Sample and eluent flow
rates are important parameters to obtain quantitative re
Figure 1. pH dependence of the recoveries of the metal io
(eluent: 10 mL of 1 M HNO3 in acetone, metal amounts: 10 µg,
N = 3). 
Figure 2. Changes on the recoveries of metal ions with calmag
amounts (N = 3, eluent: 10 mL of 1 M HNO3 in acetone).
Sorbent Extraction of Some Metal Ions on a Gas Chromatographic Stationary Phase  Bull. Korean Chem. Soc. 2003, V l. 24, No. 5     557
,
 on
o
 by
. 
,
een
ng
nd
sed
 of
the
the
ple
in-
lity
s;
.;tion and elution of analyte, respectively. The retentions for
the analytes were virtually quantitative for sample flow rates
up to 10 mL/min. Variation of the elution flow rate in the
range of 1.0-6.0 mL/min has no effect on the elution effici-
ency. In consequence, 5 mL/min was selected as flow rate
for loading and elution from the trap. 
Effect of Salt Matrix . To investigate the effect of high
concentrations of ammonium chloride, ammonium sulfate
and sodium chloride salts on the recovery of analytes, the
procedure were carried out with samples containing salts in
the range of 1-10 g (Table 1). Quantitative recovery values
for Cu, Fe, Ni and Co up to 10 g of sodium chloride, for Fe,
Ni and Co up to 10 g of ammonium chloride, for Cu, Fe, Ni
and Co up to 10 g of ammonium sulfate were obtained. It
was concluded that Cu(II), Fe(II), Ni(II) and Co(II) occurr-
ing as impurities in ammonium and sodium salts can be
determined with presented procedure. 
Analytical Performance of the Method. The accuracy of
the results was verified by analyzing the concentration after
addition of known amounts of analytes into a 50 mL solution
containing 5 g NaCl and NH4Cl. Good agreement was
obtained between the recovery of analyte for spiked and
control samples using the experimental procedure for Cu,
Fe, Ni and Co in NaCl and Fe, Ni and Co in NH4Cl. Because
of the recovery of Cu from NH4Cl were not quantitative, the
determination of Cu in NH4Cl was not performed. 
The reproducibility of the method was evaluated by
passing 50 mL of solution containing 10 µg of each analyte
ion through Chromosorb-102 and repeating this procedure
five times. The relative standard deviations were ± 2.7%,
± 2.1 %, ± 1.6 %, ± 2.1% for copper, iron, nickel and cobalt
respectively. The detection limits of the analytes based
three times the standard deviations of the blank (k = 3,
N = 20) on a sample volume 50 mL for Cu, Fe, Ni and C
were 17.0 µg/L, 112.9 µg/L, 11.0 µg/L, 6.0 µg/L, respective-
ly. The detection limits of the analytes can be decreased
one order of magnitude by increasing the sample volume
Application to Salt Samples. The method has been
employed for the determination copper(II), iron (III)
nickel(II) and cobalt(II) ions in NaCl, NH4Cl and (NH4)2SO4
salts. The results, which are shown in Table 2, have b
calculated by assuming 100% recovery of the worki
elements. The relative standard deviations (= 5) with
related to the determinations in the salts for Cu, Fe, Ni a
Co were in the range of 4.0-9.7%. 
 
Conclusion
Because of 500 mg of Cromosorb-102 resin can be u
repeatedly for 300-400 samples at least with 5 mL/min
sample and eluent flow rates and the time required for 
preconcentration and determination was about 25 min, 
proposed preconcentration system provides a fast and sim
method for enrichment on Chromosorb-102. The determ
ation procedure was characterized by good reproducibi
and accuracy. 
References
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Table 1. Influences of the certain sodium and ammonium salts as
matrix on the recoveries of trace impurities (N = 3, V = 50 mL)
Salt
Concentration, 
g/50 mL
Recovery, %
Cu Fe Ni  Co
NaCl 1 97 100 100 95
5 97 100 100 100
10 100 100 100 95
NH4Cl 1 41 96 100 100
5 71 95 100 100
10 44 95 100 100
(NH4)2SO4 1 95 100 100 100
5 96 100 100 100
10 96 100 100 95
Table 2. The concentration of copper(II), iron(III), nickel(II) and cobalt(II) in some sodium and ammonium salts
Sample
Concentration, µg/ga
Cu Fe Ni Co
Refined Table Salt 0.11 ± 0.01 2.90 ± 0.19 0.39 ± 0.02 B.L.D
Unrefined Table Salt 0.09 ± 0.01 2.73 ± 0.19 0.45 ± 0.02 0.32 ± 0.02
NaCl (Analytical Reagent Grade) 0.15 ± 0.02 1.56 ± 0.16 0.31 ± 0.02 0.28 ± 0.02
NaCl (Technical Grade) 0.11 ± 0.01 1.53 ± 0.14 0.34 ± 0.03 0.19 ± 0.02
NH4Cl (Analytical Reagent Grade) N.D. 3.24 ± 0.28 0.34 ± 0.02 0.25 ± 0.02
(NH4)2SO4 (Analytical Reagent Grade) 0.07 ± 0.01 0.94 ± 0.10 0.16 ± 0.01 0.10 ± 0.01
aP = 0.95, ± t.s/√N, N = 5, BLD: Below the Detection Limit, ND: Not Determined.
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Sorbent extraction of some metal ions on a gas chromatographic stationary phase prior to their flame atomic absorption determinations

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Sorbent extraction of some metal ions on a gas chromatographic stationary phase prior to their flame atomic absorption determinations

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