American Journal of Anal yt ical Chemistry, 2011, 2, 757-767
doi:10.4236/ajac.2011.27087 Published Online November 2011 (http://www.SciRP.org/journal/ajac)
Determination of Trace Amounts of Lead by Modified
Graphite Furnace Atomic Absorption Spectrometry
after Liquid Phase Microextraction with
Pyrimidine-2-thiol
Saeid Nazari1,2
1Department of Chemistry, Faculty of Science, Sabzevar Tarbiat Moallem University, Sabzevar, Iran
2Department of Chemistry, Quchan Branch, Islamic Azad University, Quchan, Iran
Received December 18, 2010; revised February 3, 2011; accepted February 11, 2011
Abstract
The liquid phase microextraction (LPME) was combined with the modified Graphite furnace atomic absorp-
tion spectrometry (GF-AAS) for determination of lead in the water and solid samples. In a preconcentration
step, lead was extracted from a 2 ml of its aqueous sample in the pH = 5 as lead-Pyrimidine-2-thiol cationic
complex into a 4 µl drop of 1,2 dichloroethane and ammonium tetraphenylborate as counter ion immersed in
the solution. In the drop, the lead-Pyrimidine-2-thiol ammonium tetraphenylborate ion associated complex
was formed. After extraction, the microdrop was retracted and directly transferred into a graphite tube modi-
fied by [W.Pd.Mg] (c). Some effective parameters on extraction and complex formation, such as type and
volume of organic solvent, pH, concentration of chelating agent and counter ion, extraction time, stirring rate
and effect of salt were optimized. Under the optimum conditions, the enrichment factor and recovery were
525% and 94%, respectively. The calibration graph was linear in the range of 0.01 - 12 µg·L–1 with correla-
tion coefficient of 0.9975 under the optimum conditions of the recommended procedure. The detection limit
based on the 3Sb criterion was 0.0072 µg·L–1 and relative standard deviation (RSD) for ten replicate meas-
urement of 0.1 µg·L–1 and 0.4 µg·L–1 lead was 4.5% and 3.8% respectively. The characteristic concentration
was 0.0065 µg·L–1 equivalent to a characteristic mass of 26 fg. The results for determination of lead in refer-
ence materials, spiked tap water and seawater demonstrated the accuracy, recovery and applicability of the
presented method.
Keywords: Lead, Liquid Phase Microextraction, Preconcentration, Graphite Furnace Atomic Absorption
Spectrometry
1. Introduction
Lead is one of the most ubiquitous elements in the envi-
ronment and is recognized as a major health risk to hu-
mans and animals [1,2]. Lead is a serious cumulative
body poison [3] which enters our body system through
air, water, and food. Inorganic lead binds itself with the
SH group in enzymes or proteins and acts as an enzyme
inhibitor [4]. Acute lead poisoning in humans causes
severe damage in the kidneys, liver, brain, reproductive
system and central nervous system, and even causes
death. Mild lead poisoning causes anemia, headache and
sore muscles and the victim may feel fatigued and irrita-
ble. Chronic exposure to lead causes nephritis, scaring
and the shrinking of kidney tissues [5]. It is emitted into
the biosphere in considerable amounts, owing to its in-
creased industrial use and its application as a fuel addi-
tive [6,7]. In recent years, concern has increased over the
concentration of lead in drinking and natural waters [8].
A variety of techniques such as inductively coupled
plasma mass spectrometry (ICP-MS) [9], ICP-atomic
spectrometry [10,11], electrothermal atomic absorption
spectrometry [12] and flame atomic absorption spec-
trometry (FAAS) [13-16] has been widely used for the
determination of trace metal in different samples.
Monitoring trace element concentrations in biological

S. NAZARI
758
materials, particularly biological fluids, might be consid-
ered a difficult analytical task, mostly due to the com-
plexity of the matrix and the low concentration of these
elements, which requires sensitive instrumental tech-
niques and often a preconcentration step. The most
widely used techniques for separation and preconcentra-
tion of trace lead include liquid–liquid extraction [17],
cloud point extraction [18,19], solid phase extraction
[20-24] and electrochemical deposition [25], etc. The
solvent microextrction technique effectively overcomes
these difficulties by reducing the amount of organic sol-
vent and by allowing sample extraction and preconcen-
tration to be done in a single step. The technique is faster
and simpler than conventional methods. It is also inex-
pensive, sensitive and effective for the removal of inter-
fering matrices. Solvent microextraction is a form of
solvent extraction with phase ratio values higher than
100 [26-30]. This technique uses simple equipment
which is found in most analytical laboratories and also
has been used for sample preparation of organic compo-
nents and has coupled with chromatography methods.
We developed this technique in our laboratory and re-
ported for the first time on the coupling of liquid phase
microextraction (LPME) with spectrometry to determine
inorganic compounds. Using this technique, arsenic in a
variety of samples was determined [33].
In this paper, we describe a new and extremely high
sensitive method for extraction and determination of lead
in aqueous samples by liquid phase microextraction com-
bined with a graphite furnace atomic absorption spec-
trometry (LPME-GF-AAS). The results indicate that the
LPME is an efficient extraction technique for analyzing
lead in real samples, with very high pre-concentration fac-
tor, greatly increased sensitivity and low detection limit.
The method is very simple and quick so that the overall
time of extraction and determination for each sample is 8
minutes.
2. Experimental
2.1. Instrumentation
A Shimadzu model AA-6300G atomic absorption spec-
trometer (Kyoto, Japan) with GFA-EX7i graphite furnace
atomizer and D2 lamp for background correction was
used. A lead hollow cathode lamp (Hamamatsu photon-
ics, Kyoto, Japan) was used as the radiation source ad-
justed at the operating current at the wavelength of 283.3
nm with 0.4 nm spectral bandpass. All measurements
were performed using peak height and gas stop mode.
The measurement conditions are given in Table 1. All
pH measurements were made by a Metrohm digital pH
meter (model: 691, Herisua, Switzerland) with a com-
bined glass electrode.
A 10 µl Hamilton 7105 syringe (Hamilton, Reno, NV,
USA) was used to suspend the drop of the acceptor phase
and to inject it into the graphite furnace atomizer. Sam-
ples were stirred in 10 ml flat-bottom vial containing
Teflon-line septa using an electronic magnetic stirrer
(VWR Scientific, West Chester, PA, USA).
Table 1. Applied conditions for lead determination with GFA system.
Optimum analytical conditions
Lamp current 4 mA
Wavelength 228.8 nm
Spectral bandwidth 0.5 nm
Spectral bandwidth peak height
Purge gas Ar
Back ground correction D2
GFA heating programme
Stage Furnace temperature/˚C Mode Time/s Ar flow rate/L·min–1
Drying 150 ramp 15 1.5
Ashing 400 step 15 1.5
Atomization 1800 step 3 gas stop
Clean up 2500 step 2 1.5

759 S. NAZARI
2.2. Reagents
All reagents used were at least of analytical grade. Water
was deionizer to a resistivity of 18 MΩ cm in a Milli-Q
system (Millipore, Bedford, MA, USA). A lead stock
solution (1000 mg·L–1 Pb) was prepared dissolving high-
purity Pb(NO3)2 (SPEX, Eddison, NJ, USA).Working
solutions were prepared daily in 1% (v/v) HNO3 by proper
dilution of the stock solution. The extraction organic
phase was 1,2 dichloroethane (Merck, Darmstadt, Ger-
many). 3.0% (m/v) Pyrimidine-2-thiol (Merck, Darmstadt,
Germany) in ethanol was used as a complexing agent and
1.5% (m/v) ammonium tetraphenylborate (Merck, Darm-
stadt, Germany) in 1,2 dichloroethane was used as counter
ion. Modifiers of 0.1% (m/v) Pd in HCl 2% (v/v), 0.1%
(m/v) W, 10% (m/v) Mg in water were used.
2.3. Extraction Procedure
Two ml of lead solution was adjusted at pH = 5 and
treated with 0.5 ml of 3.0% (m/v) Pyrimidine-2-thiol was
transferred to a 10 ml vial. Lead formed a cationic com-
plex with Pyrimidine-2-thiol in aqueous solution. The
solution was stirred by magnetic stirrer with a 6 mm stir
bar at optimized speed 600 rpm. A 4 µl of 1,2 dichloro-
ethane and ammonium tetraphenylborate as counter ion
was taken by the Hamilton syringe whose needle was
used to pierce the vial septum. The syringe was clamped
in such a way that the tip of the needle was located at a
fixed position in the sample solution as shown in Figure
1. The syringe plunger was depressed to expose the drop
and the stirring commenced. In the drop, the Pb-Py-
rimidine-2-thiol ammonium tetraphenylborate ion asso-
ciated complex was formed. The Pb-Pyrimidine-2-thiol
cationic complex was extracted from aqueous solution
into the 1,2 dichloroethane as extraction organic phase
and formed ion associated complex with ammonium
tetraphenylborate as counter ion.
After the extraction, the microdrop was retracted and
directly injected into the graphite furnace tube modified
with [W.Pd.Mg] (c) for subsequent determinations. The
different parameters affecting the technique such as sol-
vent, pH, stirring rate, time of extraction, concentration
of Pyrimidine-2-thiol and ammonium tetraphenylborate
were optimized.
2.4. Tube Modification
Mg modifier was used by injecting 0.2% Mg and sample
solution with equal volumes. [(W.Pd) (c) + Pd(i)] modi-
fiers were used for coating containing 40 µg of each of
W and Pd from 0.1% of their solutions at temperatures of
2300˚C and 2100˚C respectively and injecting 10 µl of
0.1% (m/v) Pd on top of 10 µl sample solution (without
extraction). [Pd(c) + Pd(i)] modifier was used as coating
of 60 µg Pd onto the graphite tube at 1800˚C and inject-
ing of 10 µl solution of 0.1% (m/v) Pd on top of 10 µl of
sample solution. [W.Pd.Mg] (c) modifier was used as
coating of 40 µg of each of W, Pd and Mg solution at the
appropriate temperatures. Added of pyrimidine-2-thiol to
lead solution in direct injection without preconcentration
step has not any effect on the signal.
3. Results and Discussion
In order to obtain a high enrichment factor, the effect of
different parameters affecting the complex formation and
extraction conditions such as type and volume of organic
solvent, pH, concentration of chelating agent and counter
ion, extraction time and stirring rate were optimized. One
variable at a time optimization was used to obtain opti-
mum conditions for liquid phase microextraction (LPME)
procedure.
Enrichment factor is defined as the ratio of concentra-
tion of lead in the microdrop phase to concentration of
lead in the aqueous sample. Concentration of lead in the
microdrop phase was calculated from the calibration
graph obtained by direct injection of lead into the modi-
fied graphite furnace tube without any preconcentration
(by compare absorbance of direct injection and after
preconcentration). Addition of complexing agent to the
lead solution in direct injection without preconcentration
step did not any effect on the signal.
3.1. Effect of Type of Modifiers
Several modifiers containing Pd, Ru, Rh, Ir, V, Mo, W,
Ni, Mg, Ascorbic acid, separately or in their combina-
tions, were tested. The results of best performing modifi-
ers are shown in Table 2. [W.Pd.Mg] (c) modifier showed
the best results in contrast to [(W.Pd) (c) + Pd (i)] and
[Pd (c) + Pd (i)] for direct determination of lead.
Figure 1. The schematic setup for liquid phase microextrac-
tion.

S. NAZARI
760
3.2. Effect of Type and Volume of the Extraction
Solvent
The choice of organic solvent used in LPME was a major
consideration. In order to promote analyte transferring
from the donor solution through the organic phase to the
accepter microdrop, the solubility of the neutral analytes
in the organic solvent should be higher than that in the
donor solution and simultaneously the solubility of ionic
analytes should be lower than that in the accepter phase.
Effect of five different solvents, carbon tetrachloride,
dichloromethane, 1,2 dichloroethane, nitrobenzene and
benzyl alcohol was evaluated for the of 2 ml lead solu-
tion with concentration of 0.1 µg·L–1. The results are
given in Figure 2. 1,2 dichloroethane was found to pro-
vide higher extraction efficiency. This may be attributed
to middle polarity of 1,2 dichloroethane, which leads to
the higher solubility of the polar Pb-Pyrimidine-2-thiol
cationic complex and hence higher extraction efficiency.
The influence of drop size was investigated in the
range of 1 - 4 µl. It was found that the absorbance in-
creases with drop volume in the range of 1 - 4 µl. When
drop size exceeded 4 µl, it became too unstable to be
suspended at the needle tip. For this reason, 4 µl drop
volume was used for further studies.
3.3. Effect of Extraction Time
Extraction time is one of the most important factors in
the most of extraction procedures. LPME is a type of
equilibrium extraction, and the optimal extraction effi-
ciency is obtained when equilibrium is established. There-
fore, the extraction time plays a very essential role in the
whole process. The dependence of extraction efficiency
Table 2. Analytical figures of merit for lead determination using different chemical modifiers.
Chemical modifier Detectiona
limit (µg·L–1)
Sensitivityb
(µg·L–1)
Linear range
(µg·L–1) RSD %c
Mg (i)
Ni (i)
0.14
0.18
0.038
0.042
0.28 - 44
0.25 - 29
6.2
5.8
[(W.Rh) (c) + Rh (i)] 0.11 0.05 0.31 - 38 4.6
[Pd (c) + Pd (i)] 0.081 0.032 0.30 - 39 5.1
[W.Pd.Mg] (c) 0.074 0.026 0.22 - 3 3.8
a: Based on 3Sb; b: Calculated by dividing 0.0044 to the slope of calibration curve; c: For 10 replicated analysis of 0.1 µg·L–1 lead.
Figure 2. Effect of type of extraction solvent on the absorbance obtained from LPME.

761 S. NAZARI
upon extraction time was studied within a range of 0 - 30
minutes in the constant experimental conditions. All
measurements were carried out with 0.1 µg·L–1 lead.
Figure 3 shows the absorbance of lead versus extraction
time. The results showed an increase of the lead absorb-
ance up to 8 minutes and leveling off at higher extraction
time. Therefore, 8 minutes was used as the optimum ex-
traction time.
3.4. Effect of pH
The effect of pH on the complex formation and extrac-
tion of lead from water samples was studied within the
range of 3.0 - 9.0. The results, illustrated in Figure 4,
show that the absorbance is nearly constant in the range
of 4.5 - 5.5. In order to obtain high extraction efficiency
and minimize diverse ions interferences, pH 5 was cho-
sen.
3.5. Effect of Pyrimidine-2-Thiol Concentration
The influence of the concentration of pyrimidine-2-thiol
in the aqueous solution on the lead complex formation
was investigated for 0.1 µg·L–1 solution of lead extracted
for 8 minutes. Different concentrations (0.0% - 2.0% m/v)
of pyrimidine-2-thiol were used in the aqueous solution
and its effects on the extraction process are shown in
Figure 5. As can be seen, the efficiency of lead transport
increases with increasing pyrimidine-2-thiol concentra-
tion until 1.0% (m/v) is reached. However, a further in-
crease in the concentration of pyrimidine-2-thiol (up to
1.0%) caused a pronounced decrease in the formation of
lead ion pair. This is most probably due to the competi-
tion of pyrimidine-2-thiol itself with lead-pyrimidine-
2-thiol complex for transfer through the LPME. Hence,
1.0% (m/v) was employed as the optimum concentration
of pyrimidine-2-thiol.
Figure 3. Effect of extraction time on the absorbance of lead
obtained from LPME.
Figure 4. Effect of pH on the absorbance of lead obtained
from LPME.
Figure 5. Effect of concentration of Pyrimidine-2-thiol on
the absorbance of lead obtained from LPME.
3.6. Effect of Ammonium Tetraphenylborate
Concentration into the 1,2 Dichloroethane
Drop
Different concentrations (0.0% - 1.5% m/v) of ammo-
nium tetraphenylborate as counter ion in the drop of 1,2
dichloroethane under the optimum condition described
above were investigated. The results show that by in-
creasing the concentration of ammonium tetraphenylbo-
rate the absorbance increases up to 0.8% (m/v) ammo-
nium tetraphenylborate was present in the drop and lev-

S. NAZARI
762
eling off at higher concentration as shown in Figure 6.
3.7. Effect of Stirring Rate
Magnetic stirring was used to facilitate the mass transfer
process and thus improve the extraction efficiency. The
stirring rate was optimized for extraction process. Figure
7 illustrates the effects of stirring rate on the enrichment
factor increased with increasing of the stirring rate up to
600 rpm, because, in high stirring rate, a relatively large
vortex is formed in the lower region of the organic sol-
vent, but instability of droplet limited the phenomenon,
thus 600 rpm was chosen for further experiment.
3.8. Effect of Salt
The influence of ionic strength was evaluated at 0% - 5%
(m/v) NaCl levels while other parameters were kept con-
stant. As observed in Figure 8, salt addition has no sig-
nificantly effect on extraction recovery. Therefore, all the
extraction experiments were carried out without adding
salt.
3.9. Effect of Foreign Ions
Preconcentration procedures for trace elements in the
high salt content samples can be strongly affected by the
matrix constituents of the sample. The influence of the
common co-existing ions in natural water samples on the
lead recovery was investigated. For this purpose, ac-
cording to the recommended procedure, 2 ml of solution
Figure 6. Effect of concentration of ammonium tetraphenyl-
borate concentration into the 1,2 dichloroethane drop on
the absorbance of cadmium obtained from LPME.
Figure 7. Effect of stirring rate on the absorbance of lead
obtained from LPME.
Figure 8. Effect of salt concentration on the absorbance of
lead obtained from LPME.
that contains 0.1 µg·L–1 of lead and various amounts
from interfering ions, were preconcentrated and deter-
mined. A given spices was considered to interfere if it
resulted in a ±5% variation of the GFAAS signal. The
results are summarized in Table 3, proving that the lead
recoveries were almost quantitative in the presence of an
excessive amount of the possible interfering cations and
anions.

S. NAZARI
763
Table 3. Effect of interferents on the recovery of 0.1 µg·L–1 Pb(II) in water sample using LPME.
Interferent Concentration (µg·L–1) Interferent/Pb (II) ratio Recovery (%)
Na+ 1,000 10,000 98.6
Li+ 100 1,000 100.8
K+ 100 1,000 102.3
Ca2+ 100 1,000 100.1
Mg2+ 100 1,000 99.6
Ba2+ 100 1,000 100.7
Bi3+ 100 1,000 98.2
Mn2+ 100 1,000 97.9
Co2+ 100 1,000 102.1
Al3+ 100 1,000 99.2
Fe2+ a 100 1,000 99.7
Fe3+ a 100 1,000 99.3
Ni2+ 100 1,000 98.4
Sn4+ 100 1,000 99.1
Zn2+ 100 1,000 100.0
Cr3+ 100 1,000 98.6
Ag+ 30 300 98.1
Cd2+ 30 300 98..4
Cu2+ 30 300 99.4
Si4+ 30 300 98.5
Hg2+ 10 100 97.9
Cl– 1,000 10,000 98.2
Br– 1,000 10,000 98.8
3
NO 100 1,000 101.1
CH3COO– 100 1,000 99.5
SCN– 100 1,000 99.3
2
4
SO 

100 1,000 100.0
2
3
CO
3
100 1,000 98.6
4
PO
2
100 1,000 99.2
28
SO
2
100 1,000 99.7
3
SeO 100 1,000 98.4
aMasked with F-.
3.10. Analytical Figure of Merits
Under the optimum conditions described above, the ana-
lytical performance characteristics of the proposed method
are listed in Table 4.
The calibration graph, obtained by analysis of 8 stan-
dards with different known concentrations of Pb, was
linear with a correlation coefficient of 0.9996 at levels
near the detection limits and up to at least 4.5 µg·L–1 [A
= 0.0021 (±0.002) + 0.25068 (±0.0021)C], where A is
the absorbance and C is Pb2+ concentration in µg·L–1.
The calibration graph was linear in the range of 0.01 -
12 µg·L–1 with correlation coefficient of 0.9975 under
the optimum conditions of the recommended procedure.
The equation of line is A = 0.0045 (±0.0062) + 0.48C
(±0.0085), where A is the absorbance and C is concen-
tration of lead in µg·L–1 in the initial solution. The detec-
tion limit was calculated as three times the standard de-
viation of the peak absorbance for injection of 4 µl of ten
extractions of the blank, using the liquid phase microex-
traction procedure. The detection limit was calculated to
be 0.0072 µg·L–1 with absolute value of 28.8 fg for 4 µl
injection into the graphite furnace. The characteristic
concentration was 0.0065 µg·L–1 equivalent to a charac-

S. NAZARI
764
teristic mass of 26 fg. The relative standard deviation for
(RSD) for ten replicate measurement of 0.1 µg·L–1 and
0.4 µg·L–1 lead was 4.5% and 3.8% respectively. The
enrichment factor (EF) was obtained from the slope ratio
of calibration graph after and before extraction, which
was about 525. The extraction recovery (R%) was 94%
which was calculated by Equation (1).
R% = (Vdrop/Vsolution) × EF × 100 (1)
3.11. Application
In order to establish the validity of the proposed proce-
dure, the method has been applied to the determination
of lead in standard reference materials NIST 1643e,
NIST 1640 (National Institute of Standard and Technol-
ogy NIST, USA), JB-1, JB-1a and JB-2 as powder ob-
tained from geological survey of Japan (GSJ). The pow-
der was dissolved in 15 ml of a mixture of 500 ml HF,
165 ml H2SO4 and 40 ml HNO3 at 150ºC in a teflon
beaker overnight. To show the applicability of the
method, seawater from Caspian Sea and local tap water
was analyzed for its lead content. The results obtained
are presented in Table 5. As shown by the results in Ta-
ble 5, good agreement between certified and found val-
ues was obtained at a 95% confidence level, indicating
that calibration carried out using aqueous standard solu-
tions submitted to the LPME procedure results in good
accuracy. To assure the homogeneity and statistical va-
lidity of the method, a paired t-test was applied to the
group of results; the determined “t” value was 0.187,
which is below the reference t-value for a 95% confi-
dence interval (t = 2.78).
Table 4. Analytical characteristics of LPME-GF AAS for determination of lead.
Parameter Analytical feature
Linear range (µg·L–1) 0.01 - 12
Correlation coefficient (r2) 0.9975
Limit of detection (µg·L–1)(3σ, n = 10) 0.0072
Repeatability (RSD %) (n = 10, 0.1 µg·L–1) 4.5
Repeatability (RSD %) (n = 10, 0.4 µg·L–1) 3.8
Enrichment factor (EF) a 525
Sample Volume (ml) 2
Sample introduction Volume (µl) 4
Sample preparation time (min) 8
Recovery (%) 94
aEnrichment factor is the slope ratio of calibration graph after and before extraction.
Table 5. Results obtained for the determination of Pb in SRM using LPME-GFAAS with a modified graphite tube (n = 3;
t-Student applied for 95% confidence le vel; t = 0.1874 for the group of results).
Sample Lead added (µg·L–1) Lead found (µg·L–1) Recovery %
Sea water* 0 3.7 ± 0.1 ―
0.2 0.196 ± 0.01 98.3
0.4 0.39 ± 0.02 97.4
0.6 0.59 ± 0.04 99.2
Tap water 0 0.00
0.2 0.202 ± 0.01 101
0.4 0.41 ± 0.03 102.5
Reference Material Certified value Measured value Recovery %
JB-1a 10.0 (µg·g–1) 9.93 ± 0.41 ( µg·g–1) 99.3
JB-1aa 6.76 (µg·g–1) 6.66 ± 0.32 ( µg·g–1) 99.0
JB-2a 5.36 (µg·g–1) 5.19 ± 0.26 ( µg·g–1) 96.9
NIST 1643eb
NIST 1640b
19.63 ± 0.21 (µg·L–1)
27.89 ± 0.14 (µg·L–1)
20.07 ± 0.84 (µg·L–1)
28.84 ± 1.4 (µg·L–1)
102.2
103.4
*Collected from Caspian Sea; aObtained from geological survey of Japan, GSJ; bFrom National Institute of Standard and Technology NIST (USA).

765 S. NAZARI
Table 6. Characteristics performance data obtained by using LPME and other preconcentration techniques for determina-
tion of lead.
LOD Reference Sample preparation
time (min)
Sample
volume (ml)
Enrichment
factor
RSD
(%) (µg·L–1)
Method
31 > 6 500.0 543 6.3 0.39
Liquid–liquid extraction and
micro volume back-extraction–FAAS
32 > 20 50.0 125 3.0 16 Co-precipitation-FAAS
33 4 300 30 4.7 6.1 Off-line-SPE–FAAS
34 4 39 330 2.6 0.8 On-line-SPE–FAAS
35 30 50.0 50 3.5 1.1 CPE–FAAS
Represented
method
8 2 525 3.8a, 4.5b 0.0072 LPME-ETAAS
aLead concentration was 0.1 µg·L–1 for which RSD was obtained; bLead concentration was 0.4 µg·L–1 for which RSD was obtained.
3.12. Comparison with Other Methods
Table 6 indicates the limit of detection (LOD), the rela-
tive standard deviation, the sample preparation time and
the sample volume in the LLE-microvolume back-ex-
traction [31], co-precipitation [32], off-line SPE (Solid
Phase Extraction) [33], on-line SPE [34] CPE and (Cloud
Point Extraction) [35] for the extraction and determina-
tion of lead in water samples. The comparison of the
results exhibits that LOD and the enrichment factor (or
enhancement factor) in the present method were better
than those of the other methods.
4. Conclusions
The results show a very promising technique for the de-
termination of lead in variety of samples at µg·L–1 levels
without the needs for any sophisticated device. Apart
from extremely high sensitivity and relatively free from
interferences, the procedure is very simple, fast and
benefits a very low detection limit. The method is also
inexpensive and reproducible and applied for sea and tap
water samples. The method can also be applied for
analysis of real samples such as biological and botanical
samples.
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