Pivaloyl chloride as a new derivatization agent for parabens and its application in simultaneous derivatization and air-assisted liquid–liquid microextraction of the analytes in hygiene and personal care products

Article abstract of DOI:10.1007/s13738-019-01690-7

An air-assisted liquid–liquid microextraction method using of an extraction solvent (less dense than water) has been proposed for simultaneous derivatization and extraction of some p-hydroxybenzoic acid esters (parabens) in different samples before their

Full text of DOI:10.1007/s13738-019-01690-7

Journal of the Iranian Chemical Society
https://doi.org/10.1007/s13738-019-01690-7
ORIGINAL PAPER
Pivaloyl chloride as a new derivatization agent for parabens
and its application in simultaneous derivatization and air‑assisted
liquid–liquid microextraction of the analytes in hygiene and personal
care products
Mir Ali Farajzadeh1,2 · Mehri Bakhshizadeh Aghdam · Mohammad Reza Afshar Mogaddam ·
1
3
Ali Akbar Alizadeh Nabil4
Received: 12 November 2018 / Accepted: 9 May 2019
©
Iranian Chemical Society 2019
Abstract
An air-assisted liquid–liquid microextraction method using of an extraction solvent (less dense than water) has been pro-
posed for simultaneous derivatization and extraction of some p-hydroxybenzoic acid esters (parabens) in diꢀerent samples
before their determination with gas chromatography-ꢁame ionization detection. The analytes are derivatized by a fast reac-
tion occurring between parabens and pivaloyl chloride (as a derivatization agent) and extracted into toluene (as an extrac-
tion solvent) under mild conditions in a test tube. After performing the microextraction procedure, a home-made device
(
an inverse funnel having a capillary tube) is placed into the tube. A thin ꢂlm of the extractant accumulated on the surface
of the aqueous phase is transferred into the capillary part of the device. A fraction of the organic phase is removed by a
microsyringe and injected into the separation system for analysis. Under optimum conditions, detection and quantiꢂcation
−
1
−6
−5
−5
limits were between 0.60 and 1.0; and 1.7 and 3.1 ng mL in solution; and 6.0×10 and 1.0×10 ; and 1.7×10 and
−5
−1
3
.1×10 g kg in solid, respectively. The enhancement and enrichment factors were obtained in the ranges of 492–650 and
3
80–410, respectively. Relative standard deviations were less than 6% (n=6) for intra- and less than 9% (n=4) for inter-day
−
1
precisions calculated at a concentration of 50 ng mL of each analyte. The calibration graphs were linear with coeꢃcients
of determination≥0.994. Finally, the selected parabens were successfully analyzed in various hygiene and personal care
products by the proposed method.
Keywords Gas chromatography · Hygiene · Parabens · Derivatization · Air-assisted liquid–liquid microextraction
Abbreviations
AALLME Air-assisted liquid–liquid microextraction
EF
Enrichment factor
Methyl paraben
Propyl paraben
MeP
PrP
ER
Extraction recovery
Enhancement factor
Ethyl paraben
EnF
EtP
GC
Gas chromatography
Introduction
4
-Hydroxybenzoic acid esters (parabens) are widely
*
Mir Ali Farajzadeh
employed as preservatives in hygiene, cosmetic, and per-
sonal care products due to their broad spectrum of anti-
microbial activity, ideal physicochemical properties, low
toxicity, worldwide legislative acceptance, biodegradability,
and cost [1, 2]. However, some studies have shown that
parabens can absorb through the skin [3] and cause endo-
crine disrupting eꢀect [4–6]. To minimize possible risks
to human health, European Union law has restricted the
use of parabens in hygiene and personal care products. The
mafarajzadeh@yahoo.com; mafarajzadeh@tabrizu.ac.ir
1
2
3
4
Department of Analytical Chemistry, Faculty of Chemistry,
University of Tabriz, Tabriz, Iran
Engineering Faculty, Near East University, 99138 Nicosia,
North Cyprus, Mersin 10, Turkey
Food and Drug Safety Research Center, Tabriz University
of Medical Science, Tabriz, Iran
Pharmaceutical Analysis Research Center, Tabriz University
of Medical Sciences, Tabriz, Iran
Vol.:(0
1
123456789)
3

Journal of the Iranian Chemical Society
maximum authorized concentration (MAC) of individual
parabens in hygiene and personal care products is 0.04%,
and the MAC of overall parabens is 0.08% [7]. Conse-
quently, the development of an analytical method to analyze
their levels in personal care products and cosmetic is need-
ful. Many papers on the evaluation of parabens in diꢀerent
samples by high-performance liquid chromatography [8,
method has been used in diꢀerent samples [33, 34]. Despite
its advantages, relatively high consumption of dispersive
solvent (usually 1 vs. 5 mL aqueous phase) and increasing
the solubility of the analytes in the aqueous phase owing
to the presence of the disperser are disadvantages of the
method. To resolve these problems, some disperser solvent-
less techniques such as vortex-assisted liquid–liquid micro-
extraction [35], salt-assisted liquid–liquid microextraction
[36], ultrasound-assisted emulsiꢂcation microextraction,
and air-assisted liquid–liquid microextraction (AALLME)
[37–39] have been proposed. The turbid solution in AAL-
LME is formed by repeatedly sucking and injecting of a
mixture of an aqueous sample solution and a few microliters
of an extraction solvent with a syringe in a test tube without
using disperser solvent. In a classical AALLME procedure,
a water-immiscible organic solvent with density greater
than water is used. However, most of these solvents are the
halogenated solvents which are hazardous, and their han-
dling is diꢃcult in laboratory. To solve this problem, these
solvents are replaced by lighter than water density organic
solvents which are low toxic for human and environment.
The main goal of this study was to develop a lighter than
water organic solvent AALLME procedure for simultane-
ous derivatization and extraction of three parabens in dif-
ferent samples. In this process, the analytes are derivatized
using a new derivatization agent (pivaloyl chloride) and the
derivatized analytes are extracted into a lighter than water
organic solvent which is safer than heavier organic solvents.
To collect the extraction solvent, a simple device is fabri-
cated. The device is an inverse funnel which is placed into
a convenient glass test tube. The proposed method has high
enhancement factors (EnFs) and low detection limits. Also,
symmetry of the chromatographic peaks of the derivatized
products improves with respect to those of the un-derivat-
ized analytes. The other improvement of the method is the
collection of the extractant after performing the method by
a new device applicable for the extraction solvents lighter
than water.
9
], gas chromatography (GC) [10–13], ultra performance
liquid chromatography [14–18], capillary electrophoresis
19], and micellar electrokinetic chromatography [20] have
[
been published. Due to low molecular mass and volatility of
parabens, GC is a good option for their analysis. But, they
are too polar to be properly separated by GC, and hence,
they usually require derivatization before GC analysis for
improvement of chromatographic analysis performance.
Silylation [21, 22] and acetylation [23, 24] are two common
derivatization methods for GC analysis of parabens. These
methods have their own limited shortcoming, for example,
silylation reagents are moisture-sensitive and some cares
must be taken to maintain inert and water-free environment
to prevent their deactivation or reduce unwanted side reac-
tions. Moreover, derivatization procedures using the men-
tioned reagents involve additional steps which increase the
time required for sample preparation [25]. In addition to the
derivatization, an appropriate sample preparation method is
frequently required to isolate the analytes from the complex
matrix, concentrate, and make them compatible with the
instrumental analytical techniques. Liquid–liquid extraction
(
LLE) [26], and solid-phase extraction [27] are common
pretreatment procedures. However, some disadvantages
such as large organic solvent consumption, high cost, and
time-consuming make them unappealing for routine analy-
sis. To eliminate these drawbacks, microextraction tech-
niques have been developed. Liquid phase microextraction
(
[
LPME) [28] and solid-phase microextraction (SPME)
29] are examples of the microextraction techniques which
have been used for the extraction and preconcentration of
parabens. The LPME is a simple, rapid, and inexpensive
sample preparation method compared to LLE and SPME
procedure [30, 31]. In this procedure unlike LLE, only a
few microliters of an organic solvent are used. Also, there
is no need to expensive and fragile ꢂbers used in SPME.
In 2006, Assadi and coworkers developed a new microex-
traction method namely dispersive liquid–liquid microex-
traction [32]. This method is based on the dispersion of an
extraction solvent (water-immiscible solvent) with the aid of
a disperser solvent (water-miscible solvent) into an aqueous
sample. Fine droplets of the extraction solvent with a large
contact area with the sample solution are formed in this step
which lead to achieve high preconcentration and extraction
eꢃciency. The advantages of this method are the simplic-
ity of operation, rapidity, low cost, relatively high extrac-
tion recovery (ER), and high enrichment factor (EF). This
Experimental
Chemicals and reagents
Three parabens including methyl paraben (MeP), ethyl
paraben (EtP), and propyl paraben (PrP) with purities
>98% were supplied from Sigma–Aldrich (St. Louis, MO,
USA). The tested extraction solvents including n-hexane,
n-octanol, toluene, and xylene were from Merck (Darm-
stadt, Germany). 3-Picoline (as a catalyst), analytical rea-
gent grade sodium chloride, and methanol were from Merck.
Pivaloyl chloride as a derivatization agent was obtained
from Sigma–Aldrich. A standard solution of the analytes
1
3

Journal of the Iranian Chemical Society
was prepared in methanol at a concentration of 1000 mg
centrifugation at 5000 rpm for 10 min, 1 mL of the super-
natant was diluted at a ratio of 1:4 with deionized water and
subjected to the proposed method.
−
1
L
(each analyte) and stored in a refrigerator at 4 °C. A
−
1
standard solution of the analytes (each 500 mg L ) was
prepared in a mixture of 3 mL toluene, 0.1 mL 3-picoline,
and 1 mL pivaloyl chloride and injected into the separation
system (three times in each day) for quality control. Also,
the obtained peak areas were used in the calculation of EFs,
EnFs, and ERs. Working standard solutions were prepared
daily by appropriate dilutions of the standard solution of the
parabens prepared in methanol with deionized water (Ghazi
Company, Tabriz, Iran).
Procedure for derivatization and microextraction
of parabens
−1
5
.0 mL of an aqueous standard solution (1 mg L of each
analyte) or sample (see “Samples” section) along with 7.5%,
w/v, NaCl were placed into a 10-mL glass test tube. Then 40
µL catalyst (3-picoline), 20 µL derivatization agent (pivaloyl
chloride), and 17 µL extraction solvent (toluene) were trans-
ferred into the solution. The mixture was repeatedly aspi-
rated into a glass syringe (10-mL) and then expelled into the
tube via the syringe needle (ꢂve times). A cloudy solution
resulted from the dispersion of the ꢂne droplets of toluene
into the aqueous solution was formed. In this step, the ana-
lytes were rapidly derivatized by pivaloyl chloride and the
resultant derivatives were extracted into the toluene droplets.
The mixture was centrifuged for 5 min at 5000 rpm. A thin
ꢂlm of the organic phase was ꢁoated on the surface of the
aqueous phase. The collection device was placed into the
tube, and the extractant sat at its narrow section (10 ± 0.5
µL). An aliquot (1 μL) of the collected organic phase was
removed using a 1-µL GC microsyringe and injected into
the separation system for analysis. The device and the devel-
oped derivatization/microextraction procedure are shown in
Scheme 1.
Instrumentation
The analytes separation and detection were performed with a
Shimadzu 2014 gas chromatograph (Kyoto, Japan) equipped
with a ꢁame ionization detector (FID) and a split/splitless
injector maintained at 290 °C in a splitless/split mode (sam-
pling time 1 min and a split ratio of 1:10). Helium (99.999%,
Gulf Cryo, United Arab Emirates) was used as the carrier
−
1
gas at a constant linear velocity of 30 cm s . The separa-
tion was carried out on an RTX-1 (30 m×0.25 mm i.d., ꢂlm
thickness 0.25 μm) capillary column purchased from Restek
Corporation (Bellefonte, USA). The column oven tempera-
ture was programmed as follows: initial temperature 100 °C
−
1
(
held 1 min) and increased by the rates of 10 °C min until
−
1
−1
1
75 °C, 2 °C min until 200 °C, and then 30 °C min
to 290 °C (held 3 min). The FID temperature was main-
tained at 290 °C. Injections were performed using a zero
dead volume microsyringe (1-µL) obtained from Hamilton,
Switzerland. Hydrogen gas was generated with a hydrogen
generator (OPGU-1500S, Shimadzu, Japan) for FID at a ꢁow
EF, ER, and EnF calculation
−
1
−1
EF is calculated by the following equation:
C
EF =
rate of 30 mL min . The ꢁow rate of air was 300 mL min .
Separation in gas chromatography-mass spectrometry (GC-
MS) was carried out on an HP-5 MS (30 m×0.25 mm i.d.,
ꢂlm thickness 0.25 µm) capillary column (Hewlett-Packard,
Santa Clara, USA). Helium (99.9999%, Gulf Cryo, United
col
(1)
C
0
where C and C are the analyte concentration in the col-
col
0
−
1
Arab Emirates) was employed at 1.0 mL min as the car-
rier gas. Temperature programming of the column oven and
injector temperature used in the GC-FID experiments was
utilized in GC-MS separation. Library searching was per-
formed using the commercial NIST library. Hettich centri-
fuge model D-7200 (Kirchlengern, Germany) was used in
AALLME to expedite phase separation.
lected organic phase and the initial concentration of the
analyte in the sample, respectively. C is obtained by com-
col
paring the results obtained in two following cases: by direct
injection of the standard solution of the analytes prepared in
a mixture of toluene, 3-picoline, and pivaloyl chloride (see
“Chemicals and reagents” section) and injecting the extract-
ant after doing the method.
The following equation was used in ER calculation:
Samples
ꢀ
ꢁ
n
C
× V
V
col
col
col
col
ER =
× 100 =
× 100 =
× EF × 100
Hygiene and personal care products including toothpaste,
sunscreen, hair musk, and face wash gel were purchased
from local vendors (Tabriz, Iran). Piroxicam topical gel
was bought from local pharmacies. In order to extract the
analytes from the samples, 1 g of each sample was mixed
with 10 mL methanol and sonicated for 10 min. After
n
C × V
0
V
aq
0
aq
(
2)
where n is total analyte amount, and n is the extracted
0
col
amount of analyte. V and V are the volumes of the col-
col
aq
lected organic phase and aqueous solution, respectively.
EnF is determined by the following equation:
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3

Journal of the Iranian Chemical Society
Scheme 1 Extraction device (a)
and air-assisted liquid–liquid
microextraction and derivatiza-
tion procedure (b)
slopeder
EnF =
slopedir
(3)
slope is the calibration curve slope after doing the derivat-
der
ization/microextraction method, and slope is the calibra-
dir
tion curve slope of the direct injection of standard solutions
prepared in methanol.
Results and discussion
Selection of extraction solvent
Choosing an appropriate extraction solvent is a key issue in
an AALLME method in order to reach an eꢃcient extrac-
tion. An extraction solvent in AALLME procedure should
meet some requirements such as lower density compared to
water (in this study), sparingly soluble in water, high extrac-
tion aꢃnity toward the compounds of interest, good gas
chromatographic behavior, and forming a cloudy solution
during the sucking and injecting cycles. Considering these
requirements, four low-density solvents including n-octanol
Fig. 1 Selection of extraction solvent. Extraction conditions: Aque-
−1
ous solution volume, 5 mL; analytes concentrations, 1 mg L of each
analyte; catalyst type, 3-picoline; catalyst volume, 25 μL; pivaloyl
chloride volume, 25 µL; extraction solvent, xylene (20 μL), toluene
(
25 μL), n-octanol (14 μL), and n-hexanol (22 μL); extraction cycle
numbers, 5 times; centrifugation rate 5000 rpm; and centrifugation
time, 5 min. The error bars indicate the minimum and maximum of
three determinations
−
1
−1
(
(
d = 0.82 g mL ), n-hexanol (d = 0.65 g mL ), toluene
Optimization of extraction solvent volume
−1
−1
d=0.86 g mL ), and xylene (d=0.77 g mL ) were tested.
The initial volumes of the solvents were chosen diꢀerent
to obtain an equal volume for the collected phase (10± 0.5
µL). Therefore, 20, 25, 22, and 14 µL of xylene, toluene,
n-hexanol, and n-octanol were used for the extraction of the
analytes from the aqueous solution, respectively. According
to the obtained results (Fig. 1), toluene is more eꢃcient than
other studied solvents owing to chemical structure similarity
of toluene and the analytes. So toluene was chosen as the
extractant in the next experiments.
The volume of extraction solvent is an important parameter
that has impacts on the collected organic phase volume and
EF. The extraction solvent volume should be adequate for
extraction of the analytes as much as possible but does not
dilute them. For this purpose, diꢀerent volumes of toluene
(25–45 µL) were selected. The obtained data showed that
(data not shown here) by increasing toluene volume at the
mentioned range, the analytical signals decreased contin-
ually. It can be attributed to the dilution of the extracted
1
3

Journal of the Iranian Chemical Society
analytes in the collected phase due to increasing in the col-
lected phase volume from 10 to 32 µL. It is notable that at
volumes less than 25 µL, the volume of the collected phase
was low and its removal was diꢃcult. So 25 µL toluene was
selected as the optimal volume of the extraction solvent for
the further steps.
acid scavenger and accelerates the derivatization reaction.
Therefore, optimization of the catalyst volume is neces-
sary for the developed method. For this purpose, diꢀerent
experiments were carried out by adding various volumes
of 3-picoline (20–50 µL). Based on the obtained results
(Fig. 3), the peak areas of the derivatives increase by
increasing the volume of 3-picoline up to 40 µL and then
decrease. It should be noted that by increasing 3-pico-
line volume, the excess of 3-picoline is dissolved into the
extraction solvent and the collected phase volume is also
increased, and hence, concentrations of the extracted ana-
lytes into organic phase are decreased. Subsequently, 40
µL of 3-picoline was used in further experiments.
Optimization of derivatization agent volume
In this work, derivatization was performed in an aqueous
phase and for the ꢂrst time pivaloyl chloride was used to
convert the parabens to their trimethyl acetyl derivatives.
In the derivatization reaction, hydrogen of phenolic group
of the parabens replaces with a trimethyl acetyl group. This
leads to produce the derivatives which are less polar and
more volatile. This improves the chromatographic property
of the analytes. The volume of pivaloyl chloride can aꢀect
the derivatization yield, the collected phase volume, and the
extraction eꢃciency. To study the eꢀect of derivatization
agent volume, diꢀerent volumes of pivaloyl chloride (15,
Study of salt addition
Salting-out eꢀect is observed in most extractive methods.
To evaluate the salting-out eꢀect, the developed procedure
was performed on the working solutions containing vari-
ous concentrations of sodium chloride (0, 2.5, 5.0, 7.5, and
10%, w/v) using 25, 22, 19, 17, and 13 µL of the extraction
solvent, respectively, to reach a constant volume (10± 0.5
µL) of the collected phase. The obtained results in Fig. 4
reveal that by increasing sodium chloride concentration
up to 7.5%, w/v, the analytical signals increase and then
decrease gradually. It seems that up to 7.5%, w/v, sodium
chloride, the salting-out eꢀect leads to an improvement in
the migration of the analyte into the organic phase. The
reducing in extraction eꢃciency at a high concentration
of sodium chloride (10%, w/v) can be attributed to the
increased viscosity of the aqueous phase. Considering the
results, the next experiments were carried out in the aque-
ous solutions containing 7.5%, w/v, sodium chloride and
17 µL toluene was used as the extraction solvent.
2
0, 25, 30, and 35 μL) were examined. According to the
obtained results in Fig. 2, the analytical signals increase by
increasing the volume of pivaloyl chloride up to 20 μL and
then reduce. It is concluded that at 15 μL, the amount of piv-
aloyl chloride is not suꢃcient for complete derivatization. It
is noted that in the volumes more than 20 μL pivaloyl chlo-
ride, decreasing in the analytical signals can be attributed
to dilution eꢀect by increasing the volume of the collected
organic phase upon dissolving the excess of the derivatiza-
tion agent into the organic phase. Finally, 20 μL pivaloyl
chloride was chosen for the next experiments.
Optimization of catalyst volume
Parabens are weak acids and addition of an alkaline cata-
lyst such as 3-picoline to the aqueous solution can improve
their derivatization yield and rate. 3-Picoline acts as an
Fig. 2 Study of pivaloyl chloride volume. Extraction conditions are
the same as those used in Fig. 1, except 25 µL toluene was used as the
extraction solvent
Fig. 3 Study of catalyst volume. Extraction conditions are the same
as those used in Fig. 2, except 20 µL pivaloyl chloride was used
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Journal of the Iranian Chemical Society
Study of centrifugation time and rate
To optimize the centrifugation time and rate, these
parameters were examined in the ranges of 1–7 min and
2
000–7000 rpm, respectively. The obtained results (data not
shown) showed that there is no signiꢂcant diꢀerence in peak
areas of the analytes at high centrifuging time and speed.
Hence, 5 min and 5000 rpm were chosen in the following
experiments, for centrifuging time and speed, respectively.
Analytical features of the proposed method
The method developed in this study was validated in the
view of the following features: limit of detection (LOD),
limit of quantiꢂcation (LOQ), EF, ER, EnF, coeꢃcient of
Fig. 4 Eꢀect of salt addition on the performance of the method.
Extraction conditions are the same as those used in Fig. 3, except 40
µL 3-picoline was used
2
determination (r ), linear range, and repeatability expressed
as relative standard deviation (RSD). The results are listed
in Table 1. The LODs and LOQs (calculated as S/N = 3
and 10, respectively) were in the ranges of 0.60–1.0 and
−
1
−6
−5
1
1
.7–3.1 ng mL in solution (6.0 × 10 – 1.0 × 10 and
−
5
−5
−1
.7 × 10 – 3.1 × 10 g kg in solid), respectively. The
2
r obtained in the range of 0.994–0.996 certiꢂed the good
linearity of the developed method throughout the studied
levels. The precision of the developed method was evalu-
−
1
ated by analyzing the standard solutions (50 ng mL of
each analyte) on the same day and four consecutive days.
The RSDs varied from 4–6 and 7–9% for intra- (n=6) and
inter-day (n=4) precisions, respectively. The ERs and EFs
were in the ranges of 76–82% and 380–410, respectively.
On the other hand, good EnFs ranging from 492 to 650 were
obtained due to adding an alkyl group on the analytes by
performing the derivatization reaction. This enhanced FID
response toward the analytes. It is noted that the obtained
Fig. 5 Study of extraction numbers. Extraction conditions are the
same as those used in Fig. 4, except 7.5%, w/v, sodium chloride was
used
−6
−5
−1
LODs (6.0×10 – 1.0×10 g kg ) in this study are com-
−
1
pletely lower than the MACs (0.04% or 0.4 g kg ) of the
parabens in the studied samples.
Optimization of extraction cycles number
In this study, the mixture of an aqueous solution, the
extraction solvent, and the catalyst was repeatedly sucked
into a glass syringe and then expelled into a test tube.
Through this action, the analytes convert to the related
nonpolar derivatives and extracted into the dispersed
extraction solvent. So the number of suction/injection
cycles which deꢂned as the “numbers of extraction” can
aꢀect the method eꢃciency and should be optimized.
To some extent similar to multiple batch extraction, it is
predictable that by increasing extraction numbers, ERs
should be increased, too. The eꢀect of extraction num-
bers was evaluated in the range of 1–7 times. The results
in Fig. 5 show that by increasing extraction numbers till
the 5th cycle, analytical signals increase and then remain
nearly constant. Consequently, 5 times of extraction were
selected for the next studies.
Real samples analysis
In order to investigate the performance of the developed
method, some hygiene and personal care products includ-
ing sunscreen, hair musk, toothpaste, face wash gel, and
piroxicam topical gel were analyzed under the optimum
experimental conditions. All samples were analyzed in trip-
licate. Typical GC-FID chromatograms of these samples are
shown in Fig. 6. According to these chromatograms, there
are two suspected peaks eluted in the retention times belong
to MeP and PrP in sunscreen and face wash gel samples. To
identify these peaks, the samples were also injected into
GC-MS after performing the proposed method. The pres-
ence of the mentioned analytes in the above samples was
veriꢂed from GC-MS data. In the case of face wash gel, GC-
total ions current-MS chromatogram along with mass data
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Journal of the Iranian Chemical Society
Table 1 Quantitative features of the derivatization/AALLME-GC-FID method for the selected analytes
Analytes LODa
LOQb
LRc
r2d
RSD%e
EF± SDf EnF± SDg ER± SDh
In solution In solid
In solution In solid
Intra-day Inter-days
−
1
−1
(
ng mL
)
sample
(ng mL
)
sample
−1
−1
(
g kg
)
(g kg
)
5
6
6
−5
−5
−5
MP
EP
PP
1.0
0.60
0.70
1.0×10−
3.1
1.7
2.2
3.1×10
1.7×10
2.2×10
3.1–12,000 0.994
1.7–12,000 0.996
2.2–12,000 0.995
4
6
6
9
7
8
380± 25 492± 25
410± 20 650± 23
400± 30 610± 20
76± 5
82± 4
80± 6
−
6.0×10
7.0×10−
a
Limit of detection (S/N=3)
b
c
d
e
Limit of quantiꢂcation (S/N=10)
−1
Linear range (ng mL
)
Coeꢃcient of determination
Relative standard deviation (n=6, C=50 ng mL of each analyte) for intra- and (n=4, C=50 ng mL−1 of each analyte) for inter-day preci-
−1
sions
f
Enrichment factor± standard deviation (n=3)
g
Enhancement factor± standard deviation (n=3)
Extraction recovery± standard deviation (n=3)
h
are summarized in Table 2. Other samples were free of the
studied parabens. The matrix eꢀect was investigated using
the added-found method. The samples were spiked with the
−
3
−2
analytes at two concentrations (2.5×10 and 1.25×10
−
1
g kg of each paraben) and subjected to the presented pro-
cedure. Mean relative recoveries (compared to recoveries
achieved in deionized water spiked at the related concentra-
tions) were obtained in the range of 83–107% (Table 2). The
obtained relative recoveries show that samples matrices have
a little eꢀect on the performance of the method.
Comparison of the presented method with other
methods
Some analytical characteristics including EF, LOD, RSD,
and LR of the developed method and other previously pub-
lished methods for determining parabens in various samples
are listed in Table 3. According to the results, the obtained
LODs in the presented method are less than those of the
other mentioned methods. Repeatability of the developed
method is satisfactory, and its RSD % is better than or com-
parable with the others. In comparison with others, this
method has higher EFs. This method uses low volumes of
organic reagents and performs microextraction and deri-
vatization in a single step. This method is economical, fast,
sensitive, and simple.
Fig. 6 Typical GC-FID chromatograms of (A) face wash gel spiked
−1
with the analytes at a concentration of 250 mg kg of each paraben,
(
B) unspiked face wash gel, (C) sunscreen spiked with the analytes
−1
at a concentration of 250 mg kg (each analyte), (D) unspiked sun-
screen, (E) direct injection of derivatized parabens in toluene (each
−
1
analyte 250 mg L ), and (F) standard solution of the analytes in
−1
methanol (each analyte 4000 mg L ). In chromatograms (A) – (D),
the method was done and 1 µL of the extractant was analyzed by GC-
FID. Peaks identiꢂcation: (1) MeP, (2) EtP, (3) PrP, (4) derivatized
MeP, (5) derivatized EtP, and (6) derivatized PrP
is given in Fig. 7. The concentrations of the analytes in sun-
screen and face wash gel calculated based on GC-FID data
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Journal of the Iranian Chemical Society
Fig. 7 Typical GC-total ions current-MS chromatogram of face wash gel after performing the proposed method (a), and mass spectra of b scan
1
231 (retention time 23.1 min), c derivatized MeP, d scan 1536 (retention time 25.3 min), and e derivatized PrP
Conclusions
a new device was utilized. The developed method has some
advantages such as ease of operation, high EFs and EnFs,
and acceptable repeatability. Moreover, it is economical and
less hazardous for the environment due to the low consump-
tion of organic solvents. Derivatization and extraction were
performed in a single step. Fast derivatization at room tem-
perature was occurred.
In this work, an easy and fast AALLME method using an
extraction solvent lighter than aqueous phase followed by
GC-FID analysis was proposed in the determination of
parabens in various samples. The derivatization agent was
pivaloyl chloride which was used for parabens for the ꢂrst
time. To collect the extractant after performing the method,
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Journal of the Iranian Chemical Society
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Journal of the Iranian Chemical Society
Table 3 Comparison of the
proposed method with other
methods in the extraction and
determination of the selected
parabens
LRa
RSD%b
LODc
EFd
Method
Sample
References
DLLME-GC-FIDe
HF-LPME-GC-FID
DLLME-GC-FID
Water
Facial tonic
–
–
5.9–7.4
4.5–8.9
2–3
2.5–22
5.1–18
5.0–15
70–210
–
100–276
[24]
[37]
[33]
f
e
Personal care
products and
food samples
Hygiene and
personal care
products
5–30,000
AALLME–GC–FIDg
3.1–12,000
4–6
0.60–1.0
380–410
This work
a
Linear range (ng mL−1
)
b
Relative standard deviation
c
d
e
f
Limit of detection (ng mL−1)
Enrichment factor
Dispersive liquid–liquid microextraction-gas chromatography-ꢁame ionization detection
Hollow ꢂber-liquid phase microextraction-gas chromatography-ꢁame ionization detection
g
Air-assisted liquid–liquid microextraction-gas chromatography-ꢁame ionization detection
Acknowledgments The authors wish to thank the Research Council of
18. M. Mincea, I. Lupşa, I. Talpoş, V. Ostafe, Acta Chromatogr. 21,
University of Tabriz for the ꢂnancial support.
591 (2009)
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