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Journal of Chromatography A
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agnetic molecularly imprinted nanoparticles based on grafting polymerizationor selective detection of 4-nitrophenol in aqueous samples
li Mehdiniaa,∗, Tohid Baradaran Kayyalb, Ali Jabbarib, Mohammad Ovais Aziz-Zanjanib, Ehsan Ziaeib
Department of Marine Science, Iranian National Institute for Oceanography, Tehran, IranDepartment of Chemistry, Faculty of Science, K. N. Toosi University of Technology, Tehran, Iran
r t i c l e i n f o
rticle history:eceived 27 October 2012eceived in revised form 17 January 2013ccepted 22 January 2013vailable online 29 January 2013
In this study, an analytical procedure for the selective extraction and detection of 4-nitrophenol(4-NP) was investigated by using of molecularly imprinted polymer on the surface of magneticnanoparticles (MNPs). The magnetic nanoparticles were modified by tetraethyl orthosilicate (TEOS) and3-methacryloxypropyl trimethoxysilane (MPTS) before imprinting. The magnetic molecularly imprintedpolymer (MMIP) was polymerized at the surface of modified MNPs by using of methacrylic acid (MAA)as functional monomer, 4-NP as template and ethylene glycol dimethacrylate (EGDMA) as cross-linker.Experimental design by the Taguchi method was used for the optimization of synthesis procedure ofimprinted polymer. The resulting MMIP showed high adsorption capacity, proper selectivity and fastkinetic binding for the template molecule. It was characterized by Fourier transform infrared (FT-IR)analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods.The maximum adsorption capacity of MMIP was obtained as 57.8 mg g−1 and it took about 2 h to achieve
the equilibrium state. The adsorption curve of MMIP was also fitted with the Freundlich isotherm equa-tion. The assay exhibited a linear range of 25–1000 �g L−1 for 4-NP with the correlation coefficient (R2) of0.995. The method was also examined for the analysis of 4-NPs in seawater. For recovery evaluation, theseawater samples were spiked at two concentration levels of 50 and 100 �g L−1 of 4-NPs and the recoveryvalues were in the range of 79.3–99.8%. The relative standard deviations (RSD) for the recoveries wereless than 5.2%.
. Introduction
Molecularly imprinted polymers (MIPs) are artificial polymershich are formed in the presence of a target molecule that finally
s removed by the proper solvents; therefore, the obtained specificavities are complement to the target molecule in shape, size andunctional groups.
The use of MIPs has been developed in various fields such asxtraction [1–5], sensors [6,7], catalysis [8,9] and drug delivery10]. In recent years, the combination of MIP and other samplereparation techniques like solid phase extraction, solid-phaseicroextraction and matrix solid-phase dispersion has opened a
ew window for selective extraction and recognition of targetolecules from the complex matrices [11].The conventional method for the preparation of MIPs is bulk
olymerization [12,13], which is traditional and exhibit high selec-ivity. There are some defects for this polymerization method suchs: imperfect removal of template molecules, slow mass transfer
of template molecules from the polymer backbone, heterogeneousdistribution of the binding sites, poor site accessibility and smallbinding capacity in some cases. Therefore, surface polymerizationhas been suggested for the improving of accessibility to the tar-get molecules, more suitable mass transfer and complete removalof templates [14,15]. In this regard, the surface grafting MIPs havebeen developed on the different surfaces such as silica particles[14,16,17], titanium dioxide particles [18], anodic alumina oxidemembrane [19], and polymeric supports [20]. Recently, we syn-thesized molecularly imprinted nanocomposites on the surfaceof mesoporous silica with high imprinting effect and adsorptioncapacity for the selective extraction of 2,4-dinitrophenol in aqueoussamples [21].
Nowadays magnetic nanoparticles (MNPs) because of theirattractive properties have been used in the separation methods[22], catalysis [23], bioscience [24] and environmental remedi-ation [25]. The MNPs possess significant advantages including:small size, high surface-to-volume ratio, high magnetic suscepti-
bility and effective ability for binding. On the other hand, easy andefficient separation can be performed with an external magneticfield without any additional centrifugation or filtration procedures[26,27].
contact time may allow 4-NP to be associated more effectivelywith the monomer. Then, 200 mg of modified Fe3O4@SiO2 wasadded into the reaction mixture and the mixture was stirred for3 h. 5 mmol of EGDMA and 20 mg of AIBN were added into the
Table 1Parameters and their levels in the Taguchi method.
A. Mehdinia et al. / J. Chr
The MNPs can also be used as proper solid support substrateor imprinting polymers. For the first time, in 1998, Mosbach et al.28] synthesized MIP on the magnetic substrate by suspensionolymerization but the obtained magnetic imprinted polymer didot exhibit more recognition ability than non magnetic imprintedolymer against the target molecule. Thereafter, the researchersodified the surface of magnetic substrates with different mate-
ials to improve the recognition properties of magnetic MIPsMMIPs). Ethylene glycol [29], oleic acid [30,31] and trimethoxysi-ane with vinyl [26,32] or amino groups [33] were some of the
odifiers used for this purpose.4-Nitrophenol (4-NP) is widely used for the manufacture of
rugs, dyes, fungicides, insecticides and darkens leather [34].ccording to the U. S. Environmental Protection Agency (EPA), 4-P has been reported as Priority Pollutants. There are not anynown natural sources of 4-nitrophenol in the environment. Thenthropogenic sources of nitrophenols in air and soil are proba-ly industrial manufacturers and processors. The vehicular exhaust
s another main source of releasing nitrophenols to the envi-onment. In water, both photolysis and biodegradation woulde important fate processes. Effluents from the textile industry,aste waters from various industries such as iron and steel man-facturing, foundries, pharmaceutical manufacturing, processingnd electrical/electronic components production may also releaseoth 2-nitrophenol and 4-nitrophenol into the surface waters [34].ecause of the presence of nitrophenols at trace levels in the var-
ous matrices, especially water samples, the analytical methodsith effective sample preparation and extraction, and trace-leveletection are required [35].
In this work, we performed the combination of imprinting poly-ers and MNPs for selective and effective recognition of 4-NP from
queous samples. The MNPs were modified by vinyl groups andhen the modified surface was employed for grafting of copolymer-zed methacrylic acid (MAA) and ethylene glycol dimethacrylateEGDMA) which imprinted by 4-NP. The adsorption capacity andelectivity of the nanoparticles were also investigated and theirharacteristics were compared with non imprinted polymers (NIP).
. Experimental
.1. Chemicals
Iron (III) chloride hexahydrate (FeCl3·6H2O), iron (II) chlo-ide tetrahydrate (FeCl2·4H2O), ammonium hydroxide (NH4OH)or synthesis of Fe3O4 nanoparticles, tetraethyl orthosilicateTEOS) and 3-methacryloxypropyl trimethoxysilane (MPTS) werebtained from Merck (Darmstadt, Germany). For preparationf imprinted polymer, EGDMA and acetonitrile (HPLC grade)ere purchased from Sigma–Aldrich (Beijing, China) and Caledon
Ontario, Canada) companies, respectively. 4-NP, 2-nitrophenol2-NP), 2,4-dinitrophenol (2,4-DNP), phenol (Ph), MAA, and 2,2-zobisisobutyronitrile (AIBN) were also obtained from Merck.
.2. Instrumentation
The MMIP was characterized by scanning electron microscopyHitachi S-4160 SEM), transmission electron microscopy (PhilipsM30 TEM) and FT-IR (Bruker VERTEX 70 spectrometer). The higherformance liquid chromatography (HPLC) analyses were per-ormed with an Agilent 1100 series (Santa Clara, CA, USA) withV/Vis detector.
.3. Synthesis of Fe3O4@SiO2
For preparation of Fe3O4 nanoparticles, FeCl3·6H2O (34.6 mmol)nd FeCl2·4H2O (17.30 mmol) were dissolved in 160 mL double
gr. A 1283 (2013) 82– 88 83
distilled water while stirring under nitrogen gas atmosphere. Then20 mL of NH4OH (25%, v/v) was added dropwise to the solutionwhile increasing the temperature up to 80 ◦C and then, the reactionwas carried out for 30 min. The black Fe3O4 MNPs were separatedby an external permanent magnet.
The synthesized Fe3O4 nanoparticles (900 mg) were dispersedin 300 mL mixture of ethanol and double distilled water (4:1, v/v) byultrasonic vibration for 15 min. Subsequently, NH4OH (15 mL) andTEOS (2.1 mL) were continuously added into the reaction mixture.The reaction was stirred for 12 h at 40 ◦C and finally the productwas gathered by a magnet.
2.4. Surface modification of Fe3O4@SiO2
250 mg of Fe3O4@SiO2 nanoparticles was chemically modifiedby 5 mL of MPTS in 30 mL toluene solution under the protec-tion of nitrogen. The mixture was refluxed for 24 h at 120 ◦C. TheFe3O4@SiO2@MPTS was collected by an external magnetic field andthen washed with toluene and distilled water, respectively.
2.5. Experimental design for synthesis conditions
Experimental design was developed for planning of an exper-iment at various conditions. The Taguchi method provides theoptimal selection of parametric values with a systematic and effi-cient approach for conducting of experiments. This method appliedorthogonal arrays (OA) to investigate a large number of variableswith a small number of experiments. In order to analyze the results,it used a statistical measure of performance called signal-to-noise(S/N) ratio. Usually, three types of S/N ratio analysis are applica-ble: (1) lower is better, (2) nominal is the best, and (3) higheris better [36,37]. Therefore, the optimal condition was acquiredwith performing small number of experiments and significantlythe experiments time and costs were minimized.
In this work, we applied experimental design by the Taguchimethod for the optimization of MMIP synthesis conditions.Three experimental parameters including the amount of modifiedFe3O4@SiO2 (mg), the molar ratio of template to monomer (T:M)and the molar ratio of monomer to cross-linker (M:C) with threelevels were considered as the independent variables and their val-ues are summarized in Table 1. For full investigation of the impact ofvariables, 27 (33) experiments were needed. An L9 orthogonal array(OA) has carried out to design experiment with selected parametersand levels. The experimental layout of OA (L9) was also showed inTable 2. The optimum condition was obtained with three replicatesand determined by the signal to noise (S/N) ratio with approachof higher is better. The adsorption capacity was measured as theresponse of S/N ratio. For analyzing of the results Minitab 16 pro-gram was applied.
2.6. Preparation of 4-NP-MMIP
0.33 mmol 4-NP and 1 mmol MAA were dissolved in 50 mL ofacetonitrile and stirred for 12 h at room temperature [14,38]. This
esulted mixture and the solution was purged with nitrogen gasor 10 min while cooled in an ice bath and maintained under ultra-onic vibration. The polymerization was performed at 60 ◦C underitrogen gas for 24 h. Finally, the synthesized 4-NP-MMIPs wereeparated by an external magnetic field and eluted by a mixturef methanol/acetic acid (9:1, v/v) for removing the entrapped tem-lates. It was then washed with distilled water. For comparison,agnetic non-molecular imprinted polymers (MNIPs) were also
ynthesized simultaneously under the same procedure withoutemplate molecule. Fig. 1 exhibits the schematic preparation pro-edure of 4-NP-MMIP.
.7. Adsorption experiment
The adsorption capacity was measured in five times by adding0 mg of 4-NP-MMIPs or MNIPs in a 10 mL aqueous solution of 4-
P at concentrations ranged from 0.1 to 6 mM. The solution was
haken for 12 h at room temperature and then, MMIPs (or MNIPs)as separated by an external magnetic field and supernatant was
Fig. 1. Schematic representation of chemical modification of Fe3O4 (a), prea
gr. A 1283 (2013) 82– 88
analyzed by HPLC-UV. The adsorption capacity (Q) was calculatedfrom Eq. (1).
Q = (C0 − Ce) · V
m(1)
In Eq. (1), Q (mg g−1) is the adsorption capacity, C0 and Ce
(mg L−1) are the initial and equilibrium concentrations of 4-NPsolution, respectively. V (L) is the volume of the initial solution andm (g) is the mass of MMIP (or MNIP).
2.8. Selectivity experiments
The selectivity of MMIP for 4-NP and similar compounds (2-NP, 2,4-DNP, Ph) was determined at the Qmax concentration. Theselectivity coefficients were evaluated by Eqs. ((2)–(4)):
Kd = Qe
Ce(2)
=Kd(4NP)
Kd(SC)
(3)
˛r = ˛MIP
˛NIP(4)
where kd is the distribution coefficient, Qe and Ce are the adsorp-tion capacity and equilibrium concentrations of 4-NP and similarcompounds, respectively.
In Eq. (3) represents the selectivity factor and Kd(SC) is thedistribution coefficient of similar compounds. In Eq. (4) ˛r alsorepresents the relative selectivity factor which is depended on theselectivity factor of MIP and NIP.
A C18 column (250 mm × 4.6 mm i.d., 5 mm) from Agilentwas used as the analytical column. The mobile phase for
rrangement of MAA and 4-NP (b), and preparation of 4-NP-MMIPs (c).
A. Mehdinia et al. / J. Chromatogr. A 1283 (2013) 82– 88 85
r adso
c(ww1wi
2
Omnifaiff
psw0
3
3
NtStis
orc
Fig. 2. Main effects plot fo
hromatographic analysis consisted of acetonitrile, containing 1%v/v) acetic acid, as solvent A and Milli-Q water acidified to pH = 2.5ith acetic acid, as solvent B. The flow-rate of the mobile phaseas 1 mL min−1 and the gradient profile was 50–100% A from 0 to
0 min, and then isocratic elution for 2 min. The oven temperatureas set at 25 ◦C and all compounds were detected at 254 nm. The
njection volume was also 20 �L.
.10. Determination of 4-NP in real samples
The real aqueous samples were seawaters of Persian gulf andman sea. The samples were collected in glass bottles and wereaintained in darkness and cool place until analysis. For determi-
ation of 4-NP in the samples, 20 mg of MMIP powder was addednto 10 mL of aqueous samples. After stirring at room temperatureor 2.5 h, the MMIPs were separated by an external magnetic fieldnd then were eluted with 0.5 mL of acetonitrile solution contain-ng 10% acetic acid. This procedure resulted in a preconcentrationactor of 20. Finally the eluted solution was injected into the HPLCor analyzing of target analyte.
In addition, liquid–liquid extraction (LLE) was applied for com-arison with MMIP extraction. In this regard, a Persian gulf waterample was extracted by dichloromethane solvent after spikingith 100 �g L−1 of 4-NP. The extract evaporated and re-solved in
.5 mL of acetonitrile and then injected to HPLC.
. Results and discussion
.1. Determination of optimum conditions
In the preliminary studies, the adsorption capacity of MIP andIP were determined in some selected conditions and the adsorp-
ion capacity of MIP was higher than NIP in all the conditions.ince the major part of the analyte adsorb on the imprinting sites,hen the more adsorption capacity can be representative of moremprinting sites. Therefore, the adsorption capacity of MIP was con-idered as the target of optimization.
The optimization of parameters was investigated with anrthogonal design L9 (33). The obtained results of the signal to noiseatio were plotted in Fig. 2. As shown in this figure, the optimumonditions were 200 mg for the amount of modified surface, 0.33:1
rption capacity in MMIP.
(mmol:mmol) for the molar ratio of template to monomer and 1:5(mmol:mmol) for the molar ratio of monomer to cross-linker. Asshown in Fig. 2, the adsorption capacity decreased slightly for molarratio of monomer to cross-linker of 1:3 to 1:4 and then increasedlargely for 1:5 ratios. It can be described by this fact that for smallmolecules as template, high amount of cross-linker is necessary toproduce proper selective cavities into the polymer matrix. On theother hand, when the amounts of cross linker increase from 1:3to 1:4, non-selective binding sites could decrease and the createdselective cavities cannot compensate this reduction. Meanwhile,the created sites have not yet obtained rigid structure for imprint-ing of template. But, high amount of cross linker (1:5 ratio) providedhigh amount of selective cavities. Therefore, the maximum adsorp-tion capacity was observed in 1:5 state.
The MMIP was prepared in the optimal conditions obtained fromthe Taguchi method.
3.2. Preparation and characterization of MMIP
The preparation protocol of MMIP, as exhibited in Fig. 1, wasincluding following steps: (1) synthesis of Fe3O4 nanoparticles,(2) silica coating on Fe3O4, (3) surface modification by MPTS,(4) coating MIP film on the modified surface, and (5) removingtemplate. At first step, Fe3O4 MNPs were prepared by the copre-cipitation method. The silica shell on Fe3O4 was formed with TEOSby sol–gel process. The resulted silica shell provided hydrophilicsurface which prevented the oxidation of Fe3O4. Furthermore,surface silanol groups could offer many possibilities for modi-fication through covalent attachment of specific compounds onthe Fe3O4@SiO2 nanoparticles [26]. Finally, a thin MIP film wasformed onto the modified surface of Fe3O4@SiO2 under optimalconditions. Also, there is a competition between surface and bulkpolymerization. The competition could affect the homogeneity ofthe MIP coating. Meanwhile, the Fe3O4@SiO2 size distribution isanother parameter affecting the coating homogeneity. Therefore,the Taguchi method was used to optimize the amount of mod-ified magnetic surface and other parameters to result in better
MIP coating on the surface of modified magnetic nanoparticles.By this optimization, the homogeneity of MMIP was reasonable(16–30 nm) and the bulk polymerization effect has been mini-mized.
86 A. Mehdinia et al. / J. Chromato
stemtwafi3
FtsosMSma1oTo
F
Fig. 3. SEM and TEM images of MMIP.
The morphology and size of magnetic imprinting polymers weretudied by SEM and TEM and the results were shown in Fig. 3. Thehickness of silica layer coated on the surface of Fe3O4 nanoparticlesstimated by SEM was in the range of 75–100 nm. From the TEMicrograph it seems that the beads are not isolated but connected
o one another. The SEM micrograph also shows some agglomeratesith distribution of bead sizes. Furthermore, the spherical shape
nd core–shell structure of MMIP can be obviously observed in thisgure and the thickness of imprinted polymer layer was lower than0 nm.
Fig. 4(a)–(c) shows the infrared spectra of Fe3O4@SiO2,e3O4@SiO2@MPTS and 4-NP-MMIP, respectively. Fig. 4(a) showshe formation of silanol groups on the surface of Fe3O4. The IRpectra of MPTS-magnetic nanoparticles in Fig. 4(b) indicates peaksf carbonyl group at 1718.68 cm−1 and symmetry and asymmetrytretching bonds of methyl group at the range of 2800–3000 cm−1.eanwhile, the peak around 1100 cm−1 can be attributed to the
i–O–Si stretching vibration. The results expressed that chemicalodification on the surface of Fe3O4@SiO2 has been successfully
chieved by MPTS. In addition, the shift of carbonyl group peak from718 cm−1 to 1736 cm−1 (Fig. 4(c)) can express the participationf double bond of MPTS in the copolymerization with monomers.herefore, the resulted shift shows the elimination of conjugation
f carbonyl group with MPTS double bonds.
ig. 4. IR spectra of Fe3O4@SiO2 (a), Fe3O4@SiO2@MPTS (b), and 4-NP-MMIP(c).
gr. A 1283 (2013) 82– 88
3.3. Adsorption isotherms
The adsorption capacities of MMIP and MNIP were comparedat various concentrations of 4-NP in aqueous media. As shown inFig. 5(a), the synthesized MMIP had higher adsorption capacity thanMNIP for the template molecules. It can be seen that the adsorp-tion capacity increased with increasing of 4-NP concentration andthen it reached to an equilibrium state. The maximum adsorptioncapacities of 4-NP-MMIP and 4-NP-MNIP at 6 mM were 57.8 mg g−1
and 22.1 mg g−1, respectively. The RSD (n = 5) obtained was 3.31%for MMIP at the Qmax concentration for 4-NP. The retention mech-anism of 4-NP in the MIP in aqueous samples could be hydrogenbonding and non-covalent interaction between the template andmonomer.
The adsorption capacity of synthesized MIP was compared withthe other reported MIPs for 4-NP including bulk MIP [39] and mag-netic MIP [40]. The resulting magnetic MIP in this work showedhigher Qmax than the other works. Ersöz et al. [39] preparedtwo kinds of bulk MIP with MAA and methacrylamidoantipyrine(MAAP) as functional monomer for the removal of 4-NP. The Qmax
of 4-NP obtained for MAA-MIP and MAAP-MIP were 97 �mol g−1
(13.5 mg g−1) and 173 �mol g−1 (24.1 mg g−1), respectively whichwere lower than that obtained in the present work (57.8 mg g−1).In the other study [40], the Qmax of reported for magnetic MIP wasobtained as 4.5 mg g−1 which was less than that obtained in ourwork. The Freundlich isotherm was also used for the investiga-tion of heterogonous binding sites in the imprinted polymers. TheFreundlich isotherm can be expressed by Eqs. (5) and (6).
Q = ˛Cme (5)
log Q = log + m log Ce (6)
where Q, Ce, and m are the absorbed amount of 4-NP, equi-librium concentration, Freundlich constant and the heterogeneityfactor (with values from 0 to 1), respectively. Fig. 5(b) exhibited theadsorption isotherm of target molecules on the MMIP and MNIPfitted to the Freundlich isotherm.
Two another binding parameters, number of bindingsites (Nkmin−kmax ) and apparent average association constant(Kkmin−kmax ), were also calculated:
Nkmin−kmax = ˛(1 − m2)(k−mmin − k−m
max) (7)
Kkmin−kmax =(
m
m − 1
)(k1−m
min − k1−mmax
k−mmin − k−m
max
)
kmin = 1cmax
, kmax = 1cmin
(8)
The results of Freundlich parameters are listed in Table 3. Thedata also showed that Nkmin−kmax in MMIP was much higher thanMNIP. This means that the number of sites with adequate geom-etry and good accessibility to 4-NP were higher in MIP-coatedMNPs than in NIP-coated MNPs, demonstrating the imprinting phe-nomenon [29,41,42].
The Langmuir model was also investigated for fitting the exper-imental data and the R2 value obtained was less than Freundlichisotherm (R2 = 0.959 for MIP and R2 = 0.775 for NIP).
The adsorption kinetic of MMIP was also studied at differentinterval times. As seen in Fig. 6, the adsorption of 4-NP by MMIPwas fast in the first 120 min and then reached to the equilibriumafter 150 min.
3.4. Adsorption selectivity
The selectivity experiment was performed for 4-NP and threeanalogous compounds named as: 2-NP, 2,4-DNP and Ph. Fig. 7
A. Mehdinia et al. / J. Chromatogr. A 1283 (2013) 82– 88 87
Fig. 5. Adsorption isotherm of MMIP and MNIP for 4-NP (a) and the fitting plots with Freundlich isotherm model (b).
Table 3Freundlich fitting parameters for MMIP and MNIP.
Fig. 6. Adsorption time curve of 4-NP-MMIP at the Qmax concentration.
ompared the adsorption selectivities of MMIP and MNIP for 4-NPnd similar compounds. It was shown that the adsorption capac-ties of MMIP for the template molecule were about 1.57, 1.9 and
.82 times that for 2-NP, Ph and 2,4-DNP, respectively. However,NIP did not show any significant difference between adsorption
f 4-NP and similar compounds. The selectivity coefficient was also
ig. 7. Adsorption selectivity for 4-NP and analogous compounds at the Qmax
oncentration.
0.974 23.425 8.4760.965 10.140 7.561
exhibited in Table 4. Based on this table, the relative selectivityfactors were higher than one which indicated more selectivity ofMMIP for 4-NP than the other tested compounds.
3.5. Method validation and real sample analysis
The linearity and detection limit were investigated for the ana-lytical methodology of prepared sorbent. The results indicated goodlinearity in the range of 25–1000 �g L−1 (with selected six con-centrations and three replications) for 4-NP with the correlationcoefficient (R2) of 0.995. The obtained LOD was 7.24 �g L−1 forthe target molecule. For LOD estimation, the MIP was added to anaqueous solution without analyte and analyzed in three times. Thestandard deviations of blank signals were calculated and the LODwas obtained by division of three times of standard deviation ofblank into the slope of calibration curve.
On the other hand, the accuracy and repeatability of the methodwas evaluated by spiking aqueous samples with 4-NP at concen-tration levels of 50 and 100 �g L−1. The results for two kinds ofseawater samples extracted by synthesized MMIP and MNIP weresummarized in Table 5. The recovery obtained for MMIP was morethan that for MNIP. Fig. 8 also exhibited chromatograms of non-spiked Persian gulf water sample extracted by MMIP (a) and theseawater sample spiked with 100 �g L−1 extracted by LLE (b) andby MMIP (c). Based on the EPA, the criterion for 4-NP to protect salt-water aquatic life is 53 �g L−1 [43]. It means the proposed method
can be useful to detect 4-NP in seawaters according to the guidelinelevel of EPA.
Table 4The selectivity parameters of MMIP and MNIP (n = 3).
ig. 8. HPLC chromatograms of seawater sample of Persian gulf extracted by MMIPa), spiked sample with 100 �g L−1 of 4-NP extracted by LLE (b) and MMIP (c).
. Conclusions
A selective sorbent was synthesized by using of imprinting poly-ers for 4-NP as template. A new strategy was developed for MMIP
f 4-NP in aqueous samples by copolymerization of functional andross-linking monomers on the surface of vinyl modified silicaanoparticles in the presence of template molecule. Thin imprintedhells were generated over the support particles and the resultingmprinted particles could be readily collected with a magnet. Themprinted particles showed proper selectivity, fast kinetic bind-ng, suitable repeatability and the higher adsorption capacity than
agnetic non-imprinted polymers to 4-NP. The proposed analysisethod prepared the effective and convenient tools for monitoring
f 4-NPs in aqueous samples.
cknowledgment
We gratefully acknowledge the financial support of this worky the Iranian National Science Foundation with grant number of0000602.
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