Surface-Imprinted Magnetic Carboxylated Cellulose Nanocrystals for

Subscriber access provided by UB + Fachbibliothek Chemie | (FU-Bibliothekssystem)

Article

Surface-imprinted magnetic carboxylated cellulose nanocrystals for the highly selective extraction of six fluoroquinolones from egg samples Yan Fei Wang, Yang Guang Wang, Xiao Kun Ouyang, and Li Ye Yang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b12206 • Publication Date (Web): 22 Dec 2016 Downloaded from http://pubs.acs.org on December 24, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Surface-imprinted magnetic carboxylated cellulose nanocrystals for the highly selective extraction of six fluoroquinolones from egg samples Yan–Fei Wang, Yang–Guang Wang, Xiao–kun Ouyang*, Li–Ye Yang

School of Food and Pharmacy, Zhejiang Ocean University, Zhoushan 316022, P.R. China

*Corresponding author. Tel.: +86–580–2554781. Fax: +86–580–2554781. E–mail address: [email protected]

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 46

Abstract:

We herein describe a novel adsorbent based on molecularly imprinted polymers (MIPs)

on

the

surface

of

magnetic

carboxylated

cellulose

nanocrystals

(Fe3O4@CCNs@MIPs) for the separation and purification of six fluoroquinolones (FQs) from egg samples. The obtained Fe3O4@CCNs@MIPs not only exhibited a large surface area and specific recognition towards FQs, but were also easily gathered and separated from the egg samples using an external magnetic field. The morphologies and surface groups of the Fe3O4@CCNs@MIPs were assessed by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), X-ray diffraction (XRD), thermogravimetric analysis

(TGA),

Fourier

transform

infrared

spectroscopy

(FTIR),

and

Brunauer–Emmett–Teller (BET) surface area analysis. The Fe3O4@CCNs@MIPs exhibited high selectivity towards six structurally similar FQs. An enrichment approach was established for the measurement of six FQs from egg samples using Fe3O4@CCNs@MIPs coupled to high-performance liquid chromatography (HPLC). The recovery of spiked FQs ranged from 75.2 to 104.9% and limit of detection (LOD) was in the range of 3.6–18.4 ng g−1 for the six FQs. Therefore, the proposed method is a promising technique for the enrichment, separation, and determination of FQs from biomatrices.

Keywords: carboxylated cellulose nanocrystals, fluoroquinolones, molecularly imprinted polymers, high-performance liquid chromatography, biomatrices.


Page 3 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1. Introduction Molecularly imprinted polymers (MIPs) have received impressive attention due to their excellent affinity and selectivity towards molecular targets.1-2 To date, MIPs have been widely applied in catalysis,3 chemical/biosensor devices,4 solid-phase extraction,5 controlled drug release,6 and chromatographic separation.7 However, issues such as poor site accessibility, high diffusion barriers, and low affinity binding have limited the application of MIPs.8 To address these issues, many studies have been carried out using surface imprinting techniques to investigate viable nano-sized support materials.9 Surface molecular imprinting refers to a polymerization reaction on the surface of a solid substrate, such that the imprinted sites are scattered on the surface of the imprinted polymers or the outer surface of solid substrates.10 Support materials are therefore critical for such techniques. To date, the majority of studies have employed various materials as carriers, including carbon nanotubes (CNTs),11 graphene,12 and chitosan,13 among others,14 due to their strong mechanical strength, chemical stabilities , and high specific surface areas. However, some materials suffer from limitations, such as high preparation costs and difficult modification processes, which limit the applications of MIPs.15 Therefore, new support materials must be developed to increase the utility of MIPs. We selected carboxylated cellulose nanocrystals (CCNs) as novel support materials for MIPs to broaden the range of available substrate materials. As cellulose is the most generous renewable green material in nature, cellulose nanocrystals (CNCs) have received increasing attention as important materials in biomaterial science



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 46

because they are lightweight and exhibit a high mechanical strength, biocompatibility, high aspect ratio, reactive surface –OH groups, broad chemical modifying capacity, large specific surface area, high availability, and biodegradability.16 Thus, CNCs have great potential for application as adsorbents,17 templates for photocatalysts,18 electrode materials for capacitive deionization,19 and stabilizing agents.20 Notably, their high specific surface area makes them promising candidates for such applications, as they exhibit strong affinities and high adsorption capacities towards various chemicals. The addition of carboxyl groups to the surface of CNCs through carboxylation yields CCNs, which have a more extensive range of applications than CNCs. CCNs are inexpensive, nontoxic, and pose no serious environmental concerns; all of which provide an impetus for their use as support materials for MIPs. The separation of MIPs from solutions or samples is also an issue that prevents the wide-scale application of MIPs. Typical separation methods include centrifugation and filtration; however, these methods are time-consuming and inefficient. Magnetic materials, e.g. Fe3O4, have therefore been employed in MIPs to aid separation.21 We herein propose that the combination of these three promising concepts (i.e., MIPs, CCNs, and Fe3O4) in a single system will lead to the generation of novel Fe3O4@CCNs@MIP materials exhibiting multifunctional performances, high selectivities, high adsorption capacities for molecular targets, and facile separation by an external magnetic field. Thus, we

herein

present the preparation of Fe3O4@CCNs@MIPs

via

copolymerization using ciprofloxacin (CIP) as the template, carboxylated cellulose


Page 5 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


nanocrystals (CCNs) as carriers, 2-methylacrylic acid (MAA) as the functional monomer, divinylbenzene (DVB) as the cross-linker, and Fe3O4 as the magnetic material. The prepared Fe3O4@CCNs@MIPs was applied in the separation of fluoroquinolones (FQs) (Figure 1) from egg samples. FQs are one of the most important categories of antibiotics, and as such, they are widely used in veterinary and human medicine. However, the leftover of FQs in foods of animal origin are potentially harmful to human health. Therefore, it is essential to develop an efficient method for their removal from foods. OH

O

OH

F

O

O

OH O

F

N

N

N

NH

F

O

O

N

N O

N F

N

NH

ciprofloxacin

ofloxacin

lomefloxacin

(CIP)

(OFX)

(LOM)

OH

OH O F

O N

F N

N O

OH O

O

O

N O

NH

NH2

NH

O N

NH2

F

O N

N F

NH

NH S O O

gatifloxacin

moxifloxacin

sparfloxacin

sulfamethoxazole

(GAT)

(MFX)

(SPX)

(SMZ)

Figure 1 The molecular structures of ciprofloxacin (CIP), ofloxacin (OFX), lomefloxacin (LOM), gatifloxacin (GAT), moxifloxacin (MFX), sparfloxacin (SPX), and sulfamethoxazole (SMZ).



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

2. Experimental 2.1 Materials Analytical standards (purity >99%, used as received) of ciprofloxacin (CIP), ofloxacin (OFX), lomefloxacin (LOM), gatifloxacin (GAT), moxifloxacin (MFX), sparfloxacin (SPX), and sulfamethoxazole (SMZ), as well as analytical grade microcrystalline cellulose (MCC), ammonium persulfate (APS), citric acid, ferrous chloride tetrahydrate (FeCl2•4H2O), ferric chloride hexahydrate (FeCl3•6H2O), methacrylic acid (MAA), benzoyl peroxide (BPO), divinylbenzene (DVB), and polyethylene glycol (PEG) were purchased from Aladdin Chemical Reagent Co., Ltd. (Shanghai, China). Analytical grade ethanol, acetonitrile (ACN), acetic acid, ammonia solution (NH3•H2O), methanol, and dimethyl sulfoxide (DMSO) were supplied by Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). HPLC grade acetonitrile was purchased from Oceanpak Alexative Chemical, Ltd. (Gothenburg, Sweden). The egg samples were delivered from a local market in Zhoushan (Zhejiang, China). Deionized water was obtained by a Milli-Q® water purification system (Millipore, Molsheim, France).

2.2 Preparation of CCNs CCNs were prepared according to a literature method22 with minor modifications. MCC (6 g) was introduced into an aqueous APS solution (200 mL, 2 M), and subjected to ultrasonication for 4 h at 60 °C with stirring. The suspension was transferred into centrifuge tubes (50 mL) and centrifuged for 10 min at 9000 rpm,


Page 6 of 46

Page 7 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


then washed three times with deionized water. The obtained colloid was dissolved in an aqueous citric acid solution (200 mL, 1 M), and the resulting mixture was further stirred and subjected to ultrasonication for 2 h at 60 °C. The final product was acquired by centrifugation of the suspension for 10 min at 9000 rpm and was washed three times with deionized water (30 mL). Finally, to obtain an aqueous solution of the desired CCNs, deionized water (50 mL) was added, and the solution was subjected to dialysis to give a solution pH of 7.

2.3 Preparation of the Fe3O4@CCNs The Fe3O4@CCNs were prepared according to a literature procedure23 with minor modifications. An aqueous solution of CCNs (100 mL, 0.2 wt.%) was added to a three-necked flask and purged for 30 min with N2, followed by the addition of FeCl3•6H2O (0.8 g), FeCl2•4H2O (0.3 g), and NH3•H2O (~5 mL) to adjust the solution pH to 9–10. Thereafter, the mixture was stirred for 1 h while maintaining the temperature at 70 °C and then cooled to room temperature (25 °C). The resulting Fe3O4@CCNs were washed three times using deionized water and ethanol and separated using an external magnetic field.

2.4 Preparation of the Fe3O4@CCNs@MIPs The template molecules (CIP, 1.0 mmol) and functional monomers (MAA, 4.0 mmol) were mixed in DMSO (20 mL) under magnetic stirring for 2 h to allow them to self-assemble via hydrogen bonding interactions. Fe3O4@CCNs (0.5 g) and PEG



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(0.4 g) were then added to a solution of DMSO/H2O (9:1 v/v, 100 mL), and mixed with DVB cross-linker (1 mL), BPO initiator (0.5 g) and the pre-assembled solution under ultrasonication for 10 min. The mixture was continuously stirred under an atmosphere of N2 for 12 h while maintaining its temperature at 60 °C. The obtained nanoparticles were washed three times with ethanol and deionized water and were separated using a magnetic field. Subsequently, the CIP template was removed using a mixture of 10% acetic acid/methanol (v/v) solution under ultrasonication for 10 min until CIP cannot be detected by HPLC. Finally, the Fe3O4@CCNs@NIPs were rewashed with deionized water and freeze-dried. The magnetic carboxylated cellulose nanocrystal molecularly non-imprinted polymers (Fe3O4@CCNs@NIPs) were also synthesized using the above procedures, but without the addition of template molecules.

2.5 Characterization The morphologies of the synthesized nanoparticles were determined by TEM (Lorentz, JEM-2100, JOEL, Japan), and the surface groups were investigated by using FTIR (Tensor II, Bruker, Germany). Phase identification was detected by XRD (D8 ADVANCE with DAVINCI, Bruker, Germany). Magnetic properties were characterized using physical property measurement system (PPMS, Model-9, Quantum Design, USA), while surface elemental analysis was carried out via multifunctional XPS (AXIS ULTRA DLD, Shimadzu, Japan). In addition, thermogravimetric analysis was measured using TGA (Pyris Diamond TG/DTA,


Page 8 of 46

Page 9 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Perkin-Elmer, USA). Nitrogen adsorption isotherms were obtained using a Micromeritics ASAP 2020M apparatus (ASAP 2020M, Micromeritics, USA). Furthermore, the determination of the surface area was carried out using the Brunauer-Emmett-Teller (BET) method.24 Finally, the Barrett-Joyner-Halenda (BJH) model with desorption branches of the isotherms was employed to calculate the pore volumes and pore size distributions.

2.6 Chromatographic conditions For HPLC, an Agilent 1200 system (Agilent, Santa Clara, CA, USA) equipped with an autosampler (G1329A), degasser unit (G1322A), quaternary pump (G1311A), column thermostat (G1316A), and diode-array detector (G1315D) was used. A ZORBAX SB-C18 (5 µm particle size, 150 mm × 4.6 µm) analytical column was used for separation. The mobile phase (flow rate = 1 mL min−1) was composed of acetonitrile (A) and 0.05% triethylamine phosphate aqueous solution (pH 2.50) (B). The linear gradient elution program was: 0–2 min, 86.0% (B); 2–5 min, 86.0–74.0% (B); 5–8 min, 74.0% (B). 292 nm and 20 µL were the detection wavelength and the injection volume, respectively, and the column temperature was kept at 25 °C.

2.7 Binding characteristics The adsorption isotherm was investigated by mixing either Fe3O4@CCNs@MIPs or Fe3O4@CCNs@NIPs (10 mg) in CIP solutions (2 mL) of various concentrations (50–850 mg L−1) and incubating the samples at 25 °C for 2 h at 150 rpm. The



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 46

Fe3O4@CCNs@MIPs were then collected under an external magnetic field, and the quantity of FQ (i.e., CIP) in the supernatant was determined by HPLC. The equilibrium adsorption capacity (Q) was described by the following equation: Q =

(C 0 − C e )V m

,

(1)

where C0 and Ce (mg L−1) are concentrations of the FQs in the initial and adsorption equilibrium solutions, respectively, V (mL) is the volume of the used solution, and m (mg) is the weight of Fe3O4@CCNs@MIPs or Fe3O4@CCNs@NIPs. The Freundlich and Langmuir isotherms were used to estimate the adsorption mechanism of the Fe3O4@CCNs@MIPs. The Freundlich equation25 is expressed as follows: lg Q = lg K F +

lg C e , n

(2)

where Q (mg g−1) is the quantity of adsorbed CIP at equilibrium, Ce (mg L−1) is the CIP concentration that remains in solution at equilibrium, and KF and n are Freundlich constants associated with the adsorption interaction, and adsorption intensity, respectively. In addition, the Langmuir equation26 can be expressed as follows: Ce C 1 = e + Q Qm Qm K L

,

(3)

where Qm (mg g−1) is the saturated adsorption capacity, and KL (L mg−1) is the Langmuir binding constant. Sulfamethoxazole (SMZ) was chosen as the reference compound to assess the selectivity of Fe3O4@CCNs@MIPs towards the target compounds. SMZ is a widely


Page 11 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


used sulfonamide, and its residues exist in the environment alongside FQs. A working solution of FQs and SMZ was all prepared at an initial concentration of 20 µg mL−1. Fe3O4@CCNs@MIPs (10 mg) was incubated with the working solution (10 mL) for 2 h at 25 °C and 150 rpm. Then the mixture was separated under an external magnetic field, and the compounds present in the supernatant were determined by HPLC. The selectivity coefficient (SC) and imprinting factor (IF)27 were used to estimate the selective adsorption of the Fe3O4@CCNs@MIPs, which are defined in equations 4 and 5, respectively: IF =

Q MIP , Q NIP

(4)

where QMIP and QNIP (mg g−1) are the adsorption quantity of the target molecule or competitor molecule by the Fe3O4@CCNs@MIPs and Fe3O4@CCNs@NIPs, respectively. SC =

QFQs QSMZ

,

(5)

where QFQs and QSMZ (mg g−1) are the quantities of FQs and SMZ, respectively, adsorbed by the Fe3O4@CCNs@MIPs. The stability and recyclability of the Fe3O4@CCNs@MIPs were investigated at an initial

FQ

concentration

of

1 µg mL−1.

Following

adsorption,

the

Fe3O4@CCNs@MIPs were eluted by 10% acetic acid/methanol (v/v) solution, and the recovered Fe3O4@CCNs@MIPs were re-used as the adsorbent for recycling experiments. All extraction experiments were performed in triplicate.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 46

2.8 Optimization of the extraction procedure An egg sample was transferred to a beaker and homogenized by stirring. Then homogenized egg sample (1.0 g) was then soaked in an Erlenmeyer flask (50 mL capacity) containing the working standard solution (200 µL, 5 µg mL−1) and deionized water (9 mL) were introduced. The resulting mixture was shaken by hand for 1 min. Subsequently, the Fe3O4@CCNs@MIPs (5–25 mg) were added, and were machine-shaken

at

25 °C

for

5–100 min,

prior

to

separation

of

the

Fe3O4@CCNs@MIPs from the egg samples using a magnetic field. The recovered adsorbent was sequentially washed with deionized water (2 mL) and aqueous acetonitrile (2 mL, 10%) three times, followed by addition of 2 mL of acetic acid/methanol with different ratios (1-30%; v/v), solution was then added, and the mixture was subjected to ultrasonication to elute the template for 1 min. The elution process was carried out for three times. The eluted solutions were then combined and concentrated to dryness under a stream of N2. Finally, the dried sample was re-dissolved in the mobile phase (1 mL), vortexed for 30 s, and prior to HPLC analysis filtered through a 0.22-µm polytetrafluoroethylene membrane.

2.9 Application of Fe3O4@CCNs@MIPs for the extraction of six FQs from egg samples A homogenized egg sample (1.0 g) was spiked with the six FQs at three different concentration levels (i.e., 0.5 µg g−1, 1 µg g−1, and 2 µg g−1). Deionized water (9 mL)


Page 13 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


and the Fe3O4@CCNs@MIPs (10 mg) were then added, and adsorption-desorption experiments

were

conducted

under

optimized

conditions

(10 mg

Fe3O4@CCNs@MIPs, 80 min adsorption time, 10% acetic acid/methanol (v/v) for elution). Finally, the FQ contents were determined by HPLC.

3. Results and Discussion We herein report the preparation of CNCs containing abundant hydroxyl and a few carboxyl groups by the oxidation of MCC by APS. Following further modification with citric acid, the as-prepared CCN surfaces were rich in carboxyl groups, which could interact with hydroxyl groups distributed on the Fe3O4 surface to produce Fe3O4@CCNs. This association renders the materials magnetic, and thereby allows their facile collection from solution via a magnetic separation process. For the imprinted polymerization of the functional monomer MAA, CIP was used as the template, with PEG as the dispersant, DVB as the crosslinking agent, BPO as the initiator, and Fe3O4@CCNs as the carrier. Elution of the CIP template afforded the desired Fe3O4@CCNs@MIPs. The FQs have a 4-oxo-1,4-dihydroquinoline skeleton, which contains a pyridine ring with a carboxyl group, a fluorine atom and a piperazinyl group, located at positions 3, 6, and 7, respectively. Therefore, the template CIP has proton-accepting and hydrogen-bonding functional groups that can interact with the polar carboxyl group in the MAA monomers that are bonded on the Fe3O4@CCNs@MIPs. Adsorbents based on CNCs (or its carboxylated derivatives; i.e. CCNs) can remove a wide variety of pollutants from wastewater.22, 28 Their effectiveness as adsorbents arises from properties such as their high specific surface area, good mechanical strength, biodegradability, large number of active sites, and high functionality. In



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

addition, CCNs have a large number of carboxylic groups (more than CNCs), which are effective in the binding and adsorption processes. However, the post-adsorption separation of CCNs requires high speed centrifugation, which limits their applications in many fields. Thus, CCNs were combined with magnetic Fe3O4 to facilitate their post-adsorption separation. Furthermore, the combination of Fe3O4@CCNs with MIPs also enhances the selective behavior of the materials. The large surface area of CCNs provides enough sites for the molecular imprinting process, and the active carboxyl and hydroxyl groups of CCNs surface enable the molecular imprinting of the CCNs surface. Thus, the functional monomer can bind to the CCNs surface form hydrogen bonds with the target FQ molecules to enhance their uptake.

3.1 TEM analysis The morphologies of the CCNs, Fe3O4@CCNs, and Fe3O4@CCNs@MIPs were studied using TEM (Figure 2). As shown in Figure 2a, the large spherical particles formed from the aggregation of CCNs.29 Indeed, these aggregations were formed by a self-assembly process from short cellulose rods and their fragments via interfacial hydrogen bonds

30

In addition, as shown in Figure 2b, during the synthesis of Fe3O4

@CCNs, the presence of Fe3O4 improves the dispersion of the CCNs; correspondingly, less aggregation of the CCNs particles occurs. The Fe3O4 nanoparticles are immobilized on the surface of CCNs by interactions between the carboxyl groups of CCNs and the hydroxyl groups of Fe3O4. The Fe3O4 permeates the spherical CCNs such that Fe3O4@CCNs are well dispersed and do not aggregate into larger spherical particles.23 On the other hand, Figures 2c and 2d indicate that there are some


Page 14 of 46

Page 15 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


aggregations in the formed Fe3O4@CCNs@MIPs. However, the presence of MIPs affected the final formed structure, because the MIP layers were present around Fe3O4@CCNs as a surface-imprinted layer with thickness ranging from 20 to 30 nm.

(a)

(b)

(c)

(d)

Figure 2 TEM images of (a) the CCNs, (b) the Fe3O4@CCNs, (c) and (d) the Fe3O4@CCNs@MIPs in different magnification.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 46

3.2 XRD analysis Figure

3a

shows the

XRD patterns of the CCNs,

Fe3O4@CCNs, and

Fe3O4@CCNs@MIPs, which were examined to elucidate the crystal phase of the functionalized nanoparticles further. The characteristic peaks of the CCNs shown at -

2θ = 14.92°, 16.45°, and 22.73° in Figure 3a(1) correspond to the (101), (101), and (002) planes, respectively, and represent the typical diffraction pattern of cellulose I crystals.31 For the Fe3O4@CCNs (Figure 3a(2)) and Fe3O4@CCNs@MIPs (Figure 3a(3)), the six peaks at 2θ = 30.28°, 35.41°, 43.40°, 53.80°, 57.22°, and 62.79 ° correspond to the (220), (311), (400), (422), (511), and (440) reflections, respectively, which were consistent with the JCPDS card (19-629) for Fe3O4.32 The XRD patterns, therefore, confirmed that the modification did not change the Fe3O4 phase. Furthermore, the characteristic peaks of CCNs were not observed in plots (2) and (3) of Figure 3a because the CCNs sheets cannot pile up each other to form crystalline structures after being embedded with the magnetic nanoparticles.33


0

422 440 511 220 311 400 -400 (a) 20 40 60 2 Theta (° )

Weight (%)

Transmittance (%)

(2) Fe3O4@CCNs

400

90

80

(1) Fe3O4

-10.03%

(2) Fe3O4@CCNs

- 24.92%

60

100

- 21.42% (c)

(3) Fe3O4@CCNs@MIPs

30 0 60

200

1.2

(1) CCNs 1160 1059 (2) Fe3O4@CCNs 1620 2900 0.6 3440 1730 1430 1110 (b) (3) Fe3O4@CCNs@MIPs580 4000 3000 2000 1000 Wavenumbers (cm-1) 200 adsorption desorption

Pore Volume (cm3 g-1)

(1) CCNs (3) Fe3O4@CCNs@MIPs

800

Magnetization (emu g-1)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Intensity (a.u.)

Page 17 of 46

400 600 800 1000 Temperature (°C) (1)Fe3O4@CCNs

(d) 0 0.0

0.3 0.6 0.9 Relative Pressure (P/P0)

30 0 -30

(2)Fe3O4@CCNs@MIPs (e)

-60 -30000 -15000

0

after 10s (f)

15000 30000

Magnetic field (Oe)

Figure 3 (a) XRD patterns of (1) the CCNs, (2) the Fe3O4@CCNs, and (3), the Fe3O4@CCNs@MIPs. (b) FTIR spectra of (1) the CCNs, (2) the Fe3O4@CCNs, and (3) the Fe3O4@CCNs@MIPs. (c) TGA curves of (1) Fe3O4, (2) the Fe3O4@CCNs, and (3) the Fe3O4@CCNs@MIPs. (d) N2 adsorption-desorption isotherms for the Fe3O4@CCNs@MIPs. (e) VSM magnetization curves for (1) the Fe3O4@CCNs, and (2) the Fe3O4@CCNs@MIPs. (f) Photographic images showing the magnetic separation of Fe3O4@CCNs@MIPs.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 46

3.3 FTIR analysis The FTIR spectra of the CCNs, Fe3O4@CCNs, and Fe3O4@CCNs@MIPs are shown in Figure 3b. The values of 1430 and 2900 cm−1 for the observed peaks were attributed to the bending and stretching vibrations of saturated C–H and –CH2– bonds, respectively, while those at 1160, 1059, and 1110 cm−1 belong to C–C bond vibrations, the vibration of the C–O bond of the cellulose alcohol, and an ether C–O bond of the nanocrystalline cellulose, respectively. In addition, the broad peak at 3440 cm−1 corresponds to an O–H stretching vibration, while that at 1620 cm−1 corresponds to the stretching vibration of the carboxyl groups.34 Thus, the FTIR spectra suggest that the CCNs were successfully synthesized and modified with carboxyl groups. As shown in the Fe3O4@CCNs spectrum (Figure 3b (2)), the new peak present at 580 cm−1 was assigned to the Fe–O stretching vibrations, which indicated that the magnetic nanoparticles and CCNs had been successfully synthesized. Moreover, the band at 3440 cm−1 weakened because of the strong hydrogen bonding between Fe3O4 and the CCNs. Following MIP modification to yield the Fe3O4@CCNs@MIPs, a new band appeared at 1730 cm−1 (Figure 3b (3)), which was attributed to the C=O stretching vibrations of MAA. These results confirm that the imprinted layer was successfully grafted on the Fe3O4@CCNs.

3.4 TGA analysis Figure

3c

shows

the

TGA

curves

of

the

Fe3O4,

Fe3O4@CCNs,

and

Fe3O4@CCNs@MIPs samples. The first degradation step was caused by evaporation


Page 19 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


of residual water and moisture from the samples, with weight losses 5.8, 4.0, and 2.5% at

ambient

temperature

(0-150°C)

for

the

Fe3O4,

Fe3O4@CCNs,

and

Fe3O4@CCNs@MIPs samples respectively. The second degradation step was due to the thermal decomposition of the polymer and was observed at higher temperatures in the case of the Fe3O4@CCNs (Figure 3c (2)) and Fe3O4@CCNs@MIPs (Figure 3c (3)). Previous reports indicate that CCNs exhibit a characteristic degradation peak between 280 and 320 °C that correlates with the degradation of the pyranose rings along the CCNs backbone. During this process, the CCNs lose approximately 78–80% of their weight,30 and as such, the content of CCNs in the Fe3O4@CCNs composite could be estimated at 9.7–10%. In contrast, the degradation mechanism for MIPs consists of two stages. Firstly, conversion into poly(methacrylic anhydride) (PMAN) takes place at 220 °C, and secondly, decomposition occurs at elevated temperatures (i.e., ≤400 °C) as a consequence of PMAN fragmentation.35-36 In the case of the Fe3O4@CCNs@MIPs, the added MIPs layer causes an increase in weight loss from 10.03 to 24.92%, in addition to generating a third degradation step at 400–560 ºC. In this third step, a further weight loss of 21.42% was recorded, corresponding to the decomposition of the MIPs layer,37 which clearly demonstrates the success of the imprinting process.

3.5 BET analysis The N2 adsorption-desorption isotherms of the Fe3O4@CCNs@MIPs are shown in Figure 3d. Similar IV-type curves with an H3-hysteresis loop were observed,



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 46

indicating mesoporous structures containing a number of silt holes.38 Three regions can be observed in the adsorption isotherms as follows: (1) When P/P0 lies between 0 and 0.6, a monolayer-multilayer adsorption behavior exists; (2) when P/P0 increases from 0.6 to 0.9, capillary condensation is observed; and (3) when P/P0 lies between 0.9 and 1.0, surface multilayer adsorption occurs. In addition, the surface area of the Fe3O4@CCNs@MIPs was calculated to be 76.5 m2 g−1 using the multipoint BET (Brunauer-Emmett-Teller) method39 (P/P0 = 0.06–0.19), which was a larger value than that of the Fe3O4@CCNs (i.e., 67.3 m2 g–1). This finding suggests that the imprinting process

was

beneficial

for

the

adsorption

of

target

molecules

on

the

Fe3O4@CCNs@MIPs. Finally, average pore diameter and the total pore volume of the Fe3O4@CCNs@MIPs, calculated by the BJH method, were determined to be 13.4 nm and 0.242 cm3 g−1, respectively.40

3.6 VSM analysis Figure 3e shows the magnetic hysteresis loops for the Fe3O4@CCNs and Fe3O4@CCNs@MIPs at 25 °C. Both materials exhibited superparamagnetic behavior, with

the

saturated

magnetization

values

for

the

Fe3O4@CCNs

and

Fe3O4@CCNs@MIPs being 57.09 and 33.46 emu g−1, respectively. The imprinted layer on the Fe3O4@CCNs surface influenced the magnetic response of Fe3O4, causing a decrease in the magnetization value of the Fe3O4@CCNs@MIPs. However, the Fe3O4@CCNs@MIPs still exhibited magnetic separation under an external magnetic field, as shown in Figure 3f.


Page 21 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3.7 XPS analysis To further explore the surface chemical composition of the Fe3O4@CCNs@MIPs, XPS survey spectra, and high-resolution scans were obtained for the main elements. As shown in Figure 4a, the survey spectrum revealed three dominant peaks at 281.4, 530.3, and 710.6 eV, which assigned to C 1s, O 1s, and Fe 2p, respectively. The XPS spectra for Fe 2p, Fe 3p, C 1s, and O 1s of the Fe3O4@CCNs@MIPs are shown in Figures 4b–e, respectively, while Figure 4f shows the XPS spectra of the O 1s peak of the Fe3O4@CCNs. In the Fe 2p spectra (Figure 4b), peaks ascribing to Fe 2p3/2 and Fe 2p1/2 were observed with binding energies of 708.1 and 721.8 eV. The absence of a satellite peak at ~714 eV, which is typical of the Fe2O3 phase, suggested the formation of Fe3O4 in the Fe3O4@[email protected] Furthermore, the proportion of Fe2+ to Fe3+ in the magnetic nanoparticles was approximately 1:2, which confirms the presence of Fe3O4 (see Figure 4c).41 The XPS spectra of C1s (Figure 4d) showed four component peaks with binding energies of 281.8, 283.7, 285.4, and 287.2 eV, which corresponded to the C–C, C–O, O–C–O, and O–C=O bonds, respectively.42 In addition, following imprinting, the major O 1s peaks at 530.1, 531.1, and 533.2 eV, corresponding to the C=O, C–O, and COO– bonds, shifted to lower binding energies of 527.0, 527.5, and 530.1 eV, respectively (see Figures 4e and 4f).43 Moreover, the intensity of the COO– bond increased, clearly suggesting the successful grafting of MAA on the Fe3O4@CCNs.



4000

Fe2p O1s

40000

Fe2p 1/2

CPS

CPS

60000

C1s

Fe2p 3/2

3000

20000 0 (a) Survey 1000 800

600

400

200

2000 (b) Fe 2p 740 730

0

720 B.E.(eV)

B.E.(eV)

400

1800

CPS

200

1200

3000

60

55 50 B.E.(eV)

45

0

40

C-O 527.5 C=O 527.0

2000 1000

3000 1500

(e) O1s 538 536 534 532 530 528 526 524 522

0

C-C 281.8

(d) C1s 292

4500

COO530.1

CPS

65

700

O-C-O O-C=O 285.4 287.2

600

100 (c) Fe 3p

710

C-O 283.7

CPS

3+ Fe 2+ Fe

300

CPS

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 46

288 284 B.E.(eV) C-O 531.1

280

276

C=O 530.1

COO533.2 (f) O1s 538 536 534 532 530 528 526 524 522

B.E.(eV)

B.E.(eV)

Figure 4 XPS survey spectra of (a) the Fe3O4@CCNs@MIPs. XPS spectra of (b) the Fe 2p, (c) the Fe 3p, (d) the C 1s, and (e) the O 1s of Fe3O4@CCNs@MIPs. (f) High-resolution scan of the O 1s spectra of the Fe3O4@CCNs.

3.8 Adsorption isotherm curves Further studies were performed to test the adsorption isotherms of CIP on the Fe3O4@CCNs@MIPs. Figure 5a presents the adsorption isotherm curves of the Fe3O4@CCNs@MIPs and Fe3O4@CCNs@NIPs with different initial concentrations of CIP. As expected, the equilibrium adsorption capacity of CIP on the Fe3O4@CCNs@MIPs

increased

with

increasing

initial


CIP

concentration.

Page 23 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Interestingly, the quantity of CIP bonded to the Fe3O4@CCNs@MIPs was 50 mg g−1, which is greater than that found for the Fe3O4@CCNs@NIPs (i.e., 29 mg g−1), and is expected to be due to the imprinting effect. The equilibrium adsorption data were explored based on Langmuir and Freundlich isothermal adsorption models. The linear regression equation for the Langmuir isotherm was Ce/Q = 0.0134Ce + 3.6909 (R2 = 0.8417), and as such, the results of Qm and KL were 68.97 mg g−1 and 0.0036 L mg−1, respectively. Similarly, the linear equation for the Freundlich isotherm was log Q = 0.2217 log Ce − 0.1599 (R2 = 0.9851), and the values of n and KF were 4.51 and 1.45, respectively. These results confirm that the adsorption of CIP on the Fe3O4@CCNs@MIPs was better fitted to the Freundlich isotherm model.


-1

Adsorption Capacity (mg g

(a) 40

20 Fe3O4@CCNs@MIPs Fe3O4@CCNs@NIPs

0 0

200

120 OFX

FQs recovery (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 46

)


400 600-1 Concentration (mg L ) CIP

LOM

GAT

800 SPX

MFX

(b) 90 60 30 0 1

2

3 4 5 6 Adsorption-desorption cycle

7

8

Figure 5 (a) Adsorption isotherm curves for CIP on Fe3O4@CCNs@MIPs and Fe3O4@CCNs@NIPs. (b) Reusability of the Fe3O4@CCNs@MIPs, using the following conditions: Initial FQ concentration = 1 µg mL−1 standard working solution; adsorption dose = 10 mg; adsorption time = 80 min; eluent solution = 10% acetic acid/methanol (v/v).

3.9 Adsorption selectivity The adsorption capacities of the Fe3O4@CCNs@MIPs and Fe3O4@CCNs@NIPs towards the various FQs were investigated using SMZ as the reference compound to


Page 25 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


illustrate the molecular recognition ability of the Fe3O4@CCNs@MIPs. The results are summarized in Table 1. Table 1 Selectivity of the Fe3O4@CCNs@MIPs and Fe3O4@CCNs@NIPs towards different FQs Analyte

QMIPa (mg g-1)

QNIPa (mg g-1)

IFb

SCc

OFX

7.24

2.59

2.80

3.80

CIP

11.31

4.75

2.38

6.64

LOM

6.77

3.31

2.05

3.75

GAT

7.88

4.59

1.72

4.08

SPX

5.59

1.98

2.83

2.77

MFX

8.08

4.94

1.63

3.91

SMZ

1.30

1.36

0.96

—

a

QMIP and QNIP (mg g-1) represent the binding quantity of FQs or reference compound on the Fe3O4@CCNs@MIPs and Fe3O4@CCNs@NIPs; b

IF = QMIP/QNIP, cSC = QFQs/QSMZ.

The IF (QMIP/QNIP) and SC (QFQs/QSMZ) values were used to indicate the selectivities of the Fe3O4@CCNs@MIPs and Fe3O4@CCNs@NIPs towards the various FQs and to the competitor molecule (SMZ). The IF values for OFX, CIP, LOM, GAT, SPX, and MFX were calculated as 2.80, 2.38, 2.05, 1.72, 2.83, and 1.63, respectively. The Fe3O4@CCNs@MIPs revealed a much greater adsorption capacity towards FQs than the Fe3O4@CCNs@NIPs, suggesting that the Fe3O4@CCNs@MIPs have a relatively high affinity towards FQs. Moreover, the SC values of OFX, CIP, LOM, GAT, SPX, and MFX were 3.80, 6.64, 3.75, 4.08, 2.77, and 3.91, respectively, which indicated



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

that the Fe3O4@CCNs@MIPs exhibited excellent selectivity towards the FQs compared to the reference compound, SMZ. Notably, the adsorption capacity of SMZ on the Fe3O4@CCNs@MIPs was similar to that on the Fe3O4@CCNs@NIPs, which illustrated that there was no specificity between SMZ and the Fe3O4@CCNs@MIPs. Table 1 also shows that the SC values were high, confirming the high specificity and adsorption selectivity of the Fe3O4@CCNs@MIPs to FQs owing to specific imprinting sites. Thus, the Fe3O4@CCNs@MIPs could be applied in the separation of different FQs.

3.10 Regeneration As adsorbent reusability is a key factor for sustainability, we conducted adsorption-desorption experiments with eight different FQs using the same Fe3O4@CCNs@MIPs over eight cycles to evaluate the reusability of the material. As shown in Figure 5b, a gradual decline to 53.5–65.1% in the recovery of FQs by Fe3O4@CCNs@MIPs was observed after eight cycles. This decrease was perhaps due to the irreversible and partial loss of the active sites following FQ binding, or through active site destruction upon washing, thus leading to their unavailability for further adsorption cycles.44 Overall, the Fe3O4@CCNs@MIPs exhibited good repeatability and reproducibility, which appeared unaffected by either ultrasonic or acidic treatments.


Page 26 of 46

Page 27 of 46

3.11 Adsorption Studies 3.11.1 Effect of adsorbent quantity Dose response studies were carried out using different quantities of adsorbent (5–25 mg) for the recovery of FQs from egg substrates (1.0 g). The results shown in Figure 6a indicate that 10 mg of Fe3O4@CCNs@MIPs was optimal for the extraction and recovery of FQs from this medium. In addition, an increase in the quantity of adsorbent beyond 10 mg decreased the recovery of the various FQs, likely because of incomplete desorption.45

120

60

30

OFX CIP LOM GAT

SPX (a) MFX 0 5 10 15 20 25 Amount of Fe3O4@CCN@MIPs (mg)

FQ recovery (%)

90 FQ recovery (%)

90 60 30 0

(b) 0

20 40 60 80 Adsorption Time (min)

OFX CIP LOM GAT SPX MFX 100

90 FQ recovery (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


60

OFX CIP LOM 30 GAT SPX (c) MFX 0 1% 5% 10% 15% 20% 25% 30% Acetic acid/Methanol (v/v)

Figure 6 Optimization of extraction conditions (n = 3). (a) Effect of Fe3O4@CCNs@MIPs quantity on FQ recovery. (b) Effect of adsorption time on FQ recovery. (c) Effect of elution solvent on FQ recovery.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

3.11.2 Effect of adsorption equilibrium time The shaking times were varied between 5 and 100 min to investigate the effect of adsorption time. Figure 6b indicated that the recovery of the various FQs increased with the increasing adsorption time over the initial 80 min, after which time a plateau was reached. Therefore, we selected 80 min as the optimal adsorption time. Furthermore, the adsorption time of our materials was equivalent to that of the surface-imprinted polymer Fe3O4@MIPs,46 and was more rapid than that of the imprinted polymer nanoparticle MCN@MIPs47 employing mesoporous carbon nanoparticles (MCNs) as the carrier.

3.11.3 Effect of elution solvent To determine the optimal elution solvent, a variety of acetic acid/methanol mixtures (i.e., 1–30%, v/v) were evaluated, and the results are shown in Figure 6c. Poor recoveries were observed when low (1%) or high ratios (30%) of acetic acid/methanol (v/v) were employed, while satisfactory recoveries were obtained using 10% acetic acid/methanol (v/v). In addition, a range of ultrasonication times was studied for the elution process. However, the results have shown that the desorption/ultrasonication time had no significant influence on FQ recovery; therefore, an optimal ultrasonication time of 1 min was established.


Page 28 of 46

Page 29 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3.11.4 Application of Fe3O4@CCNs@MIPs for the separation of six FQs from egg samples As the sample matrix can greatly affect the signal of the target and enhance the background noise, two calibration curves were built for each analyte to qualitatively assess the matrix effects, i.e., one in a solvent, and the other in a blank egg extract. Calibration curves were obtained using peak area against analyte concentration values. Thus, by comparing the slopes of the two calibration curves (Table 2), a matrix effect (ME)48 in the range of 0.85 to 1.04 was observed, indicating that the application of Fe3O4@CCNs@MIPs for the extraction of FQs from egg samples yielded satisfactory results. Table 2 Linear equations and matrix effects

Analyte

a

Linear equation

R2

b

Linear equation of R2

c

ME

matrix effect OFX

y = 36.356x - 3.9494

0.9994

y = 31.070x - 1.5981

0.9968

0.85

CIP

y = 31.731x - 8.9654

0.9929

y = 29.449x - 7.9994

0.9943

0.93

LOM

y = 40.396x - 3.9079

0.9998

y = 34.974x - 3.2646

0.9982

0.87

GAT

y = 43.636x - 2.8880

0.9998

y = 38.398x + 3.9301

0.9903

0.88

SPX

y = 43.539x - 2.6496

0.9999

y = 45.281x - 3.9371

0.9969

1.04

MFX

y = 54.950x - 3.1681

0.9998

y = 47.790x + 2.616

0.9951

0.87

a,b

linear range = 0.25-10 µg mL-1.

c

ME = matrix effect, i.e., the ratio of the calibration curve slopes from the blank egg extract and the solvent.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

To

assess

the

applicability

of

the

Page 30 of 46

Fe3O4@CCNs@MIPs

for

the

adsorption/desorption of FQs, limit of quantitation (LOQ), the linearity, limit of detection (LOD), accuracy, and precision of the system were examined. The accuracy was assessed by the analysis of egg samples spiked with the six FQs at levels of 0.5, 1, and 2 µg g−1. As Table 3 shows the recovery values ranged from 75.2 to 104.9%, indicating that the proposed method exhibited acceptable recoveries and accuracies. The intraday precision was investigated based on RSD% values using six replicates on the same day, while the interday precision was determined by taking measurements during five different days over a two-week period. The RSD% values of the intra- and interday experiments were acceptable, ranging from 1.5 to 10.9% (Table 3). In addition, the LOD (S/N = 3) and LOQ (S/N = 10) defined the ratio of signal-to-noise (S/N) and ranged from 3.6 to 18.4 ng g−1 and from 12.0 to 61.4 ng g−1, respectively (Table 3). Table 3 Recovery of the six FQs in spiked egg samples Average recoverya,% (RSD,%)

LOD

LOQ

2 µg g-1

(ng g-1)

(ng g-1)

Fluoroquinolones 0.5 µg g-1b

1.0 µg g-1

OFX

89.8(6.5c,8.9d) 81.5(4.8,7.7)

75.3(3.6,8.7)

17.8

59.2

CIP

81.1(3.2,7.6)

77.0(5.9,8.4)

81.2(6.6,7.9)

18.4

61.4

LOM

79.8(2.6,10.0)

76.8(7.8,8.3)

75.9(3.5,7.3)

8.9

29.7

GAT

79.8(4.5,10.1)

80.5(1.5,8.6)

75.3(5.9,8.0)

5.3

17.7

SPX

87.0(8.4,10.1)

75.2(4.2,9.9)

76.6(5.7,10.3)

4.6

15.3

MFX

99.6(7.9,7.2)

104.9(2.7,4.3) 95.4(7.4,10.9)

3.6

12.0


Page 31 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


a

Measured in 1 day (n = 6 replicates).

b

Spiked level.

c

Intraday, n = 6 replicates in 1 d.

d

Interday, n = 6 replicates in 5 d over 2 w.

Through comparison of the FQs adsorption capacities of previously reported MIPs, we could conclude that the Fe3O4@CCNs@MIPs exhibited the higher value of adsorption capacity (i.e., 50 mg g−1) compared to only MIPs (i.e., 43 mg g−1) that employ the same monomer and template.49 In addition, the Fe3O4@CCNs@MIPs also exhibited an improved adsorption compared to MCNTs@MIPs (i.e., 48 mg g−1)50 based on carbon nanotubes (CNTs) as magnetic (M) support materials, MIPs prepared by surface-initiated chain transfer polymerization (32 mg g−1),46 and MIPs prepared with biological fluids for solid phase extraction (30 mg g−1).51 These comparisons indicate that CCNs are promising carriers and that they provide a large surface area for imprinted sites.

Table 4 Comparison of the Fe3O4@CCNs@MIPs absorbent with other MIPs materials. Adsorbent

Adsorption capacity(mg g-1)

Adsorption time (min)

Ref.

MIPs

32

60

46

nanoMCN@MIPs

41

120

47

MCNTs@MIPs

48

40

50

MIPs

30

–

51

Fe3O4@CCNs@MIPs

50

80

This work

MCNTs = magnetic carbon nanotubes.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

MCNs = mesoporous carbon nanoparticles.

The adsorption time of our materials was equivalent to that of the surface-imprinted polymer Fe3O4@MIPs,46 and was faster than that of imprinted polymer nanoparticle MCN@MIPs47 that employed mesoporous carbon nanoparticles (MCNs) as a carrier.

Table 5 shows a comparison between this method and previously reported FQ extraction methods. The results indicated that this method has a comparable or better recovery than previously reported methods,52-55 and has lower or comparable values of LOD and LOQ compared with protein precipitation–HPLC,28 pressurized liquid extraction–HPLC–FL22 and MIPs–SPE–HPLC–DAD. 56


Page 32 of 46

Page 33 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 5 Extraction and determination of FQs with different methods. Extraction method

Analysis Method

Analytes

Pressurized liquid extraction

HPLC–FL

CIP, SARA, ENROa

Protein precipitatio n

HPLC

PAZ, CIP, LEVOa

MCNTs@ MIPc

b

Linear range

HPLC–DAD

17–24

30–41

µg g-1

ng g-1

ng g-1

0.10–20 µg mL-1

0.1

–

µg mL-1

6

15

-1

16 fluoroquin olones

Online SPEe

LC–MS/MS

SPE

LC–MS/MS

MFX

HPLC–FL

CIP, DANO, ENRO, LEVO, NOR, SARAa

HPLC–DAD

CIP, ENRO, NOR, MARa

HPLC–DAD

CIP, OFX, GAT, LOM, SPX, MFX

–

MIPs–SPE

MIPs–SPE

Fe3O4@CC Ns@MIPs

a

0.095–3 µg mL-1

Ref .

66–89

22

85.2–99. 3

28

52

ng mL

ng mL

0.01–4.23

0.04–12.93 ng mL-1

65.0–12 3.0

53

1.0

92.0–10 5.9

54

62–102

55

41.8–-96 .4

56

75.2–10 4.9

this wor k

-1

ng mL-1

0.001–2.5 µg mL-1

Recover y(%)

79.1–85. 3

GAT µg mL

f

LOQ

0.05–1

0.80–450 d

LOD

–

-1

ng mL-1

0.001–0.012 ng mL-1

0.012–0.14 ng mL-1

0.039–1.26 µg mL-1

18

39

ng mL-1

ng mL-1

0.25–10

3.6–18.4

12.0–61.4

µg mL-1

ng g-1

ng g-1

PAZ = pazufloxacin, LEVO = levofloxacin, SARA = sarafloxacin, ENRO =



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

enrofloxacin, DANO = danofloxacin, NOR = norfloxacin, MARBO = marbofloxacin. b

FL = fluorescence detector.

c

MCNTs = magnetic carbon nanotubes.

d

DAD = diode array detector.

e

SPE = solid phase extraction.

f

MS = mass spectrometry.

The corresponding HPLC chromatograms are shown in Figure 7, with Figure 7a indicating that the resolution between each peak was greater than 1.5. Furthermore, the peak response was low for the spiked egg samples that lacked pre-enrichment by Fe3O4@CCNs@MIPs (Figure 7b). However, following pre-treatment of the blank egg samples with Fe3O4@CCNs@MIPs, the number of impurities was reduced, and no signals corresponding to the FQs were observed (Figure 7c). Finally, the signals corresponding to the various FQs in the spiked egg samples treated with Fe3O4@CCNs@MIPs could be clearly observed (Figure 7d). These results indicate that the Fe3O4@CCNs@MIPs are applicable in the enrichment and separation of FQs from complex biomatrices.


Page 34 of 46

Page 35 of 46

GAT SPX

MFX

LOM OFX

(a)

mAU

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


CIP

(b) (c) (d)

1

2

3

4

5

6

7

t (min)

Figure 7 HPLC chromatograms of (a) A standard mixed solution of the six FQs (i.e., OFX, CIP, LOM, GAT, SPX, MFX); (b) Egg samples spiked with the six FQs without Fe3O4@CCNs@MIP pre-enrichment; (c) Blank egg samples following Fe3O4@CCNs@MIP

extraction;

and

(d)

Spiked

egg

samples

following

Fe3O4@CCNs@MIP extraction. All FQs were spiked at a concentration of 2 µg g−1.

4. Conclusions In summary, a novel molecularly surface-imprinted polymer based on Fe3O4@CCNs (CCNs = carboxylated cellulose nanocrystals) was successfully prepared. Owing to their high specific surface area, high availability, and low-cost modification, CCNs are among the most promising materials for molecularly imprinted polymer (MIP) supports. Thus, the prepared Fe3O4@CCNs@MIPs showed excellent selectivity, a large adsorption capacity (50 mg g−1), and suitable saturation



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 36 of 46

magnetization. Our novel material was then employed for selective extraction, purification, and HPLC-based determination of six different fluoroquinolones (FQs), namely ciprofloxacin, ofloxacin, lomefloxacin, gatifloxacin, moxifloxacin, and sparfloxacin,

from

egg

samples.

We

propose

that

magnetic

molecularly

surface-imprinted polymers are a suitable alternative for the extraction, purification, and separation of various compounds from complex matrices.

Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

Funding Sources The authors are grateful for the support of National Natural Science Foundation of China (21476212) and the Foundation of Science and Technology Department of Zhejiang Province (2017C33126).

Notes The authors declare that there are no conflicts of interest.


Page 37 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


REFERENCES 1.

Zhang, L.; Chen, L., Fluorescence Probe Based on Hybrid Mesoporous

Silica/Quantum Dot/Molecularly Imprinted Polymer for Detection of Tetracycline. ACS Appl. Mat. Interfaces 2016, 8, 16248-16256. 2.

He, Y. H.; Huang, Y. Y.; Jin, Y. L.; Liu, X. J.; Liu, G. Q.; Zhao, R., Well-Defined

Nanostructured

Surface-Imprinted

Polymers for

Highly Selective Magnetic

Separation of Fluoroquinolones in Human Urine. ACS Appl. Mat. Interfaces 2014, 6, 9634-9642. 3.

Abbate, V.; Bassindale, A. R.; Brandstadt, K. F.; Taylor, P. G., Biomimetic

catalysis at silicon centre using molecularly imprinted polymers. J. Catal. 2011, 284, 68-76. 4.

Silva H D; Pacheco J; Silva, J.; Viswanathan, S.; Delerue-Matos, C., Molecularly

imprinted sensor for voltammetric detection of norfloxacin. Sensor. Actuat. B Chem. 2015, 219, 301-307. 5.

Sun, X.; Wang, J.; Li, Y.; Yang, J.; Jin, J.; Shah, S. M.; Chen, J., Novel dummy

molecularly imprinted polymers for matrix solid-phase dispersion extraction of eight fluoroquinolones from fish samples. J. Chromatogr. A 2014, 1359, 1-7. 6.

Parisi, O. I.; Morelli, C.; Puoci, F.; Saturnino, C.; Caruso, A.; Sisci, D.; Trombino,

G. E.; Picci, N.; Sinicropi, M. S., Magnetic molecularly imprinted polymers (MMIPs) for carbazole derivative release in targeted cancer therapy. Acta Palaeontol. Pol. 2014, 2, 599-604.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

7.

Ansell, R. J.; Kuah, J. K. L.; Wang, D.; Jackson, C. E.; Bartle, K. D.; Clifford, A.

A., Imprinted polymers for chiral resolution of (+/-)-ephedrine, 4: Packed column supercritical fluid chromatography using molecularly imprinted chiral stationary phases. J. Chromatogr. A 2012, 1264, 117-23. 8.

Hui, L.; Xin, H.; Zhang, Y.; Shi, S.; Jiang, X.; Chen, X., High-capacity magnetic

hollow porous molecularly imprinted polymers for specific extraction of protocatechuic acid. J. Chromatogr. A 2015, 1404, 21-27. 9.

Barahona, F.; Díazálvarez, M.; Turiel, E., Molecularly imprinted polymer-coated

hollow fiber membrane for the microextraction of triazines directly from environmental waters. J. Chromatogr. A 2016, 1442, 12-18. 10. Nie, J.; Wang, Y. G.; Gao, X. F.; OuYang, X. K.; Yang, L. Y.; Yu, D.; Wu, W. J.; Xu, H. P., Pharmacokinetic study of ofloxacin enantiomers in Pagrosomus major by chiral HPLC. Biomed. Chromatogr. 2016, 30, 426-431. 11. Zhang, Z.; Zhang, H.; Hu, Y.; Yang, X.; Yao, S., Novel surface molecularly imprinted material modified multi-walled carbon nanotubes as solid-phase extraction sorbent for selective extraction gallium ion from fly ash. Talanta 2010, 82, 304-11. 12. Yan, L.; Yin, Y. L.; Lv, P. P.; Zhang, Z. H.; Wang, J.; Long, F., Synthesis and Application of Novel 3D Magnetic Chlorogenic Acid Imprinted Polymers Based on a Graphene-Carbon Nanotube Composite. J. Agric. Food Chem. 2016, 64, 3091-3100. 13. Fan, L.; Luo, C.; Zhen, L.; Lu, F.; Qiu, H., Removal of Ag + from water environment using a novel magnetic thiourea-chitosan imprinted Ag +. J. Hazard. Mater. 2011, 194, 193-201.


Page 38 of 46

Page 39 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


14. Lin, Z.; Xia, Z.; Zheng, J.; Zheng, D.; Zhang, L.; Yang, H.; Chen, G., Synthesis of uniformly sized molecularly imprinted polymer-coated silica nanoparticles for selective recognition and enrichment of lysozyme. J. Mater. Chem 2012, 22, 17914-17922. 15. Li, Y.; Liu, J.; Liu, M.; Yu, F.; Zhang, L.; Tang, H.; Ye, B. C.; Lai, L., Fabrication of ultra-sensitive and selective dopamine electrochemical sensor based on molecularly imprinted polymer modified graphene@carbon nanotube foam. Electrochem. Commun. 2016, 64, 42-45. 16. Hasani, M.; Cranston, E. D.; Westman, G.; Gray, D. G., Correction: Cationic surface functionalization of cellulose nanocrystals. Soft Matter 2015, 11, 7440-7440. 17. Sim, J. H.; Dong, S.; Röemhild , K.; Kaya, A.; Sohn, D.; Tanaka, K.; Roman, M.; Heinze, T.; Esker, A. R., 2-Hydroxypropyltrimethylammonium xylan adsorption onto rod-like cellulose nanocrystal. J. Colloid Interface Sci 2015, 440, 119-125. 18. Chen, X.; Kuo, D. H.; Lu, D., N-doped mesoporous TiO 2 nanoparticles synthesized by using biological renewable nanocrystalline cellulose as template for the degradation of pollutants under visible and sun light. Chem. Eng. J. 2016, 295, 192-200. 19. Liu, Y.; Pan, L.; Xu, X.; Lu, T.; Sun, Z.; Chua, D. H. C., Carbon nanorods derived from natural based nanocrystalline cellulose for highly efficient capacitive deionization. J. Mater. Chem. A 2014, 2, 20966-20972. 20. Lokanathan, A. R.; Uddin, K. M.; Rojas, O. J.; Laine, J., Cellulose nanocrystal-mediated synthesis of silver nanoparticles: role of sulfate groups in



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

nucleation phenomena. ACS.Biomac 2014, 15, 373-9. 21. Lin, Z. Z.; Zhang, H. Y.; Li, L.; Huang, Z. Y., Application of magnetic molecularly imprinted polymers in the detection of malachite green in fish samples. React. Funct. Polym. 2016, 98, 24-30. 22. Batmaz, R.; Mohammed, N.; Zaman, M.; Minhas, G.; Berry, R. M.; Tam, K. C., Cellulose nanocrystals as promising adsorbents for the removal of cationic dyes. Cellulose 2014, 21, 1655-1665. 23. Kai, L.; Nasrallah, J.; Chen, L.; Huang, L.; Ni, Y., Preparation of CNC-dispersed Fe3O4 nanoparticles and their application in conductive paper. Carbohydr. Polym. 2015, 126, 175-178. 24. Song, J.; Xu, T.; Gordin, M. L.; Zhu, P.; Lv, D.; Jiang, Y. B.; Chen, Y.; Duan, Y.; Wang, D., Nitrogen-Doped Mesoporous Carbon Promoted Chemical Adsorption of Sulfur and Fabrication of High-Areal-Capacity Sulfur Cathode with Exceptional Cycling Stability for Lithium-Sulfur Batteries. Adv. Funct. Mater. 2014, 24, 1243-1250. 25. Appel, J., Freundlich's adsorption isotherm. Surf. Sci. 1973, 39, 237-244. 26. Olsen, S. R.; Watanabe, F. S., A Method to Determine a Phosphorus Adsorption Maximum of Soils as Measured by the Langmuir Isotherm1. Soil Sci. Soc. Am. J. 1957, 21, 144-149. 27. Liu, S. M.; Yang, R.; Liu, Y.; Yan, X.; Zheng, H., An effective method for the synthesis of yolk-shell magnetic mesoporous carbon-surface molecularly imprinted microspheres. J. Mater. Chem. A 2016.


Page 40 of 46

Page 41 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


28. He, X.; Male, K. B.; Nesterenko, P. N.; Brabazon, D.; Paull, B.; Luong, J. H. T., Adsorption and desorption of methylene blue on porous carbon monoliths and nanocrystalline cellulose. ACS Appl. Mat. Interfaces 2013, 5, 8796-8804. 29. Lu, P.; Hsieh, Y. L., Preparation and properties of cellulose nanocrystals: Rods, spheres, and network. Carbohydr. Polym. 2010, 82, 329-336. 30. Hu, Y.; Tang, L.; Lu, Q.; Wang, S.; Chen, X.; Huang, B., Preparation of cellulose nanocrystals and carboxylated cellulose nanocrystals from borer powder of bamboo. Cellulose 2014, 21, 1611-1618. 31. Huang, H.; Wang, X.; Ge, H.; Xu, M., Multifunctional Magnetic Cellulose Surface-Imprinted Microspheres for Highly Selective Adsorption of Artesunate. Acs Sustain. Chem. Eng. 2016, 4. 32. Mao,

X.;

Sun,

H.;

He,

X.;

Chen,

L.;

Zhang,

Y.,

Well-defined

sulfamethazine-imprinted magnetic nanoparticles via surface-initiated atom transfer radical polymerization for highly selective enrichment of sulfonamides in food samples. Anal. Methods 2015, 7, 4708-4716. 33. Pan, S. D.; Shen, H. Y.; Zhou, L. X.; Chen, X. H.; Zhao, Y. G.; Cai, M. Q.; Jin, M. C., Controlled synthesis of pentachlorophenol-imprinted polymers on the surface of magnetic graphene oxide for highly selective adsorption. J. Mater. Chem. A 2014, 2, 15345-15356. 34. Zhu, W.; Ma, W.; Li, C.; Pan, J.; Dai, X., Well-designed multihollow magnetic imprinted microspheres based on cellulose nanocrystals (CNCs) stabilized Pickering double emulsion polymerization for selective adsorption of bifenthrin. Chem. Eng. J.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

2015, 276, 249-260. 35. Schild, H. G., Thermal degradation of poly(methacrylic acid): Further studies applying TGA/FTIR. J.Polym. Sci.Pol.Chem. 1993, 31, 2403-2405. 36. Ho, B. C.; Lee, Y. D.; Chin, W. K., Thermal degradation of polymethacrylic acid. J.Polym. Sci.Pol.Chem. 2003, 30, 2389-2397. 37. Huang, W.; Kong, Y.; Yang, W.; Ni, X.; Wang, N.; Lu, Y.; Xu, W., Preparation and characterization of novel thermosensitive magnetic molecularly imprinted polymers for selective recognition of norfloxacin. J. Polym. Res. 2016, 23, 1-11. 38. Zhao, D.; Gao, X.; Wu, C.; Xie, R.; Feng, S.; Chen, C., Facile preparation of amino functionalized graphene oxide decorated with Fe3O4 nanoparticles for the adsorption of Cr(VI). Appl. Surf. Sci. 2016, 384, 1-9. 39. Brunauer, S.; Emmett, P. H.; Teller, E., Adsorption of Gases in Multimolecular Layers. J.am.chem.soc 1938, 60, 309-319. 40. Barrett, E. P.; Joyner, L. G.; Halenda, P. P., The Determination of Pore Volume and Area Distributions in Porous Substances. I. Computations from Nitrogen Isotherms. J.Manage.Eng 2014, 24, 207-216. 41. Mullet, M.; Guillemin, Y.; Ruby, C., Oxidation and deprotonation of synthetic Fe{sup II}-Fe{sup III} (oxy)hydroxycarbonate Green Rust: An X-ray photoelectron study. J. Solid State Chem. 2008, 181, 81-89. 42. Jiang, L. H.; Liu, Y. G.; Zeng, G. M.; Xiao, F. Y.; Hu, X. J.; Hu, X.; Wang, H.; Li, T. T.; Zhou, L.; Tan, X. F., Removal of 17β-estradiol by few-layered graphene oxide nanosheets from aqueous solutions: External influence and adsorption mechanism.


Page 42 of 46

Page 43 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Chem. Eng. J. 2016, 284, 93-102. 43. Anirudhan, T. S.; Jalajamony, S.; Sreekumari, S. S., Adsorption of heavy metal ions from aqueous solutions by amine and carboxylate functionalised bentonites. Appl. Clay Sci. 2012, 65-66, 67-71. 44. Venkateswarlu, S.; Yoon, M., Core-Shell Ferromagnetic Nanorod Based on Amine Polymer Composite (Fe3O4@DAPF) for Fast Removal of Pb(II) from Aqueous Solutions. ACS Appl. Mat. Interfaces 2015, 7, 25362-25372. 45. Safdarian, M.; Ramezani, Z.; Ghadiri, A. A., Facile synthesis of magnetic molecularly imprinted polymer: Perphenazine template and its application in urine and plasma analysis. J. Chromatogr. A 2016, 1455, 28-36. 46. He, Y.; Huang, Y.; Jin, Y.; Liu, X.; Liu, G.; Zhao, R., Well-defined nanostructured surface-imprinted

polymers

for

highly

selective

magnetic

separation

of

fluoroquinolones in human urine. ACS Appl. Mat. Interfaces 2014, 6, 9634-9642. 47. Feng, T.; Sun, D.; Gao, J.; Qian, Z.; Wang, X.; Fei, T.; Xie, Q.; Chen, J., Preparation of molecularly imprinted polymer nanoparticles for selective removal of fluoroquinolone antibiotics in aqueous solution. J. Hazard. Mater. 2013, 244-245, 750-757. 48. Marchi, I.; Viette, V.; Badoud, F.; Fathi, M.; Saugy, M.; Rudaz, S.; Veuthey, J. L., Characterization and classification of matrix effects in biological samples analyses. J. Chromatogr. A 2010, 1217, 4071-8. 49. Chen, L.; Zhang, X.; Yang, X.; Du, X.; Xin, S.; Lei, S.; Hui, W.; Qi, Z.; Yu, A.; Zhang, H., Determination of fluoroquinolone antibiotics in environmental water



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

samples based on magnetic molecularly imprinted polymer extraction followed by liquid chromatography-tandem mass spectrometry. Anal. Chim. Acta 2010, 662, 31-38. 50. Xiao, D.; Dramou, P.; Xiong, N.; He, H.; Yuan, D.; Dai, H.; Li, H.; He, X.; Peng, J.; Li, N., Preparation of molecularly imprinted polymers on the surface of magnetic carbon nanotubes with a pseudo template for rapid simultaneous extraction of four fluoroquinolones in egg samples. Analyst 2013, 138, 3287-3296. 51. Dramou, P.; Zuo, P.; He, H.; Pham-Huy, L. A.; Zou, W.; Xiao, D.; Pham-Huy, C., Development of novel amphiphilic magnetic molecularly imprinted polymers compatible with biological fluids for solid phase extraction and physicochemical behavior study. J. Chromatogr. A 2013, 1317, 110-120. 52. Xiao, D.; Dramou, P.; Xiong, N.; He, H.; Li, H.; Yuan, D.; Dai, H., Development of novel molecularly imprinted magnetic solid-phase extraction materials based on magnetic carbon nanotubes and their application for the determination of gatifloxacin in serum samples coupled with high performance liquid chromatography. J. Chromatogr. A 2013, 1274, 44-53. 53. Kantiani, L.; Farré, M.; Barceló, D., Rapid residue analysis of fluoroquinolones in raw bovine milk by online solid phase extraction followed by liquid chromatography coupled to tandem mass spectrometry. J. Chromatogr. A 2011, 1218, 9019-9027. 54. Yaroshenko, I. S.; Khaimenov, A. Y.; V., G. E. A.; Sidorova, A. A., A chromatographic-mass spectrometric method for the determination of moxifloxacin in


Page 44 of 46

Page 45 of 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


blood plasma for pharmacokinetic studies. J. Anal. Chem. 2015, 70, 860-868. 55. Rodríguez, E.; Navarrovilloslada, F.; Benitopeña, E.; Marazuela, M. D.; Morenobondi, M. C., Multiresidue Determination of Ultratrace Levels of Fluoroquinolone Antimicrobials in Drinking and Aquaculture Water Samples by Automated Online Molecularly Imprinted Solid Phase Extraction and Liquid Chromatography. Anal. Chem. 2011, 83, 2046-2055. 56. Oliveira, H. L. D.; Anacleto, S. D. S.; Silva, A. T. M. D.; Pereira, A. C.; Borges, W. D. S.; Figueiredo, E. C.; Borges, K. B., Molecularly imprinted pipette-tip solid phase extraction for selective determination of fluoroquinolones in human urine using HPLC-DAD. J. Chromatogr. B 2016, 1033-1034, 27-39.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

254x190mm (96 x 96 DPI)


Page 46 of 46

Surface-Imprinted Magnetic Carboxylated Cellulose Nanocrystals for

Recommend Documents