Anal. Methods Environ. Chem. J. 4 (2) (2021) 5-24  
Research Article, Issue 2  
Analytical Methods in Environmental Chemistry Journal  
Journal home page: www.amecj.com/ir  
AMECJ  
Reusable and sustainable graphene oxide/metal–organic  
framework-74/Fe O /polytyramine nanocomposite  
3
4
for simultaneous trace level quantification of five  
fluoroquinolones in egg samples by high performance liquid  
chromatography  
a
a,*  
b
a
a
Fatemeh Pourbahman , Mohsen Zeeb , Amirhossein Monzavi , Zahra Khodadadi and Seyed Saied Homami  
a
Department of Applied Chemistry, Faculty of Science, South Tehran Branch, Islamic Azad University, Tehran, Iran  
Department of Polymer and Textile Engineering, South Tehran Branch, Islamic Azad University, Tehran, Iran  
b
A R T I C L E I N F O :  
Received 2 Mar 2021  
A B S T R A C T  
nanohybrid material termed graphene oxide/metal-organic  
framework-74/Fe O /polytyramine (GO/MOF-74/Fe O /PTy) was  
A
3
4
3
4
Revised form 5 May 2021  
Accepted 27 May 2021  
Available online 28 Jun 2021  
fabricated and applied in magnetic dispersive micro-solid phase  
extraction (MD-µ-SPE) coupled with high performance liquid  
chromatography (HPLC) for simultaneous determination of  
fluoroquinolones compounds including, ofloxacin, ciprofloxacin,  
lomefloxacin, enrofloxacin and sperfloxacin in egg samples. The  
GO/MOF-74/Fe O /PTy nanocomposite was fabricated through  
------------------------  
Keywords:  
Magnetic dispersive micro-solid phase  
extraction,  
Metal–organic framework,  
Graphene oxide,  
Polytyramine,  
3
4
an in situ synthesis of MOF-74 in the presence of magnetic GO  
and followed with an oxidative polymerization of tyramine using  
horsedish peroxide (HRP) enzyme. The modifier agents improved  
the merits of the nanoporous sorbent. Extraction protocols based  
on GO/MOF nanocomposites have various benefit such as, the high  
stability, the tunable porosity, the fast mast transfer and reasonable  
enrichment factor. The fabricated material was characterized via  
energy dispersive x-ray analysis (EDX), the scanning electron  
microscopy (SEM), Fourier-transform infrared spectroscopy (FT-  
IR), and the x-ray diffraction (XRD). The calibration curves revealed  
Fluoroquinolones  
2
linearity (0.9992 ≤ r ≤ 0.9997) in the ranges of 1.0-475.0, 0.5-350.0,  
-1  
.5-350.0, 0.5-375.0 and 1.5-300.0 ng mL with limit of detections  
-1  
0
(
LODs, S/N=3) of 0.3, 0.1, 0.2, 0.1 and 0.4 ng mL for ofloxacin,  
ciprofloxacin, lomefloxacin, enrofloxacin and sperfloxacin,  
respectively. The intra-assay (≤7.7%, n = 9) and inter-assay (≤7.0%,  
n = 9) precisions along with accuracy less than 9.0% showed the  
reliability of the method.  
1
. Introduction  
their high antibacterial activity and considerable  
Fluoroquinolones (FQs) such as ofloxacin,  
ciprofloxacin, lomefloxacin, enrofloxacin and  
sparfloxacin (Fig. 1) have great importance due to  
bioavailability which makes these compounds as  
efficient drugs not only for treatment of human’s  
diseases but also for prevention and treatment of  
veterinary illnesses [1]. In recent years, the FQs  
have been widely used in different infectious  
diseases due to resistance against these drugs,  
*
Corresponding Author: Mohsen Zeeb  
Email: zeeb.mohsen@gmail.com  
https://doi.org/10.24200/amecj.v4.i02.135  
6
Anal. Methods Environ. Chem. J. 4 (2) (2021) 5-24  
the various hazardous side effects and allergic  
problems [2]. Based on FQs application in animal  
husbandry, the impact of FQs has been found in a  
variety of food samples like milk, the bee products,  
chicken and eggs. Since eggs and egg yolk products  
have high protein content and some essential  
minerals, they are tremendously utilized in the diet  
of breastfed children, infants, premature babies and  
adults. Hence, it is necessary to expand reliable and  
cost-effective analytical methods to quantify trace  
amount of FQs residue in egg samples to ensure  
public health safety in humans [3-5].  
O
N
O
O
O
F
F
OH  
HO  
N
N
N
HN  
N
ro oxac n  
Cip fl  
Enrofloxacin  
i
em ca ormu a:  
l F  
C17H18FN O3  
3
e t:  
Ch  
i
l
em ca ormu a:  
Ch  
l F  
i
l
C19H22FN O  
t:  
3
3
o ecu ar  
M l  
l
W igh 331/34  
o ecu ar  
e
M l  
l
W igh 359/39  
O
O
O
O
F
F
OH  
OH  
N
N
N
N
HN  
F
N
O
oxac n  
Ofl  
i
ome oxac n  
fl  
l
i
em ca ormu a:  
l
l F C18H20FN O  
3
4
e t:  
W igh 361/37  
Ch  
i
o ecu ar  
em ca ormu a:  
Ch l  
l F C17H19F N O  
2
3
e t:  
W igh 351/35  
M l  
l
i
3
o ecu ar  
M l  
l
NH2  
O
O
F
OH  
N
N
HN  
F
ar oxac n  
Sp fl  
i
em ca ormu a:  
l
l F C19H22F N O  
2 4  
3
o ecu ar  
e t:  
M l  
W igh 392/40  
Ch  
i
l
Fig. 1. Structures of target of fluoroquinolones (FQs) such as ofloxacin, ciprofloxacin, lomefloxacin,  
enrofloxacin and sparfloxacin  
GO-MOFs/HPLC for determination five fluoroquinolones in eggs  
Fatemeh Pourbahman et al  
7
Literature survey shows that different analytical  
protocols have been reported for the determination  
ofFQswhichsufferfrommajordrawbacksincluding  
high matrix effect, low sensitivity, unacceptable  
reproducibility, high usage of hazardous reagents  
and etc. [1, 4-6]. In order to overcome these  
weaknesses, the development a sustainable sample  
preparation strategy prior to measurement is  
essential. Magnetic dispersive micro-solid phase  
extraction (MD-µ-SPE) as a promising kind of  
solid-phase extraction (SPE) offers many merits  
over other traditional sample preparation methods  
and reveals notable applications in enrichment and  
isolation of target analyses from complex matrices  
like environmental, natural, drug and food samples  
conditions. MOFs as 3-dimensional structures  
exhibit various topologies along with individual  
properties like tunable porosity, high surface  
2
-1  
area from 1000 to 10400 m g , simple synthesis  
routes, and adequate resistance. Owing to these  
possessions, these materials have been applied in  
different areas like the adsorption phenomena[22],  
the separation [23-25], the gas storage [26, 27] and  
the drug delivery[28]. Literature survey shows that  
some MOFs including Hkust-1 [29], MIL-101[30],  
MOF-5[31], UiO-66[32], MIL-100[33] have been  
applied in SPE as successful sorbents. Among of  
MOFs crystals, the MOF-74 is resulted from the  
reaction of divalent metal cations like Mg, Mn,  
Fe, Co, Ni and Zn with divergent organic ligand  
[7-10]. The major advantages of this new kind of  
called  
2,5-dihydroxybenzene-1,4-dicarboxylate  
extraction method involve significant reduction of  
toxic reagent usage, removal of time consuming  
steps like filtration and centrifugation, considerable  
automation ability and reasonable extraction yields  
along with a meaningful decrease of interference  
effects [1]. Researchers have conducted extensive  
studies over new magnetic sorbents MD-µ-SPE  
and used in different analytical purposes. However,  
the developed sorbets show some disadvantages  
involving the lack of reusability, low surface area,  
insufficient porosity, low satiability and so on [11].  
To deal with these issues, graphene oxide (GO)  
nanosheet as a novel allotrope of carbon seems  
superior choice to fabricate a new nanohybrid  
material for extraction goals. Its high surface  
area, strong hydrophobic properties, notable  
mechanical characteristics, outstanding acid and  
alkaline resistance as well as high chemical and  
thermal stability, enable it to create increasing  
π-π interactions [12, 13]. Lately, various materials  
with individual properties such as silicon-based  
compounds [14], inorganic nano-materials [15],  
metal oxides [16, 17], conducting metal polymers  
(DBDC) [34-36]. In order to enhance the qualities  
of a carbon based material for extraction purposes,  
conductive polymers such as polythionine,  
polyaniline, polythiophene, polytyramine (PTy)  
seem appreciable alternatives which significantly  
increase π-π interaction, hydrophobic property,  
extraction capacity, diffusion rate and reusability  
[37-43]. Among these polymers, PTy can be  
synthesized through a simple and inexpensive  
oxidative polymerization route in the presence of  
horseradish peroxidaze (HRP) enzyme as a catalyst  
and furthermore existence of alkyl groups in this  
polymer results the establishment of macropores on  
the surface of sorbent. The synthesized nanosorbent  
have been used in a similar way to investigate the  
prokinetic drugs on human plasma but in this study,  
as a novel research, we used synthesized sorbent to  
quantitatively probe the simultaneous, five type of  
fluroquinolone in egg sample [44].  
In the presented study, the surface of GO nanosheet  
was modified with MOF-74 to result GO/MOF-  
74 and furthermore in order to provide a super-  
magnetic material, precipitation of Fe O on the  
3
4
[
18] and MOFs [19-21] have been introduced as  
fabricated sorbent was followed. In the last step,  
the polymerization of tyramine was carried out  
using HRPenzyme to prepare recyclable GO/MOF-  
74/Fe O /PTy nanocomposite as a sustainable  
surface modifiers to enhance the merits of the GO.  
MOFs are classified a new type of highly porous  
materials which can be synthesized through an  
interaction between coordinates of metal ions  
3
4
sorbent for the MD-µ-SPE process. Ultimately,  
(nodes) and bridging ligands, under appropriate  
the extraction protocol was followed with HPLC-  
8
Anal. Methods Environ. Chem. J. 4 (2) (2021) 5-24  
UV for simultaneous extraction and quantitation  
of five fluoroquinolones including ofloxacin,  
ciprofloxacin, lomefloxacin, enrofloxacin and  
sperfloxacin in egg samples and satisfactory  
precisions along with desirable accuracies were  
obtained.  
2.3. Chromatographic analysis  
Chromatographic data were obtained using a waters  
alliance e2695 instrument (Massachusetts, USA)  
equipped with two pumps for delivering the mobile  
phase during gradient elution. UV-VIS detector  
(wavelengths of 275 and 288 nm) and C reversed  
1
8
phase column (5 µm, 250×4.6 mm id, phenomenex  
Co, Torrance, CA) at 30°C temperature were  
utilized to complete separation process. A gradient  
elution containing two types of mobile phases (A:  
phosphate buffer at pH 3 and B: acetonitrile) was  
programmed as follows: it was started at 70% A for  
12 min, increased to 85% A over 1 min and retained  
at this value for 6 min and decreased to 70% A for  
4 min. The flow rate of pump was regulated at 1  
2
2
. Experimental  
.1. Chemicals  
In this study, the analytical grade of chemicals  
and reagents were applied. These chemicals  
involviung 2, 5- Dihydroxy triphetalic acid, N,  
N- dimethylformamide, tyramine, horseradish  
peroxidaze and graphite powder (mesh of 100)  
were obtained from Merck Company (Darmstadt,  
Germany). Iron (III) chloride hexahydrate  
-1  
mL min in all experiments while the injection  
volume was set at 20 µL. The applied mobile  
phase was filtered through a 0.2 µm membrane  
filter (Millipore, Bedford, MA, USA) for further  
purification.  
(
FeCl .6H O), iron (II) chloride tetrahydrate  
3 2  
(FeCl .4H O), the sodium nitrate (NaNO ), the  
2
2
3
potassiumpermanganate(KMnO ), thesulfuricacid  
4
(H SO , 98%), the nickel (II) nitrate hexahydrate  
2 4  
[
Ni(NO ) .6H O], the sodium hydroxide (NaOH),  
3 2 2  
the hydrochloric acid (HCl 37%), the hydrogen  
2.4. Synthesis  
peroxide (H O , 30%), the ethanol (C H OH)  
2.4.1.Synthesis of GO/MOF-74  
2
2
2
5
and triethylamine were obtained from Sigma-  
Aldrich Company (St. Luise, MO, USA). The  
standards of fluoroquinolones were provided from  
Kusum Healthcare (Punjab, India). Ultrapure  
water (Millipore, Bedford, MA, USA) was used  
in all experminets. HPLC grades of methanol,  
acetonitrile, acetone and potassium dihydrogen  
phosphate were bought from Merck company  
0.25 g graphene oxide (GO was fabricated  
using hummer’s method [45] and 0.23 g of 2,  
5-dihydroxyphthalic acid and 1.13 g of Ni (No ) .  
3
2
6H O were mixed completely and a mixture  
2
containing N,N-Dimethylformamide (DMF),  
ethanol and once ionized water (1:1:1, V/V/V, 100  
ml) was added slowly to the above materials. For  
making a suspension, the obtained solution was  
sonicated in an ultrasound bath for 10 minutes [46].  
The resultant was kept inside an oven for 24 hours  
at a temperature of 100 °C and then it was cooled  
to 25 °C. The upper phase was decanted off and the  
sedimented phase was washed with methanol for 6  
times to remove any impurities.  
(Darmstadt, Germany).  
2
.2. Instrumentation  
Energy dispersive x-ray (EDX) spectra and  
scanning electron microscopy (SEM) images  
were investigated in detail via a TESCAN-Vega  
3
(TESCAN, Czech Republic), machines. All the  
X-ray diffraction (XRD) spectra were recorded  
and studied within angular range of 0-80°, using  
Kα radiation (λ= 1.54 ˚A) created by Cu element  
on a D8 Advance AXS diffractometer instrument  
2.4.2.Synthesis of GO/MOF-74/Fe O  
For synthesis of GO/MOF-74/Fe O , 0.8  
3
4
g
3
4
FeCl .6H O and 0.3 g of FeCl .4H O were mixed  
3
2
2
2
and dissolved in 25 mL deionized water. The  
fabricated GO/MOF-74 was added slowly to the  
solution under a stream of nitrogen and the pH of  
the solution was fixed at 10 using ammonia. The  
(
Bruker, Germany). All the FTIR spectra were  
recorded on a Perkin Elmer FTIR spectrometer  
RXI, Germany).  
(
GO-MOFs/HPLC for determination five fluoroquinolones in eggs  
Fatemeh Pourbahman et al  
9
resulting solution was placed into an oven at 100  
C for 24 hours and afterwards it was cooled to  
5 °C (room temperature). To remove probable  
wise. Egg samples were spiked with various levels  
of the working standard solutions for plotting  
calibration curve and further measuring. To  
demonstrate the accuracy and reproducibility of the  
presented method, different quality control samples  
of target FQs at concentration levels of 10.0, 150.0  
°
2
impurities, the upper phase was poured off and  
residue was washed for 3 times with methanol. The  
final compound was transferred into an oven with a  
temperature of 250°C and kept there for 2 hours to  
achieve a brown powder.  
-1  
and 350.0 ng mL were prepared.  
2
.6. Preparation of egg samples  
2
.4.3.Synthesis of GO/MOF-74/Fe O / polytyramine  
Two kinds of egg samples (subject) were collcted  
and prepared before using by the proposed method.  
The egg samples 1 from healthy hens without  
feeding any drugs for evaluation of inter-day/  
intra-day precisions and accuraies were used. The  
egg samples 2 from hens which had been fed a  
certain amount of five FQs once a day for 7 day  
for conduting recovery experiments and evaluating  
the reliabilty of the method were selected. In order  
to prepare egg samples, 5 g of eggs was added to  
centrifuge tubes and after that 10 mL methanol  
was added to them and centrifuged at 5000 rpm for  
10 min. The upper phase was decanted to the new  
tubes and evaporated to dryness under a stream of  
nitogen. Finally, 5 mL deionzed water was added to  
each tube and subjected to the presented extration  
protocol.  
3
4
In order to fabricate GO/MOF-74/Fe O /PTy, an  
3
4
in situ oxidative polymerization was performed  
on the surface of GO/MOF-74/Fe O through an  
3
4
enzymatic cross-linking of poly-tyramine in the  
presence of HRP enzyme as a catalyst. HRP is  
considered as a heme-containing oxidoreductase  
which composes of two broad classes of iron  
centers including a single heme group [iron (iii)  
protoporphyrin IX] and two calcium atoms,  
which catalyzes the oxidation of different organic  
substrates by hydrogen peroxide. The chemical  
equation below describes the relevant chemical  
reaction:  
where tyramine as an enzyme substrate, conjugates  
with hydrogen peroxide and thus catalyzed by  
HRP. Synthesis route was as follows: 200 mg GO/  
MOF-74/Fe O , 160 mg tyramine, 1 mg HRP, 8  
3
4
mL acetone and 4 mL phosphate buffer (0.1 M, pH  
) were completely mixed together. Then, 240 µL  
2.7. The procedure of MD-µ-SPE-HPLC-UV  
The steps of MD-µ-SPE-HPLC-UV procedure for  
isolation, enrichment and quatitation of FQs are  
shown in schema 1. Firstly, 5.0 mL of the prepared  
egg sample was placed into a centrifuge tube and  
then 10.0 mg of GO/MOF-74/Fe O /PTy was  
7
hydrogen peroxide was used to proceed the reaction  
at a temperature of 30°C. The obtained solution was  
filtered and placed into an oven and kept there until  
dryness.  
3
4
added to the tube containing the real sample. After  
that, ultrasonic irradiation was utilized for 10 min,  
to disperse the supermagnetic nanoporous sorbent  
into the solution and isolate the analytes of interest.  
The tube containing the sample was exposed to a  
powerful magnet Nd-Fe-B with a magnitude of 0.8  
tesla to collect the particles of nanosorbent at the  
bottom of the vessel. In the next step, the aqueous  
media was discarded and the remaining extractor  
was washed with 2.5 mL acetonitrile through the  
applying ultrasonic irradiation for 2 min. Then, the  
sample containing desorbed FQs was exposed to  
2
.5. Preparation of standard solutions and  
quality control samples of FQs  
In order to prepare stock solutions, required amount  
of each FQs including ofloxacin, ciprofloxacin,  
lomefloxacin, enrofloxacin and sperfloxacin was  
independently dissolved in methanol to result  
-1  
a concentration of 10.0 mg L . To prevent the  
decomposition of FQs, the stock solutions of these  
drugs were prepared every week and stored in the  
dark place at 4 °C. To obtain working standard  
solutions of FQs, stock solutions were diluted step  
1
0
Anal. Methods Environ. Chem. J. 4 (2) (2021) 5-24  
Schema 1. A: Schematic diagram of the synthesis routes of GO/MOF-74/Fe3O4/PTy. B: different steps of  
MD-µ-SPE-HPLC-UV method in extraction, enrichment and isolation of FQs  
the magnet again to collect solution. The collected  
solution was evaporated under a stream of nitrogen  
to dryness and the resultant residue was dissolved  
in 100.0 µL of the optimized mobile phase of  
HPLC. Finally, 20.0 µL of the obtained sample was  
injected into HPLC for analyzing FQs.  
3.1. Characterizations  
The illustrates of the FTIR spectrum of GO/MOF-  
74/Fe O /PTy, recorded in the range of 400–4000  
3
4
−
1
cm (Fig.2) The FTIR spectrum of the synthesized  
nanocomposite sorbent indicatesall the components  
of this structure evidently. As clearly exhibited  
in the spectrum, the broad peak at 3200-3648  
3
. Results and Discussion  
GO-MOFs/HPLC for determination five fluoroquinolones in eggs  
Fatemeh Pourbahman et al  
11  
Fig. 2. The FT-IR spectrum of GO/MOF-74/Fe O /PTy nonporous composite  
3
4
−
1
cm assigns to hydroxyl groups with stretching  
vibrations in the structure of GO. Oxygen-  
containing functional groups in the composition of  
this sorbent include epoxy C-O and C=O stretching  
vibrations with absorption peaks in the range of  
of the nanocomposite sorbent due to the following  
data: the corresponding x-ray diffraction peaks  
°
°
assigned to (220), (311), (400) at 2θ =30.3 , 43.3 ,  
°
°
57.3 , and 62.9 can be seen in the XRD patterns  
of Figure 3b and 3c, endorsing the presence of  
Fe O . Since Fe O is also integrated into the  
−1 −1  
1
100-1200 cm and 1650-1680 cm , respectively.  
3
4
2
3
The absorption peaks corresponding with aromatic  
fabricated nano-hybrid sorbent, other diffraction  
° ° °  
absorption bonds with C=C stretching vibrations  
peaks at 33.2 , 40.8 , and 35.6 related to (104),  
(110), (113) plates can be identified, manifesting  
the presence of Fe O in the sorbent as well as  
−
1
are located in the range of 1410-1450 cm . Due  
to the adjusted attachment of magnetic Fe O on  
3
4
2
3
the surface of GO, a peak is observed at 500-580  
Fe O . Moreover, the grain size and morphology  
3 4  
−
1
cm , which attributes to the stretching vibrations  
of Fe-O. µ-hydroxo groups can also be identified  
in the corner-sharing hexagonal units of MOF-74  
and of nanoporous composite was evaluated  
by SEM images of GO (d), GO/MOF-74/Fe O4  
3
(e) and GO/MOF-74/Fe O /PTy (f) in Figure 3.  
3
4
−
1
with two sharp peaks at 850-950 cm [48]. Other  
As illustrated in Figure 3d, GO nanosheets were  
stacked in condensed layers within the lamellar  
morphological components. Moreover, it shows  
that wrinkles and folds were observed in robust  
agglomeration of graphene sheets, which consists  
of multiple agglomerated layers of graphene, with  
a strong tendency to stack due to the high surface  
energy caused by strong interactions of surface  
groups on the graphene layer. Figure 3e exhibits  
the crystal growth mechanism and evolution  
of MOF-74 and Fe O particles over the GO  
−
1
peaks placed in the range of 1210-1250 cm are  
related to N-H and C-N vibrations, respectively.  
In the XRD spectrum (Fig. 3), the peaks associated  
with GO, GO/MOF-74/Fe O , and GO/MOF-74/  
3
4
Fe O /PTy are meticulously compared with each  
3
4
other. The XRD pattern with diffraction peak  
°
assigned to (101) at 2θ=11.281 , which was shown  
in Figure 3a, confirms the GO structure. As Figure  
3
b and 3c, the MOF structure is clearly exhibited  
in the XRD pattern that confirms its unique crystal  
structure according to the x-ray reflection indexed  
3
4
nanosheet that resulted in development of sphere-  
like morphologies, appropriately distributed over  
GO surface. In Figure 3f, SEM image of GO/MOF-  
°
to (110) to (300) and diffraction peaks at 2θ=7  
°
and 12 . Also, Fe O can be found in the structure  
3
4
1
2
Anal. Methods Environ. Chem. J. 4 (2) (2021) 5-24  
Fig. 3. XRD patterns of GO (a), GO/MOF-74/Fe O (b) and GO/MOF-74/Fe O /PTy (c); SEM images  
3
4
3
4
of GO (d), and GO/MOF-74/Fe O (e) and GO/MOF-74/Fe O /PTy (f)  
3
4
3
4
7
4/Fe O / PTy obviously shows the modification  
current data exhibit the homogeneous distribution  
of the contents of MOF-74 such as Ni, C and O  
elements in both groups, confirming the effective  
attachment of MOF-74 blocks with GO layers.  
For more evidences, an increase in mass percent  
of carbon material from 31.2 to 49.2% proves the  
presence of GO in GO/MOF-74 composite, which  
firmly demonstrates well dispersion of target MOF  
on the GO sheets.  
3
4
process of GO with the layers of target polymer.  
As it can be seen, PTy layers have grown on the  
surface of GO and formed significant coating  
sheets, demonstrating prosperous synthesis of the  
final nanoscale extractor.  
When crystalline MOF-74 particles in Figure  
4
a are evenly dispersed on the surface of GO  
sheets, MOF-74 would adhere to GO (Fig. 4b).  
SEM image of MOF-74 seems to be very similar  
when compared to GO/MOF-74 image in Figure  
In Figure 5, the EDX spectrum of GO confirms  
the existence of C and O elements, with weight  
percent of 77.1% and 18.5%, respectively. Since  
MOF-74 is obtained from the reaction between of  
nickel cation and ligand 2,5-dihydroxybenzene-  
1,4-dicarboxylate, Ni, C, and O appear at 39.8%,  
4
a and 4b. Hence, by referring to EDX spectra of  
MOF-74 and GO/MOF-74, it could be possible  
to determine the successful immobilization of  
MOF-74 on the surface of GO (Fig. 5). The  
GO-MOFs/HPLC for determination five fluoroquinolones in eggs  
Fatemeh Pourbahman et al  
13  
Fig. 4. SEM images of MOF-74(a), GO/MOF-74 (b)  
Fig. 5. EDX spectrum of GO, MOF-74, GO/MOF-74 and GO/MOF-74/Fe O /Pty  
3
4
3
1.2%, and 29%, respectively. When MOF is  
bonded to GO, the carbon content increased from  
1.2% to 49.2%, designating the proper adjustment  
3.2. Influence of nanosorbent dosage  
In the enrichment protocols based on nanoporous  
sorbents, the amount of extractor is an important  
factor which effects both reproducibility and  
sensitivity features [49]. To achieve the best  
performance of the extraction method for analysis  
of FQs, various amounts of the fabricated  
3
of MOF-74 on the GO surface. In the EDX  
spectrum of GO/MOF-74/ Fe O /PTy, Fe and N,  
3
4
associated with Fe O and PTy, respectively, can  
3
4
be recognized in addition to previous components.  
1
4
Anal. Methods Environ. Chem. J. 4 (2) (2021) 5-24  
Fig. 6. Influence of GO/MOF-74/Fe3O4/PTy composite amount, other conditions:  
−
1
concentration of each FQs 20.0 ng mL ; pH 5.0; extraction time 10 min; eluting solvent  
acetonitrile; desorption time 2 min.  
nanocomposite within the range of 1.0-30.0 mg  
were investigated in detail. As Figure 6 shows,  
there is a significant and direct relationship between  
peak area of FOs and amounts of nanosorbent  
from 1.0 to 10.0 mg. GO/MOF-74/Fe O /PTy has  
compounds are as follow: (5-5.5) for pK , (6.2-  
a1  
6.4) for pK , and (8.9-9) for pK [5]. pH of the  
a2  
a3  
sample media plays a meaningful role on the  
type of interactions between sorbent and FQs  
controlling the adsorption phenomena of analytes  
and the subsequent extraction yields. The impact  
of pH solution on the determination of FQs was  
evaluated in the range of 1.0-12.0 by applying 0.01  
M HCl and NaOH. As it can be revealed in Figure  
7, the best quantification condition was obtained at  
pH 5.0, which the following explanations exhibit  
3
4
high surface area-to-volume ratio resulting the  
maximum analytical sensitivity is attainable at a  
relatively low amount of sorbent (10.0 mg), which  
can be considered as a prominent advantage of the  
new designed extractor. But after the value of 10.0  
mg, a decrease in signal was observed, which was  
due to this fact that at higher amounts of sorbent,  
the separation of analytes from the extractor using  
the magnet could not be performed effectively and  
a certain amount of FQs remains in sample. Hence,  
the probable reason: according to the pK values  
a
of all FQs, at pH 5 the neutral forms (uncharged  
forms) of drugs are dominant and due to the  
hydrophobic property of GO/MOF-74/Fe O /PTy,  
3
4
1
0.0 mg of GO/MOF-74/Fe O /PTy was operative  
the hydrophobic-hydrophobic interactions between  
analytes and sorbent become prevalent at this pH  
resulting higher recovery values. Hence, pH 5.0  
was chosen as the optimum in all enrichment steps,  
in order to achieve the best performance of the  
method in the trace monitoring of FQs.  
3
4
enough to obtain a compromise between analytical  
sensitivity and repeatability of data, so this value  
was utilized for the rest of the work.  
3
.3. Influence of pH  
Owing to the presence of carboxyl and amino  
groups in FQ structures, FQs exist as ionized or  
neural forms depending on the pH of the aqueous  
3.4. Influence of ultrasonic irradiation and  
extraction time  
media, while the reported pK values for these  
It is well-known that application of ultrasonic  
a
GO-MOFs/HPLC for determination five fluoroquinolones in eggs  
Fatemeh Pourbahman et al  
15  
Fig. 7. Influence of sample pH, other conditions: concentration of each FQs 20.0 ng  
−
1
mL ; sorbent amount 10.0 mg; extraction time 5 min; eluting solvent acetonitrile;  
desorption time 2 min.  
Fig. 8. Influence of extraction time, other conditions: concentration of each FQs 20.0 ng  
−1  
mL ; sorbent amount 10.0 mg; pH 5.0; eluting solvent acetonitrile; desorption time 2 min.  
irradiation has reasonable potential for dispersing  
the sorbent into the whole sample while the  
time of irradiation either plays a significant role  
on a successful extraction process. The time of  
irradiation is considered as the extraction time  
which a desirable value causes better mass transfer  
and more sensitive signals [50]. The influence of  
extraction time on analytical signals was examined  
from 0 to 14 min and the obtained data are shown in  
Figure 8. Stable and sensitive results were obtained  
at 10 min revealing a relatively rapid isolation of  
drugs have been happened, which is due to the high  
1
6
Anal. Methods Environ. Chem. J. 4 (2) (2021) 5-24  
Fig. 9. Influence of acetonitrile volume, other condition: concentration of each FQs 20.0  
−1  
ng mL ; sorbent amount 10.0 mg; pH 5.0; extraction time 10 min; desorption time 2 min.  
porosity of the sorbent.After 10.0 min the analytical  
signals slowly decrease owing to this fact that at  
higher time values, FQs are separated from the  
sorbent and re-entered to the solution. According to  
these criteria, 10.0 min was good enough to cover  
all necessities associated to quantification features  
and this value was selected in all experiments.  
3.6. The influence of salt concentration  
In analytical chemistry there is a well-known  
phenomenon termed salting out effect which is  
based on non-electrolyte-electrolyte interactions.  
Non-electrolytes are less soluble in water at high  
values of salt and as a result the adsorption process  
could be prevalent. Thus, in this study different  
samples containing NaCl from concentration levels  
from 0 to 10% w/v were studied to evaluate the  
salting out effect on the extraction of FQs. It was  
expected by adding salt, the solubility of analytes  
in aqueous phase decreases due to an increase  
in polarity of the aqueous medium, and thus, the  
extraction performance improves [51, 52] But as  
it is clear in Figure 10, the analytical sensitivities  
have been missed by increasing the salt level. The  
latter happening can be explained as follows: at  
higher concentrations of NaCl, the sample become  
more viscose and make the mass transfer of FQs  
so difficult that results a meaningful decline in  
analytical signals. Finally, in order to obtain better  
condition, no electrolyte was used in all evaluations.  
3
.5. Desorption condition  
Toevaluatethebestdesorptioncondition,different  
kinds of organic solvents such as methanol,  
acetonitrile and acetone as eluting agents with  
different volumes were tested. The volume and  
kind of eluting agents significantly affect the  
enrichment and isolation of target drugs so it is  
essential to carefully evaluate these parameters in  
detail. Acetonitrile exhibited individual and more  
practical desorbing ability in comparison with  
other solvents. After selecting the kind of solvent,  
its volume should be taken to the account, hence  
various volume of acetonitrile from 0.5 to 6.0 mL  
were subjected to the extraction protocol and as  
it can be seen in Figure 9, 2.5 mL of this solvent  
was adequate to deal with all necessary issues  
and provide reproducible and sensitive data.  
3.7. Evaluation of Reusability  
To evaluate the reusability of GO/MOF-74/Fe O /  
3
4
GO-MOFs/HPLC for determination five fluoroquinolones in eggs  
Fatemeh Pourbahman et al  
17  
Fig. 10. Influence of ionic strength, other conditions: concentration of each FQs 20.0  
−
1
ng mL ; sorbent amount 10.0 mg; pH 5.0; extraction time 10 min; eluting solvent  
acetonitrile; desorption time 2 min.  
PTy, the number of adsorption-desorption cycles must  
be examined. Reusability is considered an essential  
characteristic of nanoscale sorbents, in order to reduce  
the cost of analyses and provide reliable data. To study  
this capability of magnetic sorbent, after extraction  
process it was washed with 1.5 mL deionized water  
and 1.5 mL acetonitrile during the application of  
ultrasonic for 6 min. Then, the magnetic nanosorbent  
was allowed to be dried at room temperature and  
reused for other subsequent extractions. It was  
found that after 15 adsorption-desorption cycles, the  
recovery values decreased around 13%.  
respectively. The mentioned analytical figures  
of merit along with calibration curve equation,  
extraction recovery (ER) and enrichment factor are  
summarized in Table 1. EF value of each FQ was  
defined as the ratio of the calibration curve slope  
before and after extraction method. ER values were  
calculated using the equation (I):  
ER% = EF × (VFinal volume/VInitial volume) × 100 (Eq. I)  
Figure 11 shows the HPLC chromatograms for  
blank sample and egg sample with different spiked  
level of FQs. The obtained chromatogram exhibits  
other contaminants existing in the egg samples  
have no notable effect on the recording of data and  
subsequent measurements.  
3
.8. Analytical figures of merit  
Analytical aspects of the presented MD-µ-SPE-  
HPLC-UV were evaluated and main features are  
as follow: calibration curves revealed satisfactory  
2
linearity (0.992 ≤ r ≤ 0.997) in the range of 1.0-  
3.9. Evaluation of precision and accuracy  
4
75.0, 0.5-350.0, 0.5-350.0, 0.5-375.0 and 1.5-  
-1  
00.0 ng mL with limit of detections (LODs, S/  
-1  
Intra-day (within one day) and inter-day (within three  
days) precisions along with related accuracies were  
studied and estimated through the analyses of various  
quality control (QC) samples in the concentration  
3
N=3) of 0.3, 0.1, 0.2, 0.1 and 0.4 ng mL and limit  
of quantifications (LOQs, S/N=10) of 1.0, 0.5, 0.5,  
-1  
-1  
0
.5 and 1.5 ng mL for ofloxacin, ciprofloxacin,  
levels of 10, 150 and 350 ng ml . Each QC sample  
lomefloxacin, enrofloxacin and sperfloxacin,  
was obtained from spiking the drug under study into  
1
8
Anal. Methods Environ. Chem. J. 4 (2) (2021) 5-24  
Table 1. Various analytical figures of merit of MD-µ-SPE-HPLC-UV.  
LDR  
ng mL )  
LOD  
(ng mL )  
LOQ  
-1  
ER%  
(n=3)  
2
Analyte  
Linear equation  
r
EF  
-1  
-1  
(
(ng mL )  
Ofloxacin  
1.0-475.0  
0.5-350.0  
0.5-350.0  
0.5-375.0  
Y=106X + 93  
0.992  
0.996  
0.995  
0.997  
0.995  
0.3  
1.0  
43.6  
87.2  
90.0  
86.8  
91.3  
88.5  
Ciprofloxacin  
Lomefloxacin  
Enrofloxacin  
Sparfloxacin  
Y=137X + 128  
Y=126X + 114  
Y=128X + 205  
Y=95X + 89  
0.1  
0.2  
0.1  
0.4  
0.5  
0.5  
0.5  
1.5  
45.0  
43.4  
45.6  
44.2  
1.5-300.0  
2
LDR: Linear dynamic range; r : Correlation coefficient; LOD: Limit of detection; LOQ: Limit of quantification; EF: Enrichment  
factor; ER: Extraction recovery  
Fig. 11. Various HPLC-UV chromatograms of ofloxacin, ciprofloxacin, lomefloxacin,  
enrofloxacin, sparfloxacin after enrichment protocol: egg sample as the blank  
after applying MD-µ-SPE (a); Spiked egg samples after applying MD-µ-SPE with  
-1  
-1  
concentration level of each FQs at (b) 25.0 ng mL , (c) 50.0 ng mL , and (d) 150.0 ng  
-1  
mL . (1) ofloxacin, (2) ciprofloxacin, (3) lomefloxacin, (4) enrofloxacin, (5) sparfloxacin.  
GO-MOFs/HPLC for determination five fluoroquinolones in eggs  
Fatemeh Pourbahman et al  
19  
Table 2. Intra-day and inter-day precisions along with corresponding accuracies for trace measument of ofloxacin,  
ciprofloxacin, lomefloxacin, enrofloxacin, sparfloxacin in spiked egg samples.  
Intra-day, n = 9  
Inter-day, n = 9  
Conc.  
(
Drug  
-1  
ng mL )  
Found RSD  
A c c u r a c y Found  
RSD  
(%)  
Accuracy  
(%)  
-1  
-1  
(ng mL )  
(%)  
(%)  
(ng mL )  
1
0.0  
10.6 ± 0.4  
3.8  
4.9  
6.0  
9.3 ± 0.5  
5.4  
5.7  
4.2  
7.6  
5.5  
5.8  
7.4  
6.6  
5.4  
7.7  
5.8  
7.1  
8.6  
5.7  
6.3  
-7.0  
-6.0  
6.0  
Ofloxacin  
150.0  
143.9 ± 7.1  
-4.1  
-5.9  
-4.0  
6.3  
141.0 ± 8.0  
371.8 ± 15.6  
10.5 ± 0.8  
162.0 ± 9.0  
379.3 ± 22.0  
9.4 ± 0.7  
3
50.0  
0.0  
329.5 ± 16.8 5.1  
1
9.6 ± 0.4  
4.2  
5.0  
Ciprofloxacin  
Lomefloxacin  
150.0  
159.5 ± 8.6  
5.4  
8.0  
3
1
1
3
1
50.0  
362.0 ± 14.4 4.0  
3.4  
8.4  
0.0  
10.3 ± 0.6  
5.8  
3.0  
-6.0  
-7.6  
-7.8  
-9.0  
-8.6  
5.8  
50.0  
50.0  
0.0  
140.6 ± 5.7  
4.0  
-6.3  
-7.9  
6.0  
138.5 ± 9.1  
322.4 ± 17.3  
9.1 ± 0.7  
322.5 ± 15.3 4.7  
10.6 ± 0.6  
5.7  
5.3  
Enrofloxacin  
Sparfloxacin  
150.0  
155.5 ± 8.2  
3.7  
137.0 ± 7.9  
370.4 ± 26.6  
9.3 ± 0.8  
3
50.0  
0.0  
324.1 ± 22.7 7.0  
-7.4  
4.0  
1
10.4 ± 0.5  
4.8  
4.9  
-7.0  
-6.5  
-8.3  
150.0  
50.0  
156.4 ± 7.7  
4.3  
140.3 ± 8.3  
321.0 ± 20.4  
3
325.9 ± 18.1 5.5  
-6.9  
RSD (%) values are determined as 100 × SD/mean; Accuracy (%) values were defined as (mean level found – known level)/  
known level); Three independent analyses were obtained for every concentration of target FQs.  
(
the egg sample, in order to examine the developed  
method in the analysis of real matrix. The results  
of the recent experiments are completely shown in  
Table 2. As it can be seen, reasonable intra-assay  
matrices, it was applied for analyzing target drugs  
in egg samples. The egg samples from hens which  
had been fed the drug per day with 7 days were  
subjected the extraction protocols and the obtained  
results are summarized in Table 3. Furthermore, egg  
samples were spiked with different amounts of FQs  
and after analyzing the samples, the recovery values  
in three independent measurements were calculated.  
The recovery values for all FQs varied from 91.0 to  
106.8% and relative standard deviations (RSDs%)  
were in the range of 3.3-7.2% which demonstrate the  
validity of the method in analysis of complicated real  
matrices like egg samples.  
(≤7.7%, n = 9), inter-assay (≤7.0%, n = 9) as well  
as accuracy values (<9.0%) were obtained which  
all demonstrate the reliability of the method for  
simultaneous trace screening of FQs in real samples.  
3
.10. Application of the method to egg sample  
analysis  
TocheckthevalidityoftheMD-µ-SPE-HPLC-UVfor  
simultaneous trace monitoring of FQs in complicated  
2
0
Anal. Methods Environ. Chem. J. 4 (2) (2021) 5-24  
Table 3. Simultaneous monitoring of ofloxacin, ciprofloxacin, lomefloxacin, enrofloxacin, sparfloxacin  
in egg samples by the developed method.  
-1  
-1  
Analytes  
Added (ng mL )  
Found (ng mL )  
5.8  
RSD (%, n=3)  
Recovery (%)  
-
5.3  
4.9  
6.0  
5.9  
4.8  
6.0  
5.5  
5.4  
5.1  
7.2  
4.3  
4.0  
3.3  
4.9  
4.4  
5.0  
4.8  
5.2  
6.8  
6.0  
-
5
2
5
-
10.1  
28.0  
59.6  
3.7  
93.5  
91.0  
106.8  
-
Ofloxacin  
5
0
2
2
5
-
5.3  
93.0  
93.9  
94.4  
-
Ciprofloxacin  
Lomefloxacin  
5
0
26.6  
50.7  
3.1  
2
2
5
-
4.7  
92.2  
105.0  
93.6  
-
5
0
29.5  
49.7  
14.5  
15.2  
37.0  
59.7  
8.2  
2
2
5
0
5
2
5
92.1  
93.7  
92.6  
-
Enrofloxacin  
Sparfloxacin  
5
0
12.3  
31.2  
53.8  
93.2  
94.0  
92.4  
5
0
Three independent measurements were carried out for each concentration level and mean values were calculated.  
3
.11. Comparison with other methods  
4. Conclusions  
To highlight the robustness of the method,  
major analytical figures of merit including RSD,  
A four-part magnetic nanoporous GO/MOF-  
74/Fe O /PTy was effectively fabricated and  
3
4
2
LOD, LOQ, correlation coefficient (r ) along  
employed as a capable sorbent for MD-µ-SPE.  
Surface immobilization of GO with modifier agents  
including MOF-74, PTy and iron oxide significantly  
improved the merits of the hybrid materials and  
provided notable advantages like improvement of  
aromatic-aromatic interactions, high mass transfer,  
desired porosity, worthy reusability, easy-to-  
recycle the magnetic nanosorbent and reasonable  
recovery values. The results exhibited that MD-  
µ-SPE in combination with HPLC-UV is a valid  
protocol of enrichment and simultaneous trace  
level quantification of fluoroquinolones in real  
media like egg samples. The satisfactory sensitivity  
and reproducibility along with acceptable  
accuracy without considerable interferences  
form contaminants in egg matrices demonstrated  
the reliability of the method for trace screening  
purposes, and according to these criteria it possesses  
with some extraction features were compared  
with previously reported methods in literature.  
The results of the current investigation are  
summarized in Table 4. As it can be seen,  
the developed protocol exhibits notable  
improvements in approximately all analytical  
features besides a comparable extraction time  
over other reported procedure. Furthermore,  
the MD-µ-SPE-HPLC-UV reveal some worthy  
advantages like a reduction in the usage of toxic  
solvent in comparison with conventional SPE  
methods, opportune magnetic separation with  
the no need of individual device, easy-to-recycle  
the magnetic nanosorbent that can be used more  
than 14 times along with the possibility of trace  
simultaneous screening of target drugs with the  
least interferences.  
GO-MOFs/HPLC for determination five fluoroquinolones in eggs  
Fatemeh Pourbahman et al  
21  
Table 4. Comparison of MD-µ-SPE-HPLC-UV with other reported methods in literature  
for quantitation of different fluoroquinolones in eggs.  
Extraction  
Method  
Extraction  
Phase  
LOD  
(μg L )  
LOQ  
(μg L )  
Extraction RSD Detection  
2
r
Ref.  
-1  
_1  
time(min)  
(%)  
system  
HPLC-UV  
**LC  
MSPE  
SPME  
DSPE  
SPE  
C18  
0.5-5  
0.7-17  
*10-30  
0.9990-7  
0.986-7  
0.9996-9  
0.9994-7  
>0.995  
NR  
12  
10  
10  
5
<5  
[11]  
[46]  
[47]  
[6]  
C18  
C18  
*3-10  
NR  
a
a
0.1-2.6  
0.4-8.6  
1-7  
HPLC  
b
ENVI-18 disk  
0.7, 2  
<10  
2, 6  
NR  
<10  
HPLC  
SFE  
C18  
50  
>54  
2
NR  
HPLC-F  
HPLC-F  
HPLC  
[53]  
[54]  
[55]  
PLE  
C -silica  
0.4-33.5  
0.2-19.8  
<23  
8
C
d
d
MSPE  
PA  
0.4-1.4  
1.1-4.5  
0.9974-1  
0.992-7  
3.6-17.6  
MD-µ-SPE GO/MOF/Fe O /PTy  
0.1-0.4  
0.5-1.5  
10  
3.3-7.2 HPLC-UV This work  
3
4
a
b
C
d
*
μg/kg,** LC-FLC-TMS, μg/ g, polystyrene-divinylbenzene copolymer disk, PA:One-dimensional polyanilines, ng/g,  
MSPE: magnetic solid phase extraction  
SPME: solid-phase microextraction  
DSPE: dispersive solid phase extraction  
PLE: pressurized liquid extraction  
NR: not reported  
RP-HPLC/UV: Reversed phase high performance liquid chromatography  
RP-HPLC-F: reversed phase high-performance liquid chromatography with fluorescence detection  
HPLC-UV: high performance liquid chromatography with UV detection  
DMIP: dummy molecularly imprinted polymers  
appreciable potential to be employed in the other  
applications related to the food aspects.  
8248.  
[4] A. Gajda, A. Posyniak, J. Zmudzki, M.  
Gbylik, T. Bladek, Determination of (fluoro)  
quinolones in eggs by liquid chromatography  
with fluorescence detection and confirmation  
by liquid chromatography–tandem mass  
spectrometry, food chem., 135 (2012) 430-  
439.  
5
. Acknowledgements  
The authors appreciate Islamic Azad University  
South Tehran Branch for provided grant and we also  
thank Miss Zahra Shojaei and Mr Sajad Arzbin for  
cooperating to perform the HPLC measurements.  
[
5] JF. Huang,B. Lin, QW. Yu, YQ. Feng,  
Determination of fluoroquinolones in eggs  
using in-tubensolid-phase microextraction  
6
. References  
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1] H. Wu, Y. Liu, J. Chang, B. Zhao, Y.  
Huo, Zh. Wang, Y. Shi, Extraction of Five  
Fluoroquinolones in Eggs by Magnetic  
Solid-Phase Extraction with Fe O –MoS and  
coupled  
to  
high-performance  
liquid  
chromatography, Anal. Bioanal. Chem., 384  
(2006) 1228–1235.  
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Determination by HPLC-UV, Food Anal.  
Methods, 12 (2019)712-721.  
[6] M. Sturini, A. Speltini, L. Pretali, E. Fasani,  
A. Profumo, Solid-phase extraction and HPLC  
determination of fluoroquinolones in surface  
waters, J. Sep. Sci., 32 (2009) 3020-3028.  
[7] IS. Ibarra, JA. Rodriguez, CA. Galán-Vidal,  
A. Cepeda, JA. Miranda, Magnetic solid phase  
extraction applied to food analysis, J. Chem.,  
8 (2015) 1-13.  
[
2] Wm. Scheld, Maintaining fluoroquinolone  
class efficacy: review of Influencing factors,  
Emerg. Infect. Dis., 9 (2003)1-9.  
[
3] H. Yan, F. Qiao, KH. Row, Molecularly  
imprinted-matrix solid-phase dispersion for  
selective extraction of five fluoroquinolones in  
eggs and tissue, Anal. Chem., 79 (2007) 8242-  
[8] ShV. Gopalan, AN. Hasanah, MI-SPE, M-SPE  
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2
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AND M-SPD recent application on solid phase  
[17]Xu. XubiaoLuo, Ch. Wang, Sh. Luo, R. Dong,  
X. Tu, Gu. Zeng, Adsorption of As (III) and As  
(V) from water using magnetite Fe O -reduced  
extraction for compound extraction of complex  
matrices, Int. J. App. Pharm., 11 (2019)16-25.  
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4
[
9] L. Reis, L. Lorena Vidal, A. Canals,  
Determination of siloxanes in water  
samples employing graphene oxide/Fe O  
graphite oxide MnO nanocomposites, Chem.  
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