Bioinspired Polyelectrolyte-Assembled Graphene-Oxide-Coated C18

Publication Date (Web): May 18, 2016 ... chloride) (PDDA) assembled graphene oxide (GO)-coated C18 composite particles (C18@GO@PDDA) onto a quartz ...
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Bioinspired polyelectrolyte-assembled graphene-oxidecoated C18 composite solid-phase microextraction fibers for in vivo monitoring of acidic pharmaceuticals in fish Junlang Qiu, Guosheng Chen, Shuqin Liu, Tianlang Zhang, Jiayi Wu, Fuxin Wang, Jianqiao Xu, Yan Liu, Fang Zhu, and Gangfeng Ouyang Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.analchem.6b00417 • Publication Date (Web): 18 May 2016 Downloaded from http://pubs.acs.org on May 24, 2016

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Bioinspired Polyelectrolyte-Assembled Graphene-Oxide-Coated C18 Composite Solid-Phase Microextraction Fibers for in Vivo Monitoring of Acidic Pharmaceuticals in Fish

Junlang Qiu, Guosheng Chen, Shuqin Liu, Tianlang Zhang, Jiayi Wu, Fuxin Wang, Jianqiao Xu, Yan Liu, Fang Zhu*, and Gangfeng Ouyang*

MOE Key Laboratory of Aquatic Product Safety/KLGHEI of Environment and Energy Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, China

*

Corresponding author. Tel. & Fax: +86-20-84110845

E-mail: [email protected] (F. Zhu); [email protected] (G. Ouyang).

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ABSTRACT A novel solid-phase microextraction (SPME) fiber was prepared by gluing poly(diallyldimethylammonium chloride) (PDDA) assembled graphene oxide (GO) coated C18 composite particles (C18@GO@PDDA) onto a quartz fiber with polyaniline (PANI). The fiber surface coating was sequentially modified with bioinspired polynorepinephrine, which provided a smooth bio-interface and make the coating suitable for in vivo sampling. The novel custom-made coating was used to extract acidic pharmaceuticals and high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) was employed for analysis. The custom-made coating exhibited a much higher extraction efficiency than the previously used commercial polydimethylsiloxane (PDMS) and polyacrylate (PA) coatings. The custom-made coating also possessed satisfactory stability (the relative standard deviations (RSDs) ranged from 1.60% to 10.3% for six sampling-desorption cycles), interfiber reproducibility (the RSDs ranged from 2.61% to 11.5%), and resistance to matrix effects. The custom-made fibers were used to monitor the presence of acid pharmaceuticals in dorsal-epaxial muscle of living fish, and satisfactory sensitivities (limits of detection ranged from 0.13 ng/g to 7.56 ng/g) were achieved. The accuracies were verified by the comparison with liquid extraction. Moreover, the novel fibers were successfully used to monitor the presence of acidic pharmaceuticals in living fish, which demonstrated that the custom-made fibers were feasible for possible long-term in vivo continuous pharmaceutical monitoring.

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INTRODUCTION As a solvent free and non-exhaustive sample preparation technique that integrates sampling, isolation and enrichment into one step, SPME has been widely applied to different fields1,2 since its appearance in the 1990s.3 In recent years, in vivo SPME appears to be receiving attention as a sampling and sample preparation method for detecting analytes of interest in living biotas, including clinical analysis,4 pollutant detection,5 metabolomics detection,6 and central nervous system studies.7 The advantages of in vivo SPME compared to other in vivo analytical methods have been well demonstrated in the literature such as the short sampling duration and the feasibility for a wide variety of analytes.8 The emerging applications of SPME focus on the detection of highly polar exogenous and endogenous bioactive compounds in tissues of living animals, including studies on acidic pharmaceuticals.4 However, compared with studies detecting volatile and semivolatile analytes with SPME,9 these studies are still scarce, which is mainly due to the lack of proper fibers for sampling highly polar compounds in living animals.4,6,7,10,11 The preparation of SPME fibers for sampling highly polar compounds in living animals is quite challenging. Firstly, the ionization of the analytes at physiological pH can make it difficult to achieve satisfactory enrichment factors in the fiber coatings. In addition, the fibers are required to be biocompatible and resistant to matrix effects to avoid rejection reactions and binding of biomacromolecules. Moreover, the size of the fibers should be small to reduce the invasiveness imparted on the living systems.12 At present, several varieties of

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materials have been explored to prepare SPME fiber coatings,1 including ionic liquids,13,14

carbonaceous

materials,15,16

molecularly

imprinted

polymers,17,18

metalorganic frameworks19,20 and metal oxides.21,22 However, due to unfavorable properties, such as obvious matrix effects and weak robustness in biological semi-solid matrices,1 coatings with enhanced sensitivity and stability for in vivo SPME are in great need. C18 is a type of surface modified amorphous silica particles that has good adsorption ability and is widely used in solid-phase extraction and solid-phase microextraction. In recent years, C18-functionalized SPME fibers have been used to determine polycyclic aromatic hydrocarbons and pesticides in water samples.

23,24

Biocompatible C18 composite probes were also designed for in vivo or in vitro study of biological samples.25,26 GO is an oxidized derivative of graphene (G). G has many beneficial properties, including a large specific surface area, a large delocalized π-electron system, and soft and flexible physical properties.27-29 In addition to the excellent properties of G mentioned above, GO has other attractive features. Due to the various existing

polar moieties (hydroxy, carboxyl, epoxy, carbonyl, etc.), GO

has a more polar and hydrophilic character than graphene.30,31 PDDA is a cationic polyelectrolyte agents that has been widely used in many fields.32-34 One of the features of PDDA is that it carries a strong positive charge, which leads to the generation of strong electrostatic attractions between the adsorbent and acidic compounds. Lee et al. discovered that the catecholamine dopamine undergoes oxidative

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polymerization resulting in spontaneously coating virtually any present solid surfaces and providing a bioinspired covering layer.35 Recently, another catecholamine, norepinephrine (NE), was found to follow a similar but kinetically slower oxidative polymerization process compared to polydopamine (pDA). The polymerization process can generate a pNE coating, and this coating presents the same properties as pDA, such as hydrophilicity and the bio-interface property.36 However, the pNE coating is more uniform and thinner compared to the pDA coating. Moreover, the pNE coating exhibits no aggregates, whereas the pDA coating exhibits uneven coating with the formation of significant aggregates. Thus, the performance of pNE applied as a bioinspired sheath is much better than that of pDA.37 Hence, the PDDA-assembled GO-coated C18 composite particles were prepared and developed as a SPME fiber coated with PANI by the dip-coating method. The bioinspired surface modification by pNE was subsequently carried out. These custom-made novel SPME fibers were demonstrated to be much more efficient than the previously used PDMS and PA fibers, and they were then successfully used for the in vivo monitoring of targeted acidic pharmaceuticals in fish dorsal-epaxial muscle.

EXPERIMENTAL SECTION Reagents and Materials. Fluoxetine (FLU) and the deuterated standards fluoxetine-d5 were purchased from Toronto Research Chemicals Inc. (Toronto, Canada). Tolfenamic acid (TOL), mefenamic acid (MEF), flufenamic acid (FLUF), acetylsalicylic acid (ASP), and gemfibrozil (GEM) were purchased from Tokyo

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Chemical Industry Co. Ltd. (Tokyo, Japan). Ketoprofen (KET), naproxen (NAP), ibuprofen (IBU), flurbiprofen (FLUR), polyacrylonitrile (PANI) and norepinephrine (NE) were purchased from J&K scientific Ltd. (Beijing, China). HPLC grade methanol, and tri(hydroxymethyl)aminomethane hydrochloride (Tris buffer) were purchased from Sigma-Aldrich Co. Ltd. (St. Louis, USA). Dimethylformamide (DMF) and PDDA were purchased from Aladdin Reagent (Shanghai, China). The 3.5 µm C18 was obtained from an Agilent Zorbax high performance liquid chromatography column (Palo Alto, USA). The quartz fiber (660 µm O.D.) was obtained from Scitlion Technology Co. Ltd. (Beijing, China). Preparation of the C18@GO@PDDA Particles. The GO solution was prepared by the oxidation of natural graphite powders based on a modified Hummer’s method. Then, a freeze-drying process was conducted to obtain the GO powder. The preparation process of C18@GO@PDDA particles was preliminarily designed according to a previous study38 then optimized based on the feasibility and the morphology of the particles. The optimized process can be briefly described as follow: 10 mg of GO was added to 10 mL of DMF, which was ultrasonicated for 2 hours. When the GO was well dispersed, 20 mg of C18 particles and 10 mg of DCC were added. Then, the mixture was stirred (500rpm) at 40℃ for 24 h to bond the GO to the C18 particles. Then, 10 mg C18@GO particles was added into 5 g of a 2 wt% PDDA solution and dispersed by ultrasonication. The suspension was continuously stirred for 5 h at room temperature to form C18@GO@PDDA (Figure 1A). Preparation of the Custom-made Fibers. Quartz fibers (QFs) were cut into 4-5

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cm segments followed by sonication in water, methanol and acetone. After sonication, the QFs were then soaked in 0.1 M sodium hydroxide for 30 min to activate the surface, and the excess sodium hydroxide was then neutralized with hydrochloric acid. Finally, the QFs were dried at room temperature. The preparation process for the custom-made fibers was preliminarily designed according to our previous study39 then optimized based on the morphology of the coating and the extraction performance. The optimized process can be briefly described as follow: 40 mg PANI was fully dissolved in 0.6 g anhydrous DMF in a 1.5 mL plastic tube with sonication for 1 h. Then, 40 mg of the C18@GO@PDDA particles were then added to the plastic tube. The mixture was further sonicated for 30 min to form a dispersed slurry. The pretreated QFs were dipped into the slurry, and by removing them slowly, a uniform coating with a length of 1 cm length was prepared on the surface of the QFs. The QFs were dried under flowing nitrogen and finally cured for 40 min at 80℃, which facilitated the DMF to evaporate and ensured better adherence of the coating on the QFs (Figure 1B). The pNE modification were processed according to the procedure described in previous studies.36,37 First, NE was dissolved in a mixed solvent of tris buffer (10 mM, pH = 8.5); then, the coated QFs were immersed in the NE solution (2.0 g·mL-1) for 16 h. The fibers were preconditioned by being soaked in static methanol at room temperature for 15 min prior to use (Figure 1C). Animals and Exposure. Immature tilapias (Oreochromis mossambicus) were purchased from a local fishery. The tilapias were reared in aerated 80 L aquaria

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containing 40 L of dechlorinated tap water for 2 weeks before the experiment. Then, the fish were divided into two groups (n = 6 for each) and kept in 50 L tap water that was spiked with the stock solution (1000 µg·mL−1 for each pharmaceutical, in methanol) at 50.0 µg·L−1. One group was used to determine the sampling rates (after 3 d exposure) and another was used for monitoring. To keep the water concentration steady, the water was changed with fresh tap water and respiked with the initial amounts every 12 h. The monitoring period was 96 h and the sampling points were set as 4 h, 12 h, 24 h, 52 h and 96 h after the fish were exposed to the spiked water. The water quality was monitored daily (pH 6.2, dissolved oxygen 6.3 ± 0.3 ppm, and temperature 26.5 ± 1.1 °C). The lengths and weight of the fish were recorded (length 13.1 to 16.6 cm, median 14.7 cm; weight 36.0 to 49.0 g, median 40.7 g). All of the animal experiments were approved by the Animal Ethical and Welfare Committee of Sun Yat-sen University. In Vivo SPME. The procedure for in vivo sampling in fish dorsal-epaxial muscles is described in Figure S1; please consult our previous study for more details.11 The total sampling duration was controlled to be 10 min. The fibers were then rinsed with deionized water and dried with a Kimwipe tissue. Subsequently, the fibers were desorbed in 90 µL of methanol for 30 min at a vortex rate of 400 rpm, and 10 µL of fluoxetine-d5 deuterated standards solution (100 ng·mL−1) was added as an internal standard to calibrate the ionization efficiency for the HPLC-MS/MS analysis. Liquid Extraction (LE). The details of the LE of fish dorsal-epaxial muscle are described in the supporting information.

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Instrumental Analysis and Data Process. The details for the HPLC-MS/MS analysis are described in the Supporting Information. All of the data were processed with GraphPad Prism 5.

RESULTS AND DISCUSSION Characterization of the Custom-Made Fiber. The particle size could affect both the preparation of the coating and the extraction efficiency according to our previous study40. A smaller size would benefit the coating preparation and the extraction efficiency, but then the preparation of C18@GO@PDDA particles would be difficult. The employed 3.5 µm C18 particles were easily available and their size was suitable for both C18@GO@PDDA particles and the coating preparation. The scanning electron microscopic (SEM) images of the C18@GO and C18@GO@PDDA are shown in Figure 2A and 2B. Figure 2A shows that the C18 particles were completely encapsulated with GO sheets and that the GO sheets were stable and tight. Figure 2B showed that PDDA has been successfully assembled on the surface of the C18@GO particles. The surface of the particles was much smoother after the PDDA assembly. Moreover, an elemental analysis of the particles was also employed to confirm the assembly of GO sheets and the GO@PDDA assembly (Table 1). Comparing the C18 and C18@GO, the variation in the carbon and hydrogen contents can be attributed to the assembly of the GO. On the other hand, comparing the C18@GO and C18@GO@PDDA, the increases in the nitrogen content from 0.41% to 1.23% and the carbon content from 10.12% to 14.36% are ascribed to the PDDA assembled to

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the surface of C18@GO. Figure 2C shows the SEM images of the custom-made SPME fiber. The coating appears to possess a homogeneous surface, and the prepared particles are thickly and uniformly distributed both in the coating and on the surface of the coating. The X-ray photoelectron spectroscopy (XPS) analysis data confirms that there were C18@GO@PDDA particles on the coating surface by detecting the signal of C−N+ bonds (Figure 3A). The cross section of the fiber shown in Figure 2D indicates that the coating thickness was approximately 15 µm. To obtain the bio-interface and make the coating suitable for in vivo sampling, the surface of the coating was modified by the bioinspired pNE. As shown in Figure S2, the color of the coatings obviously changed. The color of the modified coating was brown while the unmodified coating was white. The surface modification was further confirmed by the XPS analysis, as the signal of C−OH bonds could be detected after modification (Figure 3B). Extraction Performance of the Custom-Made Fiber. The extraction kinetics of the surface modified and unmodified custom-made fibers were compared. As shown in Figure 4, the two types of fibers presented similar extraction kinetics for approximately all analytes. However, the equilibrium extraction amounts in the modified fibers were found to be higher than those in the unmodified fibers for all analytes (from 1.22 times to 3.32 times), even though the coating thicknesses were the same for these two types of fibers. These results indicated that this bioinspired surface modification would not hinder the mass transfer from the matrix to the coating, but instead it could enhance the loading capacity of the coating. The possible reason for

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the similar extraction kinetics was that the pNE layer was thin, smooth and hydrophilic. As for the increase in the loading capacity, the positive charges on the surface of the modified coating are suspected to affect the extraction affinity of the ionizable acid pharmaceuticals. The extraction efficiency of the custom-made coated fibers was compared with the PDMS fibers that were previously used for SPME sampling of pharmaceuticals in fish dorsal-epaxial muscles,41 fins,42 and bile.43 The preparation of the PDMS fibers was described in

previous studies as mounting a piece of PDMS tubing (length 1.0 cm,

O.D. 640 µm, I.D. 310 µm) on a stainless steel wire (diameter 480 µm).41-43 Furthermore, commercial polar PA fibers were also employed for comparison. A comparison of the extraction efficiency of the custom-made fibers, PDMS fibers and PA fibers was presented in Figure 5. The extraction efficiency of the custom-made fibers is much higher (8.0 to 81.7 times) than that of the PDMS fibers and also significantly higher (2.7 to 23.3 times) than that of PA fibers for all targeted analytes. All of the analytes were ionizable acid pharmaceuticals that can be ionized at physiological pH, so it is difficult to achieve enrichment factors in the PDMS fiber coatings for these compounds as high as for the nonpolar compounds. The enrichment factors of the acidic pharmaceuticals in the polar PA fiber coatings were also unsatisfactory in phosphate buffer saline (PBS) buffer solution. However, for our custom-made fibers, the good adsorption ability of C18 provide a strong extraction basis.23-26 The large delocalized π-electron system and various polar moieties of GO enhance the sorption affinity of the ionizable pharmaceuticals.30,31 The strong positive

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charges that the PDDA carries lead to the generation of strong electrostatic attractions to the ionizable acid pharmaceuticals.32-34 Moreover, the positive charges on the pNE modified surfaces may also improve the sorption affinity of the ionizable acidic pharmaceuticals.11 Thus, the extraction performance of novel custom-made fibers was much better than that of the PDMS fibers and PA fibers. In addition, the matrix-effect resistant of pNE modified and unmodified fibers was evaluated. MALDI-TOF MS analysis was employed to ensure that there were no macromolecules in the desorption solvent of both fibers exposed in blank fish muscle (Figure S3). The matrix effect of both fibers on the ionization of liquid chromatography-tandem mass spectrometry analysis was also evaluated. A series of standard solutions was added into the matrix-impacted and matrix-free solvents, and there was no significant ionization bias observed in the comparison (Table S1). Moreover, the pNE surface modification could provide a bioinspired interface so the fibers would not lead to any rejection reactions in living animals while sampling. The interfiber reproducibility and intrafiber reproducibility are presented in Table 2, which were determined by extraction in PBS solutions. The custom-made coating possessed satisfactory stability with RSDs of intrafiber reproducibility ranging from 1.60% to 10.3% for six sampling-desorption cycles, and the RSDs of interfiber reproducibility ranged from 2.61% to 11.5%. The good intrafiber reproducibility demonstrated that the fiber was sufficiently stable for repeated uses. The interfiber reproducibility was also satisfactory. The fibers can be well regenerated by immersing the coating in methanol for 30 minutes. In the in vivo monitoring experiment, the

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fibers could be repeatedly used at least 30 times without a decrease in the extraction performance or defects in the coating structure. In Vivo Monitoring in Fish. In this study, a sampling-rate (SPME-SR) calibration method41 was adopted to quantify the concentrations of the ten targeted acidic pharmaceuticals in the dorsal-epaxial muscles of living fish. The in vivo sampling duration was as short as 10 min, and the sensitivities were satisfactory (Table 2). The limit of quantitation values (LOQ), linear range and the regression coefficients (R2) in spiked fish dorsal-epaxial muscle homogenate are also presented (Table 2). The custom-made fibers were demonstrated to be capable of direct in vivo determination of pharmaceuticals in complex biological sample matrices. The sampling rates were first recorded in another group of fish exposed to the pharmaceuticals at the same concentration as the monitoring group (Table S2). Based on the sampling rates, the concentrations that were determined with in vivo SPME and those with LE were compared. The mean concentrations determined with both methods were close to each other, which demonstrates the excellent accuracy of in vivo SPME (Figure 6). The custom-made SPME fibers were further applied to the in vivo monitoring of the ten acid pharmaceuticals in living fish. The sampling-rate calibration method was used for quantification, and all of the analytes were successfully monitored in the living fish during the 96 h monitoring period (Figure 7). The successful in vivo monitoring experiment clearly demonstrated that the custom-made fibers were feasible for possible long-term continuous in vivo pharmaceuticals monitoring. The possible effects of this coated material and the fiber on fish need to be evaluated in

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further long-term studies. Application Considerations. In recent years, acidic pharmaceuticals have been recognized as emerging contaminants owing into their physiological activities, wide usage, and constant discharge to the environment.44-46 Acidic pharmaceuticals have been found in aquatic environments such as surface water, groundwater, and even drinking water at concentrations ranging from parts-per-trillion to parts-per-billion levels.47-49 Bioconcentration factors and pharmacokinetics are important for characterizing the bioaccumulative and metabolic properties of the acidic pharmaceuticals in environment. Long-term time-weighted in vivo monitoring in living animals is significant for bioconcentration factors and pharmacokinetics studies.5,50 In the present study, we prepared novel custom-made SPME fibers for high-efficiency extraction of acidic pharmaceuticals in living fish. The concentrations of acidic pharmaceuticals in freely swimming fish were monitored over a period of 96 hours. The in vivo monitoring experiment presented a potential use for the custom-made fibers in

in

vivo

SPME

for bioconcentration factors and

pharmacokinetics studies of acidic pharmaceuticals in living fish and other animals. Moreover, besides the laboratory experiments, the established approach could also be utilized to monitor the concentrations of acidic pharmaceuticals in rare or endangered wild animals. Then, it will be possible to conduct studies such as bioconcentration factor studies and pharmacokinetics studies on these animals, which will be helpful for improving the understanding of acidic pharmaceuticals behaviors including their translocation, bioaccumulation and metabolism in the environment and wildlife.

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CONCLUSIONS In summary, the novel custom-made SPME fibers based on PDDA assembled GO coated C18 composite particles and the surface modification with bioinspired pNE were proposed for in vivo pharmaceuticals monitoring. The custom-made fibers were demonstrated to be much more efficient then the previously used PDMS and PA fibers. The fibers were stable for repeated sampling-desorption cycles and exhibited good interfiber reproducibility and matrix-effect resistance. Due to the direct sampling of acidic pharmaceuticals in fish dorsal-epaxial muscle, satisfactory sensitivity was achieved and the accuracy was also verified by the comparison with LE. The application of in vivo monitoring of acidic pharmaceuticals in fish demonstrated that the custom-made fibers were feasible for possible long-term continuous in vivo pharmaceuticals monitoring. In addition, it also revealed a potential use for in vivo SPME

with

the

custom-made

fibers

for

bioconcentration

factors

and

pharmacokinetics studies of acidic pharmaceuticals in living fish and other animals, including rare or endangered animals.

ASSOCIATED CONTENT Supporting Information HPLC-MS/MS analytical parameters, LE method, deployment of SPME fiber in fish muscle, image of modified and unmodified fibers, MOLDI-TOF MS analysis results, comparison of LE and in vivo SPME with custom-made fibers, regression slopes of

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curves derived from the matrix-free and matrix-impacted solutions, and sampling rates of targeted acidic pharmaceuticals. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author *Tel./Fax: +86-20-84110845. E-mail: [email protected]. *Tel./Fax: +86-20-84110845. E-mail: [email protected]. Notes The authors declare no competing financial interest.

Acknowledgements We acknowledge financial support from the projects of National Natural Science Foundation of China (21377172, 21225731, 21477166, 21527813), and the NSF of Guangdong Province (S2013030013474)

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Figure Captions Figure. 1. Flow diagram of the preparation and application of the novel SPME fiber. (A) Preparation of the particles (a. C18, b. C18@GO, and c. C18@GO@PDDA). (B) Preparation of the custom-made fiber with PANI by the dip-coating method. (C) Bioinspired modification by the oxidation polymerization of NE. (D) In vivo sampling in fish dorsal-epaxial muscle with the custom-made fiber.

Figure. 2. SEM images of a C18@GO particle (A), a C18@GO@PDDA particle (B), the custom-made fiber (C) and its cross-section (D).

Figure. 3. Peak fitting of C 1s XPS spectra of the an unmodified fiber (A) and a pNE modified fiber (B).

Figure. 4. Extraction time profiles of ten acidic pharmaceuticals with unmodified fibers (A) and pNE modified fibers (B). The concentration of each analyte in PBS buffer (pH = 7.4) was 10 ng·mL−1, and the agitation rate was 400 rpm. The extractions were conducted at room temperature. The error bars represented the standard deviations (n = 6).

Figure. 5. Comparison of the extraction efficiencies between the novel fibers, PDMS fibers and PA fibers. The concentration of each analyte in PBS buffer (pH = 7.4) was 10 ng·mL−1; the agitation rate was 400 rpm, and the extraction time was 10 min. The

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error bars represent the standard deviations (n = 6).

Figure. 6. Mean concentrations of ten acid pharmaceuticals in fish dorsal-epaxial muscle with LE and in vivo SPME; the error bars represent the standard deviations (n = 6).

Figure. 7. In vivo monitoring of ten acidic pharmaceuticals in fish. The error bars represent the standard deviations (n=6).

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Figure 1.

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Figure 2.

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Figure 3.

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Figure 4.

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Figure 5.

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Figure 6.

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Figure. 7.

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Table 1. Elemental analysis data of C18, C18@GO and C18@GO@ PDDA particles. Particles

C (%)

H (%)

N (%)

C18

9.78

2.20

0

C18@GO

10.12

1.76

0.41

C18@GO@PDDA

14.36

1.88

1.23

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Table 2. Intra-fiber and inter-fiber reproducibility (%) of novel custom-made fiber (n=6), LOD (S/N=3, ng·g-1), and LOQ (S/N=10, ng·g-1) of in vivo SPME in fish dorsal-epaxial muscle. A linear range (ng·g-1) was achieved in spiked fish dorsal-epaxial muscle homogenate and R2 values are also presented. Analytes

Intrafiber

Interfiber

LOD

LOQ

Linear range

R2

CAR

8.76

8.87

0.24

0.08

1-5000

0.9960

FLU

6.31

10.7

0.22

0.73

1-5000

0.9878

MEF

6.29

3.65

0.62

2.06

5-5000

0.9862

FLUF

9.63

11.5

0.13

0.44

1-5000

0.9828

FLUR

2.44

7.68

8.44

28.1

30-5000

0.9868

KET

9.53

8.22

2.45

8.16

10-5000

0.9999

TOL

1.60

9.77

0.48

1.61

5-5000

0.9975

GEM

6.43

2.61

0.39

1.29

5-5000

0.9984

NAP

2.04

5.90

7.56

25.2

30-5000

0.9998

IBU

10.3

7.77

3.26

10.9

20-5000

0.9982

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For TOC only

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