Magnetic Solid-Phase Extraction Based on Modified ...

BATC #938148, VOL 0, ISS 0

Magnetic Solid-Phase Extraction Based on Modified Ferum Oxides for Enrichment, Preconcentration, and Isolation of Pesticides and Selected Pollutants WAN AINI WAN IBRAHIM, HAMID RASHIDI NODEH, HASSAN Y. ABOUL-ENEIN, and MOHD MARSIN SANAGI

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Critical Reviews in Analytical Chemistry (2015) 0, 1–18 Copyright © Taylor and Francis Group, LLC ISSN: 1040-8347 print / 1547-6510 online DOI: 10.1080/10408347.2014.938148

Magnetic Solid-Phase Extraction Based on Modified Ferum Oxides for Enrichment, Preconcentration, and Isolation of Pesticides and Selected Pollutants WAN AINI WAN IBRAHIM1,2, HAMID RASHIDI NODEH1, HASSAN Y. ABOUL-ENEIN3, 5 and MOHD MARSIN SANAGI2,4 1

Separation Science and Technology Group (SepSTec), Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, Johor, Malaysia 2 Nanotechnology Research Alliance, Universiti Teknologi Malaysia, Johor, Malaysia 3 National Research Centre, Department of Pharmaceutical and Medicinal Chemistry, Pharmaceutical and Drug Industries Research 10 Division, Cairo, Egypt 4 Ibnu Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, Johor, Malaysia

Recently, a simple, rapid, high-efficiency, selective, and sensitive method for isolation, preconcentration, and enrichment of analytes has been developed. This new method of sample handling is based on ferum oxides as magnetic nanoparticles (MNPs) and has been used for magnetic solid-phase extraction (MSPE) of various analytes from various matrices. This review focuses on the applications 15 of modified ferum oxides, especially modified Fe3O4 MNPs, as MSPE adsorbent for pesticide isolation from various matrices. Further perspectives on MSPE based on modified Fe3O4 for inorganic metal ions, organic compounds, and biological species from water samples are also presented. Ferum(III) oxide MNPs (Fe2O3) are also highlighted. Keywords: Biological species, inorganic, magnetic nanoparticles, magnetic solid phase extraction, modified Fe3O4, organic, pesticides

Introduction 20 Pesticides are widely used in agriculture to control insects,

pests, weeds, and fungi, to increase the quality of agricultural products and food supply, improve crop yield, and protect human health (Xiong et al., 2012; Zhao et al., 2013a). Pesticides are a large class of organic pollutants and can be classi25 fied as organophosphorus pesticides (OPPs), organochlorine pesticides (OCPs), herbicides, carbamates, fungicides, and pyrethroids, among others. OPPs are applied widely due to their excellent effectiveness in pest and weed control (Li et al., 2013a). However, harmful residues of OPPs remain in 30 the environment and cause water pollution that poses

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Address correspondence to Wan Aini Wan Ibrahim, Separation Science and Technology Group (SepSTec), Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia. E-mail: [email protected]; [email protected], or to Hassan Y. Aboul-Enein, National Research Centre, Department of Pharmaceutical and Medicinal Chemistry, Pharmaceutical and Drug Industries Research Division, Dokki, 12311 Cairo, Egypt. Email: [email protected] Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/batc.

potential risk to human health (Bagheri et al., 2010; Wang et al., 2014a). In addition, some of OPPs have been revealed to be carcinogens and several of them have been shown to be mutagens (Saleh, 1980). Also OPPs exhibit nerve agent behavior due to inhibition of the acetyl cholinesterase enzyme (Sultatos, 1994). OCPs, which include lindane and heptachlor, have been used widely since the 1940s and 1950s to control phytophagous insects and kill termites and soil insects (McManus et al., 2013). Eight different isomers of lindane and two heptachlor isomers were classified in highly toxic chemicals as persistent organic pollutants (POPs) (McManus et al., 2013). Maximum residual level (MRLs) in drinking water were set at 0.03 ng mL¡1 for heptachlor and its epoxide and 0.1 ng mL¡1 for lindane and its isomers according to the European Union Standard Commission 98/83/EC (European Community, 1998). OCPs were found in fresh and pasteurized milk (Kampire et al., 2011). Recently, pyrethroid pesticides have been applied instead of OCPs to kill insect pests in urban areas and to protect fruit in rural areas because of their low toxicity in comparison to OCPs (Jiang et al., 2013a). Herbicides are used to obtain good quality and high yield of agricultural products. Herbicides are highly soluble in water and easily enter soil and environmental water, and due to their toxicity they can cause health problems. Sulfonylurea herbicides are used for agronomic crops; although they are

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used at low concentration their phytotoxicity is high and human risk is expected (He et al., 2012). Triazine herbicides are used to remove soil pests and are easily absorbed in seedling weeds; due to their high toxicity they should be monitored in soil and environmental water samples. Carbamates are biological active and low bioaccumulation subclasses of pesticides that are relatively harmful for humans (Sun et al., 2013). Fungicides are chemical substances used in agriculture for plant disease control and are directly sprayed on grapes and leaves to avoid fungal attack (Li et al., 2013b; Montes et al., 2009). Triazole fungicides are applied in agriculture; due to their high toxicity, they have harmful effects on humans and create a major challenge in environmental protection (Wang et al., 2012b). Neonicotinoid pesticides are a new group of insecticides due to their active ingredients and pose serious risks to environmental and human health (Ma et al., 2013; Wang et al., 2012a). The MRL concentration range is 0.01–1.5 mg kg¡1 for human health (for agriculture chemical residues in food, according to the Japanese standard) (Ma et al., 2013). Pesticides can remain in plants, vegetables, and fruits during growth and post-harvest treatment (Hayward et al., 2013). Pesticides are large organic contaminates with different polarities; they are freely mobile to environmental water and easily absorbed in soil and by root transfer to leaves, plants, and vegetables. A variety of pesticides has been reported in tea (Deng et al., 2014), vegetables (Jiang et al., 2013a; Mukdasai et al., 2014), cold-pressed vegetable oil (Zhao et al., 2013b), fruit juice (Li et al., 2013b), milk (Kampire et al., 2011), and even honey (Du et al., 2013). Maximum allowance of pesticides in drinking water was set by the European Community Directive 2000/60/EC (2000) at 0.1 ng mL¡1 for single pesticides and 0.5 ng mL¡1 for total pesticides. For the mentioned reasons pesticide residues should be monitored in environmental water, plants, foods, and biologically complex samples. In order to determine pesticides at trace or ultra-trace level in complex samples and water samples, special techniques are needed for preconcentration, enrichment, and cleanup prior to instrument analysis. The most common methods are liquid-liquid extraction (LLE), which consumes a high level of unfriendly organic solvents (Ghiasvand et al., 2005; Igarashi et al., 1992) , liquid-liquid microextraction (LLME) (Liang et al., 2009), dispersive liquid-liquid microextraction based on solidification (DLLM-SFO) (Sanagi et al., 2012), dispersive liquid-liquid microextraction-solid phase extraction (DLLM-mSPE) ultra preconcentration (Fattahi et al., 2007), and solid-phase microextraction (SPME) (Wan Ibrahim et al., 2010). SPME is a solvent-free, fast, portable, and easy-to-use method. However, SPME also has some drawbacks. The fiber is fragile and has a limited lifetime, and sample carryover is difficult (Ahmadi et al., 2006; Bagheri et al., 2010). To overcome the limitations of SPME, stir bar sorptive extraction (SBSE) was developed by Baltussen et al. (1999). It is a solventless sample preparation method (when used with thermal desorption) for the extraction and enrichment of organic compounds from aqueous matrices and can be used with liquid desorption mode (Wan Ibrahim et al., 2011a, 2011b). The solid-phase

W. A. Wan Ibrahim et al. extraction (SPE) technique was successfully applied for OPP preconcentration from water samples (Wan Ibrahim et al., 2012). SPE is an ideal method for enrichment and preconcentration because it is simple, flexible, and easy to automate (Mashhadizadeh and Karami, 2011; Zhang et al., 2012a). The advantages of SPE include stability in a wide pH range, reactiveness (Wan Ibrahim et al., 2014), significant recovery, short extraction time, high enrichment factor, low cost, and less consumption of organic solvent (Cai et al., 2003). Although there are many benefits to using conventional SPE methods, they are tedious and time consuming and require a high volume of sample loading. Also, low breakthrough volume was observed for polar compounds (Buszewski and Szultka, 2012). To overcome the problem of conventional SPE limitations, magnetic nanoparticles (MNPs) were applied as a SPE sorbent in batch mode prior to extraction pretreatment followed by quick extraction using an external magnet. This method is called magnetic solid ríkova and Safa  rík, 1999). phase extraction (MSPE) (Safa Some potential benefits of MSPE are short time extraction, high enrichment, high extraction efficiency, ease and convenience of use, as well as the fact that MSPE can be used directly in crude samples without the need for centrifugation and filtration (Sun et al., 2010; Ye et al., 2014).

Magnetic Solid-phase Extraction Applications Separation technology employing magnetic materials dates back to the 1990s and before, used for separation in biological samples and environmental samples (Ennis and Wisdom,  ríkova and Safa  rík, 1999). 1991; Itak et al., 1993; Safa Recently, there has been enormous interest in the use of MNPs in separation, extraction, and cleanup of environmental contaminants. Few elements in nature have magnetic properties, including iron, cobalt, and nickel, so their nanoparticles and derivative compounds are magnetized. Established methods of magnetic nanosized powder preparation include co-precipitation (Amaranatha Reddy et al., 2012), microwave assisted (Chen et al., 2012), sol-gel (Sivakumar et al., 2012), hydrolysis (Rostamizadeh et al., 2012), hydrothermal (G€ oz€ uak et al., 2009), and flame spray (Strobel and Pratsinis, 2009). Among the various kinds of MNPs, Fe3O4 is the most common since it has high surface area, quite small particles, excellent paramagnetic properties, water dispersivity, stability, and less toxicity and is easy to synthesize and functionalize. MNPs have been widely used in water purification (Ambashta and Sillanp€a€a, 2010) as well as playing a main role in the extraction of metal ions, organic contaminants, and pesticide residues (Taghizadeh et al., 2014; Xiong et al., 2012). Low extraction efficiency, instability in acidic environment, aggregation, and easy oxidation of MNPs limit its use. To overcome these limitations, MNPs have been functionalized, modified, and improved using different kinds of organic and inorganic materials, including silica, polymers, imprinted molecules, hemi-micelles, admicelles, ionic liquids, alkoxides, membranes, members of the carbon family, proteins, and enzymes. Functionalized MNPs have been applied

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Magnetic SPE Based on Modified Ferum Oxides as MSPE sorbents in batch mode for extraction of metal ions, organic compounds, and biological substances. Improved MSPE sorbents show high stability, compatibility in different 175 environments, selectivity, and reusability. Figure 1 is a schematic illustration of MNP modification and its application in MSPE.

Magnetic Solid-phase Extraction of Pesticides Sample preparation of pesticides due to their high toxicity at 180 trace levels is required. Preconcentration is a critical step in

the analytical process. MSPE based on MNPs is a suitable candidate for this purpose. To improve the stability, sensitivity, compatibility, extraction efficiency, and selectivity, MNPs have been 185 modified with polymers, alkoxides, members of the carbon family, and mixed micelles, among others. The proposed new MSPE technique is fast, easy, and low cost and offers high extraction efficiency, high breakthrough volume, and high enrichment factor. Different kinds of modified MSPE

FIG. 1. Schematic illustration of MSPE process.

3 have been successfully applied for pesticide preconcentration and enrichment. OPPs, which include diazinon and fenitrothion, were determined using the MSPE method based on MNPs modified with core shell silica and grafted with C18 (Fe3O4@SiO2–C18). The new product showed a low limit of detection (LOD; 0.014–0.019 ng mL¡1) for OPP extraction in water samples. OPP isolation was studied in different pH ranges; at low pH the N atoms of OPPs are protonated and in alkaline pH, the OPPs undergo hydrolysis, so extraction recovery was decreased (Maddah and Shamsi, 2012). MSPE based on Fe3O4@SiO2–C18 was applied successfully in the complex matrix of vegetable samples for pyrethroid preconcentration. The low LOD (0.03 ng g¡1) achieved makes the proposed method suitable for complex sample analysis (Jiang et al., 2013a). Carbon-coated MNPs (C/Fe3O4) were synthesized using hydrothermal reaction and used as MSPE sorbent for OPP extraction from aquatic samples. Due to hydrophobicity of the prepared adsorbent, the nonpolar OPPs generated high p-p interaction in the benzene ring (LOD D 4.3 pg mL¡1),

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and mid-polar malathion without aromatic ring possessed less electrostatic interaction (LOD D 47.4 pg mL¡1). Good recoveries were obtained for all OPPs (82–101%). The proposed method provides less selectivity when considering the high-performance liquid chromatography-ultraviolet (HPLC-UV) chromatogram (figure not shown) due to the appearance of many extra peaks (Heidari and Razmi, 2012). The QuEChERS (quick, easy, cheap, effective, rugged, and safe) method was studied using MNPs modified by graphitized carbon black and primary secondary amine (GCB/PSA/Fe3O4; Zheng et al., 2013). The proposed MSPE sorbent was synthesized using the hydrothermal method and applied in pesticide residual analysis in vegetables. The magnetic sorbent was fabricated by a simple and less time-consuming method for the cleanup of 10 different OPPs, OCPs, fungicides, and pyrethroid pesticide residuals in cucumber, cabbage, tomato, and gourd samples. The recovery obtained (76–125%) demonstrated that the prepared adsorbent is suitable for complex matrix treatment. The MSPE method was sensitive to nonpolar components since a detection limit of 0.39 ng g¡1 was obtained for nonpolar bifenthrin (log Kow 5.6) and 8.6 ng g¡1 for phenthoate (log Kow » 3.0). This behavior is probably related to the p-p electron of benzene rings in the analytes (Zheng et al., 2013). OPP and OCP residues in tea samples were isolated using a laboratory-made MSPE sorbent. Amine-functionalized Fe3O4 and multiwall carbon nanotube (MWCNT) nanocomposite was prepared and applied as a rapid isolation adsorbent. Due to both hydrophobic and hydrophilic properties of the prepared adsorbent, polar and nonpolar analytes were extracted with low LOD (20–80 ng mL¡1) and good recovery (72.5–109%) (Deng et al., 2014). Fifteen OPP were analyzed rapidly using MSPE based on Fe3O4-MWCNTs. The gas chromatography with nitrogen phosphorus detector (GCNPD) chromatogram (figure not shown) showed less interference and high selectivity of the proposed adsorbent (Gonz alez-Curbelo et al., 2013). Carbon-based adsorbents have been shown to have high adsorption capacity (Karimi et al., 2014; Lei et al., 2014; Zhang et al., 2013). Graphene has been considered an ideal carbon-based adsorbent for pesticides, since it has a rich aromatic ring. MSPE based on graphene (G-Fe3O4) nanocomposite was prepared and used for imide fungicide treatment in water and grape juice samples. Graphene-based Fe3O4 (GFe3O4) provided an easy, fast, and high-extraction MSPE method. Graphene possesses a large p-p electron, high surface area, and hydrophobic properties and shows excessive adsorption behavior to benzenoid compounds. The obtained GC-MS chromatogram (Figure 2) contains high peaks, demonstrating that the synthesized adsorbent is highly sensitive to fungicides (Li et al., 2013d). G-Fe3O4 has also been used as a triazine herbicide adsorbent prior to HPLC analysis. It was synthesized using the solvothermal.method. The MSPE performance was considered under optimum conditions with an LOD in the range of 0.02–0.04 ng mL¡1. The pH studies showed that the triazine herbicides were stable in the pH range 6–8. Triazine herbicides were successfully adsorbed on graphene sheets due to the p-p electrons interaction (Zhao et al., 2011a).

W. A. Wan Ibrahim et al.

FIG. 2. GC-MS chromatograms: (A) unspiked and (B) spiked with 500 ng L¡1 of vinclozolin and 2500 ng L¡1 each of procymidone, folpet, and ditalimfos in reservoir water sample. (Li et al., 2013d). © The Japanese Society for Analytical Chemistry. Reproduced by permission of The Japanese Society for Analytical Chemistry. Permission to reuse must be obtained from the rightsholder.

Carbamate pesticides were preconcentrated using GFe3O4 from water samples. The prepared nanocomposite provides potential benefits that include high surface area, water solubility, high diffusion, excellent adsorption capacity, and quick extraction by an external magnet. All five carbamates studied contain aromatic ring and amide group in the polar and mid-polar range (log Kow 1.7–2.8). Sufficient p-electrons in the aromatic ring of the carbamates increase the affinity of graphene to adsorb analytes from large volumes of water samples and led to a high enrichment factor (Wu et al., 2011). Fe3O4@SiO2-G was used for extraction of pyrethroid pesticides from orange and lettuce. The main variables were optimized and the method exhibited LODs in the range of 0.01–0.02 ng g¡1, acceptable RSD (< 10.65%), and good recovery (90.1–103.75%). Pesticide recovery, R, was calculated using the formula R D CCos £ VVos ; where C0 and V0 are the analyte concentration and volume in desorption solvent,

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respectively, and Cs and Vs are the initial concentration and volume before extraction, respectively. Extraction recovery decreased at high pH due to pyrethroid hydrolysis in alkaline pH. Graphene with hydrophobic properties show high peak area for highly nonpolar pyrethroid (bifenthrin, log Kow > 6.0; Figure 3) (Hou et al., 2013). Pyrethroid pesticide analysis has received attention recently because of their low toxicity in comparison to OCPs. MNPs synthesized in a microbowl shape and coated by polyaniline polymer (Fe3O4/C/PANI microbowls) were applied to the determination of five pyrethroids. Microbowls increased reusability and polyaniline provide a stable, tunable, and sensitive adsorbent due to its p-electrons. Some advantages of the proposed method are rapid operation, small amounts of adsorbent (8 mg), and frequent reuse (10£) without significant changes in recovery (Figure 4) (Wang et al., 2014b). A new MSPE technique based on low-density magnetic fluid was studied. The magnetic fluid included Fe3O4 nanoparticles and oil as a carrier. Fe3O4 was coated by oleic acid dispersed on oil to prepare magnetic fluids for isolation of OCPs from water. Due to the use of a small amount of sorbent, a high enrichment factor was obtained. The proposed method successfully solved dispersive liquid-liquid microextraction (DLLME) limitations but totally depends on ionic strength. As can be seen from the chromatogram (Figure 5), 10 OCPs analytes were extracted with high recovery (70.1– 98.6%) (Shen et al., 2013). Three OPPs were analyzed using fast new dispersive microextraction method based on “magnetic water.” Water used as an MNP coating agent played the hydrophilic role in extraction; it is more environmentally friendly than organic agents. The hydrophilic adsorbent extracted a sufficient amount of polar methamidophos, omethoate, and monocrotophos

FIG. 3. GC-MS chromatograms of (A) spiked pyrethroid at 50 ng g¡1 and (B) unspiked blank orange sample. (Hou et al., 2013). © Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Reproduced by permission of Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Permission to reuse must be obtained from the rightsholder.

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FIG. 4. UFLC-UV chromatograms of (a) first extraction and (b) after 10£ extractions of pyrethroid pesticides in reusability study of Fe3O4/C/PANI MNPs sorbent (Wang et al., 2014b). © Elsevier. Reproduced by permission of Elsevier. Permission to reuse must be obtained from the rightsholder.

(log Kow < 0.5 for the three OPPs) from complex oil samples (Zhao et al., 2013b). Pillararene-modified MNPs (Fe3O4/CP5A) were used as pesticides adsorbent in juice and wine samples. The magnetic adsorbent was grafted by the amine group in Fe3O4-NH2 and the carboxylic group in CP5A. The adsorbent contain both hydrophilic and hydrophobic properties, thus the strong electrostatic interaction with polar and nonpolar pesticides. Clean chromatograms obtained (Figure 6) showed that the synthesized Fe3O4/CP5A MNP adsorbent is suitable for complex matrix analysis with less interference (Tian et al., 2013). New materials based on magnetic polypyrrole (Fe3O4 @polypyrrole) nanowires were synthesized in 20 nm diameter size. The proposed MSPE sorbent was used for preconcentration of 11 pesticides, including OPPs, OCPs, pyrethroid, and fungicides. Electrostatic interaction is the major factor of the adsorption mechanism (Zhao et al., 2013a). The method was used for determination of 11 pesticides in beverage teas, juices, and environmental water samples using a combination of gas chromatography/mass spectrometry (GC/MS) with Fe3O4@polypyrrole MSPE. The proposed method exhibited low LOD (0.09–0.29 mg L¡1), good recovery (76–129%), and acceptable reproducibility (RSD < 16%), which was measured using the interday and intraday process. Table 1 shows more references for the MSPE method based on modified Fe3O4 MNPs as adsorbent for pesticide isolation, published in 2012–2013. As can be seen from the table, the determination of herbicides using two different materials based on Fe3O4-graphene and Fe3O4@DDAC@SiO2, showed that the graphene-based adsorbent was better (lower LODs and better percentage recoveries) and showed much higher enrichment factors (3399–4002) due to strong p-p interaction between large p-stacking of graphene and the aromatic ring in herbicides. For neonicotinoids, the G-Fe3O4 adsorbent shows lower LODs and 30 times higher enrichment factors than Fe3O4@SiO2-G.

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FIG. 5. GC-ECD chromatogram of 1 mg L¡1of organochlorine pesticide extraction in spiked river water using magnetic fluid adsorbent (Shen et al., 2013). © Elsevier. Reproduced by permission of Elsevier. Permission to reuse must be obtained from the rightsholder.

Cobalt ferrite deposited on carbon nanotubes (CoFe2O4-

360 CNTs) provided sufficient OCP isolation from honey and tea

samples. Rich delocalized p-electrons in CNTs cause strong p-p interaction with hydrophobic OCPs (log Kow > 4.5 for all), which increased selectivity. A clear chromatogram obtained (figure not shown) confirmed this statement (Du 365 et al., 2013).

Magnetic Solid-phase Extraction of Metal Ions Removal of Pb(II) from water used Fe3O4@SiO2–xanthan gum (Peng et al., 2014) with good surface area (137.5 m2 g¡1) and fast adsorption. However, it showed less adsorption 370 capacity (21 mg g¡1) for Pb(II) than that obtained with g-Fe2O3@PLCs (71 mg g¡1). Removal of chromium from water used graphene oxide magnetic cyclodextrin-chitosan (Fe3O4-GO/CD/chitosan) (Li et al., 2013b). The proposed

modified magnetic adsorbent showed significant adsorption capacity (445.6 m2 g¡1) in comparison with pure graphene oxide (342.3 m2 g¡1). Silica shell Fe3O4 modified with amidoxime showed benefits as a potential adsorptive of uranium(VI) from water samples with acceptable maximum sorption capacity (0.441 mmol g¡1) (Zhao et al., 2014). Simultaneous sorption of arsenic and chromium was achieved on magnetic adsorbent based on phosphonium-silane ionic liquid. In this case MNPs were attached covalently on a cationic ligand (Badruddoza et al., 2013). In this case the adsorption capacity obtained was 50.5 m2 g¡1 for As(V) and 35.2 m2 g¡1 for Cr(VI). The value obtained for the latter is much lower than the value obtained using Fe3O4-GO/CD/chitosan adsorption, i.e., 445.6 m2 g¡1 for chromium. Modified MNPs as an adsorbent have potential benefits that include chemical stability, thermal stability, unique properties, and selective behavior in metal preconcentration.

FIG. 6. HPLC chromatograms for pesticides at two spiked levels from (A) wine and (B) juice samples. Level 1 is 0.5 mg mL¡1 and level 2 is 1.0 mg mL¡1 (Tian et al., 2013). © The Royal Society of Chemistry. Reproduced by permission of The Royal Society of Chemistry. Permission to reuse must be obtained from the rightsholder.

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G-Fe3O4 G-Fe3O4 Fe3O4@SiO2-G Fe3O4@SiO2-G C18-Fe3O4@SiO2 Fe3O4@TiO2 Fe3O4@DDAC@SiO2 Fe3O4/PSDVB

2013 2013 2013 2013 2013 2013 2012 2012

2012 G-Fe3O4 2012 Fe3O4@SiO2-C18

2012 Fe3O4@poly styrene 2012 G-Fe3O4

MSPE sorbent

Year

Pyrethroid pesticides Myclobutanil, tebuconazole, hexaconazole Neonicotinoid insecticides Carbamates & OPPs

Chloroacetanilide herbicides Herbicides Neonicotinoid pesticides 14 OPPs & fungicides OPPs OPPs Herbicides Fenitrothion

Pesticides

Water Water

Water Water

Water Green tea & water Pear & tomato Tomato & rape Water Water Water Biological samples

Sample matrix 80.7–105.3 80.2–105.3 93.1–107.4 83.2–110.3 — 88.5–96.7 80.4–107.1 97.2–100.0

0.02–0.05 ng mL¡1 0.01–0.03 ng mL¡1 0.08–0.15 ng g¡1 0.005–0.030 ng g¡1 1.8–5.0 ng g¡1 26–30 ng mL¡1 0.078–0.10 ng mL¡1 0.5 ng mL¡1

649–1078 3399–4002 160–195 — — 1000 1200–1410 —

EF

GC-ECD GC-FID HPLC-DAD GC-MS GC-MS HPLC-UV HPLC-UV UV-Vis

Detector

0.004–0.01 ng mL¡1 86–110 3325–4644 UFLC-UV 1–8 ng mL¡1 70.2–110.2 1015 GC-MS

0.01–0.02 ng mL¡1 78.0–96.5 500 UFLC-UV 0.005–0.01 ng mL¡1 86.0–102.0 3600–5824 UFLC-UV

%R

LOD

Wang et al., 2012a Xiong et al., 2012

Li et al., 2013c Bai et al., 2013 Ma et al., 2013 Wang et al., 2014a Xie et al., 2013 Li et al., 2013a He et al., 2012 Eskandari and Naderi-Darehshori, 2012 Yu et al., 2012 Wang et al., 2012b

Ref.

TABLE 1. Some MSPE applications based on modified Fe3O4 for pesticide isolation from various matrices from 2012–2013 evaluated by limit of detection (LOD), extraction recovery (% R), enrichment factor (EF), and the detector used

Magnetic SPE Based on Modified Ferum Oxides 7

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Modified MNPs have been successfully applied as MSPE sorbents for preconcentration of metal ions and have gained interest in the past few years. Trace amounts of metals were enriched by synthesized magnetic Fe3O4@SiO2@polyanilinegraphene oxide (Fe3O4@SiO2@MPANI-GO) nanocomposite with the MSPE method (Su et al., 2014). Extracted ultra-trace elements were detected using inductive coupled plasma-mass spectrometry (ICP-MS) after magnetic cleanup and preconcentration. Amounts of metal ions detected were between 0.04 and 1.40 ng L¡1. Fe3O4@SiO2@MPANI-GO advantages are simplicity, fast operation, selectivity, sensitivity, and high enrichment and that it is suitable for trace element extraction in complex samples (Su et al., 2014). Fe3O4@SiO2@MPANIGO adsorption behavior totally changes in different pH values due to increase in OH¡ at high pH, which causes repulsion with negative charge of ions as well as efficiency reduction (Su et al., 2014). Graphene (G) is used as new sorbent in analytical processes. It has high surface area and chemical stability. It has shown low recovery in metal ion preconcentration, which might be related to lack of functional group(s) on the graphene surface. Otherwise, G has great delocalized p-p electrons, which improve the p stacking and electrostatic interaction. Graphene oxide (GO) and modified GO have shown many applications in metal ion treatment because of their variety of different functional groups. GO is rich in –OH, epoxy, carboxyl, and carbonyl groups, which simply make stable coordinates with metal ions (Sitko et al., 2013; Su et al., 2014). In addition, GO possesses delocalized p-p bonding to help electrostatic interaction between metal ions and adsorbent (Chandra et al., 2010; Sitko et al., 2013; Su et al., 2014). Efficiency of GO for Cu(II) sorption was 10fold higher than that of active carbon. Polyaniline adsorbent helped to increase electrostatic interaction with rich p-p electrons (Su et al., 2014). Single-user GO or polyaniline in the SPE method is time consuming and tedious and requires ultra-speed centrifuges and filtration in batch mode. To overcome this problem, magnetic Fe3O4 nanoparticles were dispersed on GO-based material and were easily extracted using an external magnet. Magnetic Fe3O4 nanoparticles were modified using silica followed by functionalization with amine (Fe3O4@SiO2– NH2) followed by simple bonding with quercetin (Fe3O4@SiO2–NH2–quercetin). The novel prepared material was applied for uranyl ion preconcentration from water. The rapid and convenient method showed good recovery (85.7– 93.3%) and suitable adsorption capacity (13.33 mg g¡1) for uranyl ions (Sadeghi et al., 2012). Preconcentration of lead (Jiang et al., 2012), Cr(III), and Cr(VI) (Jiang et al., 2013b) was carried out using zinconimmobilized on silica shell Fe3O4 in the MSPE method. Different functional groups and delocalized electrons on zincon can cause an increase in the covalent and electrostatic interaction. Fe3O4@SiO2–zincon shows great adsorption capability, low LOD (10–10.6 ng L¡1), fast extraction, and convenience (Jiang et al., 2012; Jiang et al., 2013b). Magnetic iron oxide NPs have a large surface-to-volume ratio and therefore possess high surface energies. Consequently, they tend to aggregate so as to minimize surface

W. A. Wan Ibrahim et al. energies. Moreover, the naked iron oxide NPs have high chemical activity and are easily oxidized in air (especially magnetite), generally resulting in loss of magnetism and dispersibility. Therefore, providing proper surface coating and developing some effective protection strategies to keep the stability of magnetic iron oxide NPs is very important. Silica-coated MNPs modified with TiO2 (Fe3O4 @SiO2@TiO2) was synthesized below 50 nm size and successfully applied as MSPE adsorbent for heavy-metal extraction (Zhang et al., 2012a). Silica has unique particles, water dispersivity, large surface area, and low toxicity. Silica protected the MNPs in acidic condition since metal adsorption totally depends on sample pH. TiO2 has high surface area, and large group of OH in TiO2 can cause a stable complex with metal ions. The adsorbed Cd(II), Cr(III), Mn(II), and Cu(II) on magnetic Fe3O4@SiO2@TiO2 adsorbent was desorbed using 0.5 M HNO3 and analyzed with ICP-MS. Sample pH was investigated from 1 to 9, and high recovery was obtained at pH 8 because of the terminal –OH groups in the surface. TiO2 is negatively charged and therefore there was easy adsorption of positive metal cations. Fe3O4@SiO2@TiO2 shows great potential selectivity, very low LOD (1.6–4.0 ng L¡1), high enrichment factor (100), high adsorption capacity (15.4–59.3 mg g¡1), and good recovery (92–105%) in real sample (tap water and lake water) analysis. Polymer-modified MNPs using tetraethylenepentamine were applied as MSPE sorbent for Cr(VI) sorption from water prior to detection using flame atomic absorption spectroscopy (FAAS) (Yao et al., 2012a). The prepared adsorbent with large –NH group in polymerization makes a strong interaction with Cr(VI). The MSPE method shows good enrichment factor (125£), low LOD (0.16 ng mL¡1), and high recovery (98–101%). Pretreatment of inorganic arsenic species has received particular attention using magnetic-based materials (Chandra et al., 2010; Huang et al., 2011; Lin et al., 2012; Luo et al., 2012). Maximum allowance of arsenic in drinking water set by the World Health Organization is 10 ng mL¡1. Thus, determination and removal of inorganic arsenic species from contaminated water system are needed. A nagnetic-based GO nanocomposite showed 99.9% arsenic removal from water at 0.1 ng mL¡1 concentration (Chandra et al., 2010). Graphene oxide protects the Fe3O4 nanoparticles from oxidation and avoids aggregation of NPs (Su et al., 2014). MNPs dispersed on GO can cause quick, easy, and conventional separation with an external magnet. Magnetic-GO nanocomposite shows great adsorption behavior for As(III) and As(V) at low pH values. At high pH (> GO pHPZC) the negative charge of adsorbent causes repulsion with the anionic form of arsenic species (Chandra et al., 2010). MSPE of inorganic arsenic reported (Huang et al., 2011) exhibited low LOD (0.21 ng L¡1), high extraction recovery (96–104%), and selectivity. In this study, magnetic Fe3O4 nanoparticles were synthesized using co-precipitation and coated with silica followed by modification using 3-(2-aminoethylamino) propyltrimethoxysiliane. The prepared nanocomposite (Fe3O4@SiO2-NH2) was applied as an MSPE sorbent for preconcentration of inorganic arsenic. SiO2 is

455

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465

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475

480

485

Q3 490

495

500

505

Magnetic SPE Based on Modified Ferum Oxides 510 reliable, chemically stable, and simple to functionalize with

515

520

525

530

535

540

545

550

555

560

565

–NH2 polar groups. Rich –NH2 functional groups on the modified surface of an adsorbent can form a complex with arsenic species because of their great affinity towards As(V). The adsorbed analyte was eluted with 1 mol L¡1 HNO3 followed by ICP-MS analysis. The maximum adsorption was obtained at pH below 9 because at pH from 3 to 8, the inorganic arsenic species is in anionic form (H2AsO4¡ and HAsO42¡). Finally, a rapid and sensitive method was developed for preconstruction of arsenic with good adsorption capacity (13.5 mg g¡1), less interference, and reusability (Huang et al., 2011). MNPs coated with 3-(trimethoxysilyl)-1-propantiol and functionalized with 2-amino-5-mercapto-1,3,4-thiadiazole were used as MSPE sorbent for Ag, Cd, Cu, and Zn extraction (Mashhadizadeh et al., 2011). These heavy metals were concentrated with high enrichment factors (170–194), reasonable LODs (0.11 ng mL¡1), and high recoveries (83–103%). The extracted analytes were eluted with 1 mL of 1 mol L¡1 HCl and detected with inductively coupled plasma-optical emission spectrometry (ICP-OES). Selectivity was investigated using coexisting ions, and target metals showed good recovery (81.5%), even in the presence of mg amounts of different metal ions. The maximum adsorption capacities obtained using synthesized MSPE adsorbent were: Ag, 10.4 mg g¡1; Cd, 4.7 mg g¡1; Cu, 3.8 mg g¡1; and Zn, 5.3 mg g¡1 (Mashhadizadeh et al., 2011). Acid-coated Fe3O4 nanoparticles successfully extracted heavy metals, including Cd, Co, Cr, Ni, and Pb (Faraji et al., 2010). Modified MNPs could extract metal ions from a complex matrix such as food. Heavy metals (Cd, Cu, Hg, and Pb) were isolated using Fe3O4-3-(trimethoxysilyl)-1-propanthiolethylene glycol. High adsorption capacities (29.8–41.6 mg g¡1) were obtained at high pH and reduced capacities at low pH, which might be due to –SH group oxidase (Mashhadizadeh et al., 2014). MNPs have been modified and applied for metal pretreatment, removal, extraction, and enrichment. Magnetic g-Fe2O3 nanoparticles coated with poly-L-cysteine (g-Fe2O3@PLCs) were applied as a chelating agent for As (III), Cu(II), Cd(II), Ni(II), Pb(II), and Zn(II) from water samples (White et al., 2009). Fast treatment (2.5 min) and good recoveries (>50%) were obtained. Adsorption capacities of 71–681 mg g¡1 were obtained for MNPs modified with PLCs in comparison with adsorption capacities of 90– 522 mg g¡1 obtained for unfunctionalized g-Fe2O3. Magnetite g-Fe2O3 has been used as an adsorbent of As (III) and As(V) from water. The g-Fe2O3 with specific high surface area was synthesized using the co-precipitation method and applied for removal of toxic arsenic from water. X-ray photoelectron spectroscopy (XPS) and Fourier transform-infrared (FT-IR) results demonstrated that the interaction between analyte and adsorbent is the coordinated –OH group of adsorbent with As(III) and As(V). High adsorption capacities (74.83 mg g¡1 for As(III) and 105.25 mg g¡1 for As(V)) at 50 C in contrast to low adsorption capacities obtained at 10 and 30 C are probably related to the formation of strong coordination at 50 C. Regeneration was obtained in six cycles without a

9 significant decrease in adsorption capacity for As(III) and As(V) (Lin et al., 2012). 570

Magnetic Solid-phase Extraction of Organic Compounds Removal, preconcentration, and determination of organic pollutants are necessary because of their toxic properties. These compounds include dyes, polycyclic aromatic hydrocarbons (PAHs), sulfonamides, phenols, plasticizers, fluorine compounds, and veterinary antibiotics, among others. MSPE has been applied successfully to pretreatment of organic components. MSPE has the advantages of both SPE and MNPs, which result in a rapid, flexible, high enrichment factor, high efficiency, water dispersive, and low-cost analytical process. In order to obtain a selective, sensitive, and stable method with unique physical and chemical properties in different environments, modified and functionalized magnetic adsorbents have been used as MSPE sorbent. PAHs are large class of toxic compounds that originate from incomplete combustion of organic components and are found in food, water, and edible oils (Zhao et al., 2011b). Maximum allowance of PAHs is 25 ng mL¡1 for total and 5 ng mL¡1 for heavy compounds with five or more benzene rings as set by the Spanish government (Spain, 2001). MNPs were synthesized and coated with gold nanoparticles followed by modification with 2-mercaptoethanol (ME) or 1-dodecanethiol (DDT) using the self-assembly method. In-house, Fe3O4@Au-ME and Fe3O4@Au-DDT determined preconcentrated PAHs from water with LODs of 0.26–16.7 ng mL¡1 and showed reasonable stability with eight times recycling. The thiol-containing ligands on the surface of the adsorbent show high affinity for PAHs (Li et al., 2014). Silver-modified MNPs, Fe3O4@Ag@bis(2,3,4-trimethylphenyl)-dithiophosphinic acid, were synthesized and showed high dispersibility and biocompatibility properties. Due to easy bonding of Ag and organosulfur (S-Ag), the MNPs were coated with Ag to increase the functional sites and form stable coordination. The nanocomposite is thermally stable up to 320 C and showed high extraction recovery (82.4–109.0%) for PAHs, with anti-interference ability (Tahmasebi and Yamini, 2012). PAHs were isolated using a new magnetic sorbent based on Fe3O4@ionic liquid@methyl orange. The synthesized method is self-assembly using C18mimBr on a magnetic surface. Ionic liquids (IL) are organic salts with potential benefits such as uniqueness, stability, conductivity, tunability, and miscibility. The synthesized magnetic adsorbent based on ILs has advantages of both ILs and methyl orange (MO) and thus strongly adsorbed PAHs from water with high recoveries (80.4–104.0%) (Liu et al., 2014a). Mixed hemi-micelles as a new absorbent were applied to PAH extraction with high efficiency due to the advantages of hydrophobic interaction (in hemi-micelles) and electrostatic interactions (in admicelles). Mixed micelle advantages in SPE are easy elution, high extraction efficiency, high flow rate, high breakthrough volume, and ability to be applied to different polarities of PAHs analytes (Cheng et al., 2012). To obtain easy, fast, and convenient extraction, a method based

575

580

585

590

595

600

Q4

605

610

615

620

10 625 on mixed micelles MNPs was used as the carrier. Thus, syn-

630

635

640

645

650

655

660

665

670

675

680

thesized MSPE sorbent based on magnetic Fe3O4 functionalized with C18 and modified with barium alginate (Fe3O4@C18@Ba2C-ALG) was applied to PAH analysis with LODs of 2–5 ng L¡1 and phthalate analysis with LODs of 19–59 ng L¡1 from water samples (Zhang et al., 2010a). The disadvantages of this method are that separation of mixed micelles from MNPs in analyte desorption using a solvent strongly depends on pH and ionic strength. Mixed micelles (Fe3O4@C16mimBr) adsorbed chlorophenols with 90% recovery (Cheng et al., 2012). Immobilized mixed hemimicelles on Fe3O4 were used as MSPE sorbent, then applied to ibuprofen extraction from water with good recovery (96– 99%), excellent preconcentration factor (99), and also low LOD (S/N D 3) was obtained (0.07 ng mL¡1) (Beiraghi et al., 2014a) The pH-independent adsorbent Fe3O4/C was synthesized based on carbon-coated MNPs using a hydrothermal method. The Fe3O4/C MNPs were applied for PAH preconcentration from water. Analytes adsorbed on the sorbent in a short time and eluted with a small amount of acetonitrile. The advantages of this method in PAH analysis include fast operation and high breakthrough volume (Zhang et al., 2010b). Graphene-based MSPE sorbent (G-Fe3O4) makes strong p-p interaction between PAH aromatic rings and graphene benzene rings (Huang et al., 2014; Wang et al., 2013c). Super paramagnetic Fe3O4@diphenol (Bianchi et al., 2012) exhibits lower LODs (0.04–0.31 ng mL¡1) for PAH analysis than ceramic/carbon-coated magnetic Fe3O4 nanoparticles (C- Fe3O4/C; LODs 0.7–50 pg mL¡1) (Heidari et al., 2012). Polymers based on MNPs have been used for PAH analysis. Fe3O4-polystyrene divinylbenzene-co-4-vinylebenzenesulfonic acid was synthesized using copolymerization to produce 50 nm particle sizes. This MSPE adsorbent has high surface area, dispersivity, and stability. Due to rich delocalized electrons on the adsorbent, PAHs are easily adsorbed, followed by quick extraction. The polymer-based MSPE method is sensitive and convenient and has low LODs (10.83–18.53 nM) (Zhang et al., 2012c). MSPE can extract PAHs from complex matrices such as oils. MSPE based on magnetic multiwalled carbon nanotubes (MWCNTs) was applied to the determination of PAHs in edible oils. The method is rapid (10 min) and extracted PAHs with high recoveries (87.8–122.3%) and low LODs (0.34– 2.9 ng g¡1) from edible oil samples. Toluene was selected as an elution solvent because its p-p interaction is stronger than in MWCNTs. The preconcentrated analytes were detected with GC-MS (Zhao et al., 2011b). Phthalate acid esters (PAEs) are commonly used in the plastics industry and in polyvinylchloride. PAEs are easily removed in the environment and increase organic pollutants that are carcinogenic and estrogenic. SPE is the convenience method in phthalate extraction due to easy manipulation, high enrichment, and high efficiency. Recently, graphenebased SPE application increased phthalate isolation with high recovery and preconcentration factor (Wu et al., 2013). In order to overcome disadvantages of graphene-based traditional SPE, MNPs are grafted on graphene or other sorbents

W. A. Wan Ibrahim et al. for fast operation and high loading of sample volume. MNPs deposited on graphene sheets (Fe3O4@G) were used as MSPE sorbent (Wang et al., 2012d; Wu et al., 2011). Fe3O4@graphene offers fast separation and high adsorption capacity specific for aromatic compounds. Fe3O4@graphene was used to remove methylene blue and Congo red with adsorption capacities of 45.27 mg g¡1 and 33.66 mg g¡1, respectively (Yao et al., 2012b). Poly(aniline-naphthylamine)-coated Fe3O4 adsorbed Rhodamine B from water and the LOD was found to be 0.1 ng mL¡1 (Bagheri et al., 2013), and graphene-based adsorbent (G-Fe3O4) extracted Rhodamine B with good adsorption capacity of 186 mg g¡1 (Lu et al., 2014). The MSPE based on Fe3O4@G is simple, sensitive, and stable with 12 extractions frequency. Graphene-based magnetic silica adsorbent (Fe3O4@SiO2-G) easily preconcentrated phthalates from a complex sample (milk) with less interference effect on recovery. Considering the effect of pH on graphene-based sorbent shows that phthalate recovery remained unchanged in the pH range 2.0–10.0 (Wang et al., 2013b ). Phthalates contain a benzene ring for a strong p-stacking interaction with the large p-electron system of graphene (Ye et al., 2014). Synthesized polythiophene-coated Fe3O4 was used to adsorb phthalate plasticizer from water samples with high preconcentration factors (86–213) (Tahmasebi et al., 2013). Polymer-modified MNP (Fe3O4@polypyrrole) pyrrole has been used for phthalate isolation from water. Polypyrrole improved dispersibility and avoided MNP aggregation; it was also sensitive and selective to phthalate adsorption with p-p interaction (Meng et al., 2011a). Sulfonamides are antibiotics used in veterinary medicine as antibacterial agents. Long-time consumption of these sulfonamides has led to drug resistance and ecological effects. Sulfonamide has been successfully isolated from soil samples using alumina-coated MNPs (Fe3O4/Al2O3). The results demonstrate that Fe3O4/Al2O3 is suitable as hydrophilic analytes for their high recoveries (71–93%), with low recoveries for hydrophobic analytes (42–60%) (Sun et al., 2010). Alumina-coated MNPs (Fe3O4/Al2O3) show great analytical potential in preconcentration of trimethoprim from water (Sun et al., 2009b). Surfactant immobilized MNPs were used in the determination of perfluorine compounds from water samples with HPLC/electrospray ionization (ESI)-MS/MS as a detector. LODs of perfluorine compounds with MSPE ranged from 0.022 to 0.31 ng L¡1 (Zhao et al., 2011c). Fe3O4@Al2O3 was used to preconcentrate glyphosate and aminomethylphosphonic acid from water and guava fruit samples. The LODs obtained were 0.3 ng mL¡1 for water samples and 0.01 mg g¡1 for guava fruit (Hsu et al., 2009). Magnetic molecularly imprinted polymers (Fe3O4@MIPs) have been applied as MSPE sorbent for sulfonamide extraction from poultry food. MIPs have unique chemical and physical properties as well as the ability to be used in harsh chemical media (Kong et al., 2012). Polyaniline-coated MNPs (Fe3O4@C@PANI) synthesized using hydrothermal method were applied for phenol extraction. High efficiency of aniline was obtained due to p-p interaction between aromatic analyte and aniline (Meng et al., 2011b).

685

690

695

700

Q5

705

710

715

720

725

730

735

740

Magnetic SPE Based on Modified Ferum Oxides

745

750

755

760

765

770

775

780

Recently, the use of magnetic-based material in the MSPE method for the removal of dye and its derivatives has increased. Safarin O dye was removed from water using Fe3O4 modified with sodium dodecyl sulfate with significant adsorption capacity (796.23 mg g¡1). The adsorption isotherm fits the Langmuir isotherm (Shariati et al., 2011). Magnetic M150-Fe3O4 has been synthesized as MSPE sorbent using copolymerization method with tetraethoxysilane and vinyl triethoxysilane. This nanocomposite is totally stable at pH > 2, has a high surface area (1022.4 m2 g), small particles, tiny pore size (2.6 nm), and fast kinetic. M150Fe3O4 showed great adsorption potential for p-nitrophenol (288 mg g¡1) and chlortetracycline (318 mg g¡1) (Ma et al., 2014). Cyclodextrin polymer–coated magnetic Fe3O4 nanoparticles were used as MSPE sorbent for rutin extraction. Good adsorption capacity (67 mg g¡1) was achieved for rutin due to significant p-p electron as well as reusability. LOD obtained was 7 ng mL¡1 (Gong et al., 2014). MSPE based on MNPs is capable of preconcentration of organic compounds from complex matrix samples such as milk, fruits, and cigarette smoke. Fe3O4@SiO2-phenyl extracted acetaldehyde from cigarette smoke with good recoveries (88–92%) (Huang et al., 2013). MNPs grafted by phosphatidylcholine (Fe3O4/PC) prepared using a simple method were applied in highly effective PAH preconcentration from milk, in which the obtained results (LOD D 0.2 ng L¡1, recovery 62%, and enrichment factor is 500) demonstrate that the proposed method is suitable for complex milk samples (Zhang et al., 2012b). Table 2 shows reports on the use of modified Fe3O4 MNPs as MSPE sorbent for extraction of organic compounds from water samples from the period 2008–2013. The determination of PAHs using two different materials based on Fe3O4-octadecylphosphonic acid and C18-Fe3O4 for PAHs was better with the former (lower LOD and better percentage recovery) using the same detection method (GC-MS). As can be seen, chlorophenols analysis with modified magnetic adsorbent (hemi-micelle-based adsorbent) shows lower LOD and 6£ higher enrichment factor than with polymer-based Fe3O4.

Magnetic Solid-phase Extraction of Biological Samples MNPs have some biological applications such as gene clon785 ing, cell separation, DNA purification, and drug delivery.

MNPs with silica shell (Fe3O4@SiO2) show potential benefits in cell separation, drug delivery, and enzyme immobilize. Antibacterial application of MNPs has been studied using MNPs functionalized by N-halamine (Dong et al., 2011). 790 Antibacterial properties of N-halamine were reported in the 1970s, and it is now a useful organic amino compound. The synthesized product has been applied successfully to positive and negative bacteria to test the antibacterial activity of synthesized magnetic nanocomposite. Minimum inhibitory con795 centrations for S. aureua and P. aeruginosa were 80 mg mL¡1 and 60 mg mL¡1, respectively, using N-halamine immobilized on MNPs functionalized with silica and polystyrene acrylate acid (PSA@Fe3O4@SiO2) (Dong et al., 2011).

11 Fe3O4@polypyrrole shows high efficiency in estrogen extraction from milk complex matrices without significant lees in adsorption capacity (Gao et al., 2011). Estrogens rich in –OH functional groups and benzene ring contain p-p electron, which make selective sorption on polypyrrole possessing p-p electron and –NH groups. Molecularly imprinted silica-coated MNPs (Fe3O4@SiO2@MIPs) were applied for preconcentration of estrogen from plasma samples. SiO2 can provide more positions for MIP bonding on the Fe3O4@SiO2 nanoparticle surface. MIPs caused an increase in the adsorption capacity and selective behavior on estrogen sorption due to strong p-p interaction. The prepared nanocomposite showed low interference effect with 93.1% recovery from plasma (Wang et al., 2012c). Puerarin is easily found in plasma with hydrophobic properties. C18 with significant hydrophobicity was bonded on Fe3O4@SiO2 to provide selective, fast, and highly effective extraction of puerarin from rat plasma. Biomatrix samples possess complex species and interferences that can affect analyte recovery. Fe3O4@SiO2@C18 is more suitable for biometrics with less interference effect with 92.3% adsorption recovery for puerarin (Wang et al., 2013a). Application of C18 functional Fe3O4 NPs for extraction of aromatic amines from human urine was studied. The prepared adsorbent was successfully applied in biological matrix and it was fast, with high extraction (77–125%) and sensitivity (0.8 ng mL¡1) (Jiang et al., 2014). Hydrophobic interaction between cephalosporin antibiotic and magnetic C18- Fe3O4@mSiO2 NPs was investigated. The synthesized MSPE adsorbent adsorbed cephalosporin from milk with low interference effects since milk is a complex matrix (Liu et al., 2014b). Hemi-micelle immobilized on Fe3O4 provide suitable extraction adsorbent of mefenamic acid from plasma and urine samples. The proposed method showed LODs for mefenamic acid, 0.097 ng mL¡1 in plasma and 0.087 ng mL¡1 in urine (Beiraghi et al., 2014b). Mixed micelles based on ionic liquid immobilized on Fe3O4/SiO2 nanoparticle surface was applied as flavonoid adsorbent in a bio-matrix. Ionic liquids have both a polar group in the head (ionic in nature) and a nonpolar group in the tail (hydrocarbon chain), so are suitable in various polarity conditions. Thermal stability, inflammability, and ability to dissolve in organic and inorganic solvents, without interference with proteins and endogenous , are some advantages of ionic liquids, but this totally depends on pH. Fe3O4/SiO2@ionic liquid shows high extraction recoveries (93.5–97.6%), high breakthrough volume, and less interferences in a biomatrix (He et al., 2014). Multiwalled CNTs were assembled on MNPs (Fe3O4@MWCNT) for extraction of phthalate esters from human urine. The proposed MSPE based on Fe3O4@MWCNT successfully detected phthalate in urine real samples (Rastkari and Ahmadkhaniha, 2013). Fast extraction of estrogenic endocrine-disrupting chemicals from water using magnetic Fe3O4@poly (divinylbenzene-co-methacrylic acid) adsorbent was achieved. The proposed method showed highly sensitive behavior for estrogenic monitoring (Li et al., 2010).

800

Q6 Q7

805

810

815

Q8

820

825

830

835

840

Q9 845

Q10

850

855

Fe3O4@bamboo charcoal Hemimicells/admicellsgraphene/Fe3O4 Fe3O4@P(DEVP-co-EDMA) Fe3O4/polyaniline Octadecylphosphonic acid-Fe3O4 C18-Fe3O4 Mixed hemimicelle-Fe3O4 CTAB-Fe3O4 Mixed hemimicelle CTAB-Fe3O4

2013 2012

2012 2011 2010 2009 2009 2008 2008

MSPE adsorbent

Year

Chlorophenols Methyl mercury PAHs PAHs Sulfonamide Phenolic Chlorophenols

Polybrominated diphenylether Perfluoroalkyl alkylphenols

Organic compounds

Water Seawater Water Water Water Water Water

Water Water

Sample matrix 79–101 57–94 92.7–108.0 98 77–119 35–99 70–102 68–104 83–98

0.2–0.34 ng mL¡1 0.1 ng mL¡1 14–70 ng L¡1 0.8–36 mg L¡1 0.02–0.03 mg L¡1 12–34 ng L¡1 0.11–0.15 mg L¡1

%R

0.25–0.63 ng L¡1 0.15–50 ng mL¡1

LOD

187 91 20 200 1000 800 700

114 125

EF

GC-MS HPLC-ESIMS/MS HPLC-UV GC-MS GC-MS GC-MS HPLC-UV LC-FLD HPLC-UV

Detector

Li et al., 2012 Mehdinia et al., 2011 Ding et al., 2010 Liu et al., 2009 Sun et al., 2009a Zhao et al., 2008a Zhao et al., 2008b

Zhao et al., 2013c Liu et al., 2012a

Ref.

TABLE 2 Some MSPE applications based on modified Fe3O4 in organic compound isolation evaluated by limit of detection (LOD), extraction recovery (% R), and enrichment factor (EF) and detector used from water samples

12 W. A. Wan Ibrahim et al.

Magnetic SPE Based on Modified Ferum Oxides

860

Q11 865

870

875

880

Graphene-based MNPs (Fe3O4/SiO2-graphene) was synthesized as a sulphonamide antibiotic adsorbent from water. The method exhibited LOD of 0.09 ng mL¡1 with RSD less than 10.7%. Electrostatic p-p interaction was a major factor in the adsorption mechanism due to large p-p-electron in the graphene surface and sulphonamide structure (Luo et al., 2011). Fe3O4@SiO2@graphene was applied for protein and peptide enrichment from saline solution (Liu et al., 2012b). MNPs functionalized with amine and carboxylic functional group were used as a protein separator (Jang and Lim, 2010). Quick extraction (0.5 min) was obtained for sulphonamide sorption from milk using polymer0coated Fe3O4/SiO2 nanoparticles (Gao et al., 2010). Molecularly imprinted MSPE based on magnetic CNT was used to determine gatifloxacin in serum samples with 85% recovery (Xiao et al., 2013). Preconcentration of tramadol from urine samples was performed using MSPE based on SiO2-Fe3O4@MIPs. The proposed adsorbent shows low LOD (1.5 ng mL¡1) and good recoveries (96.1–100.1%) (Madrakian et al., 2013). Fe3O4@ZrO2 was used as MSPE sorbent for extraction of Cr(III) from urine and serum. The proposed MSPE method exhibited good LOD (0.06 ng mL¡1), adsorption capacity (24.5 mg g¡1), enrichment factor (25), and recoveries (94–107%) in urine and serum analysis, as well as selective behavior for Cr (III) due to less effect of coexisting ions with high recovery (> 90%) (Wu et al., 2012).

Conclusions and Future Perspective 885 Isolation of analytes using MSPE has gained interest since

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1999. MNPs have been grafted with different materials such as alkoxides, graphene, CNTs, and hybrid inorganic-organic sol-gel for application in a wide range of analytical processes. We have reviewed applications of modified ferum oxide MNPs (especially Fe3O4) as MSPE adsorbent for isolation of pesticides, metal ions, organic compounds, and biological analytes in different media. MNPs have been modified using different materials in order to improve the analytical performance of the proposed MSPE methods. However, various challenges in conventional SPE can be overcome using super paramagnetism nanoparticles, such as extraction time, procedures, and enrichment factor. The presented materials based on MNPs isolated the analytes in very low levels from high volumes of environmental samples. MSPE adsorbent based on modified MNPs have a strong sorption affinity to various analytes due to their high surface area, stability in different pH values, fast kinetics, thermal stability, and independence from ionic strength as well as possessing different functional group. MSPE is more convenient for preconcentration of pesticides from complex samples such as fruits, vegetables, milk, water, and biological samples. The considered literature demonstrated MSPE based mostly on Fe3O4-modified MNPs, offering potential benefits that include fast extraction process, stability, selectivity, reusability, sensitivity, repeatability, and ease of use/convenience. The very low contaminant concentrations and highly complex sample matrices impose extensive use of efficient and

13 reliable techniques for sample preparation. Therefore, the selectivity of these techniques is of primary importance. The 915 use of MNPs in sample preparation for isolation, preconcentration, and enrichment for identification and quantification will continue to be of interest in the years to come.

Funding The authors would like to thank the Ministry of Education 920 Malaysia for financial support through the Research University Grants No. 04H22, and 10J43 and Ministry of Education Malaysia for the Fundamental Research Grant Scheme (FRGS) grant no. 4F307. H. R. Nodeh would like to thank UTM for the IDF award received. 925

Abbreviations CNT DDAC DLME EF EU FAAS G GC GC-FID GC-MS GC-NPD

D D D D D D D D D D D

GO HPLC ICP-MS IL LOD MIP MNP MRL MSPE MWCNT OCP OPP PAH PSDVB R SPE UFLC

D D D D D D D D D D D D D D D D D

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