Journal of Analytical Methods in Chemistry

Journal of Analytical Methods in Chemistry / 2014 / Article

Research Article | Open Access

Volume 2014 |Article ID 976145 | 6 pages | https://doi.org/10.1155/2014/976145

Preparation and Characterization of an Amphipathic Magnetic Nanosphere

Academic Editor: Xiu-Ping Yan
Received24 Nov 2013
Accepted04 Jan 2014
Published05 Mar 2014

Abstract

The amphipathic magnetic nanospheres were synthesized using C8 and polyethylene glycol as ligands. Their morphology, structure, and composition were characterized by transmission electron microscope, Fourier transform infrared, and elementary analysis. The prepared materials presented uniform sphere with size distribution about 200 nm. The magnetic characteristics of magnetic nanomaterials were measured by vibrating sample magnetometer. The target products had a saturation magnetization value of 50 emu g−1 and superparamagnetism. The adsorption capability was also studied by static tests, and the material was applied to enrich benzenesulfonamide from calf serum. The results exhibited that the C8-PEG phase owned better adsorption capability, biocompatible property, and dispersivity in aqueous samples.

1. Introduction

Magnetic nanoparticles (MNPs) have been the hot topic of scientific research. The reports not only were concerned with their fundamental properties, but also involved the promotion of their characteristics and real applications [1]. The researches concerning the promotion of MNPs’ properties focused on the chemical modification onto the surface of MNPs in order to accommodate different aim of application. MNPs have been applied extensively in various fields, for example, magnetic storage media, bioseparation [27], drug delivery [8], biomolecular sensors [9], magnetic resonance imaging [10], jet printing [11], and so on.

Recently, magnetic nanoparticles coupled to magnetic carrier technology (MCT) have also been used in solid-phase extraction (SPE), especially for analyzing environmental and biological samples. Song et al. [12], Zhao et al. [13, 14], and Li et al. [15] utilized bare or silicon-coated as extracting sorbent to enrich organic pollutants. Yantasee et al. [16] took thiol-modified MNPs to remove metallic ion from water. Qi et al. [17] immobilized ions on the surface of MNPs for selective enrichment of the phosphopeptides. Liu et al. [18] and Yao et al. [19] prepared magnetic and microspheres to extract polycyclic aromatic hydrocarbons (PAHs) from water and polypeptide from serum, respectively. Zhang et al. [20] reported the application of magnetic molecularly imprinted polymers (MIP) in solid or semisolid samples for trace analysis of triazines and tetracycline antibiotics. Niu et al. [21] prepared carbon-encapsulated MNPs for isolation of organic pollutants. The magnetic MIP with bisphenol A (BPA) as a template was also prepared and applied to extract BPA from environmental water and milk samples [22]. The extraction can be easily achieved by dispersing the magnetic sorbents to sample solution, and the sorbents can be effortlessly isolated from the mixture by an external magnet. Compared to common SPE with nanomaterials, the magnetic SPE not only can build a controllable rebinding process and allow magnetic separation to replace the centrifugation and filtration step in a convenient and economical way, but can also avoid troubles of packing SPE column and the time-consuming process of loading large volume samples. It has been successfully employed in rapid pretreatment of large volume samples.

The dispersivity and compatibility of sorbents used in magnetic SPE are the key factors for their application. Several attempts have been done to fabricate better magnetic sorbents. MNPs using -cyclodextrin (-CD) as ligand were manufactured, and they showed superior dispersivity in water [23]. Hu et al. [24] improved the biocompatibility of magnetic MIP by combining SPE with liquid-liquid extraction (LLE). Li et al. [25] synthesized amphoteric magnetic microspheres owning hydrophilicity and hydrophobicity. But they could not take consideration to dispersivity and biocompatibility. However, the biocompatibility was necessary for the samples containing biomolecules. and materials are the classical sorbents of SPE. Polyethylene glycol (PEG) due to hydrophilic and biocompatible properties has been used as ligand to prepare various functional materials [1, 26]. It would be a promising sorbent to simultaneously bond and PEG onto the surface of MNPs.

In the present work, magnetic nanospheres possessing hydrophilic, hydrophobic, and biocompatible properties were produced with and PEG as ligands. The obtained products were applied to enrich benzenesulfonamide from calf serum.

2. Experimental

2.1. Chemicals and Materials

Sodium acetate (NaAc), triethylamine (TEA), polyethylene glycol (PEG), ethylene glycol, and ferric chloride () were obtained from Tianjin Chemicals Corporation (Tianjin, China). Tetraethoxysilane (TEOS) and octyltrimethoxysilane (OCS) were purchased from Fluka (Switzerland). These chemicals were all of analytical grade. Sulfamerazine (SMR) was purchased from Alfa Aesar (Karlsruhe, Germany; 98.5%). Acetonitrile and methanol of chromatography grade were purchased from Dima Technology (Richmond Hill, USA). All other reagents were of analytical reagent grade and the purified water by Milli-Q system was used throughout the experiments.

2.2. Preparation of Magnetic Nanoparticles

The preparation protocol of magnetic nanospheres is shown in Figure 1.

Ferric chloride (2.7 g, 10 mmol) was dissolved in ethylene glycol (80 mL) to form a clear solution, followed by the addition of NaAc (7.2 g) and polyethylene glycol (MW800, 1.0 g). After ultrasonication for 10 min, the mixture was stirred vigorously for 30 min. Then, it was sealed in a teflon-lined stainless-steel autoclave (100 mL capacity). The autoclave was maintained at 190°C for 10 h and then cooled to room temperature. The black products () were washed several times with ethanol and dried at 60°C for 12 h.

The obtained magnetic nanoparticles were encapsulated into silica beds as follows [26]: 1.0 g was suspended in 200 mL ethanol, then ammonia (25%, 30 mL), water (30 mL), and TEOS (3 mL) were added sequentially into the generated solution. After degassed, the mixture was stirred vigorously for 2 h at 50°C under nitrogen gas protection. The magnetic particles were separated from the resulting solution by a magnet and the supernatant was discarded. The target materials were rinsed with ethanol to remove excess reactants, neutralized with HCl (0.1 mol ), and washed with water. The obtained materials (@) were dried under vacuum at 80°C for 12 h.

One gram of @, 60 mL of toluene, 1 mL of OCS, and 0.5 mL of TEA were added successively to a flask. The mixture was refluxed under nitrogen gas protection and stirring for 10 h. After cooling, the magnetic particles were separated from the mixture by a magnet and the bonded phase was rinsed with toluene. The obtained products were dispersed again to 60 mL of toluene. 1 mL of PEG (MW400) and 0.5 mL of TEA were added successively to the mixture. After refluxing and stirring for 10 h, the -PEG bonded materials were obtained and rinsed with toluene and ethanol. The products were dried under vacuum at 80°C for 12 h.

2.3. Characterization

The obtained products were characterized with JEM1200EX transmission electron microscope (TEM) (Tokyo, Japan) and Nicolet Nexus 670 Fourier transform infrared (FTIR) (MN, USA) spectrometer. Elementary analysis (EA) was performed on a Vario-EL analyzer (Elementar, Germany). Magnetic properties were measured using a vibrating sample magnetometer (VSM) (Lakeshore 7304, USA).

2.4. Adsorption Tests

To measure adsorption capacity, 20 mg of -PEG was added into 10 mL SMR solution with desired concentration. The mixture was shaken for 12 h at room temperature to facilitate adsorption of SMR onto -PEG phase. After the magnetic sorbents were isolated by an external magnetic field, SMR of the supernate was determined by high performance liquid chromatography (HPLC). The chromatographic system consisted of Varian 210 high performance liquid chromatographic pump (CA, USA), 325 UV-Vis detector, and Varian Star Chromatographic workstation. An analytical reversed-phase column (5 m,  mm, Dima Technology Richmond Hill, USA) was used. The mobile phase was a mixture of acetonitrile and water (60 : 40, v/v) with flow rate of 0.8 mL  and the detection was carried out at 263 nm. The same procedure was performed for the bonded material. All tests were conducted in triplicate.

2.5. Application in Real Samples

The samples of calf serum with 10 g m SMR were diluted to 4, 2, and 1 g m, respectively. 20 mg of -PEG activated by methanol and water was added to 10 mL of diluted samples, after vortex and standing for 5 min, and then the sorbents were isolated by an external magnet. The sorbents were washed by water and hexane and then eluted by 3 mL of acetonitrile containing 1% acetic acid. At last, the elution was analyzed by HPLC-UV.

3. Results and Discussion

3.1. Characterization
3.1.1. FTIR

All products were measured by FTIR spectrometry step by step, and the results are listed in Figure 2. IR spectra provided clear evidence for the surface modification. Figure 2(a) displays the IR spectrum of the bare magnetic particles and the characteristic band of appeared at about 580 . The unique Si-O absorption band was observed from 1000 to 1100  (Figure 2(b)), indicating that silica coating was successful on the magnetite surface. In spectra of and -PEG bonded particles a typical band of C–H stretch was about 2900 , and the adsorption bands between 1100 and 1600  were related closely to R–OH, suggesting that the and -PEG phase were prepared successfully.

3.1.2. EA

Elemental analysis was employed to measure the composition of and -PEG phase products, and the results are listed in Table 1. Comparing -PEG to phase, the mass fraction of C and H increased, confirming that PEG was successfully bonded onto the surface of magnetic nanospheres. However, it cannot ensure precisely the component of C and H on the surface of magnetic nanospheres based on the data of elemental analysis.


Solid phaseC (%)H (%)

C82.5230.882
C8-PEG2.9901.182

3.1.3. TEM

Their morphological feature of all products was observed by TEM in Figure 3. As can be seen, most of the obtained nanospheres exhibited regularly spherical shape with size distribution about 200 nm. After the modification of silica, the magnetic nanospheres showed core-shell structure, and the thickness of shell was estimated to be about 20–30 nm. No significant differences were observed between and -PEG phase.

3.1.4. VSM

It is vitally important for MCT that the sorbents should possess sufficient magnetic and superparamagnetism property. VSM was employed to characterize magnetic properties of the obtained magnetic materials, and the VSM magnetization curves are shown in Figure 4. All magnetization curves were uniformly symmetric, confirming that the prepared products presented superparamagnetism. It can be seen that the saturation magnetization value of , @, , and -PEG decreased, respectively, due to the increase of nonmagnetic density. However, the saturation magnetization value of -PEG was 50 emu , which indicated that -PEG phase materials possessed superior magnetic property.

3.1.5. Dispersivity

The dispersivity was investigated in order to evaluate the difference of and -PEG. As shown in Figure 5, 20 mg of magnetic materials was dispersed to 2 mL of water or 50% ethanol solution. From Figure 5(a), the left photograph displays that and -PEG were dispersed to water by sonication, and the right photograph shows that the sorbents were collected by magnet after 10 s. The dispersivity of -PEG in water was visibly better than . Figure 5(b) illustrates that and -PEG were dispersed to 50% ethanol solution, and no evident differences of dispersivity were observed. The results confirmed that the magnetic material can be separated easily from solution by an external magnet and -PEG phase presented superior property to .

3.2. Adsorption Tests

The adsorption capability of and -PEG was researched by static tests with SMR as the target compound. As shown in Figure 6, the capacity of -PEG was about two times of with the concentration of SMR in the range 20–100 mg , and the differences decreased with the increase of SMR concentration. The differences were caused by their different dispersivity in sample solution. The sample solution used in static tests was obtained by diluting the methanol solution of SMR 1000 mg . -PEG was better dispersed in sample solution than when the SMR concentration was lower, and the differences of dispersivity between and -PEG reduced while the concentration of SMR was higher. Furthermore, the hydrogen bond between O or OH of PEG and amine of SMR also contributed to the differences. The tests revealed that -PEG presented superior adsorption property to for liquid samples.

3.3. Application in Real Samples

In order to study the feasibility of -PEG in the real application, it was applied to enrich SMR from calf serum and the spiked recoveries were investigated. As shown in Figure 7, the recoveries rose by 40% while the dilution ratio of the spiked samples (SMR, 10 g m) increased from 2.5 to 10. Under the condition of 10-times dilution, -PEG could achieve better recovery without other pretreatments, confirming that it can reduce effectively the matrix effect, for example, the influences of protein, polypeptide, fat, and so on. The results demonstrated that -PEG owning biocompatibility can be applied in the pretreatment of biological samples.

4. Conclusion

The novel magnetic nano-spheres were prepared using and polyethylene glycol as ligands. The prepared materials presented uniform sphere with size distribution about 200 nm and superparamagnetism. The results of tests proved that -PEG owned better dispersivity in aqueous samples, adsorption capability, and biocompatible property. -PEG was used to enrich SMR from calf serum and the spiked recoveries were 80%. -PEG performed superior potential in biological samples.

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

Acknowledgments

This work was supported by the Key Project of Henan Province Education Department Science and Technology Research (12A350002), the Doctoral Research Fund of Henan Chinese Medicine (BSJJ-2010-23), and the Open Project of Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University (LZUMMM 2010014).

References

  1. L. H. Reddy, J. L. Arias, J. Nicolas, and P. Couvreur, “Magnetic nanoparticles: design and characterization, toxicity and biocompatibility, pharmaceutical and biomedical applications,” Chemical Reviews, vol. 112, no. 11, pp. 5818–5878, 2012. View at: Google Scholar
  2. S. Y. Huang and Y. C. Chen, “Magnetic nanoparticle-based platform for characterization of histidine-rich proteins and peptides,” Analytical Chemistry, vol. 85, no. 6, pp. 3347–3354, 2013. View at: Google Scholar
  3. C. J. Tan, H. G. Chua, K. H. Ker, and Y. W. Tong, “Preparation of bovine serum albumin surface-imprinted submicrometer particles with magnetic susceptibility through core-shell miniemulsion polymerization,” Analytical Chemistry, vol. 80, no. 3, pp. 683–692, 2008. View at: Publisher Site | Google Scholar
  4. W. Lu, Y. Shen, A. Xie, and W. Zhang, “Preparation and protein immobilization of magnetic dialdehyde starch nanoparticles,” The Journal of Physical Chemistry B, vol. 117, no. 14, pp. 3720–3725, 2013. View at: Google Scholar
  5. Z. Zou, M. Ibisate, Y. Zhou, R. Aebersold, Y. Xia, and H. Zhang, “Synthesis and evaluation of superparamagnetic silica particles for extraction of glycopeptides in the microtiter plate format,” Analytical Chemistry, vol. 80, no. 4, pp. 1228–1234, 2008. View at: Publisher Site | Google Scholar
  6. Y. C. Li, Y. S. Lin, P. J. Tsai, C. T. Chen, W. Y. Chen, and Y. C. Chen, “Nitrilotriacetic acid-coated magnetic nanoparticles as affinity probes for enrichment of histidine-tagged proteins and phosphorylated peptides,” Analytical Chemistry, vol. 79, no. 19, pp. 7519–7525, 2007. View at: Publisher Site | Google Scholar
  7. A. M. Nowicka, A. Kowalczyk, A. Jarzebinska et al., “Progress in targeting tumor cells by using drug-magnetic nanoparticles conjugate,” Biomacromolecules, vol. 14, no. 3, pp. 828–833, 2013. View at: Google Scholar
  8. E. Amstad, J. Kohlbrecher, E. Müller, T. Schweizer, M. Textor, and E. Reimhult, “Triggered release from liposomes through magnetic actuation of iron oxide nanoparticle containing membranes,” Nano Letters, vol. 11, no. 4, pp. 1664–1670, 2011. View at: Publisher Site | Google Scholar
  9. L. Zhang, B. Liu, and S. Dong, “Bifunctional nanostructure of magnetic core luminescent shell and its application as solid-state electrochemiluminescence sensor material,” Journal of Physical Chemistry B, vol. 111, no. 35, pp. 10448–10452, 2007. View at: Publisher Site | Google Scholar
  10. L. Qi, L. Wu, S. Zheng, Y. Wang, H. Fu, and D. Cui, “Cell-penetrating magnetic nanoparticles for highly efficient delivery and intracellular imaging of siRNA,” Biomacromolecules, vol. 13, no. 9, pp. 2723–2730, 2012. View at: Google Scholar
  11. P. Tiberto, G. Barrera, F. Celegato et al., “Magnetic properties of jet-printer inks containing dispersed magnetite nanoparticles,” The European Physical Journal B, vol. 86, no. 4, pp. 1–6, 2013. View at: Google Scholar
  12. Y. Song, S. Zhao, P. Tchounwou, and Y. M. Liu, “A nanoparticle-based solid-phase extraction method for liquid chromatography-electrospray ionization-tandem mass spectrometric analysis,” Journal of Chromatography A, vol. 1166, no. 1-2, pp. 79–84, 2007. View at: Publisher Site | Google Scholar
  13. X. Zhao, Y. Shi, Y. Cai, and S. Mou, “Cetyltrimethylammonium bromide-coated magnetic nanoparticles for the preconcentration of phenolic compounds from environmental water samples,” Environmental Science and Technology, vol. 42, no. 4, pp. 1201–1206, 2008. View at: Publisher Site | Google Scholar
  14. X. Zhao, Y. Shi, T. Wang, Y. Cai, and G. Jiang, “Preparation of silica-magnetite nanoparticle mixed hemimicelle sorbents for extraction of several typical phenolic compounds from environmental water samples,” Journal of Chromatography A, vol. 1188, no. 2, pp. 140–147, 2008. View at: Publisher Site | Google Scholar
  15. J. Li, X. Zhao, Y. Shi, Y. Cai, S. Mou, and G. Jiang, “Mixed hemimicelles solid-phase extraction based on cetyltrimethylammonium bromide-coated nano-magnets Fe3O4 for the determination of chlorophenols in environmental water samples coupled with liquid chromatography/spectrophotometry detection,” Journal of Chromatography A, vol. 1180, no. 1-2, pp. 24–31, 2008. View at: Publisher Site | Google Scholar
  16. W. Yantasee, C. L. Warner, T. Sangvanich et al., “Removal of heavy metals from aqueous systems with thiol functionalized superparamagnetic nanoparticles,” Environmental Science and Technology, vol. 41, no. 14, pp. 5114–5119, 2007. View at: Publisher Site | Google Scholar
  17. D. Qi, Y. Mao, J. Lu, C. Deng, and X. Zhang, “Phosphate-functionalized magnetic microspheres for immobilization of Zr4+ ions for selective enrichment of the phosphopeptides,” Journal of Chromatography A, vol. 1217, no. 16, pp. 2606–2617, 2010. View at: Publisher Site | Google Scholar
  18. Y. Liu, H. Li, and J. M. Lin, “Magnetic solid-phase extraction based on octadecyl functionalization of monodisperse magnetic ferrite microspheres for the determination of polycyclic aromatic hydrocarbons in aqueous samples coupled with gas chromatography-mass spectrometry,” Talanta, vol. 77, no. 3, pp. 1037–1042, 2009. View at: Publisher Site | Google Scholar
  19. N. Yao, H. Chen, H. Lin, C. Deng, and X. Zhang, “Enrichment of peptides in serum by C8-functionalized magnetic nanoparticles for direct matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis,” Journal of Chromatography A, vol. 1185, no. 1, pp. 93–101, 2008. View at: Publisher Site | Google Scholar
  20. Y. Zhang, R. Liu, Y. Hu, and G. Li, “Microwave heating in preparation of magnetic molecularly imprinted polymer beads for trace triazines analysis in complicated samples,” Analytical Chemistry, vol. 81, no. 3, pp. 967–976, 2009. View at: Publisher Site | Google Scholar
  21. H. Niu, Y. Wang, X. Zhang, Z. Meng, and Y. Cai, “Easy synthesis of surface-tunable carbon-encapsulated magnetic nanoparticles: adsorbents for selective isolation and preconcentration of organic pollutants,” ACS Applied Materials and Interfaces, vol. 4, no. 1, pp. 286–295, 2012. View at: Publisher Site | Google Scholar
  22. Y. Ji, J. Yin, Z. Xu et al., “Preparation of magnetic molecularly imprinted polymer for rapid determination of bisphenol A in environmental water and milk samples,” Analytical and Bioanalytical Chemistry, vol. 395, no. 4, pp. 1125–1133, 2009. View at: Publisher Site | Google Scholar
  23. Y. Ji, X. Liu, M. Guan et al., “Preparation of functionalized magnetic nanoparticulate sorbents for rapid extraction of biphenolic pollutants from environmental samples,” Journal of Separation Science, vol. 32, no. 12, pp. 2139–2145, 2009. View at: Publisher Site | Google Scholar
  24. Y. Hu, R. Liu, Y. Zhang, and G. Li, “Improvement of extraction capability of magnetic molecularly imprinted polymer beads in aqueous media via dual-phase solvent system,” Talanta, vol. 79, no. 3, pp. 576–582, 2009. View at: Publisher Site | Google Scholar
  25. Q. Li, M. H. Lam, R. S. Wu, and B. Jiang, “Rapid magnetic-mediated solid-phase extraction and pre-concentration of selected endocrine disrupting chemicals in natural waters by poly(divinylbenzene-co-methacrylic acid) coated Fe3O4 core-shell magnetite microspheres for their liquid chromatography-tandem mass spectrometry determination,” Journal of Chromatography A, vol. 1217, no. 8, pp. 1219–1226, 2010. View at: Publisher Site | Google Scholar
  26. H. X. Zhang, M. C. Liu, and P. L. Zhu, “Preparation of a polyglycol-C8 bonded phase and its characteristics,” Chromatographia, vol. 51, no. 7-8, pp. 437–442, 2000. View at: Google Scholar

Copyright © 2014 Yongsheng Ji et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

1270 Views | 646 Downloads | 2 Citations
 PDF  Download Citation  Citation
 Download other formatsMore
 Order printed copiesOrder

We are committed to sharing findings related to COVID-19 as quickly and safely as possible. Any author submitting a COVID-19 paper should notify us at help@hindawi.com to ensure their research is fast-tracked and made available on a preprint server as soon as possible. We will be providing unlimited waivers of publication charges for accepted articles related to COVID-19. Sign up here as a reviewer to help fast-track new submissions.