Recent advances and applications of cyclodextrins in magnetic solid phase extraction.

Cyclodextrins (CDs) as a family of cyclic oligosaccharides are toroidal with a hydrophobic interior and a hydrophilic exterior. They are well-known for their ability to form host-guest inclusion complexes with different compounds. They are used as chiral stationary phases in high performance liquid chromatography (HPLC) and gas chromatography (GC) or as chiral reagents in the background electrolyte of capillary electrophoresis (CE). In recent years, they have been used for modification of sorbents or as sorbents in solid phase extraction (SPE) procedures. Magnetic solid-phase extraction (MSPE), as a new type of SPE procedure, has received considerable attention due to its rapid phase separation process as compared to traditional extraction mode. This review covers the synthesis of CD-based magnetic sorbents (such as immobilization of CDs onto the different supports, production of nanosponges, and making hybrid substances with nanomaterials) and the use of these compounds in MSPE of different analytes from biological, environmental, and food samples. Also, prospects of CD-based sorbents for sample pre-treatment are also proposed.

Micro-solid phase extraction of some polycyclic aromatic hydrocarbons from environmental water samples using magnetic ß-cyclodextrin-carbon nano-tube composite as a sorbent.

Previous studies have demonstrated the excellent capability of the cyclodextrins in pre-concentration of the organic pollutants from the aqueous solutions. In this work, ß-cyclodextrin- multiwalled carbon nano-tube composite was produced from the reaction of oxidized carbon nano-tube with cyclodextrin in the presence of the hydrazine hydrate, and subsequently attaching this composite to the iron oxide nano-particles. Prepared magnetic nano-composite was characterized by the attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), the thermogravimetric analysis (TGA), the field emission scanning electron microscopy (FESEM), and the X-ray diffraction (XRD). This composite was applied to extract seven polycyclic aromatic hydrocarbons (PAHs) from the environmental water samples as follows: naphthalene, acenaphthene, fluorene, phenanthrene, fluoranthene, pyrene and benzo[a]pyrene. Analytes analysis was performed using the gas chromatography (GC) followed by the flame ionization detection (FID), and the predominant parameters influencing the extraction efficiency were investigated thoroughly. Under the optimized extraction conditions, the enrichment factor (EF) was ranging from 41.3 to 49.3 (EFmax = 50.0), and a suitable linearity was obtained (R2 = 0.992-0.997) within the range of 2.0-1000 ng/mL. The limits of the quantification and detection were 2.0-10.0 and 0.6-3.0 ng/mL, respectively. Finally, the synthesized magnetic sorbent and method were successfully utilized for the analysis of rain, well and agricultural water samples. The relative recoveries were ranging from 75.3-107.0% with an acceptable precision (5.5-8.3%) for PAHs extraction.

Polydopamine-assisted attachment of ß-cyclodextrin onto iron oxide/silica core-shell nanoparticles for magnetic dispersive solid phase extraction of aromatic molecules from environmental water samples.

Pollution monitoring in a contaminated environmental water samples is a big challenge. In this article, immobilization of ß-cyclodextrin molecules onto the magnetic core-shell silica nanoparticles was conducted by using adhesive properties of polydopamine. The synthesis path was included of three steps: producing Fe3O4 nanoparticles as a core, coating the cores with a silica layer, and further coating with ß-cyclodextrin molecules. The structural characteristics of the synthesized nanocomposite were investigated by using attenuated total reflection-Fourier transform infrared spectroscopy, x-ray diffraction analysis, field emission scanning microscopy, transmission electron microscopy, dynamic light scattering, vibrating-sample magnetometer and energy-dispersive X-ray spectroscopy. Afterwards, obtained nanocomposite was used to extract eight polycyclic aromatic hydrocarbons from environmental water samples. Results were demonstrated that analyts with different chemical structures had different extraction manners during the process. Important effective parameters on the extraction efficiency; such as sorbent type and mass, desorption solvent (type and volume), salt concentration and the time of extraction & desorption; were investigated. Under the optimum operating conditions, good linearity within the range of 1-1000 ng/mL was obtained while coefficient of determination (r2) was in the range of 0.990-0.998. The limits of detection were between 0.04 and 0.57 ng/mL, and the enrichment factor was found to be 21-90. This nanocomposite was also applied for the extraction and enrichment of aromatic analytes from the canal and rain water samples prior to gas chromatography analysis.

Micro-solid phase extraction of benzene, toluene, ethylbenzene and xylenes from aqueous solutions using water-insoluble ß-cyclodextrin polymer as sorbent.

Water-insoluble ß-cyclodextrin polymer was synthesized by chemical cross-linking using epichlorohydrin (EPI) as a cross-linker agent. The produced water-insoluble polymer was used as a sorbent for the micro-solid phase extraction (µ-SPE) of benzene, toluene, ethylbenzene and xylenes (BTEX) from water samples. The µ-SPE device consisted of a sealed tea bag envelope containing 15mg of sorbent. For the evaluation of the extraction efficiency, parameters such as extraction and desorption time, desorption solvent and salt concentration were investigated. At an extraction time of 30min in the course of the extraction process, analytes were extracted from a 10mL aqueous sample solution. The analytes were desorbed by ultrasonication in 200µL of acetonitrile for 20min. Analysis of the analytes was done by a gas chromatography-flame ionization detector (GC-FID) system. The enrichment factor (EF) was found to be in the range 23.0-45.4 (EFmax=50.0). The method provided linearity ranges of between 0.5 and 500.0ng/mL (depending on the analytes), with good coefficients of determination (r2) ranging between 0.997 and 0.999 under optimized conditions. Detection limits for BTEX were in the range of between 0.15 and 0.60ng/mL, while corresponding recoveries were in the range of 46.0-90.0%. The relative standard deviation of the method for the analytes at 100.0ng/mL concentration level ranged from 5.5 to 11.2% (n=5). The proposed method was concluded to be a cost effective and environmentally-friendly extraction technique with ease of operation and minimal usage of organic solvent.