Magnetic Solid-phase Extraction Material Research Articles

Analysis of Perfluorinated Compounds in Environmental Water Using Decyl-perfluorinated Magnetic Mesoporous Microspheres as Magnetic Solid-Phase Extraction Materials and Microwave-Assisted Derivatization Followed by Gas Chromatography-mass Spectrometry.

In this work, a new method was developed for perfluorinated compounds (PFCs) analysis in water samples based on decyl-perfluorinated magnetic mesoporous nanocomposites microspheres-assisted extraction and microwave-assisted derivatization followed by gas chromatography-mass spectrometry analysis. The decyl-perfluorinated magnetic mesoporous nanocomposites have several advantages such as fast separation ability, good dispersibility in water sample and high selective preconcentration of PFCs. Various parameters, including eluting solvent and volume, the amounts of absorbents, extraction time and elution time, the microwave-assisted derivatization conditions were optimized. Validation studies showed that this method has good linearity (r2 > 0.9970), satisfactory precision (RSD < 7.8%) and high recovery (93-107%). The limits of detection were found to be 0.055-0.086 μg/L and the limits of quantification be 0.18-0.28 μg/L, respectively. The results indicated that the proposed method has advantages of convenience, good sensitivity and high efficiency. The method has been applied successfully to analyze perfluorinated organic acids in real water samples.

Magnetically responsive textile for a new preconcentration procedure: Magnetic textile solid phase extraction

A new preconcentration procedure named “Magnetic textile solid phase extraction” was developed. A piece of nonwoven textile (fabric) was used for the immobilization of copper phthalocyanine dye and employed for the adsorption of crystal violet and safranin O from large volumes of sample. The bound dye was eluted into small volume of methanol. The limit of detection and limit of quantification values for safranin O were 2.66 µg/L and 8.87 µg/L, while for crystal violet these values were 2.17 µg/L and 7.23 µg/L, respectively. Linearity in the range 5–100 µg/L was observed. In order to prepare magnetically responsive adsorbent, an iron-based standard staple was inserted in the textile material using an office stapler. The developed procedure can be easily adapted for the detection of large variety of analytes in biochemistry, biotechnology, environmental technology, and forensic analysis.

Reduced Graphene Oxide-Based Solid-Phase Extraction for the Enrichment and Detection of microRNA.

MicroRNAs (miRNAs) are endogenous molecules with regulatory functions. The purification and enrichment of miRNA are essential for its precise and sensitive detection. miRNA isolated using commercial kits contains abundant interfering RNAs, and the concentration of miRNA may not be adequate for detection. Herein, we prepared a reduced graphene oxide (rGO)-based magnetic solid-phase extraction material for the enrichment and ultrasensitive detection of miRNA from intricate nucleic acid solutions. In situ reverse transcription (RT) was developed as the most efficient approach to desorb miRNA from rGO among the methods that are compatible for the subsequent amplification reported thus far. Additionally, rolling circle amplification and qPCR were used to detect let-7a with a decrease of the limit of detection by 24.7- and 31.3-fold, respectively. This material was also successfully used to extract and detect miRNA from total RNA isolated from human plasma. Our results show that the material prepared in this study has the potential for cancer biopsy in clinics and the discovery of new miRNAs in scientific research.

Magnetic Dummy Template Silica Sol–Gel Molecularly Imprinted Polymer Nanospheres as Magnetic Solid-Phase Extraction Material for the Selective and Sensitive Determination of Bisphenol A in Plastic Bottled Beverages

In this study, a core–shell magnetic dummy molecularly imprinted polymer (MDMIP) was prepared with a novel and simple method. The imprinting layer was synthesized directly on the surface of Fe3O4 by only one step, which avoided further modification on the exterior of magnetic core. 4,4′-Dihydroxybiphenyl (DDBP) was used as dummy template instead of bisphenol A (BPA) to eliminate the effect of template leakage on quantitative analysis. When used as solid-phase extraction sorbent, a rapid, sensitive, and accurate method for the simultaneous extraction, concentration, and determination of trace BPA in plastic bottled beverage samples by MDMIP-SPE coupled with high-performance liquid chromatography (HPLC) was developed. Advantages of such method may be counted as the mild working temperature during the synthesis, simplicity of extraction procedure, avoidance of leakage of template, time-saving, and high binding capacity and affinity. Several parameters affecting the extraction efficiency of the analytes including the sorbent mass, the pH of sample solution, the HAc percentage in the elute, and the desorption time were investigated. Under optimized conditions, the calibration graph was linear over the range of 11.4–4560 ng mL−1 with the limit of detection of 0.083 ng L−1. In addition, the higher enrichment factors (400-fold) and good recoveries (88.6–99.5%) with relative standard deviation (RSD) values less than 9.5% were achieved. Moreover, the developed extraction protocol simplified the process of traditional solid-phase extraction (SPE) provided the possibility for separation and enrichment of BPA from complicated food matrices.

Trace determination of lead(II) ions by using a magnetic nanocomposite of the type Fe3O4/TiO2/PPy as a sorbent, and FAAS for quantitation

The authors describe a magnetic nanoadsorbent consisting of magnetite nanoparticles coated first with titanium dioxide and then with polypyrrole (PPy). It is shown to be a viable material for magnetic solid-phase extraction of trace amount of Pb(II). The magnetic titanium dioxide nanoparticles were synthesized first and then modified with PPy via in-situ electropolymerization. The properties, morphology, and composition of the sorbent were characterized by FTIR, scanning electron microscopy, energy-dispersive X-ray analysis and vibrating sample magnetometry. The effects of pH value, extraction time, type and concentration of eluent, and of sample volume were optimized. Under the optimum conditions, the limit of detection (for S/N = 3) is 0.28 μg⋅L−1. The maximum adsorption capacity of the adsorbent is 126 mg⋅g−1 of Pb(II). The accuracy of the method was investigated by analysis of a Certified Reference Material and the obtained value (0.119 μg⋅g−1) was in good agreement with the certified value (0.120 μg⋅g−1). The method was successfully applied to the determination of Pb(II) in a gastropod and spiked environmental and marine water samples. It gave recoveries in the range from 94.4 to 103.1%.

Planar graphene oxide-based magnetic ionic liquid nanomaterial for extraction of chlorophenols from environmental water samples coupled with liquid chromatography–tandem mass spectrometry

A planar graphene oxide-based magnetic ionic liquid nanomaterial (PGO-MILN) was synthesized. The prepared PGO-MILN was characterized by transmission electronmicroscopy (TEM) and Fourier-transform infrared spectrometry (FTIR). The results of adsorption experiments showed that the PGO-MILN had great adsorption capacity for 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and pentachlorophenol (PCP). Based on the adsorption experimental data, a sensitive magnetic method for determination of the five CPs in environmental water samples was developed by an effective magnetic solid-phase extraction (MSPE) procedure coupled with high-performance liquid chromatography–tandem mass spectrometry (LC–MS/MS). The effects of main MSPE parameters including the solution pH, extraction time, desorption time, and volume of desorption solution on the extraction efficiencies had been investigated in detail. The recoveries ranged from 85.3 to 99.3% with correlation coefficients (r) higher than 0.9994 and the linear ranges were between 10 and 500ngL−1. The limits of detection (LODs) and limits of quantification (LOQs) of the five CPs ranged from 0.2 to 2.6ngL−1 and 0.6 to 8.7ngL−1, respectively. The intra- and inter- day relative standard deviations (RSDs) were in the range from 0.6% to 7.4% and from 0.7% to 8.4%, respectively. It was confirmed that the PGO-MILN was a kind of highly effective MSPE materials used for enrichment of trace CPs in the environmental water.

Graphene Oxide-Based Magnetic Solid Phase Extraction Combined with High Performance Liquid Chromatography for Determination of Patulin in Apple Juice

Magnetic solid phase extraction (MSPE) is a valuable tool for the extraction and preconcentration of analytes from environmental, food, and biological samples because of its convenience, promptness, and simplicity. In this study, a graphene oxide-based magnetic nanocomposite (MGO) was synthesized and characterized by various instrumental methods. An effective MSPE procedure coupled with high-performance liquid chromatography (MSPE-HPLC) was developed for the preconcentration and determination of the patulin (PAT) in apple juice samples. Critical experimental parameters of MSPE that could affect the extraction efficiencies, such as the amount of MGO, the pH, and ionic strength of the sample solution; the extraction time; and the desorption conditions, were investigated. After optimizing the conditions, the detection limit of this method provided was 2.3 μg/kg; the recoveries were in the range of 68.7–83.6 %, with relative standard deviations (RSDs) ranging between 1.8–8.7 %. It was confirmed that the graphene-based magnetic nanocomposite was a kind of effective MSPE material used for the PAT analyses in apple juice samples.

Rapid Determination of Trace Sulfonamides in Milk by Graphene Oxide-Based Magnetic Solid Phase Extraction Coupled with HPLC–MS/MS

A simple and rapid method based on magnetic solid-phase extraction (MSPE) combined with high-performance liquid chromatography coupled with triple quadrupole mass spectrometry (HPLC–MS/MS) was used for the determination of 15 sulfonamides from milk samples. The extraction and cleanup used a graphene oxide-based magnetic nanocomposite (Fe3O4@GO) as an adsorbent. Various experimental parameters that could affect the extraction efficiencies, such as the amount of Fe3O4@GO, the extraction time, the ionic strength of sample solution, and the type of eluent, were investigated. Under optimized experimental conditions, good linearity was observed in the range of 2.0 to 100.0 μg L−1 for all of the analytes, with correlation coefficients (R2) ranging from 0.994 to 0.999. The limits of detection for the method ranged between 0.02 and 0.13 μg L−1. Mean values of the relative standard deviation of intraday and interday precision ranging from 1.0 to 7.3 % and from 1.7 to 8.1 % were obtained, respectively. The average recoveries were between 73.4 and 97.4 % at three different spiked levels. It was confirmed that the Fe3O4@GO nanocomposite was an effective MSPE material for use in sulfonamide analyses in milk samples.

Determination of bisphenols in environmental water samples using polydopamine-coated magnetic Fe3O4 as a magnetic solid-phase extraction material coupled with high-performance liquid chromatography

Fe3O4@polydopamine composites were synthesized and used as a magnetic adsorbent to extract bisphenols from environmental water samples before determination using HPLC.

Development of novel magnetic solid phase extraction materials based on Fe3O4/SiO2/poly(acrylamide-N,N′-methylene bisacrylamide)-Pluronic L64 composite microspheres and their application to the enrichment of natamycin

Novel magnetic adsorbents based on Fe3O4/SiO2/poly(acrylamide-N,N'-methylene bisacrylamide) magnetic microspheres modified with non-ionic triblock copolymer surfactant were successfully prepared as a magnetic solid phase extraction adsorbent for the determination of trace natamycin in jam samples. The adsorbent was characterized by scanning electron microscopy, transmission electron microscopy, Fourier transformed infrared spectroscopy, vibrating sample magnetometer, and X-ray diffractometer analysis, confirming that Pluronic L64 was effectively functionalized on the magnetic materials. Various experimental parameters affecting the extraction capacity were investigated including adsorbent amount, extraction time, desorption time, sample pH, and ionic strength. For recovery evaluations, the jam samples were spiked at two concentration levels of 100 and 200μgkg(-1) of natamycin and the recovery values were in the range of 78.8-93.4%. The relative standard deviations (RSD) for the recoveries were less than 3.5%. The novel magnetic solid phase extraction method provided several advantages, such as simplicity, low environmental impact, convenient extraction procedure, and short analysis time when used for natamycin analysis.

Magnetic molecularly imprinted polymers synthesized by surface-initiated reversible addition-fragmentation chain transfer polymerization for the enrichment and determination of synthetic estrogens in aqueous solution.

Magnetic molecularly imprinted polymers have attracted significant interest because of their multifunctionality of selective recognition of target molecules and rapid magnetic response. In this contribution, magnetic molecularly imprinted polymers were synthesized via surface-initiated reversible addition addition-fragmentation chain transfer polymerization using diethylstilbestrol as the template for the enrichment of synthetic estrogens. The uniform imprinted surface layer and the magnetic property of the magnetic molecularly imprinted polymers favored a fast binding kinetics and rapid analysis of target molecules. The static and selective binding experiments demonstrated a desirable adsorption capacity and good selectivity of the magnetic molecularly imprinted polymers in comparison to magnetic non-molecularly imprinted polymers. Accordingly, a corresponding analytical method was developed in which magnetic molecularly imprinted polymers were employed as magnetic solid-phase extraction materials for the concentration and determination of four synthetic estrogens (diethylstilbestrol, hexestrol, dienestrol, and bisphenol A) in fish pond water. The recoveries of these synthetic estrogens in spiked fish pond water samples ranged from 61.2 to 99.1% with a relative standard deviation of lower than 6.3%. This study provides a versatile approach to prepare well-defined magnetic molecularly imprinted polymers sorbents for the analysis of synthetic estrogens in water solution.

Synthesis of magnetic framework composites for the discrimination of Escherichia coli at the strain level

Rapid and efficient characterization and identification of pathogens at the strain level is of key importance for epidemiologic investigations, which still remains a challenge. In this work, solvothermically Fe3O4-COOH@MIL-101 composites were fabricated by in situ crystallization approach. The composites combine the excellent properties of both chromium (III) terephthalate (MIL-101) and carboxylic-functionalized magnetite (Fe3O4-COOH) particles and possess the efficient peptides/proteins enrichment properties and magnetic responsiveness. Fe3O4-COOH@MIL-101 composites as magnetic solid phase extraction materials were used to increase the discriminatory power of MALDI-TOF MS profiles. BSA tryptic peptides at a low concentration of 0.25fmolμL−1 could be detected by MALDI-TOF MS. In addition, Fe3O4-COOH@MIL-101 composites were successfully applied in the selective enrichment of the protein biomarkers from bacterial cell lysates and discrimination of Escherichia coli at the strain level. This work provides the possibility for wide applications of magnetic MOFs to discriminate pathogens below the species level.

Amine-functional magnetic polymer modified graphene oxide as magnetic solid-phase extraction materials combined with liquid chromatography–tandem mass spectrometry for chlorophenols analysis in environmental water

A novel planar-structure amine-functional magnetic polymer modified graphene oxide nanocomposite (NH2-MP@GO) was synthesized. The properties were characterized by transmission electron microscopy (TEM) and Fourier-transform infrared spectrometry (FTIR). The obtained adsorption results showed that the NH2-MP@GO had great adsorptive ability toward five chlorophenols (CPs), including 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and pentachlorophenol (PCP). Based on these, an effective magnetic solid-phase extraction (MSPE) procedure coupled with high-performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) for the preconcentration and determination of the five CPs in environmental water samples was developed. Various experimental parameters that could affect the extraction efficiencies had been investigated in detail. Under the optimum conditions, the enrichment factors of the method for the target CPs were found to be 1000. The proposed method was successfully applied for the analysis of environmental water samples with recoveries ranging from 86.4 to 99.8% with correlation coefficients (R) higher than 0.9994. Good linearities were obtained ranging from 10 to 500ng/L for 2-CP, 5 to 500ng/L for 2,4-DCP, 2 to 500ng/L for 2,4,6-TeCP and 2,3,4,6-TeCP, and 1 to 500ng/L for PCP, respectively. The limits of quantitation for the five CPs were 0.6–9.2ng/L. It was confirmed that the planar-structure NH2-MP@GO was a kind of highly effective MSPE materials used for the trace CPs analyses.

Mixed hemimicelles solid-phase extraction based on ionic liquid-coated Fe3O4/SiO2 nanoparticles for the determination of flavonoids in bio-matrix samples coupled with high performance liquid chromatography

A novel magnetic solid-phase extraction (MSPE) method based on mixed hemimicelles of room temperature ionic liquids (RTILs) coated Fe3O4/SiO2 nanoparticles (NPs) was developed for simultaneous extraction of trace amounts of flavonoids in bio-matrix samples. A comparative study on the use of RTILs (C16mimBr) and CTAB-coated Fe3O4/SiO2 NPs as sorbents was presented. Owing to bigger adsorption amounts for analytes, RTILs-coated Fe3O4/SiO2 NPs was selected as MSPE materials and three analytes luteolin, quercetin and kaempferol can be quantitatively extracted and simultaneously determined coupled with high performance liquid chromatography (HPLC) in urine samples. No interferences were caused by proteins or endogenous compounds. Good linearity (R2>0.9993) for all calibration curves was obtained, and the limits of detection (LOD) for luteolin, quercetin and kaempferol were 0.10ng/mL, 0.50ng/mL and 0.20ng/mL in urine samples, respectively. Satisfactory recoveries (93.5–97.6%, 90.1–95.4% and 93.3–96.6% for luteolin, quercetin and kaempferol) in biological matrices were achieved. It was notable that while using a small amount of Fe3O4/SiO2 NPs (4.0mg) and C16mimBr (1.0mg), satisfactory preconcentration factors and extraction recoveries for the three flavonoids were obtained. To the best of our knowledge, this is the first time a mixed hemimicelles MSPE method based on RTILs and Fe3O4/SiO2 NPs magnetic separation has ever been used for pretreatment of complex biological samples.

Preparation and Application of Core-shell Magnetic Imprinted Nanoparticles for Bisphenol A

Abstract Magnetic molecularly imprinted polymers (MMIPs) for bisphenol A (BPA) were firstly prepared by three-step miniemulsion polymerization and were used as selective adsorbents for extraction of BPA in lake water. The MMIPs nanoparticles (NPs) possessed regular morphology and good monodispersion. The average diameter of MMIPs NPs was 123 nm with RSD of 4.9% (n = 50). The thickness of MIPs shell was about 10 nm. These MMIPs NPs could be rapidly separated by an external magnet within 1 min from solution. The saturated adsorption capacity of the MMIPs for BPA was 122.2 mg g−1, and the imprinting factor α was 3.5. Selective recognition experiment was performed by using β–estradiol, estriol and diethylstilbestrol as competitive compounds, and the separation factors for the experiment were 23.6, 8.8 and 3.7, respectively. MMIPs NPs as magnetic solid phase extraction material were successfully applied to determine BPA in lake water with satisfactory recoveries.

Development of novel molecularly imprinted magnetic solid-phase extraction materials based on magnetic carbon nanotubes and their application for the determination of gatifloxacin in serum samples coupled with high performance liquid chromatography

A novel composite imprinted material, on the basis of magnetic carbon nanotubes (MCNTs)-incorporated layer using gatifloxacin as a template, methacrylic acid as a functional monomer, and ethylene glycol dimethacrylate as a cross-linker, was successfully synthesized by a surface imprinting technique. Adsorption dynamics and a Scatchard adsorption model were employed to evaluate the adsorption process. The results showed that magnetic carbon nanotubes molecularly imprinted polymers (MCNTs@MIP) displayed a rapid dynamic adsorption and a high adsorption capacity of 192.7μg/mg toward GTFX. Applied MCNTs@MIP as a sorbent, a magnetic solid phase extraction method coupled with high performance liquid chromatography (MSPE-HPLC) was developed for the determination of GTFX in serum samples. The recoveries from 79.1±4.8% to 85.3±4.2% were obtained. MCNTs@MIP can not only be collected and separated fast by external magnetic field but also have high surface-to-volume ratio, outstanding mechanical properties and specific recognition toward template molecule. In addition, the MCNTs@MIP could be regenerated, which could be used for five cycles with lost of less than 7.8% of its recovery on average. These analytical results of serum samples display that the proposed method based on MCNTs@MIP is applicable for fast and selective extraction of therapeutic agents from biological fluids.

Preparation of hydrophilic carbon-functionalized magnetic microspheres coated with chitosan and application in solid-phase extraction of bisphenol A in aqueous samples

Hydrophilic carbon-functionalized magnetic microspheres coated with chitosan (Fe3O4@C@CHI) were synthesized for the first time. The hydrophilic carbonaceous layer on the Fe3O4 microspheres was formed by the hydrothermal reaction of Fe3O4 microspheres and glucose, and then chitosan was coated on surface of the carbon-functionalized microspheres by an easy zero-length reaction with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) as cross-linkers. The Fe3O4@C@CHI microspheres were spherical core–shell structure with uniform size at about 400nm. The microspheres had a high saturation magnetization of 60.22emug−1, which was sufficient for magnetic separation. The Fe3O4@C@CHI microspheres presented good hydrophilic property due to the abundant carboxyl and hydroxyl groups on the carbonaceous layer of the microspheres. The successful modification of chitosan on the surface of carbon-functionalized magnetic microspheres was validated by the adsorption of Eriochrome Black T (EBT). The prepared microspheres were applied as magnetic solid-phase extraction materials for extraction of bisphenol A (BPA) in aqueous samples. The extraction recoveries of spiked samples were in the range of 99.4–102.6% with low relative standard deviations of 2.8–3.9%. The results demonstrated that the novel Fe3O4@C@CHI microspheres were good candidate as magnetic SPE materials for extraction of analytes from aqueous samples.

Rapid magnetic solid-phase extraction based on magnetite/silica/poly(methacrylic acid–co–ethylene glycol dimethacrylate) composite microspheres for the determination of sulfonamide in milk samples

A novel magnetic solid-phase extraction (MSPE) sorbent, magnetite/silica/poly (methacrylic acid–co-ethylene glycol dimethacrylate) (Fe 3O 4/SiO 2/P(MAA-co-EGDMA)), was developed. This MSPE material was prepared by distillation–precipitation polymerization of MAA and EGDMA in the presence of Fe 3O 4/SiO 2 microspheres with the surface containing abundant reactive double bonds. The resultant sorbent material was characterized by elemental analysis, electron microscopy, X-ray diffraction and Fourier-transformed infrared spectroscopy. In this work, eleven sulfonamides (SAs) were selected as model analytes to validate the extraction performance of this new MSPE sorbent. Noticeably, the extraction can be carried out quickly, the extraction time for the SAs onto Fe 3O 4/SiO 2/P(MAA-co-EGDMA) sorbent can be clearly shortened to 0.5 min. The desorption solution of SAs was analyzed by LC–MS/MS, and the results showed that the recoveries of these compounds were in the range of 87.6–115.6%, with relative standard deviations ranging between 0.9% and 10.8%; the limit of detection were in the range of 0.5–49.5 ng/L.