Yan-Bo Luo

Magnetic retrieval of graphene: Extraction of sulfonamide antibiotics from environmental water samples

A new technique of retrieving graphene from aqueous dispersion was proposed in the present study. Two-dimensional planar graphene sheets were immobilized onto silica-coated magnetic microspheres by simple adsorption. The graphene sheets were used as adsorbent material to extract six sulfonamide antibiotics (SAs) from water samples. After extraction, they were conveniently separated from the aqueous dispersion by an external magnetic field. Under the optimal conditions, a rapid and effective determination of SAs in environmental water samples was achieved. The limits of detection for six SAs ranged from 0.09 to 0.16 ng/mL. Good reproducibility was obtained. The relative standard deviations of intra- and inter-day analysis were less than 10.7% and 9.8%, respectively.

Fast microextraction of phthalate acid esters from beverage, environmental water and perfume samples by magnetic multi-walled carbon nanotubes

In this work, magnetic carbon nanotubes (CNTs) were prepared by mixing the magnetic particles and multi-walled carbon nanotubes dispersed solutions. Due to their excellent adsorption capability towards hydrophobic compounds, the magnetic CNTs were used as adsorbent of magnetic solid-phase extraction (MSPE) to extract phthalate acid esters (PAEs), which are widely used in many consumable products with potential carcinogenic properties. By coupling MSPE with gas chromatography/mass spectrometry (GC/MS), a rapid, sensitive and cost-effective method for the analysis of PAEs was established. Our results showed that the limits of detection (LODs) of 16 PAEs ranged from 4.9 to 38 ng L(-1), which are much lower compared to the previously reported methods. And good linearities of the detection method were obtained with correlation coefficients (R(2)) between 0.9821 and 0.9993. In addition, a satisfying reproducibility was achieved by evaluating the intra- and inter-day precisions with relative standard deviations (RSDs) less than 11.7% and 14.6%, respectively. Finally, the established MSPE-GC/MS method was successfully applied to the determination of PAEs from bottled beverages, tap water and perfume samples. The recoveries of the 16 PAEs from the real samples ranged from 64.6% to 125.6% with the RSDs less than 16.5%. Taken together, the MSPE-GC/MS method developed in current study provides a new option for the detection of PAEs from real samples with complex matrices.

Rapid Magnetic Solid-Phase Extraction Based on Magnetic Multiwalled Carbon Nanotubes for the Determination of Polycyclic Aromatic Hydrocarbons in Edible Oils

In this study, magnetic multiwalled carbon nanotubes were fabricated by a simple method and applied to magnetic solid-phase extraction (MSPE) of eight heavy molecular weight polycyclic aromatic hydrocarbons (PAHs) including chrysene, benzo[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, dibenzo[a,h]anthracene and benzo[g,h,i]perylene from edible oil samples. Several parameters affecting the extraction efficiency were investigated, including the type and volume of desorption solvent, extraction and desorption time, washing solution and the amount of sorbent. Under the optimized conditions, a simple and effective method for the determination of PAHs in edible oils was developed by coupling with gas chromatography-mass spectrometry (GC-MS). The whole pretreatment process was rapid, and it can be accomplished within 10 min. The limits of quantitation for the target PAHs were found to be 0.34-2.9 ng/g. The recoveries in oil sample were in the range 87.8-122.3% with the RSDs less than 6.8% (intraday) and 9.6% (interday). This method was successfully applied to the analysis of PAHs in seven kinds of edible oils from local markets.

Graphene-polymer composite: extraction of polycyclic aromatic hydrocarbons from water samples by stir rod sorptive extraction

Due to the excellent mechanical, thermal and electrical properties, graphene/polymer composite is expected to have a variety of applications in analytical chemistry. In this study, a new poly(ethylene glycol dimethacrylate)/graphene composite was prepared by in situ polymerization. The new composite was used for the first time as the extraction coating of stir rod sorptive extraction for the preconcentration of polycyclic aromatic hydrocarbons (PAHs) from water samples. Because of the high specific surface area and π-π electrostatic stacking properties of graphene, the graphene-polymer composite showed higher extraction efficiencies towards most target PAHs from water samples than the neat polymer. Under the optimal conditions, a method for the determination of PAHs in water samples was proposed based on the combination of stir rod sorptive extraction (SRSE) and gas chromatography-mass spectrometry (GC-MS). The limit of detection (LODs) of the developed method for 16 PAHs ranged from 0.005 to 0.429 ng mL-1, depending on the compound. Good reproducibility of method was obtained as intra- and inter-day precisions, the relative standard deviations (RSDs) were less than 12.5% and 12.6%, respectively.

A magnetite/oxidized carbon nanotube composite used as an adsorbent and a matrix of MALDI-TOF-MS for the determination of benzo[a]pyrene

A magnetite/oxidized carbon nanotube composite, Fe(3)O(4)@SiO(2)/OCNT, was fabricated in a simple way, and it was successfully used as a magnetic solid-phase extraction sorbent and a significant matrix of the matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for the detection of benzo[a]pyrene (BaP).

Substrateless graphene fiber: A sorbent for solid-phase microextraction

In current study, a substrateless graphene fiber was successfully prepared by a simple hydrothermal strategy and used as solid-phase microextraction (SPME) sorbent. Five organochlorine pesticides (OCPs) were employed as model analytes to evaluate the performance of as-prepared graphene fiber. The results showed that the graphene fiber exhibited higher extraction efficiencies, higher thermal stability (up to 310°C), better reproducibility, and longer service life (more than 180 times reuse) than commercial fibers. In addition, the method for the determination of OCPs was proposed by coupling headspace (HS)-SPME technique with gas chromatography/electron capture detector (HS-SPME-GC/ECD). The proposed HS-SPME-GC/ECD method showed low limits of detection (0.83-11.5 ng/L), wide linear dynamic ranges (more than 2 orders of magnitude), and acceptable reproducibility (RSD<10.9%). Finally, the proposed method was successfully applied to the analysis of OCPs in environmental water samples with good recoveries (81-121%) and satisfactory precisions (RSD<9%).

Stir rod sorptive extraction with monolithic polymer as coating and its application to the analysis of fluoroquinolones in honey sample.

A stir rod sorptive extraction (SRSE) with monolithic polymer as coating was proposed to avoid the friction loss of coating during the stirring process. In our study, poly(2-acrylamide-2-methylpropanesulfonic acid-co-octadecyl methacrylate-co-ethylene glycol dimethacrylate) [poly(AMPS-co-OCMA-co-EDMA)] monolithic polymer was used as a coating of SRSE. The effect of concentration of porogen on SRSE performance was studied. Four fluoroquinolones (FQs) were selected as testing analytes to evaluate the extraction efficiency of SRSE. To achieve the optimum extraction conditions of SRSE towards FQs, several parameters, including extraction time, extraction temperature, stirring rate, sample solution pH and contents of inorganic salt in the sample solution were investigated. Under the optimized conditions of SRSE, a method for the determination of FQs in honey sample was proposed based on the combination of SRSE with liquid chromatography and electrospray ionization mass spectrometry (SRSE/LC/ESI-MS). The detection limits (LODs) of the proposed method for four FQs ranged from 0.06 to 0.14ng/g and the recoveries were in the range of 70.3-122.6% at different concentrations for honey samples. Good method reproducibility was found as intra- and inter-day precisions, yielding the relative standard deviations less than 11.9% and 12.4%, respectively. The results show that SRSE with poly(AMPS-co-OCMA-co-EDMA) monolithic polymer as coating possessed good extraction capacity towards FQs in honey samples. Finally, the monolithic polymer coated stir rod was demonstrated to be reused at least 60 times.

Facile fabrication of reduced graphene oxide-encapsulated silica: A sorbent for solid-phase extraction

In this study, a facile hydrothermal reduction strategy was developed for the preparation of reduced graphene oxide-encapsulated silica (SiO2@rGO). Compared with other conventional methods for the synthesis of SiO2@rGO, the proposed strategy endowed the obtained SiO2@rGO with larger amount of immobilized rGO. The prepared functionalized silica shows remarkable adsorption capacity toward chlorophenols (CPs) and peptides. When it was used as solid-phase extraction (SPE) sorbent, a superior recovery could be obtained compared to commercial sorbents, such as C18 silica, graphitized carbon black and carbon nanotubes. Based on these, the prepared material was used as SPE sorbent for the enrichment of CPs, and a method for the analysis of CPs in water samples was established by coupling SPE with high performance liquid chromatography-ultra violet detection (SPE-HPLC/UV). In addition, the obtained SiO2@rGO was further successfully extended to the enrichment of peptides in bovine serum albumin (BSA) digests.

An anionic exchange stir rod sorptive extraction based on monolithic material for the extraction of non-steroidal anti-inflammatory drugs in environmental aqueous samples

In this study, a stir rod sorptive extraction (SRSE) adsorbent material was prepared by coating poly(4-vinylpyridine-co-ethylene glycol dimethacrylate) [poly(VP-co-EDMA)] monolithic polymer on stir rod, and then applied to the extraction of three non-steroidal anti-inflammatory drugs (NSAIDs) in environmental aqueous samples. The preparation conditions of monolithic material such as the amount of porogen and the ratio of functional monomer to cross-linker were investigated. To achieve the best extraction efficiency, several parameters, including pH value of sample solution, salt concentration in sample matrix, desorption solvent, extraction time, and desorption time, were optimized. By combining SRSE and high performance liquid chromatography with ultraviolet detector, a SRSE-HPLC/UV method for the determination of NSAIDs in environmental aqueous samples was proposed successfully. The limits of detection (LODs) of the developed method for three NSAIDs ranged between 0.09 and 0.25 ng/mL. Good method reproducibility presented as intra- and inter-day precisions were also obtained with the relative standard deviations (RSDs) less than 8.7% and 9.8%, respectively.

Preparation of mesoporous silica embedded pipette tips for rapid enrichment of endogenous peptides

Mesoporous silica embedded pipette tips (mSiO2-Tips) were successfully prepared by a simple method and applied to rapid enrichment of endogenous peptides for the first time. The prepared mSiO2-Tips showed low back pressure when solvent was pipetted up and down. As a result, mSiO2-Tip could selectively trap peptides and exclude high-MW proteins simultaneously based on size-exclusion mechanism due to the uniform mesopore structure of the sorbent bed. The in-pipette-tip SPE approach was proved to be easy-operation, sensitive and fast (less than 2 min) for the analysis of peptides, which was further successfully applied in the efficient enrichment of peptides from human plasma.