Jianqiao Xu

Application of nanomaterials in sample preparation.

Nanotechnology is one of the most important trends in material science. Due to the ultra-small size, nanomaterials possess unique physical and chemical properties. In this review, we summarized and discussed the recent applications of different nanomaterials, including metallic nanoparticles, metal organic frameworks (MOFs) materials, carbonaceous nanomaterials and siliceous nanoparticles, in sample preparation techniques.

Exceptional Hydrophobicity of a Large-Pore Metal–Organic Zeolite

Porous materials combining high hydrophobicity, large surface area, as well as large and uniform pore size are very useful but rare. The nanoporous zeolitic metal azolate framework, RHO-[Zn(eim)2] (MAF-6, Heim = 2-ethylimidazole), is an attractive candidate but thought to be unobtainable/unstable. In this work, the supramolecular isomerism of [Zn(eim)2] is thoroughly studied using a rapid solution mixing reaction of [Zn(NH3)4](OH)2 and Heim, which enables MAF-6 with high crystallinity, purity, and thermal/chemical stabilities to be synthesized in large quantity. Gas and vapor adsorption isotherms, gas chromatography, and water contact angle measurements, as well as transient breakthrough and molecular dynamics simulations show that MAF-6 exhibits large surface area (langmuir surface area 1695 m(2) g(-1)), pore volume (0.61 cm(3) g(-1)), pore size (d = 18.4 Å), and aperture size (d = 7.6 Å) with high hydrophobicity on both the internal pore and external crystal surfaces. It can barely adsorb water or be wetted by water (contact angle 143°) but readily adsorb large amounts of organic molecules including methanol, ethanol, mesitylene, adamantane, C6-C10 hydrocarbons, xylene isomers, and saturated/unsaturated analogues such as benzene/cyclohexene/cyclohexane or styrene/ethylbenzene. It can also separate these organic molecules from each other as well as from water by preferential adsorption/retention of those having higher hydrophobicity, lipophilicity, or oil/water partition coefficient. These properties are very different with other porous materials such as SOD-[Zn(mim)2] (Hmim = 2-methylimidazole, MAF-4/ZIF-8) with a hydrophobic pore surface but a hydrophilic crystal surface and small aperture size.

Applications of in vivo and in vitro solid-phase microextraction techniques in plant analysis: A review.

As a very popular sample preparation technique, solid-phase microextraction (SPME) coupled with various analytical instrumentation, has been widely used for the determination of trace levels of different plant compounds, such as volatile organic compounds (VOCs) emitted from the different plant organs, and environmental contaminants in plants. In this review, recent applications of in vitro and in vivo SPME in plant analysis are discussed and summarized according to the different organs of plants, including fruits, flowers, leaves, stems, roots and seeds, and the whole plant as well. Future developments and applications of SPME in plant analysis, especially in vivo sampling approaches, are also prospected.

In Vivo Tracing Uptake and Elimination of Organic Pesticides in Fish Muscle

Bioconcentration factors (BCFs) measured in the laboratory are important for characterizing the bioaccumulative properties of chemicals entering the environment, especially the potential persistent organic pollutants (POPs), which can pose serious adverse effects on ecosystem and human health. Traditional lethal analysis methods are time-consuming and sacrifice too many experimental animals. In the present study, in vivo solid-phase microextraction (SPME) was introduced to trace the uptake and elimination processes of pesticides in living fish. BCFs and elimination kinetic coefficients of the pesticides were recorded therein. Moreover, the metabolism of fenthion was also traced with in vivo SPME. The method was time-efficient and laborsaving. Much fewer experimental animals were sacrificed during the tracing. In general, this study opened up an opportunity to measure BCFs cheaply in laboratories for the registering of emerging POPs and inspecting of suspected POPs, as well as demonstrated the potential application of in vivo SPME in the study of toxicokinetics of pollutants.

Bioinspired Polydopamine Sheathed Nanofibers for High-Efficient in Vivo Solid-Phase Microextraction of Pharmaceuticals in Fish Muscle

In this study, electrospun nanofibers were used as solid-phase microextraction (SPME) fiber coatings after substituting the water-soluble sheath of the emulsion electrospun polystyrene (PS)@Plurinic F-127 core-sheath nanofibers with biocompatible and water-stable polydopamine (PDA) and subsequently being appropriately cross-linked with glutaraldehyde (GA) to enhance the strength of the electrospun architecture. The novel custom-made PS@PDA-GA coating was wettable in aqueous solutions and thus exhibited much higher extraction efficiency than the nonsheathed PS nanofiber coating and the thicker polydimethylsiloxane (PDMS) coating. The novel coating also possessed excellent stability (relative standard deviations (RSDs) less than 7.3% for six sampling-desorption cycles), interfiber reproducibility (RSDs less than 14.3%), and antibiofouling ability, which were beneficial for in vivo sampling. The PS@PDA-GA fiber was used to monitor pharmaceuticals in dorsal-epaxial muscle of living fish, and satisfactory sensitivities with the limits of detection in the range of 1.1 (mefenamic acid) to 8.9 (fluoxetine) ng·g(-1) and comparable accuracies to liquid extraction were achieved. In general, this study explored a convenient and effective method to sheath nanofibers for high-efficient in vivo SPME of analytes of interest in semisolid tissues.

Exploitation of a microporous organic polymer as a stationary phase for capillary gas chromatography.

Microporous organic polymers (MOPs) have emerged as a new class of functional porous materials with unique characteristics and potential uses in diverse areas. However, the field of MOPs for gas chromatographic (GC) separations has not been well explored. Herein, a MOP namely KAPs-1 was dynamic coated onto a capillary column for the first time. The fabricated column exhibited a nonpolar nature and the column efficiency for n-dodecane was up to 7769 plates m(-1). The KAPs-1 coated column showed high GC separation performance for a series of volatile organic compounds (VOCs) including the challenging ethylbenzene and xylene isomers, which could not be resolved at baseline on the commercial 5% phenyl polysiloxane stationary phase. Moreover, the relative standard deviations for five replicate determinations of the studied analytes were 0.0-0.6%, 0.9-3.2%, 1.1-5.9%, 0.8-3.7% for retention time, peak area, peak height and peak width, respectively. To investigate the interaction between some analytes and the stationary phase, thermodynamic and kinetic parameters were also evaluated. The results of this study show it is very promising to utilize MOPs as stationary phases for capillary GC.

Polyelectrolyte Microcapsules Dispersed in Silicone Rubber for in Vivo Sampling in Fish Brains.

Direct detection of fluoxetine and its metabolite norfluoxetine in living fish brains was realized for the first time by using a novel solid-phase microextraction fiber, which was prepared by mixing the polyelectrolyte in the oligomer of silicone rubber and followed by in-mold heat-curing. The polyelectrolyte was finally encased in microcapsules dispersed in the cured silicone rubber. The fiber exhibited excellent interfiber reproducibility (5.4-7.1%, n = 6), intrafiber reproducibility (3.7-4.6%, n = 6), and matrix effect-resistant capacity. Due to the capacity of simultaneously extracting the neutral and the protonated species of the analytes at physiological pH, the fiber exhibited high extraction efficiencies to fluoxetine and norfluoxetine. Besides, the effect of the salinity on the extraction performance and the competitive sorption between the analytes were also evaluated. Based on the small-sized custom-made fiber, the concentrations of fluoxetine and norfluoxetine in the brains of living fish, which were exposed to waterborne fluoxetine at an environmentally relevant concentration, were determined and found 4.4 to 9.2 and 5.0 to 9.2 times those in the dorsal-epaxial muscle. The fiber can be used to detect various protonated bioactive compounds in living animal tissues.

Disposable solid-phase microextraction fiber coupled with gas chromatography-mass spectrometry for complex matrix analysis

Recent developments of solid-phase microextraction (SPME) in biological and environmental analysis calls for robust and low-cost fibers that are prone to batch preparation with good reproducibility. However, the expensive commercial fibers and low reproducible home-made fibers cannot fully cater these requirements. In the present study, an extremely low-cost (less than one dollar) SPME fiber with good intra-fiber (RSDs% ≤ 1.6%, n = 6) and inter-fiber reproducibility (RSDs% ≤ 6.2%, n = 6) was prepared by mounting a piece of commercially available polydimethylsiloxane (PDMS) tubing on a stainless steel wire with epoxy glue. This configuration was stable for more than 100 extraction/thermal desorption cycles. In addition, compared with previously used thicker PDMS fiber, the capability of direct thermal desorption in gas chromatograph of the present fiber not only simplified the sample preparation process but also enhanced the analysis sensitivity. Excellent inter-fiber reproducibility and low cost even made the fiber disposable when used in complex matrices.

Hierarchical Graphene coating for highly sensitive solid phase microextraction of organochlorine pesticides.

Graphene, a novel class of carbon nanostructures, has received great attention as sorbents due to its fascinating structures, ultrahigh specific surface area, and good extraction ability. In this paper, a new type of hierarchical graphene was synthesized through employing a mild and environment-friendly method. Such 3D interconnected graphene own a high specific surface area up to 524m(2)g(-1), which is about 2.5 fold larger than the graphene, since the synthetic material has interlayer pores between nanosheets and in-plane pores. Then a superior solid-phase microextraction fiber was fabricated by sequentially coating the stainless steel fiber with silicone sealant film and hierarchical graphene powder. Since the novel hierarchical graphene possessed large surface area and good adsorption property, the as-prepared fiber exhibited good extraction properties of the organochlorine pesticides (OCPs). As for the analytical performance, the as-prepared fiber achieved low detection limits (0.08-0.80ngL(-1)) and wide linearity (10-30,000ngL(-1)) under the optimal conditions. The repeatability (n=5) for single fiber were between 5.1% and 11%, while the reproducibility (n=3) of fiber-to-fiber were range from 6.2% to14%. Moreover, the fiber was successfully applied to the analysis of OCPs in the Pearl River water.

Bioinspired Polyelectrolyte-Assembled Graphene-Oxide-Coated C18 Composite Solid-Phase Microextraction Fibers for In Vivo Monitoring of Acidic Pharmaceuticals in Fish

A novel solid-phase microextraction (SPME) fiber was prepared by gluing poly(diallyldimethylammonium chloride) (PDDA) assembled graphene oxide (GO)-coated C18 composite particles (C18@GO@PDDA) onto a quartz fiber with polyaniline (PANI). The fiber surface coating was sequentially modified with bioinspired polynorepinephrine, which provided a smooth biointerface and makes the coating suitable for in vivo sampling. The novel custom-made coating was used to extract acidic pharmaceuticals, and high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) was employed for analysis. The custom-made coating exhibited a much higher extraction efficiency than the previously used commercial polydimethylsiloxane (PDMS) and polyacrylate (PA) coatings. The custom-made coating also possessed satisfactory stability (the relative standard deviations (RSDs) ranged from 1.60% to 10.3% for six sampling-desorption cycles), interfiber reproducibility (the RSDs ranged from 2.61% to 11.5%), and resistance to matrix effects. The custom-made fibers were used to monitor the presence of acid pharmaceuticals in dorsal-epaxial muscle of living fish, and satisfactory sensitivities (limits of detection ranged from 0.13 ng/g to 7.56 ng/g) were achieved. The accuracies were verified by the comparison with liquid extraction. Moreover, the novel fibers were successfully used to monitor the presence of acidic pharmaceuticals in living fish, which demonstrated that the custom-made fibers were feasible for possible long-term in vivo continuous pharmaceutical monitoring.