Thoughtful design of a covalent organic framework with tailor-made polarity and pore size for the enrichment of bisphenols and their derivatives: Extraction performance, adsorption mechanism and toxicity evaluation.

A stable, reusable and cost-effective covalent organic framework (COF) with medium polarity was successfully decorated on Fe3O4. The Fe3O4@COF contained tailor-made polarity and pore size that fitted well with bisphenols and their derivatives (BPs). When coupling magnetic solid-phase extraction (MSPE) with high-performance liquid chromatography (HPLC) detection, the Fe3O4@COF featured efficient recognition and enrichment for BPs due to π-π stacking, C-H⋯π interactions, pore-filling effect, dispersion force and hydrophobic interactions. Under optimized conditions, calibration plots exhibited good linearity (5-1000 ng mL-1), and limits of detection (LOD) ranged from 0.15 to 0.39 ng mL-1. The method was successfully employed in quantifying BPs in authentic lake and river water samples with satisfactory recoveries ranging from 81.4% to 120%. Molecular dynamics simulation revealed extraction mechanisms, and a microscopic behavior related to the clustering property of the emerging brominated compounds was first discovered. Ecotoxicological assessments of target pollutants were conducted from multiple aspects, highlighting the harmfulness of the chemicals and the significance of the analytical method. The proposed methodology offered sensitive detection and quantification, which was beneficial for the timely tracking of the concentration, transportation and distribution of BPs to better explore their environmental behavior and tackle contamination problems in complex environmental matrices.

Room temperature fabrication of magnetic covalent organic frameworks for efficient enrichment of parabens in water.

A novel 4 + 2 covalent magnetic organic framework (COF) with core-shell structure was synthesized for the first time with N, N, N', N'-Tetrakis (4-aminophenyl)-1, 4- benzenediamine (TPDA) and 2, 6-Pyridinedicarboxaldehyde (PCBA) at room temperature. The synthesized magnetic TPDA-PCBA-COF has a large specific surface area and superparamagnetism, which makes it an ideal sorbent for trace analytes enrichment. To this end, we combined it with magnetic solid phase extraction (MSPE) to enrich trace parabens in environmental water. The parameters affecting the enrichment efficiency of magnetic solid phase extraction, such as the amount of Fe3O4@TPDA-PCBA-COF, extraction time, pH of samples, salt concentration, desorption solvent volume and desorption time, were optimized. A simple method for extraction and determination of parabens in water samples by MSPE combined with high performance liquid chromatography (HPLC) was established under optimized conditions. The validation results revealed that the linear ranges were at 1.0-5.0 × 102 ng mL-1 with R value between 0.9915 and 0.9999, the spiked recoveries were in the range of 82.8% to 99.9% and RSDs were lower than 10%. The method was further applied to the determination of parabens in water samples, with recoveries in the range of 82.2% to 110.0% and RSDs ≤ 7.7%. These results suggest that the magnetic TPDA-PCBA-COF could be used as a promising adsorbent for efficient extraction and quantitation of parabens in environmental water samples.

Fabrication of a core-shell porphyrin-based magnetic covalent organic framework for effective extraction of PCPs in a wide polarity range.

A novel porphyrin-based magnetic covalent organic framework (PCOF) was first reported by using a facile synthetic procedure. The Fe3O4@NH2@PCOF nanospheres were utilized to effectively extract personal care products in a wide polarity range (log Kow values from 1.96 to 7.60). The successful magnetic solid-phase extraction (MSPE) of target analytes could be ascribed to the sufficient oxygen-, nitrogen- and phenyl-containing functional groups of the COF layer, which are demonstrated to be of good compatibility with pollutants exhibiting different polarities by using molecular dynamics simulations, independent gradient model analysis and various characterizations. The MSPE extraction efficiency was enhanced by optimizing key parameters. The findings indicated that the method had a wide linearity range (1-500 ng mL-1 for parabens and UV filters) and low detection limits (0.4-0.9 ng mL-1 for parabens and 0.2-0.6 ng mL-1 for UV filters). The accuracy was reflected by recoveries ranging from 74% to 114%. Satisfactory intra- and inter-day precisions from 3.0% to 9.8% and 0.5%-9.1% were obtained. Overall, the proposed MSPE-HPLC method is accurate and reliable for identifying parabens as well as UV filters in wastewater and swimming pool water. The potential of the method for evaluating human exposure risk was unfolded.

Hydroxy-Containing Covalent Organic Framework Combined with Nickel Ferrite as a Platform for the Recognition and Capture of Bisphenols.

A hydroxy-containing covalent organic framework (COF) was successfully obtained via a simple nitrogen-purge synthetic procedure for the first time. The COF favored a serrated AA-stacking arrangement, which enhanced the stability compared with common AA or AB arrangements. To validate the potential of the COF in environmental applications, we decorated the COF onto NiFe2O4 and used the NiFe2O4@COF nanocomposite for magnetic solid-phase extraction of trace bisphenols (BPs). The parameters affecting extraction efficiencies were systematically optimized. Under the optimum extraction conditions, calibration plots showed good linearity (5.0-1.0 × 103 ng mL-1) for six BPs, and limits of detection varied from 0.14 to 0.73 ng mL-1. Molecular polarity indexes and molecular dynamics simulations revealed why the COF could efficiently recognize and capture BPs. An adsorption mechanism related to the interaction between BP clusters and the COF was discovered. Ecotoxicological assessment of BPs further unraveled the significance of the developed method for the timely tracking of the concentration, distribution, and migration of BPs in environmental media.

[Analysis of parabens in environmental water samples by covalent organic framework-based magnetic solid-phase extraction-high performance liquid chromatography].

Parabens are a class of antimicrobial preservatives that are widely used in cosmetics, pharmaceuticals, and food products because of their ease of production, antimicrobial effect, and low price. The widespread use of these parabens, poses potential risks to human health. Therefore, it is necessary to establish a simple and rapid method for the detection of parabens. The large number of substrate interferences in complex samples is an important factor affecting the sensitivity of analytical methods. Magnetic solid-phase extraction (MSPE) has received much attention because of its advantages of easy operation, short extraction time, small sample amount, low cost, and environmental friendliness. Covalent organic frameworks (COFs) with high crystallinity, high specific surface area, adjustable pore size, regular porosity, as well as high chemical and thermal stability are now widely used in separation and analysis. Therefore, a sample pretreatment method combining MSPE and COF for the analysis of parabens in complex matrices is very promising. A magnetic covalent organic framework, Fe3O4@TbBd, was successfully synthesized by the Schiff base reaction of 1,3,5-triformylbenzene (Tb) and benzidine (Bd) at room temperature using Fe3O4 nanoparticles as magnetic cores. Characterization by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) measurements, etc. revealed that the magnetic COF has high magnetic responsiveness, as well as good thermal and chemical stability, which make it an ideal adsorbent for the MSPE of parabens. Some factors related to the extraction efficiency, including the amount of adsorbent, extraction time, pH, desorption solvent, desorption time, and number of desorption were systematically investigated. A method involving MSPE and high performance liquid chromatography-ultraviolet detection (HPLC-UV) based on the Fe3O4@TbBd was developed for the determination of four parabens (ethylparaben, propylparaben, butylparaben, and benzylparaben) in environmental water samples. Under the optimal extraction conditions, the method showed good linearities. The limits of detection and limits of quantification were 0.2-0.4 µg/L and 0.7-1.4 µg/L for the four analytes, respectively. The recoveries at three spiked levels were in the range of 86.1%-110.8% with intra-day and inter-day RSDs of less than 5.5% and 4.9%, respectively. The method was successfully applied to the determination of parabens in East Lake water, Yangtze water, and domestic wastewater. Ethyl paraben and propyl paraben were detected in domestic wastewater at the levels of 1.8 µg/L and 0.4 µg/L, respectively. The recoveries of the parabens at different spiked levels ranged from 80.7% to 117.5%, with RSDs of 0.2%-8.8%. The method has good potential for the determination of parabens in environmental water samples because of its operational simplicity, short extraction time, high sensitivity, and environmental friendliness.

Efficient activation of peroxymonosulfate mediated by Co(II)-CeO2 as a novel heterogeneous catalyst for the degradation of refractory organic contaminants: Degradation pathway, mechanism and toxicity assessment.

A series of Co(II)-CeO2 mixed metal oxides were synthesized by a facile hydrothermal-calcination procedure for activating peroxymonosulfate (PMS) and degrading toxic and difficult biodegradable organics. Co(II)-CeO2 showed excellent degradation performance toward rhodamine B (RhB), toluidine blue, methylene blue and diclofenac. RhB is a refractory organic contaminant, and ecotoxicological evaluation unraveled its harmfulness to the biosphere. RhB was selected as the model pollutant to investigate catalytic mechanisms. Parameters affecting degradation performance were profoundly investigated, including Co:Ce feed ratio, initial pH, PMS dosage, catalyst dosage, RhB concentration, coexisting ions and reaction temperature. Reaction mechanisms were proposed based on density functional theory calculations and identifications of reactive oxygen species. Improvements have been achieved in seven aspects compared to previous studies, including 100% degradation ratio in both real water samples and each reuse of the catalyst, ultrafast degradation rate, cost-effectiveness of the catalyst, toxicity-attenuation provided by the developed degradation method, high degree of mineralization for the model pollutant, negligible leaching of active sites, and the enhancement of catalytic performance by utilizing trace leached cobalt, endowing the technique with broad applicability and prospect.

Preparation of beta-cyclodextrin based nanocomposite for magnetic solid-phase extraction of organic ultraviolet filters.

A simple and efficient analytical method for organic UV filters (UV-Fs) in environmental samples has been established in this study. Taking advantage of the hydrophobicity on the inner cavity, hydrophilicity on the outer wall, and host-guest interaction provided by beta-cyclodextrin, a core-shell magnetic extraction material was firstly synthesized by using a facile method. The extractant was utilized in magnetic solid-phase extraction of UV-Fs in complex environmental samples, including beach sand, sediment and river water samples, followed by the quantitation using high-performance liquid chromatography. A series of factors affecting extraction efficiencies of seven UV-Fs were profoundly optimized. Under the optimal conditions, the linear ranges were at 5.0-5.0 × 102 ng mL-1 for the UV-Fs with regression coefficients (r) at 0.9984-0.9998. The limits of detection were from 0.12 to 1.4 ng mL-1. The recoveries were in the range of 84.2-109%. Furthermore, the molecular dynamics simulations and independent gradient model analysis were applied to reveal the adsorption configuration and interaction mechanisms between target analytes and the sorbent.

An in vitro assessment for human skin exposure to parabens using magnetic solid phase extraction coupled with HPLC.

Skin contact was a significant source of human exposure to parabens during the use of personal care products. In this study, a novel and simple in vitro evaluation method for human skin exposure to parabens was established for the first time. Firstly, magnetic porous carbon (MPC) derived from discarded cigarette butts was prepared as an adsorbent of magnetic solid-phase extraction (MSPE), which provided a fast and efficient sample preparation method with satisfactory extraction performance for parabens in cosmetics and was easy to couple with high performance liquid chromatography. Secondly, the extraction conditions were optimized including the etching ratio of KOH, amount of MPC, extraction time, pH, salt concentration, desorption solvent volume and desorption time. Under the optimized conditions, the limits of detection were between 0.25 and 0.34 ng mL-1 and the spiked recoveries were in the range of 85.8-112.6%. Thirdly, the developed method was successfully employed to determine five typical parabens in real unspiked cosmetic samples, and two parabens were detected at a relatively high level. Then, the developed method was applied to in vitro assays. The absorbable dose of parabens in cream was investigated and in vitro experiments were further designed with agarose-simulated skin to demonstrate the penetration ability of parabens. In conclusion, these results indicated that parabens did have the risk of entering the body through the skin and the exposure was preferably no more than 3 h with skin contact.

Magnetic porous biochar as a renewable and highly effective adsorbent for the removal of tetracycline hydrochloride in water.

In this study, discarded cigarette butts were used as a precursor for preparing magnetic porous biochar with a facile annealing method. The magnetic porous biochar was applied to remove tetracycline hydrochloride (TCH) from aqueous solution. It exhibited excellent adsorption capacity for TCH, which was much higher than various similar materials reported. At the same time, the adsorption kinetics and adsorption isotherms of TCH were well fitted to the pseudo-second-order models and Freundlich models, respectively. The thermodynamics experiments proved that the adsorption on magnetic porous biochar was an endothermic reaction. Furthermore, the adsorption mechanism was explored, and the outstanding adsorption ability was mainly dependent on the pore filling effect, electrostatic interaction, and π-π interaction. By using the magnetic porous biochar, the real water samples were treated and high removal efficiency to TCH was obtained. What's more, the excellent reusability endowed the magnetic porous biochar with great potential as adsorbents for practical application.

Insights into the structure-performance relationships of extraction materials in sample preparation for chromatography.

Sample preparation is one of the most crucial steps in analytical processes. Commonly used methods, including solid-phase extraction, dispersive solid-phase extraction, dispersive magnetic solid-phase extraction, and solid-phase microextraction, greatly depend on the extraction materials. In recent decades, a vast number of materials have been studied and used in sample preparation for chromatography. Due to the unique structural properties, extraction materials significantly improve the performance of extraction devices. Endowing extraction materials with suitable structural properties can shorten the pretreatment process and improve the extraction efficiency and selectivity. To understand the structure-performance relationships of extraction materials, this review systematically summarizes the structural properties, including the pore size, pore shape, pore volume, accessibility of active sites, specific surface area, functional groups and physicochemical properties. The mechanisms by which the structural properties influence the extraction performance are also elucidated in detail. Finally, three principles for the design and synthesis of extraction materials are summarized. This review can provide systematic guidelines for synthesizing extraction materials and preparing extraction devices.

Rational design and synthesis of magnetic covalent organic frameworks for controlling the selectivity and enhancing the extraction efficiency of polycyclic aromatic hydrocarbons.

A series of three-dimensional magnetic covalent organic frameworks were designed and synthesized via monomer selection, coating thickness optimization, and composite strategy transformation. Their structure properties including morphology, functional group, surface area, and pore size were characterized. The relationship between the structural properties and analytical performance was systematically investigated by density functional theory calculation and batch extraction experiments for polycyclic aromatic hydrocarbons. It is proven that the extractant modified by monomer 1,4-phthalaldehyde provides a hizgh affinity for high molecule weight polycyclic aromatic hydrocarbons and the right balance between extraction and elution efficiency. The relationship between coating thickness and mass transfer rate of polycyclic aromatic hydrocarbons was studied by accurate tuning of coating layers via layer-by-layer method. A mathematical model was derived and employed to determine that two coating layers were sufficient to provide the highest extraction efficiency with the shortest equilibrium time. The extractants synthesized by two different composite strategies (layer-by-layer and one-step) show opposite selectivity for polycyclic aromatic hydrocarbons. After optimization of the extraction conditions, dispersed solid-phase extraction coupled with gas chromatography-mass spectroscopy method was developed providing a wide linear range (5-500 ng L-1), good linearity (R2 > 0.9923), high precision in intra-day (RSD% < 8.2%) and inter-day (RSD% < 12.3%) detection, and low detection limits (1.5-15.1 ng L-1). The method was applied to the simultaneous determination of 16 polycyclic aromatic hydrocarbons with acceptable recoveries, which were 87-109% for groundwater, 83-116% for East Lake water, and 82-116% for Yangtze River water samples.

An innovative in vitro assay to study the effects of aromatic pollutants on porphyrin systems.

Interactions between aromatic pollutants (APs) and porphyrin nucleus as physiological receptors have a significant effect on biological functions of porphyrin-based systems in organism. However, the details on the interaction at molecule level are still elusive. Herein, interaction mechanisms between two typical APs (methylene blue, MB and benzo[a]pyrene, B[a]P) and meso-tetra (4-carboxyphenyl) porphine (TCPP) as physiological receptors were systematically investigated. Adsorption behaviors of TCPP to B[a]P was dominated by pi-pi interaction, while interaction between TCPP and MB coupled with a multi-force field including hydrophobic, pi-pi, electrostatic, and H-bonding interactions. The relative contributions of these four forces obeyed an order: H-bonding > pi-pi > electrostatic > hydrophobic, regardless of the pH value and the initial concentration of MB. H-bonding assisted by hydrogen/hydroxide ion was the most influential force. According to the effect of pH and temperature, organisms exposed to cellular environment with high alkalinity and high temperature might uptake more APs molecules with chemical properties similar to MB and suffered greater health risks. In detail, APs might replace amino acid molecules surrounding porphyrin and change the distortion type of porphyrin molecule, and then affect biological functions of porphyrin and related proteins. This study facilitates a better understanding of potential toxicity of organisms in contaminated environment.

Net-like mesoporous carbon nanocomposites for magnetic solid-phase extraction of sulfonamides prior to their quantitation by UPLC-HRMS.

A net-like mesoporous carbon nanocomposite (MCN) was hydrothermally prepared by using filter paper as the raw material. The MCN contains magnetic nanoparticles of type Fe3O4 which result from the addition of Fe(NO3)3·9H2O during synthesis. The MCN was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman spectra, Brunauer-Emmett-Teller methods and vibrating sample magnetometry. The MCN is shown to be a viable material for magnetic solid-phase extraction of trace sulfonamides (SAs) including sulfadiazine, sulfapyridine, sulfamerazine, sulfamethazine, sulfamethizole, sulfamethoxypridazine, sulfachloropyridazine and sulfadimethoxine. Following desorption with acetone containing 0.5% ammonia, the SAs were quantified by UPLC with high-resolution mass spectrometric detection. With sulfamethazine as an example, the adsorption equilibrium configurations and the major interaction mechanism between SAs and the MCN were calculated by using density functional theory. Under the optimal conditions, the calibration plots are linear in the 0.05-10 ng·mL-1 SA concentration ranges. The limits of detection are between 7.2 and 13.6 ng·L-1. The recoveries from spiked samples ranged from 79 to 107%, with relative standard deviations of <9.9%. Graphical abstractSchematic representation of nanocomposite preparation, adsorption mechanism of sulfonamide and magnetic solid-phase extraction (MSPE) for sulfadiazine (SDZ), sulfapyridine (SPD), sulfamerazine (SMR), sulfamethazine (SMZ), sulfamethizole (SMT), sulfamethoxypridazine (SMP), sulfachloropyridazine (SCP) and sulfadimethoxine (SDMX). Quantification was accomplished by UPLC with high-resolution mass spectrometric detection.

Profiling free fatty acids in edible oils via magnetic dispersive extraction and comprehensive two-dimensional gas chromatography-mass spectrometry.

The analysis of free fatty acids (FFAs) in edible oils can provide important information for quality control and oil authentication. Herein, we report the comprehensive profiling of FFAs in edible oils via magnetic dispersive extraction combined with comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC-MS). A magnetic extractant was designed for dispersive extraction of FFAs. The extraction conditions were carefully optimized. To assess the extraction method, we first use the method for analysis of 7 targeted FFAs. The limits of detection range from 5.6 to 25.8 ng g-1, and the recoveries in oil samples are 81%-107%. We then performed comprehensive profiling of untargeted FFAs in oil by combining the extraction method with GC × GC-MS. A total of 64 FFAs were identified positively or putatively. The proposed method can provide FFA fingerprint data to guide the processing, storage and authentication of edible oils.

Eco-friendly and facile one-step synthesis of a three dimensional net-like magnetic mesoporous carbon derived from wastepaper as a renewable adsorbent.

Millions of tons of paper and its derivatives are annually wasted without being recycled and reused. To promote the comprehensive utilization of resources and eco-friendly preparation, waste filter paper, printer paper, and napkins were chosen as carbon sources to one-step synthesize three types of three dimensional (3D) net-like magnetic mesoporous carbon (MMC) by an eco-friendly and low-cost method. These mesoporous (3.90-7.68 nm) composites have a high specific surface area (287-423 m2 g-1), well-developed porosity (0.24-0.74 cm3 g-1) and abundant oxygen-containing functional groups. Compared to the other two composites, the adsorbent derived from filter paper showed the highest adsorption capacity towards methylene blue (MB) (q max = 332.03 mg g-1) and rhodamine B (RhB) (q max = 389.59 mg g-1) with a high adsorption rate (<5 min). According to the effect of pH value on adsorption capacity, and combining the analysis of Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy, the main adsorption mechanisms can be summarized as hydrogen bonds, electrostatic interactions, and π-π interaction. Besides, the occurrence of redox reactions between Fe2+/Fe0 and dye cannot be ignored. Finally, experiments on reusability were performed. They showed that the 3D net-like MMC could be easily regenerated and still maintained a removal efficiency of above 80% for RhB and 90% for MB after five cycles.

Hydrothermally tailor-made chitosan fiber for micro-solid phase extraction of petroleum acids in crude oils.

Tailor-made chitosan fiber was prepared via hydrothermal treatment to serve as a micro-solid phase extraction (micro-SPE) sorbent for the analysis of petroleum acids (PAs) in crude oils. Chitosan fiber, which is commercial and cheap, has a diameter of about 10 µm and a length of a few centimeters. The fibrous property of the sorbent enables the micro-SPE to deal with viscous crude oil samples because of the low back-pressure during extraction, while the abundant hydroxyl groups and amino groups on the surface of chitosan fiber can provide high density of specific sites for adsorption of PAs. Moreover, it was found that hydrothermal treatment at certain conditions could tune the surface properties of chitosan fiber, leading to significant improvement of the capacity of the fiber in adsorption of PAs. Using hydrothermally treated chitosan fiber as sorbent, the micro-SPE was applied to the determination of PAs in crude oils, with the advantages of easy-operation, rapidness and high sensitivity (the limits of detection range from 0.7 ng/g to 5.4 ng/g). Furthermore, coupled with comprehensive two dimensional gas chromatography-mass spectrometry (GC × GCMS), the treated chitosan fiber packed micro-SPE method showed a great potential for comprehensive profiling of PAs in crude oils.

Porphyrin-based magnetic nanocomposites for efficient extraction of polycyclic aromatic hydrocarbons from water samples.

Stable and reusable porphyrin-based magnetic nanocomposites were successfully synthesized for efficient extraction of polycyclic aromatic hydrocarbons (PAHs) from environmental water samples. Meso-Tetra (4-carboxyphenyl) porphyrin (TCPP), a kind of porphyrin, can connect the copolymer after amidation and was linked to Fe3O4@SiO2 magnetic nanospheres via cross-coupling. Several characteristic techniques such as field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectrometry, vibrating sample magnetometry and a tensiometer were used to characterize the as-synthesized materials. The structure of the copolymer was similar to that of graphene, possessing sp2-conjugated carbon rings, but with an appropriate amount of delocalized π-electrons giving rise to the higher extraction efficiency for heavy PAHs without sacrificing the performance in the extraction of light PAHs. Six extraction parameters, including the TCPP:Fe3O4@SiO2 (m:m) ratio, the amount of adsorbents, the type of desorption solvent, the desorption solvent volume, the adsorption time and the desorption time, were investigated. After the optimization of extraction conditions, a comparison of the extraction efficiency of Fe3O4@SiO2-TCPP and Fe3O4@SiO2@GO was carried out. The adsorption mechanism of TCPP to PAHs was studied by first-principles density functional theory (DFT) calculations. Combining experimental and calculated results, it was shown that the π-π stacking interaction was the main adsorption mechanism of TCPP for PAHs and that the amount of delocalized π-electrons plays an important role in the elution process. Under the optimal conditions, Fe3O4@SiO2-porphyrin showed good precision in intra-day (<8.9%) and inter-day (<13.0%) detection, low method detection limits (2-10 ng L-1), and wide linearity (10-10000 ng L-1). The method was applied to simultaneous analysis of 15 PAHs with acceptable recoveries, which were 71.1%-106.0% for ground water samples and 73.7%-107.1% for Yangtze River water samples, respectively.

Magnetic extractant with an Fe3O4@SiO2 core and aqueous ammonia coating for microextraction of petroleum acids.

Magnetic aqueous ammonia (MAA) was prepared as a magnetic extractant for dispersive microextraction of petroleum acids (PAs). The amount of extractant in MAA was custom-made by a simple approach. In the MAA composed of an aqueous ammonia coating and Fe3O4@SiO2 core, the coating is a base extractant that can selectively extract acids, while the magnetic core serves as a support to achieve dispersion as well as rapid magnetic retrieval of the extractant during the extraction processes. This is the first use of reusable, stable and modifiable Fe3O4@SiO2 as a support instead of bare Fe3O4 in a magnetic particle assisted dispersive liquid-liquid microextraction technique. The parameters that affect extraction efficiency were investigated. The sampling step as well as the desorption step can be completed in 2 min. The linear ranges are 5-5000 ng g-1, while the limits of quantification range from 2.5 to 6.2 ng g-1. The recoveries in spiked crude oil samples are in the range of 79.1% to 112.1% with relative standard deviations less than 11.3% (intra-day) and 13.4% (inter-day). Finally, the proposed method was applied to the analysis of PAs in diluted crude oils with different maturities. In comparison to the existing methods for extraction of PAs, the proposed method provides superior performances including high throughput (12-well plate), high degree of sample clean-up, and low consumption of separation material, solvent and time.

Determination of diamondoids in crude oils using gas purge microsyringe extraction with comprehensive two dimensional gas chromatography-time-of-flight mass spectrometry.

Based on a homemade device, gas purge microsyringe extraction (GP-MSE) of crude oil samples was developed for the first time. As a simple, fast, low-cost, sensitive and solvent-saving technique, GP-MSE provides some outstanding advantages over the widely used sample preparation methods for crude oils such as column chromatography (ASTM D2549). Several parameters affecting extraction efficiency were optimized, including extraction temperature, extraction time, extraction solvent, condensing temperature and purge gas flow rate. With the optimized GP-MSE conditions, several real crude oil samples were extracted, and trace diamondoids were determined using comprehensive two dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS). In total, more than 100 diamondoids were detected and 27 marker compounds were identified and quantified accurately. The limits of detection (LODs, S/N=3) were less than 0.08µg/L for all diamondoids. The relative standard deviation (RSD) was below 8%, ranging from 1.1 to 7.6%. The linearity of the developed method was in the range of 0.5-100.0µg/L with correlation coefficients (R2) more than 0.996. The recoveries obtained at spiking 50µg/L were between 81 and 108% for diamondoids in crude oil samples. The developed method can also be extended to the analysis of other components in crude oils and other complex matrices.

Synthesis of Polyethylenimine Functionalized Mesoporous Silica for In-Pipet-Tip Phosphopeptide Enrichment.

Synthesis of functionalized mesoporous silica material with large particle size remains a chanllenge. In this work, polyethylenimine (PEI) functionalized mesoporous silica (PFMS) with particle size as large as 100 µm was successfully synthesized by a facile method. In the synthesis process, PEI served as four roles simultaneously, including functionalized reagent, alkaline catalyst, template for particle formation, and pore-structure-directing agent. The surface areas of the products were higher than 260 m2/g. Benefiting from the large particle size and high surface area, PFMS was packed in a pipet tip to fabricate a convenient and miniaturized solid phase extraction apparatus for sample preparation. Additionally, based on the extremely abundant basic sites in the organic units of PFMS, the in-pipet-tip system was used as an anion-exchanger for phosphopeptide enrichment. The specificity of the developed method was investigated by capture of phosphopeptides from tryptic digests of standard protein mixtures, tryptic digests of nonfat milk, and human serum. Furthermore, the method was utilized to analyze phosphopeptides in tryptic digests of rat brain lysate, and 2251 unique phosphopeptides were successfully detected.