Showing papers in "Journal of Chromatography A in 2020"

A critical review of molecularly imprinted polymers for the analysis of organic pollutants in environmental water samples.

Abstract: Molecularly imprinted polymers (MIPs) with tailor-made recognition sites are used in water analysis for selective sample pretreatment before quantitation. The exceptional performance of MIPs with reduced interferences and matrix effects during sample preparation has resulted in selective and precise analytical methods by enhancing chromatographic separation and detection. MIPs are fabricated using a varying range of synthetic procedures and used as the adsorptive phase in solid phase extraction (SPE), dispersive solid phase extraction (DSPE), solid phase microextraction (SPME), stir bar sorptive extraction (SBSE), and membrane-based extraction techniques. In this paper, a comprehensive review of MIP technologies reported in the literature for water analysis is provided. MIPs are critically evaluated using key performance criteria, such as adsorption capacity, imprinting factor, chromatographic retention factor, and cross-selectivity. The recent advances of MIP technologies including the preparation protocols, applications and developments are discussed. Additionally, the performance of MIPs which can be improved by optimizing the composition of the polymeric network is reviewed regarding the characteristics of rebinding medium. The limitations of MIPs for water analysis, especially restricted selectivity for water soluble analytes, material wettability, and MIP inhomogeneity are discussed by providing the possible solutions. Finally, some novel applications and prospects for online, rapid and direct analysis of environmental samples using MIPs are included.

A ferrofluidic hydrophobic deep eutectic solvent for the extraction of doxycycline from urine, blood plasma and milk samples prior to its determination by high-performance liquid chromatography-ultraviolet.

Abstract: The ferrofluid phase was prepared according to mixing magnetic nanoparticle and the hydrophobic deep eutectic solvent as a green microextraction solvent. This new composite was applied for vortex-assisted dispersive liquid–liquid microextraction (VA-HDES-ferrofluid-DLLME) of doxycycline (DOC) residual extraction and determined through high-performance liquid chromatography-ultraviolet (HPLC-UV). The characterization of magnetic nanoparticle was investigated by XRD, TEM and FESEM. The dependency of DOC microextraction to main variables and their interaction and find optimum points were undertaken using response surface methodology with either central composite design (CCD). Thus, the optimum pH, ionic strength, ferrofluid volume and vortex time for DOC extraction are determined to be 3.0, 4%w/v, 150 μL and 7 min, respectively. According to this condition, linear response is found to be greater than 10–400 ng mL−1, with a correlation coefficient of 0.983. The detection and quantification limits are 3.6 and 8.5 ng mL−1, while the repeatability and reproducibility as precision criteria (RSD%) are 3.74% and 4.15%, respectively. The DOC recoveries in all of the urine, blood plasma and milk samples are between 86.70 and 97.48%, with RSD% lower than 5.72%.

Quadruplex stable isotope derivatization strategy for the determination of panaxadiol and panaxatriol in foodstuffs and medicinal materials using ultra high performance liquid chromatography tandem mass spectrometry.

Abstract: This work proposed a novel strategy based on quadruplex stable isotope derivatization for sensitive, accurate, speedy and green determination of panaxadiol (PD) and panaxatriol (PT). This strategy integrated with ultrasound-assisted dispersive liquid-liquid microextraction, microwave-assisted derivatization, and magnetic graphene oxide dispersive solid phase extraction as efficient sample pretreatment techniques, coupling with ultra-high performance liquid chromatography tandem mass spectrometry detection in multiple reaction monitoring mode for the analytical purpose of high-throughput, sensitivity, selectivity, green and accuracy. Quadruplex mass spectrometry sensitizing derivatization reagents, 3-N-(D0-/D3-methyl-, and D0-/D5-ethyl-)-2′-carboxyl chloride rhodamine 6 G, were designed, synthesized and applied for the high-throughput derivatization of hydroxyl‑containing PD and PT for the first time. The analogue derivatives of PD and PT standards using 3-N-propyl-2′-carboxyl chloride rhodamine 6 G as derivatization reagent were employed as the internal standards for the mass spectrometry quantitation to minimize matrix effect. All rhodamine 6 G derivatives of PD and PT were easily and selectively adsorbed by magnetic graphene oxide for efficient magnetic dispersive solid phase extraction before injection. Parameters of (micro-) extractions, derivatization and liquid chromatography-mass spectrometry conditions were all optimized in details. Method validation results consisting of linearity, accuracy, precision, repeatability, matrix effect, stability and limits of detection (LODs, 0.02 ng/mL for PD and 0.03 ng/mL for PT) were determined. The analytical performance of this method benefited from efficient integration of suitable sample pretreatment techniques and characteristic structure of rhodamine 6 G with four mass tags in derivatization reagents. The developed and validated method has been applied to the quantitation of PD and PT for the quality assessment of related foodstuffs and traditional Chinese medicinal materials.

Sulphonate functionalized covalent organic framework-based magnetic sorbent for effective solid phase extraction and determination of fluoroquinolones.

Abstract: Most of the reported covalent organic frameworks (COFs) are hydrophobic, limiting their adsorption application in sample pretreatment field. In this work, sulphonate functionalized magnetic covalent organic frameworks (COFs) composites were first synthesized by loading gold nanoparticles on Fe3O4@COF(TpBD) surface and then functionalized by sodium 3-mercaptopropanesulphonate immobilization via Au-S bonding formation (denoted as Fe3O4@COF(TpBD)@Au-MPS nanocomposites), which were further utilized as adsorbents for magnetic solid-phase extraction (MSPE) of fluoroquinolones. Compared with Fe3O4@COF(TpBD), the composites exhibited higher affinity to fluoroquinolones. Under optimized conditions, the developed MSPE method coupled with HPLC–MS/MS showed good linearity (R2 ≥0.9989) and yielded low limits of detection (0.1–1.0 μg kg−1) for fluoroquinolones. Moreover, the proposed method was successfully applied to extract fluoroquinolones from spiked meats (pork, chicken and bovine). The satisfactory recoveries were in the range of 82–110.2% with the relative standard deviations (RSDs) lower than 7.7%. These results indicated that the Fe3O4@COF(TpBD)@Au-MPS is a promising magnetic adsorbent for trace fluoroquinolones determination in meat samples. This work not only provided a facile strategy for COF functionalization, but also developed an efficient method for detecting fluoroquinolones in foodstuffs.

In situ formation of thymol-based hydrophobic deep eutectic solvents: Application to antibiotics analysis in surface water based on liquid-liquid microextraction followed by liquid chromatography.

Abstract: A simple and ecofriendly sample preparation method was developed for quantifying fluoroquinolone (FQ) antibiotics in surface water. Seventeen combinations of monoterpenes (menthol, thymol, and camphor), fatty acids (heptanoic, octanoic, nonanoic, and decanoic acids), and a benzoate ester (salol) were utilized for the in situ formation of hydrophobic deep eutectic solvents (hDESs) for liquid-liquid microextraction (LLME). The hDES comprising thymol and heptanoic acid (HA) exhibited the highest extraction efficiency for ofloxacin, norfloxacin, ciprofloxacin, and enrofloxacin. Optimization via the one-variable-at-a-time strategy revealed that a 2:1 ratio of thymol to HA yielded the highest efficiency for antibiotic extraction at pH 4-7. Further, response surface methodology-based optimization suggested that the optimal extraction conditions involved the use of appropriate amounts of thymol and HA to generate 100 μL of hDES in 10 mL of aqueous sample with incubation at 52 °C for 5 min, followed by automated shaking for 1 min. The collected hDES phase was diluted and subjected to liquid chromatography-ultraviolet detection analysis. The established method based on in situ formation of hDES coupled with shaker-assisted LLME (in situ hDES-SA-LLME) was validated. The method was specific and showed good linearity in the 15-3000 ng mL-1 concentration range (r2 ≥ 0.9997), with a limit of detection of 3.0 ng mL-1, limit of quantification of 9.0 ng mL-1, accuracy of 84.1-113.65%, and intra-day and inter-day precision of ≤7.78% RSD and ≤7.91% RSD, respectively. The method was successfully applied to three different types of real surface water samples. Without toxic volatile organic solvents, the developed method allows for safe and rapid, yet reliable, analysis of FQ antibiotics.

Deep eutectic solvents in separations: Methods of preparation, polarity, and applications in extractions and capillary electrochromatography.

Abstract: Deep eutectic solvents (DESs) have emerged as alternatives to conventional organic solvents and ionic liquids (ILs). Their tunable and designer physio-chemical properties, low cost, and ease of preparation make them attractive solvent systems for use in extractions and additives to chromatographic separations. However, due to the diverse range of hydrogen bond acceptors and donors that comprise DESs, choosing the appropriate solvent for separations can be challenging. This review discusses all methods of DES preparation and details their advantages and disadvantages. Since polarity is an important aspect in their use in separations, the classification of DESs based on the betaine dye and nile red scales as well as Kamlet-Taft parameters is also discussed. Finally, a summary of applications of DESs in various extraction processes (phenolics, fuels, metals, proteins, carbohydrates), solid-phase extraction, solid-phase microextraction, as well as capillary electrochromatography is provided.

Fabrication of iron oxide@MOF-808 as a sorbent for magnetic solid phase extraction of benzoylurea insecticides in tea beverages and juice samples.

Abstract: A novel magnetic metal organic framework composite (Fe3O4@MOF-808) was synthesized by a facile solvothermal method and applied as an adsorbent for the magnetic solid phase extraction (MSPE) of benzoylurea insecticides (BUs) from tea beverages and juice samples. The prepared materials were characterized using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), vibrating sample magnetometry measurements and N2 adsorption-desorption experiments. The adsorption (adsorbent amount, extraction time and pH) and elution (elution solvent, elution volume and time) parameters were investigated in detail. Under the optimized experimental conditions, Fe3O4@MOF-808 exhibited simpler and better reusability than commercial C18, with an equivalent adsorption effect. Notably, π-π interactions, hydrophobic interactions and hydrogen bonding interactions contributed to the good adsorption of BUs by Fe3O4@MOF-808. Finally, a simple and sensitive method was established using Fe3O4@MOF-808-based MSPE coupled with high-performance liquid chromatography (HPLC). It provided low limits of detection (0.04–0.15 ng/mL), wide linear ranges (0.15–50 ng/mL) and satisfactory recoveries (84.6–98.3%). The proposed method was successfully applied for the fast and sensitive determination of BUs in tea beverages and juice samples.

Combination of dispersive solid phase extraction with solidification organic drop-dispersive liquid-liquid microextraction based on deep eutectic solvent for extraction of organophosphorous pesticides from edible oil samples.

Abstract: A dispersive solid phase extraction method was combined with deep eutectic solvent–based solidification of floating organic drop–dispersive liquid–liquid microextraction and used for the extraction/preconcentration of some organophosphorus pesticides residues from edible oil samples. The extracted analytes were quantified with gas chromatography–nitrogen phosphorous detector. In this procedure, the sample lipids are saponified with a sodium hydroxide solution and then the analytes are adsorbed onto a primary secondary amine sorbent. After that the analytes are desorbed with acetone as an elution/dispersive solvent and mixed with choline chloride: 3,3–dimethyl butyric acid deep eutectic solvent and the mixture is rapidly dispersed into deionized water. Then, the obtained cloudy solution is centrifuged and placed into an ice bath. The extraction solvent is solidified on the top of the solution. Finally, it is removed and dissolved in acetonitrile, and 1 µL of the solution is injected into the separation system. Validation of the method showed that limits of detection and quantification were in the ranges of 0.06–0.24 and 0.20–0.56 ng mL–1, respectively. Enrichment factors and extraction recoveries of the analytes ranged from 170–192 and 68–77%, respectively. The method had an acceptable precision with relative standard deviations less than ≤9.2% for intra– (n=6) and inter–day (n=6) precisions at four concentrations (3, 10, 50, and 250 ng mL–1, each analyte). Finally the method was used for determination of the analytes in five edible oil samples.

Electrospinning fabrication of covalent organic framework composite nanofibers for pipette tip solid phase extraction of tetracycline antibiotics in grass carp and duck

Abstract: In the current study, a novel covalent organic frameworks COF-SCU1 incorporated electrospun nanofibers (PAN@COF-SCU1 nanofibers) was fabricated via a facile electrospinning method and utilized as adsorbent in pipette tip solid-phase extraction (PT-SPE) of tetracycline antibiotics (TCs) from foods. The prepared PAN@COF-SCU1 nanofibers possessed both of the unique characteristics of electrospun nanofibers and COFS-CU1, and thus improving the adsorption capacity of the electrospun nanofibers and preventing the problems of leakage and high pressure caused by directly using the nanosize COFs as adsorbent in PT-SPE. The experiments affected the adsorption and desorption efficiencies, such as the loading ratios of COFS-CU1 in nanofibers, the amount of nanofibers, the matrix pH and desorption solvent, were studied in detail. Eventually, a new pipette tip solid-phase extraction-high performance liquid chromatography (PT-SPE/HPLC) method was proposed for the analysis of three TCs from food. Satisfied linearity for TCs was obtained in the range of 4–70 ng mL−1. The limits of detection and quantification were ranged from 0.6 to 3 ng mL−1 and from 2 to 10 ng mL−1, respectively. The interday and intraday precisions (RSD) were all lower than 9%. The proposed PT-SPE/HPLC method was used to determine TCs residues in grass carp and duck samples for the first time. The results could not only explore the availability of PT-SPE in the extraction of TCs in food samples, but also broadened the potential applications of COFs in sample preparation.

Magnetic molecularly imprinted polymers prepared by reversible addition fragmentation chain transfer polymerization for dispersive solid phase extraction of polycyclic aromatic hydrocarbons in water.

Abstract: Magnetic molecularly imprinted polymers (MMIPs) combine nanotechnology and molecular imprinting technology to offer selective and tunable enrichment for water analysis. In this paper, a selective sorbent was prepared by surface polymerization onto magnetic Fe3O4@SiO2 nanoparticles through reversible addition fragmentation chain transfer (RAFT) polymerization. The MMIPs were used for dispersive solid phase extraction (DSPE) of 16 PAHs as priority pollutants in aqueous matrices. After preconcentration, the analysis was performed using gas chromatography with an atmospheric pressure chemical ionization-tandem mass spectrometry (APGC–MS/MS). The extraction method is based on the dispersion of MMIPs in an aqueous sample using an ultrasonic bath which provides rapid equilibrium of analytes between the sorbent and sample solution. The enriched analytes were retrieved by collecting MMIP particles and desorbed into an organic solvent before instrumental analysis. A design of experiment (DOE) approach was applied to optimize several extraction parameters including the mass of MMIPs, the sample volume, salt addition, collection time, desorption volume, and desorption time. A fractional factorial design (FFD) (26-2) was performed to assess the influence of the selected factors on the extracted amount of analytes. The most effective factors including the mass of MMIPs, the volume of sample solution, and salt content was further investigated using central composite design (CCD) and yielded quadratic models between dependent and independent variables. The optimum conditions of DSPE obtained by desirability function (DF) were employed for preconcentration of PAHs in water samples. The evaluation showed that the MMIPs provide higher extraction efficiency compared to nanoparticles such as Fe3O4, Fe3O4@SiO2 and non-imprinted polymer, demonstrating the creation of selective recognition binding sites at the surface of magnetic nanoparticles. The LODs and LOQs ranged from 1 to 100 pg mL−1 and 2 to 200 pg mL−1, respectively. Finally, the MMIP-DSPE method was successfully applied for preconcentration and trace quantification of PAHs in real samples such as produced water and river water samples.

Eco-friendly ultrasonic assisted liquid–liquid microextraction method based on hydrophobic deep eutectic solvent for the determination of sulfonamides in fruit juices

Abstract: A sensitive, fast, eco-friendly ultrasound assisted liquid–liquid microextraction (LLME) in combination with hydrophobic deep eutectic solvent (DES) method was developed to preconcentrate and extract sulfonamides in fruit juices, prior to high-performance liquid chromatographic (HPLC) analysis. The DES was synthesized with trioctylmethylammonium chloride (TAC) and 2-octanol at the molar ratio of 1:2. Some parameters which affected the extraction efficiency were investigated and optimized, including the volume of DES, extraction method, extraction time, pH. Under the optimum conditions, good linearity (r = 0.9999) in the range of 0.1–50 µg mL−1 was obtained. The limit of detection (LOD) was 0.02–0.05 µg mL−1. And the accuracy of the developed method was confirmed by analysis of spike method, the recoveries were in the range of 88.09–97.84% at the spike levels of 2–20 µg mL−1 in fruit juices.

A functionalized magnetic covalent organic framework for sensitive determination of trace neonicotinoid residues in vegetable samples.

Abstract: A functionalized magnetic covalent organic framework containing the nitro groups (Fe3O4@COF-(NO2)2) with core-shell structure was synthesized for magnetic solid phase extraction (MSPE) of six neonicotinoid insecticides residue in vegetable samples. The structure of Fe3O4@COF-(NO2)2 was investigated by various characterization techniques. The Fe3O4@COF-(NO2)2 exhibits the excellent thermal and chemical stability, high surface area (254.72 m2 g−1), total pore volume (0.19 cm3 g−1), high magnetic responsivity (27.7 emu g−1), which can be used as an ideal adsorbent for rapid isolation and enrichment of target analytes. A sensitive method was developed by using Fe3O4@COF-(NO2)2-based MSPE coupled with HPLC with UV detection. It offered good linearity within the range of 0.1–30 ng mL−1, low limits of detection (S/N = 3) of 0.02–0.05 ng mL−1. Furthermore, high enrichment factors of 170–250 for six neonicotinoid insecticides were obtained. The applicability of Fe3O4@COF-(NO2)2 is demonstrated for measuring trace neonicotinoid residues in vegetable samples with satisfactory recoveries, which ranged from 77.5 to 110.2%. The results indicated that the Fe3O4@COF-(NO2)2 microspheres offer great potential for efficient extraction of neonicotinoid insecticides from complex samples.

Magnetic solid-phase extraction of sulfonamide antibiotics in water and animal-derived food samples using core-shell magnetite and molybdenum disulfide nanocomposite adsorbent

Abstract: A molybdenum disulfide(MoS2)-based core-shell magnetic nanocomposite (Fe3O4@MoS2) was synthesized by the stepwise hydrothermal method. Two-dimension ultrathin MoS2 sheets with a thickness of approximately 20 nm were grown in situ on the surface of Fe3O4 (∼200 nm). They were employed as an adsorbent for the magnetic solid-phase extraction (MSPE) of sulfonamide antibiotics (SAs) from water samples. High-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) was used for SA quantitation. Extraction parameters, including the pH effect, amount of Fe3O4@MoS2, extraction time, temperature, and desorption conditions, were systematically investigated. The electrostatic interaction between the positively charged SAs and negatively charged MoS2 nanoparticles in the optimal extraction conditions enhanced the adsorption of SAs on the sorbent surface. Under chosen conditions, the proposed strategy achieved wide linear range of 1.0–1000 ng·L−1 SAs, low limits of detection (LOD, 0.20–1.15 ng·L−1, S/N = 3:1), good trueness (recoveries between 85.50–111.5%), satisfactory repeatability and reproducibility (relative standard deviation,

Microextraction approaches for bioanalytical applications: An overview.

Abstract: Biological samples are usually complex matrices due to the presence of proteins, salts and a variety of organic compounds with chemical properties similar to those of the target analytes. Therefore, sample preparation is often mandatory in order to isolate the analytes from troublesome matrices before instrumental analysis. Because the number of samples in drug development, doping analysis, forensic science, toxicological analysis, and preclinical and clinical assays is steadily increasing, novel high throughput sample preparation approaches are calling for. The key factors in this development are the miniaturization and the automation of the sample preparation approaches so as to cope with most of the twelve principles of green chemistry. In this review, recent trends in sample preparation and novel strategies will be discussed in detail with particular focus on sorptive and liquid-phase microextraction in bioanalysis. The actual applicability of selective sorbents is also considered. Additionally, the role of 3D printing in microextraction for bioanalytical methods will be pinpointed.

Optimization and validation of a head space solid-phase microextraction-arrow gas chromatography-mass spectrometry method using central composite design for determination of aroma compounds in Chinese liquor (Baijiu).

Abstract: A headspace solid-phase microextraction Arrow (HS-SPME Arrow) method coupled with gas chromatography-mass spectrometry (GC–MS) was developed for the quantitation of a large number of aroma compounds in Chinese liquor (Baijiu). Optimization of extraction conditions by a central composite experimental design revealed that the dilution of the alcohol content of 5 mL of Baijiu to 10%, followed by the addition of 1.5 g of NaCl and subsequent SPME Arrow extraction with DVB/CAR/PDMS fiber coating over 45 min at 45 °C was the most suitable. The quantitative method allowed the extraction and identification of 82 aroma compounds (esters, alcohols, fatty acids, aldehydes & ketones, furans, pyrazines, sulfur compounds, phenols, terpenes, and lactones) in the Baijiu sample. The method was validated with good repeatability, inter and intra-day precision (almost below 15%), and accuracy (almost in the range of 81.5–119.96%). Furthermore, the method was validated successfully for the most significant compounds and was applied to study the composition of volatile compounds in different types of Baijiu. This research proved that SPME Arrow is an effective method for the extraction of aroma compounds in Baijiu and other distilled spirits. This developed method will allow improved analysis of other distilled spirits.

Noncovalent interactions in high-performance liquid chromatography enantioseparations on polysaccharide-based chiral selectors.

Abstract: Designed more than thirty years ago in order to improve and maximize the discrimination capability of native polysaccharides, cellulose- and amylose-based selectors have shown excellent and unequalled performances for the enantioseparation of chiral compounds. The successful story of these chiral selectors relies on a multi-site high-ordered chiral platform which is held up by intramolecular hydrogen bonds (HBs), and makes the polymer able to host and discriminate enantiomers. In this environment, both achiral and stereoselective intermolecular noncovalent interactions play a pivotal role, and HBs, halogen bonds (XBs), dipole-dipole, π-π stacking, steric repulsive, and van der Waals interactions underlie adsorption process and formation of transient diastereomeric assemblies between the polymer and the enantiomer pair. In the last decades, advances in computational chemistry and spectroscopic techniques have improved knowledge of noncovalent interactions, contributing to decode their functions in chemical systems. Significantly, over time the growing interplay between experimental and theoretical approaches has contributed to unravel intermolecular forces underlying selector-selectand association and to understand recognition patterns. On this basis, this review summarizes seminal and representative studies dealing with noncovalent interactions that function in HPLC enantioseparations promoted by cellulose benzoates and phenylcarbamates of amylose and cellulose. The importance of integrating theoretical and experimental approaches to profile mechanisms and interaction patterns is highlighted by discussing focused case studies. In particular, the advantageous utilization of electrostatic potential (V) analysis and molecular dynamics (MD) simulations in this field is evidenced. A systematic compilation of all published literature has not been attempted.

In-situ synthesis of fluorinated magnetic covalent organic frameworks for fluorinated magnetic solid-phase extraction of ultratrace perfluorinated compounds from milk.

Abstract: Perfluorinated compounds (PFCs) are new types of persistent organic pollutants known to bioaccumulate in organism, which have come under increased scrutiny due to the close relation with various health problems. Sensitive detection of PFCs remains a significant challenge because of their ultratrace levels in complex samples. Herein, fluorinated magnetic covalent organic frameworks (Fe3O4@TpPa-F4) were first synthesized via a monomer-mediated in situ growth strategy and served as fluorinated magnetic adsorbent. Accordingly, a novel pretreatment method based on fluorinated magnetic solid-phase extraction (FM-SPE) combined with HPLC-MS/MS was developed to detect ultratrace PFCs from milk samples. The as-prepared Fe3O4@TpPa-F4 possessed regular porosity (0.81 nm) with large surface areas (188.04 m2/g), high fluorine content (4.85%), strong magnetic responsiveness (50 emu/g), and good chemical and thermal stability, which rendered it an ideal adsorbent material for highly efficient extraction of PFCs. Under the optimized parameters, the developed method displayed good linearity for six PFCs in the range of 0.1–250 ng/L with high correlation coefficients (r ≥ 0.9952), and the corresponding limits of detection (LODs) were 0.005–0.05 ng/L (S/N ≥ 3). Furthermore, high enrichment factors (EFs, 21.91–100.6 folds) and acceptable relative standard deviations (RSDs) of inter-day (0.5–11.8%) and batch-to-batch (2.3–11.7%) for the six PFCs were achieved. Moreover, this method was further employed to milk samples with different brands and packages, in which ultratrace PFCs were found with diverse concentrations from 10.36 to 729.34 ng/L, confirming the promising applicability of the Fe3O4@TpPa-F4 as an alternative adsorbent for sample pretreatment.

Evaluation of sulfonic acid functionalized covalent triazine framework as a hydrophilic-lipophilic balance/cation-exchange mixed-mode sorbent for extraction of benzimidazole fungicides in vegetables, fruits and juices

Abstract: The functionalization of covalent organic frameworks (COFs) enhances chemical properties and expands future applications. Herein, a facile strategy for sulfoacid-functionalized COF is presented through post-modification of covalent triazine frameworks (CTFs) platform. The magnetic solid phase extraction (MSPE) material is obtained by anchoring in situ Ni particles on CTF support (Ni/CTF-SO3H) possessing a dual retention mechanism combining hydrophilic-lipophilic-balance (HLB) and cation-exchange interaction. We established the (Ni/CTF-SO3H)-MSPE method for selectively enriching carbendazim (CBZ) and thiabendazole (TBZ) from food samples and reducing matrix effect simultaneously. The method detection limit is 1.23–7.05 µg kg−1 for CBZ and TBZ in vegetable, fruit and juice samples, determined by high-performance liquid chromatography-ultraviolet detector. The recoveries of spiked CBZ and TBZ in the samples are 80.2–115.1% and RSDs 6.0–11.4%, depending on both analytes and samples. Our work provides a unique perspective in the development of functionalized COFs as a versatile HLB/cation-exchange mixed-mode SPE sorbent for extraction of basic analytes in complex matrix.

Effective extraction of organophosphorus pesticides using sol-gel based coated stainless steel mesh as novel solid-phase extraction sorbent.

Abstract: In this study, for the first time, stainless steel meshes coated with poly(ethylene glycol) and carbon nanotubes (PEG-CNT) by sol–gel technique were used as the adsorbent for solid-phase extraction. The coated stainless steel is loaded onto a cartridge and used to isolate and extract organophosphorus pesticides (OPPs) from water and fruit juice samples. Effective extraction parameters such as sample volume, desorption solvent, and desorption solvent volume were studied and investigated. Under optimal conditions, the linearity of the method was obtained in the range of 0.03 to 80 ng mL−1 and also the limits of detection (LODs) of the method were ranged from 0.01 to 0.03 ng mL−1. The repeatability of the method was evaluated at three concentration levels (0.1, 1, and 50 ng mL−1), and the relative standard deviation (RSD%) of the method was obtained in the range of 3.8 to 4.8%. Finally, the proposed method was used to analysis of OPPs in real water and fruit juice samples, with relative recovery in the range of 94.3 to 99.8%.

The applicability of high-speed counter current chromatography to the separation of natural antioxidants

Abstract: Antioxidants play an essential role in human health, as they have been found to be capable of lowering the incidence of many diseases, such as cancer and angiocardiopathy. Currently, more attention is paid to natural antioxidants because of the possible insecurity of synthetic antioxidants. Thus, the development of efficient techniques or methods to separate antioxidants from natural sources is requested urgently. High-speed counter current chromatography (HSCCC) is a unique support-free liquid-liquid chromatographic technique and has been widely applied in the field of separation of natural products. In this review, we summarize and analyze the related researches on the application of HSCCC in the separation of various natural antioxidants so far. The purpose of the article is to provide a certain theoretical support for the separation of natural antioxidants by HSCCC, and to make full use of advantages of HSCCC in the separation of bioactive components. In particular, some key problems associated with the separation strategies, the structural categories of natural antioxidants, solvent system choices, and the application of different elution modes in HSCCC separation, are summarized and commented. We expect that the content reviewed can offer more evidence for the development of the field of natural antioxidants separation, so as to achieve large-scale preparation of natural antioxidants.

Microcrystalline cellulose/metal−organic framework hybrid as a sorbent for dispersive micro-solid phase extraction of chlorophenols in water samples

Abstract: In this study, the microcrystalline cellulose/metal-organic framework 199 hybrid (MCC/MOF-199) was applied as sorbent for the dispersive micro-solid phase-extraction (D-μSPE) of chlorophenols. The D-μSPE method combined with high-performance liquid chromatography- ultraviolet detection (HPLC-UV) was employed to determine of four chlorophenols including 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), 2,3-dichlorophenol (2,3-DCP), and 2,5-dichlorophenol (2,5-DCP) in aqueous. The main parameters of the D-μSPE process that influence the extraction (i.e. the amount of sorbent, elution condition, extraction time, and pH) were investigated and optimized. Based on the outputs, the presence of MCC on the surface of MOF-199 leads to improve the properties of MOF-199 and the MCC/MOF-199 has the highest sorption capacity, durability, and porosity in comparison with MCC and MOF-199. According to the validation study at the optimized conditions, the linearity for the analytes was achieved in the range from 0.1 to 200 ng mL-1 for 2-CP and 4-CP and 0.15 to 200 ng mL-1 for 2,3-DCP and 2,5-DCP with correlation coefficients between 0.9928 and 0.9965. The limits of detection calculated at S/N=3 were in the range of 0.03-0.05 ng mL-1. Besides, the relative standard deviations (RSDs) for three spiking levels (0.2, 10,100 ng mL-1) do not exceed 6.8% and extraction recoveries are between 81.0% and 88.3%. Finally, the D-μSPE-HPLC-UV method was successfully applied to the analysis of CPs in real water samples (mineral, river and wastewater samples) with good recoveries (95.8 to 99.5%) and satisfactory precisions (RSD < 6.8%).

Oil extraction from tiger nut (Cyperus esculentus L.) using the combination of microwave-ultrasonic assisted aqueous enzymatic method - design, optimization and quality evaluation.

Abstract: Microwave-ultrasonic assisted aqueous enzymatic extraction (MUAAEE) was applied to extract tiger nut oil (TNO) The conditions of MUAAEE were optimized by Plackett-Burman design followed Box-Behnken design An oil recovery of 8523% was achieved under optimum conditions of a 2% concentration of mixed enzyme including cellulase, pectinase and hemicellulase (1/1/1, w/w/w), particle size

Spherical mesoporous covalent organic framework as a solid-phase extraction adsorbent for the ultrasensitive determination of sulfonamides in food and water samples by liquid chromatography-tandem mass spectrometry.

Abstract: Efficient extraction of polar sulfonamides antibiotics from aqueous samples and food is very challenging, because they are hydrophilic, their concentration is very low, and the matrix is complex. Covalent organic frameworks (COFs), a novel porous organic material, have attracted great attention. In this work, the spherical triphenylbenzene-dimethoxyterephthaldehyde-COFs (TPB-DMTP-COFs) were synthesized by a simple room temperature method, and due to their attractive properties, such as high outstanding acid-base stability, large specific surface area, low skeletal density, inherent porosity and high crystallinity, so TPB-DMTP-COFs as ideal solid phase extraction adsorbents showed excellent adsorption performance for trace polar sulfonamides in food and water. TPB-DMTP-COFs were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, powder X-ray diffraction, and so on. The important parameters were optimized to improve the extraction efficiency of TPB-DMTP-COFs toward sulfonamides. Analysis of sulfonamides was performed by liquid chromatography-tandem mass spectrometry. The developed method based on TPB-DMTP-COFs material achieved low limits of detection (0.5-1.0 ng L-1), wide linearity (5-1000 ng L-1), and good repeatability (2.5%-8.7%). The possible extraction mechanism was also discussed. Finally, the method was successfully applied to the enrichment and detection of sulfonamides in environmental water samples and food samples. The present study indicated that TPB-DMTP-COFs had splendid prospects in highly sensitive analysis of other pollutants in complex matrix.

Dispersive solid phase extraction combined with solidification of floating organic drop-liquid-liquid microextraction using in situ formation of deep eutectic solvent for extraction of phytosterols from edible oil samples.

Abstract: In this study, a dispersive solid phase extraction method was combined with solidification of floating organic drop–liquid–liquid microextraction based on in situ synthesis of deep eutectic solvent. It was used for the extraction of some phytosterols from edible oil samples. The extracted analytes were quantified by gas chromatography–mass spectrometry. In this procedure, the sample lipids are saponified with sodium hydroxide and then the analytes are adsorbed onto an octadecylsilane sorbent. After that the analytes are desorbed from the sorbent with ethanol as an elution solvent and the eluant is diluted with deionized water to obtain a homogenous solution. Then, a few amounts of choline chloride and n-butyric acid are dissolved in the solution and transferred into a water batch adjusted at 75 ⁰C for 5 min. During this period Choline chloride and n-butyric acid form a deep eutectic solvent (extraction solvent) dispersed in whole parts of the solution. The obtained cloudy solution is placed into an ice bath. The extraction solvent is collected and solidified on the top of the solution. Finally, it is removed and allows melted at room temperature and an aliquat of the solution is injected into the separation system. Validation of the method showed that limits of detection and quantification were in the ranges of 0.52–1.6 and 1.7–5.6 ng mL–1, respectively. Enrichment factors and extraction recoveries of the analytes ranged from 312 to 375 and 75–90%, respectively. The method had a proper percision with relative standard deviations less than ≤8.2% for intra– (n = 6) and inter–day (n = 6) precisions at a concentration of 15 ng mL–1 of each analyte. Finally the method was successfully used for determination of the analytes in some edible oil samples.

Combination of gel-electromembrane extraction with switchable hydrophilicity solvent-based homogeneous liquid-liquid microextraction followed by gas chromatography for the extraction and determination of antidepressants in human serum, breast milk and wastewater

Abstract: The current study presents for the first time a combination of the gel electromembrane extraction (GEL-EME) and switchable hydrophilicity solvent-based homogeneous liquid-liquid microextraction (SHS-HLLME) methods which can be used as an efficient hyphenated extraction procedure. This coupled method, which was followed by GC-FID, was applied for quantification of antidepressants (desipramine, clozapine, and citalopram) in biological and wastewater samples. The effective parameters of both GEL-EME and SHS-HLLME procedures were optimized. Using an agarose gel membrane, analytes were extracted from 7.0 mL of the sample solution to 500 µL of the aqueous acceptor solution. The maximum extraction of analytes of interest was obtained under the optimized conditions (pH of acceptor solution, 5.0; pH of gel membrane, 5.0; pH of sample solution, 7.0, voltage value, 30 V; and extraction time, 30 min). Then, the acceptor solution was transferred to the extraction cell and the SHS-HLLME procedure was conducted again under the optimized conditions. Dipropylamine (50 µL) was selected as an extraction solvent. The introduced technique exhibited good linearities with coefficients of determinatin (R2) higher than 0.983 and an acceptable linear range of 5.0–1000 ng/mL. Accordingly, the limit of detection was ≤ 1.0 ng/mL (S/N = 3) for all analytes, and the high enrichment factors were obtained in the range of 178.7–194.8. Moreover, the corresponding repeatability was from 4.0 to 8.7% (n = 3). The proposed method was successfully utilized to determine trace levels of the drugs in human serum, wastewater, and breast milk samples.

Magnetic covalent organic framework as a solid-phase extraction absorbent for sensitive determination of trace organophosphorus pesticides in fatty milk.

Abstract: A simple and efficient magnetic solid-phase extraction (MSPE) method was established with magnetic covalent organic framework (COF) as adsorbent to enrich organophosphorus pesticides from fatty milk samples, followed by the sensitive determination via LC-MS/MS The key parameters influencing the MSPE efficiency were comprehensively investigated to afford an optimized procedure All the target analytes could be captured directly by magnetic COF from milk without protein precipitation, making the pretreatment rapid and convenient Systematic method validation demonstrated its satisfactory linearity, recoveries (800-105 %), and precision (RSDs <123 %) The method limits of quantification were 02-05 μg L-1 A comparison experiment to the reported solid-phase extraction fully verified the present MSPE more rapid, accurate, and environment-friendly Furthermore, FT-IR and XPS analysis were performed to reveal the adsorption mechanisms of magnetic COF to organophosphorus pesticides, which could offer guidance on the rational design of COF adsorbent for various target analytes

Preparation of a stilbene diamido-bridged bis(β-cyclodextrin)-bonded chiral stationary phase for enantioseparations of drugs and pesticides by high performance liquid chromatography.

Abstract: A stilbene diamido-bridged bis(β-cyclodextrin) was synthesized via the reaction between 4,4′-stilbene dicarboxylic acid and 6-deoxy-6-amino-β-cyclodextrin. Then it was bonded onto the surface of an ordered mesoporous SBA-15 to obtain a novel bridged bis(β-cyclodextrin)-bonded chiral stationary phase (SBCDP). The structures of the bridged bis(β-cyclodextrin) and SBCDP were characterized by the mass spectrometry, nuclear magnetic resonance, infrared spectroscopy, elemental analysis and thermogravimetric analysis. The chromatographic performance of SBCDP was systematically evaluated by separating 23 racemic drugs and pesticides, including trimeprazine, praziquantel, flavanones, β-blockers and triazole pesticides in the reversed-phase chromatography or the polar organic mode. The chromatographic conditions that affect the enantioselectivity or diasterioselectivity of SBCDP were investigated in detail, including the mobile phase composition, pH value and column temperature. As a result, all tested analytes were resolved on SBCDP with high resolutions (1.51∼5.15) within about 25 min, and the enantioseparation resolutions of flavanone and imazalil were up to 5.15 and 4.38, respectively. Compared with the native β-cyclodextrin stationary phase (CDCSP), the SBCDP had a better chromatographic performance in enantioselectivity and diasterioselectivity. For example, enantiomers of trimeprazine, praziquantel, flavanone and imazalil those could not be separated by CDCSP, were separated by SBCDP with high resolutions. Unlike the small cavity (0.65 nm) of native CD, the bridging linker of the bridged bis(β-CD) supplied a well-organized “pseudo-cavity”, and combined two native CDs as an organic whole, which could synergistically encapsulate and complex some bulky analytes, making the chiral discrimination of SBCDP more precise. Moreover, we also found that SBCDP possessed high enantioselectivity and diastereoselectivity over a wide range of temperature (30∼60 °C), which made the fast analysis possible. As a new chiral separation material, SBCDP may have wider applications in analysis of chiral compounds.

The evolution of two-dimensional gel electrophoresis - from proteomics to emerging alternative applications.

Abstract: Two-dimensional gel electrophoresis (2-DE) is a technique that has been widely applied in a variety of proteomics studies. It is capable of resolving complex protein mixtures into individual protein spots based on their isoelectric point and molecular weight, enabling large-scale analysis of protein expression patterns for deciphering their changes in different biological conditions. 2-DE is a powerful tool that empowers researchers to perform differential qualitative and quantitative proteome analysis and is particularly advantageous for characterizing protein isoforms and post-translationally modified proteins. Despite its popularity as the workhorse for proteomics in the past few decades, it has been gradually displaced by the more sophisticated and high-performance mass spectrometry-based methods. However, there are several variations of the 2-DE technique that have emerged as promising approaches that shine new light on specific niches that 2-DE could still contribute. In this review, we first provide an overview of the applications of 2-DE, its merits and pitfalls in the current proteomic research arena, followed by a discussion on several alternative approaches for potential future applications.

Single isomer cyclodextrins as chiral selectors in capillary electrophoresis.

Abstract: Since decades, cyclodextrins are one of the most powerful selectors in chiral capillary electrophoresis for the enantioseparation of diverse organic compounds. This review concerns papers published over the last decade (from 2009 until nowadays), dealing with the capillary electrophoretic application of single isomer cyclodextrin derivatives in chiral separations. Following a brief overview of their synthetic approaches, the inventory of the neutral, negatively and positively charged (including both permanently ionic and pH-tunable ionizable substituents) and zwitterionic CD derivatives is presented, with insights to underlying structural aspects by NMR spectroscopy and molecular modeling. CE represents an ideal tool to study the weak, non-covalent supramolecular interactions. The published methods are reviewed in the light of enantioselectivity, enantiomer migration order and the fine-tuning of enantiodiscrimination by the substitution pattern of the single entity selector molecules, which is hardly possible for their randomly substituted counterparts. All the reviewed publications herein support that cyclodextrin-based chiral capillary electrophoresis seems to remain a popular choice in pharmaceutical and biomedical analysis.

Cyclodextrin-based sorbents for solid phase extraction

Abstract: Cyclodestrins (CDs) are cyclic oligosaccharides well-known for their ability to form host-guest inclusion complexes with properly sized compounds. They have been used for decades as chiral selectors as well as drug delivery systems within the frameworks of separation science and pharmaceutical science. More recently, their use has been extended to the field of extractive science under the stimulus of additional advantageous characteristics, such as low-price, negligible environmental impact, non-toxicity, as arising from the fact that natural CDs are starch degradation products. To abate their solubility in water and generate novel sorbents for solid phase extraction, the following approaches have been employed: (i) immobilization onto inert materials (silica, attapulgite, etc.); (ii) immobilization onto nanomaterials (magnetic nanoparticles, titanium oxide, carbon nanotubes, graphene oxide, etc.); (iii) polymerisation with specific cross-linkers to form the so-called CD-based nanosponges. Particularly promising are these last ones for their selectivity, mesoporous structure, insolubility in aqueous media and good dispersibility. This review offers a concise overview on the state of art and future prospects of CDs in this important sector of the analytical chemistry, offering a critical perspective of the most significant applications.