Click preparation of triazole-bridged teicoplanin-bound chiral stationary phases for efficient separating amino acid enantiomers.

Enantioseparation of amino acids is considered as a challenging task due to the extreme structural similarity of their enantiomers. Herein, teicoplanin was modified with different chemical equivalents of azide groups and attached to silica particles by employing Click Chemistry for resolution of chiral amino acids for the first time. Interestingly, teicoplanin modified with 5-fold the chemical equivalent of azide groups (TK-2 CSP) exhibited superior amino acid separation ability compared to two other columns: one modified with only 1-fold the chemical equivalent of azide groups (TK-1 CSP), and the other modified with excess azide groups (TK-3 CSP). Additionally, the TK-2 CSP exhibited superior enantioselectivity when separating amino acids containing hydrophobic alkyl side chains in comparison to other teicoplanin-based CSPs. The TK-2 CSP column allows the baseline separation of 7 native amino acids. Molecular docking demonstrates that effective enantioseparation arises from distinct patterns of interaction between the host and guest molecules. Moreover, (p-methyl) phenylcarbaminoylated-teicoplanin CSP (TK-4, TK-5 CSP) were prepared by post-modification from TK-1 CSP and TK-2 CSP to isolate Fmoc-modified amino acids. This work explores the impact of various modification methods on the enantioseparation effects of host molecules and paves the way for expanding the potential applications of teicoplanin and macrocyclic glycopeptide molecules.

Cellulose-Based Hectocycle Nanopolymers: Synthesis, Molecular Docking and Adsorption of Difenoconazole from Aqueous Medium.

The goal of this work was to develop polymer-based heterocycle for water purification from toxic pesticides such as difenoconazole. The polymer chosen for this purpose was cellulose nanocrystalline (CNC); two cellulose based heterocycles were prepared by crosslinking with 2,6-pyridine dicarbonyl dichloride (Cell-X), and derivatizing with 2-furan carbonyl chloride (Cell-D). The synthesized cellulose-based heterocycles were characterized by SEM, proton NMR, TGA and FT-IR spectroscopy. To optimize adsorption conditions, the effect of various variable such as time, adsorbent dose, pH, temperature, and difenoconazole initial concentration were evaluated. Results showed that, the maximum difenoconazole removal percentage was about 94.7%, and 96.6% for Cell-X and Cell-D, respectively. Kinetic and thermodynamic studies on the adsorption process showed that the adsorption of difenoconazole by the two polymers is a pseudo-second order and follows the Langmuir isotherm model. The obtained values of ∆G ° and ∆H suggest that the adsorption process is spontaneous at room temperature. The results showed that Cell-X could be a promising adsorbent on a commercial scale for difenoconazole. The several adsorption sites present in Cell-X in addition to the semi crown ether structure explains the high efficiency it has for difenoconazole, and could be used for other toxic pesticides. Monte Carlo (MC) and Molecular Dynamic (MD) simulation were performed on a model of Cell-X and difenoconazole, and the results showed strong interaction.

Enantioseparation and determination of triazole fungicides in fruit juice by aqueous biphasic system coupled with HPLC-MS/MS.

The aqueous biphasic system based on choline ionic liquids and ethylene/propylene oxide copolymer coupled with high-performance liquid chromatography-tandem mass spectrometry was developed for the simultaneous determination of the enantiomers of two fungicides: myclobutanil and tebuconazole. The influence of mass fractions of ionic liquids and the copolymer on the extraction efficiency of the target fungicides was investigated. The analytes are mainly concentrated in the bottom, copolymer-rich phase. The extraction efficiencies of the selected fungicides were significantly affected by the concentrations of the copolymer, and their extraction efficiencies decreased with the higher mass fractions of the copolymer, while the mass fraction of ionic liquids had little effect on their extraction behavior. Excellent extraction efficiency was achieved using the aqueous biphasic system based on choline L-lysinate and the copolymer. At three spiked concentrations of 0.01, 0.05, and 0.1 mg/kg, the average recoveries of the selected fungicides ranged from 80 to 89%, with the relative standard deviations in the range of 2.1-5.3%. Limits of quantitation for the enantiomers of tebuconazole and myclobutanil were 0.5 and 5.0 µg/kg, respectively. The developed system could be successfully applied to the analysis of triazole fungicides residue in real samples.

Analytical research on the separation and residue of chiral pesticide triadimenol in fruit and vegetable puree.

In this paper, a method for the separation of triadimenol stereoisomers using ultra-performance convergence chromatography and an analytical method for the determination of triadimenol stereoisomer residues in pumpkin puree, apple puree, and tomato puree as a supplement for infants are established. Test samples were extracted with acetonitrile and successively purified with graphitized carbon black and Florisil column. Afterward, Acquity Trefoil AMY1 column was adopted for chiral separation of chromatographic column, and gradient elute was carried out with supercritical carbon dioxide-methanol as the mobile phase and with external standard method for quantitation. Results showed that the linearly dependent coefficient of the four kinds of triadimenol stereoisomers within 1.0 and 50 mg/L was greater than 0.9997, and the limit of quantitation of the four kinds of triadimenol stereoisomers was 0.05 mg/kg. Recovery experiment was carried out within 0.05 and 1.0 mg/kg scope, the recoveries were 81.0-107％, and the relative standard deviation was 2.3-7.6%. This method implemented the separation of triadimenol stereoisomers and its residue test in pumpkin puree, apple puree, and tomato puree as a supplement for infants, and it can provide reliable technical support for the analysis of pesticide residue and assessment of product quality.

Enantiomeric separation of prothioconazole and prothioconazole-desthio by Capillary Electrophoresis. Degradation studies in environmental samples.

In this work, two analytical methodologies by Capillary Electrophoresis were developed. The first one enabled the rapid and cost-effective enantioseparation of prothioconazole and was applied to the analysis of prothioconazole-based commercial agrochemical formulations. The second methodology enabled the simultaneous enantioseparation of prothioconazole and its metabolite prothioconazole-desthio and was applied to degradation studies of both compounds in soil and sand samples. The influence of several experimental variables was investigated to develop both methodologies. The separation of prothioconazole enantiomers was achieved in 4.5 min with a resolution of 2.8 employing a neutral cyclodextrin (heptakis(2,3,6-tri-O-methyl)-ß-cyclodextrin). Given the nature of prothioconazole-desthio, a neutral cyclodextrin cannot be used for its chiral separation. For this reason, the simultaneous enantioseparation of prothioconazole and prothioconazole-desthio was achieved in 5.5 min with resolution values of 1.9 and 8.2, respectively, using a negatively charged cyclodextrin (sulfated-γ-cyclodextrin). The analytical characteristics of the developed methodologies were evaluated and both methods showed good performance to be applied to the quantitation of the enantiomers of prothioconazole in commercial agrochemical formulations (LOD 0.7 mg L-1) and to carry out degradation studies for both compounds in environmental matrices (LODs lower than 0.9 and 1.3 mg L-1 for prothioconazole and prothioconazole-desthio enantiomers, respectively). The recovery values obtained were in the range between 94-104 % for the agrochemical formulations, between 96-99 % for the sand samples and between 97-100 % for the soil samples.

Chromatographic separation of the interconverting enantiomers of imidazo- and triazole-fused benzodiazepines.

The toolbox of medicinal chemists includes the 1,4-benzodiazepine scaffold as a "privileged scaffold" in drug discovery. Several biologically active small molecules containing a 1,4-benzodiazepine scaffold have been approved by the FDA for the treatment of various diseases, with most of them being used for their psychotropic effects. The therapeutic potential of 1,4-benzodiazepines has stimulated the interest of synthetic chemists in developing new synthetic strategies to a range of substituted analogues for biological evaluation. A structural variation of the classical benzodiazepine skeleton is observed e.g. in alprazolam, midazolam, and related benzodiazepines, which contain a 1,2,4-triazole or an imidazole ring fused to the benzodiazepine core. Irrespective of the presence of the fused heterocyclic ring, the seven-membered diazepine ring is far from planar, and its shape resembles a twist chair. Then, the unsymmetrical substitution pattern around the seven membered cycle renders these molecules chiral, as they lack any reflection-type symmetry element. However, chirality of this molecules is labile at room temperature, becausea simple ring flipping process converts one enantiomer into the other, and 1,4-benzodiazepines exist as a mixture of rapidly interconverting conformational enantiomers in solution at or near room temperature. Physical separation of the interconverting enantiomers of diazepam and of other related 1,4-benzodiazepin-2-ones can be accomplished by low temperature HPLC on chiral stationary phases (CSPs). If the HPLC column is cooled down to temperatures where the interconversion rate is sufficiently low, compared to the chromatographic separation rate, distinct separated peaks can be observed, provided the CSP is sufficiently enantioselctive. The apparent rate constants for the on-column enantiomerization and the corresponding free energy activation barriers were obtained by simulation of exchange-deformed HPLC profiles using a computer program based on the stochastic model. Here we report on the dynamic HPLC investigations carried out on a set of fused imidazo and triazolo-benzodiazepines (alprazolam, midazolam, triazolam and estazolam) The experimental dynamic chromatograms and the corresponding interconversion barriers reported in this paper show that the third fused heterocyclic ring increase the energy barrier by 2 kcal/mol.

Simultaneous determination, dissipation and decontamination of fungicides applied on cabbage using LC-MS/MS.

A method for simultaneous determination of carbendazim and tebuconazole residues in cabbage was developed and validated in LC-MS/MS. Samples were extracted and purified following the modified QuEChERS procedure, which enabled the elution of carbendazim and tebuconazole at 0.96 and 5.31 min, respectively. LOD and LOQ were 0.0005 and 0.0015 mg kg-1, respectively. Mean recovery was in the range of 78.94 to 104.89% for carbendazim and 76.07 to 98.62% for tebuconazole. The field samples recorded residues of 0.274 and 0.481 mg kg-1; and 0.194 and 0.392 mg kg-1 at single and double dose for carbendazim and tebuconazole, respectively. Half-life values were 2.17 and 2.99 for carbendazim and 2.74 and 2.81 for tebuconazole at single and double dose, respectively. Decontamination with saltwater wash followed by cooking and lemon water wash found superior in the removal of residues more than 90%.

Preparation of magnetic MOFs for use as a solid-phase extraction absorbent for rapid adsorption of triazole pesticide residues in fruits juices and vegetables.

Detection of low levels of triazole fungicides in agricultural product matrices is important. Although several detection methods have been developed, all have some drawbacks, such as being time-consuming, requiring complex sample pretreatment, and consuming large volumes of organic solvents. There is an urgent need for a simple and rapid detection method for triazole fungicides. In this study, the adsorbent composite material magnetic MOFs based on Fe3O4-MWCNT was synthesized by in-situ polymerization at room temperature, and was applied to extract triazole pesticides from fruits and vegetables. High-performance liquid chromatography-tandem mass spectrometry was used for quantification. Under optimized conditions, the constructed detection method showed a low detection (LOD) of 0.52-1.83 µg/L (S/N = 3) and wide linear range of 5.00-500.00 µg/L for triazole fungicides in the fruit and vegetable samples. The method recovery for spiked fungicides (10, 50, and 100 µg/L) in cabbage, spinach, orange juice, and apple juice ranged from 62.80% to 94.20%. The constructed detection method has a lower detection limit than previously reported methods and has a higher sensitivity for triazole pesticide residues in complex matrices.

Popping candy-assisted dispersive liquid-liquid microextraction for enantioselective determination of prothioconazole and its chiral metabolite in water, beer, Baijiu, and vinegar samples by HPLC.

To simultaneously determine the enantiomers of prothioconazole and its chiral metabolite prothioconazole-desthio in water, beer, Baijiu, and vinegar samples by HPLC, a simple, fast, environmentally-friendly popping candy-assisted dispersive liquid-liquid microextraction technique was developed. A green medium-chain fatty acid (decanoic acid) and popping candy could be used as the extractant and solid dispersant respectively to avoid the use of toxic organic solvents. Decanoic acid was collected after extraction by solidification at room temperature. The linear range of this technique was from 27.1 to 1000 µg L-1. The limits of detection and quantification were within the ranges of 8.1-11.2 µg L-1 and 27.1-37.3 µg L-1, respectively. The extraction recovery was 80.8% to 102.5% with the relative standard deviation ranged from 1.1 to 7.1%. This technique has been successfully applied to enantioselectively determine the residues of prothioconazole and prothioconazole-desthio in water, beer, Baijiu, and vinegar samples.

Magnetic metal-organic framework MIL-100 (Fe)/polyethyleneimine composite as an adsorbent for the magnetic solid-phase extraction of fungicides and their determination using HPLC-UV.

Fe3O4@MIL-100 (Fe)/PEI are used for the first time as an adsorbent material for the extraction of pesticide residues (epoxiconazole, flusilazole, tebuconazole, and triadimefon) from food matrices. The adsorbent proposed (Fe3O4@MIL-100(Fe)/PEI) was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), thermogravimetric (TG) analysis, and vibrating sample magnetometer (VSM) techniques to evaluate the properties of the sorbent. Then, the Fe3O4@MIL-100 (Fe)/PEI was employed for the quantification of the four triazole fungicides in fruits and vegetables (apple, orange, tomato, cabbage, and cucumber) using HPLC-UV for separation and detection. During the extraction process, the main parameters such as amount of adsorbent, extraction time, pH value, ionic strength, eluting solvent, and eluting volume were optimized. Under the optimum conditions, good linearity of this method was observed for all analytes, with correlation coefficients (R2) ≥ 0.9908. The limits of detection (LODs) ranged from 0.021-3.04 µg kg-1. The extraction recoveries of the four triazole fungicides varied from 73.9 to 109.4% with relative standard deviations (RSD) in the range 0.5 to 6.2%. Compared with other MOFs, the modification of Fe3O4@MIL-100 (Fe) with PEI shows high efficient adsorption due to the combined benefits of MIL-100 (Fe) and PEI. The material is easily synthesized, has good stability, and is of low cost.  Graphical abstract.

Hydroxyl-containing porous organic framework coated stir bar sorption extraction combined with high performance liquid chromatography-diode array detector for analysis of triazole fungicides in grape and cabbage samples.

In this work, a hydroxyl-containing porous organic framework (HC-POF) was prepared by a simple solvothermal reaction with 1,4-phthalaldehyde and phloroglucinol as monomers. Sol-gel method was used to coat HC-POF on the glass stir bar. The prepared HC-POF coated stir bar shows better extraction performance for six triazole fungicides (TFs) compared to commercial polydimethylsiloxane and ethylene glycol-silicone coated stir bars. Fourier transform infrared Spectrometry and X-ray photoelectron Spectrometry were used to explore interactions between HC-POF coating and TFs. It is assumed that the coating mainly adsorbs TFs through π-π interactions, hydrogen bonding and hydrophobic interactions. Based on this fact, a new method of HC-POF coated stir bar sorptive extraction combined with high performance liquid chromatography-diode array detector was developed for the determination of six TFs in grape and cabbage samples. A series of extraction and desorption conditions were carefully optimized, including salt concentration, sample solution pH, stirring rate and desorption solvent. Under the optimized experimental conditions, the proposed method displayed limits of detection in the range of 0.022 -0.071 µg L-1, which is the lowest among the reported SBSE methods for target TFs analysis. The linear range for six TFs was 0.1/0.2-500 µg L-1 and the recoveries for the spiked grape and cabbage were 81.0-109% and 80.7-111%, respectively.

Differential Impacts of Azole Antifungal Drugs on the Pharmacokinetic Profiles of Dasatinib in Rats by LC-MS-MS.

BACKGROUND: Dasatinib, as an oral multi-targeted inhibitor of BCR-ABL and SRC family kinases, has been widely used for the treatment of Philadelphia Chromosome Positive Leukemias in imatinib-acquired resistance and intolerance. The study aimed to develop and validate a simple and robust assay with a small volume of plasma based on liquid chromatography coupled with tandem mass spectrometry to determine the concentration of dasatinib and to investigate the impact of the cytochrome 3A4 inhibitors, including ketoconazole, voriconazole, itraconazole and posaconazole, on the pharmacokinetics of dasatinib in rats. METHODS: Thirty rats were divided randomly into five groups, control group (0.5% carboxymethylcellulose sodium), ketoconazole (30 mg/kg) group, voriconazole group (30 mg/kg), itraconazole group (30 mg/kg) and posaconazole group (30 mg/kg). After 150 µL blood samples were collected at 0, 0.5, 1, 2, 4, 6, 8, 10, 12, 24, and 48 h and precipitated with acetonitrile, the plasma concentration of dasatinib was determined through Fluoro- Phenyl column (150 mm×2.1 mm, 3 µm) in a positive ionization mode. RESULTS: The results suggested that ketoconazole, voriconazole, and posaconazole could increase the AUC0-t of dasatinib to varying degrees while significantly reducing its clearance. However, there was no significant impact on the pharmacokinetics of dasatinib, co-administered with itraconazole except for the CL and MRT0-t of dasatinib. Additionally, voriconazole could significantly increase Cmax of dasatinib by approximately 4.12 fold. CONCLUSION: These data indicated that ketoconazole, posaconazole and voriconazole should be cautiously co-administered with dasatinib or close therapeutic drug monitoring of dasatinib concentration, which might cause the drug-drug interaction.

Validation of a methodology by LC-MS/MS for the determination of triazine, triazole and organophosphate pesticide residues in biopurification systems.

Biopurification systems are useful in the management of pesticide residues and provide an option to dispose wastewaters of agricultural origin derived from pesticide application practices. The analysis of pesticide residues in the biopurification system biomixture is necessary to determine whether the removal of the target compounds occurs with reliable results. In this study, the pesticide extraction methodology was optimized and validated in a biomixture composed of coconut fiber, compost and soil, to determine a total of 43 molecules, distributed among triazines (10), triazoles (13) and organophosphates (20) using liquid chromatography coupled to a triple quadrupole mass spectrometer. For the validation, the parameters of linearity, matrix effect, limit of determination (LOD), specificity, selectivity, precision, trueness and robustness in the proposed biomixture were evaluated. The analyses of those parameters revealed satisfactory results of the method for most of the compounds, with the exception of diclorvos and ciromazine, for which the development of an alternative method is recommended. Once the extraction methodology was validated, the removal of eight molecules was assayed in a biopurification system used for the simultaneous treatment of a mixture of pesticide commercial formulations. Although most of the compounds were at least partially removed, none of them was eliminated at levels below the LOD. The removal pattern of ametryn, atrazine, chlorpyrifos, malathion and terbutryn was comparable to those obtained in other efficient biomixtures, and the highly recalcitrant triadimenol was eliminated; nonetheless, tebuconazole and diazinon were not significantly removed.

Effect of processing on the reduction of pesticide residues in a traditional Chinese medicine (TCM).

The behaviour of residues of tebuconazole, prochloraz, and abamectin in rehmannia during rehmannia decoction processing was systemically assessed. The pesticides were determined by ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) after each processing step including washing, steaming and drying, carbonising, and boiling. Results showed that the pesticide residues significantly decreased after the steps of washing, carbonising, and boiling. Washing reduced pesticide residues by 41.2%-60.0%; carbonising reduced pesticides by 27.1%-71.1% in both prepared rehmannia and unprepared rehmannia. After boiling, the concentrations of tebuconazole and prochloraz were 0.0002-0.0022 mg kg-1 in decoctions. Abamectin was not detected in rehmannia after carbonising, and it was not detected in decoctions either. The processing factors (PFs) were less than 1 during food processing, indicating that the full set of processing can reduce the residues of tebuconazole, prochloraz, and abamectin in rehmannia decoction.

Simultaneous Enantioselective Determination of Two New Isopropanol-Triazole Fungicides in Plant-Origin Foods Using Multiwalled Carbon Nanotubes in Reversed-Dispersive Solid-Phase Extraction and Ultrahigh-Performance Liquid Chromatography-Tandem Mass Spectrometry.

A simple and sensitive enantiomeric analytical method was established for the determination of two new isopropanol-triazole fungicides mefentrifluconazole and ipfentrifluconazole in plant-origin foods using ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The best enantioseparation of the four target stereoisomers was achieved on a Chiral MX(2)-RH column within 7 min by reversed-phase liquid chromatography, which is a significant improvement in the resolution of different chiral compounds under one set of conditions. A simple and effective pretreatment procedure was developed for the extraction and purification of the two target chiral fungicides using reversed-dispersive solid-phase extraction (r-DSPE) with multiwalled carbon nanotubes (MWCNTs). The influence of the type and amount of MWCNTs on the purification efficiencies and recoveries was evaluated. The mean recoveries for all four stereoisomers were in the range of 76.9-91.2%, with relative standard deviation (RSD) values below 7.2%. The limit of quantification (LOQ) of all stereoisomers of mefentrifluconazole and ipfentrifluconazole was 5 µg/kg for all tested matrixes. The results of the method validation and real samples analysis confirm that the established method is efficient and reliable for the enantiomeric determination of mefentrifluconazole and ipfentrifluconazole in plant-origin food samples.

Magnetic amino-functionalized hollow silica-titania microsphere as an efficient sorbent for extraction of pesticides in green and roasted coffee beans.

This study describes the synthesis and application of a magnetic amino-functionalized hollow silica-titania microsphere as a new sorbent for magnetic dispersive micro-solid phase extraction of selected pesticides in coffee bean samples. The sorbent was fully characterized by Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, transition electron microscopy, energy-dispersive X-ray spectroscopy, and vibrating sample magnetometry techniques. Significant extraction parameters affecting the proposed method, such as extraction time, sorbent amount, sample solution pH, salt amount, and desorption conditions (desorption solvent and time) were investigated and optimized. All the figures of merits were validated in coffee bean samples under the matrix-matched calibration method. Linear dynamic ranges were 5-250 µg/kg with the determination coefficients (R2 ) > 0.9980. The limits of detection for the pesticides of chlorpyrifos, malathion, hexaconazole, and atrazine were 1.42, 1.43, 1.35, and 1.33 µg/kg, respectively. Finally, the method was successfully applied for the determination of the pesticides in green and roasted coffee bean samples, and the obtained recoveries were in the range of 74-113% for spiked samples. The prepared sorbent could be used for the magnetic dispersive micro-solid phase extraction of pesticides in the plant-derived food matrix.

Sequential extraction and enrichment of pesticide residues in Longan fruit by ultrasonic-assisted aqueous two-phase extraction linked to vortex-assisted dispersive liquid-liquid microextraction prior to high performance liquid chromatography analysis.

A simple, green and efficient method for extraction, purification and enrichment of pesticide residues of triazoles and pyrethroids in Longan fruit was developed by ultrasonic-assisted aqueous two-phase extraction (UAATPE) coupled to vortex-assisted dispersive liquid-liquid microextraction (VADLLME). Using an aqueous two-phase system (ATPS) of ethanol/K2HPO4 as extraction solvent, the composition of the ATPS, extraction temperature and time were investigated, respectively. Then VADLLME process also was optimized by investigating type and volume of extracting and dispersive solvents, vortex-assisted time and salt addition. The optimum conditions were as follows: the ATPS composition of ethanol concentration 30.0% (w/w) and K2HPO4 concentration 25% (w/w), extraction temperature 70 °C and extraction time 15 min for UAATPE; 1-dodecanol 200 µL as extraction solvent, ethanol 1.25 mL as dispersive solvent, vortex-assisted time 1.5 min and addition of NaCl 4% (w/v) for VADLLME. Ethanol as extraction solvent and dispersive solvent could directly connect UAATPE with VADLLME without extra steps. By means of HPLC-DAD detection, nine pesticides had good linearity ranged from 0.0200 to 13.59 µg/mL (R2 ≥ 0.9957). LODs and LOQs were in the range of 0.005576-0.01740 µg/mL and 0.01859-0.05010 µg/mL, respectively. UAATPE-VADLLME coupled to HPLC was successfully applied to simultaneous determination of multiple pesticides in Longan fruit, and mean recoveries and RSDs were between 76.95% and 98.63%, 1.2% and 9.8%, respectively. Furthermore, myclobutanil, fenpropathrin and deltamethrin were detected in pericarp and pulp of Longan samples from different districts, respectively.

Separation of twelve posaconazole related stereoisomers by multiple heart-cutting chiral-chiral two-dimensional liquid chromatography.

Posaconazole represents a triazole antifungal agent which is used to treat various fungal infections. It contains four chiral centers leading to 16 stereoisomers. With the convergent synthesis route, only 11 related stereoisomeric impurities may potentially exist in the active pharmaceutical ingredient (API). It is a challenge to separate all the stereoisomers in one run. To address this problem, a multiple heart-cutting chiral-chiral two-dimensional liquid chromatography (2D-LC) method was developed. The multiple heart-cutting 2D-LC separation was implemented on 2D-LC system with three chiral columns with immobilized polysaccharide chiral stationary phases, namely Chiralpak IB, IC and IF3. In the system, the column Chiralpak IB was used as the 1D separation column and IC and IF3 columns were used parallelly for the 2D separation. The twelve stereoisomers were all well separated in one run by the multiple heart-cutting chiral-chiral 2D-LC system.

A silica-based three-dimensional molecularly imprinted coating for the selective solid-phase microextraction of difenoconazole from wheat and fruits samples.

In this work, a selective silica-based molecular imprinted solid-phase microextraction (SPME) sorbent was prepared through the sol-gel process. Difenoconazole was used as a template to prepare imprinted materials on the surface of mesoporous silica. The SPME fiber followed by gas chromatography-electron capture detection was applied for the extraction and determination of difenoconazole. Fourier transform infrared spectrometry, field emission scanning electron microscopy, X-ray diffraction, and thermal gravimetry were used to characterize the imprinted SPME fiber. Two different procedures were presented to prepare MCM-41@SiO2-difenoconazole. Also, a non-MCM molecularly imprinted polymer was synthesized to investigate the effect of MCM-41 on the selectivity and extraction efficiency of the sorbent. The important parameters (i.e., desorption time and temperature, ionic strength, stirring rate, pH, extraction temperature and time) affecting the extraction performance of the method were optimized. Under optimum conditions, the limits of detection and quantification were found to be 0.002 and 0.005 ng mL-1, respectively. Linear dynamic range was in the range of 0.01-1 ng mL-1. The intra- and inter-day relative standard deviations and fiber-to-fiber reproducibility were in the range of 4.3-7.5, 3.3-8.2 and 7.4-9.7%, respectively. The fiber was successfully applied for the selective extraction of difenoconazole from wheat and fruit samples and satisfactory results with extraction recoveries >73% were obtained.

Azo-linked porous organic polymers/polydimethylsiloxane coated stir bar for extraction of benzotriazole ultraviolet absorbers from environmental water and soil samples followed by high performance liquid chromatography-diode array detection.

With 4,4'-diaminoterphenyl and phloroglucinol as the monomers, Azo-linked porous organic polymer (PP) was prepared by a green mild azo reaction. Azo-PP is rich in phenolic hydroxyl groups and benzene rings, which can form intermolecular hydrogen bonds with the phenolic hydroxyl groups in interest benzotriazoles (BZTs). The π-π interaction between the benzene ring and the triazole ring would promote the adsorption of target BZTs on Azo-PP. Azo-PP/polydimethylsiloxane (PDMS) coated stir bar was prepared via sol-gel technique for the extraction of target BZTs. Compared with commercial stir bar, Azo-PP coated stir bar showed superior extraction efficiency (75-88% vs 45-65%) under similar conditions and kinetics (50 min vs 120 or 360 min). A method of stir bar sorptive extraction (SBSE) combined with high performance liquid chromatography (HPLC)-diode array detector (DAD) was developed to analyze six target BZT UltraViolet (UV) absorbers. The optimization of SBSE conditions for extraction of interest BZTs was performed by single-factor test. Under the optimized conditions, the limits of detection within 0.12-0.33 µg/L were achieved for six BZT UV absorbers, with the linear range within 0.5-100 µg/L. The method was applied to detect six BZT UV absorbers in the East Lake water, Yangtze River water, and campus soil samples. No BZT was detected in any of the samples. The recoveries of target BZTs in spiked samples were found in the range of 94.9-118%, 96.2-118%, and 88.2-119%.