Huaixia Chen

A novel dispersive solid-phase extraction method using metal-organic framework MIL-101 as the adsorbent for the analysis of benzophenones in toner

Metal-organic frameworks (MOFs) have been paid widespread attention in the field of adsorption and separation materials due to its porosity, large specific surface area, unsaturated metal-ligand sites and structural diversity. In this study, the green powder MIL-101 was synthesized and used for the extraction of benzophenone, 2,4-dihydroxybenzophenone and 2-hydroxy-4-methoxy-benzophenone from toner samples for the first time. The synthesized MIL-101 was characterized by X-ray diffraction, scanning electron microscopy, thermogravimetry and nitrogen adsorption porosimetry. The MIL-101 was applied as the dispersive solid phase extraction (DSPE) adsorbent for the extraction and preconcentration of benzophenone, 2,4-dihydroxybenzophenone and 2-hydroxy-4-methoxy-benzophenone from toner samples. The extraction conditions were investigated. Under the optimized conditions, a DSPE-HPLC method for the determination of benzophenone, 2,4-dihydroxybenzophenone and 2-hydroxy-4-methoxy-benzophenone was developed. The method yielded a linear calibration curve in the concentration ranges from 4.0 to 3500 μg L(-1) for the three analytes in toner samples with regression coefficients (r(2)) of 0.9992, 0.9999 and 0.9990, respectively. Limits of detection were 1.2, 1.2 and 0.9 μg L(-1), respectively. Both the intra-day and inter-day precisions (RSDs) were <10%.

Preparation of Molecularly Imprinted Polymer Monolith with an Analogue of Thiamphenicol and Application to Selective Solid-Phase Microextraction

A molecularly imprinted polymer (MIP) monolith has been prepared and characterized. Its application to the assay of thiamphenicol in milk with high-performance liquid chromatography–photodiodes array detector was validated. The newly developed MIP monolith was produced using an analogue to thiamphenicol as the template molecule to avoid major traditional drawback associated with MIPs of residual template bleeding. The MIP monolith synthesized in a micropipette tip could be connected with syringes in different sizes simply to perform solid-phase microextraction process without any other treatment. This molecularly imprinted polymer monolith microextraction (MIPMME) method showed high selectivity and enrichment ability for thiamphenicol (TAP). Several parameters affecting MIPMME were investigated, including the flow rate, volume, pH and salt concentration of sample, the type and volume of washing solution, and the type and flow rate of eluent. The recovery of this method for TAP was investigated and high recoveries of 93.5 ~ 96.8% from milk were obtained with relative standard deviations less than 6.3%.

Preparation, characterization and application of organic–inorganic hybrid caffeine imprinted monolith

The present work aims to synthesize an organic-inorganic hybrid caffeine imprinted monolith using one-step method. The synthesis conditions such as the type of inorganic precursor and porogenic solvent, the molar ratios of the monomer and cross-linker, the volume ratio of the inorganic alcoholysate and organic part were optimized. The morphology of the monolith was studied by scanning electron microscopy and Fourier transform infrared spectra. The imprinted factor of the monolith for caffeine reached 3.02. A simple, rapid and sensitive method for the determination of caffeine in childrens milk using the organic-inorganic hybrid caffeine imprinted polymer monolith microextraction combined with high-performance liquid chromatography-photodiodes array detector was developed. Several parameters affecting the sample pretreatment were investigated, including the type, flow rate and volume of eluent, the flow rate and volume of sample solution. The assay exhibited a linear dynamic range of 8-500μgL(-1) with the correlation coefficient above 0.9987. Lower limits of detection (LOD, at S/N=3) and quantification (LOQ, at S/N=10) in childrens milk samples were 2.7 and 8μgL(-1). Recoveries of caffeine from spiked childrens milk ranged from 85 to 104% with relative standard deviations of less than 8.9%.

A molecularly imprinted organic–inorganic hybrid monolithic column for the selective extraction and HPLC determination of isoprocarb residues in rice

An IPC-imprinted (IPC is isoprocarb) poly(methacrylic acid)/SiO2 hybrid monolithic column was prepared and applied for the recognition of the template. The hybrid monolithic column was synthesized in a micropipette tip using methyltrimethoxysilane as the inorganic precursor, 3-(methacryloxy)propyltrimethoxysilane as the coupling agent, and ethylene glycol dimethacrylate as the cross-linker. The synthesis conditions, including the porogenic solvent, coupling agent, volume ratio of the inorganic alcoholysate and organic part, were optimized. The prepared monolithic column was characterized by SEM and FTIR spectroscopy. A simple, rapid, and sensitive method for the determination of IPC in rice using the imprinted monolithic column microextraction combined with HPLC was developed. Several parameters affecting the sample pretreatment were investigated, including the eluent, washing solution, and loading sample volume. The linearity of the calibration curve was observed in the range of 9.0-1000 μg/kg for IPC in rice with the correlation coefficient (r2) of 0.9983. The LOD was 3.0 μg/kg (S/N = 3). The assay gave recovery values ranging from 91 to 107%. The proposed method has been successfully applied for the selective extraction and sensitive determination of IPC in rice and a satisfactory result was obtained.

Structural elucidation of in vivo and in vitro metabolites of epiberberine in rat and its liver and intestines by liquid chromatography-tandem mass spectrometry.

The in vivo and in vitro metabolism of epiberberine was investigated using a highly specific and sensitive liquid chromatography–mass spectrometry (LC–MS/MS) method. In vivo samples including rat urine, feces, and plasma samples were collected individually after ingestion of 35 mg/kg epiberberine to healthy rats. In vitro samples were prepared by incubating epiberberine with homogenized liver and intestinal flora of rats, respectively. As a result, at least 17, 3 and 5 metabolites were found in rat urine, feces, and plasma, respectively. Additionally, 1 and 3 metabolites were found in the rat intestinal flora and homogenized liver incubation mixtures, respectively.

Ultra Preconcentration of Polycyclic Aromatic Hydrocarbons in Smoked Bacon by a Combination of SPE and DLLME

A sample pretreatment method, solid-phase extraction combined with dispersive liquid-liquid microextraction (SPE-DLLME), was established for the sensitive determination of polycyclic aromatic hydrocarbons (PAHs) in smoked bacon samples. In the SPE-DLLME process, three PAHs including naphthalene (Naph), phenanthrene (Phen) and pyrene (Pyr) were extracted from samples and transferred into C18 SPE cartridge. The target analytes were subsequently eluted with 1.2 ml of acetonitrile-dichloromethane (5:1, v/v) mixture solution. The eluent was injected directly into the 5.0 ml ultrapure water in the subsequent DLLME procedure. The sedimented phase was concentrated under a gentle nitrogen flow to 120.0 µl. Finally, the analytes in the extraction solvent were determined by high-performance liquid chromatography with a ultra-violet detector. Some important extraction parameters affecting the performance, such as the sample solution flow rate, breakthrough volume, salt addition as well as the type and volume of the elution solvent were optimized. The developed method provided an ultra enrichment factors for PAHs ranged from 3478 to 3824. The method was applied for the selective extraction and sensitive determination of PAHs in smoked bacon samples. The limits of detection (S/N = 3) were 0.05, 0.01, 0.02 μg kg(-1) for Naph, Phen, Pyr, respectively.

SOLID-PHASE EXTRACTION FOLLOWED BY DISPERSIVE LIQUID–LIQUID MICROEXTRACTION FOR THE SENSITIVE DETERMINATION OF CARBAMATES IN ENVIRONMENTAL WATER BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

A new sample pretreatment method, solid-phase extraction combined with dispersive liquid–liquid microextraction (SPE-DLLME), was established for the sensitive determination of carbamates in environmental water samples. Three carbamates (carbofuran, carbaryl, and pirimicarb) were extracted from water samples by SPE. After the elution of the desired compounds from the sorbent using acetonitrile, DLLME technique was performed on the obtained solution. The analytes were determined by high performance liquid chromatography. The method provided ultra-enrichment factors for carbamates and ranged from 5408 to 7647. The calibration curves were linear in the range of 0.05–5 µg L−1 for carbofuran and carbaryl, and 0.01–5 µg L−1 for pirimicarb in water, respectively. The limits of detection (LODs) were in the ranges of 0.001–0.01 µg L−1. The proposed method was successfully applied for the selective extraction and determination of carbamates in environmental water samples.

Characterization of metabolites of worenine in rat biological samples using liquid chromatography-tandem mass spectrometry.

The in vivo and in vitro metabolites of worenine in rat were identified or characterized using a specific and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. In vivo samples including rat urine, feces, and plasma samples were collected after ingestion of 25 mg/kg worenine to healthy rats. The in vivo and in vitro samples were cleaned up by a solid-phase extraction procedure (C18 cartridges) and a liquid-liquid extraction procedure, respectively. Then these pretreated samples were injected into a reversed-phase C18 column with mobile phase of methanol-ammonium acetate (2mM, adjusted to pH 3.5 with formic acid) (60:40, v/v) and detected by an on-line MS/MS system. As a result, at least twenty-seven metabolites and the parent medicine were found in rat urine after ingestion of worenine. Seven metabolites and the parent medicine were identified or characterized in rat feces. Three metabolites and the parent medicine were detected in rat plasma. One metabolite was found in the rat intestinal flora incubation mixture, and three metabolites were characterized in the homogenized liver incubation mixture. The main phase I metabolism of worenine in rat was dehydrogenization, hydrogenation, hydroxylation, and demethylene reactions, and that of phase II was sulfation and glucuronidation.

Characterization of in vivo and in vitro Metabolic Pathway of Anisodamine by Liquid Chromatography‐Tandem Mass Spectrometry

Abstract In vivo and in vitro metabolisms of anisodamine were investigated using a highly specific and sensitive LC‐MSn method. Feces, urine, and plasma samples were collected individually after ingestion of 25 mg/kg anisodamine to healthy rats. Rat feces and urine samples were cleaned up by a liquid‐liquid extraction and a solid phase extraction procedure (C18 cartridges), respectively. Methanol was added to rat plasma samples to precipitate plasma proteins. Anisodamine was incubated with homogenized liver and intestinal flora of rats in vitro, respectively. The metabolites in the incubation solution were extracted with ethyl acetate. Then, these pretreated in vivo and in vitro samples, were injected into a reversed‐phase C18 column with mobile phase of methanol/0.01% triethylamine solution (adjusted to pH 3.5 with formic acid) (60:40, v/v) and detected by an on‐line MSn system. Identification and structural elucidation of the metabolites were performed by comparing their changes in molecular masses (ΔM), retention times and full scan MSn spectra with those of the parent drug. Fifteen new metabolites (aponoranisodamine, apoanisodamine, methoxyanisodamine, hydroxy‐methoxyanisodamine, trihydroxyanisodamine, dimethoxyanisodamine, dihydroxy‐methoxyanisodamine, tetrahydroxyanisodamine, hydroxy‐dimethoxyanisodamine, trihydroxy‐methoxyanisodamine, dihydroxy‐dimethoxyanisodamine, tetrahydroxy‐methoxyanisodamine, trihydroxy‐dimethoxyanisodamine, dihydroxy‐trimethoxyanisodamine, and hydroxy‐tetramethoxyanisodamine) were identified in rat urine after ingesting anisodamine. Seven metabolites (nor‐6β‐hydroxytropine, 6β‐hydroxytropine, tropic acid, aponoranisodamine, apoanisodamine, noranisodamine, and anisodamine N‐oxide) and the parent drug were detected in rat feces. Six metabolites (nor‐6β‐hydroxytropine, 6β‐hydroxytropine, tropic acid, apoanisodamine, hydroxyanisodamine, and anisodamine N‐oxide) and the parent drug are detected in rat plasma. Only apoanisodamine was detected in the homogenized liver incubation mixture. The hydrolyzed metabolites (6β‐hydroxytropine and tropic acid) and the dehydrated metabolite of anisodamine were found in the rat intestinal flora incubation mixture.

One-pot preparation of an acryloyled β-cyclodextrin-silica hybrid monolithic column and its application for determination of carbendazim and carbaryl

This work describes, for the first time, an acryloyled β-cyclodextrin hybrid monolith column was synthesized, under aqueous-phase conditions, and used for solid-phase microextraction of carbendazim and carbaryl. The monolithic column was characterized using scanning electron microscopy, nitrogen adsorption-desorption, thermogravimetric analysis and Fourier transform infrared spectroscopy, and used as the adsorbent for solid phase microextraction (SPME) of carbendazim and carbaryl. After optimization of the SPME conditions, a simple and sensitive SPME-HPLC method was developed for the determination of carbendazim and carbaryl in leafy vegetables. The method exhibited a good liner response in the range 5-400 μg/kg (R2 = 0.9994) for carbendazim and 10-400 μg/kg (R2 = 0.9996) for carbaryl, respectively. The limits of detection were 1.0 and 1.5 μg/kg for carbendazim and carbaryl, respectively, in leafy vegetables. Recoveries ranged from 92.6% to 110.1%, and the relative standard deviations were less than 6.1%.