Multiple Monolithic Fiber Solid-phase Microextraction Research Articles

Application of novel metal organic framework-deep eutectic solvent/molecularly imprinted polymer multiple monolithic fiber for solid phase microextraction of amphetamines and modafinil in unauthorized medicinal supplements with GC-MS

The goal of this research is the development of multiple monolithic fiber-solid phase microextraction (MMF-SPME) using a new integrated fiber for the determination of amphetamine derivatives and modafinil from unauthorized medicinal supplements. For this purpose, a monolithic fiber of metal organic framework MIL-Al (53)-deep eutectic solvent (DES)/molecularly imprinted polymers (MOF-DES/MIP) was synthesized. To find optimum microextraction conditions gas chromatography-mass spectrometer (GC-MS) was used and the influences of effective variables were investigated using one factor at a time method. After that, the significant variables were optimized using a Box-Behnken design (BBD) combined with a desirability function (DF). Under optimized conditions (desorption solvent=1500 µL of 1-octanol, pH=3.5, extraction time=35 min, [NaCl]=0% w/v and stirring rate=600 rpm), calibration graphs of analytes were linear in a concentration range of 0.1–400 μg L−1 with correlation coefficients > 0.9966. Limits of detection and quantification were in the ranges of 0.023–0.033 μg L−1 and 0.088–0.113 μg L−1, respectively. This procedure was successfully employed in determining target analytes in spiked and unspiked unauthorized medicinal supplement samples with recoveries ranging from 95.14 to 104.63%.

Approach based on multiple monolithic fiber solid-phase microextraction coupled to liquid chromatography-tandem mass spectrometry for sensitive determination of perfluoroalkyl acids in fish and seafood

A sensitive analytical approach using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with multiple monolithic fiber solid-phase microextraction (MMF-SPME) was developed for determination of perfluoroalkyl acids, including perfluorocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs) in fish and seafood. The MMF-SPME based on poly (vinylbenzyltrimethylammonium chloride/dodecafluoroheptyl acrylate-co- ethylenedimethacrylate/divinylbenzene) monolith which contained abundant F atoms and quaternary amine groups was employed to effectively extract studied analytes. Various parameters affecting the extraction performance were investigated in detail. Under the most favorable conditions, the developed method displayed wide linear dynamic ranges with good coefficients of correlation (R2 > 0.99). The limits of detection (LODs) and limits of quantification (LOQs) were in the ranges of 0.0062–1.5 μg/kg and 0.021–5.0 μg/kg, respectively. The relative standard deviation (RSD) values for intra-day and inter-day assay variability were less than 12% for all analytes. The introduced method was successfully applied to detect low levels of PFCAs and PFSAs in the muscle of fish, shrimp and shellfish samples. Recoveries at low, medium and high fortified concentrations were in the ranges of 80.2–119%, and the RSDs varied from 0.3% to 11% for all analytes. The satisfactory results well demonstrate that the developed approach is sensitive and reliable in the monitoring of trace PFCAs and PFSAs in fish and seafood.

A nanocomposite consisting of graphene oxide, zeolite imidazolate framework 8, and a molecularly imprinted polymer for (multiple) fiber solid phase microextraction of sterol and steroid hormones prior to their quantitation by HPLC.

A method is described for multiple monolithic fiber solid-phase microextraction of five sterol and steroid hormones from complex food samples. A composite was prepared from graphene oxide, a metal-organic framework (ZIF-8) and a molecularly imprinted polymers was deposited on a single thin fiber. Four thin fibers were combined to obtain a fiber bundle. The nanocomposite was characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy. The parameters affecting the extraction were optimized by Box-Behnken design. Following elution with methanol, the analytes progesterone, testosterone, β-sitosterol, cholesterol and campesterol were quantified via HPLC. Response is linear in the 0.01-1000μgL-1 concentration range, and limits of detection range from 3 to 5ngL-1. The method was successfully applied to the determination of the five analytes in spiked samples of white meat, egg yolks and vegetables. The relative mean recoveries ranged from 95.0% to 101.0%. Graphical abstract Schematic presentation of a monolith molecularly imprinting polymer (MIP) fiber fabrication for solid phase microextraction (SPME) of sterol and steroid hormones. The fiber was synthesis using graphene oxide and metal-organic framework, ZIF-8, composite by imprinting technique and progesterone as template. Four fibers were combined to obtain a fiber bundle. Then, multiple fiber solid-phase microextraction was employed for determination of analytes by coupling with HPLC/UV detection.

Fabrication of boron-rich multiple monolithic fibers for the solid-phase microextraction of carbamate pesticide residues in complex samples.

To enrich carbamate pesticides from complex matrices, an adsorbent based on poly (vinylboronic anhydride pyridine complex-co-ethylenedimethacrylate) monolith was fabricated and utilized as the extraction phase of multiple monolithic fiber solid-phase microextraction. Due to the abundant boron atoms in the monolith, the B-N coordination interaction between adsorbent and analytes play a key role in the efficient extraction of analytes. Under the optimized conditions, the monolithic fibers were combined with high-performance liquid chromatography for the quantify trace levels of carbamate pesticides in environmental water and orange juice samples. For water sample, the limit of detection and limit of quantification were in the range of 0.017-0.29 and 0.057-0.96μg/L, respectively. The related values in orange juice samples were 0.038-0.39 and 0.12-1.36μg/kg, respectively. Besides, the proposed method also exhibits wide linearity, satisfactory coefficients of determination, and good precision. The introduced approach was successfully applied to determine trace target analytes in real-life samples. The spiked recoveries with different fortified concentrations were in the range of 80.4-117% for water samples and 83.7-119% for fruit juice samples. The relative standard deviations were below 10%. The results evidence that the suggested method was convenient, reliable, and eco-friendly for the monitoring of trace levels of carbamate pesticides in complex samples such as waters and juices.

Sensitive determination of perfluoroalkane sulfonamides in water and urine samples by multiple monolithic fiber solid-phase microextraction and liquid chromatography tandem mass spectrometry

To extract perfluoroalkane sulfonamides (PFASAs) in water and urine samples effectively, a new adsorbent based on poly (1H,1H,2H,2H-nonafluorohexyl acrylate/vinyboronic anhydride pyridine complex-co-ethylenedimethacrylate) monolith (FBE) was synthesized and used as the extraction phase of multiple monolithic fiber solid-phase microextraction (MMF-SPME). Because there are abundant fluorinated (F-) alkyl chains and boron atoms in the adsorbent, the FBE/MMF-SPME displays satisfactory extraction performance for PFASAs by means of fluorophilic and B-N coordination interactions. Under the most favorable conditions, the FBE/MMF-SPME was combined with HPLC-MS/MS for the sensitive monitoring of ultra-trace PFASAs in environmental water and human urine samples. The limits of detection and limits of quantification achieved for target analytes were in the range of 0.13–1.45 ng/L and 0.44–4.80 ng/L, respectively. The developed FBE/MMF-SPME-HPLC-MS/MS method was successfully applied to quantify the level of PFASAs in water and human urine samples, and ultra-trace target PFASAs were detected in the real samples. The recoveries at different fortified concentrations ranged from 80.3% to 119% with RSD in the range of 0.9–11%. Compared with reported methods, the proposed method exhibits some merits such as high sensitivity, good method precision, low consumption of sample and environmental friendliness.

Graphene reinforced multiple monolithic fiber solid-phase microextraction of phenoxyacetic acid herbicides in complex samples

To increase the specific surface area (SSA) of monolith-based adsorbent for the extraction of phenoxyacetic acid herbicides (PAAs) in complex samples, graphene was embedded in an adsorbent based on poly (4-vinylpyridine-co-ethylene glycol dimethacrylate) monolith (GEM). The new adsorbent was employed as extraction phase of multiple monolithic fiber solid-phase microextraction (MMF-SPME). The influences of preparation conditions and extraction parameters on the enrichment performance of GEM/MMF-SPME for PAAs were investigated in detail. Results well indicated that the embedded graphene could obviously enhance the SSA of the adsorbent and introduce π-π electrostatic stacking groups. The prepared GEM/MMF-SPME could extract PAAs effectively by means of π-π electrostatic stacking, hydrophobic, ion-exchange and hydrogen bonding interactions. Under the most favorable conditions, a convenient, sensitive, cost-effective and environmentally friendly method for the determination of trace PAAs in water and rice samples was developed by the combination of GEM/MMF-SPME and high performance liquid chromatography-diode array detection (HPLC-DAD). Results showed that for water sample, the limits of detection (LOD, S/N = 3) and limit of quantification (LOQ, S/N = 10) values were in the range of 0.093–0.12 μg/L and 0.31–0.41 μg/L, respectively. The corresponding values in rice sample were 0.36–0.66 μg/kg and 1.18–2.27 μg/kg, respectively. The proposed method was successfully applied to quantify trace PAAs in water and rice samples. Recoveries achieved for water and rice samples at different spiked concentrations were in the ranges of 70.0–118% and 70.0–117%, respectively. The RSDs varied from 0.3% to 10% for all analytes. The results well revealed the potential application of GEM/MMF-SPME as an effective sample preparation processes for the monitoring of PAAs in water, rice and other complex samples.

Efficient extraction of perfluorocarboxylic acids in complex samples with a monolithic adsorbent combining fluorophilic and anion-exchange interactions

Efficient extraction of perfluorocarboxylic acids (PFCAs) is a key step for the accurate and sensitive determination of PFCAs due to their low concentration and the complexity of sample matrices. Herein, according to the chemical characteristics of PFCAs, a new adsorbent based on poly (2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl acrylate/(vinylbenzyl)trimethylammonium chloride-co-divinylbenzene/ethylenedimethacrylate) monolith was fabricated and utilized as the extraction medium of multiple monolithic fiber solid-phase microextraction (MMF-SPME). Results well indicted that the prepared monolithic adsorbent (MA) could efficient extract PFCAs through fluorophilic and anion-exchange interactions. Under the optimal conditions, the MA/MMF-SPME was combined with HPLC-MS/MS for the sensitive monitoring of ultra-trace PFCAs in water and milks samples. The limits of detection (S/N = 3) of the target PFCAs in water and milk samples were 0.40–4.40 ng/L and 0.9–12.1 ng/L, respectively. Furthermore, the proposed method also exhibited some merits including wide linear dynamic ranges, satisfactory sensitivity, good method precision and low consumption of sample and organic solvent. Isotope internal standard calibration curve method was used to quantify the concentration of PFCAs in real samples, and trace levels of PFCAs in tap water and milk samples had been successfully detected.

Mixed functional monomers-based monolithic adsorbent for the effective extraction of sulfonylurea herbicides in water and soil samples

Effective extraction is a key step in the determination of sulfonylurea herbicides (SUHs) in complicated samples. According to the chemical properties of SUHs, a new monolithic adsorbent utilizing acrylamidophenylboronic acid and vinylimidazole as mixed functional monomers was synthesized. The new adsorbent was employed as the extraction phase of multiple monolithic fiber solid-phase microextraction (MMF-SPME) of SUHs, and the extracted SUHs were determined by high-performance liquid chromatography with diode array detection (HPLC-DAD). Results well evidence that the prepared adsorbent could extract SUHs in environmental waters and soil effectively through multiply interactions such as boronate affinity, dipole-dipole and π-π interactions. Under the optimized extraction conditions, the limits of detection for target SUHs in environmental water and soil samples were 0.018–0.17μg/L and 0.14–1.23μg/kg, respectively. At the same time, the developed method also displayed some analytical merits including wide linear dynamic ranges, good method reproducibility, satisfactory sensitivity and low consume of organic solvent. Finally, the developed were successfully applied to monitor trace SUHs in environmental water and soil samples. The recoveries at three fortified concentrations were in the range of 70.6–119% with RSD below 11% in all cases. The obtained results well demonstrate the excellent practical applicability of the developed MMF-SPME-HPLC-DAD method for the monitoring of SUHs in water and soil samples.

Development of multiple monolithic fiber solid-phase microextraction and liquid chromatography-tandem mass spectrometry method for the sensitive monitoring of aminoglycosides in honey and milk samples.

A simple and sensitive method for the simultaneous extraction and determination of six aminoglycosides in honey and milk samples was developed using multiple monolithic fiber solid-phase microextraction and liquid chromatography with tandem mass spectrometry. The multiple monolithic fibers based on poly(methacrylic acid-co-ethylenedimethacrylate) monolith as the extraction medium was used to concentrate target analytes. Because there were abundant carboxyl groups in the monolith, the monolithic fibers could extract aminoglycosides effectively through cation-exchange and hydrophobic interactions. To obtain optimum extraction performance, several extraction parameters including desorption solvent, adsorption and desorption time, pH value and ionic strength in sample matrix, were investigated in detail. Under the optimized extraction conditions, the limits of detection of the proposed method were 0.10-0.30 and 0.23-0.59μg/kg for honey and milk samples, respectively. Satisfactory linearity was achieved for analytes with the coefficients of determination above 0.99. At the same time, the developed method showed acceptable method repeatability and reproducibility. Finally, the proposed method was successfully applied to the determination of aminoglycosides in real honey and milk samples. Recoveries obtained for the determination of six target analytes in spiking samples ranged from 67.9 to 110%, and the relative standard deviations were in the range of 1.2-11%.

Preparation and evaluation of an adsorbent based on poly (muconic acid-co-divinylbenzene/ethylenedimethacrylate) for multiple monolithic fiber solid-phase microextraction of tetracycline antibiotics

To extract tetracycline antibiotics (TAs) effectively, a new adsorbent based on poly (muconic acid-co-divinylbenzene/ethylenedimethacrylate) monolith was fabricated and used as the extraction medium of multiple monolithic fiber solid-phase microextraction (MD/MF-SPME). The effect of the fabrication parameters on extraction efficiency was studied thoroughly. Elemental analysis, infrared spectroscopy, scanning electron microscopy and mercury intrusion porosimetry were used to check the physicochemical properties of the adsorbent. Some key parameters that affect the extraction performance of MD/MF-SPME for TAs were investigated systematically. Under the optimized experimental conditions, the prepared adsorbent could effectively extract the TAs through multiple interactions. At the same time, a simple and sensitive method for monitoring trace TAs in honey samples was developed by coupling MD/MF-SPME with high-performance liquid chromatography tandem mass spectrometry detection (MD/MF-SPME-HPLC–MS/MS). The limits of detection (S/N=3) for target compounds were in the range of 7.3–17.1ng/kg. The intra-day and inter-day precision (relative standard deviations, n=4, %) at 0.5μg/kg and 20.0μg/kg spiking concentrations were 5.0–9.5% and 3.6–10.0%, respectively. The mean recoveries of the target TAs in the real honey samples were between 70.5–111.0%.

Fabrication and evaluation of a fluorophilic adsorbent for multiple monolithic fiber solid-phase microextraction of fluorobenzenes

A new type of highly fluorinated monolith (HFM) was fabricated and used as adsorbent of multiple monolithic fiber solid-phase microextraction (MMF-SPME). To prepare the HFM, a fluorinated monomer, 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl acrylate was in situ copolymerized with dual cross-linkers (divinylbenzene and ethylenedimethacrylate). The fabrication parameters including the content of monomer and porogenic solvent in the polymerization mixture were optimized to obtain expected extraction performance and life span. The physicochemical properties of the HFM were systematically investigated with elemental analysis, infrared spectroscopy, scanning electron microscopy and mercury intrusion porosimetry. The effective extraction of six fluorobenzenes was selected as a paradigm to demonstrate the fluorophilic characteristic of HFM/MMF-SPME. At the same time, a convenient and effective method for the determination of trace fluorobenzenes in environmental water samples was developed by coupling HFM/MMF-SPME with high performance liquid chromatography/diode array detection (HFM/MMF-SPME-HPLC/DAD). Results indicated that the limits of detection (S/N=3) for targeted compounds were in the range of 1.09–5.88μg/L. The intra-day and inter-day precision (relative standard deviations, n=4, %) at two spiked concentrations were 4.2–10.6% and 6.1–10.8%, respectively. Finally, the developed method was successfully applied to the analysis of fluorobenzenes in spiked real water samples with satisfactory recoveries and repeatability.

Preparation and application of a poly (ionic liquid)-based molecularly imprinted polymer for multiple monolithic fiber solid-phase microextraction of phenolic acids in fruit juice and beer samples.

In this work, a new molecularly imprinted polymer (MIP) using a poly (ionic liquid) (PIL) as a functional monomer was prepared and utilized as the extraction medium of multiple monolithic fiber solid-phase microextraction (MMF-SPME). A PIL, 1-ally-3-vinylimidazolium chloride, was used as a functional monomer, and 3,4-dihydroxybenzenepropanoic acid (DBA) and ethylene dimethacrylate were chosen as the template molecule and cross-linker, respectively, to synthesize the PIL/MIP. Under the optimized preparation conditions, the recognition coefficient of PIL-MIP for DBA was as high as 11.6. The combination of PIL/MIP-MMF-SPME and high-performance liquid chromatography with diode array detection (HPLC/DAD) was developed for the sensitive determination of phenolic acids (PAs) in fruit juice and beer samples. Under the optimal conditions which were investigated in detail, the limits of detection (LODs, S/N = 3) for PAs in fruit juice were 0.024-0.24 μg L-1, and the related values were 0.011-0.052 μg L-1 for the beer sample. The intra-day and inter-day precision (relative standard deviations, n = 4, %) at 1.0 and 100.0 μg L-1 spiking concentration were both less than 10%. In the analysis of PAs in fruit juice and beer samples, satisfactory recoveries and repeatability were achieved. In comparison with reported approaches, the proposed method exhibited some advantages including high selectivity, convenience, satisfactory sensitivity and environmental friendliness.

Fabrication of a polymeric ionic liquid-based adsorbent for multiple monolithic fiber solid-phase microextraction of endocrine disrupting chemicals in complicated samples

A multiple monolithic fiber solid-phase microextraction (MMF-SPME) utilizing polymeric ionic liquid-based adsorbent was prepared. The adsorbent was obtained by in situ copolymerization of an ionic liquid, 1-trimethyl-(4-vinylbenzyl) aminium chloride and dual cross-linkers (divinylbenzene and ethylenedimethacrylate). The effect of preparation conditions including the content of ionic liquid and porogen in the polymerization mixture on extraction performance was studied in detail. Infrared spectroscopy, elemental analysis, scanning electron microscopy and mercury intrusion porosimetry were used to inspect the physicochemical properties of the new adsorbent. The applicability of the new MMF-SPME was demonstrated by the extraction of trace endocrine disrupting chemicals (EDCs). Results indicated that the prepared MMF-SPME could extract EDCs effectively through multi-interactions such as ion-exchange, π-π and hydrophobic interactions. After optimization of extraction parameters, a method of MMF-SPME coupled to high performance liquid chromatography/diode array detection was conducted to detect trace EDCs in complicated samples including environmental water and human urine. The limits of detection (S/N=3) and quantification (S/N=10) for targeted compounds were 0.011–0.065μg/L and 0.036–0.21μg/L, respectively. Satisfactory precision was also achieved by evaluating the repeatability and intermediate precision with relative standard deviations (RSDs) of less than 9% and 10%, respectively. At the same time, the proposed method was successfully applied for the determination of EDCs in water and human urine with spiking recoveries ranged from 70.6% to 119%.

Facile preparation of a polydopamine-based monolith for multiple monolithic fiber solid-phase microextraction of triazine herbicides in environmental water samples.

A new multiple monolithic fiber solid-phase microextraction using a polydopamine-based monolith as the extraction medium is proposed. The monolith was synthesized by facile in situ copolymerization of N-methacryldopamine and dual cross-linkers (divinylbenzene/ethylenedimethacrylate) in the presence of N,N-dimethylformamide. The effect of the contents of N-methacryldopamine and porogen in the polymerization mixture on the extraction performance was investigated thoroughly. A series of characterization studies was performed to validate the structure and properties of the monolith. The prepared multiple monolithic fibers were used for the extraction of triazine herbicides in environmental water samples. After the optimization of the extraction parameters, a convenient, sensitive, cost-effective, and environmentally friendly method for the determination of trace triazine herbicides in water samples was developed by coupling multiple monolithic fibers solid-phase microextraction with high-performance liquid chromatography and diode array detection. The results indicated that the limits of detection and quantification for the target compounds were 0.031-0.14 and 0.10-0.45 μg/L, respectively. Good precision and reproducibility were obtained with the relative standard deviations below 10%. The developed method was applied to the analysis of the triazine herbicides in different water samples (lake, river, and farmland waters). The recoveries of the method were in the range between 79.6 and 117%.

Determination of trace phenolic acids in fruit juice samples using multiple monolithic fiber solid-phase microextraction coupled with high-performance liquid chromatography

A simple and sensitive analytical approach of MMF/SPME-LD-HPLC/DAD was proposed for the determination of trace level of phenolic acids in fruit juice samples.

Multiple monolithic fiber solid-phase microextraction based on a polymeric ionic liquid with high-performance liquid chromatography for the determination of steroid sex hormones in water and urine.

The development of a simple and sensitive analytical approach that combines multiple monolithic fiber solid-phase microextraction with liquid desorption followed by high-performance liquid chromatography with diode array detection is proposed for the determination of trace levels of seven steroid sex hormones (estriol, 17β-estradiol, testosterone, ethinylestradiol, estrone, progesterone and mestranol) in water and urine matrices. To extract the target analytes effectively, multiple monolithic fiber solid-phase microextraction based on a polymeric ionic liquid was used to concentrate hormones. Several key extraction parameters including desorption solvent, extraction and desorption time, pH value and ionic strength in sample matrix were investigated in detail. Under the optimal experimental conditions, the limits of detection were found to be in the range of 0.027-0.12 μg/L. The linear range was 0.10-200 μg/L for 17β-estradiol, 0.25-200 μg/L estriol, ethinylestradiol and estrone, and 0.50-200 μg/L for the other hormones. Satisfactory linearities were achieved for analytes with the correlation coefficients above 0.99. Acceptable method reproducibility was achieved by evaluating the repeatability and intermediate precision with relative standard deviations of both less than 8%. The enrichment factors ranged from 54- to 74-fold. Finally, the proposed method was successfully applied to the analysis of steroid sex hormones in environmental water samples and human urines with spiking recoveries ranged from 75.6 to 116%.

Monitoring of selected estrogen mimics in complicated samples using polymeric ionic liquid-based multiple monolithic fiber solid-phase microextraction combined with high-performance liquid chromatography

A convenient, rapid, sensitive and environmentally friendly method for simultaneous monitoring of six estrogen mimics (bisphenol A, diethylstilbestrol, dienestrol, hexestrol, octylphenol and nonylphenol) in water and milk samples was developed by coupling multiple monolithic fiber solid-phase microextraction (MMF-SPME) to high performance liquid chromatography with diode array detection. The MMF-SPME based on polymeric ionic liquid-based monolith as extractive medium was used to concentrate target analytes. Because there were multiple interactions between adsorbent and analytes, the MMF-SPME exhibited a high extractive capability toward analytes. To obtain optimum extraction performance, several extraction parameters including desorption solvent, pH value and ionic strength in sample matrix, extraction and desorption time were investigated and discussed. Under the optimized extraction conditions, the limits of detection (S/N=3) of the proposed method were 0.040–0.11μg/L in water and in milk samples. Satisfactory linearity was achieved for analytes with the correlation coefficients (r) above 0.99. Excellent method reproducibility was achieved by evaluating the repeatability, intermediate precision and MMF-to-MMF reproducibility with relative standard deviations (RSDs) of both less than 10%. Finally, the proposed method was successfully applied to the determination of estrogen mimics in several milk and environmental water samples. Recoveries obtained for the determination of six target analytes in spiking samples ranged from 75.6% to 118%, with RSD below 10% in all cases.

Sensitive monitoring of benzoylurea insecticides in water and juice samples treated with multiple monolithic fiber solid-phase microextraction and liquid chromatographic analysis

In present study, a convenient, sensitive and environmentally friendly method for the determination of five benzoylurea insecticides (BUs) in water and juice samples was developed. To extract trace benzoylurea insecticides effectively, poly(methacrylic acid-co-ethylene dimethacrylate) monolith was prepared and used as the sorbent of multiple monolithic fiber solid-phase microextraction (MMF-SPME). The influences of preparation conditions of monolith and extraction parameters of MMF-SPME on BUs were studied thoroughly. Under the optimized conditions, the combination of MMF-SPME with high performance liquid chromatography-diode array detection (MMF-SPME-HPLC-DAD) showed expected analytical performance for target analytes. The limits of detection (S/N=3) of the developed method were 0.026–0.075μgL−1 in water and 0.053–0.29μgL−1 in juice samples. Good linearity was obtained for analytes with the correlation coefficients (R2) above 0.99. Satisfactory repeatability and reproducibility was achieved, with relative standard deviations (RSD) of both less than 10%. Finally, the established MMF-SPME-HPLC-DAD method was successfully applied for the determination of BUs residues in juice and environmental water samples. Recoveries obtained for the determination of BUs in spiking samples ranged from 65.1% to 118%, with RSD below 10% in all cases.

Sensitive monitoring of trace nitrophenols in water samples using multiple monolithic fiber solid phase microextraction and liquid chromatographic analysis

In this work, a simple, efficient and environmentally friendly method—multiple monolithic fiber solid-phase microextraction (MMF-SPME) combining with high-performance liquid chromatography (HPLC) was first established for the determination of six trace nitrophenols in water samples. In order to prepare MMF-SPME, 1-allyl-3-methylimidazolium bis [(trifluoro methyl) sulfonyl] imide was co-polymerized with ethylene dimethacrylate to get single thin fiber (0.5mm in diameter). Subsequently, four thin fibers were bound together to obtain the MMF-SPME. The effect of preparation conditions of MMF-SPME on the extraction performance was investigated in detail. In order to obtain the optimal extraction conditions of MMF-SPME for nitrophenols, several extractive parameters, including desorption solvent, extraction and desorption time, pH values and ionic strength in sample matrix were optimized. Under the optimum conditions, the linear ranges of 4-nitrophenol, 2,4-dinitrophenol, 5-methyl-2-nitrophenol, 5-methoxyl-2-nitrophenol were 0.5–200µg/L and 1.0–200µg/L for 2-nitrophenol and 4-tertbutyl-2-nitrophenol. The limits of detection (S/N=3) for the target analytes were 0.075–0.27µg/L. At the same time, excellent method reproducibility was achieved in terms of intra- and inter-day precisions, indicated by the RSDs of both <10.0%, respectively. Finally, the proposed method was successfully used to detect nitrophenols in different environmental water samples. Satisfactory recoveries ranged from 82.6% to 116% and the RSDs for reproducibility were less than 10% for target analytes in all real samples.

Multiple monolithic fiber solid-phase microextraction: A new extraction approach for aqueous samples

A novel multiple monolithic fiber solid-phase microextraction (MMF-SPME) was designed and prepared. Two steps were involved in the preparation of MMF-SPME. Firstly, single thin fiber (0.5mm in diameter) was prepared by co-polymerization of vinylimidazole and ethylene dimethacrylate. Secondly, several thin fibers were bound together to obtain the MMF assembly. The extraction and desorption dynamics of MMF-SPME with different numbers of fibers were studied in detail. In order to demonstrate the usability of the new MMF-SPME, the extraction performance of MMF-SPME for 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol was investigated in direct SPME mode. Results indicated that aqueous samples could form convection effectively within MMF-SPME because there were gaps between fibers. The extraction procedure was accelerated by the convection. At the same time, the MMF-SPME possessed high extraction capacity because more sorbent was employed. Under the optimized extraction conditions, low detection limits (S/N=3) and quantification limits (S/N=10) for the target analytes were achieved within the range of 0.13–0.29μg/L and 0.44–0.98μg/L, respectively. The MMF-SPME also showed a very long lifespan and good repeatability. Finally, the MMF-SPME was successfully applied to the analysis of tap, lake and ground water samples with spiked recoveries in the range of 73.8–101%.