Xiaojia Huang

Direct enrichment of phenols in lake and sea water by stir bar sorptive extraction based on poly (vinylpyridine-ethylene dimethacrylate) monolithic material and liquid chromatographic analysis

A poly (vinylpyridine-ethylene dimethacrylate) monolithic material was synthesized and selected as stir bar sorptive extraction (SBSE) medium. The influences of polymerization conditions on the extraction efficiency were investigated using phenol and p-nitrophenol as target analytes. Based on this, six strongly polar phenols in water were directly concentrated by the new SBSE and determined with high performance liquid chromatography equipped with diode array detector. To achieve the optimum extraction performance, several main parameters, including extraction and desorption time, pH value and contents of inorganic salt in the sample matrix were investigated. The method showed good linearity and acceptable recoveries, as well as advantages such as sensitivity, simplicity, low cost and high feasibility. The proposed method was successfully applied to the determination of phenolic compounds in lake and sea waters.

Simple and sensitive monitoring of sulfonamide veterinary residues in milk by stir bar sorptive extraction based on monolithic material and high performance liquid chromatography analysis

A simple, rapid, and sensitive method for the quantitative monitoring of five sulfonamide antibacterial residues (SAs) in milk was developed by stir bar sorptive extraction (SBSE) coupling to high performance liquid chromatography with diode array detection. The analytes were concentrated by SBSE based on poly (vinylimidazole-divinylbenzene) monolithic material as coating. The extraction procedure was very simple, milk was diluted with water then directly sorptive extraction without elimination of fats and protein in samples was required. To achieve optimum extraction performance for SAs, several parameters, including extraction and desorption time, desorption solvent, ionic strength and pH value of sample matrix were investigated. Under the optimized experimental conditions, low detection limits (S/N=3) quantification limits (S/N=10) of the proposed method for the target compounds were achieved within the range of 1.30-7.90 ng/mL and 4.29-26.3 ng/mL from spiked milk, respectively. Good linearities were obtained for SAs with the correlation coefficients (R(2)) above 0.996. Finally, the proposed method was successfully applied to the determination of SAs compounds in different milk samples and satisfied recoveries of spiked target compounds in real samples were obtained.

Development and validation of stir bar sorptive extraction of polar phenols in water followed by HPLC separation in poly(vinylpyrrolididone-divinylbenzene) monolith

An effective and simple method for polar phenols in water matrix was developed by using stir bar sorptive extraction (SBSE) based on a hydrophilic poly(vinylpyrrolididone-divinylbenzene) (VPDB) monolithic material and HPLC analysis. To achieve optimum extraction performance for phenols, several parameters, including extraction and desorption time, desorption solvent, pH value, and ionic strength of sample matrix, were investigated. Under the optimized experimental conditions, eight phenols were directly enriched from water samples and analyzed by HPLC-DAD. The detection limits (S/N = 3) and quantification limits (S/N = 10) of the proposed method for the target compounds were achieved within the range of 0.72-1.37 and 2.40-4.27 ng/mL from spiked water, respectively. Recoveries of eight phenolic compounds were found in the range of 55.2-95.9%. The calibration curves showed the linearity ranging from 5 to 150 ng/mL with linear regression coefficient R(2) values above 0.98. Method repeatability presented as intra- and interday precisions were also found with the RSDs less than 4.10 and 7.61%, respectively. The distribution coefficients between VPDB and water (K(VPDB/W)) for phenolic compounds were also calculated and compared with K(O/W). Finally, the proposed method was successfully applied to the determination of the target compounds in tap water, sea water and wastewater samples.

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 0.040-0.11 μg/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.

Novel extraction approach for liquid samples: Stir cake sorptive extraction using monolith

In this study, a new extraction approach for liquid samples--stir cake sorptive extraction using monoliths as extractive medium was developed. The preparation procedure of stir cake is very simple. First, monolithic cake is synthesized according to the in situ polymerization of monolith; then, the cake is inserted in an original unit (holder), which is constructed from a syringe cartridge and allows the magnetic stirring of the cake during the extraction process. The effects of dimension of monolithic cake and unit design on the extraction performance were optimized in detail. To demonstrate the usability of this new extraction approach, poly(vinylimidazole-divinylbenzene) was prepared and acted as the extractive cake. The analysis of steroid hormones in milk samples by the combination of stir cake with high-performance liquid chromatography with diode array detection, was selected as a paradigm for the practical evaluation of stir cake sorptive extraction. Under the optimized extraction conditions, low detection limits (S/N=3) and quantification limits (S/N=10) of the proposed method for the target analytes were achieved within the range between 0.33-0.69 and 1.08-2.28 μg/L, respectively. The method also showed good linearity, repeatability, high feasibility and acceptable recoveries. Because the monolithic cake does not contact with the vessel wall during stirring, there is no friction loss of extractive medium and the stir cake can be used for more than 1000 h.

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 0.13-0.29 μg/L and 0.44-0.98 μg/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%.

A new anionic exchange stir bar sorptive extraction coating based on monolithic material for the extraction of inorganic anion.

A novel anionic exchange stir bar sorptive extraction (SBSE) coating based on poly(2-(methacryloyloxy)ethyltrimethylammonium chloride-co-divinylbenzene) monolithic material for the extraction of inorganic anion was prepared. The effect of preparation conditions such as ratio of functional monomer to cross-linker, content of porogenic solvent on the extraction efficiencies were investigated in detailed. The monolithic material was characterized by elemental analysis, scanning electron microscopy and infrared spectroscopy. In order to investigate the extraction capacity of the new coating for inorganic anion, the new SBSE was combined with ionic chromatography with conductivity detection, Br-, NO3-, PO4(3-) and SO4(2-) were selected as detected solutes. Several extractive parameters, including pH value and ionic strength in sample matrix, desorption solvent, extraction and desorption time were optimized. The results showed that strongly ionic strength did not favor the extraction of anlaytes. Under the optimum experimental conditions, low detection limits (S/N=3) and quantification limits (S/N=10) of the proposed method for the target anions were achieved within the range of 0.92-2.62 and 3.03-9.25 microg/L, respectively. The method also showed good linearity, simplicity, practicality and low cost for the extraction inorganic anions. Finally, the proposed method was successfully used to detect the two different trademarks of commercial purified water with satisfactory recovery in the range of 70.0-92.6%. To the best of our knowledge, this is the first to use SBSE to enrich inorganic anions.

Preparation of a new polymeric ionic liquid-based monolith for stir cake sorptive extraction and its application in the extraction of inorganic anions

In this study, a novel stir cake sorptive extraction (SCSE) sorbent based on polymeric ionic liquid-based monolith (PILM) for the extraction of inorganic anions was prepared. In the presence of a porogen solvent containing 1-propanol and dimethylformamid, an ionic liquid, 1-ally-3-methylimidazolium chloride was used as monomer to copolymerize in situ with ethylene dimethacrylate to form PILM. The effect of preparation conditions such as ratio of functional monomer to cross-linker, content of porogenic solvent on the extraction efficiencies were investigated in detail. The PILM was characterized by elemental analysis, scanning electron microscopy, mercury intrusion porosimetry and infrared spectroscopy. In order to investigate the extraction capacity of PILM-SCSE for inorganic anions, the SCSE was combined with ion chromatography with conductivity detection, F(-), Cl(-), NO(2)(-), Br(-), NO(3)(-), PO(4)(3-) and SO(4)(2-) were selected as detected solutes. Several extractive parameters, including pH values in sample matrix, desorption solvent, extraction and desorption time were optimized. The results showed that under the optimum experimental conditions, low detection limits (S/N=3) and quantification limits (S/N=10) of the proposed method for the target anions were achieved within the range of 0.11-2.08 and 0.37-6.88 μg/L, respectively. The method also showed good linearity, simplicity, practicality and low cost for the extraction inorganic anions. Finally, the proposed method was successfully used to detect different water samples include commercial purified water, tab water and river water. Acceptable recoveries and satisfactory repeatability were obtained. To the best of our knowledge, this is the first to use polymeric ionic liquid to enrich inorganic anions.

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 0.026-0.075 μg L(-1) in water and 0.053-0.29 μg L(-1) in juice samples. Good linearity was obtained for analytes with the correlation coefficients (R(2)) 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.

Simple and sensitive determination of nitroimidazole residues in honey using stir bar sorptive extraction with mixed mode monolith followed by liquid chromatography

In the present study, we developed a simple and sensitive method for the simultaneous determination of metronidazole (MTZ), ronidazole (RNZ), dimetridazole (DMZ), and tinidazole (TNZ) in honey. Honey samples were diluted with water, then directly treated by stir bar sorptive extraction (SBSE) based on poly(methacrylic acid-3-sulfopropyl ester potassium salt-co-divinylbenzene) monolithic material. The analytes were analyzed by HPLC equipped with diode array detector. In the optimized process, several parameters, including the composition of desorption solvent, pH value and ionic strength in sample matrix, extraction, and desorption time, were investigated in detail. Under the optimized conditions, the detection limits (S/N=3) and quantification limits (S/N=10) of the proposed method for the target compounds were achieved within the range of 0.47-1.52 and 1.54-5.0 μg/kg from spiked honey sample, respectively. The calibration curves showed the linearity ranging from 2 to 200 μg/kg for dimetridazole and tinidazole, 5-200 μg/kg for metronidazole and ronidazole. Method repeatability presented as intra- and interday precisions were found with the RSDs <4.43 and 4.41%, respectively. Finally, the developed method was successfully applied to the determination of nitroimidazoles in different honey samples and satisfactory recoveries of spiked target compounds were in the range of 71.1-114%.