Selective and fast removal and determination of ß-lactam antibiotics in aqueous solution using multiple templates imprinted polymers based on magnetic hybrid carbon material.

Selective and fast adsorption of five broad-spectrum ß-lactam antibiotics included amoxicillin, cephalexin, cefazolin, penicillin G and oxacillin was achieved by novel surface molecular imprinting polymers (MIPs) with magnetic hybrid carbon material as the substrate. The characteristics of MIPs were studied by scanning electron microscope, Fourier transform infrared spectrometer, thermogravimetric analysis, etc. And through a series of adsorption experiments to examine the kinetics, isotherms, thermodynamics, selectivity and reusability for sorption of ß-lactam antibiotics onto the MIPs. The adsorption equilibriums were accomplished in about 60 min with adsorption capacities of 4.57-24.55 mg g-1, while the adsorption process was preferably fitted with pseudo-second-order kinetic model and Freundlich model. The imprinting factors ranged from 1.88 to 9.94 indicated the MIPs possessed excellent recognition ability, and its good reusability was demonstrated after five times adsorption-desorption cycles without a large drop in adsorption capacity. Furthermore, a new detection method was developed by combining of MIPs with solid phase extraction and high performance liquid chromatography (MIPs-SPE-HPLC). Under the optimal SPE conditions, the limits of detection (LODs) for the five BLAs were 0.24-0.56 µg L-1, with RSDs of 0.76-5.39%. The synthesized MIPs and the proposed MIPs-SPE-HPLC method can be applied for the efficient, simultaneous separation and detection of BLAs.

Highly selective removal and recovery of Ni(II) from aqueous solution using magnetic ion-imprinted chitosan nanoparticles.

Nickel (Ni) is one of the most common heavy metals. In this study, nano-sized magnetic ion-imprinted polymers (MIIPs) were synthesized using chitosan as the functional monomer, and used for selective adsorption and recovery of Ni(II) from solutions. The results showed MIIPs possessed high sorption selectivity for Ni(II), and the change in pH (5.0-9.0) exerted insignificant influence on the ion adsorption, allowing almost complete elution and recovery of adsorbed Ni(II) ions by using 0.5% EDTA-Na solution. Moreover, the sorption capacity of the recycled MIIPs decreased by only about 10% after 15 adsorption-desorption cycles. The time required for establishing the adsorption equilibrium was less than 1 h. The sorption process was predominant and endothermic, and could be well described by both Langmuir isotherm model and pseudo-second-order kinetic model. Therefore, the synthesized MIIPs was a suitable adsorbent for highly selective, fast and efficient removal and recovery of low-concentration Ni(II) ions from wastewaters.

Effects of prepolymerization on surface molecularly imprinted polymer for rapid separation and analysis of sulfonamides in water.

This work systematically investigated the effects of prepolymerization on the property of multi-templates surface molecularly imprinted polymer (MIP), which was utilized to quickly and simultaneously separate and detect six sulfonamides (sulfadiazine, sulfathiazole, sulfamerazine, sulfamethazine, sulfamethoxazole and sulfadoxine) in real waters. The MIPs were prepared using the six sulfonamides as the templates, mesoporous silica supported onto the surface of magnetic graphene oxide as the carrier and 4-vinylbenzoic as the functional monomer, with and without prepolymerization of templates with functional monomer. The preparation and adsorption conditions were optimized. It was found that the adsorption capacities of the selected six sulfonamides on the MIP (pre) prepared with prepolymerization were apparently higher than those on the MIP (no pre) synthesized without prepolymerization. Subsequently, the MIPs were utilized as adsorbents for SPE of these sulfonamides, and coupled with high performance liquid chromatography (HPLC) for the determination of sulfonamides. The developed analytical method showed outstanding applicability for the detection of trace sulfonamides in real water samples. The spiked recoveries and relative standard deviations (RSDs) of the six sulfonamides using MIP (no pre) and MIP (pre) were 73.34-99.43% and 87.37-102.34%, 2.28-7.77% and 3.18-6.49%, respectively.

Multi-templates surface molecularly imprinted polymer for rapid separation and analysis of quinolones in water.

Rapid separation and analysis of trace quinolones (fleroxacin (FLRX), enoxacin (EN), norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENRO), and lomefloxacin hydrochloride (LOME)) in real water samples were achieved by using a multi-templates molecularly imprinted polymer (MIP) based solid phase extraction (SPE) coupled with dispersive liquid-liquid microextraction (DLLME) followed by high performance liquid chromatography (HPLC). The MIP was prepared via surface molecular imprinting, using the selected quinolones as the templates and mesoporous silica modified magnetic graphene oxide as the carrier. The preparation and adsorption conditions were optimized. The MIP presented high adsorption capacity and wonderful selective recognition for the quinolones, with the adsorption capacities of 20.15, 20.88, 18.01, 20.01, 16.98, and 17.09 mg/g for FLRX, EN, NOR, CIP, ENRO, and LOME, respectively. Meanwhile, a SPE-DLLME-HPLC method for trace detection of FLRX, EN, NOR, CIP, ENRO, and LOME in real water samples was developed and showed outstanding applicability. The spiked recoveries and relative standard deviations (RSDs) were 89.67-100.5%, and 3.59-7.12%, respectively.

Enhanced removal of As(â ¢) and As(â ¤) from aqueous solution using ionic liquid-modified magnetic graphene oxide.

In this study, ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6])-modified magnetic graphene oxide (MGO-IL) was prepared for the first time, and was used to adsorb and remove arsenic (As(Ⅲ) and As(V)) ions from aqueous solution. MGO-IL was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and magnetization curves. Effects of ionic liquid type, solution pH, initial arsenic concentration and contact time on the adsorption performance of MGO-IL for As(Ⅲ) and As(V) were studied. The experimental results showed that the adsorption equilibrium was achieved within 30 min, with maximum adsorption capacities of 160.65 mg g-1 for As(Ⅲ) and 104.13 mg g-1 for As(V), respectively, and MGO-IL could be rapidly isolated from solution by applying a magnetic field. MGO-IL was reused for 5 times, without marked decrease in its adsorption capacities. Moreover, common coexisting anions did not interfere with the absorption of As(Ⅲ) and As(V). Compared with MGO, the sorption quantities of MGO-IL for As(Ⅲ) and As(V) were greatly enhanced, and the equilibrium time was significantly reduced. Therefore, MGO-IL can potentially serve as an excellent adsorbent for the simultaneous separation and removal of As(Ⅲ) and As(V) from water.

C8-modified magnetic graphene oxide based solid-phase extraction coupled with dispersive liquid-liquid microextraction for detection of trace phthalate acid esters in water samples.

Phthalate acid esters (PAEs) are extensively applied in plastic and plastic products, and have caused potential hazards on human and animal health. In this study, a highly sensitive method was proposed for trace detection of selected PAEs in water by gas chromatography-mass spectrometry, after solid-phase extraction (SPE) using octyl (C8)-modified magnetic graphene oxide (MGO-C8) as the adsorbent followed by dispersive liquid-liquid microextraction (DLLME). The prepared MGO-C8 was characterized by Fourier transform infrared spectroscopy (FT-IR), thermo gravimetric analysis (TGA) and vibrating sample magnetometry (VSM). The recoveries of the PAEs using MGO-C8 as the adsorbent were found to be significantly higher those obtained by MGO. The influences of solution pH, adsorption and desorption time, eluent and extractant, and salt addition on the extraction efficiency of PAEs were investigated. Under the optimized conditions, limits of detection (LODs) of 0.5-1.0 ng L-1 for PAEs, and related standard deviations (RSDs) of 4.8-7.5% were obtained. The proposed method was utilized in the detection of trace PAEs in real environmental water samples, with spiked recoveries of 89.5-112.3%, 91.5-105.0% and 98.0-110.0% for DBP, DEHP and DNOP, respectively.

Synthesis of a molecularly imprinted polymer on mSiO2 @Fe3 O4 for the selective adsorption of atrazine.

Atrazine contamination of water is of considerable concern because of the potential hazard to human health. In this study, a magnetic molecularly imprinted polymer for atrazine was prepared by the surface-imprinting technique using Fe3 O4 as the core, mesoporous silica as the carrier, atrazine as the template, and itaconic acid as the functional monomer. The magnetic molecularly imprinted polymer was characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and vibration-sample magnetometry. The binding properties of the magnetic molecularly imprinted polymer toward atrazine were investigated by adsorption isotherms, kinetics, and competitive adsorption. It was found that the adsorption equilibrium was achieved within 2 h, the maximum adsorption capacity of atrazine was 8.8 µmol/g, and the adsorption process could be well described by the Langmuir isotherm model and pseudo-second-order kinetic model. The magnetic molecularly imprinted polymer exhibited good adsorption selectivity for atrazine with respect to structural analogues, such as cyanazine, simetryne, and prometryn. The reusability of the magnetic molecularly imprinted polymer was demonstrated for at least five repeated cycles without a significant decrease in adsorption capacity. These results suggested that the magnetic molecularly imprinted polymer could be used as an efficient material for the selective adsorption and removal of atrazine from water samples.

A novel ion-imprinted polymer based on graphene oxide-mesoporous silica nanosheet for fast and efficient removal of chromium (VI) from aqueous solution.

A novel chromium (VI) ion-imprinted polymer (Cr(VI)-IIP) was prepared using surface ion imprinting technique on graphene oxide-mesoporous silica (GO-MS) nanosheets with 3-(2-amino ethyl amino) propyl trimethoxysilane as the functional monomer. The prepared Cr(VI)-IIP was characterized by Fourier transform infrared spectroscopy, scanning electronic microscopy, X-ray diffraction and thermogravimetric analysis. The prepared Cr(VI)-IIP was then applied to remove Cr(VI) ions from aqueous solution. The influences of functional monomer amount, contact time, initial Cr(VI) concentration, solution pH and temperature, on the adsorption performance of Cr(VI)-IIP were investigated. Adsorption experiments revealed that the sorption equilibrium was achieved within 5 min with a high adsorption capacity up to 438.1 mg g-1, and the adsorption process followed pseudo-second-order kinetic model and Freundlich adsorption isotherm model. The Cr(VI)-IIP exhibited superior selectivity for Cr(VI) with respected to Cr(III), Mo(VI), PO43-, SO42- and NO3-. Moreover, Cr(VI)-IIP showed good reusability in five adsorption/desorption cycles. Results indicated that the synthesized Cr(VI)-IIP possessed excellent potential applications for the treatment of wastewaters containing Cr(VI).

Preparation of magnetic molecularly imprinted polymer nanoparticles by surface imprinting by a sol-gel process for the selective and rapid removal of di-(2-ethylhexyl) phthalate from aqueous solution.

Magnetic molecularly imprinted polymer nanoparticles for di-(2-ethylhexyl) phthalate were synthesized by surface imprinting technology with a sol-gel process and used for the selective and rapid adsorption and removal of di-(2-ethylhexyl) phthalate from aqueous solution. The prepared magnetic molecularly imprinted polymer nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and vibrating sample magnetometry. The adsorption of di-(2-ethylhexyl) phthalate onto the magnetic molecularly imprinted polymer was spontaneous and endothermic. The adsorption equilibrium was achieved within 1 h, the maximum adsorption capacity was 30.7 mg/g, and the adsorption process could be well described by Langmuir isotherm model and pseudo-second-order kinetic model. The magnetic molecularly imprinted polymer displayed a good adsorption selectivity for di-(2-ethylhexyl) phthalate with respect to dibutyl phthalate and di-n-octyl phthalate. The reusability of magnetic molecularly imprinted polymer was demonstrated for at least eight repeated cycles without significant loss in adsorption capacity. The adsorption efficiencies of the magnetic molecularly imprinted polymer toward di-(2-ethylhexyl) phthalate in real water samples were in the range of 98-100%. These results indicated that the prepared adsorbent could be used as an efficient and cost-effective material for the removal of di-(2-ethylhexyl) phthalate from environmental water samples.

Determination of trace bisphenol A in environmental water by high-performance liquid chromatography using magnetic reduced graphene oxide based solid-phase extraction coupled with dispersive liquid-liquid microextraction.

Bisphenol A (BPA), an endocrine-disrupting chemical, has received much attention from researchers and the general public. In this paper, a novel method of determining BPA at trace levels was developed, using magnetic reduced graphene oxide (rGO-Fe3O4)-based solid-phase extraction coupled with dispersive liquid-liquid microextraction (DLLME), followed by high-performance liquid chromatographic determination. The rGO-Fe3O4 was prepared and then characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, and vibrating sample magnetometry. The greatest saturation magnetization of rGO-Fe3O4 was up to 43.8 emu g-1, which allowed rapid isolation of the rGO-Fe3O4 from solutions upon applying an appropriate magnetic field. The effects of solution pH, adsorbent amount, type and volume of eluent and extraction solvent, extraction time, and salt concentration on the extraction efficiency of BPA were examined and optimized. Under the optimum conditions, an enrichment factor of 5217 and an LOD of 0.01 µg L-1 for BPA were obtained. The reusability of rGO-Fe3O4 for at least 12 repeated cycles without any significant decrease in the extraction recovery of BPA was demonstrated. The proposed method was applied to the determination of BPA in different real water samples, with relative recoveries of 84.8-104.9 % and RSDs of 0.8-8.3 % in the spiked concentration range 1-10 µg L-1.

Magnetic molecularly imprinted polymer nanoparticles-based solid-phase extraction coupled with gas chromatography-mass spectrometry for selective determination of trace di-(2-ethylhexyl) phthalate in water samples.

Novel magnetic molecularly imprinted polymer nanoparticles (MMIPs) were synthesized by surface imprinting technology with a sol-gel process, using di(2-ethylhexyl)phthalate (DEHP) as the template. The MMIPs were characterized using Fourier transform-infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The MMIPs displayed good adsorption selectivity for DEHP, with selectivity coefficients of 5.2 and 4.8 with respect to di-n-octyl phthalate and dibutyl phthalate, respectively. The reusability of MMIPs was demonstrated for at least eight repeated cycles without significant loss in adsorption capacity. A novel method for selective preconcentration and determination of trace DEHP in aqueous solutions was developed by using the magnetic DEHP-imprinted nanoparticles as adsorbent for solid-phase extraction (SPE) coupled with gas chromatography-mass spectrometry (GC-MS). The optimum SPE conditions were as follows: adsorbent amount, 50 mg; sample volume, 100 mL; adsorption time, 20 min; eluent, chloroform; and desorption time, 5 min. Results showed that the limit of detection (LOD) and limit of quantification (LOQ) for DEHP were 0.02 and 0.075 µg L-1, respectively. The proposed method was applied to the determination of DEHP in different real water samples, with spiked recovery of 93.3-103.2 % and RSD of 1.2-3.2 %. Therefore, the developed analytical method is rapid, sensitive, and accurate, which provides a new option for the detection of trace DEHP in aqueous samples.

[Determination of metals in waste bag filter of steel works by microwave digestion-flame atomic absorption spectrometry].

A method of microwave digestion technique-flame atomic absorption spectrometry was proposed to determine the total contents of Cu, Zn, Pb, Cd, Cr and Ni in five different kinds of waste bag filters from a steel plant. The digestion effects of the six acid systems on the heavy metals digestion were studied for the first time. The relative standard deviation (RSD) of the method was between 1.02% and 9.35%, and the recovery rates obtained by standard addition method ranged from 87.7% to 105.6%. The results indicated that the proposed method exhibited the advantages of simplicity, speediness, accuracy and repeatability, and it was suitable for determining the metal elements of the waste bag filter. The results also showed that different digestion systems should be used according to different waste bag filters. The waste bag filter samples from different production processes had different metal elements content. The Pb and Zn were the highest in the waste bag filters, while the Cu, Ni, Cd and Cr were relatively lower. These determination results provided the scientific data for further treatment and disposal of the waste bag filter.

Hollow fiber supported liquid-phase microextraction using ionic liquid as extractant for preconcentration of benzene, toluene, ethylbenzene and xylenes from water sample with gas chromatography-hydrogen flame ionization detection.

A novel method has been developed for the analysis of benzene, toluene, ethyl-benzene, and o-, m- and p-xylenes (BTEXs) in water using hollow fiber supported liquid-phase microextraction (HF-LPME) followed by gas chromatography-hydrogen flame ionization detection. Ionic liquid 1-butyl-3-methy-limidazolium hexafluorophosphate ([BMIM][PF(6)]) was acted as the extractant for extraction and preconcentration of BTEXs from aqueous samples, and a porous-walled polypropylene hollow fiber was utilized to stabilize and protect [BMIM][PF(6)] during the extraction process. Various parameters that affect extraction efficiency were investigated in detail, and the optimized experimental conditions were as follows: 8 µL of [BMIM][PF(6)] as extraction solvent for the target analytes in 20 mL of sample solution, 30 min of extraction time, a stirring rate of 1400 rpm and 15% NaCl (w/v) in aqueous sample at 25°C (ambient temperature). The recovery was found to be 90.0-111.5% with RSD (n=5) of 1.3-5.4%, and the detection limits (S/N=3) were in the range of 2.7-4.0 µg/L. The proposed method was simple, cheap, rapid, sensitive and environmentally benign, and could act as an alternative to techniques for BTEXs analysis with expensive instrumentations.

Speciation analysis of mercury in water samples using dispersive liquid-liquid microextraction combined with high-performance liquid chromatography.

A novel approach for preconcentration and speciation analysis of trace amount of mercury from water samples was proposed by dispersive liquid-liquid microextraction (DLLME) coupled to high performance liquid chromatography with diode array detection (HPLC-DAD). Mercury species (Hg(2+), methylmercury (MeHg(+)) and phenylmercury (PhHg(+))) were complexed with dithizone (DZ) to form hydrophobic chelates and then extracted into the fine drops of extraction solvent dispersed in the aqueous sample by dispersive solvent. After extraction, the sedimented phase was analyzed by HPLC-DAD. Some important parameters affecting the DLLME such as extraction solvent and dispersive solvent type and volume, concentration of dithizone solution, sample pH, extraction time and salt effect were investigated. Ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM][PF(6)]) was found to be a suitable extractant for the chelates. Under the optimized conditions (extraction solvent: 70 µL of ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM][PF(6)]); dispersive solvent: 0.75 mL of methanol containing dithizone (0.02%, m/v); pH: 4; extraction time: 5 min; and without salt addition), the limits of detection for Hg(2+), MeHg(+) and PhHg(+) were 0.32, 0.96 and 1.91 µg L(-1) (SN(-1)=3) respectively, and the relative standard deviation (RSD) was between 4.1 and 7.3% (n=5). Three real water samples (tap water, river water and lake water) spiked with mercury species were detected by the developed method, and the relative recoveries obtained for Hg(2+), MeHg(+) and PhHg(+) were 89.6-101.3%, 85.6-102.0% and 81.3-97.6%, respectively.

Determination of trace impurities in high-purity zirconium dioxide by inductively coupled plasma atomic emission spectrometry using microwave-assisted digestion and wavelet transform-based correction procedure.

This paper describes a rapid, accurate and precise method for the determination of trace Fe, Hf, Mn, Na, Si and Ti in high-purity zirconium dioxide (ZrO2) powders by inductively coupled plasma atomic emission spectrometry (ICP-AES). The samples were dissolved by a microwave-assisted digestion system. Four different digestion programs with various reagents were tested. It was found that using a mixture of sulfuric acid (H2SO4) and ammonium sulfate ((NH4)2SO4), the total sample dissolution time was 30 min, much shorter than that required for conventional digestion in an opening system. The determination of almost all of the target analytes suffered from spectral interferences, since Zr shows a line-rich atomic emission spectrometry. The wavelet transform (WT), a recently developed mathematical technique was applied to the correction of spectral interference, and more accurate and precise results were obtained, compared with traditional off-peak background correction procedure. Experimental work revealed that a high Zr concentration would result in a significant decrease in peak height of the analyte lines, which was corrected by standard addition method. The performance of the developed method was evaluated by using synthetic samples. The recoveries were in the range of 87-112% and relative standard deviation was within 1.1-3.4%. The detection limits (3sigma) for Fe, Hf, Mn, Na, Si and Ti were found to be 1.2, 13.3, 1.0, 4.5, 5.8 and 2.0 microg g(-1), respectively. The results showed that with the microwave-assisted digestion and the WT correction, the detection limits have improved by a factor of about 5 for Fe, 4 for Mn and Ti, 3 for Si, and 2 for Hf and Na, respectively, in comparison with conventional open-system digestion and off-peak correction. The proposed technique was applied to the analysis of trace elements above-mentioned in three types of ZrO2 powders.

[Application of a modified method of wavelet noise removing to noisy ICP-AES spectra].

A new method for noise removal from signal by the wavelet transform was developed. Compared with analytical signal, noise has higher frequency and smaller amplitude. By the new wavelet filtering method, the high frequency components were first removed, and then the small ones in the remaining transformed vectors were discarded. The proposed approach was evaluated by the processing of simulated and experimental noisy ICP-AES spectra. Different amounts of noise were added to a Gaussian peak to obtain a series of noisy ICP spectra. The simulated noisy spectra with R (signal to noise ratio) = 6 and N (data number) = 51, and with R = 6 and N = 17 were used to illustrate the feasibility of the proposed method. The performances of noise removal by the wavelet smoothing, the wavelet denoising and the proposed technique were compared. It was found that using the new approach, the relative errors of peak height would be no more than 5% for spectra with normal sampling points and R > or = 2. Moreover, the baseline could be easily defined, which was helpful to the accurate measurement of peak height. Experimental spectra of Al and V at low concentrations were processed by the proposed method. Intense noises were efficiently removed and the spectra became smoother without underestimating the analytical signal. The distortion of V 303.310 nm line was substantially rectified. The linear correlation coefficients between the peak heights in the reconstructed spectra and the concentrations were found to be 0.9953 for Al and 0.9836 for V, respectively.