Use of solid-phase microextraction for the analysis of bisphenol A and bisphenol A diglycidyl ether in food simulants

A new method has been developed to simultaneously analyse bisphenol A (BPA) and bisphenol A diglycidyl ether (BADGE) in aqueous based food simulants. The method consists on direct immersion solid-phase microextraction (SPME) of the analytes from the liquid matrix and subsequent chromatographic analysis by gas chromatography-mass spectrometry. Using the proposed method, a whole analysis (including chromatographic step) can be completed in less than 40 min, with minimum sample handling. The SPME method shows good analytical performance for simultaneous BPA and BADGE analysis, except for BADGE determination in the aqueous alcohol (simulant C) solution. Detection limits ranging from 0.1 to 2.0 ng/g for BPA and from 13 to 15 ng/g from BADGE were obtained, with a linear range from the low-ng/g to several-microg/g range for BPA and from 0.1 microg/g to 40 microg/g for BADGE. A possible optimisation method has been also developed and introduced.     

Relaxation time for composite membranes

The formalism of network thermodynamics has been utilised to calculate the relaxation time for composite membranes, consisting of a prallel and a series arrangement of two constituent membrane elements, as a function of relaxation times for the constituent membrane elements.     

Use of block copolymer as compatibilizer in polyimide/zeolite composite membranes

In this work, we introduced a diblock copolymer (dBC), i.e., polystyrene‐b‐poly(hydroxyl ethyl acrylate) (PS‐b‐PHEA) as a compatibilizer to enhance interfacial adhesion between PI and zeolite in PI/Zeolite/dBC (1/0.1/0.05 wt%) membrane for gas separation. FT‐IR spectroscopy showed the formation of hydrogen bonding interactions of the carbonyl and the hydroxyl in dBC with both PI and zeolite. The differential scanning calorimeter (DSC) study showed that the glass transition temperature (T_g) of PI increased upon the introduction of dBC, indicating specific interactions in the mixed matrix membranes. The gas permeabilities of H₂, N₂, O₂, and CO₂ through PI/zeolite 5A/dBC membranes were reduced but the permselectivity were increased compared to neat PI membrane. Copyright © 2009 John Wiley & Sons, Ltd.     

Inorganic composite membranes for electrodialytic desaltination

Application of inorganic composite membranes in electrodialytic desaltination of dilute solutions containing Na⁺, Ca²⁺, Mg²⁺, Cl^?, and SO ₄ ^2? ions was studied. The membranes are based on an oxide ceramic containing hydrated zirconium(IV) oxide as an ion-exchange component. The limiting currents were estimated theoretically.     

A new direct current method for resistance measurements of ionic membranes and its application to composite membranes

The present paper deals with a D.C. method for measuring membrane electrical resistance making use of a constant current pulse, automated measuring equipment and taking into account polarization phenomena. The potential transient, subsequent to application of current, is analyzed, and membrane electrical resistance is determined by extrapolation to zero time of the potential differences measured after the current step. Experimental results obtained with commercial ion-exchange membranes were in good agreement with those computed from the diffusion equation. The method developed gives values with a standard deviation lower than traditional techniques. As an application example, the current pulse technique allows measurement of electrical resistance of composite silicafouled membranes in the electrodialysis process in both current directions. In this case the different response of the system, after the current pulse, gives useful information about membrane structure and ion distribution on the double layers surrounding the membrane.     

Multiple-stage mass spectrometry analysis of bisphenol A diglycidyl ether, bisphenol F diglycidyl ether and their derivatives

The fragmentation of bisphenol A diglycidyl ether (BADGE), bisphenol F diglycidyl ether (BFDGE) and their derivatives was studied by electrospray ionization tandem mass spectrometry. Multiple-stage mass spectrometry and accurate mass measurements were combined to establish the fragmentation pathways. BADGEs and BFDGEs tend to form ammonium adducts under electrospray conditions which fragmented easily. The fragmentation of [M+NH(4)](+) for BADGEs started with the cleavage of the phenyl-alkyl bond, which was followed by the α-cleavage of the ether group to generate the characteristic product ions at m/z 135, [C(9)H(11)O](+), and m/z 107, [C(7)H(7)O](+). The fragmentation of the BFDGE isomer mixtures was studied by on-line reversed-phase liquid chromatography coupled to multiple-stage mass spectrometry (LC/MS(n)). Information obtained from product ion spectra for each BFDGE isomer and its comparison with the fragmentation pathway of BADGE allowed each isomer and the chromatographic elution order to be identified.     

Application of multivariate analysis to the screening of molecularly imprinted polymers for bisphenol A

A key issue in the synthesis of molecularly imprinted polymers (MIPs) is the identification and optimisation of the main factors that affect the material structure and its molecular recognition properties. This paper describes the application of an experimental design and multivariate analysis method for the synthesis of bisphenol A (BPA)-selective MIPs. Six factors with a large impact on the MIP synthesis and its analytical performance have been optimised: the amount of template, the type and the percentage of functional and cross-linking monomers, the polymerisation method (i.e. thermal or UV initiation) and the porogenic solvent. The polymers have been prepared in small-scale (mini-MIPs) and, after careful removal of the template, their BPA rebinding capacity has been evaluated and related to the MIP composition. Among the two functional monomers tested, namely 4-vinylpyridine (4-vpy) and methacrylic acid (MAA), the former rendered the best selectivity for BPA analysis. The partial least squares (PLS) models revealed that the photoinitiated polymers with a 1:1 ratio of 4-vinylpyridine to cross-linker (EDMA or TRIM) yield the highest specific binding. Such procedure is time and cost effective and can be used as a general tool in the preparation of MIPs for different analytes.     

Interfacial synthesis of bisphenol A tetrachlorocyclotriphosphazene from bisphenol A and hexachlorocyclotriphosphazene

The effect of solvent purity on the synthesis and yield of bisphenol A tetrachlorocyclotriphosphazene (BATCCP) has not been described in the literature. The purpose of this research was to synthesize BATCCP hybrid monomers and to evaluate the effect of solvent purity on the BATCCP production. BATCCP monomers were prepared by an interfacial procedure in a water/toluene system as a function of time with the assistance of a phase transfer catalyst, tetraoctylammonium bromide. ¹H and ³¹P NMR confirmed the production of BATCCP monomer by the appearance of chemical shifts at 7.18 and 5.35 ppm in the ¹H NMR and 23.4 and 13.9 ppm in the ³¹P NMR, respectively. Distillation of the toluene, not suggested in previous reports of HCCP hybrid synthesis, resulted in an improvement of actual % yield to 40% and stability of the product throughout the 1440 min reaction as confirmed by MALDI, compared with an 11% actual yield at 15 min, decaying to 2% over a 1440 min reaction when the synthesis was performed with ‘anhydrous toluene’ as provided commercially without further distillation.     

纳米银增强化学发光法测定塑料中的双酚A

研究发现在碱性介质中,纳米银对luminol-KMnO4化学发光体系的发光信号具有强烈的增敏作用,而双酚A对该体系具有明显的抑制作用,据此结合流动注射技术,建立了流动注射化学发光分析法测定塑料中双酚A的方法。该方法测定双酚A的线性范围为8.0×10-11～1.0×10-8g.mL-1(0.9926)和1.0×10-8～8.0×10-8g.mL-1(0.9916),检出限(3σ)为6.5×10-11g.mL-1。对5.0×10-10g.mL-1和5.0×10-8g.mL-1双酚A平行测定11次,其相对标准偏差为1.4%和1.0%。对反应机理进行了讨论。该方法简单、快速、灵敏度高,用于塑料制品中双酚A的测定,回收率为97.0%～105.0%。     

Chirality based sensor for bisphenol A detection

A universal chirality detection platform based on immuno-recognition-driven nanoparticle assembly has been fabricated for the first time. A strong shifted chiral signal was produced by asymmetric plasmonic nanoparticle dimers. Using bisphenol A (BPA) as a model target substrate, the LOD was 0.02 ng mL(-1).     

基于碳量子点修饰硅胶荧光法测定塑料制品中的双酚A

制备了碳量子点修饰的硅胶SiO2@CDs.在盐酸介质中KBrO3能够氧化碳量子点使其荧光发射峰减弱,而双酚A(BPA)对此氧化猝灭有明显抑制作用,据此建立了荧光法测定痕量双酚A的新方法,线性范围是20~500μg·L-1,检出限3σ为5.2μg·L-1.本文作者将该方法成功用于塑料制品中双酚A的测定,回收率在95%~104%之间.     

Biosensor immunoassays for the detection of bisphenol A

Bisphenol A (BPA) is a xenoestrogen found in the environment, in consequence, for the biosensor detection of BPA we raised antibodies (polyclonal (PAbs) and monoclonal (MAbs)) against a structural analogue of BPA, 4,4 bis-(4-hydroxyphenyl) valeric acid (BVA). The kinetics of the MAb-BPA interaction were evaluated and the MAb providing the highest affinity was directly immobilized onto the sensor chip surface to evaluate a direct assay. Afterwards, the performance of the MAbs and the PAbs was compared in an inhibition assay using a BVA-coated chip.The highest sensitivity (limit of detection (LOD) of 0.4 μg L⁻¹) was obtained with MAb 12 in the direct assay. However, the inhibition assay was the most robust and the PAbs showed the highest sensitivity (LOD of 0.5-1 μg L⁻¹). The antibodies were specific for BVA and BPA as only minor cross-reactivities were found toward structurally related compounds or other endocrine disruptors. In the inhibition assay (with a run time of 6 min), water samples spiked with BPA at different levels (0.5-50 μg L⁻¹) resulted in recoveries varying between 68% and 121%. The sensitivity of the inhibition assay could be improved 40 times (LOD of 0.03 μg L⁻¹ with the Mab 12-based assay) using solid phase extraction (SPE).     

Carbon ceramic composite membranes for catalytic membrane reactor applications

A novel route is described for the production of carbon-ceramic membranes where the structure can be adjusted for use in either multiphase (gas-liquid) or gas phase membrane reactors. The production route allows the deposition of the membrane layer onto a two layer ceramic support (1OO nm top layer) giving potentially significant cost savings. It has also been shown that the route can be readily extended to multichannel monolith supports allowing a simple scale up route. The carbon component also provides an excellent support for the active metal allowing the production of high metal dispersions. Published in Russian in Kinetika i Kataliz, 2007, Vol. 48, No. 6, pp. 924–938. This article was submitted by the authors in English.     

Cellular porous polyvinylidene fluoride composite membranes for lithium-ion batteries

Macroporous polyvinylidene fluoride (PVdF) membranes were prepared by a phase inversion method and evaluated as battery separators. Two totally different morphologies (cellular and finger-like) were obtained by coagulating PVdF solutions with two different solvents. The cellular membranes were formed immediately by precipitating the PVdF solution with a latent solvent (acetone) in water, while the finger-like membranes were precipitated from the PVdF solution with a true solvent (N-methyl-2-pyrrolidone). The incorporation of a silica filler decreased the ionic resistance of the PVdF membranes of both morphologies. However, the cellular membranes showed better mechanical properties and enabled higher ionic conductivities than the finger-like ones, especially when the silica loading was low. Compared with a conventional untreated polyolefin separator, the porous PVdF membranes showed good wettability by a liquid electrolyte. After being activated with a commercial LiPF₆–ethylene carbonate–dimethyl carbonate electrolyte, the PVdF membranes were tested for their applications in lithium-ion batteries. Coin cells with these PVdF membranes exhibited stable cycling performance and good rate capability at room temperature. However, the cellular membranes are preferred over the finger-like ones because they offer higher mechanical performance, and can be processed into flat membranes more easily.     

Emulsion pathways to composite polymeric membranes for separation processes

A novel method for the preparation of selective composite membranes from emulsions is suggested. The dispersed phase is chosen to yield a polymer soluble in those components for which the membrane should be selective; the continuous phase, on the other hand, is selected to yield a polymer that is insoluble in any of the components of the mixture. Conventional emulsions (which have a maximum dispersed phase volume fraction of 0.74) or microemulsions can be employed to generate composites. However, concentrated emulsions which allow volume fractions as large as 0.99 are most suitable as precursors to selective and efficient membranes. These concentrated emulsions have the appearance of gels with a structure similar to that of foams. The relatively high permeabilities obtained with the resultant membranes are due to the small thickness of the films of the continuous phase. A concentrated emulsion of a hydrophobic (hydrophilic) monomer dispersed in a hydrophilic (hydrophobic) continuous phase is first prepared at room temperature, with suitable initiators in each phase for later polymerization, and with an appropriate dispersant in the continuous phase. To ensure the stability of the emulsion, the hydrophilic monomer is, in general, replaced by monomer plus water. On heating the gel at 50 °C, polymerization occurs in both phases and the emulsion transforms into a composite polymer membrane. As examples, composite membranes containing polystyrene as the dispersed phase and polyacrylamide as the continuous phase are used to separate toluene from cyclohexane, while other composite membranes containing acrylamide as the dispersed phase and a crosslinked polystyrene as the continuous phase are used to separate water from ethanol.Lecture presented at the Colburn Symposium, University of Delaware, October 19, 1988.     

FTIR spectroscopic investigation of inorganic fillers for composite DMFC membranes

An infrared spectroscopic investigation of inorganic fillers employed in composite perfluorosulfonic membranes has been carried out. The surface acidity of the fillers appears to influence the bending and stretching vibrational frequencies of the water physically adsorbed on the filler surface. The conductivity of composite membranes and maximum power density of direct methanol fuel cells (DMFCs) at 145 °C appear to be related to the characteristics of the water adsorbed on the filler particles. Inorganic fillers characterised by acidic properties undergo a strong interaction with water and enhance the DMFC performance at high temperature.     

Single-step fabrication of asymmetric dual-phase composite membranes for oxygen separation

Asymmetric dual-phase composite membranes for oxygen separation were conveniently fabricated by an acid leaching technique. A thin dense layer of Ce_0.85Sm_0.15O_1.925/Sm_0.6Sr_0.4FeO_3−δ was left by controlling the degree of acid leaching, and a porous substrate of Ce_0.85Sm_0.15O_1.925 with a fluorite structure was formed after dissolution of Sm_0.6Sr_0.4FeO_3−δ with a perovskite structure in HCl. Thus, a thin dense layer and a porous substrate can be fabricated in a single step in which traditional shrinkage mismatch and chemical reaction between thin dense layers and porous substrates can be avoided. The thickness of the dense layer can be controlled by varying the acid leaching time. Hence, dual-phase composite membranes with high oxygen flux can be obtained.